CN201601610U - Inverter circuit - Google Patents

Abstract

The utility model discloses an inverter circuit, which is used as a rotating-speed adjusting and driving device of an AC motor. The inverter circuit comprises a current transformer, a current sampling and processing circuit which is connected with the current transformer, an input rectifier filter circuit, a bus voltage sampling circuit and an inverter circuit which are connected with the input rectifier filter circuit, a PWM driving circuit which is connected with the inverter circuit, a microprocessor circuit which is connected with the current sampling and processing circuit and the PWM driving circuit and the bus voltage sampling circuit; the inverter circuit is connected with a motor M. The characteristics are as follows: the current sampling and processing circuit comprises a current signal detecting and processing circuit and a dead-zone detecting circuit. The advantages are as follows: the circuit is simple, the cost is low, the detecting accuracy of the output current is increased, the polarity and the value of the current signal can be detected more accurately; the inverter circuit can increase the accuracy of the dead-zone compensation when being used for dead-zone compensation, avoids distortion of the current signal, decreases the harmonic wave of the output current, and inhibits oscillation of the current.

Description

A kind of converter circuit

Technical field

The utility model relates to a kind of converter circuit, especially improves the circuit of frequency converter upper and lower bridge arm dead area compensation accuracy, as alternating current motor rotational speed regulation drive unit.

Background technology

Frequency converter is as the drive unit of alternating current motor rotational speed regulation, be desirable, the most promising speed regulating device of alternating current motor of generally acknowledging at present, it has good speed adjusting performance, energy-conserving action and technology controlling and process mode, is the ideal device that vast enterprise carries out equipment technology reconstruction and transmission model change.Along with worldwide energy problem is becoming tight day, from the strategy of national energy-conserving and environment-protective, frequency control has very big development space as energy-conservation a kind of effective means; In addition, realize that automation control will be the direction of electrical apparatus industry development from now on, in conjunction with China present level of production and development speed, frequency converter will be widely used in the production of reality as automation equipment important in the speed technology controlling and process.Therefore present stage discussion frequency converter is the requirement of having complied with era development.

In the frequency converter of various pulse-width modulations (PWM) type,, all be provided with Dead Time for two pipes up and down that prevent a brachium pontis of switching device power model damage owing to straight-through.In Dead Time, because pipe does not all have triggering signal up and down, output voltage depends on the polarity of output current fully, so output voltage is uncontrollable.Its direct result that causes is exactly to produce error between the output voltage and instruction voltage, and output current produces distortion.Motor is when low speed, and then torque produces pulsation, and the ability of output torque reduces, even the situation with not dynamic load occurs.

In the existing frequency converter, generally all this Dead Time is compensated.It is the method that adopts software that a kind of compensation method is arranged, by electric current is detected, judge that its polarity obtains the direction of dead area compensation, in this method, if when adopting the single current sample circuit to measure current signal, take intoaccount 2 times of load current values of frequency converter and near 0 current detecting, this point is difficult to accomplish, therefore may cause the mistake of current polarity judgement, thereby cause the generation of mistake compensation.

Summary of the invention

Task of the present utility model is to solve the deficiencies in the prior art, provides that a kind of circuit is simple, cost is low, improves frequency converter upper and lower bridge arm dead area compensation accuracy, avoids the distortion of current signal and suppresses the converter circuit of current oscillation.

Task of the present utility model is finished like this, a kind of converter circuit, comprise current transformer, the current sample treatment circuit that is connected with current transformer, the input rectifying filter circuit, the busbar voltage sample circuit and the inverter circuit that are connected with the input rectifying filter circuit, the PWM drive circuit that is connected with inverter circuit, with the current sample treatment circuit, PWM drive circuit and busbar voltage sample circuit microprocessor linked circuit, inverter circuit is connected with motor M, is characterized in: described current sample treatment circuit detects treatment circuit by current signal and the dead band testing circuit is formed.Current signal detects the detection that treatment circuit is used for output current, and the dead band testing circuit is mainly used in the detection of the positive-negative polarity of output current signal, is used for dead area compensation and judges.The dead band testing circuit can comprise journey current sample modulate circuit in a small amount, current signal zero cross detection circuit etc. by accomplished in many ways.

Current signal described in the utility model detects treatment circuit by resistance R 2-R4, R8, R10, capacitor C 1, C3, double diode D1 and amplifier U1D form, one end ofresistance R 2 is connected with power supply Vref, the other end ofresistance R 2 is connected with an end ofresistance R 3 and 1 pin of amplifier U1D, 2 pin of amplifier U1D are connected with an end of an end ofresistance R 4 and resistance R 8, the other end ofresistance R 4 is connected with an end summation current transformer CT of capacitor C 1, the other end of resistance R 8 is connected with 3 pin of amplifier U1D and an end of resistance R 10, one end of the other end of resistance R 10 andcapacitor C 3, the end of MCU in 1 end of double diode D1 and the microcontroller circuit is connected, 2 pin of double diode D1 are connected with DC power supply VCC1, the other end ofresistance R 3, capacitor C 1, the 3 pin common grounds of the other end of C3 and double diode D1.

Dead band described in the utility model testing circuit is by resistance R 5-R7, R9, R11,capacitor C 2, C4, double diode D2 and amplifier U2D form, one end ofresistance R 5 is connected with power supply Vref, the other end ofresistance R 5 is connected with an end ofresistance R 6 and 1 pin of amplifier U2D, 2 pin of amplifier U2D are connected with an end of an end ofresistance R 7 and resistance R 9, the other end ofresistance R 7 is connected with an end summation current transformer CT ofcapacitor C 2, the other end of resistance R 9 is connected with 3 pin of amplifier U2D and an end of resistance R 11, one end of the other end of resistance R 11 andcapacitor C 4, the other end of MCU in 1 end of double diode D2 and the microcontroller circuit is connected, 2 pin of double diode D2 are connected with DC power supply VCC1, the other end ofresistance R 6,capacitor C 2, the 3 pin common grounds of the other end of C4 and double diode D2.

Because the utility model adopts current signal to detect treatment circuit and the dead band testing circuit detects current symbol, circuit is simple, cost is low, improve the detection accuracy of output current, can detect the polarity and the numerical value of current signal more accurately, be used for dead area compensation, improve the accuracy of dead area compensation, avoid the distortion of current signal, reduced the harmonic wave of output current, suppressed the vibration of electric current.

Description of drawings

Fig. 1 is a theory diagram of the present utility model.

Fig. 2 is the theory diagram of the utility model current sample treatment circuit.

Fig. 3 is the electrical schematic diagram of the utility model current sample treatment circuit.

Embodiment

See also Fig. 1, the theory diagram of converter circuit.Input rectifying filter circuit 1 is circuit diagram commonly used.Busbarvoltage sample circuit 3,microcontroller circuit 4,PWM drive circuit 5 andinverter circuit 6 all are the common circuit in the converter circuit, include the MCU microprocessor in themicrocontroller circuit 4.

See also Fig. 2, described currentsample treatment circuit 2 comprises that the current signal that is used for the output current detectiondetects treatment circuit 21, measure the positive-negative polarity of current signal, be used for the deadband testing circuit 22 that dead area compensation is judged, the signal that currentsample treatment circuit 2 obtains from the current sensor sampling, be divided into two-way, one the tunnel sends into current signaldetection treatment circuit 21 carries out the output current detection, through after the Filtering Processing, signal is sent into the A/D conversion mouth of MCU, one the tunnel sends into deadband testing circuit 22, a current with high accuracy signal is provided, and the polarity that is used for current compensation is judged, sends into MCU through after the Filtering Processing then.

Seeing also Fig. 3 is current sample treatment circuit one embodiment of the present utility model, current signal converts voltage signal (is that voltage signal does not just need transfer resistance R1 as current sensor output) to through over-current sensor CT1, sampling resistor R1, be divided into two-way then and deliver to current signal detection treatment circuit and dead area compensation testing circuit respectively, right latter two signal is delivered to MCU respectively after resistance R 10,capacitor C 3 and resistance R 11,capacitor C 4 filtering, finish the dead area compensation to electric current after being calculated by MCU.Current signal detect treatment circuit be with signal through capacitor C 1 filtering after, throughresistance R 2, R3, R4, R8 and amplifier U1D the whole waveform of current signal is nursed one's health the input range of MCU again, be used for the detection of electric current.The dead area compensation testing circuit be with signal through aftercapacitor C 2 filtering, again throughresistance R 5, R6, R7, R9 and amplifier U2D with the signal condition of the near zero-crossing point of current signal input range to MCU, be convenient to the judgement of current signal polarity.Double diode D1, D2 play the amplitude limit effect, and protection MCU avoids external high voltage and damages.

Claims (3)

1. converter circuit, comprise current transformer (7), the current sample treatment circuit (2) that is connected with current transformer (7), input rectifying filter circuit (1), busbar voltage sample circuit (3) that is connected with input rectifying filter circuit (1) and inverter circuit (6), the PWM drive circuit (5) that is connected with inverter circuit (6), with current sample treatment circuit (2), PWM drive circuit (5) and busbar voltage sample circuit (3) microprocessor linked circuit (4), inverter circuit (6) is connected with motor M, it is characterized in that described current sample treatment circuit (2) detects treatment circuit (21) by current signal and dead band testing circuit (22) is formed.

2. converter circuit according to claim 1, it is characterized in that described current signal detects treatment circuit (21) by resistance R 2-R4, R8, R10, capacitor C 1, C3, double diode D1 and amplifier U1D form, one end of resistance R 2 is connected with power supply Vref, the other end of resistance R 2 is connected with an end of resistance R 3 and 1 pin of amplifier U1D, 2 pin of amplifier U1D are connected with an end of an end of resistance R 4 and resistance R 8, the other end of resistance R 4 is connected with an end summation current transformer CT of capacitor C 1, the other end of resistance R 8 is connected with 3 pin of amplifier U1D and an end of resistance R 10, one end of the other end of resistance R 10 and capacitor C 3, the end of MCU in 1 end of double diode D1 and the microcontroller circuit is connected, 2 pin of double diode D1 are connected with DC power supply VCC1, the other end of resistance R 3, capacitor C 1, the 3 pin common grounds of the other end of C3 and double diode D1.

3. converter circuit according to claim 1, it is characterized in that described dead band testing circuit circuit (22) is by resistance R 5-R7, R9, R11, capacitor C 2, C4, double diode D2 and amplifier U2D form, one end of resistance R 5 is connected with power supply Vref, the other end of resistance R 5 is connected with an end of resistance R 6 and 1 pin of amplifier U2D, 2 pin of amplifier U2D are connected with an end of an end of resistance R 7 and resistance R 9, the other end of resistance R 7 is connected with an end summation current transformer CT of capacitor C 2, the other end of resistance R 9 is connected with 3 pin of amplifier U2D and an end of resistance R 11, one end of the other end of resistance R 11 and capacitor C 4, the other end of MCU in 1 end of double diode D2 and the microcontroller circuit is connected, 2 pin of double diode D2 are connected with DC power supply VCC1, the other end of resistance R 6, capacitor C 2, the 3 pin common grounds of the other end of C4 and double diode D2.

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