JPS6389055A - Power source device - Google Patents

Abstract

PURPOSE:To reduce the cost of products by insulating the detection system of overcurrents and a power output terminal by using a light-emitting means and a light-receiving means. CONSTITUTION:A DC two-power output type power source device is constituted of a converter transformer T, diodes D2-D3 for preventing reverse currents, diodes D4-D7 for high-frequency rectification, choke coils L1-L2, capacitors C2-C3 for smoothing, light-emitting diodes PD1-PD2 for a photo-coupler, etc. The power device also has a short bar E for positive and negative two- power outputs and a short bar F for a single power output. Consequently, when short circuits are generated between terminals A-B and C-D, fuses F1, F2 are fused, and the light-emitting diodes PD1-PD2 are turned OFF. Accordingly, phototransistors PT1-PT2 are turned OFF, and an abnormal detection signal is output to a control system for a switching element on the primary side of the transformer T through a comparator OP3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a power supply device used as a power supply means for, for example, a telephone exchange.

(Prior Art) For example, as a power supply means for a telephone exchange, etc., a switching means is provided on the primary side of a converter transformer, and the switching means converts input DC into AC, and AC appears on the secondary side of the converter transformer. A switching power supply device is known that outputs direct current by rectifying and smoothing it.

In such a power supply device, if an overcurrent flows through the output line for some reason, the output line must be immediately shut off, so a circuit for detecting overcurrent is installed on the secondary side of the converter transformer. It is provided.

Conventionally, as an overcurrent detection circuit in a power supply device, a current transformer CT is provided on the secondary side of a converter transformer T, as shown in FIG.
The current flowing through T is converted to direct current by rectifying diode D1 and smoothing capacitor C1, and converted to a voltage level by resistor R1. This voltage level and reference voltage VRef are input to comparator OPI, and the current flowing to current transformer CT is comparator OP when becomes above a certain value
An abnormality detection signal is output from I, and this abnormality detection signal is
A circuit is known in which the signal is transmitted to the control system of the next switching element.

Further, as shown in FIG. 5, a resistor (detection resistor) R2 is provided on the output line, the current IL of the output line is converted to a voltage level, this voltage level and the reference voltage VRef are input to the comparator OP2, and the resistor R2 is connected to the output line. A circuit is also known in which an abnormality detection signal is output from the comparator OP2 when the current flowing through R2 exceeds a certain value, and this abnormality detection signal is transmitted to the control system of the primary side switching element.

By the way, in a circuit using a current transformer, the overcurrent detection system and the power output system are insulated, so it is effective when driving by connecting the power output terminals in series or parallel. Since the price of the product is extremely high, there is a problem of high product cost.

On the other hand, circuits using detection resistors have low product costs, but
Since the overcurrent detection system and the power supply output system are not insulated, there is a problem in that when the output terminals are connected in series or in parallel and driven, the detection level fluctuates, making it impossible to perform stable detection.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances. The aim is to provide a power supply device with low product cost.

[Configuration of the Invention (Means for Solving Problems)] The present invention provides switching means on the primary side of a converter transformer, converts input DC into AC, and converts input DC into AC. In a power supply device that rectifies and smooths alternating current that appears in the output line, the converter transformer has a current interrupting means that interrupts the output line when an overcurrent occurs, and a current interrupter that is turned on while current is flowing through the output line, on the secondary side of the converter transformer. However, there is an abnormality in the control system of the light emitting means that turns off when the output line is cut off, the light receiving means that turns on and off according to the on/off of the light emitting means, and the switching means on the primary side when the light receiving means turns off. An abnormality signal generating means for outputting a detection signal is provided.

(Function) In the power supply device of the present invention, when an overcurrent occurs on the secondary side of the converter transformer, the current cutoff means cuts off the output line, the light emitting means and the light receiving means are turned off at that point, and an abnormal signal is generated. The means outputs an abnormality detection signal to the control system of the switching means on the primary side. That is, although the power supply device of the present invention does not use a current transformer, the overcurrent detection system and the power output system are insulated.

(Example) Hereinafter, details of embodiments of the present invention will be explained based on the drawings.

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention.

Note that FIG. 1 is an example of a circuit when a two-output DC power supply device is constructed according to the present invention.

In the figure, T is a converter transformer, D2 and D3 are diodes for backflow prevention, D4 to D7 are diodes for high frequency rectification, Ll and R2 are choke coils, C2 and C3 are smoothing capacitors, and Fl and F2 are overcurrent Fuses that sometimes cut off current, PDl and PD2 are photocoupler light emitting diodes, R3 and R4 are light emitting diodes PD1 and P
The drive resistor D2 and A to D are power output terminals.

Further, E is a short bar used when obtaining two positive and negative power supply outputs, and F is a short bar used when obtaining a single power supply output.

Although the primary side of the converter transformer T is omitted in FIG. 1, the primary side is, for example, a push-pull type switching circuit.

In FIG. 1, when short bar E is used, terminal A becomes a positive output, terminals B and C are ground, and terminal 1 becomes a negative output.

On the other hand, when short bar F is used, terminals A and C are positive outputs, and terminals B and D are ground.

Figure 2 shows the light emitting diodes PCI and PD2 in Figure 1.
2 is a diagram showing the configuration of a phototransistor-side circuit (overcurrent detection circuit) corresponding to FIG.

In the figure, VCC is the control power supply, VRef is the reference power supply, P'F is the phototransistor, R5 is the drive resistance of this phototransistor PT, R6 is the resistor for setting the bias voltage of the phototransistor PT, and OR3 is the collector of the phototransistor PT. Voltage and reference power supply VRe
This is a comparator that compares f.

The operation of the circuit of this embodiment will be described below with reference to these figures.

First, the output generated on the secondary side of the transformer T by high frequency switching of the switching element on the primary side of the transformer T is rectified by the diodes D4 to D7, and the output is rectified by the choke coil L.
1, F2, and a smoothing circuit consisting of capacitors C2 and C3 to obtain direct current.

Then, DC output is obtained from output terminals A to D through fuses F1 and F2 and diodes D2 and D3.

If short bar E is used here, terminals B and C are connected, and a positive output can be obtained between terminals A and B, and a negative output can be obtained between terminals C and D.

Further, when short bar F is used, terminals A, C and terminals B, D are connected, and a positive output can be obtained from between terminals A, C and B, D.

In the circuit described above, between the terminals A and B or between the terminals C and
If a short circuit occurs between D, fuses F1 and F2 will melt, the potential difference between a and b or c and d in Figure 1 will become O, and the current flowing through the light emitting diodes PD1 and PD2 will become O. .

As a result, when phototransistors PTI and PT2 are turned off, the ten terminal of comparator OP3 rises to the power supply voltage VCC, and VCC>VRe f .
The output of No. 3 becomes high level and overcurrent is detected.

The output of this comparator OP3 is output to the control system of the switching element on the primary side of the transformer T as an abnormality detection signal.

Thus, in the device of this embodiment, the light emitting diodes PD1, P
D2 and phototransistors PTI and PT2,
Since the overcurrent detection system and the power supply output terminal are insulated, it is effective even when driving power supply devices connected in series or in parallel, even though no current transformer is used.

In the above-described embodiment, a fuse resistor is used as a means for interrupting the output line, but the present invention is not limited to this. Other parts may be used if necessary.

The present invention can also be applied to an output power supply voltage shortage detection circuit.

FIG. 3 is a diagram showing the circuit configuration in this case.

This circuit is modified from the circuit shown in FIG.
) and the diode D2 (D3) are removed. This circuit corresponds to a circuit similar to that shown in FIG. An abnormality detection signal is output to the control system of the switching element on the side.

[Effects of the Invention] As explained above, in the power supply device of the present invention, the overcurrent detection system and the power output terminal are insulated by using the light emitting means and the light receiving means, so that the power supply device can be connected in series or in parallel. It is also effective when driving with a current transformer, and since no current transformer is used, the product cost does not increase.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an apparatus according to one embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of a circuit corresponding to a part of FIG. 1, and FIG. 3 is another embodiment of the present invention. FIGS. 4 and 5 are circuit diagrams showing the configuration of the main parts of the device, and FIGS. 4 and 5 are circuit diagrams showing the structure of an overcurrent detection circuit in a conventional power supply device.

Claims (3)

[Claims] (1) In a power supply device, a switching means is provided on the primary side of a converter transformer, the switching means converts input DC to AC, and the AC appearing on the secondary side of the converter transformer is rectified and smoothed and outputted, On the secondary side of the converter transformer, current cutting means cuts off the output line when an overcurrent occurs, and light emitting means turns on while current is flowing through the output line and turns off when the output line is cut off. It is characterized by providing a light receiving means that turns on and off in accordance with the turning on and off of the light emitting means, and an abnormality signal generating means that outputs an abnormality detection signal to the control system of the switching means on the primary side when the light receiving means is turned off. and power supply equipment. (2) The power supply device according to claim 1, wherein the current interrupting means is a fuse resistor. (3) The power supply device according to claim 1 or 2, wherein the light emitting means and the light receiving means are internal elements of a photocoupler.