JPH07306726A - Power-on control circuit - Google Patents

Abstract

PURPOSE:To reduce the current consumption of a battery by eliminating a backup current at power-off time which is required before to turn on and off a power source. CONSTITUTION:With a switch 1 in the circuit closed once, a 1st switching element 2 and a 2nd switching element 3 conduct and a control signal SC becomes active, but even when the switch 1 is opened thereafter, the gate of the 1st switching element 2 is held continuously at a high level with a voltage divided by resistances 10 and 11, so the element 2 stays turned on and the 2nd switching element 3 still conducts, so that the control signal SC is continuously active. When the gate of a 3rd switching element 4 is held at a high level with a power-off signal SO, the element conducts, the gate of the 1st switching element 2 which is at the high level so far goes down to a low level, the element turns off so the 2nd switching element 3 also turns off, so that the control signal becomes in active.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-on control circuit for portable equipment, and more particularly to a power-on control circuit for reducing current consumption.

[0002]

2. Description of the Related Art Normally, a portable device is required to perform processing such as file closing immediately before the power is turned off. Therefore, even if the power switch is physically turned off, the power is turned off by software after the processing is finished. It controls the disconnection.

Conventionally, for such control, as shown in FIG. 2, a switch 1 for generating a trigger pulse ST by an operator operating at power-on and power-off, and a trigger pulse ST.
Is supplied, the state of the control signal SI for controlling the state of the power supply is transited, and the flip-flop 20 for holding the state is included. FIG. 3 is an operation truth table of the flip-flop 20. When the power is turned off, the switch 1 is temporarily closed, and the trigger pulse ST is output to the flip-flop 20 and also to the main control unit 3. When the main control unit 3 detects this, processing such as file closing is performed. When the processing is completed, the software outputs the power-off signal SO when the processing is completed, and finally the power-off is controlled by the signal SC.

When the power is turned on, the switch 1 is temporarily closed again, and the trigger pulse ST generated thereby changes from the OFF state held by the flip-flop 20 to the ON state and the power is turned on.

As described above, the power is turned on and off each time the switch 1 is closed, and at the time of disconnection, the main control unit 30 outputs the disconnection signal SO for turning off the power after the control signal SI of the flip-flop 2 is delayed. Output.

[0006]

In this conventional power-on control circuit for portable equipment, a flip-flop is used for control, and this flip-flop is supplied with a trigger pulse generated when the power is turned on, and the flip-flop is supplied to the power source. In order to change the state of the control signal SI from the power-off state to the power-on state, it is necessary to hold the state even when the power is off. Therefore, the flip-flop needs to be energized at all times even when the power is turned off, and a battery is used as a backup source to back it up.

In portable equipment, a DC-DC converter is mainly used as a main power source. In that case, the battery is used as a primary side input of the DC-DC converter. Therefore, if the control circuit is configured as described above, the current consumption of the battery is increased by the backup current of the flip-flop, which causes a problem that the battery is consumed quickly.

An object of the present invention is to provide a power-on control circuit that does not consume backup current when power is turned off.

[0009]

The power-on control circuit of the present invention includes a switch that is temporarily closed by an operation, a first switching element that is conductive when the switch is closed, and a conductive state of the first switching element. The second switching element that conducts and the second switching element conducts, so that the input of the first switching element is kept at a high level, the first conduction control circuit that keeps conducting, and the first switching element A second conduction control circuit for setting the input to a low level to make it non-conductive, and instructing power-on by conduction of the second switching element.

In the present invention, the external signal is generated with a certain time delay by closing the switch that conducts the first switching element every other time.

The second conduction control circuit may be a third switching element which conducts when a high level is applied by an external signal.

[0012]

According to the present invention, by turning on the switch once, the first switching element and the second switching element are kept in the conducting state, and the third switching element is conducted from the outside, so that the conducting state is maintained until then. The first switching element and the second switching element are configured to be in a non-conducting state.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In FIG. 1, when the power is turned on, the switch 1 is closed for a certain period of time to generate a trigger pulse ST. While the trigger pulse is being generated, that is, while the switch 1 is closed, the voltage of the battery 9 changes to the resistance 5
And the voltage is divided by 6 and the gate of the first switching element 2 becomes high level. Then, the first switching element 2 becomes conductive, and the gate of the second switching element 3 connected to the drain of the first switching element 2 becomes low level, so that the second switching element 3 also becomes conductive and the control signal SC of the power supply (not shown) is supplied. Becomes active.

Here, even if the switch 1 is opened, the voltage divided by the resistors 10 and 11 which are the first conduction control circuit keeps the gate of the first switching element 2 at the high level, so that it continues to conduct. Therefore, the second switching element 3 also continues to conduct, and even if the switch 1 opens as a result, the control signal SC continues to be active and the power supply circuit (not shown) continues to operate. At this time, the diodes 7 and 8 both serve to prevent backflow. Also, resistors 5, 6 and resistors 10,
Reference numeral 11 is a resistance value that generates a voltage level that allows the first switching element 2 to conduct, and can be deleted depending on the voltage of the battery 9.

When the power supply is cut off, the power supply cut-off signal SO is supplied as a signal from the outside, and when the gate of the third switching element 4 becomes high level by this, the third switching element 4 which is the second conduction control circuit becomes conductive. To do. Therefore, the first switching element 2 that was at the high level until then
Gate becomes low level and becomes non-conductive. Therefore, the second switching element 3 is also turned off and the battery 9 is turned off. This results in the control signal SC
Becomes inactive, and the power supply circuit (not shown) stops the power supply. After the trigger pulse ST generated when the switch 1 is closed for the second time or the even number of times is input to the main control unit 30, the main control unit 30 determines that the power is off, and after performing various processes such as file closing. , Power off signal SO
To occur. That is, the power-off signal SO is generated with a delay of a certain time when the switch 1 is closed for an even number of times. When the power is off, the power to the main controller 30 is also off, so the trigger pulse ST is ignored and only the closing operation is performed.

When the circuit is constructed as in this embodiment, no current flows in this circuit when the power is off, and the battery 9 is only required when the power is turned on and for driving the apparatus.

Although the field effect transistor has been described as the switching element in the present embodiment, the present circuit can be constructed with other switching elements.

[0019]

As described above, according to the present invention, since it is not necessary to use a flip-flop as in the conventional case, a backup power supply is not needed. Furthermore, when the power is off, no current flows in the circuit of the present invention,
The current consumption of the battery can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional control circuit.

FIG. 3 is a truth table showing the operation of a flip-flop used in a conventional control circuit.

[Explanation of symbols]

 1 Switch 2 1st switching element 3 2nd switching element 4 3rd switching element 9 Battery 20 Flip-flop

Claims (2)

[Claims] 1. A switch that is temporarily closed by an operation, a first switching element that is conductive when the switch is closed, a second switching element that is conductive when the first switching element is conductive, and the second switch.
A first conduction control circuit that keeps the input of the first switching element at a high level and keeps the conduction by the conduction of the switching element, and a second conduction control circuit that makes the input of the first switching element non-conductive by an external signal. A power-on control circuit, comprising a conduction control circuit, and instructing power-on by conduction of the second switching element. 2. The power-on control circuit according to claim 1, wherein the external signal is generated with a certain time delay by closing the switch every other time.