JPH0697846B2 - Power supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a switching type power supply device for producing a direct current power supply from an alternating current power supply.

<< Prior Art >> Most of the general switching power supplies using a commercial power supply as an input use a capacitor input type rectifier circuit as shown in FIG. That is, the AC input is full-wave rectified by the rectifier circuit 1 including a diode bridge, the pulsating current is smoothed by the capacitor 2, and the DC-DC converter 3
Entered in. As is well known, the waveform of each part of this capacitor input type rectifier circuit is as shown in FIG.

<< Problems to be solved by the invention >> For example, "Switching regulator design know-how"
(CQ Publishing Co., Ltd., issued August 1, 1986, author: Akira Hasegawa) As described on pages 170-171, in the capacitor input type rectifier circuit, the input current Ii
Is a pulse current that flows for a very short time every half cycle of the AC input, and the current peak value becomes very large. Therefore, circuit elements (elements such as rectifier diodes and inrush prevention circuits) that have sufficient withstand current characteristics must be used in the part where the input current flows, which is one of the obstacles to cost reduction. ing.

Moreover, a sharp pulse current having a large peak value flows in the AC power supply line, which considerably deteriorates the noise environment. Since this pulse current is synchronized with the waveform of the power supply,
When many switching regulators are connected to the commercial power supply, their pulse currents are superimposed,
The problem becomes bigger.

In the case of a capacitor input type rectifier circuit, if the AC input voltage is changed from 100V to 200V, for example, the output voltage of the smoothing capacitor 2 also changes, so that
The input voltage to the DC-DC converter 3 exceeds the allowable range and does not operate as a stabilized power supply. 100V as input
In a conventional device capable of supporting both a power source and a 200V power source, the configuration of the rectifier is switched between a voltage doubler rectifier circuit and an ordinary full-wave rectifier circuit by a switch. By switching the switch according to the voltage rank of the input power supply, it is possible to supply a smoothed voltage within an allowable range to the DC-DC converter. In another conventional device, a transformer is provided in the input stage so that the input voltage can be changed by tapping the transformer. In any case, the conventional device requires a switching operation according to the voltage rank of the AC power supply used.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is that an input current from an AC power supply is a current substantially proportional to an input voltage similar to the case of a resistive load, and the voltage rank of the AC power supply is It is an object of the present invention to provide a power supply device capable of generating a substantially constant voltage across the capacitor even if it is changed significantly.

<< Means for Solving Problems >> A power supply device according to the present invention includes a full-wave rectifier circuit (10), a chopper circuit (20), and a control circuit (30). The chopper circuit (20) has two switching elements (Q1, Q2), an inductor (L1), a capacitor (C1) and two diodes (D1 and D2), and two switching elements (Q1 and Q2).
A series circuit in which an inductor (L1) is sandwiched between 1, Q2) is connected between the outputs of the full-wave rectifier circuit (10), and two switching elements (Q1, Q2) are fully controlled by the control circuit (30). The two diodes (D1, D2) are driven on and off at a high constant frequency at the same time, and a capacitor (C1) is sandwiched between them to form a series circuit and are connected across the inductor (L1) to form a series closed loop. Two switching elements (Q
When 1, Q2) is off, the induction current of the inductor (L1) flows in the closed loop, and smoothed DC is output from both ends of the capacitor (C1). The control circuit (30) includes a PWM circuit (31), a multiplier (32), a differential amplifier (33), and a current detection circuit (34).
And an error amplifier (35), the error amplifier (35) detects an error between the output voltage (V2) of the chopper circuit (20) and the reference voltage (Vs), and the current detection circuit (34) is an inductor. (L
The low frequency component of the current (I1) flowing through 1) is detected, and the multiplier (32) multiplies the output voltage signal (V1) of the full wave rectifier circuit (10) by the output signal of the error amplifier (35) to obtain the difference. Motion amplifier (33)
Amplifies the difference between the output signal of the multiplier (32) and the output signal of the current detection circuit (34), and the PWM circuit (31) causes the inductor (L
The pulse width is controlled to drive the two switching elements (Q1, Q2) so that the waveform of the current (I1) flowing through 1) changes following the waveform of the output voltage (V1) of the full-wave rectifier circuit (10). And outputs the drive signal (see FIG. 1).

<< Operation >> In the above configuration, the drive pulse width of the switching elements (Q1, Q2) is controlled by the first control means included in the control circuit (30), and the current (I1) flowing through the inductor (L1) is controlled.
1) changes almost following the full-wave rectified voltage waveform (V1). Further, the drive pulse width of the switching elements (Q1, Q2) is controlled by the second control means included in the control circuit (30), and the output voltage (V2) of the chopper circuit (20) is almost equal to the reference voltage (Vs). Kept equal.

<< Embodiment >> FIG. 1 shows the configuration of a power supply device according to an embodiment of the present invention, which can be used alone as a non-isolated AC-DC converter, or as a front stage of an isolated DC-DC converter. It may be used as an AC-DC converter. FIG. 2 is a waveform diagram of the main part of the circuit of FIG.

The sine wave AC input is full-wave rectified by a rectifier circuit 10 composed of a diode bridge and input to a step-up chopper circuit 20 described in detail below. The chopper circuit 20 is a rectifier circuit sandwiched between two switching elements Q1 and Q2 which are simultaneously turned on / off by a PWM (pulse width control) circuit 31 at a constant frequency sufficiently higher than an AC power supply, and switching elements Q1 and Q2. Inductor L1 connected in series between 10 outputs,
It has two diodes D1 and D2 connected in series across the inductor L1 and a capacitor C1 so that current flows through the inductor L1 when the switching elements Q1 and Q2 are off. One end of the capacitor C1 is commonly connected to the input minus line. The capacitor C1 has a considerably large capacity, and is smoothed from both ends to stabilize the voltage (described later).
The generated DC output is taken out. The capacitor C2 is a small-capacity capacitor for absorbing high frequency ripple and is not essential to the present invention.

A signal of the full-wave rectified output voltage V1 of the rectifier circuit 10 is input to a differential amplifier 33 via a VCA (voltage control type variable gain amplifier) 32 as a multiplier. The current I1 flowing through the inductor L1 of the chopper circuit 20 is detected by the current transformer 34 that constitutes the current detection circuit, and the signal of the low frequency component is input to the differential amplifier 33. The PWM circuit 31 operates according to the differential output of the differential amplifier 33, and changes the drive pulse width (ON time) of the switching elements Q1 and Q2 so that the differential output is minimized. Further, the error of the output voltage V2 of the chopper circuit 20 with respect to the reference voltage Vs is detected by the error amplifier 35, and this output becomes the control voltage of the VCA32.

In the above configuration, the differential amplifier 33 has a chopper circuit.
The waveform of the input V1 of 20 and the waveform of the current I1 flowing through the inductor L1 are compared, and the ON time of the switching elements Q1 and Q2 is changed by the PWM circuit 31 so that the current waveform changes following the voltage waveform. .

When the switching elements Q1 and Q2 are on, current flows from the rectifier circuit 10 to the inductor L1 through the switching elements Q1 and Q2, and energy is stored in the inductor L1. The current increase value during the ON period is proportional to the input voltage V1 and also to the ON time. When the switching elements Q1 and Q2 are turned off, a current due to the release of energy accumulated in the switching elements is supplied to the capacitor C1 side. The pulse width control by comparing the input voltage waveform and the current waveform of the inductor L1 shows that as the input voltage V1 increases, the switching elements Q1, Q2
Acts to shorten the on time of. By this control, the change of the current waveform becomes almost equal to the full-wave rectified waveform of the input voltage. That is, when viewed from the AC input side, the input voltage and the input current have substantially the same waveform and there is no phase difference, and the state is almost the same as when the load is a resistor. The above is the operation of the first control means included in the control circuit 30.

Further, the second control means included in the control circuit 30 operates as follows. If the output voltage V2 is higher than the reference voltage Vs, VC
As the gain of A32 becomes smaller and V2 is smaller than Vs, VCA32
The gain of becomes large. This VCA32 is a circuit through which the waveform signal of the input voltage in the first control means passes, and the gain thereof is a basic parameter of the first control means. That is, if the output voltage V2 is too high, the switching elements Q1, Q2
ON time is shortened, and conversely, if it is too low, ON time is extended, and it acts so that the output voltage V2 approaches the reference voltage Vs.

<< Effects of the Invention >> As described in detail above, in the power supply device according to the present invention, the input current changes substantially in accordance with the AC input voltage and has a substantially sinusoidal shape with no phase difference. The relationship between the voltage and current is almost the same as in the case of resistive load. Therefore, unlike the conventional capacitor-input type rectifier circuit, a large pulse current does not flow intensively in a short time, the restrictions on the withstand current characteristics of the circuit elements are relaxed, and various AC power lines are connected. It is possible to reduce noise that has an adverse effect.

In addition, the step-up and step-down actions of the chopper circuit, and the second
Even if the voltage of the AC input fluctuates or the voltage rank is changed, the output voltage can be kept constant by the feedback control action of the output voltage by the control means. As a result, no switching is required,
For example, a power supply device compatible with 100 V AC power supply to 400 V AC power supply can be easily configured.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of essential parts of the circuit of FIG. 1, and FIG. 3 is a circuit diagram of a conventional capacitor input type power supply device. FIG. 4 is a waveform diagram of essential parts of the circuit of FIG. 10 …… Rectifier circuit 20 …… Chopper circuit Q1, Q2 …… Switching element L1 …… Inductor C1 …… Capacitor D1, D2 …… Diode 30 …… Control circuit 31 …… PWM (pulse width control) circuit 32 …… Multiplication Transformer (VCA) 33 …… Differential amplifier 34 …… Current detection circuit (current transformer) 35 …… Error amplifier

Claims (1)

[Claims] 1. A full-wave rectifier circuit (10) and a chopper circuit (20).
And a control circuit (30), the chopper circuit (20) includes two switching elements (Q1, Q
2), inductor (L1), capacitor (C1) and two diodes (D1 and D2), and the inductor (L1) is sandwiched between two switching elements (Q1, Q2). Connected between the outputs of the wave rectifier circuit (10), the two switching elements (Q1, Q2) are simultaneously turned on / off at a sufficiently high constant frequency by the control circuit (30).
Two diodes (D1, D2) with a capacitor (C1) in between
A series circuit is sandwiched between the inductor (L1) and connected to both ends of the inductor (L1) to form a series closed loop. When the two switching elements (Q1, Q2) are off, the inductor (L1)
The induced current of 1) flows, and smoothed DC is output from both ends of the capacitor (C1). The control circuit (30) controls the PWM circuit (31), multiplier (32), differential amplifier (33) and current. Detection circuit (34) and error amplifier (3
5) and the error amplifier (35) has a chopper circuit (20).
Error between output voltage (V2) and reference voltage (Vs) is detected, current detection circuit (34) detects low frequency component of current (I1) flowing through inductor (L1), and multiplier (32) Is an error amplifier (35) for the output voltage signal (V1) of the full-wave rectifier circuit (10)
Multiply the output signals of the differential amplifier (33) and the multiplier (32)
Of the output signal of the full-wave rectifier circuit (10) is amplified by amplifying the difference between the output signal of the current detection circuit (34) and the output signal of the current detection circuit (34). V1)
A power supply device that outputs a drive signal with pulse width control that drives two switching elements (Q1, Q2) so that they change following the waveform of.