JPH08314552A - Power supply circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] Starting the stabilizing voltage generation unit that supplies the stabilizing power supply voltage to the control unit to start the control unit, and then controlling the driving of the stabilizing voltage generation unit by the control unit itself. Improvement that also acts as a measure against momentary interruption of the power supply circuit. [Structure] A voltage detection circuit 4 that produces a HiZ output when a power-on switch SW is pressed, a differentiation circuit 5 that generates a differential output by the Hiz output of the voltage detection circuit 4, and a transistor switch that is turned on for a certain time by the differential output. 6 is provided, and the voltage generation circuit 3 uses the output of the transistor switch 6 for a fixed time
To start.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a power supply whose voltage fluctuates and holds the drive of a stabilized voltage generation unit for generating a stabilized voltage supplied from the power supply voltage to the control unit by the control unit itself. In addition, the present invention relates to a power supply circuit in which the control unit itself stops driving the stabilized voltage generation unit when the power is turned off. The product to which the present invention is applicable is preferably an electronic device that uses a battery as a power source and a CPU as a control unit, and examples thereof include small electronic devices such as mobile phones.

[0002]

2. Description of the Related Art An electronic device using a battery is provided with a stabilizing voltage generator for generating a stabilized power source voltage for each block such as a CPU system block which is driven by different power source voltages in the device. In the case of equipment, one CPU controls the drive of each stabilized voltage generator,
The stabilized voltage generator that supplies the stabilized power supply voltage to the CPU must also control its driving by the CPU itself. Therefore, when the power is turned on, a circuit for generating an activation signal for activating the stabilized voltage generator of the CPU block is provided. The start-up signal activates the stabilized voltage generator of the CPU system block, the generated stabilized power supply voltage causes the CPU to reset and enter the initial state, and the control signal for driving each stabilized voltage generator is input. Start. After that, the CPU holds the driving of each stabilized voltage generation unit.

[0003]

A flip-flop is used for the circuit for generating the activation signal for activating the stabilized voltage generation unit of the CPU system block when the power is turned on as described above.

However, since the flip-flop is composed of a plurality of logic gates, the number of parts is large. Further, the logic gate has a large dark current even when the power switch is turned off, and is not suitable for reducing the power consumption of the device.

Further, in the case of a portable device, due to a shock such as vibration, the battery terminals are momentarily disconnected (10 ms or less) and the power is cut off, and the power is turned on again (hereinafter, such a state is momentarily cut off). However, at this time, the stabilized voltage generation unit of the CPU system block cannot instantaneously generate the voltage to be supplied, so that the CP
The drive of U was also stopped, and there was a risk that the CPU would remain stopped even if the momentary interruption was recovered. Therefore, as a measure against momentary interruption, it is necessary to re-configure the activation signal to be output to the stabilized voltage generation unit upon recovery from momentary interruption. However, the flip-flop itself has a large number of parts, and such a countermeasure is provided. And the number of parts will increase further.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a power-on switch circuit, a voltage detection circuit for generating an output at a voltage value higher than a predetermined value, and an output of the voltage detection circuit. And a starting signal generating circuit for generating a starting signal for a certain period of time by the differentiating signal, and the stabilizing voltage generating circuit of the CPU block is started by this starting signal.

[0007]

Since the voltage detection circuit produces an output when the power supply voltage is turned on or when the power is restored from an instantaneous interruption, the differential signal produced by this output produces an activation signal for a certain period of time to activate the stabilizing voltage generation unit of the CPU block. It

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, which comprises a battery 1, a power-on switch circuit 2, a stabilized voltage generation circuit 3 for a CPU block, a voltage detection circuit 4, a differentiating circuit 5, a transistor switch 6, and a CPU 7. . The voltage generation circuit 3 is driven by the "H" signal as a drive signal. The voltage detection circuit 4 is an open collector type output using CMOS, and outputs HiZ when the input is "H", and outputs 0V when the input is "L". Transistor switch 6 is R5 and Tr
It consists of an "L" output switch consisting of 2 and an inverting switch consisting of R6, R7 and Tr3 which inverts this output to an "H" output, and the "H" output is generated for a certain period of time at the output of the differentiating circuit 5, and this produces voltage It becomes the activation signal of the circuit 3. R3 is used as a pull apple resistor because the voltage detection circuit 4 has an open collector type output. The diode D2 and the resistor R9 are for level shifting with the CPU 7. Similarly, the diode D3 is also for level shifting with the CPU 7.

With the above configuration, when the power-on switch SW is pressed while the battery 1 is set in the device, the power-on switch circuit 2 is turned on. As a result, the power supply voltage is supplied to the voltage detection circuit 4, so that the voltage detection circuit 4 becomes a HiZ output, a differentiation signal is generated in the differentiation circuit 5, and the transistor switch 6 is kept for a certain time (100 mS).
It is turned on. With this, the transistor switch 6
The H "output is generated for a certain period of time, which activates the voltage generating circuit 3. The activation supplies the stabilized power supply voltage to the CPU 7, and the CPU 7 shifts to the reset and initial state within the certain period of time, and then" H ". Control signal of the voltage generation circuit 3
Output to. After that, the CPU 7 controls the voltage generation circuit 3. When the power switch SW is pressed again in this state, the voltage is pulled through the diode D2 due to grounding, and the CPU 7 detects the level shift and outputs the control signal to the voltage generation circuit 3 as "L", so that the voltage generation circuit 3 is stopped, and the power supply to the CPU 3 is also stopped.

With the above configuration, the voltage detection circuit 4 outputs HiZ when the power is turned on or the momentary interruption is restored, and the differentiation signal is generated by the differentiation circuit 5 to turn on the transistor switch 6 for a certain time. While the drive of the generation circuit 3 is held by the CPU 7, the circuit that generates the signal that activates the voltage generation circuit 3 does not consume current.

In the above embodiment, R1, R2,
Power-on switch circuit 2 consisting of Tr1, R5, Tr2
The switch composed of R6, R7, and Tr3 can be composed of an analog switch or an inverter.
Further, in the present embodiment, the voltage generation circuit 3 operates by "H"("H" active), but when using the type that operates by "L"("L" active), R6 is used. , R7 and Tr3 are unnecessary, the collector of Tr2 may be directly connected to the line of the battery 1, and R8 may be changed from pull-down to pull-up.

[0012]

Since no flip-flop is required,
It can be configured with a small number of parts and is suitable for downsizing and cost reduction of equipment.

Since it is possible to construct without using any logic gate, the dark current can be made almost zero,
Suitable for low power consumption.

Even if a momentary interruption occurs, it is possible to immediately shift to drive control of the stabilized power supply generation circuit by the CPU after recovery from the momentary interruption.

[Brief description of drawings]

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

[Explanation of symbols]

 1: Battery 2: Power-on switch circuit 3: Voltage generation circuit 4: Voltage detection circuit 5: Differentiation circuit 6: Transistor switch (starting signal generation unit) 7: CPU

Claims (1)

[Claims] 1. A power-on switch circuit, a voltage detection circuit that detects a power-supply voltage and generates an output when the power-on switch circuit is turned on, and a differentiation circuit that generates a differential signal by the output of the voltage detection circuit. A start-up signal generation circuit that generates a start-up signal for a certain period of time based on the differential signal; and a stabilized voltage generation circuit that generates a stabilized voltage to be supplied to a control circuit based on a power supply voltage. The stabilized voltage generation circuit is activated by the activation signal generated for a certain time when is turned on, and the control circuit generates the stabilized voltage by the voltage generated by the stabilized voltage generation circuit within the activation signal generation time. A power supply circuit, characterized in that a control signal for driving the circuit is started.