JPH02211059A - Multi-output regulated power supply - Google Patents

Abstract

PURPOSE:To protect a main switching element from overvoltage by lowering an output voltage through shortening the ON time of said element while clamping the input of a regulated power supply, when an interlock for stopping said regulated power supply operates. CONSTITUTION:When an output voltage is lower than the Zener voltage of a Zener diode ZD10 because of a short circuit of output, etc., a transistor Q10 is OFF and IC20 turns OFF a chopper transistor Q20. Accordingly, when the value of an input voltage VDC rises and exceeds the Zener voltage of a Zener diode ZD1, a command is given to a control circuit 4 via said Zener diode ZD1 and a photocoupler PC and said input voltage VDC is clamped by said Zener voltage. Therefore, the input voltage does not exceed the dielectric strength of said IC20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multi-output stabilized power supply device having a large number of output terminals.

[Conventional technology]

A conventional device of this type of multi-output stabilized power supply device is shown in FIG.
This shows a case with two output terminals where the power source is used as a load driving power source.

In the figure, a switching transistor Ql as a main switching element connects C1 and AC2 to an AC input terminal.
connected in series with the primary winding P1 of the transformer T1 between the DC terminals of the full-wave rectifier bridge circuit DB to which the flute is connected;
The control circuit 4 controls the on/off time ratio. When the switching transistor Ql is turned on, the voltage of the primary winding P1 of the transformer T1 is applied, which causes the secondary winding S
A voltage proportional to the number of turns is induced at t, 52. A pulse voltage is induced in each secondary winding 31.52 by turning on and off the switching transistor Ql.
Output terminal 0UTO, 0UTI side has inductance Ll,
Smoothing filter circuit consisting of capacitor CI, output terminal 0Uf0, 0UT2 side has inductance L2. It is converted into a DC voltage by a smoothing filter circuit consisting of a capacitor C2. The control circuit 3 detects the output voltage and current of one output terminal 0.01171 out of the multiple outputs and feeds it back to the control circuit 4. The control circuit 3 is an operational amplifier OPI whose non-inverting input is a value obtained by dividing the output voltage VDO from the output terminals 01lTO, 0tlT1 and resistors R1 to R3, and whose inverting input is a reference voltage value set by a Zener diode zO. These values are compared and a control signal is sent to the control circuit 4 via the photocoupler PC, which is a feedback element. The operational amplifier OPI lengthens the ON time of the switching transistor Q1 when the output voltage VDD decreases, and increases the ON time of the switching transistor Q1 when the output voltage VDD increases.
Shorten the on time. Operational amplifier OP2 of control circuit 3
detects the voltage generated across the overcurrent detection resistor R5,
A control signal is given to the control circuit 4 via the photocoupler PC to shorten the on time of the switching transistor RO 1. In this way, the on-time of the switching transistor Q1 is controlled so that the output voltage VDD remains constant even if the input terminal F, in and the load current 100 change.

The stabilized power supply circuit 2 connected to the output terminals 011TO and 0tlT2 has an inductance L2. This is for converting the DC voltage smoothed by the capacitor C2 into a constant DC voltage. Although the output voltage VDD of the output terminals 0UTO and 0uT1 is stabilized by feedback control, the voltage on the secondary winding S2 side is not stabilized, so this stabilizing power supply circuit 2 is necessary. This stabilized power supply circuit 2 detects the output voltage vp by IC20 and
20 is turned on and off.

In order to sequence the output, the interlock circuit 1 uses a Zener diode ZD10 to detect when the output voltage VDD has fallen below a certain voltage due to an overload or short circuit, turns off the transistor QIO, and controls the operation of the stabilized power supply circuit 2. is stopped and the output voltage vp is turned off. This is generally used as an output voltage VDD-5ν as a control power source for a microcomputer, etc.
When the output voltage vp is used as a power source for driving a load, when the power source voltage vrJn of the control device decreases, the voltage vp of the power source for driving the load is also decreased to prevent trouble during recovery.

[J'i that the invention tries to solve! fi) The output voltage of the output terminals 01lTO and OυH in the conventional device described above.
As shown in FIG. 4, the current characteristics are such that when the load current 100 increases and exceeds a predetermined value, the output voltage VDD decreases. Therefore, when the output voltage VDD decreases due to overload or the like, the interlock circuit 1 is activated and the operation of the stabilized power supply circuit 2 is stopped. At this time, the input voltage VOC side of the stabilized power supply circuit 2 is in a no-load state, so the value of the input voltage VOC increases as shown by the dotted line VDC2 in Figure 3, which shows the output voltage characteristics of the multi-output stabilized power supply. .

In this way, when the input voltage VDD decreases and the interlock circuit 1 is activated and the stabilized power supply circuit 2 is turned off, the input voltage ■port C of the stabilized power supply circuit 2 is connected to the element used in the stabilized power supply circuit 2. For example, withstand voltage VCCaax of IC20 etc.
This has the disadvantage that the element will be destroyed because it rises to a value exceeding .

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the conventional device, and to solve the problem that when sequentially stopping a multi-output regulated power supply, even if the input voltage of the regulated power supply circuit becomes a conductive voltage, the elements of the regulated power supply circuit are destroyed. The purpose of the present invention is to provide a multi-output stabilized power supply device that never fails.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention has a large number of output terminals, detects the output of at least one output terminal among the large number of output terminals, and detects the output of the main switching element. In a multi-output stabilized power supply device that feeds back to a control circuit that controls the on-off time ratio, when the output of the output terminal that performs the feedback control decreases, the stabilized power supply circuit of the other output terminals An interlock circuit that stops the operation is provided, and a voltage control element is provided that clamps the input voltage of the other output terminal and the child at a predetermined voltage when this interlock circuit is activated, and the activation signal of this voltage @control element is controlled as described above. It is characterized by feeding back to the circuit.

[For production]

In the multi-output stabilized power supply device according to the present invention, the voltage control element detects a voltage at which the interlock circuit is activated and the input voltage of the safe power supply circuit becomes an overvoltage, and the input voltage of the stabilized power supply circuit is kept constant. The voltage is clamped so as not to exceed the voltage, and feedback is applied to a control circuit that controls on/off of the main switching element on the primary side to shorten the on-time ratio of the main switching element and lower the output voltage.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 1 is a circuit diagram of a multi-output stabilized power supply device showing an embodiment of the present invention. In the figure, the same parts as those of the conventional device shown in FIG. is omitted.

The differences between FIG. 1 and FIG. 2 are the positive input terminal A point of the stabilized power supply circuit 2, the anode of the photodiode of the photocoupler PC that constitutes the feedback element of the control circuit 3, and the output terminal of the operational amplifier OPI. This is the point where the Zener diode zD1 is connected between the connection point B and the connection point B.

If an overload or short circuit occurs at the output terminals 0UTO and 0tlT1, the output voltage VDD will drop at a certain point as shown in FIG. When this output voltage vDD becomes lower than the Zener voltage of the Zener diode ZDlO of the interlock circuit 1 and the transistor QIO is turned off, the input terminal T of the IC20 of the stabilized power supply circuit 2 becomes H level. IC
20 sets the chipper transistor Q20 to 0% duty when the T terminal becomes H level.
0 is off. Therefore, the input voltage vnc terminal of the stabilized power supply circuit 2 is in a no-load state, so that the input voltage VOCO value increases. When the value of the input voltage vDC rises and exceeds the Zener voltage of the Zener diode ZDI, the Zener diode 201 becomes conductive and the Zener diode z01.
A current flows through the photodiode of the photocoupler PC through the resistor R4, and the phototransistor becomes deeper (on state).As a result, the control circuit 4 controls the on-time ratio of the switching transistor Q1 to become smaller.
The input voltage vOC is clamped by the Zener voltage as shown by the solid line voct in FIG. Therefore, the input voltage VDC does not exceed the IC20) withstand voltage VCCmax, and
N20 is protected by overvoltage.

Note that the output terminal 0UTO has the output voltage voo, vr'
The common connection is made on the output side of the output terminal, but in the case of isolated output, it is sufficient to isolate the interlock circuit and add one photocoupler for feedback.

In the above embodiment, the forward con/sl-type was explained, but the flyback type is also the same, and is stable and stable.
The power supply circuit may be a dropper type.

〔Effect of the invention〕

According to the present invention described above, the control circuit has a large number of output terminals and controls the on/off time ratio of the main switching element by detecting the output of at least one output terminal among the large number of output terminals. In the multi-output stabilized power supply device which feeds back to A voltage control element is provided that clamps the input voltage of the other output terminal at a predetermined voltage when the interlock circuit is activated, and the actuation signal of this voltage control element is configured to be fed back to the control circuit, and the output is feedback-controlled. When the input terminal of the stabilized power supply circuit on the output terminal side, which stops operating sequentially as the voltage on the terminal side decreases, is in a no-load state and the voltage at the input terminal rises, the voltage control element becomes conductive. By applying feedback to the control circuit that controls the on/off of the main switching element to control the on-time ratio of the main switching element, the input voltage of the stabilized power supply circuit can be prevented from entering an overvoltage state, and the input voltage of the stabilized power supply circuit can be stabilized. This has the advantage that the elements of the power supply circuit can be protected from overvoltage.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a multi-output regulated power supply device according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing a multi-output regulated power supply device of a conventional device, and Fig. 3 is a multi-output regulated power supply device. FIG. 4 is an output voltage/current characteristic diagram of an output terminal subjected to feedback control. 1: Interlock circuit, 2: Stabilized power supply circuit, control circuit, Gelement, Zol, 2010: Control circuit, Ql main switch Zener diode. move

Claims (1)

[Claims] 1) A multi-output device that has a large number of output terminals, and detects the output of at least one of the large number of output terminals and feeds it back to a control circuit that controls the on/off time ratio of the main switching element. In the stabilized power supply device, an interlock circuit is provided that stops the operation of the stabilized power supply circuit of other output terminals when the output of the output terminal that performs the feedback control decreases, and when this interlock circuit is activated, etc. 1. A multi-output stabilized power supply device, characterized in that a voltage control element is provided for clamping an input voltage at an output terminal of the output terminal at a predetermined voltage, and an operation signal of the voltage control element is fed back to the control circuit.