JPH0149967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power control circuit in which most of the power control is under the control of a CPU (central processing unit).

Systems for driving portable radio cassette recorders, video tape recorders, etc.
It is necessary to reduce power consumption when using a battery power supply, and various power saving circuits are built in. However, when recording standby is required in the tape loading state, such as with a video tape recorder, the loading mechanism etc. must be kept energized. It is necessary to keep it. However, in conventional power supply control circuits, the system and power supply are simply connected directly via a self-holding type (hereinafter referred to as "alternate type") power switch. The operator has to turn off the power switch frequently, which places a heavy burden on the operator.
There are drawbacks such as the risk of serious damage to the tape if the operator accidentally turns off the power switch when power to the system should not be cut off, such as during tape loading. It was hot.

The present invention eliminates the above drawback by providing a power switch controlled by the CPU between the power supply and the system so that the CPU can control the power supply to the system after the power switch is turned on. The CPU powers the system only when necessary, and if the CPU determines that it is necessary to power the system, the system remains powered, even if the reset switch is pressed. The purpose of this invention is to provide a power supply control circuit with improved performance.

To achieve this objective, the present invention provides a power switch connected to a power supply via a momentary type power switch.
It is connected to the power supply via the CPU and an alternate type power switch, and together with the power switch
Allows systems whose operation is controlled by the CPU and power supply from the power switch to the CPU.
It consists of a diode that prevents the opposite, and a reset switch that is connected to the interrupt input terminal of the CPU and inputs a command to open the power switch.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the power supply control circuit of the present invention, and FIGS. 2A to 2F are signal waveform diagrams of various parts of the circuit to explain its operation.

In FIG. 1, reference numeral 1 denotes a portable video tape recorder, which has a built-in power source 2 consisting of a rechargeable battery or the like. Reference numeral 3 denotes a system that applies electricity to all objects including the video tape loading mechanism, rotary head drive mechanism, etc., and all operations are controlled by the CPU 4.

Here, the power supply 2 is connected via the power switch 5.
It is connected to the CPU 4 and to the system 3 via a large capacity power switch 6. The power switch 5 is a momentary type switch that closes only while it is pressed, but the power switch 6 is an alternate type, and is closed or opened by excitation and demagnetization of a power relay 7 controlled by the CPU 4. do. Therefore, the power relay 7 includes an opening coil 7a and a closing coil 7b of the power switch 6.
are provided with buffer circuits 17a and 17b, respectively.
It is connected to CPU4 via.

In addition, even after the power switch 5 is turned on, the CPU
In order to ensure power supply to 4, a diode 8 for backflow prevention is connected to the line 31 branched from the middle of the power line 61 connecting the power switch 6 and the system 3.
It is connected to the power supply terminal V _DD of CPU4 via.

On the other hand, the reset switch 9 for stopping the operation of the CPU 4 and the system 3 is connected to the inverter 10.
By closing the reset switch 9, a reset signal (a command to open the power switch 6) can be supplied to the interrupt input terminal INT.

Below, power supply control circuit 1 having the above configuration
Operation 1 will be explained in conjunction with Figure 2 A to F.

First, when the power switch 5 is closed while neither the CPU 4 nor the system 3 is operating at all, the CPU 4 is energized and starts operating as shown in FIG.
It is carried out by.

Once the CPU 4 is activated, the CPU 4 confirms that the system 3 is ready to receive power, and then
The closing coil 7b is energized and excited. the result,
The power switch 6 is closed, and the system 3 is now energized for the first time. Of course, the time required for the CPU 4 to confirm is short, and the confirmation is completed within a short period of time when the power switch 5 is closed.

By closing the power switch 6, various mechanisms in the system 3 are supplied with power, and the CPU
It begins to operate based on commands from 4.
Further, the CPU 4 is also supplied with power through the power switch 6 instead of the power switch 5.

In addition, since the diode 8 is provided, the problem that the system 3 is activated at the same time as the power switch 5 is closed without waiting for confirmation from the CPU 4 does not occur. Further, the monitoring of the system 3 by the CPU 4 is performed continuously during the operating period of the CPU 4,
If the CPU 4 determines that there is no need to energize the system 3, the opening coil 7a is energized and excited.
The power switch 6 is opened and power to the system 3 is cut off.

Furthermore, even if the operator accidentally closes the reset switch 9 even though the video tape recorder 1 is in the recording standby state and the tape loading mechanism is in operation, the CPU 4 If it is determined that it is necessary to energize the system 3, the power switch 6 is kept closed. Therefore, the inconvenience that the power supply 2 is turned off while the tape is still in the loading state does not occur. In such a case, the CPU 4 issues a command to cancel tape loading, and opens the power switch 6 after tape loading is canceled.

When the system 3 does not require energization, the reset switch 9 is closed and the opening coil 7a is energized and the power switch 6 is turned on.
At the same time as the opening of the CPU 4 and system 3, the power supply 2
It is cut off from the power source and stops operating.

In this way, in the power control circuit 11 having the above configuration, the power switch 5 itself is
For CPU 4, only for a short period of time at the beginning of its operation,
Since it only needs to supply a small amount of current, it does not need to have a large capacity at all, and therefore, even if it is incorporated into the video tape recorder 1, there are almost no restrictions on implementation. In addition, since these components are small and have a small capacity, a free layout of components is possible.

In addition, since all power supply to the system 3 is under the control of the CPU 4, the power supply can be cut off by a command from the CPU 4 without the operator having to perform a reset operation every time except when necessary.

Note that in the above embodiment, the application of the power supply control circuit 11 is of course not limited to the portable video tape recorder 1.

As explained above, according to the power supply control circuit of the present invention, the momentary type power switch may be of a small capacity and small size as long as it can carry enough current to operate the central processing unit. Therefore, the mounting location can be laid out freely, and since the power to the system is controlled by the opening/closing of the power switch by the central processing unit, the system can be installed without any reset operation by the operator.
If the central processing unit determines that energization is not necessary,
Power to the system can be cut off automatically, which enables power-saving system design.
Furthermore, even if a reset signal is interrupted to the central processing unit, depending on the state of the system, the power switch may be disabled for a certain period of time or until certain conditions are met, depending on the system state. It has excellent effects such as being able to postpone development.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the power supply control circuit of the present invention, and FIGS. 2A to 2F are signal waveform diagrams of various parts of the circuit to explain its operation. 1... Portable video tape recorder, 2... Power supply, 3... System, 4... CPU, 5... Power switch, 6... Power switch, 7... Power relay, 8
...Diode, 9...Reset switch, 10...Inverter, 11...Power control circuit.

Claims (1)

[Claims] 1. In an electronic equipment system controlled by a central processing unit, driving power is supplied to the central processing unit by turning on a momentary power switch, and the central processing unit A power supply control circuit that supplies driving power to the electronic equipment system by turning on a controlled self-holding power switch, the power supply control circuit branching the driving power supplied to the electronic equipment system to the central power switch. By providing a unidirectional power line that supplies driving power to the processing device and a reset switch that instructs the central processing unit to open the power supply line of the power switch, the electronic device A power supply control circuit characterized in that cutoff or supply control of power supplied to the system is placed under the control of the central processing unit.