Summary of the invention
The objective of the invention is to defective at existing continuous mode power factor corrector, a kind of continuous mode power factor corrector of adjusting operating frequency according to the output current size is provided, reduce its switching loss and capacitive loss under the undercapacity condition, to improve the average efficiency of power factor corrector.
Purpose of the present invention is achieved by the following technical programs:
A kind of power factor corrector comprises input ac power Vac,rectifier bridge 1, PFC inductance 2,switching tube 3,output rectifying tube 4,output filter capacitor 5,load 7, continuous current modePFC control unit 9, outputvoltage detecting circuit 10,current sampling resistor 11 compositions; Wherein the negative pole ofoutput filter capacitor 5 is defined as ground, the input of describedrectifier bridge 1 is connected in AC power Vac, one end of the output cathode series connection PFC inductance 2 ofrectifier bridge 1, the anode of the drain electrode of the other end of PFC inductance 2 and switchingtube 3 andoutput rectifying tube 4 connects same point altogether, the source ground ofswitching tube 3, the grid ofswitching tube 3 is the signal output part of continuous current-modePFC control unit 9 in succession, the negative electrode ofoutput rectifying tube 4 and the positive pole ofoutput filter capacitor 5, the positive pole ofload 7 connects, outputvoltage detecting circuit 10 is byresistance R 1, resistance R 2 is formed, one end ofresistance R 1 is connected to the negative electrode ofoutput rectifying tube 4, the other end is connected with an end of resistance R 2, resistance R 2 other end ground connection,current sampling resistor 11 is connected between the output negative terminal of the source electrode ofswitching tube 3 andrectifier bridge 1, the negative pole ofoutput filter capacitor 5 is connected to the source electrode ofswitching tube 3, the negative pole ofload 7 is connected with the negative pole ofoutput filter capacitor 5, above-mentioned PFC inductance 2 two ends, between the source electrode ofswitching tube 3 and the drain electrode, parasitic capacitance in parallel separately betweenoutput rectifying tube 4 both positive and negative polarities.Can adjust operating frequency according to the output current size in order to make power factor corrector, this circuit comprises that also output current detects amplifying circuit 6, voltage controlledoscillator 8, described output current detects between the negative pole that amplifying circuit 6 is connected in the negative pole ofload 7 andoutput filter capacitor 5, the output load current signal is detected and handles, described output current detects the input that amplifying circuit 6 outputs are connected in voltage controlledoscillator 8, export a control signal and give voltage controlledoscillator 8, voltage controlledoscillator 8 produces the sawtooth waveforms Fs of a respective frequencies, the output of voltage controlledoscillator 8 is connected in the frequency input of continuous current modePFC control unit 9, sawtooth waveforms Fs is delivered to continuous current modePFC control unit 9, thus the operating frequency ofcontrol switch pipe 3.
Purpose of the present invention can also further realize by following technical measures:
Aforementioned a kind of power factor corrector, wherein output current detection amplifying circuit 6 comprises resistance RSen2, resistance RI3, resistance RF1, capacitor CZ1, current error amplifier U1, described resistance RSen2Two ends are connected between the negative pole of the negative pole ofload 7 andoutput filter capacitor 5, described resistance RI3An end be connected in the negative pole ofoutput filter capacitor 5, the other end is connected in the input negative terminal of current error amplifier U1, the positive termination reference voltage V of the input of current error amplifier U1Ref2, the output of current error amplifier U1 is connected in the input of voltage controlledoscillator 8, described resistance RF1, capacitor CZ1Series connection, series circuit one end is connected with the input negative terminal of current error amplifier U1, and the series circuit other end is connected with the output of current error amplifier U1.
Aforementioned a kind of power factor corrector, wherein continuous current modePFC control unit 9 comprises current error amplifier U2, multiplier U3, PWM generator U4, low pass filter LPF, voltage error amplifier VEA, output driving circuit, squaring circuit X2, resistance RIAC, resistance RI2, resistance R3, resistance RF2, capacitor Cp, capacitor CZ2Described resistance RIACOne end is connected in the output cathode ofrectifier bridge 1, and the other end is connected in the input of multiplier U3 and the input of low pass filter LPF, and the output of low pass filter LPF is connected in squaring circuit X2Input, squaring circuit X2Output be connected in the input of multiplier U3; Voltage error amplifier VEAThe input negative terminal be connected betweenresistance R 1, the resistance R 2 voltage error amplifier VEAThe positive termination reference voltage V of inputRef1, its output is connected in the input of multiplier U3; Described resistance RI2An end be connected in the output negative pole ofrectifier bridge 1, the other end is connected in the output of multiplier U3, the input negative terminal of current error amplifier U2 links to each other with the output of multiplier U3, the input anode of current error amplifier U2 is connected in resistance R3An end, resistance R3Other end ground connection, resistance RF2With capacitor CZ2Series connection, series circuit and capacitor CpParallel connection, this parallel circuits one is terminated at the input negative terminal of current error amplifier U2, and the other end is connected to the output of current error amplifier U2; The input negative terminal of described PWM generator U4 links to each other with the output of current error amplifier U2, the input anode of PWM generator U4 is connected with the output of voltage controlledoscillator 8, the output of PWM generator U4 is connected in the output driving circuit input, and the output driving circuit output connects the grid ofswitching tube 3.
Compared with prior art, the invention has the beneficial effects as follows: thus because the operating frequency of power factor corrector is subjected to output current regulating to reduce switching loss and the capacitive loss of power factor corrector under the undercapacity condition, promoted the average efficiency of power factor corrector.
Embodiment
The invention will be further described below in conjunction with the drawings and specific embodiments.
As shown in Figure 1, the present invention includes input ac power Vac,rectifier bridge 1, PFC inductance 2,switching tube 3,output rectifying tube 4,output filter capacitor 5,load 7, continuous current modePFC control unit 9, outputvoltage detecting circuit 10,current sampling resistor 11 compositions, wherein the negative pole ofoutput filter capacitor 5 is defined as ground.The input of describedrectifier bridge 1 is connected in AC power Vac, one end of the output cathode series connection PFC inductance 2 ofrectifier bridge 1, the anode of the drain electrode of the other end of PFC inductance 2 and switchingtube 3 andoutput rectifying tube 4 connects same point altogether, the source ground ofswitching tube 3, the grid ofswitching tube 3 is the signal output part of continuous current-modePFC control unit 9 in succession, the negative electrode ofoutput rectifying tube 4 and the positive pole ofoutput filter capacitor 5, the positive pole ofload 7 connects, outputvoltage detecting circuit 10 is byresistance R 1, resistance R 2 is formed, one end ofresistance R 1 is connected to the negative electrode ofoutput rectifying tube 4, the other end is connected with an end of resistance R 2, resistance R 2 other end ground connection,current sampling resistor 11 is connected between the output negative terminal of the source electrode ofswitching tube 3 andrectifier bridge 1, the negative pole ofoutput filter capacitor 5 is connected to the source electrode ofswitching tube 3, the negative pole ofload 7 is connected with the negative pole ofoutput filter capacitor 5, above-mentioned PFC inductance 2 two ends, between the source electrode ofswitching tube 3 and the drain electrode, parasitic capacitance in parallel separately betweenoutput rectifying tube 4 both positive and negative polarities.In order to make power factor corrector adjust operating frequency according to the output current size, this circuit comprises that also output current detects amplifying circuit 6, voltage controlled oscillator 8.Described output current detects between the negative pole that amplifying circuit 6 is connected in the negative pole ofload 7 andoutput filter capacitor 5, and the output load current signal is detected and handles, and concrete output current detects amplifying circuit 6 and comprises resistance RSen2, resistance RI3, resistance RF1, capacitor CZ1, current error amplifier U1, described resistance RSen2Two ends are connected between the negative pole of the negative pole ofload 7 andoutput filter capacitor 5, described resistance RI3An end be connected in the negative pole ofoutput filter capacitor 5, the other end is connected in the input negative terminal of current error amplifier U1, the positive termination reference voltage V of the input of current error amplifier U1Ref2, the output of current error amplifier U1 is connected in the input of voltage controlledoscillator 8, described resistance RF1, capacitor CZ1Series connection, series circuit one end is connected with the input negative terminal of current error amplifier U1, and the series circuit other end is connected with the output of current error amplifier U1.
Aforesaid continuous current modePFC control unit 9 specifically comprises current error amplifier U2, multiplier U3.PWM generator U4, low pass filter LPF, voltage error amplifier VEA, output driving circuit, squaring circuit X2, resistance RIAC, resistance RI2, resistance R3, resistance RF2, capacitor Cp, capacitor CZ2Described resistance RIACOne end is connected in the output cathode ofrectifier bridge 1, and the other end is connected in the input of multiplier U3 and the input of low pass filter LPF, and the output of low pass filter LPF is connected in squaring circuit X2Input, squaring circuit X2Output be connected in the input of multiplier U3; Voltage error amplifier VEAThe input negative terminal be connected betweenresistance R 1, the resistance R 2 voltage error amplifier VEAThe positive termination reference voltage V of inputRef1, its output is connected in the input of multiplier U3; Described resistance RI2An end be connected in the output negative pole ofrectifier bridge 1, the other end is connected in the output of multiplier U3, the input negative terminal of current error amplifier U2 links to each other with the output of multiplier U3, the input anode of current error amplifier U2 is connected in resistance R3An end, resistance R3Other end ground connection, resistance RF2With capacitor CZ2Series connection, series circuit and capacitor CpParallel connection, this parallel circuits one is terminated at the input negative terminal of current error amplifier U2, and the other end is connected to the output of current error amplifier U2; The input negative terminal of described PWM generator U4 links to each other with the output of current error amplifier U2, the input anode of PWM generator U4 is connected with the output of voltage controlledoscillator 8, voltage controlledoscillator 8 is delivered to PWM generator U4 with the sawtooth waveforms Fs of its generation, the output of PWM generator U4 is connected in the output driving circuit input, the output driving circuit output connects the grid ofswitching tube 3, thus the operating frequency of removingcontrol switch pipe 3 by the generation of sawtooth waveforms Fs control PWM ripple like this.
The control strategy that the present invention adopts is certain corresponding certain switch operating frequency of load, and the corresponding relation of its frequency and output current can be linear, non-linear and other corresponding relation, and this operating frequency is not subjected to the influence of input voltage size or shape.Its working condition is identical with existing continuous mode power factor corrector under full load conditions.Confirmed following condition establishment before analyzing this circuit: (1) continuous current modePFC control unit 9 is the continuous current mode power factor correcting device of telotism, and its operating frequency is provided by the outside.(2) the current sample mode is a resistance sampling.(3) load minimum current is Imin, and corresponding minimum frequency of operation is Fs_min, and the load maximum current is Imax, and corresponding maximum operation frequency is Fs_max, and Io is a load current, Fs be the switching tube operating frequency and: Imin≤Io≤Imax; Fs_min≤Fs≤Fs_max.
Main circuit of the present invention is made up of PFC inductance 2, switchingtube 3,output rectifying tube 4,output filter capacitor 5, and its topology is the Boost circuit.Ac grid voltage Vac input is after rectification obtains commutating voltage Vin, switchingtube 3 ends earlier, after electric capacity is charged to certain value, switchingtube 3 begins according to the conducting of PWM rule and ends, storage and release with control inductance self-energy, and pass throughoutput rectifying tube 4 tooutput filter capacitor 5 chargings, and be sent to load 7, finish the function that alternating voltage is transferred to direct voltage.Control circuit is made up of the two large divisions, and a part is continuous current mode PFC control unit 9 (CCM PFC Control), and it is by voltage error amplifier VEA, current error amplifier U2, multiplier U3, PWM generator U4, low pass filter LPF compositions such as (Low pass filter); Another part is the Current Control frequency cells, and it detects amplifying circuit 6 (Current Detecting Unit) by output current and voltage controlled oscillator is formed.The outputvoltage detecting circuit 10 that Voltage loop in the closed-loop system is made up of resistor voltage divider network, voltage error amplifier VEA, multiplier U3, current error amplifier U2, compositions such as PWM generator U4.Its form is similar to the Voltage loop in the general voltage control pulse modulation technique, to reach the purpose that keeps output voltage stabilization.Electric current loop in the closed-loop system is bycurrent sampling resistor 11, current error amplifier U2,, PWM generator U4 forms.The output voltage V out sampling value and the reference voltage V ref1 of main circuit input to voltage error amplifier VEAThe detected value K of voltage Vin after the rectification and voltage error amplifier VEA output voltage V va are added to the input of multiplier U3 jointly.The output signal Vm of multiplier U3 is as the reference signal of Current Feedback Control signal, therefore current reference signal is two half-sine waves, detected value Iin * Rsen1 of it and input current Iin relatively after, be added to PWM generator U4 through current error amplifier U2 and produce pwm signal, with the break-make of switching tube in the control Boost DC/DC converter.Thereby make the waveform basically identical of the waveform of input current Iin and the voltage Vin after the rectification, and same-phase.So just make that current harmonics greatly reduces, thereby improved power factor.The frequency control loop course of work of this circuit is: output current detects amplifying circuit 6 by detection and processing to output load current, export a control signal Vo and this signal is delivered to the input of voltage controlled oscillator, voltage controlled oscillator produces the sawtooth waveforms Fs of a respective frequencies, sawtooth waveforms Fs signal send the synchronous signal input end of continuous current modePFC control unit 9, be the input anode of PWM generator U4, with the operating frequency of control switch pipe.
According to Cao Lingling, the efficiency analysis of Chen Ganhong power factor corrector of disclosed continuous current mode of operation in " time variant voltage DBPFC and BOOST PFC efficiency analysis pair with contrast " (airplane power source science and technology of aviation key lab is academic, and annual meeting---APSC ' 2009) with calculate and can know, the main loss of the power factor corrector of tradition under the continuous mode is made up of the conduction loss of switch module and line resistance and the switching loss of switch module and the capacitive loss of switch element parasitic capacitance, wherein switching loss accounts for its major ingredients, switching loss is directly proportional with its operating frequency with the capacitive loss, conduction loss and frequency-independent, relevant result calculated is as follows:
The turn-off power loss P of 1 output rectifier diodeDiode_off=K1FS_pfc
2 switching tube turn-on consumption PSw_on=K2FS_pfc
3 switching tube turn-off power loss PSw_off=K3FS_pfc
The parasitic capacitance loss P of 4 switching tubes, output diode, inductanceSw_c=K4FS_pfc
(K1, K2, K3, K4Be the coefficient relevant) with component parameters
Reduce operating frequency as shown from the above formula and will reduce overall loss, at output voltage one regularly, the setting of minimum frequency of operation is subject to the volume of maximum output current and minimum input voltage and PFC inductance, therefore under the volume situation of identical PFC inductance, fixing caused switching loss of operating frequency and capacitive loss are had a strong impact on system's efficient under the undercapacity situation, and influence is even more serious when underloading.Utilization of the present invention peak inrush current by the PFC inductance when output current reduces will reduce, the applicable AC magnetism induction of its magnetic core this moment will become big, thereby the value permission of the forward weber of inductance becomes big, under the constant situation of duty ratio, reduce its operating frequency, reduce the switching loss and the capacitive loss of system, can improve the efficient of CCM PFC power factor corrector under the undercapacity situation effectively.
The present invention carries out actual verification on the power factor corrector of 200W, and traditional C CM PFC controlling schemes efficient that obtains and the efficient that obtains with apparatus of the present invention (frequency is subjected to the power factor corrector of the continuous mode of output current adjusting) are compared.
Fig. 2 is that its operating frequency is 85KHz under the traditional C CM PFC fixed frequency condition, and input voltage is respectively 100V, 160V, 264V, the efficient when output voltage is 390V and the relation curve of load.
Fig. 3 is that apparatus of the present invention are subjected under the output current adjusting pattern in frequency, and its maximum operation frequency is 85KHz, and minimum frequency of operation is 45KHz, and input voltage is respectively 100V, 160V, 264V, the efficient when output voltage is 390V and the relation curve of load.
Fig. 4 is that its operating frequency is 85KHz under the traditional C CM PFC fixed frequency condition, and output voltage is 390V, the efficient when output current is respectively 0.3A and 0.5A and the relation curve of input voltage.
Fig. 5 is that apparatus of the present invention are subjected under the output current adjusting pattern in frequency, and its maximum operation frequency is 85KHz, and minimum frequency of operation is 45KHz, and output voltage is 390V, the efficient when output current is respectively 0.3A and 0.5A and the relation curve of input voltage.
Can find that from the contrast of contrast, Fig. 4 and Fig. 5 of Fig. 2 and Fig. 3 apparatus of the present invention can improve the average efficiency of power factor corrector under the undercapacity condition greatly.
In addition to the implementation, the present invention can also have other execution modes, and all employings are equal to the technical scheme of replacement or equivalent transformation formation, all drop in the protection range of requirement of the present invention.