JP2512040B2 - 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. In other words, the AC input is full-wave rectified by the rectifier circuit 1 consisting of a diode bridge,
The pulsating flow is smoothed by the capacitor 2 and input to the DC-DC converter 3. 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 remains within the allowable range. It exceeds the limit and does not work as a stabilized power supply. 10 as input
In a conventional device capable of supporting both 0V power source and 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 the Problems >> A power supply device according to the present invention is a rectifier circuit that full-wave rectifies an AC power supply to obtain a pulsating current output; and is driven on / off at a frequency sufficiently higher than the AC power supply. A switching element, an inductor connected in series with the output of the rectifier circuit together with the switching element, a diode and a capacitor connected in series across the switching element so that a current flows through the inductor when the switching element is off. A chopper circuit that obtains a smoothed DC output from both ends of the capacitor; an insulation type DC-DC converter that stabilizes the output of the chopper circuit to obtain a DC output of a predetermined voltage; and an output voltage of the rectifier circuit. A voltage waveform detecting means for detecting the waveform of the low-frequency component of the current flowing through the inductance. Current waveform detection means; waveform comparison means for comparing the voltage waveform detected by the voltage waveform detection means with the current waveform detected by the current waveform detection means and outputting the difference between these waveform signals; the waveform comparison First control means for controlling the drive pulse width of the switching element so that the difference output from the means is minimized so that the current waveform changes following the voltage waveform; Output voltage detecting means for detecting the output voltage of the DC converter; reference voltage comparing means for comparing the output voltage detected by the output voltage detecting means with a reference voltage and outputting an error of this output voltage with respect to the reference voltage. Second control means for controlling the drive pulse width of the switching element so that the error output from the reference voltage comparison means becomes small.

<< Operation >> In the above configuration, the drive pulse width of the switching element is controlled by the first control means, and the current flowing through the inductor changes substantially following the full-wave rectified voltage waveform. Further, the drive pulse width of the switching element is controlled by the second control means, and the output voltage of the DC-DC converter is kept substantially equal to the reference voltage.

<< 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, together with a switching element Q1 and a switching element Q1 which are driven on / off by a PWM (pulse width control) circuit 31 as a first control means and a second control means at a frequency sufficiently higher than an AC power supply. Inductor L1 connected in series between the outputs of rectifier circuit 10 and switching element Q1 so that current flows through inductor L1 when switching element Q1 is off.
Has a diode D1 and a capacitor C1 connected in series at both ends of the. The capacitor C1 has a considerably large capacity, and a smoothed and voltage-stabilized (described later) DC output is taken out from both ends of the capacitor C1. 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,
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.
The drive circuit 42 drives Q3 on / off at a sufficiently high frequency with a predetermined duty ratio. And transformer 41
The output of the secondary winding L3 of the diode D3 and D4, inductor L
4. DC output is obtained by rectifying and smoothing with capacitor C3.

The signal of the full-wave rectified output voltage V1 of the rectifier circuit 10 is VCA (voltage control type variable gain amplifier) 3 as a voltage waveform detecting means.
It is input to the differential amplifier 33 as a waveform comparison means via 2. The current I1 flowing through the inductor L1 of the chopper circuit 20 is detected by the current transformer 34 as current waveform detection means, and the signal of the low frequency component is input to the differential amplifier 33. 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. Further, the error of the output voltage V3 of the DC-DC converter 40 with respect to the reference voltage Vs is an error amplifier 35 as an output voltage detecting means and a reference voltage comparing means.
This output is detected by the photoisolator 36
It becomes the control voltage of VCA32.

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

When the switching element Q1 is on, a current flows from the rectifier circuit 10 to the inductor L1 through the switching element Q1,
Energy is stored in inductor L1. The current increase value during this ON period is proportional to the input voltage V1 and is also proportional to the ON time. When the switching element Q1 is turned off, a current due to the release of the energy stored therein is generated by the rectifier circuit 10.
And is supplied to the capacitor C1 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. With this control, the change in the current waveform becomes substantially 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 no phase difference, and the state is almost the same as if the load were a resistor. The above is the operation of the first control means described above.

The second control means operates as follows. The gain of the VCA32 decreases as the output voltage V3 is higher than the reference voltage Vs, and the gain of the VCA32 increases as V3 is lower than Vs. The VCA 32 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, output voltage 3
Is too high, the on-time of the switching element Q1 is shortened, and conversely, if it is too low, the on-time is extended, whereby 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. 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 following the AC input voltage,
It becomes almost sinusoidal with no phase difference, and the relationship between voltage and current seen from the AC power supply side is almost the same as in the case of a resistive load.
Therefore, unlike the conventional capacitor input type rectifier circuit, a large pulse current does not flow intensively in a short period of time, so that the restrictions on the current resistance characteristics of the circuit elements are relaxed and various AC power supply lines are used. It is possible to reduce adverse noise.

Further, the output voltage is kept constant even when the AC input voltage fluctuates or the voltage rank is changed by the boost operation of the chopper circuit and the feedback control operation of the output voltage by the second control means. Can be. As a result, it is possible to easily configure a power supply device that does not require switching at all and is suitable for, for example, an AC 100V power supply to an AC 200V power supply.

[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 31 …… Pulse width control circuit 40 …… DC-DC converter

Claims (1)

(57) [Claims] 1. A rectifying circuit for full-wave rectifying an AC power source to obtain a pulsating flow output; a switching element which is on / off driven at a frequency sufficiently higher than the AC power source; and an output of the rectifying circuit together with this switching element. An inductor connected in series between the switching element and a diode and a capacitor connected in series at both ends of the switching element so that current flows through the inductor when the switching element is off, and a DC output smoothed from both ends of the capacitor. A chopper circuit for obtaining the above; an insulation type DC-DC converter for stabilizing the output of the chopper circuit to obtain a DC output of a predetermined voltage; a voltage waveform detecting means for detecting a waveform of the output voltage of the rectifier circuit; A current waveform detecting means for detecting a waveform of a low frequency component of a current flowing through; Waveform comparing means for comparing the output voltage waveform with the current waveform detected by the current waveform detecting means and outputting the difference between these waveform signals; and for minimizing the difference output from the waveform comparing means. First control means for controlling the drive pulse width of the switching element so that the current waveform changes following the voltage waveform; and output voltage detection means for detecting the output voltage of the DC-DC converter. Reference voltage comparing means for comparing the output voltage detected by the output voltage detecting means with a reference voltage and outputting an error of the output voltage with respect to the reference voltage; and the error output from the reference voltage comparing means. A second control means for controlling the drive pulse width of the switching element so that