JPS5897722A - Power supply device - Google Patents

Abstract

PURPOSE:To foreknow assuredly voltage drop, by comparing the voltage of a battery power supply with the voltage of an automatic voltage controlling circuit and then setting the working voltage of a voltage reduction detector which is contained in a load which works through the automatic voltage controlling circuit on the basis of the detected voltage reduction. CONSTITUTION:A voltage VBB is supplied to an automatic voltage control circuits (AVR) 1 and 2 and a voltage reduction setting circuit 7 from an external power supply VDC or a built-in battery power source VB. The AVR1 delivers the voltage VDD and applies it to the circuit 7 along with a load 1 and the AVR2. A TRQ3 is turned on when the difference between the VBB and VDD is large and then turned off with about 0.6V. At this time point, a TRQ4 is turned on and the value drops suddenly for an equivalent resistance that decides the working voltage of a voltage drop detecting IC connected to a terminal 3a of a load 3. At the same time, the set voltage for detection of the voltage drop rises up suddenly to exceed the VDD. Thus the voltage drop detecting signal is delivered. A microprocessor of a load 4 reads out the set voltage and displays it to the load 3 with the liquid crystal. In such a way, a voltage drop is know previously. Such a power supply is suited to an RAM.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device for electrical equipment equipped with a rewritable memory (for example, RAM, etc.). It is an object of the present invention to provide a power supply device that can prevent important data stored in the memory from being lost by notifying the user that the need for charging has arisen.

In general, a power supply device for an electrical device equipped with a rewritable memory has a diode D2 and a resistor connected to the positive electrode side of a rechargeable battery 6 that receives power supply voltage from an external power input terminal 5, as shown in FIG. The power supply voltage VBB is supplied from the connection point between R1 and the diode D1 to the automatic voltage adjustment circuits 1 and 2, the power supply voltage Vo+o from this automatic voltage adjustment circuit 1 is supplied to the load 3, and the power supply from this automatic voltage adjustment circuit 1 is The power supply voltage Vcc from the automatic voltage adjustment circuit 2 with reference to the voltage VDD is supplied to the load 4. A reduced voltage detection integrated circuit (not shown in the figure) connected to a resistor RI2 at the terminal 3a of the load 3 is used to detect the reduced voltage to notify the user that the voltage of the battery 6 has decreased and conversion or charging is required. (2) detects that the power supply voltage VDD from the automatic voltage adjustment circuit 1 has fallen below a specified voltage.

In the voltage reduction detection integrated circuit, the value of the power supply voltage VDD at which a voltage reduction detection signal is output as a result of a decrease in the power supply voltage is set based on the value of the resistor R12. The reduced voltage detection signal from the integrated circuit for detecting reduced voltage is read by the microprocessor included in the load 4 to which the power supply voltage 3, -1-Vcc from the automatic voltage adjustment circuit 2 is supplied, The included liquid crystal display displays text or graphics to indicate that the power supply voltage has dropped.

However, in the above-mentioned power supply device, the reduced voltage detection integrated circuit is included in the circuit block driven by the output voltage of the automatic voltage adjustment circuit 1, and the power supply voltage V
As BB decreases, the output voltage V of automatic voltage adjustment circuit 1
Reduced voltage detection becomes possible only after nn is not fully stabilized and drops to a value lower than the voltage set by resistor R12. Therefore, the power supply voltage VDD is 5v±0.25
In circuits with strict conditions such as V, when considering the temperature characteristics of the detected voltage, it is important to consider the temperature characteristics of the detected voltage as an integrated circuit for detecting reduced voltage. There were also problems with mass production, such as fine adjustment of values. In addition, the automatic voltage adjustment circuit 10
The output voltage Vcc of the automatic voltage adjustment circuit 2, which uses the stabilized output voltage VDn as a reference voltage and is driven by ON/OFF signals output from the circuit included in the load 3, is controlled by a microprocessor or TTI.

5V:l:0.25V is required as the power supply voltage V9G. That is, when the automatic voltage adjustment circuit 2 is on, the power supply voltage Vcc is obtained as approximately the same potential as the power supply voltage VDD by comparison with the power supply voltage vDIl, and the reference voltage VD of this power supply voltage Vcc is obtained.
A tighter tolerance voltage is required for D. Therefore, in the power supply device described above, it has become more difficult to detect the power supply voltage VDD and display a reduced voltage. Furthermore, even if the above-mentioned reduced power display is displayed while operating on batteries, the reduced voltage is detected after the output voltage VDD of the automatic voltage adjustment circuit 1 has already begun to fall below the set value of the resistor RI2. The period from when the power supply voltages VDD and VCC fall below the lower limit of 4.75V of the specified voltage 6V±0.25.

The time during which the device can operate is short, so even if a voltage reduction warning is issued, there is a risk that the device will not be able to operate or the operation will not be guaranteed.

The present invention solves these conventional drawbacks,
To the load including the integrated circuit for detecting reduced voltage, detect reduced voltage before the power supply voltage from the binary voltage adjustment circuit decreases, and set the operating voltage of the integrated circuit for detecting reduced voltage. It is composed of

EMBODIMENT OF THE INVENTION Hereinafter, the power supply device of this invention is demonstrated with drawing of an Example. FIG. 2 shows an embodiment of the present invention. In the figure, 1 is an automatic voltage adjustment circuit, and a dunnode D2 is connected to a battery 6 which can be charged by receiving power supply voltage from an external power input terminal 6. A power supply voltage VBB is supplied from a connection point between the resistor R1 and the diode D1, and a stabilized power supply voltage VDI) is output. This automatic voltage adjustment circuit 1 is composed of transistors Q+, Q2, diodes Ds, D4, and resistors R2, Rs, R4. Reference numeral 2 denotes an automatic voltage adjustment circuit, which is supplied with the power supply voltage vBB and operates with the power supply voltage VDD from the automatic voltage adjustment circuit 1 as a reference voltage, so as to output a stabilized power supply voltage Vcc. . This automatic voltage adjustment circuit 2 consists of a transistor QS I Q61
Q7, diode D7 and resistor R8, Rq, R
+o, R++. 3 is a load that operates with the power supply voltage VDD, 4 is a load that operates with the power supply voltage VCC, and 7 is a voltage reduction detection integrated circuit that operates with the power supply voltage VCC and detects the voltage reduction and is included in the load 3. This is a reduced voltage setting circuit that sets the operating voltage of the circuit.
It is connected to the terminal 31L of. This reduced voltage setting circuit 7
are transistors Q5, Q4, and resistor Rs,
It is composed of R6°R7.

The power source consists of a battery power source consisting of six nickel cadmium batteries combined in series, or an external power source Vnc, and when there is no external power source, the power is supplied from the battery 6 via a Schottky diode D2 adopted to reduce the forward voltage drop. Power supply voltage VBB is supplied. That is, the voltage of the battery power supply is approximately 6.0 to 6.7V, and from this the voltage of the diode D
The value of the power supply voltage VBB is 6.7v to 6.4v, which is obtained by subtracting the voltage 0.3V of 2. 9. As an external power supply. A stabilized power supply of OV is used, and the power supply voltage VBB is connected to a diode D.
It becomes 8.2V by subtracting the voltage drop o, sV of 1. At this time, the battery 6 is charged via the resistor R1.

The automatic voltage adjustment circuit 1 supplies a power supply voltage VDn (6V±0.25V) to the CMO8RAM included in the load 1 as a standby power supply for storing data and for small loads such as 0MO8IC and LCD display 7behle display devices. It is also used as a reference voltage for the automatic voltage adjustment circuit 2.

A decoder circuit consisting of a microprocessor, TTL, etc. in the load 4 extracts a signal for turning on and off the automatic voltage adjustment circuit 2 from the terminal 3b of the load 3 according to the timer function included in the load 3, a keyboard reception signal, and an external interrupt signal. The output voltage Vca of the automatic voltage adjustment circuit 2 is supplied to the peripheral components such as the load 4, and the microprocessor of the load 4 performs timer processing, keyboard reception processing, and interrupt reception processing from external peripheral devices, and when the predetermined work is completed, Turn off the system control signal included in load 3 (terminal sb of load 3), turn off automatic voltage adjustment circuit 2, and enter standby.
Enter the mode. Even if the automatic voltage adjustment circuit 2 is turned off and the circuit in the automatic voltage adjustment circuit 1 and the load 3 is displayed on the LCD using a small current, the keyboard reception wait and the counter operation of the timer function continue. It is possible.

In the power supply device having such a configuration, the transistor Q5 configuring the reduced voltage setting circuit element is connected to the power supply voltages VBB, V
It is turned on when the voltage between DD and VDD is sufficiently large, and is turned off when the voltage between power supply voltage VBB and VDD becomes approximately equal to o and ev. At this point, the transistor Q4 is turned on, and the value of the equivalent resistance for determining the operating voltage of the integrated circuit for detecting a reduced voltage connected at the terminal 3a of the load 3 decreases rapidly. The set voltage increases rapidly and significantly exceeds the power supply voltage VDD, so the integrated circuit for detecting a reduced voltage outputs a reduced voltage detection signal, which is read by the microprocessor included in the load 4 and outputs a reduced voltage detection signal. A display to that effect will be displayed on the liquid crystal display included in the. The limiting transistor Q1 of the automatic voltage adjustment circuit 1 has a collector-emitter voltage of approximately 0.1V.
It operates normally until it reaches the vicinity, so the power supply voltage VD
Voltage reduction is detected before D decreases, and the time until power supply voltage VDD starts to decrease can be saved. Therefore,
In this example, six batteries that can be recharged as 91\-di batteries were used, and the nominal voltage was 6V.
With the power supply, the output voltage VDD of automatic voltage adjustment circuit 1 is 5V.
It can be put to practical use even if the required voltage is ±0.25, and the device can be made compact, lightweight, and inexpensive with the minimum necessary configuration without requiring an unnecessarily high battery voltage. .

In this embodiment, when operating with an external power supply, the power supply voltage V
Since BB reaches as high as 8.2V, it is necessary to limit the current flowing from the emitter to the base of transistor Q3.

That is, if there is no resistor R5, the power supply voltage VDD is VBB.
-0-6V = 7-6V will be overloaded, and the function of the automatic voltage adjustment circuit 1 will be destroyed. In this sense, it is necessary to insert a limiting resistor in series with the emitter or base of the transistor Q3.According to the present invention, as shown in FIG. A voltage reduction that detects voltage reduction by comparing it with the previous power supply voltage and sets a 1° operating voltage of an integrated circuit for voltage reduction detection included in a load to which the power supply voltage from the automatic voltage adjustment circuit is supplied. Since it is equipped with a setting circuit, it is possible to detect a voltage drop before the power supply voltage from the automatic voltage adjustment circuit drops, and it is possible to reliably detect that the battery voltage has dropped, even though the power supply voltage is originally low and unregulated. However, it has the advantage of being able to display and warn on a liquid crystal display.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional power supply device, and FIG. 2 is a circuit connection diagram showing an embodiment of the power supply device of the present invention. 1... Automatic voltage adjustment circuit, 3... Load, 6... Battery, 7... Reduced voltage setting circuit, Q3, Q4...・Transistor, R5
, R6, R7... Resistance.

Claims (1)

[Claims] Means for detecting a voltage drop by comparing the voltage of an automatic voltage adjustment circuit that stabilizes and outputs the power supply voltage from the battery power supply with the power supply voltage from the battery power supply, and the automatic voltage adjustment circuit that is also used for detecting the voltage reduction. 1. A power supply device comprising a reduced voltage setting circuit having means for setting an operating voltage of a reduced voltage detection circuit included in a load to which the voltage is supplied as a power supply voltage.