JPS5899230A - Power source - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a power supply device for stabilizing the power supply voltage from a battery power supply with an automatic voltage adjustment circuit, and supplying the stabilized output voltage of the automatic voltage adjustment circuit to a load as the power supply voltage. In particular, it is an object of the present invention to provide a power supply device that can prevent a battery as a power source from causing liquid leakage due to dissipation or electricity.

Generally, as shown in FIG. 1, a power supply device of a device supplies a power supply voltage VBB from a plurality of batteries 11 to an automatic voltage adjustment circuit 12, and a stabilized output voltage Vcc from this automatic voltage adjustment circuit 12 is used as a power supply. The voltage was configured to be supplied to the load 13 as a voltage. However, in the above-described power supply device, there is a problem in that if the battery 11 serving as a power source is over-discharged, leakage occurs, and a countermeasure for this problem is desired. In particular, when a rechargeable nickel-cadmium battery is used as the battery 11, a large current flows from the plurality of batteries 11 connected in series, resulting in an overdischarge state. At this time,
The capacities of the above-mentioned batteries are not completely equal, and in the over-discharge state described above, the battery with the lower capacity discharges first, and becomes a load for the batteries that are not yet fully discharged. The battery will be charged in the reverse direction. Then, reverse-charged batteries deteriorate rapidly, causing leakage that can damage equipment, or lead to a state of insufficient capacity where even after charging, the remaining capacity is less than the original discharge capacity. There was a problem that the battery life decreased and the battery needed to be replaced.

The present invention solves these conventional drawbacks, and
A means is provided to detect a drop in the power supply voltage from the battery power source and cut off the comparison reference voltage of the automatic voltage adjustment circuit, thereby cutting off the output voltage from the automatic voltage adjustment circuit and preventing over-discharge of the battery. It is designed to prevent this.

Embodiments of the power supply device of the present invention will be described below. FIG. 2 shows an embodiment of the power supply device of the present invention.
In the figure, 1 is an automatic voltage adjustment circuit that converts the voltage of a battery power supply 6 that can be charged by a power supply voltage VDC supplied from an external power input terminal 6 to a power supply voltage VBB from a connection point between a diode D2, a resistor R1, and a diode DI. This power supply voltage VBB is stabilized and a voltage VDD is output.

This automatic voltage adjustment circuit 1 consists of transistors Q2 e Q3
It is composed of an e diode D6 and resistors R6 and R7.

Reference numeral 2 denotes an automatic voltage adjustment circuit, which is supplied with the power supply voltage VBB, operates with the output voltage v11D of the automatic voltage adjustment circuit 1 as a reference voltage, and outputs a stabilized voltage Vcc. This automatic voltage adjustment circuit 2 includes transistors Qs, Qa, a diode D7, and a resistor R8.
3 is a load that operates using the output voltage vDD of the automatic voltage adjustment circuit 1 as the power supply voltage;
4 is a load that operates using the output 1 voltage Vcc of the automatic voltage adjustment circuit 2 as the power supply voltage; 7 is an overdischarge prevention circuit that detects a drop in the power supply voltage Van and cuts off the comparison reference voltage of the automatic voltage adjustment circuit 1; It looks like this. This overdischarge prevention circuit 7 is a transistor Q1% diode "3 * D4
*R5 and resistor R2e "3 *R4t"5
It consists of A circuit consisting of a transistor Q4 and a resistor R1+ is configured to start the automatic voltage adjustment circuit 2 using the output a of the load 3.

Load 3 is a clock timer using prt4os IC, keyboard reception buffer IC, and I for driving LCD display.
It consists of a minute current load such as C, a storage element with a small standby current, an 0MO8RAV, a liquid crystal display with a minute current, etc., and it consists of loads that need to be constantly energized and loads that consume only a small amount of current even when they are in operation.

The load 4 consists of a high-speed microprocessor consisting of an NMO8I (J), a decoder consisting of a TTL, etc., and a ROM that consumes a large amount of current but is required to operate only when the microprocessor is operated.

Between loads 3 and 4, there are address lines, data lines (bidirectional), timing signals, and other control signals from the load 40 microprocessor.
A timer signal and a keyboard reception signal from the load 3 are received by the microprocessor, processed by the microprocessor, and then displayed on the liquid crystal display for the load 3. 9. The time data in RAM has been updated.

Here, load 3. Since the load 4 uses a digital element that requires a highly stabilized voltage during operation, the output voltages yoD, y of each of the automatic voltage regulator circuits 1 and 2 are adjusted.
Both cc need to be 6±0.25V. Therefore, the automatic voltage adjustment circuits 1 and 2 are configured so that approximately 6V is applied to the reference voltage input terminals (bases of transistors Q3 and Q6).

As the battery power source 6, five nickel cadmium batteries are connected in a row, and a total discharge characteristic of 6 to 6.8 V is obtained. Then, by subtracting the voltage drop caused by the Schottky barrier diode D2, the power supply voltage vBB is 6.8 to 6.6.
I am getting v. Stabilized 9V as external power input
use. In this case, the power supply voltage VBB is VDC=9V
When the voltage drop of the diode D1 is subtracted from the voltage drop of the diode D1, the current consumption from the battery power supply 6 disappears, and conversely, the current consumption from the battery power supply 6 disappears.
The battery power source 6 is charged via the battery 7.

In this configuration, when there is no external power input and the battery power supply 6 is operating, when the voltage of the battery power supply 6 is sufficiently high, a Zener diode of about 4V is used as the diode D3, so the transistor Q1 is turned on. The base voltage of the transistor Q3 is stabilized by the Zener diode D5 of approximately 6V. In the automatic voltage adjustment circuit 1, a voltage lower than the power supply voltage VDD by the forward voltage (approximately 0.6 V) caused by the diode D6 is applied to the emitter of the transistor Q3. The value obtained by subtracting the emitter-to-emitter forward voltage (approximately o, e v) is compared, and when the output voltage vDD is too low, the base current of transistor Q3 increases, and the DC current amplification factor hl of transistor Q3 increases.
The collector current is amplified to Fgg times the collector current, and is further amplified by the transistor Q2.
Since the collector current of transistor Q2 is multiplied,
It works to increase the output voltage VDD.

Conversely, when the output voltage VDD is too high, the transistor Q2
(7) Since the collector current is limited, the output voltage vDD becomes approximately equal to the base potential of the transistor Q3 and is stabilized. On the other hand, the automatic voltage adjustment circuit 2 sinks current at the terminal 31L of the load 3 in response to an interrupt processing request signal from the timer XC included in the load 3, the keyboard reception IC, or an external peripheral device, and draws current at the base of the transistor Q4. A current is applied to turn on transistor Q4. That is, a signal is applied from the terminal 3a to turn on the transistor Q4. As a result, transistor Q4 is turned on, and the base of transistor Q6 becomes approximately equal to the emitter potential vDD of transistor Q4.The circuit configuration of automatic voltage adjustment circuit 2 is the same as automatic voltage adjustment circuit 1, and therefore transistor Q6 A voltage substantially equal to the base current of is obtained from the collector of transistor Q5 as output voltage Vcc. If the base current of the transistor Q4 is cut off at the terminal 3a of the load 3, the transistor Q4 is turned off and the output voltage Vcc becomes 0 volts.

The resistor RIG of the automatic voltage adjustment circuit 2 is set to a smaller value than the resistor R7 of the automatic voltage adjustment circuit 1 so as to increase the maximum emitter current of the transistor Q6 and increase the maximum collector current of the transistor Q5. There is. This means that the current flowing through the resistor R7 and RIO is the transistor Qs,
Since the emitter potential of transistor Qs is always constant at approximately 4.4V, it is approximately constant. Even if the collector current of Q5, that is, the load current, is small and the corresponding emitter current of transistors Q3 and Qs may be small, the difference current is supplied via diodes D and D7, so it flows to diodes D6 and D7. The current is considered a loss current.

Therefore, from the viewpoint of extending battery life, the loss current of the automatic voltage adjustment circuit 1, which is always on, is suppressed as much as possible. To make this possible, the load on automatic voltage adjustment circuit 1 is kept as light as possible. On the other hand, automatic voltage adjustment circuit 2, which is turned on only when necessary, has a large load current, so the current flowing through resistor R1 is also large. This is because it is necessary.

Next, when the terminal voltage vB of the battery power supply 6 decreases, the power supply voltage VBB decreases, the current of the Zener diode D3 decreases rapidly, and the transistor Q1 turns off. Then, transistor Q3 is also turned off, and transistor Q2 is also turned off. Since the automatic voltage adjustment circuit 2 uses the output voltage VDD of the automatic voltage adjustment circuit 1 as a reference voltage, the transistor Q
6 is also turned off, transistor Q5 is also turned off, and load 3.6 is also turned off. Current consumption in the load 4 can be completely cut off. or,
Transistor Q1 is also turned off, and diode D30 current is also changed.If a punch-through type Zener diode that works at high performance even at low voltage is used for diode D3, it can be turned off rapidly due to a drop in the power supply voltage VaB, so the Zener voltage of approximately 4V is applied to diode D3. By using this, the load on the battery type/source 6 can be completely cut off when the power supply voltage VBB reaches approximately 4.6V. Even if a nickel cadmium battery is used as the battery power source 6, over-discharge is prevented and there are no problems such as leakage or reverse charging.

The resistor R3 of the overdischarge prevention circuit 7 is necessary when the power supply voltage Was is high.
The resistor R2 is used to prevent current from flowing through the diode D3.
It is used to completely turn off transistor Q1.

In addition, the reason why the Zener diode D4 is additionally provided at the base of the transistor Q3 via the resistor R5 is because the Zener voltage of 6V is used for the diode D4, and even if a large voltage is applied to the power supply voltage VaB due to the external power input, This is to suppress the rise in the reference voltage of transistor Q3.

As described above, according to the present invention, an overdischarge prevention circuit is provided which has a means for detecting a drop in power supply voltage from a battery power supply and a means for cutting off a comparison reference voltage of an automatic voltage adjustment circuit based on the detection result. , capable of interrupting the output voltage as a stabilized power supply voltage from the automatic voltage adjustment circuit;
The current consumption of the load on the battery power source can be cut off.

Therefore, it is possible to prevent over-discharge of the battery power source, eliminate leakage of liquid, and prevent damage to the equipment Q due to this leakage.

Furthermore, using a rechargeable ÷Tschel cadmium battery as a battery power source has the advantage of preventing over-discharge and eliminating the inconvenience of reverse charging.

[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. 1.2... Automatic voltage adjustment circuit, 3.4...
...Load, 5...Battery power supply, 7...Overdischarge prevention circuit, Ql-Qa...-Transistor,
D, ~D7...Diode, R1-R7゜...
····resistance. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (4)

[Claims] (1) detection means for detecting power supply voltage from a battery power supply;
A power supply comprising an overdischarge prevention circuit having a cutoff means for cutting off a comparison reference voltage of an automatic voltage adjustment circuit that supplies an output voltage obtained by stabilizing the power supply voltage to a load as a power supply voltage based on a detection result of the overdischarge detection means. Device. (2) The automatic voltage adjustment circuit connects the first transistor whose emitter is connected to the positive electrode side of the battery power supply, and the collector of the second transistor, and connects the emitter of the second transistor to the emitter of the first transistor through a diode. The collector of the first transistor is connected to the negative electrode side of the battery power source through a resistor, and the reference voltage element is connected to the base of the second transistor, and the collector of the first transistor is connected to the negative electrode side of the battery power supply. Voltage load power supply 1
2. The power supply device according to claim 1, further comprising an overdischarge prevention circuit connected to the base of said second transistor. (3) The overdischarge prevention circuit is connected to the negative electrode side of the battery power source via a resistor and a diode to the base of a transistor whose base and emitter are connected to the positive electrode side of the battery power source,
2. The power supply device according to claim 1, wherein the transistor is configured to take out an output from the collector of the transistor to cut off a comparison reference voltage of the automatic voltage adjustment circuit. (4) a first automatic voltage adjustment circuit that stabilizes the power supply voltage from the battery power source and supplies the output voltage to the load as the power supply voltage; a second automatic voltage adjustment circuit that stabilizes and outputs the power supply voltage from the battery power supply using the output voltage of the automatic voltage adjustment circuit as a reference voltage; a detection means for detecting the power supply voltage from the battery power supply; and a detection means for detecting the power supply voltage from the battery power supply; -C is provided with an over-discharge prevention circuit having a cut-off means for cutting off the comparison reference voltage of the first automatic voltage adjustment circuit based on the detection result; 1. A power supply device configured to cut off the output voltage from the second automatic voltage adjustment circuit.