JP2018196251A - electric circuit - Google Patents

Abstract

An output voltage ripple of an output capacitor of a power factor correction circuit is suppressed.
A step-up conversion means for step-up converting an input AC voltage into a DC voltage, a step-down conversion means for supplying a desired power to a load with the DC voltage as an input, and a current ripple generation means for generating a ripple signal. 32 and current ripple superimposing means 34 for generating and outputting a target peak current signal in which the ripple signal is superimposed on the DC smoothed target peak current signal, and smoothing of the step-down conversion means 104 based on the target peak current signal Control the current through the coil.
[Selection] Figure 1

Description

  The present invention relates to an electric circuit including a power factor correction circuit.

  Disclosed is a converter comprising a front-stage converter having a first switching circuit, a capacitor for smoothing the current output from the converter, and a rear-stage converter having a second switching circuit for receiving the smoothed current input. ing. The ripple current can be reduced by switching control so that the end point of the output period in which current is output from the first switching circuit and the start point of the input period in which current is input to the second switching circuit have a time difference. (Patent Document 1).

Japanese Patent Laid-Open No. 2006-149897

  As in Patent Document 1, it is possible to minimize the current flowing into and out of the output capacitor by overlapping the period in which the current flows into the output capacitor of the power factor correction circuit and the period in which the current flows out from the output capacitor. It is. However, a ripple reduction that can cancel out a ripple current having a frequency component twice the frequency of the input voltage has not been realized. Therefore, it is difficult to greatly reduce the capacity of the output capacitor, and it is difficult to greatly reduce the size of the device.

  One aspect of the present invention includes a power factor correction circuit that boosts and converts an input AC voltage into a DC voltage, a converter circuit that supplies the DC voltage as input and supplies desired power, and a ripple that generates a ripple signal. Signal generating means; and current ripple superimposing means for generating and outputting a target peak current signal obtained by superimposing the ripple signal on a DC smooth target peak current signal, and the converter circuit based on the target peak current signal It is an electric circuit characterized by controlling the current flowing through the smoothing coil.

  Here, the power factor correction circuit includes a rectifier circuit that rectifies the AC voltage, and the ripple signal generation unit outputs the ripple signal having a frequency included in an AC component of a rectified current output from the rectifier circuit. It is preferable to generate.

  Further, it is preferable that the ripple signal generating means generates the ripple signal having a frequency twice as high as the frequency of the AC voltage.

  Further, it is preferable that the ripple signal generating means generates the ripple signal based on a waveform obtained by differentiating the output voltage of the power factor correction circuit.

  According to the present invention, ripple of the output voltage of the output capacitor of the power factor correction circuit can be suppressed. Therefore, the capacity of the output capacitor can be reduced, and the device can be miniaturized.

It is a functional block diagram which shows the structure of the electric circuit in 1st Embodiment. It is a figure which shows the structure of the electric circuit in 1st Embodiment. It is a figure explaining the effect | action of the conventional electric circuit. It is a figure explaining the effect | action of the electric circuit in 1st Embodiment. It is a functional block diagram which shows the structure of the electric circuit in 2nd Embodiment. It is a figure which shows the structure of the electric circuit in 2nd Embodiment. It is a figure explaining the effect | action of the conventional electric circuit. It is a figure explaining the effect | action of the electric circuit in 2nd Embodiment.

[First Embodiment]
As shown in the functional block diagram of FIG. 1, the electric circuit 100 according to the first embodiment includes a step-up conversion unit 102, a step-down conversion unit 104, an input voltage detection unit 10, an input current detection unit 12, and an input current command value generation. Means 14, current error detection means 16, switch control means 18, output voltage detection means 20, voltage error detection means 22, voltage compensator 24, peak current detection means 26, output voltage detection means 28, target peak current generation means 30, The current ripple generating unit 32, the current ripple superimposing unit 34, the current error detecting unit 36, the current command value generating unit 38, and the switch control unit 40 are configured.

  The electric circuit 100 can be configured as a specific electric circuit as shown in FIG. In FIG. 2, the components corresponding to the functional blocks in FIG.

The step-up converter 102 includes a rectifier circuit 102 a and functions as a bridgeless power factor correction circuit (PFC circuit: Power Factor Correction) in the electric circuit 100. The step-up converter 102 includes a rectifier circuit 102a connected to an AC power source and an output capacitor C _VH provided on the output side.

  The step-down converter 104 is a converter circuit including a configuration in which direct current-direct current converters (DC / DC converters) are connected in cascade, receives the output voltage from the step-up converter 102, converts the voltage, and outputs the converted voltage. In this embodiment, as an example, a configuration including a configuration in which phase-shifted full-bridge DC / DC converters are cascade-connected is shown.

  First, the control of the boost converter 102 will be described. The step-up converter 102 includes an input voltage detector 10, an input current detector 12, an input current command value generator 14, a current error detector 16, a switch controller 18, an output voltage detector 20, a voltage error detector 22, and a voltage. It is controlled by the compensator 24.

The input voltage detection means 10 detects and outputs the input voltage _vac of the boost conversion means 102. The input voltage detection means 10 can be configured including a voltage sensor. The detected input voltage v _ac is analog / digital converted and input to the input current command value generating means 14 and the current ripple generating means 32.

Here, assuming that the angular frequency ω _{ac is} the effective value v _ac ^(RMS) , the waveform of the input voltage v _ac is expressed by Equation (1).

The input current detection unit 12 detects and outputs the input current i _ac of the boost conversion unit 102. The input current detection means 12 can be configured to include a current sensor. The detected input current i _ac is analog / digital converted and input to the input current command value generation means 14.

The input current command value generation means 14 generates and outputs a target input current command value i _ac ^(REF) based on the input voltage v _ac detected by the input voltage detection means 10. Input current command value i _ac ^(REF), as shown in Equation (2) and Equation (3), the voltage value v _c input from the voltage compensator 24 to be described later as the input voltage effective value v _ac ^(RMS) And is a signal that periodically changes at an angular frequency ω _ac with an amplitude I _ac ^(REF) . The input current command value i _ac ^(REF) is input to the current error detection means 16.

The current error detection unit 16 obtains a difference value between the target input current command value i _ac ^(REF) generated by the input current command value generation unit 14 and the actual input current i _ac input from the input current detection unit 12. Output to the switch control means 18. The switch control means 18 turns on the switching element of the rectifier circuit 102a of the boost conversion means 102 based on the difference value between the target input current command value i _ac ^(REF) obtained by the current error detection means 16 and the input current i _ac. The time ratio of / off is obtained, and the timing for turning on / off the switching element is controlled according to the time ratio.

The target input current command value i _ac ^(REF) is updated at every switching timing of the boost converter 102. Here, the input voltage effective value v _ac ^(RMS) is preferably calculated and updated using the waveform data of the immediately preceding half cycle every time the input voltage v _ac crosses zero. As a result, the amplitude I _ac ^(REF) in Equation (2) is updated every time the input voltage v _ac crosses zero.

The output voltage detection means 20 detects and outputs the terminal voltage (output capacitor voltage) v _vh of the output capacitor C _VH of the boost conversion means 102. The output voltage detection means 20 includes a voltage sensor. The detected output capacitor voltage v _vh is analog / digital converted and input to the voltage error detecting means 22.

The voltage error detection unit 22 calculates a difference value between the output capacitor voltage v _vh input from the output voltage detection unit 20 and the reference voltage V _vh ^(REF), and outputs the difference value to the voltage compensator 24.

The voltage compensator 24 receives the difference value between the output capacitor voltage v _vh and the reference voltage V _vh ^(REF) from the voltage error detection means 22 and based on the proportional gain, integral gain, etc. required for the boost conversion means 102. Voltage compensated voltage value Vc is calculated and output to input current command value generation means 14.

In this way, the output capacitor voltage v _vh of the boost converter 102 is fed back to the input current command value generator 14, and the target input current command value i _ac ^(REF) is obtained from the input voltage v _ac and the input current i _ac. Based on the target input current command value i _ac ^(REF) , switching control of the boost converter 102 is performed. The output capacitor voltage v _vh of the step-up conversion unit 102 is input to the input terminal of the step-down conversion unit 104. The step-down converter 104 performs DC / DC conversion on the output capacitor voltage v _vh and outputs it as an output voltage v _pv and an output current i _pv .

  Next, the control of the step-down converter 104 will be described. The step-down converter 104 includes a peak current detector 26, an output voltage detector 28, a target peak current generator 30, a current ripple generator 32, a current ripple superimposing unit 34, a current error detector 36, a current command value generator 38, and It is controlled by the switch control means 40.

The peak current detector 26 detects the current i _T1 on the transformer primary side of the step-down converter 104. The peak current detection means 26 includes a current sensor. The current i _T1 is analog / digital converted. The peak current detection means 26 further estimates and outputs the peak current i _Pk of the smoothing coil from the current i _T1 on the transformer primary side. The peak current i _Pk is input to the target peak current generation means 30 and the current error detection means 36.

The output voltage detection unit 28 detects and outputs the output voltage v _pv of the step-down conversion unit 104. The output voltage detection means 28 can be configured to include a voltage sensor. The detected output voltage v _pv is analog / digital converted and input to the target peak current generating means 30.

The target peak current generator 30 determines the peak current command value I _LP ^(DC) so that the output voltage v _pv from the step-down converter 104 becomes a desired value, and outputs it to the current ripple superimposing unit 34.

Current ripple generation unit 32 receives the input voltage v _ac step-up converter 102 from the input voltage detection unit 10 generates a current ripple i _LP ^(RIP). The current ripple i _LP ^(RIP) is expressed as 2 in the peak current amplitude I _LP ^(RIP) and the angular frequency ω _ac of the input voltage v _ac allowed in the circuit configuration of the step-down converter 104, as shown in Equation (4). The signal periodically changes at the double angular frequency 2ω _ac . The calculated current ripple i _LP ^(RIP) is input to the current ripple superimposing means 34.

The current ripple superimposing means 34, as shown in the equation (5), includes the peak current command value I _LP ^(DC) input from the target peak current generating means 30 and the current ripple i _LP ^{( RIP)} and the added value i _Pk ^(REF) are calculated and output to the current error detecting means 36.

The current error detection means 36 has a difference value between the peak current command value I _LP ^(DC) input from the current ripple superimposing means 34 and the current ripple i _LP ^(RIP) and the peak current i input from the peak current detection means 26. A difference value from _Pk is calculated as an output signal and output to the current command value generating means 38.

  The current command value generation means 38 receives the output signal of the current error detection means 36, and outputs a signal whose current has been compensated based on the proportional gain and integral gain required for the step-down conversion means 104 with respect to the output signal. It is generated and output to the switch control means 40.

  The switch control means 40 receives the output signal of the current command value generation means 38, generates a phase shift pulse, and controls on / off of switching elements in the inverter included in the step-down conversion means 104.

In the electric circuit 100 according to the present embodiment, the current ripple generating means 32 and the current ripple superimposing means 34 are provided, the current ripple i _LP ^(RIP) is estimated, and the step-down conversion means in consideration of the current ripple i _LP ^(RIP). By setting a target value for controlling the peak current of the smoothing coil 104, the ripple voltage of the output voltage V _vh of the boost converter 102 can be reduced. The reduction amount of the ripple voltage can be adjusted by changing the amplitude of the current ripple i _LP ^(RIP) .

Here, the reason why the ripple voltage of the output voltage V _vh of the step-down converter 104 can be reduced by superimposing the current ripple i _LP ^(RIP) is as follows.

In the step-up converter 102, the conducting diode is switched depending on the polarity of the waveform of the input voltage _vac , so that the current supplied from the input power source at point A in FIG. It is expressed by Equation (6).

The voltage ripple of the step-up conversion means 102 is generated by integrating the difference current between the input current represented by the second term of the equation (6) and the current output to the step-down conversion means 104 by the output capacitor. That is, the current ripple i _LP ^(RIP) expressed by the equation (4) changes at the same frequency and phase as the second term of the equation (6), and thus acts to reduce the current ripple of this difference. As a result, the voltage ripple of the boost converter 102 is reduced.

FIG. 3 shows the configuration of the conventional electric circuit, that is, the current ripple generating means 32 and the current ripple superimposing means 34 are not provided, and the peak current command value I _LP ^(DC) from the target peak current generating means 30 is determined as the current error detecting means 36. The result of having simulated the input and output in the structure which inputs directly to the is shown. FIG. 4 shows the result of simulating the input and output in the electric circuit 100 in the present embodiment.

As shown in FIG. 3, in the conventional electric circuit, the output capacitor voltage V _vh of the step-up conversion means has a ripple of about ± 9 V with respect to the DC average value, whereas the electric circuit 100 of the present embodiment. When the current ripple i _LP ^(RIP) of about ± 6 A is superimposed on the target peak current command value I _LP ^(DC) , the ripple of the output capacitor voltage V _vh is reduced to about ± 4 V.

[Second Embodiment]
As shown in the functional block diagram of FIG. 5, the electric circuit 200 according to the second embodiment is similar to the electric circuit 100 according to the first embodiment in the step-up conversion unit 102, the step-down conversion unit 104, and the input voltage detection. Means 10, input current detection means 12, input current command value generation means 14, current error detection means 16, switch control means 18, output voltage detection means 20, voltage error detection means 22, voltage compensator 24, peak current detection means 26 , Output voltage detecting means 28, target peak current generating means 30, current ripple generating means 42, current ripple superimposing means 44, current error detecting means 36, current command value generating means 38 and switch control means 40.

However, in the first embodiment, the input voltage v _ac is input to the current ripple generating means 32, but in this embodiment, the output capacitor voltage v _vh of the boost conversion means 102 is applied to the current ripple superimposing means 44. It differs in that it is input. Therefore, in the following description, only a configuration different from the electric circuit 100 of the first embodiment will be described.

  As shown in FIG. 6, the electric circuit 200 can be configured as a specific electric circuit. In FIG. 6, the components corresponding to the functional blocks in FIG.

The current ripple generation means 42 generates a current ripple i _LP ^(RIP) that changes in the same manner as the differential waveform of the output capacitor voltage v _vh of the step-down conversion means 104 as shown in Equation (7). The differential waveform can be obtained from the time difference between values sampled in a sufficiently short time (for example, the control cycle of the voltage compensator 24) with respect to the cycle of the input voltage _vac .

In electric circuit 200 in the present embodiment, it is considered that current ripple i _LP ^(RIP) can be grasped by differentiating output capacitor voltage v _vh .

In the current ripple superimposing means 44, as shown in the equation (8), the peak current command value I _LP ^(DC) input from the target peak current generating means 30 and the current ripple i _LP ^{( RIP)} and the added value i _Pk ^(REF) are calculated and output to the current error detecting means 36.

In the electric circuit 200 in the present embodiment, the current ripple generating means 42 and the current ripple superimposing means 44 are provided, the current ripple i _LP ^(RIP) is estimated, and the step-down conversion means in consideration of the current ripple i _LP ^(RIP). By setting a target value for controlling the peak current of the smoothing coil 104, the ripple voltage of the output voltage V _vh of the boost converter 102 can be reduced. The reduction amount of the ripple voltage can be adjusted by changing the amplitude of the current ripple i _LP ^(RIP) .

FIG. 7 shows the configuration of the conventional electric circuit, that is, the current ripple generating means 42 and the current ripple superimposing means 44 are not provided, and the peak current command value I _LP ^(DC) from the target peak current generating means 30 is determined as the current error detecting means 36. The result of having simulated the input and output in the structure which inputs directly to the is shown. FIG. 8 shows the result of simulating the input and output in the electric circuit 200 in the present embodiment.

As shown in FIG. 7, in the conventional electric circuit, the output capacitor voltage V _H of the step-down converter has a ripple of about ± 9 V with respect to the DC average value, whereas the electric circuit 200 of the present embodiment. When the current ripple i _LP ^(RIP) of about ± 5 A is superimposed on the target peak current command value I _LP ^(DC) , the ripple of the voltage output capacitor voltage V _H is reduced to about ± 6 V.

  10 input voltage detection means, 12 input current detection means, 14 input current command value generation means, 16 current error detection means, 18 switch control means, 20 output voltage detection means, 22 voltage error detection means, 24 voltage compensator, 26 peak Current detection means, 28 Output voltage detection means, 30 Target peak current generation means, 32 Current ripple generation means, 34 Current ripple superimposition means, 36 Current error detection means, 38 Current command value generation means, 40 Switch control means, 42 Current ripple Generating means, 44 current ripple superimposing means, 100 electric circuit, 102 step-up conversion means, 102a rectifier circuit, 104 step-down conversion means, 200 electric circuit.

Claims (4)

A power factor correction circuit that boosts and converts an input AC voltage into a DC voltage;
A converter circuit for supplying desired power to a load using the DC voltage as an input;
Ripple signal generating means for generating a ripple signal;
Current ripple superimposing means for generating and outputting a target peak current signal in which the ripple signal is superimposed on a DC smooth target peak current signal;
With
An electric circuit for controlling a current flowing through a smoothing coil of the converter circuit based on the target peak current signal. The electrical circuit according to claim 1,
The power factor correction circuit includes a rectifier circuit that rectifies the AC voltage,
The ripple signal generating means generates the ripple signal having a frequency included in an AC component of a rectified current output from the rectifier circuit. The electrical circuit according to claim 1,
The electric circuit characterized in that the ripple signal generating means generates the ripple signal having a frequency twice as high as the frequency of the AC voltage. The electrical circuit according to claim 1,
The electric circuit characterized in that the ripple signal generating means generates the ripple signal based on a waveform obtained by differentiating the output voltage of the power factor correction circuit.