JPH08107677A - Control circuit of ac-input power-supply unit - Google Patents

Abstract

PURPOSE: To reduce the AC-frequency ripple generated in the output voltage of an AC-input power-supply unit while maintaining its stability. CONSTITUTION: In a control circuit of an AC-input power-supply unit, during a term wherein its input power is larger than its output power, a part of its input power is charged in a capacitor 3 via a second switching part 4, and during the term other than this term, a part of its output power is discharged from the capacitor 3 into its output via a first switching part 2, and thereby, the electric energy fed to its output is made constant. In this control circuit, a plurality of error amplifiers 102, 104, 108, 110, 120 each of which inputs an output voltage and a reference voltage and has each differnt feedback gain and each different reference voltage from others are provided in parallel. Further, the outputs of these amplifiers are inputted to the first and second switching parts 2, 4, and thereby, the AC-frequency ripple of the output voltage of the power-supply unit is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit of an AC input power supply device which realizes AC frequency ripple reduction of output.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional configuration example of a control circuit of an AC input power supply device. As shown in FIG. 4, the AC input power supply device in the conventional example includes a rectifier circuit 8 including a diode connected to the AC input source 1, an inductor 21 connected to the rectifier circuit 8, and the inductor 2.
1 is connected to the inductor 21 via a diode 9 and an energy storage capacitor 3, and a switch element 4 connected to the capacitor 3.
A second switching section 4 having two input transformers, two input windings 51 and 52 respectively connected to the outputs of the two switching sections 2 and 4, and a two-input transformer 5 having the output winding 53; A rectifying / smoothing circuit 6 including a diode and an output capacitor connected to the winding 53, an output terminal 7 connected to the rectifying / smoothing circuit 6, and a control circuit 1.
00 and 00.

Further, the control circuit 100 in the conventional example.
Is a first error amplifier 102 that receives the voltage of the capacitor 3 and the first reference voltage 101, and the output of the first error amplifier 102 and the voltage of the AC input source 1 or a sinusoidal waveform synchronized with the voltage. A multiplier 103 that receives the absolute value of the oscillation waveform as an input, and the output of this multiplier 103 and the inductor 2
The second error amplifier 104, which receives the detection signal of the current flowing in 1, and the first comparator 106, which receives the output of the second error amplifier 104 and the sawtooth wave output from the sawtooth wave oscillator 105. And a third error amplifier 108 that receives the voltage of the output terminal 7 of the AC input power supply device and the second reference voltage 107, the output of the third error amplifier 108, and the sawtooth wave from the sawtooth wave oscillator 105. Second comparator 1 with and as inputs
09, the voltage of the output terminal 7 of the AC input power supply device and the second reference voltage 107 are input to the fourth error amplifier 110.
And the output of the fourth error amplifier 110 and the sawtooth oscillator 1
A third comparator 111 which receives the sawtooth wave from
The output of the three comparators 106, 109, 111 is used as an input, and a logic circuit 112 made up of OR, NOT, AND, etc., and the first drive circuit 113 for driving the switch elements 22 and 23 with the output of this logic circuit 112 as an input. And a second drive circuit 114 which receives the output of the logic circuit 112 and drives the switch element 42.

Here, the first error amplifier 102 outputs an error voltage with respect to the first reference voltage 101 which does not transmit a ripple having a frequency twice that of the AC input source 1 generated in the voltage of the capacitor 3. . The second error amplifier 104 outputs an error voltage between the averaged switching ripple of the input current generated due to the high frequency switching performed in the first switching unit 2 and the reference current waveform output by the multiplier 103. To do. In addition, the first comparator 106
Is a sine wave-shaped waveform similar to the voltage of the AC input source 1 or a waveform similar to this, and performs control such that the average value of the voltage of the capacitor 3 in the AC cycle is constant. It outputs a pulse signal that controls the ON period. The second comparator 109 outputs a pulse signal during the OFF period of the switch element 23 in order to control the charging energy of the capacitor 3 so that the voltage of the output terminal 7 becomes equal to the second reference voltage 107. The third comparator 111 outputs a pulse signal during the ON period of the switch element 42 in order to control the discharge energy from the capacitor 3 so that the voltage of the output terminal 7 becomes equal to the second reference voltage 107.

In this AC input power supply device, the capacitor 3 is charged with a part of the input power during the period when the input power is higher than the output power, that is, during the charging mode, and the input power is lower than the output power, that is, In the discharge mode, a part of the output power is supplemented by the discharge from the capacitor 3.

FIG. 5 shows switching elements 22, 23,
42 shows the gate drive voltage waveforms V _{G1 to} V _G3 of 42. In the charging mode, energy is stored in the inductor 21 during the ON period of the switch element 22, the energy storage capacitor 3 is charged during the simultaneous OFF period of the switch elements 22 and 23, and the energy is stored in the inductor during the ON period of the switch element 23 via the transformer. Supply power to the output. Also, the reset of the transformer 5 is
After the switch element 23 is turned off, the body diode of the switch element 42 becomes conductive, and energy is released from the input winding 52 to the capacitor 3.
On the other hand, in the discharge mode, the switch element 42 is turned on while the switch element 22 is on, energy is stored in the transformer 5, and power is simultaneously supplied to the output while the switch element 23 is on.

FIG. 6 is a diagram schematically showing the waveform of each part related to the output voltage control in the discharge mode of this conventional example. In the control circuit of the present AC input power supply device, it is necessary to greatly change the duty ratio of the switch element 42 in the discharge mode to control the output voltage, and in order to reduce the AC frequency ripple generated in the voltage of the output terminal 7. Requires a high gain in the fourth error amplifier 110. As shown in FIG. 6, when the exciting current of the transformer 5 continuously flows in the discharge mode, the feedback system of the output voltage becomes unstable due to the high feedback gain, and the voltage at the output terminal 7 oscillates. May occur.

[0008]

In this conventional example, since the output voltage is controlled by largely changing the duty ratio of the switch element, the AC frequency ripple generated in the output voltage becomes large in order to maintain the stability. There is a problem that unstable oscillation occurs in order to reduce this ripple.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a control circuit for reducing the AC frequency ripple generated in the output voltage while maintaining the stability.

[0010]

A control circuit for an AC input power supply device according to the present invention comprises an energy storage element and a first AC input source connected to the energy storage element.
And a second switching section that receives the energy storage element as an input, and controls the charging energy from the AC input source to the energy storage element so that the output voltage is detected and is constant. Controlling the input power to detect the voltage or current of the energy storage element and to keep the average value in this AC cycle constant.
The discharge energy from the energy storage element to the output is controlled by the switching element in the switching section of the second output voltage so that the output voltage is detected and becomes constant.
AC power source for controlling the output voltage and the voltage or current of the energy storage element by combining the output of the first switching section and the output of the second switching section In the control circuit of the apparatus, the output voltage and the reference voltage are input, a plurality of error amplifiers having different feedback gains and different reference voltages are provided, and the outputs of the plurality of error amplifiers are connected in parallel, It is input to the second switching unit.

[0011]

In the control circuit of the AC input power supply device according to the present invention, error amplifiers for a plurality of output power supplies are provided in parallel,
By setting the output voltage feedback gain low only in the range where it is likely to become unstable, it is possible to reduce the AC frequency ripple of the output voltage while maintaining the stability of the control system.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention. As shown in FIG. 1, the main circuit configuration of the AC input power supply device in this embodiment is the same as that of the conventional example shown in FIG. Further, as shown in FIG. 1, in the control circuit 100A of the present embodiment, the configuration of the error amplifier for generating a signal for controlling the on / off of the switch element 42 is different from that of the conventional example. That is, the fourth error amplifier 110 that receives the voltage of the output terminal 7 of the AC input power supply device and the third reference voltage 130, the voltage of the output terminal 7 of the AC input power supply device, and the fourth reference voltage 140. Fifth input
Error amplifier 120 and the fourth and fifth error amplifiers 11
It is characterized by having first and second diodes 150 and 160 connected to the outputs of 0 and 120, respectively.

In the control circuit 100A of this embodiment,
The fourth error amplifier 110 has a high gain and the fifth error amplifier 120 has a low gain. FIG. 2 is a diagram showing the characteristics of the fourth and fifth error amplifiers 110 and 120 and the third comparator 111. As shown in FIG. 2, in the range in which a narrow pulse signal in which the exciting current of the transformer 5 is discontinuous is output during the period in which the capacitor 3 is being discharged, the output signal of the fourth error amplifier 110 has a higher feedback gain. The output voltage is controlled by, while the voltage of the output terminal 7 is controlled by the output signal of the fifth error amplifier 120 with a low feedback gain in the range where a wide pulse signal in which the exciting current of the transformer 5 is continuous is output. . Accordingly, it is possible to reduce the AC frequency ripple generated in the voltage of the output terminal 7 while maintaining the stability.

The first comparator 106 can increase the power factor of a sinusoidal waveform whose input current is similar to the voltage of the AC input source 1 or a waveform corresponding to the sinusoidal waveform.

FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention. As shown in FIG. 3, the AC input power supply device according to the present embodiment includes a rectifier circuit 8 including a diode connected to the AC input source 1, an inductor 21 connected to the rectifier circuit 8, and a inductor 21 connected to the inductor 21. The first switching unit 2 constituted by the switched switching elements 22 and 23, the energy storage capacitor 3 connected to the inductor 21 via the diode 9, and the switching elements 42 and 43 and the inductor 44 connected to the capacitor 3. A second switching unit 4 having a two-input transformer 5 having two input windings 51 and 52 and an output winding 53 connected to the outputs of the two switching units 2 and 4, and an output winding. A rectifying / smoothing circuit 6 including a diode and an output capacitor connected to the output terminal, an output terminal 7 connected to the rectifying / smoothing circuit 6, Circuit 100B
Composed of and.

Further, as shown in FIG. 3, the control circuit 100B in this embodiment is arranged so that the voltage of the capacitor 3 and the first
The first error amplifier 10 which receives the reference voltage 101 of
2, a multiplier 103 that receives the output of the first error amplifier 102 and the voltage of the AC input source 1 or the absolute value of a sinusoidal oscillation waveform that is synchronized with the voltage, and the output of the multiplier 103 and the inductor 21. A second error amplifier 104, which receives a detection signal of a current flowing through the second error amplifier 104, and a first comparator 106 which receives the output of the second error amplifier 104 and the sawtooth wave output from the sawtooth wave oscillator 105. , A third error amplifier 108 that receives the voltage of the output terminal 7 of the AC input power supply device and the second reference voltage 107, and the output of the third error amplifier 108 and the sawtooth wave from the sawtooth oscillator 105. And a second comparator 109 that receives as input, a fourth error amplifier 110 that receives the voltage of the output terminal 7 of the AC input power supply device and the third reference voltage 130 as input, and an output terminal of the AC input power supply device. 7th voltage and 4th The fifth error amplifier 120 that receives the reference voltage 140 as input, and the first and second diodes 150 and 160 and the sawtooth oscillator connected to the outputs of the fourth and fifth error amplifiers 110 and 120, respectively. The third comparator 111 which receives the sawtooth wave from the input 105 and the inputs of the outputs of the three comparators 106, 109 and 111, NOT,
A logic circuit 112 including AND, NOR and flip-flops, a first drive circuit 113 which receives the output of the logic circuit 112 and drives the switch elements 22 and 23, and a switch element which receives the output of the logic circuit 112 as an input Second drive circuit 114 for driving 42 and 43
Composed of and.

Here, the fourth error amplifier 110 has a high gain, and the fifth error amplifier 120 has a low gain. While the capacitor 3 is discharging, the output voltage of the fourth error amplifier 110 is controlled by the output signal of the fourth error amplifier 110 with a high feedback gain in a range where a narrow pulse signal in which the current of the inductor 44 is discontinuous is output. The voltage of the output terminal 7 is controlled by a wide feedback gain in which the current of the inductor 44 is continuous.
Accordingly, it is possible to reduce the AC frequency ripple generated in the voltage of the output terminal 7 while maintaining the stability.

[0019]

As described above, according to the present invention, the energy storage element, the first switching section to which the AC input source is input and the energy storage element is connected, and the energy storage element to be the input Two switching parts, and the output of the first switching part and the second switching part.
In the control circuit of the AC input power supply device that synthesizes the output of the switching unit to form an output, a plurality of error amplifiers that receive the output voltage and the reference voltage are provided, and the plurality of errors having different feedback gains and reference voltages, respectively. Since the outputs of the amplifiers are connected in parallel, the AC frequency ripple of the output voltage can be reduced while maintaining the stability of the control system.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing characteristics of an error amplifier and a comparator in the present invention.

FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram showing conventional control in an example of an AC input power supply device.

5 is a diagram showing an example of a gate drive voltage waveform of a switch element according to the conventional example of FIG.

6 is a waveform chart showing a problem in the conventional example of FIG.

[Explanation of symbols]

 1 AC Input Source 2 1st Switching Section 3 Capacitor 4 2nd Switching Section 5 Transformer 6 Rectification / Smoothing Circuit 7 Output Terminal 8 Rectification Circuit 9 Diode 21 Inductor 22 Switch Element 23 Switch Element 42 Switch Element 100A Control Circuit 100B Control Circuit 101 First Reference Voltage 102 First Error Amplifier 103 Multiplier 104 Second Error Amplifier 105 Sawtooth Oscillator 106 First Comparator 107 Second Reference Voltage 108 Third Error Amplifier 109 Second Comparator 110 Fourth error amplifier 111 Third comparator 112 Logic circuit 113 First drive circuit 114 Second drive circuit 120 Fifth error amplifier 130 Third reference voltage 140 Fourth reference voltage 150 First diode 160 Second diode

Claims (1)

[Claims] 1. An energy storage device comprising: an energy storage device; a first switching unit having an AC input source as an input and connected to the energy storage device; and a second switching unit having the energy storage device as an input. And control the charging energy from the AC input source to the energy storage element so that it becomes constant, and detect the voltage or current of the energy storage element and input to make the average value constant in this AC cycle. The control of electric power is performed by the switch element in the first switching section, the output energy is detected and the discharge energy from the energy storage element to the output is controlled so as to be constant, and the switch in the second switching section is controlled. The output of the first switching unit and the output of the second switching unit are combined and output. In the control circuit of the AC input power supply device for controlling the output voltage and the voltage or current of the energy storage element, the output voltage and the reference voltage are input, and a plurality of error amplifiers having different feedback gains and different reference voltages are provided. A control circuit of an AC input power supply device, wherein outputs of the plurality of error amplifiers are connected in parallel and input to the first and second switching units.