JPH03276077A - Power source protecting circuit - Google Patents

Abstract

PURPOSE:To protect a regulator by interrupting the connection between the regulator and a load when a detecting current of load current detecting means becomes larger than a certain value and also keeping this interrupted state. CONSTITUTION:When the current flowing in a resistor R for detection of the load current becomes larger than the specific value and the voltage drop there from becomes larger than the specific value, e.g., in the case a short-circuit is generated at the load side, this short-circuit is detected by the current detecting means R and a relay Ry is exerted according to this detection to interrupt the connection between the regulator 2 and load 3, then the interrupted state is kept on. Consequently, in case of looking from a regulator, the side of load 3 becomes the open state after it come to the interrupted state and not in the short-circuited state even if the state is back to a normal output state in accordance with the output current decreased thereafter; so, no more overcurrent is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply protection circuit used by being inserted between a regulator and a load.

[Prior Art] Conventional regulators have a protection function that protects the regulator by reducing the output current when a short circuit occurs on the load side.

[Problem to be solved by the invention] By the way, since the protective function provided in the regulator is canceled when the output current decreases,
If the cause of the short circuit is not removed, the regulator will repeat a reduction in output current and a steady output state. As a result, the semiconductor switch used to control the regulator generates heat, resulting in a temperature rise of more than 60 deg per minute, which can cause damage to the semiconductor switch or sudden deformation of the molded parts around it. There was a problem.

The present invention was made in view of the above-mentioned problems, and its purpose is to protect the regulator against short circuits on the load side that last for a long time, thereby preventing damage to the regulator and overheating accidents. - To provide a power protection circuit capable of

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a current detecting means for detecting a load current, which is inserted between a regulator and a load, and a current detecting means for detecting the load current. The device is equipped with a cutoff means that cuts off the connection between the regulator and the load when the detected current exceeds a certain value, and maintains this cutoff state.

[Function] According to the present invention, when a short circuit occurs on the load side, the current detection means detects this short circuit current, and based on this detection, the cutoff means connects and disconnects between the regulator and the load, This shut-off state is maintained. Therefore, from the perspective of the regulator, after the above-mentioned cut-off state occurs, the load side becomes open, and even if the output current returns to the steady output state as the output current decreases, it will not become a short-circuit state and no excessive current will flow. As a result, heat generation and damage to the regulator do not occur, and the regulator can be protected.

[Example] The present invention will be explained below with reference to Examples.

FIG. 2 shows the configuration of an embodiment, in which a power supply protection port N4 of the present invention is connected to a regulator 2 and a load 3, which are of a series control type and have a conventional protection function, which are supplied with power from the main power supply 1, for example.
inserted between.

FIG. 1 shows a concrete circuit of the power supply protection circuit 4, in which there is a normally closed contact r1 of a relay Ry between the output of the regulator 2 and the load 3, and a contact t! for detecting the load current. (It is inserted in series with the resistor R, and furthermore, a series circuit of the normally open contact r2 of the relay Ry and the excitation coil of the relay Ry is connected to the output of the regulator 2.

A delay capacitor C is installed in the excitation coil of relays R and y.
A series circuit of the contact r and a control transistor Q is connected in parallel to the contact r2.

Transistor Q is of PNP type, and its base is connected to the load side end of resistor R.

When the current flowing through the load current detection resistor R exceeds a certain value, the voltage drop exceeds a certain value (for example, 0.6V).
(above), a current flows to the base of the transistor Q, turning it on. Therefore, from regulator 2 to contact r1→
Current flows through transistor Q → parallel circuit of excitation coil of relay Ry and delay capacitor C → regulator 2,
Drive relays R and y. By this driving, relay Ry turns off contact r1 and turns on contact r2. Therefore, when the contact r1 is turned off, the connection between the regulator 2 and the load 3 is disconnected, and when the contact R2 is turned on, a self-holding circuit of the relay Ry is formed. Therefore, until the self-holding circuit of the relay Ry is reset, the regulator 1 and the load 3 are disconnected, and no short-circuit current flows through the regulator 1 after the load 3 is disconnected, and the regulator 1 is protected.

In addition, in the operation of relay Ry, normally closed contact r is turned off before normally open contact r2 is turned on, so there is a risk that the excitation current will be cut off before the self-holding circuit is constructed, resulting in chattering operation. Therefore, in the embodiment circuit of FIG. 1, the excitation of the relay Ry is maintained until the contact r is turned on by discharging the delay capacitor C, thereby preventing the chattering operation.

In this way, in this practical example, the resistor R is used as the current detection means 1j.
A relay Ry and a transistor Q for controlling the relay Ry are used as the cutoff means.

In the above embodiment, the power supply protection port i! is connected between one regulator 2 and the load 3! 34 is inserted, but if there are a plurality of loads 3 connected to the regulator 2 as shown in FIG. 3, a power supply protection circuit 4 is inserted corresponding to each load 3 for use. In this case, if there is a load 3 that does not operate, it is known that that load 3 is abnormal, and normal operation of other loads 3 can be ensured.

Note that a current relay may be used as a breaker tank.

In addition, a photocoupler that turns on when a current exceeding a certain value flows may be provided, and the breaker tank may be driven when the photocoupler is turned on.Furthermore, a comparator may be used to detect the current: detect the voltage across the resistor R for ii. However, the shutoff means may be controlled. Also, SC instead of relay Ry
A semiconductor switch with R may also be used.

[Effects of the Invention] The present invention includes a current detecting means that is inserted between a regulator and a load, and a current detecting means for detecting a load current. The regulator is equipped with a cutoff means that cuts off between the regulator and the load and maintains this cutoff state, so if a short circuit occurs on the load side, the cutoff means cuts off between the regulator and the load and maintains this cutoff state. Therefore, even if the regulator returns to a steady output state as the output current decreases, the load side will not become short-circuited, and excessive current will not flow through the regulator, resulting in heat generation or damage. First, the regulator can be protected, and since the load cannot be used until the cause of the abnormality is removed, the abnormal state can be noticed by the user.

[Brief explanation of drawings]

FIG. 1 is a specific circuit diagram of an embodiment of the present invention, FIG. 2 is an overall configuration diagram showing one usage example of the same, and FIG. 3 is an overall configuration diagram showing another usage example of the invention. 2 is a regulator, 3 is a load, 4 is a power supply protection circuit, R is a current detection resistor, Q is a transistor, Ry is a relay, r
l + r 2 is a contact point.

Claims (1)

[Claims] (1) A device that is inserted between the regulator and the load, and includes a current detection means for detecting the load current, and when the detected current of the current detection means exceeds a certain value, the current detection means is inserted between the regulator and the load. What is claimed is: 1. A power supply protection circuit characterized by comprising a damping means for disconnecting the power and maintaining the damped state.