JP2002369397A - Overdischarge prevention circuit for primary battery and multisystem power supply circuit fitted with this circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overdischarge prevention circuit for a primary battery, and a multisystem power supply circuit fitted with this circuit, which shuts out even a feeble discharge of a battery when the battery becomes in a discharge stop state, and surely evades the discharge of the battery. SOLUTION: A main switching element Q1 is arranged in a power supply route 2 connecting a primary battery B and a load Z, and this element Q1 is on/off-controlled by a controlling switching element Q2. A divided voltage output by resistors R3, R4 connected to the supply route 2 on the load Z side rather than the element Q1, is inputted to the base of the element Q2. If the battery voltage becomes lower than a set voltage, the element Q2 is turned off. Consequently, the base current of the element Q1 is interrupted and the element Q1 is turned off too. Any feeble current does not flow from the battery B, and discharge of the battery is completely stopped. By closing a switch SW1 after a battery exchange and inputting the battery voltage directly to the element Q2, the element Q2 is turned on, and the element Q1 is turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mobile phone and a PDA.
For the overdischarge prevention circuit for protecting the primary battery used in various electronic devices from overdischarge, etc., it is possible to completely shut out the weak current from the battery when the discharge is stopped. The present invention relates to an overdischarge prevention circuit for a primary battery, which can reliably protect the battery from overdischarge, and a multi-system power supply circuit including the circuit.

[0002]

2. Description of the Related Art An over-discharge prevention circuit for a secondary battery such as a lithium secondary battery is disclosed in Japanese Patent Application Laid-Open No. 4-33142.
No. 5 is known. In this prior art overdischarge prevention circuit, a switching element is inserted in a discharge path from a battery to a load, and a battery voltage is detected by a voltage detector. When the battery voltage is sufficiently high, the switching element is turned on by the output from the voltage detector, and current flows from the battery to the load via the switching element. When the battery voltage gradually decreases due to the discharge and the battery voltage falls below a predetermined set voltage, the switching element is turned off by the output from the voltage detector. As a result, the discharge path from the battery to the load is cut off, the discharge is stopped, and overdischarge of the battery is prevented.

[0003] The power supply can be started again from the secondary battery,
After charging, the switching element is turned on in response to the supply of charging power from the outside, and power can be supplied from the battery to the load again.

[0004]

However, the power supply of the primary battery cannot be restarted at the time of charging as in the case of the secondary battery. Therefore, in the primary battery, the following overdischarge prevention circuit has been adopted.

FIG. 9 shows an example of a conventional overdischarge prevention circuit for a primary battery. This circuit includes a switching element Q1 composed of a PNP transistor provided on one of two power supply lines 2 connecting a battery B and a load Z.
A resistor R1 provided between the base terminal and the emitter terminal of the switching element Q1, and a resistor connected in series between the base terminal of the switching element Q1 and the other power supply line 2. R2 and a Zener diode D1.

When the battery voltage is sufficiently high, the resistance R1
In addition, a current flows through the resistor R2 and the Zener diode D1, and a base current also flows through the switching element Q1, so that the switching element Q1 is turned on and the battery B
Current flows from the load to the load Z. When the discharge proceeds and the battery voltage gradually decreases, the switching element Q1 is turned off,
The discharge path from the battery B to the load Z is shut off. The battery cell for which the switching element Q1 is turned off is determined by the resistor R2 and the Zener diode D1.

When the battery B is newly replaced, the battery voltage becomes sufficiently high, so that the base current starts to flow again in the switching element Q1, the switching element Q1 is turned on, and the power supply is restarted.

However, this circuit has the following problems. That is, the switching element Q1
Was turned off, and a very weak current flowed in the path formed by the resistors R1, R2 and the Zener diode D1 even though the battery B was in the discharge stopped state. As described above, although the battery B is in the discharge stopped state, a weak current flows, which may cause the battery to be over-discharged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to cut off a weak current even when a battery is in a discharge stop state. It is an object of the present invention to provide a primary battery overdischarge prevention circuit capable of reliably avoiding the discharge of a primary battery and a multi-system power supply circuit including the circuit.

[0010]

In order to achieve the above object, a circuit for preventing overdischarge of a primary battery according to the present invention is provided on a power supply path from a primary battery to a load. And a voltage detection circuit provided on the load side of the main switching element to detect a supply voltage to the load, and the main switching element detects when the voltage detected by the voltage detection circuit falls below a set voltage. A control circuit for turning off the switching element, a bypass path interposed between the battery side of the main switching element and the input side of the control circuit and bypassing the switching element, and a bypass for opening and closing the bypass path An open / close switch is provided (claim 1).

In this circuit, since the voltage detection circuit is provided on the load side of the main switching element, a weak current does not flow through the voltage detection circuit when the main switching element is turned off. In addition, the discharge of the battery can be reliably stopped. On the other hand, when the battery is replaced with a new battery, by closing the bypass open / close switch, the power supply voltage of the new battery can be input to the control circuit through the bypass path without passing through the main switching element,
Thereby, the main switching element is turned on, and the power supply from the battery to the load can be restarted.

Further, the main switching element is PN
It is characterized by comprising a P-type transistor (claim 2). By configuring the main switching element with a PNP transistor, the current supplied from the battery to the load can be limited by the relationship between the base current of the PNP transistor and hfe, and the load can be protected from overcurrent.

Further, the control circuit includes a control switching element that is turned on / off in accordance with a detection voltage from the voltage detection circuit and controls on / off of the main switching element. (Claim 3). If the control circuit is composed of switching elements,
The on / off control of the main switching element can be easily performed.

Further, the main switching element is constituted by a bipolar transistor or a field-effect transistor, and a short-circuit switch for short-circuiting between the base and the emitter or between the gate and the source is provided. Item 4). The main switching element can be cut off by the short-circuit switch, whereby the power supply path from the battery to the load can be forcibly cut off, and the switch for stopping power supply can be configured very easily at a small signal level. be able to.

Further, the control switching element is constituted by a bipolar transistor or a field effect transistor, and a short-circuit switch for short-circuiting between the base and the emitter or between the gate and the source is provided. Claim 5). The control switching element can be cut off by the short-circuit switch, thereby turning off the main switching element and forcibly cutting off the power supply path from the battery to the load.
A switch for stopping power supply can be configured very simply.

Further, the bypass opening / closing switch and the short-circuit switch connected to the main switching element are constituted by one double-throw switch. Since the two switches are constituted by one double-throw switch, the cost can be reduced by reducing the number of components.

Further, a delay circuit for delaying signal transmission from the voltage detection circuit to the control circuit or from the control circuit to the switching element is provided. By providing such a delay circuit, when the load is a pulsed load Z through which an intermittent current flows, even if the battery voltage drops momentarily, the discharge stop function is erroneously activated and the load Z Can be prevented from being stopped.

Further, as the delay circuit, a capacitor is connected in parallel from the voltage detection circuit to the control circuit (claim 8). By using the capacitor in this way, the delay circuit can be configured very simply.

Further, in the multi-system power supply circuit including the primary battery overdischarge prevention circuit according to the present invention, a plurality of power supply systems for individually supplying power from the primary battery to a plurality of loads, respectively, A switching device for each system provided in each power supply system to open and close each power supply system, a power supply controller for individually controlling on / off of each switching device for each system, and separately provided from the plurality of power supply systems. A controller power supply system for supplying power from the battery to the power supply controller,
In a multi-system power supply circuit in which when the power supply from the battery to the power supply controller is stopped, the power supply controller turns off all of the system-based open / close switching elements and shuts off all of the power supply system, the controller power supply system includes: A main switching element is provided, and a voltage detection circuit for detecting a power supply voltage to the power supply controller is provided on the power supply controller side from the main switching element, and the voltage detection circuit detects the power supply voltage when the detected voltage falls below a set voltage. The control circuit turns off the main switching element (claim 9).

In the case of such a multi-system power supply circuit, power supply from the battery to each power supply system can be cut off collectively by shutting off the power supply system to the power supply controller that controls opening and closing of each power supply path. Since it is not necessary to provide an overdischarge prevention circuit for each power supply system individually, it is possible to reduce the number of components, and it is not necessary to shut off all power supply systems at once, so relatively inexpensive small A switching element for a signal can be used, so that cost can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 shows a first embodiment of a circuit for preventing overdischarge of a primary battery according to the present invention. The overdischarge prevention circuit includes a main switching element Q1 interposed in one of the power supply paths 2 between the primary battery B and the load Z to open and close the power supply path 2; Power supply path 2
A voltage detection circuit 4 interposed therebetween to detect a supply voltage;
A control switching element Q2 for controlling on / off of the main switching element based on a detection signal from the voltage detection circuit 4, and a battery B of the main switching element Q1.
And a switch (bypass opening / closing switch) SW1 provided on the bypass path 8 to open and close the bypass path 8.

The main switching element Q1 is composed of a PNP transistor, and a resistor R1 is connected between the base and the emitter. The control switching element Q2 is formed of an NPN transistor, and has a collector terminal connected to the base terminal of the main switching element Q1 via a resistor R2. The emitter is connected to the other power supply path 2. The control switching element Q2 and the resistor R2 form a conduction path through which the base current of the main switching element Q1 flows.

On the other hand, the voltage detection circuit 4 comprises a resistor R3 and a resistor R
4. The midpoint between these two resistors R3 and R4 is connected to the base terminal of the control switching element Q2, and the divided output of the two resistors R3 and R4 is input to the control switching element Q2 as a voltage detection signal. The control switching element Q2 is turned on when the divided output is equal to or higher than the reference voltage (here, 0.6 to 0.7 V), and is turned off when the divided output is equal to or lower than the reference voltage.
As a result, the control switching element Q2 controls the opening and closing of the conduction path of the base current of the main switching element Q1, thereby turning on / off the main switching element Q1.

When the power supply voltage of the battery B is sufficiently high,
The divided output of the voltage detection circuit 4 is higher than the reference voltage, the control switching element Q2 is turned on, and the main switching element Q1 is also turned on. A current flows from the battery B to the load Z, and power is supplied.

On the other hand, when the discharge of the battery B proceeds and the battery voltage of the battery B gradually decreases, the divided output of the voltage detection circuit 4 gradually decreases, and when the divided output falls below the reference voltage,
The control switching element Q2 is turned off, and the main switching element Q1 is turned off. As a result, the current from the battery B to the load Z is cut off, and the discharging of the battery B is stopped.

Here, the resistor R3 is set so that the divided output falls below the reference voltage near the battery voltage reaching the cutoff voltage.
And the resistance ratio of the resistor R4.

When the main switching element Q1 is turned off, no current flows to the voltage detection circuit 4, the control switching element Q2 does not turn on, and a weak current does not flow through the resistor R1. Thus, the discharge of the battery B is completely shut out, and the battery B can be reliably protected from overdischarge.

By the way, in this circuit, once the main switching element Q1 is turned off, the main switching element Q1 cannot be turned on even if the used battery B is replaced with a new battery.

Therefore, when the battery B is replaced, a switch SW1 for turning on the main switching element Q1 by manual operation or the like is provided. This switch SW
Numeral 1 is provided in a bypass path 8 which connects the battery B side (emitter terminal) of the main switching element Q1 and the load Z side (collector terminal) and bypasses the main switching element Q1. The bypass path 8 is opened and closed. When the battery B is replaced with a new battery B, the battery voltage is input to the voltage detection circuit 4 by closing the switch SW1. The switching element Q2 is turned on, and the main switching element Q1 can be turned on. Then, the power supply from the battery B to the load Z can be restarted.

The switch SW1 only needs to be closed for an extremely short period of time for the control switching element Q2 to respond, so that a momentary momentary switch can be used.

In this circuit, since a PNP transistor is used for the main switching element Q1, the current flowing from the battery B to the load Z is reduced by a current limiting function based on the relationship between the base current of the PNP transistor and hfe. The load Z can be limited, and the load Z can be protected from overcurrent.

<< Second Embodiment >> FIG. 2 shows a second embodiment of an overdischarge prevention circuit for a primary battery B according to the present invention. In this circuit, a switch SW2 together with a resistor R5 is provided between the battery B side of the main switching element Q1 and the base side of the control switching element Q2 as a switch forming a bypass path 8 bypassing the main switching element Q1. Things. By directly inputting the battery voltage to the control switching element Q2 without passing through the voltage detection circuit 4, it is possible to prevent the battery B from directly conducting to the load Z when the switch SW1 is closed. Can be. As a result, even if the switch SW1 is erroneously closed when the battery B is in the discharge stop state, the discharge route from the battery B to the load Z is not opened, and the battery B is not overdischarged.

Since the switch SW2 needs to be closed only for a very short period of time for the control switching element Q2 to respond similarly to the case described above, an inexpensive instantaneous switch such as a momentary switch is used. Switches can be used. Further, in this circuit, since the current flowing through the switch SW2 can be adjusted to be small by setting the resistor R5, a very inexpensive small signal switch is used as the switch SW2. As a result, the switch can be easily configured, and the cost can be significantly reduced.

The input side of the control circuit to which one end of the bypass path according to the present invention is connected refers to the input portion of the control circuit (here, the base of the control switching element Q2) as shown in the circuit of FIG. First, as shown in the circuit of FIG. 1, the input side may be the input side of the voltage detection circuit, and as long as the battery voltage can be input to the control circuit without passing through the main switching element Q1, any position may be obtained as a result.

Third Embodiment FIG. 3 shows a third embodiment of an overdischarge prevention circuit for a primary battery B according to the present invention. In this circuit, a switch SW3 is connected in parallel between a base terminal and an emitter terminal (between both ends of a resistor R4) of a control switching element Q2 for controlling on / off of a main switching element Q1 in the circuit of the second embodiment. It was done. The switch SW3 is for short-circuiting between the base and the emitter of the control switching element Q2, and by short-circuiting between the base and the emitter,
The control switching element Q2 can be forcibly turned off.

When the control switching element Q2 is turned off, the main switching element Q1 is also turned off, and the discharge from the battery B to the load Z can be forcibly stopped even when the battery voltage has not reached the final voltage. it can. This switch SW3 can be used as means for stopping the power supply from the battery B to the load Z. As with the switch SW2, the switch SW3 can be configured at low cost by using a small signal momentary switch or the like.

When the power supply from the battery B to the load Z is restarted, the switch SW
2 is closed, the control switching element Q2 is turned on, and the main switching element Q1 is turned on. FIG. 4 shows another embodiment of a switch for forcibly stopping power supply. In this circuit, the switch SW4 is connected between the base and the emitter of the main switching element Q1.
Is interposed. By closing this switch SW4,
The main switching element Q1 is directly turned off, and the power supply from the battery B to the load Z is stopped. In the present embodiment, one end of the switch SW4 is connected to the emitter of the Q1 of the main switching element, and the terminal can be shared with the switch SW2 for restarting power supply. Therefore, the switch SW4 is configured by a double throw switch having one common terminal. be able to. With a single switch, the off operation for stopping the power supply from the battery to the load and the on operation for resuming the power supply can be realized with a single switch, and the power supply operation from the battery to the load can be easily realized and the number of components can be reduced. Cost can be reduced.
Further, as for the double throw switch, an inexpensive momentary switch for small signals can be applied similarly to the switches SW2 and SW3 described above, and the cost can be further reduced.

FIG. 5 shows an embodiment in which a small signal momentary switch applicable to the switches SW2 and SW3 is formed at low cost. FIG. 5A is a sectional view of the switch, and FIG. 5B is a front view of the switch. This switch is provided on the outer surface of an outer case 10 made of a synthetic resin or the like of various electric devices on which the overdischarge prevention circuit is mounted. The operating portion 12 is cut out and formed integrally with the outer case 10 as a spring piece. As shown in FIG. 5B, a first metal piece 18 is disposed on the back side of the spring piece 12, and presses the periphery of the outer projection 14 of the spring piece 12 and pushes it into the outer case 10. For example, the first metal piece 18 is pressed by the inner projection 16 of the spring piece 12 to contact the second metal piece 20 inside the electric device, and the contact is closed. When the spring piece 12 is released from the pressing, the spring piece 12 returns to its original position again by its elastic restoring force, and the first metal piece 18 is moved to the second metal piece 20.
Away from it and the contacts are opened. The contact is closed only while the spring piece is being pressed, and functions as a momentary switch. If the switches SW2 and SW3 are formed using the outer surface of the outer case of the electric device, they can be provided at very low cost.

<< Fourth Embodiment >> FIG. 6 shows a fourth embodiment of an overdischarge prevention circuit for a primary battery B according to the present invention. In this circuit, a capacitor C1 is provided in parallel with a resistor R4 between the terminals of the circuit shown in FIG. The capacitor C1 plays a role of delaying and transmitting the divided output of the voltage detection circuit 4 to the control switching element Q2. That is, it functions as a delay circuit. The reason why the divided output of the voltage detection circuit 4 is transmitted to the control switching element Q2 with a delay is as follows. That is, the load Z connected to the overdischarge prevention circuit according to the present invention includes a pulse load Z in which an intermittent current flows from a battery, including a transmission / reception circuit of a communication device such as a mobile phone or a PDA. When a large pulse current flows through such a load Z, as shown in FIG. 7, the battery voltage may temporarily decrease in accordance with the pulse and fall below the cutoff voltage. If the battery voltage falls below the cutoff voltage even for a moment, the discharge stop function is activated, and the power supply to the load Z may be stopped.

If the capacitor C1 is interposed in parallel with the resistor R4 as in the present embodiment, even if the battery voltage temporarily drops, the reduction of the divided output can be suppressed by the capacitor C1. As long as the voltage does not continuously decrease for a certain period of time or longer, it is possible to prevent the control switching element Q2 from being turned off.

Further, in the circuit of this embodiment, even when the switch SW1 is closed, the time until the control switching element Q2 is turned on is delayed. Therefore, even if the switch SW1 is closed by mistake, the switch SW1 is closed. If the time is short, it is not necessary to turn on the main switching elements Q1 and Q2, and it is possible to prevent the power supply path from being opened.

In this embodiment, the voltage detection circuit 4
Is connected in parallel with a capacitor C1 between both ends of a resistor R4. However, the delay circuit according to the present invention is not limited to this, and other well-known delay circuits may be applied. You may. This delay circuit may be interposed between the control circuit and the main switching element Q1 in addition to being interposed between the voltage detection circuit and the control circuit.

<< Fifth Embodiment >> FIG. 8 shows a fifth embodiment of an overdischarge prevention circuit for a primary battery B according to the present invention. This circuit distributes the power supply path 2 of the battery B to a plurality of power supply systems 2A, 2B, and 2C to supply power to a plurality of circuits (here, a TX circuit (transmission circuit), an RX circuit (reception circuit), and an audio circuit). This is a multi-system power supply circuit.

In this circuit, each power supply system 2A, 2B, 2
C are respectively provided with switching elements Q6 to Q8 for opening and closing the power supply systems 6A, 6B, and 6C, respectively.
Switching elements Q3 to Q5 for controlling ON / OFF of the switching elements Q6 to Q8 are connected to the respective switching elements Q6 to Q8.
The power supply controller 2 controls the switching elements Q3 to Q5 and individually controls on / on control of the switching elements Q3 to Q5.
0.

The power supply controller 20 includes a power supply path 2D independent of the power supply systems 2A, 2B, and 2C of the above-described circuits.
Is supplied from the battery B through And battery B
When the power supply from is stopped, the power supply controller 20 turns off the switching elements Q3 to Q5. As a result, the switching elements Q6 to Q8 are turned off, and the power supply systems 2A, 2B, and 2C are shut off.
The switching elements Q3 to Q5 are each formed of an NPN transistor, and the switching elements Q6 to Q5
Each of Q8 is constituted by a MOSFET. Resistors R6 to R8 are provided between the base and emitter of each of the switching elements Q3 to Q5, and resistors R9 to R11 are provided between the gate and the source of each of the switching elements Q6 to Q8. .

In this embodiment, an overdischarge prevention circuit is provided only for the power supply path 2D from the battery B to the power supply controller 20. That is, as shown in FIG. 8, a main switching element Q1 is provided on one side of a power supply path 2D from the battery B to the power supply controller 20, and a resistor R2 is provided between the base of the main switching element Q1 and the other power supply path 2D. A control switching element Q2 is interposed in series, and a resistor R3 is provided as a voltage detection circuit between the power supply paths 2D.
And R4, and the midpoint between the resistors R3 and R4 is connected to the base of the control switching element Q2. Between the base and the emitter of the main switching element Q1, a resistor R4 and a switch SW1 are connected in parallel.
A bypass path 8 is provided between the base of the main switching element Q1 and the base of the control switching element Q2, and the bypass path 8 is provided with a resistor R5 and a switch SW1.

When the battery voltage drops and the divided output from the resistors R3 and R4 falls below the reference voltage, the control switching element Q2 turns off and the main switching element Q1 turns off. As a result, the power supply path 2D from the battery B to the power supply controller 20 is cut off, and the power supply controller 20 is stopped. When the power supply controller 20 is stopped, the switching elements Q3 to Q5 are turned off, whereby the switching elements Q6 to Q8 that open and close the power supply systems 2A, 2B, and 2C are turned off. The power supply system 2A, 2B, 2C from the battery B to each circuit is also shut off, and the discharge of the battery B is completely stopped.

As described above, the power supply path 2 includes a plurality of power supply systems 2
In the case of a system in which the power is distributed to the power supply systems A, 2B, and 2C, the power supply path 2D to the power supply controller 20 that controls opening and closing of the power supply paths 2A, 2B, and 2C is cut off, so that the power supply system 2A, 2B , 2C can be cut off collectively. Since it is not necessary to separately provide an overdischarge prevention circuit for each of the power supply systems 2A, 2B, and 2C, the number of components can be reduced, and all the power supply systems 2A, 2B, 2C, and 2D are collectively shut off. Since there is no need to perform this operation, it is possible to use a relatively inexpensive switching element for small signals, thereby reducing the cost.

The main switching element Q1 and the control switching element Q2 of the overdischarge prevention circuit according to the present invention.
As for, a field effect transistor such as a MOSFET may be used in addition to the PNP transistor and the NPN transistor described above.

[0050]

According to the first aspect of the present invention,
By providing the voltage detection circuit on the load side of the main switching element, when the main switching element is turned off, it is not necessary to supply a weak current to the voltage detection circuit, and the battery is reliably stopped discharging. Can be. on the other hand,
When a new battery is replaced, the power supply voltage of the new battery can be input to the control circuit through the bypass path without passing through the main switching element by closing the bypass open / close switch. Then, the power supply from the battery to the load can be resumed.

According to the second aspect of the present invention, since the main switching element is constituted by a PNP transistor, the current supplied from the battery to the load can be reduced by the relationship between the base current of the PNP transistor and hfe. Limits can be added and the load can be protected from overcurrent.

According to the third aspect of the present invention, the control circuit is controlled to be turned on / off in response to the detection voltage from the voltage detection circuit to control the main switching element to be turned on / off. If it is constituted by the elements, the on / off control of the main switching element can be easily performed.

According to the fourth aspect of the present invention, the main switching element is constituted by a bipolar transistor or a field effect transistor, and short-circuited between the base and the emitter or between the gate and the source. Is provided, the main switching element can be cut off by the short-circuit switch, whereby the power supply path from the battery to the load can be forcibly cut off. It can be easily configured.

According to the fifth aspect of the present invention, the control switching element is constituted by a bipolar transistor or a field effect transistor, and short-circuited between the base and the emitter or between the gate and the source. If a switch is provided, the control switching element can be cut off by the short-circuit switch, thereby turning off the main switching element and forcibly interrupting the power supply path from the battery to the load. A switch for stopping power supply can be configured very simply.

According to the invention of claim 6 of the present invention, the bypass switch and the short-circuit switch connected to the main switching element are constituted by one double-throw switch, so that the number of parts can be reduced. The cost can be reduced by the reduction.

According to a seventh aspect of the present invention, there is provided a delay circuit for delaying signal transmission from the voltage detection circuit to the control circuit or from the control circuit to the switching element. Therefore, when the load is a pulse load Z in which an intermittent current flows, the discharge stop function is erroneously activated even if the battery voltage drops momentarily, and the load Z
It is possible to prevent the power supply to the power supply from being stopped.

According to the invention of claim 8 of the present invention, since the delay circuit is constituted by a capacitor, the delay circuit can be configured very simply.

Further, according to the ninth aspect of the present invention, according to the multi-system power supply circuit having the circuit for preventing over-discharge of the primary battery, the power supply system to the power supply controller is cut off, so that the battery can be connected to each power supply system. Power supply can be cut off collectively.
Since it is not necessary to provide an overdischarge prevention circuit for each power supply system individually, it is possible to reduce the number of components, and it is not necessary to shut off all power supply systems at once, so relatively inexpensive small A switching element for a signal can be used, so that cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of a circuit for preventing overdischarge of a primary battery according to the present invention.
FIG. 2 is a circuit diagram illustrating the embodiment.

FIG. 2 is a diagram illustrating a second embodiment of an overdischarge prevention circuit for a primary battery according to the present invention.
FIG. 2 is a circuit diagram illustrating the embodiment.

FIG. 3 is a diagram illustrating a third embodiment of an overdischarge prevention circuit for a primary battery according to the present invention.
FIG. 2 is a circuit diagram illustrating the embodiment.

FIG. 4 is a circuit diagram showing another embodiment of the overdischarge prevention circuit of the primary battery shown in FIG.

FIG. 5 is a cross-sectional view and a front view showing an embodiment of a switch constituting an overdischarge prevention circuit for a primary battery according to the present invention.

FIG. 6 shows a fourth embodiment of the overdischarge prevention circuit for a primary battery according to the present invention.
FIG. 2 is a circuit diagram illustrating the embodiment.

FIG. 7 is a graph showing the relationship between battery voltage and time when a pulsed load is connected.

FIG. 8 is a circuit diagram showing an embodiment of a multi-system power supply circuit including a primary battery overdischarge prevention circuit according to the present invention.

FIG. 9 is a circuit diagram showing an example of a conventional overdischarge prevention circuit for a primary battery.

[Explanation of symbols]

 Reference Signs List 2 power supply path 4 voltage detection circuit 8 bypass path 20 power supply controller R1 to R11 resistance Q1 main switching element Q2 control switching element D1 Zener diode SW1 to SW4 switch

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoyuki Akaya 5-36-11 Shimbashi, Minato-ku, Tokyo FDC Corporation F-term (reference) 2G016 CB12 CC01 CC02 CC04 CC07 CC12 CD04 CD06 CD09 CD10 CD14 5G003 BA01 DA02 DA13 GA01 GC06 5H025 MM01 5H030 AA04 AS11 AS14 BB21 BB27 FF44

Claims (9)

[Claims] 1. A main switching element provided on a power supply path from a primary battery to a load to open and close the power supply path, and a voltage provided on the load side of the main switching element to detect a power supply voltage to the load. A detection circuit;
A control circuit that turns off the main switching element when a detection voltage of the voltage detection circuit falls below a set voltage; and a bypass circuit that connects the battery side of the main switching element and the input side of the control circuit to bypass the switching element. An overdischarge prevention circuit for a primary battery, comprising: a bypass path interposed therebetween; and a bypass on / off switch for opening and closing the bypass path. 2. The circuit for preventing overdischarge of a primary battery according to claim 1, wherein the main switching element is constituted by a PNP transistor. 3. The control circuit according to claim 1, further comprising a control switching element that is turned on / off in response to a detection voltage from the voltage detection circuit and controls on / off of the main switching element. Claim 1 or 2
An overdischarge prevention circuit for a primary battery according to claim 1. 4. The device according to claim 1, wherein said main switching element is constituted by a bipolar transistor or a field effect transistor, and a short-circuit switch for short-circuiting between said base and emitter or between gate and source is provided. 2. The circuit for preventing overdischarge of a primary battery according to 1. 5. The control switching element comprises a bipolar transistor or a field-effect transistor, and a short-circuit switch for short-circuiting between the base and the emitter or between the gate and the source is provided. Item 4. An overdischarge prevention circuit for a primary battery according to Item 3. 6. The circuit according to claim 1, wherein the bypass switch is connected to the short-circuit switch connected to the main switching element.
5. The circuit for preventing overdischarge of a primary battery according to claim 4, wherein the circuit comprises two double throw switches. 7. The semiconductor device according to claim 1, further comprising a delay circuit for delaying signal transmission from said voltage detection circuit to said control circuit or from said control circuit to said switching element. 13. An over-discharge prevention circuit for a primary battery according to item 10. 8. The over-discharge prevention circuit for a primary battery according to claim 7, wherein a capacitor is connected in parallel from the voltage detection circuit to the control circuit as the delay circuit. 9. A plurality of power supply systems for individually supplying power to a plurality of loads from a primary battery, a system-specific switching element provided in each power supply system to open and close each power supply system, A power supply controller for individually controlling on / off of the switching elements;
A controller power supply system that is provided separately from the plurality of power supply systems and supplies power from the battery to the power supply controller, wherein the power supply is performed when power supply from the battery to the power supply controller is stopped. In a multi-system power supply circuit in which a controller turns off all of the system-based on / off switching elements and shuts off all of the power supply systems, the main switching elements are provided in the controller power supply system, and the main switching elements are provided on the power supply controller side. A voltage detection circuit for detecting a power supply voltage to the power supply controller, wherein the control circuit turns off the main switching element when a detection voltage of the voltage detection circuit falls below a set voltage. Item 10. Prevention of overdischarge of the primary battery according to any one of Items 1 to 7 Multi-system power supply circuit with circuit.