JPH0726751Y2 - Electronic device with low battery detection function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an electronic device with a low battery detection function.

[Prior Art] Conventionally, in a small electronic device such as a handy terminal that uses a battery as a power source, a battery voltage detection circuit that detects a decrease in battery voltage is provided.

Fig. 5 shows a block circuit diagram of this kind of electronic equipment.
U11 has input / output circuit 12, ROM13, RAM1
In addition to 4, the voltage detection circuit 15 is connected. When the voltage detection circuit 15 detects that the battery voltage is equal to or lower than the predetermined operation guarantee voltage, the low voltage detection signal is given to the CPU 11 as an interrupt signal to notify the CPU 11 of the voltage drop.

Such a voltage detection circuit 15 is always operating, and a small amount of current is flowing through the internal comparator itself.
Therefore, there is a drawback that unnecessary current flows to the voltage detection circuit 15 when the CPU 11 and other devices are operating and not operating, resulting in wasted power consumption.

The problem of this invention is to effectively suppress the current consumed for detecting the battery voltage.

[Means for Solving the Problems] The means of this invention are as follows.

The voltage detection means 1 (see the block diagram of FIG. 1, the same applies hereinafter) is a low battery detection circuit that detects a voltage drop of the power supply battery.

The central processing unit 2 is a CPU that performs various processes according to a microprogram stored in advance.

The control means 3 controls the operation of the voltage detection means 1 based on whether or not the central processing unit 2 is operating, and detects the voltage when the central processing unit 2 is not operating, such as in a waiting state. The operation of the means 1 is prohibited.

[Operation] The operation of the means of this invention is as follows.

If the central processing unit 2 is operating now, the control means 3
Activates the voltage detection means 1. As a result, the voltage detecting means 1 detects the voltage drop of the power supply battery, and when a low battery is detected as a result, for example, the voltage detecting means 1
Notifies the central processing unit 2 to that effect.

Further, when the central processing unit 2 is not operating, for example, in a key input waiting state, the control means 3 prohibits the operation of the voltage detecting means 1.

As a result, when the central processing unit 2 is not operating, no unnecessary current is consumed for detecting the battery voltage drop, so that the current required for the detection can be minimized.

Therefore, the current consumed for detecting the battery voltage can be effectively suppressed.

[Embodiment] An embodiment will be described below with reference to FIGS. 2 to 4.

FIG. 2 is a block circuit diagram showing a small electronic device such as a handy terminal. The CPU 21 controls various operations in accordance with a microprogram stored in advance in the ROM 22, and the CPU 21 is connected to the ROM 22 as well as an input / output circuit 23, a RAM 24, and a voltage detection circuit 25.

The voltage detection circuit 25 has a normal configuration including a comparator, etc., and the battery voltage is supplied to the voltage detection circuit 25 via the gate circuit 26, and this battery voltage is a predetermined threshold voltage (of the CPU 21). When it reaches below the operation guarantee voltage), it gives an interrupt signal to the CPU 21 to inform it of the low battery state.

The gate circuit 26 is a switching transistor which is opened by an operating signal m indicating that the CPU 21 is operating, such as a read signal from the CPU 21, and controls the supply of the battery voltage to the voltage detection circuit 25. The CPU operating signal m is C
This is a signal that goes high when the PU21 is performing read / write processing, and goes low when it is not operating, such as when waiting for a key input.

Next, the operation of this embodiment will be described with reference to FIG.

Now, as shown in FIG. 3, the in-operation signal m output from the CPU 21 is a signal that repeats low level and high level in synchronization with the operation of the CPU 21, and becomes low level when the CPU 21 is not operating. . Therefore, in this case, the gate circuit 26 is closed to cut off the supply of the battery voltage to the voltage detection circuit 25. As a result, the voltage detection circuit 25 is in the operation stopped state when the operating signal m is at the low level.

Further, when the CPU 21 is in operation, the in-operation signal m is at a high level, and therefore the gate circuit 26 is opened, so that the battery voltage is supplied to the voltage detection circuit 25 and low battery detection is performed.

Such an operation is repeated according to the in-operation signal m from the CPU 21, and as a result, the voltage detection circuit 25 remains in the stopped state after a fixed time (several μsec) even if the low battery detection operation is started. As a result, the voltage detection circuit 25 performs the low battery detection operation for several μsec each time the CPU 21 operates, and the voltage detection circuit 2 operates when the CPU 21 is not operating.
The operation of 5 is stopped. Thus, even if the operation of the voltage detection circuit 25 is stopped while the CPU 21 is not operating, the battery effect during that time is small, and the operation is stopped for a few μsec. Therefore, as shown in FIG. When the voltage becomes equal to or lower than the threshold value, the low battery state is detected at the next operation timing of the voltage detection circuit 25, and the interrupt signal is given to the CPU 21.

FIG. 4 is a flow chart for explaining the operation of the CPU 21. Here, when the CPU 21 receives the interrupt signal from the voltage detection circuit 25, it notifies the low battery state and stops the process currently being executed.

That is, in the key input waiting state in step S1,
When there is a key input, the CPU 21 outputs the operating signal m to operate the voltage detection circuit 25 (step S2). Then, it is detected whether or not an interrupt signal is input from the voltage detection circuit 25 (step S3), and when no interrupt is detected, various processes corresponding to the key input (step S4) are performed, and then step Although the process returns to S1, if the presence of an interrupt is detected, the process proceeds to the interrupt processing routine accompanying the voltage drop.

In this interrupt process, the low battery state is displayed or an alarm sound is given in response to the interrupt signal from the voltage detection circuit 25, and the process currently being executed is stopped.

In this way, by stopping the processing of the CPU 21 in response to the low battery detection, it is possible to prevent erroneous processing.

The power supply battery may be a secondary battery in addition to the primary battery, and the battery voltage detection means detects the operation guarantee voltage of the display device, the printer, etc. in addition to the operation guarantee voltage of the CPU. It may be.

Further, in the electronic device having the clock circuit, the battery voltage detection operation may be performed at a constant timing in synchronization with the clock signal generated from the CPU.

[Effect of the Invention] This invention detects the battery voltage drop during the operation of the central processing unit, and stops the detection when the central processing unit is not operating. It is possible to suppress the consumed current as much as possible and prevent wasteful power consumption.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of the present invention, FIGS. 2 to 4 are embodiments, FIG. 2 is a block circuit diagram of an electronic device with a low battery detection function, and FIG. 3 is an electronic device with a low battery detection function. FIG. 4 is a time chart for explaining the operation of the device, FIG. 4 is a flow chart for explaining the operation of the CPU 21, and FIG. 5 is a diagram for explaining a conventional electronic device with a low battery detection function. 21 …… CPU, 22 …… ROM, 25 …… Voltage detection circuit, 26 …… Gate circuit, m …… Operating signal.

Claims (1)

[Scope of utility model registration request] 1. A voltage detecting means for detecting a battery voltage, a central processing unit for performing various kinds of processing, and a control for controlling the operation of the voltage detecting means based on whether or not the central processing unit is in operation. An electronic device with a low-battery detection function, characterized in that the control means prohibits the operation of the voltage detection means when the central processing unit is not operating.