JPH0697845B2 - 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), a control circuit (30), and a DC-DC converter (40). is there. The chopper circuit (20)
It has a switching element (Q1), an inductor (L1), a capacitor (C1), and a diode (D1). The switching element (Q1) is connected to one output side of the full-wave rectifier circuit (10), and the inductor (L1 ) Is connected to the output side of the switching element (Q1) and the other output side of the full-wave rectifier circuit (10), and the capacitor (C1) is connected in the forward direction to the diode (D1).
Connected to the output side of the switching element (Q1) and the other output side of the full-wave rectifier circuit (10) via a capacitor (C1)
Outputs smoothed DC from both ends of. DC-DC converter (40) consists of transformer (41) and switching element (Q3)
And a drive circuit (42) and a rectifying / smoothing circuit (D3, D4, L4, C3), the primary winding (L2) of the transformer (41) and the switching element (Q3) are connected in series to the chopper circuit (20). Connected to the output side of the drive circuit (42) drives the switching element (Q3) on and off at a sufficiently high constant frequency with a predetermined duty ratio, and the rectifying and smoothing circuit (D3, D4, L4, C3) It rectifies and smoothes the output of the secondary winding (L3) of (41) and outputs stable DC. The control circuit (30) has a PWM circuit (31), a multiplier (32), a differential amplifier (33), a current detection circuit (34) and an error amplifier (35).
5) detects the error between the output voltage (V3) of the DC-DC converter (40) and the reference voltage (Vs), and the current detection circuit (34) detects the low frequency of the current (I1) flowing through the inductor (L1). A component (32) detects the component, 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), and the differential amplifier (33) multiplies 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), and the waveform of the current (I1) flowing through the inductor (L1) in the PWM circuit (31). It outputs a pulse width controlled drive signal that drives the switching element (Q1) at a sufficiently high constant frequency so as to change following the waveform of V1) (see Fig. 1).

<< Operation >> In the above configuration, the drive pulse width of the switching element (Q1) is controlled by the first control means included in the control circuit (30), and the current (I1) flowing through the inductor (L1) is the full-wave rectified voltage. It changes almost following the waveform (V1). Further, the drive pulse width of the switching element (Q1) is controlled by the second control means included in the control circuit (30),
-The output voltage (V3) of the DC converter (40) is the reference voltage (V3
s).

<< Embodiment >> FIG. 1 shows a configuration of a power supply device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram of a main portion thereof.

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 includes a switching element Q1 driven on / off by a PWM (pulse width control) circuit 31 at a constant frequency sufficiently higher than an AC power supply,
Inductor L1 connected in series between the output of rectifier circuit 10 together with switching element Q1, diode D1 and capacitor connected in series across inductor L1 so that current flows through inductor L1 when switching element Q1 is off.
With C1. The capacitor C1 has a considerably large capacity,
From both ends of this, a DC output that is smoothed with the opposite polarity to the input and stabilized in voltage (described later) is taken out. The capacitor C2 is a small-capacity capacitor for absorbing high frequency ripple and is not essential to the present invention.

The output of the chopper circuit 20 becomes an output of a predetermined voltage further stabilized by the insulation type DC-DC converter 40, and is supplied to the load.

The DC-DC converter 40 of this example has a well-known configuration, in which the primary winding L2 of the transformer 41 and the switching element Q3 are connected in series and connected to both ends of the capacitor C1.
Is driven on / off by a driving circuit 42 at a sufficiently high constant frequency with a predetermined duty ratio. Then, the output of the secondary winding L3 of the transformer 41 is rectified and smoothed by the diodes D3 and D4, the inductor L4, and the capacitor C3 to obtain a DC output.

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 element Q1 so that the differential output is minimized. Also,
An error of the output voltage V3 of the DC-DC converter 40 with respect to the reference voltage Vs is detected by the error amplifier 35, and this output becomes the control voltage of the VCA 32 via the photo isolator 36.

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

When the switching element Q1 is on, current flows from the rectifier circuit 10 to the inductor L1 through the switching element Q1 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 element Q1 is turned off, the current due to the release of the energy stored in the switching element Q1
Supplied to the side.

As a result, the pulse width control by comparing the input voltage waveform and the current waveform of the inductor L1 acts to shorten the ON time of the switching element Q1 as the input voltage V1 increases. By this control, the change in the current waveform becomes substantially equal to the line-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 V3 is higher than the reference voltage Vs, VC
As the gain of A32 becomes smaller and V3 becomes 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 V3 is too high, the on-time of the switching element Q1 is shortened, and if it is too low, the on-time is newly adjusted, which causes the output voltage V3 of the chopper circuit 20, that is, the input voltage V2 of the DC-DC converter 40. Is increased or decreased, and as a result, the output voltage V3 of the DC-DC converter 40 acts so as to approach 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 current 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 …… Switching element L1 …… Inductor C1 …… Capacitor D1 …… Diode 30 …… Control circuit 31 …… PWM (pulse width control) circuit 32 …… Multiplier (VCA) 33 …… Differential amplifier 34 …… Current detection circuit (current transformer) 35 …… Error amplifier 40 …… DC-DC converter 41 …… Transformer 42 …… Drive circuit Q3 …… Switching element

Claims (1)

[Claims] 1. A full-wave rectifier circuit (10) and a chopper circuit (20).
A chopper circuit (20) includes a switching element (Q1), an inductor (L1), a capacitor (C1), and a diode (D1), which is a power supply device having a control circuit (30), a DC-DC converter (40), and a control circuit (30). With a switching element (Q1) full-wave rectifier circuit (10)
The inductor (L1) was connected to the output side of the switching element (Q1) and the other output side of the full-wave rectifier circuit (10), and the capacitor (C1) was connected in the forward direction. Switching element (Q
1) is connected to the output side of the full-wave rectifier circuit (10) and the smoothed DC is output from both ends of the capacitor (C1). The DC-DC converter (40) is connected to the transformer (41). ), Switching element (Q3), drive circuit (42), rectifying and smoothing circuit (D3
D4 ・ L4 ・ C3) and the primary winding (L
2) and the switching element (Q3) are connected in series to the output side of the chopper circuit (20), and the drive circuit (42) turns the switching element (Q3) on / off with a sufficiently high constant frequency and a predetermined duty ratio. Drive and rectify and smooth circuit (D3 ・ D4
・ L4 ・ C3) rectifies and smoothes the output of the secondary winding (L3) of the transformer (41) to output stable DC, and the control circuit (30) controls the PWM circuit (31) and multiplier (32). ), A differential amplifier (33), a current detection circuit (34), and an error amplifier (3
5) and the error amplifier (35) has a DC-DC converter (4
0) output voltage (V3) and reference voltage (Vs) error component is detected, the current detection circuit (34) detects the low frequency component of the current (I1) flowing through the inductor (L1), and the multiplier ( 32) uses the error amplifier (3) as the output voltage signal (V1) of the full-wave rectifier circuit (10).
5) The output signal of 5) is multiplied, and the differential amplifier (33)
The difference between the output signal of 2) and the output signal of the current detection circuit (34) is amplified, and the waveform of the current (I1) flowing through the inductor (L1) in the PWM circuit (31) is the output of the full-wave rectification circuit (10). A power supply device that outputs a pulse-width-controlled drive signal that drives the switching element (Q1) at a sufficiently high constant frequency so that it changes following the voltage (V1) waveform.