TW201839541A - Phase compensation method for power factor correction circuit - Google Patents

Abstract

A method for phase compensating a power factor correction circuit is provided. The power factor correction circuit receives an input voltage and an input current. The method comprises steps of: (a) sampling a present current value of an input current, and filtering the sampled signal; (b) predicting a present waveform of the input current corresponding to the present current value of the filtered sampled signal and a previous waveform of the input current corresponding to a previous current value of the filtered sampled signal, and generating a current error signal according to a difference between the present waveform and the previous waveform; (c) adjusting the current error signal, thereby generating an adjusted signal; (d) adding a feedforward signal to the adjusted signal, thereby generating a phase compensation signal; and (e) adding a current control signal to the phase compensation signal, thereby generating a pulse width modulation signal to control the switching circuit.

Description

Phase compensation method suitable for power factor correction circuit

The present invention relates to a phase compensation method, and more particularly to a phase compensation method suitable for a power factor correction circuit.

The load may be represented by a resistive impedance, an inductive impedance, a capacitive impedance, or a combination thereof for the power conversion device. When the current input to the load is in phase with the voltage applied to the load, the power factor is close to one. When the power factor is less than 1, the transmitted power may be lost due to phase mismatch between current and voltage or the introduction of noise.

Therefore, in order to avoid the power factor reduction and improve the efficiency, the conventional power conversion device usually has a power factor correction function, for example, by configuring an active power factor correction (PFC) circuit, which can be sampled in a feedforward manner. The received AC input voltage, and then the output current output by the AC input voltage is adjusted, so that the AC input current received by the power factor correction circuit follows the AC input voltage, thereby obtaining an AC input that is close to a sinusoidal waveform and is in phase. Current to increase power factor and reduce current harmonics.

However, the conventional power factor correction circuit has a bridge rectifier diode, and the forward voltage drop of the bridge rectifier diode and the high frequency filter capacitor disposed after the bridge rectifier diode cause AC communication. The input current is stalled near the zero point of the AC input voltage and its distortion, resulting in zero-crossing distortion, which increases the total harmonic distortion and leads to a reduction in power factor.

Therefore, how to develop a phase compensation method suitable for a power factor correction circuit which can improve the above-mentioned conventional techniques is an urgent need.

The purpose of the present invention is to provide a phase compensation method suitable for a power factor correction circuit, which solves the problem that the conventional power factor correction circuit has zero crossover distortion, such as total harmonic distortion increase and power factor reduction.

In order to achieve the above object, the present invention provides a phase compensation method for a power factor correction circuit, the power factor correction circuit receives an input voltage and an input current, and includes a switch circuit and a control unit, and the switch circuit is controlled by the control unit. Or the operation of the cutoff, the power factor correction circuit outputs the output voltage and the output current, and the control unit comprises a low pass filter, a differential controller and a cosine multiplier, wherein the low pass filter continuously receives the input current sampling signal reflecting the current input current. The phase compensation method comprises the steps of: (a) generating a corresponding input current sampling signal according to the current input current, and filtering the input current sampling signal by using a low-pass filter; (b) using the differential controller to receive according to the current The filtered input current sampling signal and the previously received filtered input current sampling signal predict the waveform of the current input current and the waveform of the previous input current, and according to the waveform of the current input current and the waveform of the previous input current Difference produces a current error signal; (c) uses cosine The device adjusts the current error signal to generate an adjustment signal; (d) superimposes the adjustment signal and the feedforward signal to generate a phase compensation signal; (e) superimposes the phase compensation signal and the current control signal to generate a pulse The width modulation signal, and the pulse width modulation signal is used to control the operation of the switching circuit.

Some exemplary embodiments embodying the features and advantages of the present invention are described in detail in the following description. It should be understood that the present invention is capable of various modifications in various aspects, and is not intended to limit the scope of the present invention.

Please refer to FIG. 1 , which is a schematic diagram of the circuit structure of the power factor correction circuit of the preferred embodiment of the present invention. As shown in FIG. 1, the power factor correction circuit 1 of the present invention can be applied to a power conversion device (not shown) for improving the power factor of the power conversion device, and the power factor correction circuit 1 receives an input current Iin. And an input voltage Vin, and output an output current Iout and an output voltage Vout, and include a switch circuit 10 and a control unit 20. The switching circuit 10 can perform an on or off switching operation to cause the power factor correction circuit 1 to generate an output current Iout and an output voltage Vout. The control unit 20 outputs a corresponding pulse width modulation signal D_pwm according to the input current Iin, the input voltage Vin and the output voltage Vout to control the operation of the switching circuit 10, thereby adjusting the phase of the input current Iin and the phase of the input voltage Vin. Consistent, and eliminate the phenomenon of pause and distortion of the input current Iin near the zero point of the input voltage Vin (zero crossover distortion).

Please refer to FIG. 2 and cooperate with FIG. 1 , wherein FIG. 2 is a schematic diagram of the operation principle of the control unit shown in FIG. 1 . As shown in FIG. 2, the control unit 20 includes a low pass filter 22, a differential controller 23, a cosine multiplier 24, a first adder 25, and a second adder 26.

The low pass filter 22 can continuously receive an input current sampling signal reflecting one of the input currents Iin received by the power factor correction circuit 1 and filter the input current sampling signal.

The differential controller 23 is electrically connected to the low pass filter 22, which receives the filtered input current sampling signal transmitted by each low pass filter 22, and has a register for storing the signal, and the differential controller 23, each time receiving the filtered input current sampling signal transmitted by the low-pass filter 22, updating the signal in the temporary register to the filtered input current sampling signal received at the moment, in addition, in the update Before the signal in the memory is the filtered input current sampling signal received by the current, the differential controller 23 first predicts the waveform of the current input current Iin according to the filtered input current sampling signal received, and according to The signal stored in the register predicts the waveform of the signal stored in the register, compares the waveform of the current input current Iin and the waveform of the signal stored in the register, and outputs a current error according to the difference between the waveforms of the two The signal, wherein the differential controller 23 outputs a zero current error signal if the register has not yet stored the signal. Therefore, in the present embodiment, when the power factor correction circuit 1 is not operating, virtually no signal is stored in the register of the differential controller 23, so when the power factor correction circuit 1 starts operating and the differential controller 23 is first When the filtered input current sampling signal is received, since there is no signal stored in the register at this time, the differential controller 23 outputs a zero current error signal, and the differential controller 23 continues to receive the current time. The filtered input current sampling signal is stored in the temporary register, and when the differential controller 23 receives the filtered input current sampling signal for the second time, the differential controller 23 firstly filters the received signal according to the second time. The input current sampling signal predicts the waveform of the current input current Iin, and predicts the waveform of the filtered input current sampling signal received by the first time according to the signal stored in the register, and correspondingly according to the difference between the waveforms of the two Output current error signal, and finally, update the filtered input current sampling signal received in the second register, in other words, differential control 23 actually predicts the waveform of the current input current Iin according to the filtered input current sampling signal received, and predicts the previous time according to the filtered input current sampling signal received by the temporary storage device. Corresponding to the waveform of the input current Iin, and corresponding to the output current error signal according to the difference between the two waveforms, and subsequently updating the filtered input current sampling signal received in the register to the temporary register.

In the above embodiment, the differential controller 23 can have a compensation factor. When the differential controller 23 compares the waveform of the input current Iin with the waveform of the signal stored in the register, the comparison result is compared with the compensation factor of the constant value. A multiplication operation is performed to generate a current error signal. The compensation factor can be positive or negative. And the compensation factor can be preset by the phase difference between the input current Iin and the input voltage Vin.

The cosine multiplier 24 is electrically connected to the differential controller 23 for receiving the current error signal output by the differential controller 23, and adjusting the current error signal to output an adjustment signal, which is adjusted by the cosine multiplier 24. It can reduce the degree of change of the waveform of the current error signal at the peak value and increase the degree of change of the waveform of the current error signal at the zero point.

The first adder 25 is electrically connected to the cosine multiplier 24, which superimposes the received signals, that is, the feedforward signal D_ff and the adjustment signal output by the cosine multiplier 24 are superimposed to correspond to the output one phase compensation. The signal D_comp, wherein the feedforward signal D_ff is mainly used to adjust the output current Iout outputted by the power factor correction circuit 1 according to the input voltage Vin, thereby making the phase of the input current Iin coincide with the phase of the input voltage Vin, and before The feed signal D_ff is actually generated according to the input voltage Vin and the output voltage Vout, and the feedforward signal D_ff is estimated by the following equation (1): D_ff = 1 - (Vin / Vout) (1) In addition, when the differential controller 23 When the current error signal of zero is output, the adjustment signal output by the cosine multiplier 24 also corresponds to zero, so that the phase compensation signal D_comp output by the first adder 25 is substantially equal to the feedforward signal D_ff. On the other hand, when the differential controller 23 outputs a non-zero current error signal, the signal received by the first adder 25 includes the adjustment signal output by the cosine multiplier 24 and the feedforward signal D_ff, so the first adder The output phase compensation signal D_comp of 25 is actually equal to the superposition of the adjustment signal and the feedforward signal D_ff.

The second adder 26 is electrically connected to the first adder 25, which receives the phase compensation signal D_comp and a current control signal D_curr_ctrl output by the first adder 25, and the phase compensation signal D_comp and the current control signal D_curr_ctrl The superposition is performed to generate a pulse width modulation signal D_pwm. The current control signal D_curr_ctrl is correspondingly generated according to a comparison result of a current feedback value of the output current Iout and a preset current, and is used to make the output current Iout output by the power factor correction circuit 1 conform to the preset. The current is adjusted accordingly.

Please refer to FIG. 3 and cooperate with the first and second figures. FIG. 3 is a flow chart of the phase compensation method applicable to the power factor correction circuit shown in FIG. 1 in the preferred embodiment of the present invention. The phase compensation method of the preferred embodiment of the present invention comprises the following steps:

First, a corresponding input current sampling signal is generated according to the current input current Iin, and the input current sampling signal is filtered by the low pass filter 22 (as shown in step S301).

Then, the differential controller 23 is used to predict the waveform of the current input current Iin and the waveform of the previous input current Iin according to the currently received filtered input current sampling signal and the previously received filtered input current sampling signal, and compare and compare The difference between the two waveforms is to generate a current error signal based on the comparison result (as shown in step S302).

Next, the current error signal is adjusted using the cosine multiplier 24 to generate an adjustment signal (as shown in step S303).

Then, the feedforward signal D_ff generated according to the input voltage Vin and the output voltage Vout is superimposed with the adjustment signal by the first adder 25 to generate the phase compensation signal D_comp (as shown in step S304).

Finally, the second adder 26 superimposes the current control signal D_curr_ctrl and the phase compensation signal D_comp generated according to the comparison result of the current feedback value of the output current Iout with the preset current to generate the pulse width modulation signal D_pwm. The switching circuit 10 is controlled to adjust the phase of the output current Iout (step S305). In step S305, since the phase of the output current Iout can correspond to the phase of the input voltage Vin according to the adjustment of the pulse width modulation signal D_pwm, and the phase of the input current is the same as the phase of the output current, the output current Iout is adjusted. The phase of the input current Iin can be adjusted so that the phase of the input current Iin coincides with the phase of the input voltage Vin, and the setting of the low pass filter 22, the differential controller 23, and the cosine multiplier 24 is adopted. In the above steps S301~S303, the power factor correction circuit 1 of the present invention can effectively reduce the zero-crossover distortion and reduce the total harmonic distortion, thereby improving the efficiency of power transmission.

In step S302, if the differential controller 23 first receives the filtered input current sampling signal due to the power factor correction circuit 1 being activated, the differential controller 23 outputs a zero current error as described above. The signal, so in step S304, the phase compensation signal D_comp is substantially equal to the feedforward signal D_ff, and in step S305, the pulse width modulation signal D_pwm generated by the superimposed current control signal D_curr_ctrl and the phase compensation signal D_comp is only used to control The switching circuit 10 makes the phase of the input current Iin coincide with the phase of the input voltage Vin.

Please refer to FIG. 4 and FIG. 5 , wherein FIG. 4 is a waveform diagram of input current received by a conventional power factor correction circuit that does not use the phase compensation method of the present invention, and FIG. 5 is a diagram used in FIG. 3 of the present application. A waveform diagram of the input current received by the power factor correction circuit of the phase compensation method. As shown in FIG. 4, the input current received by the conventional power factor correction circuit is due to the bridge rectifier diode and the high voltage included in the power factor correction circuit when the input voltage is at zero, that is, time T1 and time T2. The frequency filter capacitor causes a phenomenon of pause and distortion, thereby generating zero-crossing distortion, resulting in an increase in total harmonic distortion. As shown in Fig. 5, the input current Iin received by the power factor correction circuit of the present case causes the pause and its distortion due to the use of the phase compensation method of the present case when the input voltage is at zero, that is, time T3 and time T4. The phenomenon is greatly reduced, so the distortion of zero crossover is significantly smaller. Therefore, comparing FIGS. 4 and 5, it can be seen that the input current after power factor correction using the conventional power factor correction circuit is received by the power factor correction circuit of the phase compensation method shown in FIG. 3 of the present invention. The zero-crossover distortion of the input current Iin is greatly reduced, effectively reducing the total harmonic distortion, thereby improving the efficiency of power transmission.

In summary, the phase compensation method applicable to the power factor correction circuit of the present invention predicts the current state by the differential controller according to the currently received filtered input current sampling signal and the previously received filtered input current sampling signal. The waveform of the input current and the waveform of the previous input current, and the current error signal is generated according to the difference of the waveform, and then the current error signal is adjusted by the cosine multiplier to generate an adjustment signal, and then the adjustment signal is superimposed with the feedforward signal to generate The phase compensation signal finally controls the switching circuit by the pulse width modulation signal generated by superimposing the phase compensation signal and the current control signal, so that not only the phase of the input current is matched with the phase of the input voltage, but also the effective reduction can be effectively reduced. Zero crossover distortion reduces total harmonic distortion, which in turn increases the efficiency of power transfer. In addition, the phase compensation method applicable to the power factor correction circuit of the present invention adjusts the current error signal by the cosine multiplier, reduces the degree of change of the waveform of the current error signal at the peak value, and increases the waveform of the current error signal at the zero point. The degree of change enables the power factor correction circuit using the phase compensation method of the present invention to increase the stability margin.

It should be noted that the above is only a preferred embodiment for the purpose of illustrating the present invention, and the present invention is not limited to the embodiments described above, and the scope of the present invention is determined by the scope of the patent application. Moreover, the case may be modified by those who are familiar with the technology, but it is not intended to be protected by the scope of the patent application.

1‧‧‧Power Factor Correction Circuit

10‧‧‧Switch circuit

20‧‧‧Control unit

22‧‧‧Low-pass filter

23‧‧‧Differential controller

24‧‧‧ Cosine Multiplier

25‧‧‧First Adder

26‧‧‧Second Adder

Iin‧‧‧ input current

Vin‧‧‧Input voltage

Iout‧‧‧Output current

Vout‧‧‧ output voltage

D_ff‧‧‧ feedforward signal

D_comp‧‧‧ phase compensation signal

D_curr_ctrl‧‧‧ current control signal

D_pwm‧‧‧ pulse width modulation signal

Steps of S301~S305‧‧‧ phase compensation method

T1, T2, T3, T4‧‧‧ time

FIG. 1 is a schematic diagram showing the circuit structure of a power factor correction circuit according to a preferred embodiment of the present invention.

Figure 2 is a schematic diagram showing the operation principle of the control unit shown in Figure 1.

Figure 3 is a flow chart of a phase compensation method applicable to the power factor correction circuit shown in Figure 1 of the preferred embodiment of the present invention.

Figure 4 is a waveform diagram of the input current received by a conventional power factor correction circuit that does not use the phase compensation method of the present invention.

Figure 5 is a waveform diagram of the input current received by the power factor correction circuit of the phase compensation shown in Fig. 3 of the present invention.

Claims (8)

A phase compensation method is applicable to a power factor correction circuit, which receives an input voltage and an input current, and includes a switch circuit and a control unit, and the switch circuit is controlled by the control unit. Turning on or off, the power factor correction circuit outputs an output voltage and an output current, the control unit includes a low pass filter, a differential controller and a cosine multiplier, wherein the low pass filter is continuously received Reflecting one of the input current input current sampling signals, the phase compensation method comprises the steps of: (a) filtering the input current sampling signal by using the low-pass filter; (b) using the differential controller to receive according to the current Filtering the input current sampling signal and the previously received filtered input current sampling signal, predicting the waveform of the current input current and the waveform of the previous input current, and according to the waveform of the current input current and the previous time The difference in the waveform of the input current produces a current error signal; (c) using the cosine multiplier The flow error signal is adjusted to generate an adjustment signal; (d) superimposing the adjustment signal with a feedforward signal to generate a phase compensation signal; (e) superimposing the phase compensation signal with a current control signal, To generate a pulse width modulation signal, and to control the operation of the switching circuit by using the pulse width modulation signal. The phase compensation method of claim 1, wherein the differential controller further comprises a register for storing the filtered input current sampling signal received by the differential controller. The phase compensation method according to claim 1, wherein in the step (d), the feedforward signal is generated according to the input voltage and the output voltage. The phase compensation method of claim 3, wherein the feedforward signal is equal to 1 - (Vin / Vout), wherein Vin is the input voltage, and Vout is the output voltage. The phase compensation method according to claim 1, wherein in the step (e), the current feedback value of the output current is compared with a preset current, and the current control signal is generated according to the comparison result. The phase compensation method according to claim 1, wherein the differential controller stores a compensation factor, and in the step (b), the waveform of the current input current and the waveform of the previous input current are used. The difference is multiplied by the compensation factor to produce the current error signal. The phase compensation method according to claim 6, wherein the compensation factor is a positive number or a negative number. The phase compensation method according to claim 6, wherein the compensation factor is preset by a phase difference between the input current and the input voltage.