JPS59206774A - Detecting and displaying circuit of power supply voltage - Google Patents

Abstract

PURPOSE:To display the state of the voltage of one power supply by the other power supply when its voltage is reduced by providing a power supply for detecting the variation of a power supply voltage and a power supply for driving a display part independently. CONSTITUTION:It is supposed that the power supplies A4, A5 are formed and the power supply A4 has larger current consumption and its power supply voltage is precedently reduced. The variation of the power supply voltage of the power supply A4 is applied to the base of a transistor (TR)13 through a constant voltage diode 11 and amplified. A diode (D)12 is set up so that the load of the TR13 is suddenly increased at a part close to the lower limit value of the power supply voltage of the power supply A4 and a constant voltage diode 14 fixes the emitter voltage of the TR13. A CMOS inverter 15 operates surely at the lower limit vaue of the power supply voltage, and when the output of the inverter 15 is inverted, a TR17 is turned on, an LED16 lights up and the voltage reduction of the power supply A4 is displayed. The LED16 is turned on by the power supply B5 and the consumed status of both power supplies A4, B5 can be uniformed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a power supply voltage detection and display device that detects the terminal voltage of a battery and displays the voltage level in an electronic device that uses a battery and aims at low power consumption. Conventional groove structure and its problems Recently, there has been a demand for electronic devices with low power consumption, and more and more devices are battery-operated. The ideal battery to use is one whose capacity becomes zero when the terminal voltage falls below a certain level.

However, during use of a battery, the terminal voltage generally tends to decrease gradually. Therefore, it is necessary to constantly monitor the battery capacity (terminal voltage) so that the device can be used in a normal state. In these electronic devices, the conventional method for detecting the power supply voltage is to compare the voltage VB from the power supply 1 and the voltage VR from the separately provided reference power supply 2, as shown in FIG. When the voltage becomes R, a method has been adopted in which the voltage ratio circuit 3 is operated, the output thereof is used to detect a drop in the power supply voltage, and a display or alarm is issued. This method has the following two drawbacks.

■ A voltage comparator (linear IC) is used as a detector, and when the power supply voltage VB and the reference voltage VR match, that is, the voltage detector constantly consumes a certain amount of current even when it is not in the detection operation, resulting in wasted current. be.

■ While the power consumption of electronic devices as a whole is decreasing, it is not possible to reduce the current consumed by the voltage detection circuit.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks of the conventional technology.The present invention suppresses the current consumed by the voltage detection circuit except when a drop in power supply voltage is detected, and when a drop in power supply voltage is detected, it reduces the current consumption of the battery. An object of the present invention is to provide a power supply voltage detection circuit that indicates consumption.

Structure of the Invention The present invention provides separate batteries to obtain a plurality of power supply voltages, and a voltage fluctuation amplifying section that amplifies fluctuations in the power supply voltage of one battery, and when the output of this voltage fluctuation section exceeds a certain level. and a display section that displays a decrease in the power supply voltage of the one battery, and the display section is driven by the other of the batteries.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2, this embodiment has a power supply A4 and a power supply B
5, the current consumption of power source A4 is larger than that of power source B5, and the capacity of power source A4 decreases due to light,
A voltage fluctuation amplification unit 6 that amplifies the power supply voltage fluctuation of the power source 4, a determination unit 7 that determines the degree of decrease in the power supply voltage from the output of this amplification unit, and a display that displays the determination result and receives the power from the power supply B. This device is composed of a section 8. By displaying the voltage drop of the power source using power source B, it is possible to equalize the state of consumption of the batteries used for the two power sources.

FIG. 3 shows a specific circuit, in which 11 is a constant voltage diode, 12 is a diode, 13 is a transistor that amplifies power supply voltage fluctuations, 14 is a constant voltage diode, and 16 is a CMOS inverter that determines the degree of decrease in power supply voltage. , 16
is an LED that indicates a drop in power supply voltage, and 17 is an LED l
This is a transistor that drives 6.

The operation of the power supply voltage detection and display device configured as described above will be described below.

Now, in an electronic device to which the circuit of this embodiment is added, the power supply A
It is assumed that the power supply A4 consumes a larger current than the power supply A4 and the power supply B5, and its power supply voltage decreases first.

Therefore, fluctuations in the power supply voltage of the power supply A4 are applied to the base of the transistor 13 through the constant voltage diode 11 and amplified. Here, the diode 12 is provided so that the load on the transistor 13 becomes steeper near the lower limit of the power supply voltage of the power supply A4 by utilizing its nonlinearity.

Therefore, with a slight drop in the power supply voltage near the lower limit value of the power supply voltage '-power supply voltage of the power supply A4, the output of the transistor 13 changes greatly from low level to high level. Note that the constant voltage diode 14 is used to determine the emitter voltage of the transistor 13. The above is the voltage fluctuation amplification section 6 of FIG. 2. The output of the transistor 13 is input to the CMOS inverter 16. Since the output of the transistor 13 changes greatly from low level to 7-high level near the lower limit of the power supply voltage, the CMOS input/output 15 can maintain the power supply voltage regardless of the fluctuation of the threshold level caused by the fluctuation of the power supply voltage. Operates reliably at the lower limit value.

In other words, the output of this CMOS inverter 15 is inverted from high level to low level. This CMOS inverter 15 corresponds to the determining section 7 in FIG.

When the output of the CMOS inverter 15 is inverted from the low level to the low level, the l/registor 1 changes from off to on, and the LED l6 lights up, indicating that the voltage of the power source 4 has dropped. In addition, power supply B5 is used as a power supply for lighting up 1ED16i, so that power supply B5
Two power supply type i% A4. Equalize the consumption status of B6.

As described above, according to this embodiment, by amplifying the fluctuations in the power supply voltage, this circuit operates and does not consume the power supply of the display unit. By obtaining power from a power source that is not currently in use, it is possible to equalize the consumption of the two power sources.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a circuit diagram of a power supply voltage detection display device showing a second embodiment of the present invention. In FIG. 4, 18 is the power supply C1
18' is a power source, 19 and 19' are inverters, 20 is a display LED, 21 is an opto-isolator, 22 is an opto-isolator, 23 is a diode, and 24 is a diode.

In the first embodiment, the power source that consumes the battery is fixed among the two power supplies, but in this embodiment, this is not fixed, and the voltage fluctuation amplifying section and the discriminating section are
Although the configuration is the same as that shown in the figure, this embodiment has one for each power source, and the configuration of the display section is different from the configuration shown in FIG. 3.

The operation of the second embodiment of the power supply voltage detection and display device configured as described above will be described below.

The power supply 18 or 18' becomes exhausted and the power supply voltage decreases. However, it is not determined which power source will run out first. The voltage drops of the power supplies 18 and 18' are amplified by voltage fluctuation amplifiers 6 and 6', respectively, and input to oven collector type inverters 19 and 19'. That is, when the power supply voltage of the power supply 18 decreases below the lower limit value,
The output of one inverter becomes low level, and when the power supply voltage of power supply 18' falls below the lower limit value, the output of inverter 19' becomes low level.

When the output of the inverter 19 becomes low level, the opto-isolator 21 operates and this transistor is turned on. Then, the diode 23° LED 20, the opto-isolator 21. The circuit of power supply 18' becomes conductive, and LE
D20 lights up.

Similarly, when the output of the inverter 19' becomes low level, the transistor of the opto-isolator 22 turns on, and the opto-isolator 22 and the LED 20
．． The circuit of diode 24 and power supply 18 becomes conductive, and LE
D20 lights up.

As described above, according to this embodiment, a display LED and two diodes are connected in a closed circuit, a series circuit of an opto-isolator transistor and a power supply is connected to each of these two diodes, and a power supply is connected to the display LED and two diodes. By arranging the reverse bias of the diode to cut off the current from the LED, one LED can be lit using either of the two power supplies.

In the first embodiment, if the circuit constants and the transistor 13 are selected so that the collector current of the transistor 13 is small, and if a high resistance is used for the resistor R1, the current consumption of the power supply detection and display circuit can be reduced. I can do it. Although the transistor 13 is a junction transistor, it goes without saying that it may also be a field effect transistor. It goes without saying that it can be constructed from CMOS buffers and transistors.

Effects of the Invention As described above, the power supply voltage detection display device of the present invention has a power supply for detecting fluctuations in power supply voltage and a power supply for driving the display unit separately, so that the power supply voltage of one power supply can be reduced. When the battery is low, the status can be displayed by the other battery.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a power supply voltage detection circuit in a conventional example, FIG. 2 is a block diagram of a power supply voltage detection and display circuit in an embodiment of the present invention, and FIGS. 3 and 4 are respective embodiments of the present invention. FIG. 3 is a circuit diagram of a power supply voltage detection and display circuit in FIG. 4...Power supply person, 5...Power supply B, 6...
... Voltage fluctuation amplification section, 7... Discrimination section, 8...
...Display section, 18゜18' ...Power supply, 2o
...LED, 21. 22...Opto isolator, 23.24...Diode O

Claims (2)

[Claims] (1) In order to obtain multiple power supply voltages, separate batteries are provided, and a voltage fluctuation amplification section amplifies the fluctuations in the power supply voltage of one battery, and the output of this voltage fluctuation section is constant (when the voltage exceeds the A power supply voltage detection and display circuit comprising: a display section for displaying a decrease in power supply voltage of a battery, the display section being driven once by the other one of the batteries. (2) In the display section, a display element and two diodes are connected in a closed circuit, and a series circuit consisting of a switch and a DC power supply is connected to each of these two diodes, and the current of the DC power supply is connected to the reverse circuit of the diode. A power supply voltage detection and display circuit according to claim 1, which is formed with a groove so as to be cut off by a bias.