JPH05336655A - Power supply control circuit - Google Patents

Abstract

PURPOSE:To prevent useless power consumption of battery when power is turned OFF by employing power devices of low power consumption in the constitution of power supply circuit for feeding a control reference voltage generating circuit with power from a battery through a power switch of portable terminal. CONSTITUTION:ON signal for a power switch 22 is latched at a latch section until the power switch 22 is turned OFF and then a buffer IC 24 is driven thus feeding a reference voltage generating IC 25 with power only when a main power supply is turned ON. The latch circuit 23 and the buffer IC are constituted of C-MOS devices of very low power consumption. Since the power supply circuit scarcely consume power when the main power supply is turned OFF, load on the battery power supply is reduced and operating time of the device is prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control circuit for controlling a power supply supplied to a portable terminal.

[0002]

2. Description of the Related Art A conventional power supply control circuit includes a switching element (Tr, FET, etc.) for controlling power supply to a circuit portion of a portable terminal, a control LSI for controlling the switching element, and a control LSI for each operation. It is composed of a reference voltage generation unit serving as a reference. Also, since the battery is used as the power source, the control LSI has a power supply prohibition function when the battery voltage drops, and a battery voltage when the battery voltage drops, for the purpose of avoiding malfunction of the portable terminal 0 circuit part when the voltage drops when the battery is exhausted. It is equipped with a function to generate a power supply alarm signal as a battery voltage monitoring signal by software when the voltage drops.

FIG. 2 is a block diagram of an example of a conventional power supply control circuit. In the conventional example, 11 is a Ni-Cd battery,
12 is a reference voltage generation IC, 13 is a power supply control LSI, 14
Is a power switch, 15 is a power ON / OFF control block inside 13, 16 is a power alarm generation block inside 13,
Reference numeral 17 is a power supply switching transistor, 18 is a portable terminal logic circuit section, and 19 is an LCD panel section. Supply of power from 11 to each unit device of the portable terminal such as 18 and 19 is controlled by 13 LSIs. 13 is a reference voltage generation IC of 12.
All power supply control is executed based on the reference voltage generated by. When the power supply SW of 14 is turned on, LO at that time
The W level pulse signal is input to 13, and 13 turns on the transistor 17 and supplies the power from 11 to 18 and 19. At that time, 15 block parts inside 13 monitor the collector output voltage of 17 (supply voltage to 18, 19) on the basis of the reference voltage from 12, and when the collector voltage value is below a certain voltage level, Turn off the 17th transistor to avoid abnormal operation of 19th and 19th low voltage
To stop the power supply. That is, when the battery voltage level of 11 is below a certain voltage level, the portable terminal body is controlled so as not to be turned on. In addition, 16 blocks in 13 are powered by SW ON 14 to supply power to 18 and 19, and then when the battery of 11 is exhausted and the voltage level is lowered, 17 blocks based on the reference voltage of 12 are generated. It has a function of generating a power supply alarm signal when the collector output voltage of is monitored below a certain voltage level. There are several types of generated power supply alarm signals depending on the level of the monitored voltage level. (In Fig. 2, two types, ALM1 and ALM2, are shown.) This alarm signal is monitored by software, and the low power supply voltage level is set by limiting or stopping the operation of the main body logic circuit system for each alarm signal generation voltage level. It is possible to prevent the malfunction of the main body Logic circuit system at that time.

As described above, in the conventional example, since the 12 reference voltage generating ICs are directly connected to the battery power source of 11, the current is constantly consumed at 12 even when the portable terminal main body is in a power-off state, and the consumption of the battery 11 is accelerated. Will end up.

[0005]

In this conventional power supply control circuit, the current is constantly consumed when the battery power supply is connected in the reference voltage generation section which is the operation base of the control LSI, so that the power supply of the main body is Even in the OFF state, the battery is always exhausted and the actual operation time of the main body is shortened.

[0006]

The power supply control circuit of the present invention is a power supply control circuit for a portable terminal which operates on a battery, wherein a power supply from the battery is supplied to a reference voltage generation circuit for control. And a power supply circuit which supplies the power source according to the present invention, and the power supply circuit is configured by a low power consumption type device.

[0007]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.

In this embodiment, 21 is a Ni-Cd battery, 22 is a power switch (SW), 23 is a latch circuit,
Reference numeral 24 is a buffer IC, 25 is a reference voltage generation IC, 26 is a power supply control LSI, 27 is a power supply control unit, 28 is a power supply alarm generation block, 29 is a power supply switching transistor, 30 is a portable terminal logic circuit, and 31 is an LCD. It is a panel.

When the power source SW22 is turned on, the power source control LS
Transistor 29 is turned on by I26 and logic circuit 3
0 and the LCD panel unit 31 are supplied with power. Battery 2
1 logic when the power supply voltage level of 1 is low (Log
ic) A power-on prohibiting function under the control of the power supply control unit 27 for protecting the malfunction of the circuit units 30 and 31, and a main body Logic when the output voltage of the collector of the transistor 29 decreases due to the exhaustion of the battery 21 during the main body operation. The operation of each part of the series of power supply alarm signal generation functions under the control of the alarm generation part 28 for protecting the malfunction of the circuit parts 30 and 31 is the same as that of the conventional power supply control circuit described above.

According to the method for supplying power to the reference voltage generating IC of this embodiment, when the power SW 22 is turned on, it is turned on.
The signal is input to the power supply control LSI 26 and becomes a trigger signal for starting the main body power supply control, but at the same time, the ON signal is the latch circuit 2.
Input to 3. The power supply SW22 of the latch circuit 23 is ON
It has a function of latching the ON signal and continuously outputting the HIGH level signal from the time it is turned on until the time it is turned off next time. The HIGH level signal output from the latch circuit 23 is input to the buffer IC 24 and is input to the reference voltage generation IC 2
5 supplies power to the reference voltage generation IC 25 while the HIGH level signal of the latch circuit 23 is output.

In this way, the reference voltage generation IC 25 is supplied only when the power supply SW22 is turned on and the portable terminal main body is in the power-on state, so the reference voltage generation IC 25, which has been a problem in the conventional example. Therefore, the current is not always consumed. Also, the logic circuit 3
0 and the power supply control LSI 26 have a C-MOS device internal structure, the current consumption when not in operation (portable terminal main body power OFF state) is very small on the order of μA. Therefore, a portable terminal powered by a battery is used. In, the actual operation time can be lengthened.

[0012]

As described above, according to the present invention, in the reference voltage generating circuit section which constantly consumes current in the power supply control circuit, the battery power is supplied only when the power supply of the portable terminal main body is turned on. The current consumption when turned off is extremely small, the load of the battery as the power source is reduced, and the actual operation time of the main body is extended.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an example of a conventional power supply control circuit.

[Explanation of symbols]

 21 battery 22 power supply SW 23 latch circuit 24 buffer IC 25 reference voltage generation IC 26 power supply control LSI 27 power supply control unit 28 power supply alarm generation unit 29 transistor 30 logic circuit unit 31 LCD panel

Claims (1)

[Claims] 1. A power supply control circuit for a portable terminal operated by a battery, comprising a power supply circuit for supplying power from the battery to a control reference voltage generation circuit by a power switch of the portable terminal,
A power supply control circuit comprising the power supply circuit as a low power consumption device.