JPH03218262A - Positive/negative output type power supply - Google Patents

Abstract

PURPOSE:To improve power factor through a simple constitution by employing the intermediate tap, equally dividing the secondary winding of a transformer, as an earth line and arranging plus and minus side choppers symmetrically. CONSTITUTION:An AC power supply 1 is connected with the primary winding of a transformer 2 and an intermediate tap, equally dividing the secondary winding, is employed as an earth line 8. A plus side rectifying circuit comprising diodes D1, D2 produces a full-wave rectified plus output for the earth line 8, whereas a minus side rectifying circuit comprising diodes D3, D4 produces a full-wave rectified minus output for the earth line 8. Switching elements Q1, Q2 in the plus and minus side chopper circuits 6, 7 are turned ON/OFF simultaneously through plus and minus side drive circuits 3, 4. A controller 5 provides a control signal commonly to the drive circuits 3, 4.

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a power factor correction type power supply device that creates stable DC power from an AC power supply using chopper control, and in particular,
The present invention relates to a dual-output power supply device that generates positive and negative outputs that are symmetrical with respect to a ground line.

<Prior art> AC power is rectified and input to the chopper circuit [7. In a power supply device that rectifies and smoothes the output of the chopper circuit to obtain a stable DC output, the current flowing through the inductor or switching element of the chopper circuit is By controlling the drive pulse width of the chopper circuit's switching elements so that the waveform of the low-frequency component of the current changes to follow the waveform of the output voltage of the rectifier circuit in the preceding stage of the chopper circuit, the power factor can be brought close to 1. A control system using this method is known.

In this type of power supply device, the input current changes almost following the AC input voltage, forming a nearly sinusoidal wave 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. become. Therefore, unlike conventional capacitor input type rectifier circuits, large pulse currents do not flow in a concentrated manner in a short period of time, and restrictions on the current withstand characteristics of circuit elements are relaxed. can reduce noise.

[Problems to be Solved by the Invention] When configuring a power factor correction power supply device as described above, which generates a positive and negative output that is symmetrical with respect to the ground line, conventionally an insulated type power supply device is used. It was a combination of two power supplies. Therefore, the overall configuration requires a combination of two power supply devices, resulting in a very large and expensive device.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to realize a power factor correction type positive and negative output type power supply device with the simplest possible configuration.

4 <<Means for solving the problem>> Therefore, in this invention, a transformer is provided in the input stage, an AC power source is connected to the primary side, and a middle tap that divides the secondary winding into two is used as a ground line for rectification. The circuit and the chopper circuit are configured symmetrically on the plus side and the minus side, respectively. A configuration in which the switching elements of the plus side and minus side chopper circuits are simultaneously turned on and off via the plus side and minus side drivers, and a common control signal is given to both drivers from one controller. shall be.

The controller is configured to control both switching so that the waveform of the low frequency component of the current flowing through the inductor or switching element in the plus side or minus side chopper circuit changes to follow the waveform of the output voltage of the plus side or minus side rectifier circuit. a first control means for controlling the drive pulse width of the element; and a first control means for controlling the width of the drive pulse 5 of both the switching elements so as to reduce the error between the voltages at the output terminals of the plus side and minus side chopper circuits and the reference voltage. A second control means is provided to perform the control.

<<Operation>> According to the above configuration, the switching control system of the positive side chopper circuit and the negative side chopper circuit is shared, and the power factor correction type power supply device operates as a power factor correction type positive and negative output type power supply device with a simpler configuration.

<<Embodiment>> FIG. 1 shows the overall configuration of a positive and negative output type power supply device according to an embodiment of the present invention. AC power supply 1 is transformer 2
connected to the primary winding of the The secondary winding of the transformer 2 has a middle tap that divides the winding into two equal parts, and the middle tap becomes the ground line 8.

The diodes D1 and D2 constitute a positive side rectifier circuit, and produce a positive output that has been rectified afterward to the ground line 8. The diodes D3 and D4 are a negative side rectifier circuit, and produce a negative output that is rectified afterward with respect to the ground line 8. Note that the capacitors C1 and 02 are small-capacity capacitors for absorbing high-frequency ripples, and are not essential to this device.

6 6 is a positive chopper circuit, which includes an inductor L1, a switching element Ql, a diode D5, a capacitor C
Consists of 3. The switching element Q] is turned on and off by a positive driver 3 at a frequency sufficiently higher than that of the AC power supply 1. The inductor L1 and the switching element Q1 are connected in series between the output terminals of the positive rectifier circuits DI and D2 and the earth line 8. Furthermore, the diode D5 and the capacitor C3 are connected in series across the switching element Q1 so that current flows through the inductor L1 when the switching element Q1 is off. This capacitor C3 has a considerably large capacity, and a smoothed positive DC output is taken out from both ends of the capacitor C3.

7 is a negative chopper circuit to which the outputs of the negative rectifier circuits D3 and D4 are applied, and is composed of an inductor L2, a switching element Q2, a diode D6, and a capacitor C4, and its configuration is symmetrical to that of the positive chopper circuit 6. . The switching element Q2 is turned on/off by the negative driver 4, and a smoothed negative DC output is taken out from both ends of the capacitor C4.

A common control signal is input from the controller 5 to the positive side drive circuit 3 and the negative side drive circuit 4, and both switching elements Q1 and Q2 are simultaneously driven on/off by this control signal. The controller 5 forms the main part of the control circuit of the power factor correction method, and is connected to the positive side rectifier circuit DI.
, D2 output voltage waveform a and the waveform signal b of the current flowing through the inductor L1 of the positive chopper circuit 6 (current transformer 10
), the voltage between the output terminal of the plus side chopper circuit 6 and the output terminal of the minus side chopper circuit 7 is detected by the resistor R]
The voltage signal C divided by and R2 is used as an input signal, and the driving pulse widths of both switching elements Q1 and Q2 are controlled as follows.

FIG. 2 shows the circuit configuration of the controller 5. The output voltage waveform a of the positive side control circuits DI and D2 is VCA (
differential amplifier 53 via voltage controlled variable gain amplifier) 52
is input. Inductor L of positive chopper circuit 6
1 is detected by current transformer 10, and its low frequency component signal b is input to differential amplifier 33. P
The WM (pulse width control) circuit 54 is connected to this differential amplifier 53.
The drive pulse width of both switching elements QIQ2 (
on time).

Further, the values of the resistors R1 and R2 connected between the output terminals of the chopper circuits on the plus side and the minus side are different, and the voltage C at the midpoint is inputted to the error amplifier 51, and the reference voltage Vs
Errors for are detected.

This error output becomes the control voltage of the VCA 52.

In the above configuration, the differential amplifier 53 compares the input voltage waveform a of the chopper circuit 6 with the current waveform b flowing through the inductor L1, and controls the PWM circuit so that the current waveform b changes to follow the voltage waveform a. 54, the on time of both switching elements Ql and Q2 can be changed.

Further, the larger the divided voltage C between the output terminals is than the reference voltage Vs, the smaller the gain of the VCA 52 becomes, and the smaller the divided voltage C is smaller than the reference voltage Vs, the larger the gain of the VCA 952 becomes. This VCA 52 is a circuit through which the input voltage waveform signal a passes, and its gain is the first one.
This is the standard parameter for the control means. That is, if the divided voltage C is too high, the on time of the switching elements Ql and Q2 will be shortened, and if it is too low, the on time will be extended, and this will act to bring the output divided voltage C closer to the reference voltage Vs.

As explained in detail above, in this type of power supply,
The input current changes almost following the AC input voltage, becoming almost a sine wave with no phase difference, and the relationship between voltage and current seen from the AC power supply side is almost the same as that of a resistive load (the power factor is improved). ).

<<Problems to be Solved by the Invention>> As explained in detail above, the positive and negative output power supply device according to the present invention controls the two chopper circuits on the plus side and the minus side by a so-called power factor correction control circuit. Since the circuit systems that control both chopper circuits are integrated into one system, the overall configuration is extremely simple, and the device is inexpensive and compact. It can be realized.

[Brief explanation of drawings]

FIG. 1 is an overall circuit diagram of a dual-output power supply device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram of a controller 5 in FIG. 1. 1... AC power supply 2... Transformer 3... Positive side driver 4... Negative side driver 5... Controller 6...・Positive side chopper circuit

Claims (1)

[Claims] A transformer to which an AC power source is connected to the primary side; the intermediate tap that divides the secondary winding of this transformer into two halves is used as a ground line, and the outputs at both ends of the secondary winding are full-wave rectified. a positive side rectifier circuit and a negative side rectifier circuit to obtain a pulsating output; a switching element that is driven on/off at a sufficiently higher frequency than the AC power supply; and a connection between the output of the positive side rectifier circuit and the switching element; An inductor connected in series, a diode and a capacitor connected in series across the switching element such that current flows through the inductor when the switching element is turned off, and a smoothed DC output from both ends of the capacitor. a side chopper circuit; a switching element that is driven on and off at a sufficiently higher frequency than the AC power source; an inductor that is connected in series with the switching element between the output of the negative side rectifier circuit; a negative side chopper circuit including a diode and a capacitor connected in series across both ends of the switching element so that current flows through the inductor, and obtaining smoothed DC output from both ends of the capacitor; the positive side and negative side chopper circuits; a positive-side driver and a negative-side driver that simultaneously turn on and off the switching elements; a controller that provides a common control signal to the positive-side and negative-side drivers; Controlling the drive pulse width of both switching elements so that the waveform of the low frequency component of the current flowing through the inductor or the switching element in the chopper circuit changes to follow the waveform of the output voltage of the positive side or negative side rectifier circuit. and a second control means that controls drive pulse widths of both the switching elements so as to reduce an error between the voltage between the output terminals of the positive side and negative side chopper circuits and the reference voltage. A power supply device with both positive and negative outputs.