JPH09103077A - Power-factor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-factor control circuit, in which a signal synchronized with input ACs is applied to the voltage and current of the input ACs and a power factor can be improved sufficiently, regarding the power-factor control circuit reducing the waveform distortion of the single-phase input ACs. SOLUTION: An input-signal detecting section 16 is composed of a synchronizing pulse signal generating circuit 17 generating a pulse signal synchronized with AC input voltage and a signal adder 18 adding the output pulse of the circuit 17 and an input-voltage waveform. This control circuit has a circuit 19 collating and comparing the output signal of the detecting section 16 and a load-side DC output-voltage detecting value and a comparison circuit 20 comparing an output from the circuit 19 and a single-phase AC input-current waveform, and a pulse-width control-signal generating section 21 is controlled by the output signal of the comparison circuit 20. The on-off of a main switch 7 are controlled by the pulse-width control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor control circuit for controlling so as to reduce the waveform distortion of a single-phase input AC.

[0002]

2. Description of the Related Art When a load including a reactance component is connected to an AC circuit, a phase difference occurs between an applied voltage and a flowing current, and the cosine value of the phase difference at that time is called "power factor". That is, the closer the power factor is to 100%, the less the phase difference is. When converting AC to DC to obtain a DC power supply, a smoothing circuit composed of a reactance and a capacitor is used near the rectifier circuit, so the input AC current waveform contains high-order harmonics. When connected to another circuit, the distortion current flowing in the other circuit, that is, a current with a poor power factor, may cause heat generation and burnout in the transformer, the capacitor, and the like in the other circuit. Therefore, a power factor control circuit is provided in the alternating current conversion circuit to prevent the occurrence of the trouble. Japanese Patent Laid-Open No. 4-140064 discloses an example of the circuit. FIG. 6 of the accompanying drawings is a diagram showing a configuration of a conventional power factor control circuit. In FIG. 6, 1 is an AC input source,
Reference numeral 2 is a DC load, 3 is a rectifier circuit, 4 is a diode, 5 is a capacitor, 6 is a reactance, and the diodes 4 to 6 represent a smoothing circuit. A main switch 7 is an output side terminal of the rectifier circuit 3. A current transformer 8 detects the current value of the AC input source 1. Reference numeral 9 is an output terminal of the capacitor 5, 10 is a first error amplification circuit, 11 is a multiplier, 12 is a second error amplification circuit, 13 is a waveform comparison circuit, 14 is a triangular wave generation circuit, and 15 is an output PWM signal. The AC input from the AC input source 1 is the rectifier circuit 3 and the backflow prevention diode 4
Then, it is converted to a direct current and is supplied to the load 2. The capacitor 5 is connected to both terminals 9 of the load 2, and the voltage is Eo. The voltage waveform of the AC input source 1 is applied to one terminal of the multiplier 11. The output of the first error amplification circuit 10, that is, the error value of the DC output voltage is applied to the other terminal of the multiplier 11. The output voltage detection value Eo of the DC circuit and the output voltage set value in the case of a predetermined load current are input to the first error amplification circuit 10, and the difference obtained by the calculation is output as an error.
In the multiplier 11, the error signal and the input voltage value are applied and calculated to obtain an input current target value for obtaining a predetermined output voltage, that is, a state in which there is no output voltage error.
Next, in the second error amplification circuit 12, the input current target value and the input current value are input and calculated. It can be said that the output after the calculation is a current waveform error. That is, if the input current waveform has a distortion, the distortion is included. The waveform comparison circuit 13 compares the triangular waveform signal from the triangular wave generation circuit 14 with the error signal. FIG. 7 is an example of a diagram showing input / output signal waveforms with respect to the waveform comparison circuit 13. In the waveform shown in FIG. 7A, Vc represents an output signal from the triangular wave generation circuit 14, and waveform Vi represents a current waveform error signal. The waveform shown in FIG. 7B is the output signal of the waveform comparison circuit 13. The output signal is a so-called PWM signal, which turns the main switch 7 on and off, and as a result controls the current envelope to be a sine wave. FIG. 7C shows a half-wave sine wave of a sine wave with a power factor of 100%.
For example, if the current waveform error signal is larger than the normal sine wave, the off time of the main switch 7 is extended, and conversely, if the error signal is small, the on time is extended. Therefore, since the positive and negative half waves of the AC waveform are controlled, the AC current from the AC input source 1 becomes a pure sine wave and the power factor is 10
0% is achieved.

[0003]

Although the above explanation is for the case where the power factor control is executed according to the theory, the actual operation is not so. In other words, it has been found experimentally that the AC waveform that should be controlled to improve the power factor should be targeted at the waveform near the point where the input voltage / input current crosses zero. Since the detection signal of 1 is of a small level, it is necessary to amplify the level until it is processed into a control signal. However, since the original signal is at a low level, it is difficult to distinguish it from noise, and the desired signal is not always obtained by amplification. Further, in FIG. 7A, the signal Vi
Looking at the magnitude relationship between Vc and Vc, the point M should be Vc = Vi = 0, but Vi does not always become zero like Vc.
When Vi has a positive value due to noise or the like at the point M, the pulse shown in FIG. 7B is generated, so that the main switch is abnormally opened / closed and an accurate sine wave is obtained. Is difficult. Therefore, the distortion of the input current could not be removed. Therefore, it is desirable to provide a power factor control circuit capable of sufficiently improving the power factor by applying a load signal synchronized with the input alternating current to the voltage of the input alternating current in order to improve the conventional drawbacks.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a power factor control circuit which solves the above-mentioned problems, and collates and compares a single-phase AC input voltage detection value and a load-side DC output voltage detection value. The comparison and comparison circuit, a comparison circuit for comparing the output of the comparison and comparison circuit with a single-phase AC input current waveform, and a pulse width control signal generator for obtaining a signal for controlling the pulse width by the signal obtained by the comparison circuit. In the power factor control circuit for a single-phase alternating current input current, which controls the main switch that turns on and off between the output voltage terminals of the alternating current input rectifier circuit by the output of the signal generator, the input signal is further input to the power factor control circuit. A detection unit is provided, and the input signal detection unit includes a synchronization pulse signal generation circuit that generates a pulse signal synchronized with an AC input voltage, and a signal addition unit that adds an output pulse of the synchronization pulse signal generation circuit and an input voltage waveform. Constituted by a circuit, characterized in that the signal adding circuit output signal and the single-phase input voltage detection value. In this case, it is preferable that the synchronizing pulse generating circuit is composed of a signal comparing circuit, and one signal of the signal comparing circuit is an AC input voltage and the other is a zero V signal.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of the power factor control circuit of the present invention. In FIG. 1, 1 is an AC power supply, 2 is a load, 7 is a main switch, 16 is an input signal detection unit, 17 is a synchronous pulse generation circuit, 18 is a signal addition circuit, 19 is a collation comparison circuit, 20 is a comparison circuit, 21 Is a pulse width control signal generator, and 22 is a rectifier circuit. Thus, the configuration of the power factor control circuit of the present invention will be described with reference numerals, a collation comparison circuit 19 that collates and compares a single-phase AC input voltage detection value and a load-side DC output voltage detection value, and the collation comparison circuit 19. The comparison circuit 20 is provided with a comparison circuit 20 for comparing the output of the comparison circuit with a single-phase AC input current waveform, and a pulse width control signal generator 21 for obtaining a signal for controlling the pulse width by the signal obtained by the comparison circuit 20. In a power factor control circuit for a single-phase alternating current input current, in which a main switch 7 for turning on / off between output voltage terminals of an alternating current input current circuit is controlled by an output of a generator 21, a further input signal is detected by the power factor control circuit. A section 16 is provided, and the input signal detection section 16 generates a sync pulse signal generation circuit 17 for generating a pulse signal synchronized with an AC input voltage, an output pulse of the sync pulse signal generation circuit 17 and an input voltage waveform. Constituted by the signal adding circuit 18 to calculate, constitutes the signal adder circuit 18 output signal by said single-phase input voltage detection value.

In the present invention, for power factor control, the synchronous pulse signal generating circuit 17 generates a pulse synchronized with the input AC, that is, a pulse synchronized with the frequency of the AC power supply. Since the signal has a magnitude corresponding to the pulse amplitude when the input voltage is 0 V, when the pulse signal and the input voltage are added by the signal adding circuit 18, the AC input of the sine wave expands in both positive and negative directions. It becomes the attached shape. Then, the signal is multiplied by the error of the output voltage in the comparison and comparison circuit 19. The output of the verification and comparison circuit 19 is the target value for the input current required for the load connected at that time. Therefore, by comparing this target value and the input current waveform in the comparison circuit 20, the error between the target value and the actual value is obtained. According to the present invention, the pulse width control signal generator 21
At get the PWM signal. If the switch 7 is turned on / off by the PWM signal, the power factor of the current flowing into the rectifier circuit 22 can be regarded as 100%.

FIG. 2 is a concrete configuration diagram of the input signal detecting section 16 shown in FIG. 1 as a preferred embodiment of the invention described above. In FIG. 2, reference numeral 31 denotes an AC input voltage application terminal S.
Is shown. Reference numeral 32 denotes a voltage comparator, which is an example of a synchronizing pulse signal generating circuit. Reference numeral 33 indicates a voltage adding circuit. The signal from the application terminal of the AC input voltage is applied to one terminal of the voltage comparator 32, and the reference potential of zero V (0V) is applied to the other terminal. Obtaining a zero V reference potential is
For example, it can be obtained by connecting to the ground side terminal of the battery terminal to obtain its potential, or by connecting one line of the secondary side output of the power supply transformer to zero V of the illustrated control line. Voltage comparator 31
Generates a pulse output at the output terminal at the moment when the potentials of the two terminals become the same, a pulse is generated at the output at the moment when the AC input voltage crosses zero V, and the input voltage changes from a high half-wave value. It becomes a positive pulse until it drops again and crosses zero V. Then, a negative pulse is generated at the moment when the voltage crosses zero V.
The width of this negative pulse is until the next crossing of 0V. This pulse waveform is shown as "square wave P" in FIG. The signal at one terminal of the voltage adding circuit 33 is the pulse signal P, and the signal at the other terminal is the input voltage waveform shown at the terminal 31. To the output terminal T of the voltage adding circuit 33, a waveform in which a sine wave-shaped intermediate portion as shown by a solid line on the right side thereof is bulky up and down is output. The dotted line signal shown in contact with the waveform is the input voltage waveform. In the voltage adding circuit 33, since the pulse signal P as a load signal synchronized with the input AC is added to the input voltage waveform, the voltage adding circuit 3
The output signal of 3 has a special waveform.

The output terminal T of the voltage adding circuit 33 is connected to the input terminal of the AC input source of the circuit corresponding to the conventional power factor control circuit shown in FIG. That is, it becomes one input signal to the multiplier 11 in FIG. The other input signal to the multiplier 11 is the output voltage error value. Therefore multiplier 1
The input current target value for making the output U of 1 have no output voltage error is obtained.

FIG. 4 is a diagram showing the waveform of each part in the circuit having the configuration shown in FIGS. 2 and 3. FIG. 4A shows an input voltage waveform at the terminal S in FIG. FIG. 4B shows the waveform at the output terminal of the voltage comparator 32. FIG. 4C shows the waveform at the output terminal T of the voltage adding circuit 33. FIG.
The waveform shown in (c) is added with the pulse signal P in order to make the rising edge of the input voltage detection waveform steep in the input signal detection unit 16 judging from its shape. FIG.4 (d) shows the waveform which shows the said input voltage target value. Next, in the second error signal amplifier 12 shown in FIG. 3, the signal of the input waveform is input from the terminal W and the calculation is performed. The output Vy of the second error signal amplifier 12 includes the error signal included in the input current waveform. (See FIG. 4 (f)). Therefore, the waveform comparison circuit 13 compares the output signal Vy with the output Vc of the triangular wave 14 to obtain the PWM signal 15Vz.

Compared to FIG. 7, the PWM signal 15Vz shown in FIG. 5 has a small difference in width between pulse waveforms. As shown in FIG. 3, when the output signal Vc of the triangular wave generating circuit 14 and the output signal Vy of the second error signal amplifier 12 are compared in the waveform comparison circuit 13, the error signal included in the signal Vy is surely detected. This is because it is taken out. Therefore, if the switch 7 shown in FIG. 1 is controlled by the PWM signal 15, the effect of improving the power factor is greater than that in the conventional case.

[0011]

As described above, according to the above configuration of the present invention,
To improve the power factor of the single-phase AC input current, obtain the input voltage error-free target value.The signal applied to the circuit that multiplies with the output line pressure on the load side, that is, the signal with a sharp rise in the input voltage detection waveform Since the pulse synchronized with the frequency of the alternating current is used, the on / off signal of the switch obtained by calculation based on the signal has a sufficiently large effect for tampering with the power factor.

[Detailed Description of Drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a specific configuration diagram of the input signal detection unit shown in FIG.

FIG. 3 is a circuit diagram when the present invention is applied to a conventional power factor control circuit.

FIG. 4 is a diagram showing the waveform of each part in the circuit having the configuration shown in FIGS. 2 and 3.

FIG. 5 is a waveform comparison signal and P in the embodiment of the present invention.
It is a figure which shows a WM signal.

FIG. 6 is a diagram showing a configuration of a conventional power factor control circuit.

7 is a diagram showing input / output signal waveforms for the waveform comparison circuit shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 AC input source 2 Load 7 Main switch 16 Input signal detection unit 17 Synchronous pulse signal generation circuit 18 Signal addition circuit 19 Collation comparison circuit 20 Comparison circuit 21 Pulse width control signal generation unit 22 Rectification circuit

Claims (2)

[Claims] 1. A collation comparison circuit that collates and compares a single-phase AC input voltage detection value and a load-side DC output voltage detection value; and a comparison circuit that compares the collation comparison circuit output with a single-phase AC input current waveform. A pulse width control signal generator for obtaining a signal for controlling the pulse width by the signal obtained by the comparison circuit,
In a power factor control circuit for a single-phase AC input current, wherein a main switch that turns on and off between output voltage terminals of an AC input rectifier circuit is controlled by the output of the signal generation unit, the power factor control circuit further includes an input signal detection unit. The input signal detection unit is provided with a synchronous pulse signal generating circuit for generating a pulse signal synchronized with an AC input voltage, and a signal adding circuit for adding an output pulse of the synchronous pulse signal generating circuit and an input voltage waveform. A power factor control circuit, wherein the output signal of the signal addition circuit is the detected value of the single-phase input voltage. 2. The synchronizing pulse generating circuit according to claim 1,
A power factor control circuit comprising a signal comparison circuit, wherein one signal of the signal comparison circuit is an AC input voltage and the other is a zero V signal.