JPS60176125A - Power supply voltage check circuit of microcomputer - Google Patents

Abstract

PURPOSE:To compare two voltage levels with an analog comparator circuit by using a voltage comparator in common for a voltage comparator circuit informing shortage of a battery and a voltage comparator circuit resetting a microcomputer. CONSTITUTION:A normal switch signal is generated from the microcomputer 11, inputted to a switch circuit 14 of a voltage comparator circuit 15 so as to switch the comparison voltage of the voltage comparator circuit 15. An output of the voltage comparator circuit 15 and a switch signal are inputted to a logical circuit 16. The microcomputer 11 performs various controls of a device 12 normally. When a voltage ed of a battery power 1 is lower than an informing voltage e2, an informing signal is inputted to the microcomputer 11 from the logical circuit 16 so as to raise a buzzer 13 for information. When the voltage ed is lower than the reset voltage e1, a reset signal is inputted to the microcomputer 11 from the logical circuit 16, which is reset and the device 12 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a power supply voltage check circuit for a microcomputer that controls equipment powered by a battery.Conventional structure and problems thereof Advent of CuO2 microcomputer This made it easy to drive microcontrollers with batteries. However, as shown in Figure 1, the battery voltage decreases over time, so in order to prevent the microconbeater from malfunctioning, when the battery voltage drops, the microconbeater is reset and the equipment is stopped before it malfunctions. There is a need to. However, since it can be inconvenient if the device suddenly stops, a notification is often sent to notify the user of battery life before resetting the microcomputer. A conventional example in which a microcomputer is reset when the reset signal is high is shown in Figure 2.A resistor 2 and a diode 3 are connected in series in parallel with a battery power source 1,
A resistor 5 and a resistor 6t connected in series are connected. The comparator 7 has a midpoint potential 1 between the resistor 2 and the diode 3.
a, the midpoint potential lb between resistor 4 and resistor 5 are input to the positive and negative input terminals, and comparator 8 receives midpoint potential 1° between resistor 2 and diode 3, and midpoint potential Jl? between resistor 5 and resistor 6. e is connected to be input to the positive and negative input terminals. Comparators 7 and 8 are generally well-known open collector type comparators. Resistor 9 pulls up the output voltage of comparator 7, and resistor 10 pulls up the output voltage of comparator 8. and the output terminal of the comparator 8.

The output of the comparator 7 is input to the reset terminal of the microcomputer 11 as a reset signal, and the output of the comparator 8 is input to the microcomputer 11 as a notification signal. The microcomputer 11 outputs a notification signal from a notification buzzer 13 and also controls various devices 12. When the output of the comparator 7 is low, the microcomputer 11 operates normally and controls the device 12, and when the output is high, the microcomputer 11 resets and stops the device 12. When the output of the comparator 8 is low, the microcomputer 11 does not notify, but when the output is high, the buzzer 13 sounds to notify.

When na=n+ I! When a=nb, #a=#g, Na
The constants of resistors 4 and 5.6 are determined so that = (lc).When 6a>h, nc>na, the output of comparator 8 is low and no alarm is output, and nb When '>6a, the output of the comparator 7 is low and the microcomputer 11 controls the device 12. e2>#d>'(l When l, llc<(l
At a, the output of 8 goes high to notify that the battery life is nearing 0 and at j? When b>#a, the output of the comparator 7 is low and the microcomputer 11 controls the device 12. J? d<J? When #b<#a, the output of the comparator 7 becomes high, the microcomputer 11 is reset, and the equipment 12 is stopped.

In this configuration, two analog comparison circuits are required, so the analog comparator consumes a large amount of current and consumes the battery, resulting in a shortened battery life.

OBJECTS OF THE INVENTION The present invention solves the problems of the conventional analog comparator circuit 1f! The purpose is to compare two voltage levels at 1 and reduce current consumption.

Structure of the Invention In order to achieve this object, the present invention has a voltage comparator circuit for comparing and detecting the voltage of the battery power supply, and a microcontroller for controlling battery-powered equipment. It has a switching circuit that periodically switches the comparison level between a reset voltage 12 and a notification voltage 12 according to the switching output of the computer, and the voltage comparison circuit divides into a reset signal and a notification signal according to the switching output of the microcomputer. The configuration is such that the output is output to a logic circuit that is input to a microcomputer. This configuration has the effect of reducing battery consumption by making the analog comparison circuit 1111!1[1.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. A switching signal is constantly generated from the microcomputer 11, and the voltage comparison circuit 1
5 to the switching circuit 14. The switching circuit 14 switches the comparison voltage of the voltage comparison circuit 15. Voltage comparison circuit 15
The output and switching signal are input to the logic circuit 16. Normally, the microcomputer 11 performs various controls on the equipment 12. When the voltage na of the battery power supply 1 becomes lower than 42 in Figure 1g1, a notification signal is input from the logic circuit 16 to the microcomputer 11, and the buzzer 13 sounds to notify the user.
When the level becomes lower, a reset signal is input from the logic circuit 16 to the microcomputer 11, and the microcomputer 11 resets the device 12.
If you stop it, it will hurt.

A specific example of the circuit is shown in FIG. In FIG. 4, parts that operate the same as those in FIG. 2 are given the same numbers.

A resistor 2 and a diode 3 connected in series are connected in parallel with the battery power source 1. Resistor 17 and Resistor 1
8 are connected in series, a resistor 18 is connected in parallel with the switching circuit 14, and a resistor 17.18 and the switching circuit 16 are connected to the battery power supply 1.
are connected in parallel. The midpoint configuration ge of resistors 17 and 18 and the midpoint potential of resistor 2 and diode 3 (la are input to the positive and negative input terminals of comparator 19. Comparator 19 is a commonly known open collector type comparator. The resistor 2o is used to pull up the output voltage of the comparator 19.

The microcomputer 11 always generates a switching signal as shown in FIG. 5, which is input to the resistor 21 and the inverter 22. The resistor 21 is connected in series with the resistor 23, and its midpoint potential 1t
is connected to the base of transistor 24, and transistor 2
The collector of resistor 4 is connected to resistor 25, and the other end of resistor 25 is connected to the midpoint of resistors 17 and 18. The output of the comparator 19 is between the microcomputer 11 (D notification signal input terminal and the inverter 2
Connected to 6. The inverter 22.26 is connected to the cathode of the diode 27.28, and the diode 27
．． The anode of 28 is connected to the positive side of the power supply via a resistor 29, and is also sent to the microcomputer 1 as a reset signal.
It is input to the reset terminal of 1. The microcomputer 11 outputs a notification signal from a notification buzzer 13 and performs various controls on the equipment 12. When the reset signal is low, the microcomputer 11 of the embodiment operates normally and controls the device 12, and when it is high, the microcomputer 11 resets and controls the device 12tl-.
It is configured to stop. When the notification signal output is high, the microcomputer 11 does not notify, and when it goes low, the buzzer 13 is activated.
The microcomputer 11 always generates a switching signal shown in FIG. When the switching signal is high, the transistor 24 is turned on,
The resistor 18 and the resistor 25 are placed in parallel. When the switching signal is low, transistor 24 is turned off and resistor 18 and resistor 2
5 is in a disconnected state.・Therefore, as shown in FIG. 6, when the switching signal 11e is low (le = (le l
+When the switching signal is high (le=(le2(net >(
le2). When nd=li, na=(J e r
+ J? The constants of the resistors 17, 18, and 25 are determined so that when d = E 2 (la = lJez).

When ed>e2, regardless of whether the switching signal is high or low (
le>(la, the notification signal that is the output of the comparator 19 becomes high and does not notify. Also, the output of the inverter 26 becomes low, so the switching signal is high and the rotary inverter 2
Even if the output of 2 switches, the reset signal is low.

When 12>ld>l+, the notification signal becomes low when the switching signal is high, and it is notified that the battery life is approaching. The output of the inverter 26 becomes high, but since the output of the inverter 22 is also low, the reset signal becomes low. When the switching signal is low, the output of comparator 19 is high, and inverter 2
6 becomes low, so the output of inverter 22 becomes high, but the reset signal remains low.

When 11a<llI, the switching signal changes between high and low, the output of the comparator 19 remains low, and the output of the inverter 26 becomes high. Here, when the switching signal becomes low, the output of the inverter 22 also becomes high, the reset signal becomes high, the microcomputer 11 is reset, and the equipment 12 is stopped. The output voltages of the comparator 19, inverter 22, and inverter 26, and the high and low voltages of the notification signal and reset signal are shown in the following table.

In the embodiment shown in Figure fI4, the inverters 22 and 26 and the microcomputer 11 use 0MO5-ICs, and the current consumed by these is extremely small, about 1% compared to the current consumed by the voltage comparison circuit 19. /10.

Effects of the Invention As described above, the present invention shares the voltage comparison circuit for notifying the battery consumption and the voltage comparison circuit for resetting the microcomputers, and uses a logic circuit. Since the configuration is such that the notification signal and reset signal are input to the microcomputer, the number of analog voltage comparison circuits is reduced by one, which has the effect of reducing current consumption and extending battery life.

[Brief explanation of drawings]

tJ! Ji diagram is a characteristic diagram showing the time change of battery voltage, Figure 2 is a circuit diagram of a conventional microcomputer power supply voltage check circuit, and fJ3 diagram is a microcomputer power supply voltage check circuit showing an embodiment of the present invention. A block diagram of the circuit, Fig. 4 is a circuit diagram showing a specific example of the same circuit, Fig. 5 is a timing diagram showing a microcomputer switching signal, f
Figure J6 is a timing diagram showing the positive input voltage of the comparator. 1...Battery power source, 11...Microcomputer, 12...Device, 14...
Switching circuit, 15...Voltage comparison circuit, 16...
...Name of logic circuit representative: Patent attorney Toshio Nakao and one other person Figure 1

Claims (1)

[Claims] A microcontroller that controls equipment using battery power and the electric/ll! The voltage comparison circuit includes a voltage comparison circuit that compares and detects the voltage of the power supply, and the voltage comparison circuit includes a switching circuit that periodically switches the comparison level between the reset voltage digit and the alarm voltage cape based on the switching output of the microconbeater. , the voltage comparator circuit is configured to divide into a reset signal and a notification signal according to the switching output of the microconbeater, and output the signal to a logic circuit input to the microconbeater.The power supply voltage of the microconbeater is checked. circuit.