JPS61281315A - Power circuit - Google Patents

Abstract

PURPOSE:To control efficiently an output side by detecting an increase of a control current, turning on a control transistor thereby, and limiting a control current of a stabilizing circuit. CONSTITUTION:A power circuit is constituted of an input voltage 1, a stabilizing circuit 2, a reference voltage setting circuit 3, and a control circuit 4. In this state, as for this control circuit 4, when a current taken out from an output side increases, a current flowing through its resistances 401, 402 also increases, and when a voltage drop during this time increases to an on-voltage of a control transistor 402, it is turned on, a control output 42 is set to zero and a transistor 201 of the reference voltage setting circuit 3 and the stabilizing circuit 2 is turned off. As a result, an output also becomes zero, and an output current can be limited.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to overcurrent control in stabilized power supply circuits used in general equipment.

Conventional technology In a conventional stabilized power supply circuit (hereinafter referred to as a power supply), when an overcurrent flows such as blocking the output terminal of the power supply, a limiting resistor is provided in the load current line, or a circuit shown in Fig. 3 is used. As shown in the figure, a control circuit 24 is provided on the load current line, and this controls the reference voltage setting circuit 3 and the stabilizing circuit 2.
A method was used to limit the output current.

Problems to be Solved by the Invention In any conventional circuit, the larger the amount of current to be detected, the larger the current capacity of the limiting resistor is required. Inserting the power supply increases the output impedance of the power supply, which causes a voltage drop even in normal use, and there is a problem that complete stabilization is not achieved.

The present invention has been made in view of this point.

The aim is to provide a circuit that controls output by controlling the control current, which changes not by the current flowing through the load itself, but by changes in the load.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems.
Focusing on the fact that the control current (base current) of This limits the control current (base current) of the

In addition to the above-described configuration, the present invention incorporates the control system including the detection section into the control system rather than the direct load current of the power supply, thereby reducing the current capacity required on the detection side. Embodiment FIG. 1 is a block diagram showing an embodiment of the power supply circuit of the present invention.

In FIG. 1, 1 is an input voltage, 2 is a stabilizing circuit, 3 is a reference voltage setting circuit, and 4 is a control circuit, which has a control current input terminal 41 and a control output terminal .

The control circuit 4 normally applies a control output corresponding to the output current to the reference voltage setting circuit 3 and the stabilizing circuit 2.

Here, when the output current increases and the control input to the input terminal 41 increases, the control circuit 4 limits the control output from the control output terminal 42 that is applied to the reference voltage setting circuit 3, so that the output current is limited. That will happen.

FIG. 2 shows another embodiment of the present invention, in which a control transistor 403 and resistors 401 and 402 are connected so as to control a stabilizing circuit 2 consisting of a transistor 2o1 and a reference voltage setting circuit 3 consisting of a diode 301. A control circuit 4 consisting of the following is connected.

When the current taken out from the output side increases in this state, the current flowing through the resistors 401 and 402 also increases, and when the voltage drop during this period increases to the ON voltage of the control transistor 402, the control transistor 402 turns ON1, . When the output is 0, the transistor 2o1 of the reference voltage setting circuit 3 is turned off, the output is also 0, and the output current is limited.

Effects of the Invention As described above, according to the present invention, it is possible to provide a useful power supply circuit that can limit excessive output current with an extremely simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a power supply circuit according to one embodiment of the present invention, FIG. 2 is a circuit diagram of a power supply circuit according to another embodiment of the present invention, and FIG. 3 is a block diagram of a conventional power supply circuit. 2... Stabilization circuit, 3... Reference voltage setting circuit, 4... Control circuit, 41... Control input terminal, 42...・Control output terminal. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
0 Figure 3

Claims (1)

[Claims] In addition to a reference voltage setting circuit and a stabilizing circuit that can obtain an output voltage by a circuit that controls a control current that changes in proportion to the output current, a stabilization circuit that detects the control current and when an output current exceeding a certain setting flows. A power supply circuit comprising: a circuit for controlling a control current and limiting an output current;