CN108419322B - Electromagnetic heating equipment, electromagnetic heating system and heating control method and device thereof - Google Patents

Abstract

The invention discloses an electromagnetic heating device, an electromagnetic heating system, a heating control method and a heating control device thereof, wherein the method comprises the following steps: acquiring target heating power of an electromagnetic heating system; judging whether the target heating power is smaller than a preset power or not; if the target heating power is smaller than the preset power, controlling the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control period, wherein N first pulse signals are provided to the power switch tube in the discharging stage so that the current flowing through the power switch tube is smaller than a preset current value, P first pulse signals are provided in first preset time in the heating stage, Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of each first pulse signal is first driving voltage, the amplitude of each second pulse signal is second driving voltage, and the first driving voltage is smaller than the second driving voltage. Therefore, pulse current is restrained in a pre-discharge mode, and millisecond-pole duty ratio low-power heating is achieved.

Description

Electromagnetic heating equipment, electromagnetic heating system and heating control method and device thereof

Technical Field

The invention relates to the technical field of household appliances, in particular to a heating control method of an electromagnetic heating system, a heating control device of the electromagnetic heating system, the electromagnetic heating system and electromagnetic heating equipment.

Background

In the related art, an electromagnetic resonance circuit of a single IGBT generally adopts a parallel resonance mode, and sets resonance parameters on the premise of realizing high-power operation, as shown in fig. 1, when heating is performed with high power, the leading voltage when the IGBT is turned on is very small due to matching of the resonance parameters, and the pulse current of the IGBT is also very small. However, as shown in fig. 2, when low-power heating is used, the leading voltage of the IGBT is very high, which causes the IGBT pulse current to be very large, and particularly, the IGBT is easily damaged beyond the limit of use of the IGBT.

In order to achieve low power, the related art usually adopts a duty ratio manner as shown in fig. 3 to perform intermittent heating, for example, a manner of stopping heating for 5s by heating for 5s to achieve low power of 5/10, but the related art has a problem that if the intermittent heating period is longer, the cooking function is affected, for example, the cooking function is easy to overflow when cooking porridge, the cooking experience of a user is reduced, and if the intermittent heating period is shorter, the IGBT is turned on hard, and thus the pulse current of the IGBT is very large and the noise is serious.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, a first object of the present invention is to provide a heating control method for an electromagnetic heating system, which can suppress a pulse current of a power switching tube and realize low-power heating with a millisecond duty ratio.

A second object of the present invention is to provide a heating control device for an electromagnetic heating system, and a third object of the present invention is to provide an electromagnetic heating system. A fourth object of the present invention is to provide an electromagnetic heating apparatus.

In order to achieve the above object, a first embodiment of the present invention provides a heating control method for an electromagnetic heating system, including the following steps: acquiring target heating power of the electromagnetic heating system; judging whether the target heating power is smaller than a preset power or not; if the target heating power is less than the preset power, controlling the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control period, wherein N first pulse signals are provided to a power switch tube of a resonance circuit of the electromagnetic heating system in the discharging stage so that the current flowing through the power switch tube is less than a preset current value, P first pulse signals are provided within a first preset time in the heating stage, and then Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of the first pulse signals is a first driving voltage, the amplitude of the second pulse signals is a second driving voltage, the first driving voltage is less than the second driving voltage, and N, P, Q is an integer greater than 1.

According to the heating control method of the electromagnetic heating system provided by the embodiment of the invention, when the target heating power is less than the preset power, in each control period, the resonant circuit of the electromagnetic heating system is controlled to sequentially enter a discharging stage, a heating stage and a stopping stage, wherein N first pulse signals are provided to the power switch tube of the resonant circuit in the discharging stage so that the current flowing through the power switch tube is less than a preset current value, P first pulse signals are provided within a first preset time in the heating stage, Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of each first pulse signal is a first driving voltage, the amplitude of each second pulse signal is a second driving voltage, and the first driving voltage is less than the second driving voltage. Therefore, by means of the pre-discharge mode, pulse current of the power switch tube can be restrained, low-power heating of millisecond-pole duty ratio is achieved, and user experience is improved.

In addition, the heating control method of the electromagnetic heating system according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the invention, a third driving voltage is continuously output to the power switch tube in the stop stage to drive the power switch tube to turn off.

According to an embodiment of the present invention, a pulse width of the first pulse signal of the discharging phase is smaller than a pulse width of the second pulse signal of the heating phase. The pulse width of each first pulse signal is greater than or equal to 0.1us and less than or equal to 10 us.

According to an embodiment of the invention, the first preset time is less than or equal to 5 ms.

According to an embodiment of the invention, the electromagnetic heating system is powered by an alternating current power supply, the method further comprising: acquiring a voltage zero crossing point of the alternating current power supply; and controlling the electromagnetic heating system to enter the discharging stage according to the voltage zero crossing point.

According to an embodiment of the present invention, the heating control method of the electromagnetic heating system further includes: after the preset time of entering the discharging stage or at the voltage zero crossing point, controlling the electromagnetic heating system to enter the heating stage so as to enable the discharging stage to be in a voltage zero crossing interval which is constructed by taking the voltage zero crossing point as the center. Wherein the voltage zero crossing interval may be [ -5ms, 5ms ].

According to an embodiment of the present invention, the preset current value is 85A.

According to an embodiment of the present invention, the first driving voltage is equal to or greater than 5V and equal to or less than 14.5V, and the second driving voltage is equal to or greater than 15V.

In order to achieve the above object, a second embodiment of the present invention provides a heating control device for an electromagnetic heating system, including: the resonant circuit comprises a power switch tube; the driving circuit is connected with the control end of the power switch tube and is used for driving the power switch tube; a control unit, connected to the driving circuit, for obtaining a target heating power of the electromagnetic heating system, determining whether the target heating power is smaller than a preset power, and controlling the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control cycle when the target heating power is smaller than the preset power, wherein the driving circuit is controlled to provide N first pulse signals to the power switch tube in the discharging stage so that a current flowing through the power switch tube is smaller than a preset current value, and the driving circuit is controlled to provide P first pulse signals within a first preset time and then provide Q second pulse signals to the power switch tube after the first preset time in the heating stage, an amplitude of the first pulse signals is a first driving voltage, the amplitude of the second pulse signal is a second driving voltage, and the first driving voltage is smaller than the second driving voltage, wherein N, P, Q is an integer greater than 1.

According to the heating control device of the electromagnetic heating system provided by the embodiment of the invention, when the target heating power is less than the preset power, in each control period, the control unit controls the resonant circuit of the electromagnetic heating system to sequentially enter the discharging stage, the heating stage and the stopping stage, wherein in the discharging stage, the driving circuit is controlled to provide N first pulse signals to the power switch tube so that the current flowing through the power switch tube is less than the preset current value, in the heating stage, the driving circuit is controlled to provide P first pulse signals within the first preset time and then provide Q second pulse signals to the power switch tube after the first preset time, the amplitude of the first pulse signals is the first driving voltage, the amplitude of the second pulse signals is the second driving voltage, and the first driving voltage is less than the second driving voltage. Therefore, by means of the pre-discharge mode, pulse current of the power switch tube can be restrained, low-power heating of millisecond-pole duty ratio is achieved, and user experience is improved.

In addition, the heating control device of the electromagnetic heating system according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, the control unit is further configured to continuously output a third driving voltage to the power switch tube in the stop phase, so as to drive the power switch tube to turn off.

According to an embodiment of the present invention, a pulse width of the first pulse signal of the discharging phase is smaller than a pulse width of the second pulse signal of the heating phase. The pulse width of the first pulse signal is greater than or equal to 0.1us and less than or equal to 10 us.

According to an embodiment of the invention, the first preset time is less than or equal to 5 ms.

According to one embodiment of the invention, the electromagnetic heating system is powered by an ac power source, the apparatus further comprising: the zero-crossing detection unit is connected with the control unit and used for acquiring a voltage zero-crossing point of the alternating current power supply, and the control unit is used for controlling the electromagnetic heating system to enter the discharging stage according to the voltage zero-crossing point.

According to an embodiment of the invention, the control unit is further configured to control the electromagnetic heating system to enter the heating phase after entering the discharging phase for a preset time or at the voltage zero-crossing point, so that the discharging phase is within a voltage zero-crossing interval configured with the voltage zero-crossing point as a center. Wherein the voltage zero-crossing interval is [ -5ms, 5ms ].

According to an embodiment of the present invention, the preset current value is 85A.

According to an embodiment of the present invention, the first driving voltage is equal to or greater than 5V and equal to or less than 14.5V, and the second driving voltage is equal to or greater than 15V.

In order to achieve the above object, a third embodiment of the present invention provides an electromagnetic heating system, including a heating control device of the electromagnetic heating system.

According to the electromagnetic heating system provided by the embodiment of the invention, the pulse current of the power switch tube can be inhibited in a pre-discharge mode, so that low-power heating of millisecond pole duty ratio is realized, and the user experience is improved.

In order to achieve the above object, a fourth aspect of the present invention provides an electromagnetic heating apparatus, including the electromagnetic heating system.

According to the electromagnetic heating equipment provided by the embodiment of the invention, the pulse current of the power switch tube can be inhibited in a pre-discharge mode, so that low-power heating of millisecond pole duty ratio is realized, and the user experience is improved.

According to one embodiment of the invention, the electromagnetic heating device is an induction cooker, an electromagnetic rice cooker or an electromagnetic pressure cooker.

Drawings

Fig. 1 is a schematic view of a driving waveform of an IGBT when an electromagnetic heating system heats at a high power in the related art;

fig. 2 is a schematic view of a driving waveform of an IGBT when an electromagnetic heating system heats at low power in the related art;

FIG. 3 is a waveform of a duty cycle when an electromagnetic heating system of the related art heats in a duty cycle manner;

fig. 4 is a flowchart of a heating control method of an electromagnetic heating system according to an embodiment of the present invention;

fig. 5 is a graph illustrating the relationship between the driving voltage and the current of an IGBT according to an embodiment of the invention;

fig. 6 is a schematic view of a heating control method of an electromagnetic heating system according to an embodiment of the present invention;

FIG. 7 is an expanded view of the driving waveforms of the discharging phase D1, the heating phase D2 and the stopping phase D3 of FIG. 6;

fig. 8 is a control schematic diagram of a first pulse signal and a second pulse signal in a heating control method of an electromagnetic heating system according to an embodiment of the present invention;

FIG. 9 is a block schematic diagram of a heating control device of an electromagnetic heating system according to an embodiment of the present invention;

FIG. 10 is a block schematic diagram of a heating control device of an electromagnetic heating system according to one embodiment of the present invention;

FIG. 11 is a schematic circuit diagram of an electromagnetic heating system according to one embodiment of the present invention; and

fig. 12 is a block schematic diagram of an electromagnetic heating system according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

A heating control method of an electromagnetic heating system, a heating control device of an electromagnetic heating system, and an electromagnetic heating apparatus proposed according to an embodiment of the present invention are described below with reference to the drawings.

Fig. 4 is a flowchart of a heating control method of an electromagnetic heating system according to an embodiment of the present invention. As shown in fig. 4, the heating control method includes the steps of:

s1: a target heating power W1 of the electromagnetic heating system is obtained.

Wherein the target heating power W1 is the heating power required by the electromagnetic heating system under different cooking parameters. For example, when a user wants to cook millet congee, a congee cooking mode can be selected on a control panel of the electromagnetic heating system, the electromagnetic heating system enters the congee cooking mode, and the electromagnetic heating system can perform low-power heating at a heating power of 800W in the congee cooking mode, wherein the corresponding target heating power is 800W.

S2: it is determined whether the target heating power W1 is less than the preset power W2.

The preset power W2 may be a power value calibrated according to an actual situation, and when the target heating power W1 is smaller than the preset power W2, it is determined that the electromagnetic heating system is heated at a low power, and when the target heating power W1 is greater than the preset power W2, it is determined that the electromagnetic heating system is heated at a high power.

According to an embodiment of the invention, the predetermined power W2 may be 1400W, thereby reducing noise caused by frequent activation.

S3: if the target heating power W1 is less than the preset power W2, the electromagnetic heating system is controlled to sequentially enter a discharging stage, a heating stage and a stopping stage in each control period, wherein N first pulse signals are provided to a power switch tube of a resonance circuit of the electromagnetic heating system in the discharging stage so that the current flowing through the power switch tube is less than a preset current value, P first pulse signals are provided in a first preset time in the heating stage, and Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of the first pulse signals is a first driving voltage V1, the amplitude of the second pulse signals is a second driving voltage V2, the first driving voltage V1 is less than the second driving voltage V2, and N, P, Q is an integer greater than 1.

It should be noted that the values of N, P and Q may be related to the actual control process, such as the pulse width, the pulse width variation of two adjacent pulses, the resonant heating parameter, etc., and the values of N, P and Q may be different in different control processes, so that N, P and Q may not be preset fixed values.

Further, according to an embodiment of the present invention, the third driving voltage is continuously output to the power switch tube during the stop phase to drive the power switch tube to turn off. Wherein, the third driving voltage may be 0V.

According to an embodiment of the present invention, the preset current value may be 85A. The first preset time may be less than or equal to 5 ms.

When the power switching tube, such as an IGBT tube, is driven by the first driving voltage, the power switching tube can be operated in an amplification state; when the second driving voltage is adopted to drive the power switch tube, such as an IGBT tube, the power switch tube can be enabled to work in a saturation conducting state. However, when the power switching tube is operated in the amplification state, as can be seen from the relationship between the drive voltage and the current of the IGBT shown in fig. 5, the current of the IGBT tube can be limited by adjusting the drive voltage supplied to the IGBT tube, and thus, the IGBT tube is driven by sampling the first drive voltage, and the current of the IGBT tube can be limited to 85A or less, thereby effectively suppressing the pulse current.

According to an embodiment of the invention, the first driving voltage V1 may be greater than or equal to 5V and less than or equal to 14.5V, and the second driving voltage V2 may be greater than or equal to 15V. More specifically, the power switch tube may be an IGBT, the first driving voltage V1 may preferably be 9V, when the first driving voltage supplied to the IGBT is 9V, the C-pole current of the IGBT may be constant around 22A, and the IGBT operates in an amplification state, so that the pulse current is well suppressed. The second driving voltage V2 may preferably be 15V, and the IGBT operates in a saturation state under the driving of the second driving voltage V2. The third driving voltage V3 may be 0V, and the IGBT is turned off by the driving of the third driving voltage V3.

Specifically, when the target heating power W1 is less than the preset power W2, as shown in fig. 6-7, each control cycle includes a discharging phase D1, a heating phase D2 and a stopping phase D3, i.e., in each control cycle, the resonant circuit (e.g., C2 and L2 connected in parallel in fig. 11) is controlled to sequentially enter a discharging phase D1, a heating phase D2 and a stopping phase D3. More specifically, the discharging phase D1 may be entered first, and the driving circuit of the electromagnetic heating system is controlled to output N first pulse signals to the control terminal of the power switch, so as to discharge the electric energy stored in the filter capacitor (i.e., C1 in fig. 11) during the stop phase in the previous control period, so that the collector voltage of the power switch is substantially 0V when the heating phase D2 is entered, and the pulse current of the power switch is reduced. After the discharging stage D1 is completed, the heating stage D2 is entered, and in the heating stage D2, the driving circuit is controlled to continue outputting the first pulse signal of the first preset time to the control end of the power switch tube to reduce the pulse current of the power switch tube, and then after the first preset time, the Q second pulse signals are output to the control end of the power switch tube to make the power switch tube work in a saturated conducting state, at this time, the electromagnetic heating system can perform normal resonant heating. And, after the heating stage D2 is completed, the electromagnetic heating system enters the stop stage D3, and in the stop stage D3, the control driving circuit outputs the third driving voltage, that is, 0V, does not output the pulse signal, and the power switch tube is turned off, at this time, the electromagnetic heating system stops heating.

In addition, the electromagnetic heating system can be controlled to perform low-power heating in a duty ratio mode, namely in each control period, the electromagnetic heating system can be controlled to heat for t1 first and then stop heating for t2, and the duty ratio is t1/(t1+ t 2). Specifically, as shown in fig. 6, in an embodiment of the present invention, the control period may be shortened to millisecond pole, for example, a duty ratio is set in units of a half-wave period of the ac mains, so that the electromagnetic heating system is controlled to perform low-power heating by adopting a millisecond pole duty ratio, where the duty ratio may refer to a ratio of the number of half-waves occupied by the heating stage to the number of half-waves occupied by the whole control period, for example, when the control period is 4 half-waves, if 1 half-wave is heated and 3 half-waves are stopped being heated, the duty ratio is 1/4, that is, the duration of the heating stage D2 in each control period is about one half-wave period; for another example, when the control period is 4 half waves, if 2 half waves are heated and the heating is stopped for 2 half waves, the duty ratio is 2/4, that is, the duration of the heating phase D2 in each control period is about two half-wave periods; as another example, when the control period is 4 half waves, if 3 half waves are heated and 1 half wave is stopped, the duty ratio is 3/4, i.e., the duration of the heating period D2 in each control period is about three half wave periods.

Therefore, the electric energy stored in the filter capacitor is released in a pre-discharging mode, namely in a discharging stage, the pulse current of the power switch tube can be restrained, and further the control period can be shortened to a millisecond pole, so that the heating effect is basically equal to continuous low power.

According to an embodiment of the invention, the electromagnetic heating system is powered by an ac power source, such as ac mains, the method further comprising: acquiring a voltage zero crossing point of an alternating current power supply; and controlling the electromagnetic heating system to enter a discharging stage according to the voltage zero crossing point.

It should be noted that the discharge phase may be entered near the voltage zero crossing point, that is, before, after or at the voltage zero crossing point.

Further, the heating control method of the electromagnetic heating system further includes: after the preset time of the discharging stage is reached or the voltage zero crossing point is used for controlling the electromagnetic heating system to enter the heating stage, so that the discharging stage is in a voltage zero crossing interval which is constructed by taking the voltage zero crossing point as the center.

That is, whether the discharging phase is completed or not can be determined by taking time as a reference, that is, if the duration of the discharging phase reaches a preset time, the resonant circuit is controlled to exit the discharging phase and enter the heating phase. Or, whether the discharging stage is completed or not can be judged by the voltage zero crossing point, that is, if the voltage zero crossing point is detected, the resonant circuit is controlled to exit the discharging stage and enter the heating stage.

Wherein, the voltage zero-crossing interval is [ -5ms, 5ms ]. That is, the discharge phase may be within 5ms before and after the voltage zero crossing.

In addition, in one embodiment of the present invention, the heating control method of the electromagnetic heating system further includes: the electromagnetic heating system can also be controlled to enter a stopping phase according to the voltage zero crossing point.

In particular, in connection with the embodiment of fig. 6, assuming low power heating with a duty cycle of 2/4 is selected according to the target heating power, the total control period is 4 half-waves, the heating period being close to 2 half-waves. The heating control method of the electromagnetic heating system comprises the following steps:

the discharging phase D1 may be entered before the first zero-crossing point a1, for example, the first zero-crossing point a1 may be estimated, then the starting time of the discharging phase D1 is obtained according to the estimated first zero-crossing point a1 and the preset time tf for the discharging phase D1 to last, and the electromagnetic heating system is controlled to enter the discharging phase D1 at the starting time, that is, the driving circuit is controlled to output the first pulse signal with the amplitude of the first driving voltage V1 to the power switch tube, so as to release the electric energy stored in the filter capacitor during the stopping phase.

In the process of controlling the driving circuit to output the first pulse signal, detecting the voltage zero crossing point in real time, and when the voltage zero crossing point, namely the first zero crossing point a1, controlling the electromagnetic heating system to enter a heating stage D2, namely controlling the driving circuit to output the first pulse signal with the amplitude of the first driving voltage V1 to the control end of the power switch tube, and output the second pulse signal with the amplitude of the second driving voltage V2 to the control end of the power switch tube after the first preset time T1, so that the power switch tube works in a saturated conducting state, and at this time, the electromagnetic heating system can perform normal resonant heating.

The duration of the heating stage D2 is close to two half-wave periods, the zero crossing point of the voltage is continuously detected in real time in the process of controlling the driving circuit to output the second pulse signal, and when the third zero crossing point A3 is detected, the electromagnetic heating system is controlled to enter the stop stage D3, that is, the driving circuit is controlled to continuously output the third driving voltage, that is, 0V, to the control end of the power switch tube to drive the power switch tube to be turned off, and the electromagnetic heating system stops heating.

The duration of the stop phase D3 is close to two half-wave periods, and in the stop phase D3, the fifth zero-crossing point a5 may be estimated, and then the starting time of the discharging phase D1 in the next control cycle may be obtained according to the estimated fifth zero-crossing point a5 and the preset time for which the discharging phase D1 is to be continued.

So repeating, low power heating at millisecond duty cycles can be achieved such that the heating effect is substantially equivalent to continuous low power.

According to one embodiment of the present invention, a pulse width of the first pulse signal in the discharging phase is smaller than a pulse width of the second pulse signal in the heating phase. That is, the pulse width of any one of the first pulse signals in the discharging stage is smaller than the pulse width of each of the second pulse signals. In other words, the pulse widths of the N first pulse signals provided in the discharging stage are all smaller than the minimum pulse width of the pulse widths of the Q second pulse signals provided in the heating stage. Wherein, the pulse width may refer to the duration of the high level. In addition, the pulse width of the first pulse signal in the discharging stage may also be smaller than the pulse width of the first pulse signal in the heating stage.

When the first pulse signal with a narrow pulse width is used for driving the power switch tube, for example, the IGBT tube, the pulse current of the IGBT tube needs a certain time to rise, so that the narrow pulse width can turn off the IGBT tube before the pulse current of the IGBT tube rises to a large value, and the current of the IGBT tube can be limited to, for example, 85A or less, thereby effectively suppressing the pulse current.

According to an embodiment of the present invention, as shown in fig. 7, the pulse widths of the N first pulse signals of the discharging stage may be gradually increased. And the difference value of the pulse widths of two adjacent first pulse signals can be less than or equal to a preset width threshold value.

It should be understood that the gradual increase of the pulse widths of the N first pulse signals may refer to that the overall trend of the pulse widths of the N first pulse signals is increasing, and the increasing manner may be various, including but not limited to, sequentially increasing according to the same preset increment, or sequentially increasing according to different preset increments, or the consecutive N pulse widths may be kept unchanged during the increasing process.

Specifically, as shown in fig. 7, it is assumed that the driving circuit outputs N first pulse signals to the power switch tube during the discharging phase D1 to release the stored electric energy of the filter capacitor during the previous stopping phase D3, wherein the pulse widths of the N first pulse signals may be Y1, Y2, …, YN-2, YN-1, YN, respectively. The N first pulse signals show an increasing trend as a whole, for example, the following relationship may be satisfied between the pulse widths of the N first pulse signals: yi +1 is not less than Yi + N, where i is 1 to N-1, Yi is the pulse width of the ith first pulse signal, Yi +1 is the pulse width of the i +1 th first pulse signal, and N is a preset width threshold, that is, the pulse width variation of each two adjacent first pulse signals may be equal, that is, gradually increased according to the same preset increment; or the difference of the pulse widths of two adjacent first pulse signals is zero, namely, the pulse widths of a plurality of continuous pulse signals can be kept unchanged.

In addition, according to an embodiment of the present invention, the pulse widths of the N first pulse signals may also be gradually decreased. The way of gradually decreasing the pulse width is basically the same as the way of gradually increasing the pulse width, and is not described in detail. Alternatively, the pulse widths of the N first pulse signals may be the same, that is: YN-1-YN-2, …, Y2-Y1.

According to an embodiment of the present invention, the preset width threshold may have a value range of 1us to 5us, and preferably 2 us.

In addition, according to the embodiment of fig. 7, in the heating stage, P first pulse signals may be output first, and then Q second pulse signals may be output, where the output time of the P first pulse signals is a first preset time. It should be noted that, the pulse widths of the P first pulse signals in the heating phase may be kept constant and equal to the pulse width of the second pulse signal, or the pulse widths of the P first pulse signals in the heating phase may continue to change according to the change of the N first pulse signals in the discharging phase, for example, the pulse widths of the P first pulse signals may increase or decrease based on the pulse width of the nth first pulse signal in the discharging phase.

According to an embodiment of the present invention, the pulse width of the first pulse signal, i.e., Y1, may be greater than or equal to 0.1us and less than or equal to 10 us.

In addition, according to an embodiment of the present invention, when the target heating power W1 is greater than or equal to the preset power W2, the power switch tube may be driven by the single second driving voltage V2, and the electromagnetic heating system may perform continuous high-power heating.

It should be further noted that, as shown in fig. 8 and 11, the driving circuit of the electromagnetic heating system may include a driving module and a voltage transformation module, the driving module is configured to output a driving pulse signal to the power switching tube to drive the power switching tube to be turned on or off, and the voltage transformation module is configured to adjust a driving voltage of the driving pulse signal. The control unit of the electromagnetic heating system is provided with a first control output end and a second control output end, the first control output end is connected with the driving module, the second control output end is connected with the voltage transformation module, when the control unit outputs a first control signal such as a PPG signal through the first control output end and outputs a second control signal such as a high level signal through the second control output end, the voltage transformation module transforms voltage to adjust the driving voltage of the driving pulse signal to a first driving voltage V1, and the driving circuit can provide the first pulse signal with the amplitude of the first driving voltage V1 to the power switch tube; when the control unit outputs a first control signal such as a PPG signal through the first control output terminal and outputs a third control signal such as a low level signal through the second control output terminal, the voltage transformation module does not transform the voltage, the driving voltage of the driving pulse signal is kept at the second driving voltage V2, and the driving circuit can provide a second pulse signal with the amplitude of the second driving voltage V2 to the power switch tube.

In summary, according to the heating control method of the electromagnetic heating system provided in the embodiment of the present invention, when the target heating power is smaller than the preset power, in each control period, the resonant circuit of the electromagnetic heating system is controlled to sequentially enter the discharging stage, the heating stage, and the stopping stage, wherein N first pulse signals are provided to the power switch tube of the resonant circuit in the discharging stage so that the current flowing through the power switch tube is smaller than the preset current value, P first pulse signals are provided in the heating stage within a first preset time, and Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of the first pulse signal is the first driving voltage, the amplitude of the second pulse signal is the second driving voltage, and the first driving voltage is smaller than the second driving voltage. Therefore, by means of the pre-discharge mode, pulse current of the power switch tube can be restrained, low-power heating of millisecond-pole duty ratio is achieved, and user experience is improved.

Fig. 9 is a block schematic diagram of a heating control device of an electromagnetic heating system according to an embodiment of the present invention. As shown in fig. 9, the heating control device of the electromagnetic heating system includes: adrive circuit 10, aresonant circuit 20 and acontrol unit 30.

Theresonant circuit 20 includes a powerswitching tube driver 40, as shown in fig. 11, the powerswitching tube driver 40 may be an IGBT tube, theresonant circuit 20 further includes a resonant capacitor C2 and a heating coil L2, the resonant capacitor C2 and the heating coil L2 may be connected in parallel, one end of the parallel resonant capacitor C2 and one end of the heating coil L2 are connected to a filter inductor L1 and also connected to one end of the filter capacitor C1, the other end of the filter capacitor C1 is grounded, the other end of the parallel resonant capacitor C2 and the other end of the heating coil L2 are connected to a C pole of the IGBT tube, and an E pole of the IGBT tube is grounded.

The driving circuit 10 is connected to a control end of the power switch tube 40, for example, a G pole of the IGBT, and the driving circuit 10 is configured to drive the power switch tube 40; the control unit 30 is connected to the driving circuit 10, the control unit 30 is configured to obtain a target heating power of the electromagnetic heating system, determine whether the target heating power is smaller than a preset power, and control the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control cycle when the target heating power is smaller than the preset power, wherein the driving circuit 10 is controlled to provide N first pulse signals to the power switch tube 40 in the discharging stage so that a current flowing through the power switch tube 40 is smaller than a preset current value, the driving circuit 10 is controlled to provide Q second pulse signals to the power switch tube 40 after a first preset time in the heating stage after the first preset time is reached, an amplitude of the first pulse signal is a first driving voltage V1, an amplitude of the second pulse signal is a second driving voltage V2, and the first driving voltage V1 is smaller than the second driving voltage V2, wherein N, P, Q is an integer greater than 1.

It should be noted that the values of N, P and Q may be related to the actual control process, such as the pulse width, the pulse width variation of two adjacent pulses, the resonant heating parameter, etc., and the values of N, P and Q may be different in different control processes, so that N, P and Q may not be preset fixed values.

Further, according to an embodiment of the present invention, thecontrol unit 30 is further configured to continuously output a third driving voltage to thepower switch tube 40 during the stop phase, so as to drive thepower switch tube 40 to turn off. Wherein, the third driving voltage may be 0V.

Wherein the target heating power W1 is the heating power required by the electromagnetic heating system under different cooking parameters. For example, when a user wants to cook millet congee, a congee cooking mode can be selected on a control panel of the electromagnetic heating system, the electromagnetic heating system enters the congee cooking mode, and the electromagnetic heating system can perform low-power heating at a heating power of 800W in the congee cooking mode, wherein the corresponding target heating power is 800W.

The preset power W2 may be a power value calibrated according to an actual situation, and when the target heating power W1 is smaller than the preset power W2, it is determined that the electromagnetic heating system is heated at a low power, and when the target heating power W1 is greater than the preset power W2, it is determined that the electromagnetic heating system is heated at a high power.

According to an embodiment of the invention, the predetermined power W2 may be 1400W, thereby reducing noise caused by frequent activation.

According to an embodiment of the present invention, the preset current value may be 85A. The first preset time may be less than or equal to 5 ms.

When thepower switch tube 40, for example, an IGBT tube, is driven by the first driving voltage, thepower switch tube 40 may operate in an amplification state; when the second driving voltage is used to drive the power switch tube, such as an IGBT tube, thepower switch tube 40 can be operated in a saturated conducting state. However, when thepower switch tube 40 is operated in the amplification state, as can be seen from the relationship between the driving voltage and the current of the IGBT shown in fig. 5, thecontrol unit 30 can limit the current of the IGBT tube by adjusting the driving voltage supplied to the IGBT tube, and for example, when the driving voltage supplied to the IGBT tube is 9V, the C-pole current of the IGBT tube can be kept constant at about 22A, and thus, the IGBT tube is driven by sampling the first driving voltage, and the current of the IGBT tube can be limited to 85A or less, thereby effectively suppressing the pulse current.

According to an embodiment of the invention, the first driving voltage V1 may be greater than or equal to 5V and less than or equal to 14.5V, and the second driving voltage V2 may be greater than or equal to 15V. More specifically, thepower switch tube 40 may be an IGBT, the first driving voltage V1 may preferably be 9V, when the first driving voltage supplied to the IGBT is 9V, the C-pole current of the IGBT may be constant around 22A, and the IGBT operates in an amplification state, so that the pulse current is well suppressed. The second driving voltage V2 may preferably be 15V, and the IGBT operates in a saturation state under the driving of the second driving voltage V2. The third driving voltage V3 may be 0V, and the IGBT is turned off by the driving of the third driving voltage V3.

Specifically, when the target heating power W1 is less than the preset power W2, as shown in fig. 6-7, each control cycle includes a discharging phase D1, a heating phase D2 and a stopping phase D3, i.e., in each control cycle, thecontrol unit 30 controls the resonant circuit (e.g., C2 and L2 connected in parallel in fig. 11) to sequentially enter the discharging phase D1, the heating phase D2 and the stopping phase D3. More specifically, the discharging phase D1 can be entered first, and thecontrol unit 30 controls the drivingcircuit 10 to output N first pulse signals to the control terminal of thepower switch tube 40 to discharge the electric energy stored in the filter capacitor (i.e. C1 in fig. 11) during the stop phase in the previous control period, so that the collector voltage of thepower switch tube 40 is substantially 0V when entering the heating phase D2, and the pulse current of thepower switch tube 40 is reduced. After the discharging stage D1 is completed, the heating stage D2 is entered, and in the heating stage D2, the drivingcircuit 10 is controlled to continue outputting the first pulse signal of the first preset time to the control terminal of thepower switch tube 40 to reduce the pulse current of the power switch tube, and then outputting Q second pulse signals to the control terminal of thepower switch tube 40 after the first preset time to make thepower switch tube 40 work in a saturated conducting state, at this time, the electromagnetic heating system can perform normal resonant heating. After the heating phase D2 is completed, the electromagnetic heating system enters the stop phase D3, and in the stop phase D3, thecontrol unit 30 controls the drivingcircuit 10 to output the third driving voltage, i.e., 0V, and does not output the pulse signal, so that thepower switch tube 40 is turned off, and the electromagnetic heating system stops heating.

In addition, the electromagnetic heating system can be controlled to perform low-power heating in a duty ratio mode, namely in each control period, the electromagnetic heating system can be controlled to heat for t1 first and then stop heating for t2, and the duty ratio is t1/(t1+ t 2). Specifically, as shown in fig. 6, in an embodiment of the present invention, the control period may be shortened to millisecond pole, for example, a duty ratio is set in units of a half-wave period of the ac mains, so that the electromagnetic heating system is controlled to perform low-power heating by adopting a millisecond pole duty ratio, where the duty ratio may refer to a ratio of the number of half-waves occupied by the heating stage to the number of half-waves occupied by the whole control period, for example, when the control period is 4 half-waves, if 1 half-wave is heated and 3 half-waves are stopped being heated, the duty ratio is 1/4, that is, the duration of the heating stage D2 in each control period is about one half-wave period; for another example, when the control period is 4 half waves, if 2 half waves are heated and the heating is stopped for 2 half waves, the duty ratio is 2/4, that is, the duration of the heating phase D2 in each control period is about two half-wave periods; as another example, when the control period is 4 half waves, if 3 half waves are heated and 1 half wave is stopped, the duty ratio is 3/4, i.e., the duration of the heating period D2 in each control period is about three half wave periods.

Therefore, the electric energy stored in the filter capacitor is released in a pre-discharging mode, namely in a discharging stage, the pulse current of the power switch tube can be restrained, and further the control period can be shortened to a millisecond pole, so that the heating effect is basically equal to continuous low power.

According to an embodiment of the present invention, the electromagnetic heating system may be powered by an ac power source, as shown in fig. 10, the apparatus further comprising: the electromagnetic heating system comprises a zero-crossingdetection unit 50, the zero-crossingdetection unit 50 is connected with thecontrol unit 30, the zero-crossingdetection unit 50 is used for acquiring the voltage zero-crossing point of the alternating current power supply, and thecontrol unit 30 is used for controlling the electromagnetic heating system to enter a discharging stage according to the voltage zero-crossing point.

It should be noted that thecontrol unit 30 may control theresonant circuit 20 to enter the discharging phase near the voltage zero crossing point, that is, before the voltage zero crossing point, after the voltage zero crossing point, or before the voltage zero crossing point.

According to an embodiment of the present invention, thecontrol unit 30 is further configured to control the electromagnetic heating system to enter the heating phase after entering the discharging phase for a preset time or at a voltage zero crossing point, so that the discharging phase is within a voltage zero crossing interval configured with the voltage zero crossing point as a center.

That is, whether the discharging phase is completed or not can be determined based on time, that is, if the duration of the discharging phase reaches a preset time, thecontrol unit 30 controls the resonant circuit to exit the discharging phase and enter the heating phase. Alternatively, it may also be determined whether the discharging phase is completed by the voltage zero crossing point, that is, if the voltage zero crossing point is detected, thecontrol unit 30 controls the resonant circuit to exit the discharging phase and enter the heating phase.

Wherein, the voltage zero-crossing interval is [ -5ms, 5ms ]. That is, the discharge phase may be within 5ms before and after the voltage zero crossing.

In addition, in an embodiment of the present invention, thecontrol unit 30 may further control the electromagnetic heating system to enter the stop phase according to the voltage zero crossing point.

In particular, in connection with the embodiment of fig. 6, assuming low power heating with a duty cycle of 2/4 is selected according to the target heating power, the total control period is 4 half-waves, the heating period being close to 2 half-waves. Thecontrol unit 30 may perform heating control in the following manner:

thecontrol unit 30 may control the electromagnetic heating system to enter the discharging phase D1 before the first zero-crossing point a1, for example, the first zero-crossing point a1 may be estimated first, then the starting time of the discharging phase D1 is obtained according to the estimated first zero-crossing point a1 and the preset time tf for which the discharging phase D1 needs to last, and thecontrol unit 30 controls the electromagnetic heating system to enter the discharging phase D1 at the starting time, that is, controls the drivingcircuit 10 to output the first pulse signal with the amplitude of the first driving voltage V1 to the power switch tube, so as to release the electric energy stored in the filter capacitor during the stopping phase.

In the process of controlling the drivingcircuit 10 to output the first pulse signal, thecontrol unit 30 detects a voltage zero crossing point in real time through the zero-crossingdetection unit 50, and when the voltage zero crossing point, i.e., the first zero crossing point a1, controls the electromagnetic heating system to enter the heating stage D2, i.e., thecontrol unit 30 controls the drivingcircuit 10 to output the first pulse signal with the amplitude of the first driving voltage V1 to the control end of the power switch tube, and outputs the second pulse signal with the amplitude of the second driving voltage V2 to the control end of thepower switch tube 40 after the first preset time T1, so that thepower switch tube 40 operates in a saturated conduction state, and at this time, the electromagnetic heating system can perform normal resonant heating.

The duration of the heating phase D2 is close to two half-wave cycles, thecontrol unit 30 continues to detect the zero crossing point of the voltage in real time by the zero-crossingdetection unit 50 during the process of controlling the drivingcircuit 10 to output the second pulse signal, and when detecting the third zero crossing point A3, controls the electromagnetic heating system to enter the stop phase D3, that is, thecontrol unit 30 controls the drivingcircuit 10 to continuously output the third driving voltage, that is, 0V, to the control end of thepower switch tube 40, so as to drive thepower switch tube 40 to turn off, and the electromagnetic heating system stops heating.

The duration of the stop phase D3 is close to two half-wave periods, and in the stop phase D3, thecontrol unit 30 may estimate the fifth zero-crossing point a5 first, and then obtain the starting time of the discharging phase D1 in the next control period according to the estimated fifth zero-crossing point a5 and the preset time for which the discharging phase D1 needs to last.

So repeating, low power heating at millisecond duty cycles can be achieved such that the heating effect is substantially equivalent to continuous low power.

According to one embodiment of the present invention, a pulse width of the first pulse signal in the discharging phase is smaller than a pulse width of the second pulse signal in the heating phase. That is, the pulse width of any one of the first pulse signals in the discharging stage is smaller than the pulse width of each of the second pulse signals. In other words, the pulse widths of the N first pulse signals provided in the discharging stage are all smaller than the minimum pulse width of the pulse widths of the Q second pulse signals provided in the heating stage. Wherein, the pulse width may refer to the duration of the high level. In addition, the pulse width of the first pulse signal in the discharging stage may also be smaller than the pulse width of the first pulse signal in the heating stage.

When thepower switching tube 40, for example, an IGBT tube, is driven by the first pulse signal having a narrow pulse width, since it takes a certain time for the pulse current of the IGBT tube to rise, the IGBT tube can be turned off before the pulse current of the IGBT tube rises to a large value by using the narrow pulse width, and the current of the IGBT tube can be limited, for example, to 85A or less, thereby effectively suppressing the pulse current.

According to an embodiment of the present invention, as shown in fig. 7, the pulse widths of the N first pulse signals of the discharging stage are gradually increased. And the difference value of the pulse widths of two adjacent first pulse signals can be less than or equal to a preset width threshold value.

It should be understood that the gradual increase of the pulse widths of the N first pulse signals may refer to that the overall trend of the pulse widths of the N first pulse signals is increasing, and the increasing manner may be various, including but not limited to, sequentially increasing according to the same preset increment, or sequentially increasing according to different preset increments, or the consecutive N pulse widths may be kept unchanged during the increasing process.

Specifically, as shown in fig. 7, it is assumed that the driving circuit outputs N first pulse signals to the power switch during the discharging phase D1 to release the electric energy stored in the filter capacitor during the previous stopping phase D3, wherein,

the pulse widths of the N first pulse signals may be Y1, Y2, …, YN-2, YN-1, YN, respectively. The N first pulse signals show an increasing trend as a whole, for example, the following relationship may be satisfied between the pulse widths of the N pulse signals: yi +1 is not less than Yi + N, where i is 1 to N-1, Yi is the pulse width of the ith first pulse signal, Yi +1 is the pulse width of the i +1 th first pulse signal, and N is a preset width threshold, that is, the pulse width variation of each two adjacent first pulse signals may be equal, that is, gradually increased according to the same preset increment; or the difference of the pulse widths of two adjacent first pulse signals is zero, namely, the pulse widths of a plurality of continuous pulse signals can be kept unchanged.

In addition, according to an embodiment of the present invention, the pulse widths of the N first pulse signals may also be gradually decreased. The way of gradually decreasing the pulse width is basically the same as the way of gradually increasing the pulse width, and is not described in detail. Alternatively, the pulse widths of the N first pulse signals may be the same, that is: YN-1-YN-2, …, Y2-Y1.

According to an embodiment of the present invention, a value range of the preset width threshold may be 1us to 5us, and preferably may be 2 us.

In addition, according to the embodiment of fig. 7, in the heating stage, thecontrol unit 30 may control the drivingcircuit 10 to output P first pulse signals and then output Q second pulse signals, where the output time of the P first pulse signals is a first preset time. It should be noted that, the pulse widths of the P first pulse signals in the heating phase may be kept constant and equal to the pulse width of the second pulse signal, or the pulse widths of the P first pulse signals in the heating phase may continue to change according to the change of the N first pulse signals in the discharging phase, for example, the pulse widths of the P first pulse signals may increase or decrease based on the pulse width of the nth first pulse signal in the discharging phase.

According to an embodiment of the present invention, the pulse width of the first pulse signal, i.e., Y1, may be greater than or equal to 0.1us and less than or equal to 10 us.

In addition, according to an embodiment of the present invention, when the target heating power W1 is greater than or equal to the preset power W2, thecontrol unit 30 may drive thepower switch tube 40 with the single second driving voltage V2, and the electromagnetic heating system may perform continuous high-power heating.

It should be further noted that, as shown in fig. 8 and 11, the drivingcircuit 10 of the electromagnetic heating system may include adriving module 11 and a transformingmodule 12, where the drivingmodule 11 is configured to output a driving pulse signal to thepower switch 30 to drive thepower switch 30 to turn on or off, and the transformingmodule 12 is configured to adjust a driving voltage of the driving pulse signal. Acontrol unit 30 of the electromagnetic heating system has a first control output end PPG and a second control output end EN, the first control output end PPG is connected with a drivingmodule 11, the second control output end EN is connected with avoltage transformation module 12, when thecontrol unit 30 outputs a first control signal such as a PPG signal through the first control output end PPG and outputs a second control signal such as a high level signal through the second control output end EN, thevoltage transformation module 12 transforms voltage to adjust a driving voltage of a driving pulse signal to a first driving voltage V1, and the drivingcircuit 10 can provide the first pulse signal with an amplitude of the first driving voltage V1 to apower switch tube 40; when thecontrol unit 30 outputs a first control signal, for example, a PPG signal, through the first control output terminal PPG and outputs a third control signal, for example, a low-level signal, through the second control output terminal EN, thevoltage transformation module 12 does not transform the voltage, the driving voltage of the driving pulse signal is kept at the second driving voltage V2, and the drivingcircuit 10 may provide the second pulse signal with the amplitude of the second driving voltage V2 to thepower switch tube 40.

In summary, according to the heating control device of the electromagnetic heating system provided in the embodiment of the invention, when the target heating power is smaller than the preset power, in each control period, the control unit controls the resonant circuit of the electromagnetic heating system to sequentially enter the discharging stage, the heating stage, and the stopping stage, wherein in the discharging stage, the driving circuit is controlled to provide N first pulse signals to the power switch tube so that the current flowing through the power switch tube is smaller than the preset current value, and in the heating stage, the driving circuit is controlled to provide P first pulse signals within a first preset time, and then provide Q second pulse signals to the power switch tube after the first preset time, an amplitude of the first pulse signal is the first driving voltage, an amplitude of the second pulse signal is the second driving voltage, and the first driving voltage is smaller than the second driving voltage. Therefore, by means of the pre-discharge mode, pulse current of the power switch tube can be restrained, low-power heating of millisecond-pole duty ratio is achieved, and user experience is improved.

In addition, the embodiment of the invention also provides an electromagnetic heating system.

Fig. 12 is a block schematic diagram of an electromagnetic heating system according to an embodiment of the present invention. As shown in fig. 12, theelectromagnetic heating system 60 includes: the heating control device 70 of the electromagnetic heating system of the above embodiment.

According to one embodiment of the present invention, theelectromagnetic heating system 60 is suitable for an electromagnetic oven, an electromagnetic rice cooker, an electromagnetic pressure cooker, or the like.

According to the electromagnetic heating system provided by the embodiment of the invention, the pulse current of the power switch tube can be inhibited in a pre-discharge mode, so that low-power heating of millisecond pole duty ratio is realized, and the user experience is improved.

Finally, the embodiment of the invention also provides electromagnetic heating equipment, which comprises the electromagnetic heating system of the embodiment.

According to one embodiment of the invention, the electromagnetic heating device is an induction cooker, an electromagnetic rice cooker or an electromagnetic pressure cooker.

According to the electromagnetic heating equipment provided by the embodiment of the invention, the pulse current of the power switch tube can be inhibited in a pre-discharge mode, so that low-power heating of millisecond pole duty ratio is realized, and the user experience is improved.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (23)

1. A heating control method of an electromagnetic heating system is characterized by comprising the following steps:

acquiring target heating power of the electromagnetic heating system;

judging whether the target heating power is smaller than a preset power or not;

if the target heating power is smaller than the preset power, controlling the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control period, wherein N first pulse signals are provided to a power switch tube of a resonance circuit of the electromagnetic heating system in the discharging stage so that the current flowing through the power switch tube is smaller than a preset current value, P first pulse signals are provided in a first preset time in the heating stage, then Q second pulse signals are provided to the power switch tube after the first preset time, the amplitude of the first pulse signals is a first driving voltage, the amplitude of the second pulse signals is a second driving voltage, the first driving voltage is smaller than the second driving voltage, and N, P, Q is an integer larger than 1.

2. The heating control method of the electromagnetic heating system according to claim 1, wherein a third driving voltage is continuously output to the power switch tube during the stop phase to drive the power switch tube to turn off.

3. The heating control method of an electromagnetic heating system according to claim 1, wherein a pulse width of the first pulse signal of the discharging phase is smaller than a pulse width of the second pulse signal of the heating phase.

4. The heating control method of the electromagnetic heating system according to claim 1, wherein a pulse width of the first pulse signal is 0.1us or more and 10us or less.

5. The heating control method of an electromagnetic heating system according to claim 1, wherein the first preset time is 5ms or less.

6. A heating control method of an electromagnetic heating system according to claim 1, wherein the electromagnetic heating system is supplied with power by an alternating current power supply, the method further comprising:

acquiring a voltage zero crossing point of the alternating current power supply;

and controlling the electromagnetic heating system to enter the discharging stage according to the voltage zero crossing point.

7. The heating control method of an electromagnetic heating system according to claim 6, characterized by further comprising: after the preset time of entering the discharging stage or at the voltage zero-crossing point, controlling the resonant circuit to enter the heating stage so as to enable the discharging stage to be in a voltage zero-crossing interval which is constructed by taking the voltage zero-crossing point as the center.

8. The heating control method of an electromagnetic heating system according to claim 7, wherein the voltage zero-crossing interval is [ -5ms, 5ms ].

9. The heating control method of an electromagnetic heating system according to claim 1, characterized in that the first drive voltage is equal to or greater than 5V and equal to or less than 14.5V, and the second drive voltage is equal to or greater than 15V.

10. The heating control method of an electromagnetic heating system according to claim 1, characterized in that the preset current value is 85A.

11. A heating control device of an electromagnetic heating system, comprising:

the resonant circuit comprises a power switch tube;

the driving circuit is connected with the control end of the power switch tube and is used for driving the power switch tube;

a control unit, connected to the driving circuit, for obtaining a target heating power of the electromagnetic heating system, determining whether the target heating power is less than a preset power, and controlling the electromagnetic heating system to sequentially enter a discharging stage, a heating stage and a stopping stage in each control cycle when the target heating power is less than the preset power, wherein the driving circuit is controlled to provide N first pulse signals to the power switch tube in the discharging stage so that a current flowing through the power switch tube is less than a preset current value, and the driving circuit is controlled to provide P first pulse signals in a first preset time and then provide Q second pulse signals to the power switch tube after the first preset time in the heating stage, an amplitude of the first pulse signals is a first driving voltage, the amplitude of the second pulse signal is a second driving voltage, and the first driving voltage is smaller than the second driving voltage, wherein N, P, Q is an integer greater than 1.

12. A heating control device of an electromagnetic heating system as claimed in claim 11, wherein the control unit is further configured to continuously output a third driving voltage to the power switch tube during the stop phase to drive the power switch tube to turn off.

13. A heating control device of an electromagnetic heating system according to claim 11, wherein a pulse width of the first pulse signal of the discharging phase is smaller than a pulse width of the second pulse signal of the heating phase.

14. A heating control apparatus of an electromagnetic heating system according to claim 11, wherein a pulse width of the first pulse signal is 0.1us or more and 10us or less.

15. A heating control device of an electromagnetic heating system according to claim 11, wherein the first preset time is equal to or less than 5 ms.

16. A heating control device of an electromagnetic heating system according to claim 11, wherein the electromagnetic heating system is powered by an alternating current power supply, the device further comprising:

the zero-crossing detection unit is connected with the control unit and used for acquiring a voltage zero-crossing point of the alternating current power supply, and the control unit is used for controlling the electromagnetic heating system to enter the discharging stage according to the voltage zero-crossing point.

17. A heating control device of an electromagnetic heating system according to claim 16, characterized in that the control unit is further configured to control the resonance circuit to enter the heating phase after entering the discharging phase for a preset time or at the voltage zero-crossing point, so that the discharging phase is within a voltage zero-crossing interval configured with the voltage zero-crossing point as a center.

18. A heating control device of an electromagnetic heating system according to claim 17, wherein the voltage zero-crossing is [ -5ms, 5ms ].

19. A heating control device of an electromagnetic heating system according to claim 11, wherein the first drive voltage is equal to or greater than 5V and equal to or less than 14.5V, and the second drive voltage is equal to or greater than 15V.

20. A heating control device of an electromagnetic heating system according to claim 11, characterized in that the preset current value is 85A.

21. An electromagnetic heating system, characterized by comprising a heating control device of an electromagnetic heating system according to any one of claims 11-20.

22. An electromagnetic heating apparatus, characterized by comprising an electromagnetic heating system according to claim 21.

23. The electromagnetic heating apparatus according to claim 22, wherein the electromagnetic heating apparatus is an induction cooker, an induction cooker or an induction pressure cooker.

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