JPH10136585A - Power switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lighten the load capacity required at standby time, and make a power circuit at the time small-capacity and inexpensive by switching the power at normal operation and the power at standby time, in a power circuit. SOLUTION: This power switching circuit is equipped with transistors 15 and 17 for power switching and a transistor 16 for prevention of reverse flow, and the transistor 16 is connected so that the main power circuit 13 can supply a constant a voltage circuit 12 and a constant voltage circuit with voltage, and a transistor 17 is connected between the constant voltage circuit 12 and a backup circuit 11, and it is controlled to turn on at standby time and turn off at normal operation by a microcomputer 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for switching between a power supply in a normal operation and a power supply in a standby state, and mainly relates to a television device.

[0002]

2. Description of the Related Art During normal operation, a power supply is rectified through a relay and uses a voltage output by a switching circuit. In addition, the power supply at the time of standby uses the output voltage obtained by rectifying the AC voltage before the relay separated by a small-capacity transformer.

As a power supply switching circuit, for example, as proposed in Japanese Utility Model Laid-Open No. 4-134788, a backup system using a predetermined constant voltage circuit is also employed.

[0004]

However, in the conventional circuit system, in order to secure the operation of the image storage memory during standby, the amount of current of the load required to operate during standby increases, and the shape and shape of the transformer that separates the AC voltage are reduced. However, the size of the predetermined constant voltage circuit is increased, and the cost is increased.

[0005]

According to the present invention, in order to achieve the above object, a switching circuit is provided, and the operation of the memory is controlled by a microcomputer. According to the above configuration, it is possible to use a small-capacity separate transformer in the power supply circuit at the time of standby, thereby reducing the cost.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention controls the switching timing of the power supply by a microcomputer and switches the operation mode of the image storage memory to change the operation mode from normal operation to standby. This is a circuit of a system that constantly supplies power even when the power is switched.

According to a third aspect of the present invention, there is provided a power supply switching transistor and a reverse inflow prevention transistor, wherein the reverse inflow prevention transistor supplies a voltage to a constant voltage circuit and a constant voltage circuit in a main power supply circuit. And a power supply switching transistor connected between the constant voltage circuit and the backup circuit, and controlled by a microcomputer to be turned on during standby and turned off during normal operation. Thus, a small-capacity separate transformer can be used in the power supply circuit during standby, and the cost can be reduced.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a block diagram of a power supply switching circuit according to an embodiment of the present invention, and FIG. 2 is a power supply switching timing chart of FIG.

The power supply switching circuit of the present invention comprises power supply switching transistors 15, 17 and a reverse inflow prevention transistor 16, and the reverse inflow prevention transistor 1
6 is a constant voltage circuit 12 and a constant voltage circuit 1
4 is connected so as to supply a voltage, and the power supply switching transistor 17 is connected to the constant voltage circuit 12 and the backup circuit 11.
The microcomputer 18 controls the microcomputer 18 so that it is turned on during standby and turned off during normal operation.

At the time of normal operation, the voltage applied to the transistor 15 by the microcomputer 18 is kept low, the transistor 17 for the changeover switch is turned off, and the constant voltage circuit 1 is turned off.
2 and the constant voltage circuit 14 are supplied with voltage by the main power supply circuit 13. At the time of switching from the normal operation to the standby operation, as shown in FIG. 2A, before turning off the operation of the main power supply circuit, the microcomputer 19 first sets the video storage memory 20 to the standby mode.

Next, as shown in FIG. 2B, a HIGH signal is supplied from the microcomputer to the transistor 15, the transistor 17 for the changeover switch is turned on, and the backup circuit 11 is connected to the constant voltage circuit 12.

Thereafter, the operation of the main power supply circuit is turned off by the microcomputer 18 as shown in FIG. As a result, the voltage is constantly supplied to the constant voltage circuit 12 even when the state changes from the normal operation to the standby state.

When switching from the standby mode to the normal operation mode, the microcomputer 18 first turns on the main power supply circuit as shown in FIG. 2C. Next, as shown in FIG. 2B, the microcomputer 19 sets the image storage memory 20 to the normal operation mode.

Then, the transistor 1 is sent from the microcomputer 18.
5 is supplied with a LOW voltage, the connection between the backup circuit 11 and the constant voltage circuit 12 is cut off, and the main power supply circuit 13 supplies a voltage to the constant voltage circuit 12. Thereby, the voltage is supplied from the main power supply circuit 13 to the constant voltage circuit 12 and the constant voltage circuit 14 during the normal operation.

(Embodiment 2) The basic operation is as described in Embodiment 1.
Is the same as However, the timing of switching between the backup circuit 11 and the main power supply circuit 13 is not controlled by the microcomputer 18 but the voltage of the constant voltage circuit 14 is detected, and after the voltage drops below a predetermined voltage value, the backup circuit 11 and the main circuit 13 are switched. In this method, the transistor 11 is turned on so that the constant voltage circuit 12 is connected.

[0016]

According to the present invention, the power supply circuit used during standby can be reduced because the load required during standby can be reduced by switching the power supply circuit during normal operation and during standby. Thus, an inexpensive power supply circuit configuration is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply switching circuit according to an embodiment of the present invention.

FIG. 2 is a power supply switching timing chart of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 backup circuit 12 constant voltage circuit 13 main power supply circuit 14 constant voltage circuit 15 switching transistor 16 reverse inflow prevention transistor 17 power supply switching switch transistor 18 microcomputer 19 video storage memory control microcomputer 20 video storage memory 21 bias setting resistor 22 Bias setting resistor 23 Base current setting resistor 24 Reverse bias prevention resistor

Claims (3)

[Claims] 1. A power supply switching circuit, wherein a power supply in a normal operation and a power supply in a standby state are switched at a timing controlled by a microcomputer. 2. A power supply switching circuit, wherein a power supply switching timing is controlled by detecting a power supply used in a normal operation, and a power supply circuit is switched in a standby state. 3. A power supply switching transistor and a reverse inflow prevention transistor, wherein the reverse inflow prevention transistor is connected by a main power supply circuit so that a voltage can be supplied to a constant voltage circuit and a constant voltage circuit. A power supply switching circuit characterized in that a transistor is connected between the constant voltage circuit and the backup circuit, and is controlled by a microcomputer to be turned on during standby and turned off during normal operation.