JPH11266542A - Power source circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source circuit, capable of avoiding power supply to an electronic apparatus by detecting inverse connection of a plurality of batteries connected in series. SOLUTION: A plurality of batteries of an electronic apparatus 6, to which power is supplied from a plurality of the batteries connected in series, are divided into a plurality of blocks #1, #2. The connected states of batteries, which belong to the respective blocks and are connected in series, are detected by the respective comparators 10a, 10b. When inverse connection is detected in one block, outputs of an AND circuit 9 and an OR circuit 7 turn to low level. Switching transistors Q1, Q2 are turned off, and power supply to the electronic apparatus 6 is cur off. A plurality of the batteries connected in series are divided into plural blocks, and each of the connection states is detected, so that the difference between the lowest operation assurance voltage of the batteries and the highest voltage of the inverse connection becomes large. Thereby it is made easy to detect the connection state of batteries with the comparators.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device to which power is supplied from a plurality of batteries connected in series, and does not supply power to the electronic device when a battery connection state is detected and a reverse connection is detected. Power supply circuit.

[0002]

2. Description of the Related Art In an electronic apparatus to which power is supplied from a plurality of batteries connected in series, when a small number of batteries are reversely connected, the reversely connected batteries are charged and the electrolyte leaks.

[0003]

Conventionally, in order to solve the above problems, there is known a power supply device in which a battery is not physically connected even if the battery is connected in reverse as shown in FIG. This power supply device includes a chassis 1 constituting a battery housing.
A spring 3 to which the negative terminal 2b of the battery 2 is connected is attached to one of the chassis 1a and the other chassis 1b, and a depression 4 is formed in the other chassis 1b. A terminal plate 5 to which the terminal 2a is connected is provided. FIG. 3A shows a state in which the battery 2 is properly inserted into the battery housing having the above-described configuration. The negative terminal 2b of the battery 2 contacts the spring 3, and the positive terminal 2a of the battery 2 is a chassis. 1b is fitted into the depression 4 and comes into contact with the terminal plate 5.

On the other hand, when the battery 2 is erroneously inserted into the battery housing in the reverse direction, the positive terminal 2a of the battery 2 contacts the spring 3 as shown in FIG. Since the negative electrode terminal 2b is flat, it is not fitted into the recess 4 of the chassis 1b and therefore does not contact the terminal plate 5, so that even if the battery 2 is inserted in the reverse direction, reverse connection to the electronic device is prevented. You.

However, when the battery housing having the above-described structure is used in an electronic device, when the number of batteries increases, the battery housing having the above-described structure is employed for each battery, and they are electrically connected in series. This necessitates a complicated and dimensionally large wiring, and inevitably leads to high costs. The present invention has been made in view of the above problems, and proposes a power supply circuit that can electrically detect a reverse-connected battery and avoid power supply in an electronic device using a plurality of batteries.

[0006]

A power supply circuit according to the present invention divides a plurality of series-connected batteries into a plurality of blocks and detects a connection state of the plurality of batteries belonging to these blocks for each block. A state detection circuit is provided. By detecting the connection state of the battery for each block, the difference between the minimum operation guarantee voltage of the battery and the maximum voltage of the reverse connection is increased, and the detection of the reverse connection is facilitated.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic configuration of the power supply circuit of the present invention will be described with reference to FIG. The power supply circuit of the present invention
Dividing multiple batteries connected in series into multiple blocks,
The reverse connection is detected from the voltage between both ends of each block. Here, assuming that the number of batteries of a certain block divided into a plurality of blocks is N, the voltage in the block in the case of the normal connection is the maximum voltage = the voltage per new battery (about 1.7 V).
× N = 1.7N (V) Minimum operation guarantee voltage = Minimum operation guarantee voltage per one line (for example, 1.0 V) × N = N, and the supply of power is stopped or limited to the minimum operation guarantee voltage. Not be.

Next, when one battery of a certain block is reverse-connected, one of the reverse connection and one of the regular connection are canceled in terms of voltage, so that the maximum voltage of the reverse connection = new battery Voltage per line (approximately 1.7 V) × (N−2) = 1.7
(N-2) (V). Therefore, to detect a reverse connection, the maximum voltage of the reverse connection must be detected.

Therefore, in order to detect a reverse connection of a certain block, a voltage lower than the minimum operation guarantee voltage and higher than the highest voltage of the reverse connection may be detected. That is, N>
N and Vref satisfying Vref> 1.7 (N-2)
And reverse connection can be detected by detecting the voltage in the above range by a comparator or the like. Here, N becomes 4 or less from the condition that N is an integer, and Vref is set according to the value of N. With this setting, the difference between the minimum operation guarantee voltage and the maximum reverse connection voltage increases as N decreases (N = 2 when divided by 4 when the number of batteries is eight) or as the number of reverse connections increases. Therefore, it is easy to detect the reverse connection.

In the example of dividing eight batteries connected in series shown in FIG. 2, when N = 2, 2>Vref> 0, when N = 3, 3>Vref> 1.7, and when N = 4, 4>Vref> 1.7. Vref>
3.4, and the differences are 2V, 1.3V, and 0.3V, respectively.
It is understood that the difference between the minimum operation guarantee voltage and the reverse connection maximum voltage increases as the N becomes smaller, and that the detection by the comparator becomes easier.

As described above, in a plurality of battery-powered devices, a battery connected in series is divided into a plurality of blocks to detect a battery connection state, so that reverse connection of the battery can be easily detected. The leakage of the electrolyte can be prevented by stopping or limiting the power supply from the battery based on the above.

An embodiment of the power supply circuit according to the present invention based on the above principle will be described below with reference to FIG. The power supply circuit shown in FIG. 1 is a power supply circuit divided into two blocks # 1 and # 2 where the total number of batteries is eight and N = 4. Therefore, when N = 4 is substituted into the equation of N>Vref> 1.7 (N−2), 4>Vref> 1.7 (4-2) = 3.4. For example, Vref = 3.7V Set.

As shown in FIG. 1, a power supply terminal + B of the electronic device 6 is connected to a collector of a second switching transistor Q2 (hereinafter, referred to as a transistor Q2), and one end of a power supply switch S1 is connected to its emitter. . Further, bias resistors R1 and R2 are provided between the base and the emitter.
And the base is connected to the collector of a first switching transistor Q1 (hereinafter, referred to as transistor Q1) via the resistor R1. The emitter of the transistor Q1 is connected to the ground G, and its base is connected to the output terminal of the OR circuit 7 via the resistor R3. The switching circuit 8 is turned on / off by the transistors Q1 and Q2 according to the connection state of the battery.

The OR circuit 7 has two input terminals,
One input terminal of the OR circuit 7 is connected to the output terminal of the AND circuit 9, and the other input terminal is connected to the transistor Q2.
Are connected to the ground G via a resistor C4 and a capacitor C. An integrating circuit is formed by the resistor R4 and the capacitor C. The operation of the integrating circuit will be described later.

The AND circuit 9 has input terminals corresponding to the number of divided blocks. In this embodiment, the AND circuit 9 is divided into two blocks, and thus has two input terminals. One input terminal of the AND circuit 9 is connected to the output side of the comparator 10a, and the other input terminal is connected to the output side of the comparator 10b. The non-inverting input terminals of the comparators 10a and 10b are respectively connected to the positive electrodes of the batteries of blocks # 1 and # 2 obtained by dividing eight series-connected batteries into two, and are set to the inverting input terminals. Voltage sources Ref1, Ref2
Are connected respectively. Thus, the AND circuit 9, the comparators 10a and 10b, the set voltage source Ref1, and the set voltage source Ref2 constitute a battery connection state detection circuit.

Hereinafter, the operation of the power supply circuit will be described. When the power switch S1 is turned on, voltages are respectively applied to the OR circuit 7, the AND circuit 9, the comparators 10a and 10b via the constant voltage circuit 12, and the four battery blocks # 1 and # 2 are connected in reverse. Comparator 10a and comparator 10b detect whether the connection is normal or not. Here, since N = 4, VRef
1 = VRef2 = 3.7V is set.

First, when the batteries belonging to both blocks are properly connected, the outputs of the comparators 10a and 10b are both at the high level. As a result, the output of the AND circuit 9 is at the high level and the output of the OR circuit 7 is at the high level. High level, the transistors Q1 and Q2
Are turned on, the + B terminal of the electronic device 6 and the ground terminal G
Eight batteries are connected in series to supply power to the electronic device 6.

On the other hand, when either or both of the blocks # 1 and # 2 have a battery that is reversely connected,
The voltage generated in each block is (4 × 1.7) −
(2 × 1.7) = 3.4 V, and the voltage between the block terminals becomes smaller than the set voltage of 3.7 V. Therefore, the outputs of the comparators 10 a and 10 b both become low level, The output and the output of the OR circuit 7 become low level, and the transistors Q1,
Even when the transistor Q2 is turned off and the power switch S1 is turned on, the power is not supplied to the electronic device 6 because the transistor Q2 is turned off. As described above, when a battery that is reversely connected is present in any of the divided blocks, power is not supplied to the electronic device by detecting that, and charging of the battery that is reversely connected is avoided.

Here, the reason why the integration circuit composed of the resistor R4 and the capacitor C is inserted between the input terminal of the OR circuit 7 and the collector of the transistor Q2 is that the connection of the battery is normal and the electronic equipment is connected. When power is supplied to the electronic device 6 and the electronic device 6 is in use, and a large-amplitude signal is input to the electronic device 6 and a large current flows in the normal use condition, a plurality of serially connected devices belonging to each block are connected. The voltage between both terminals of the battery may drop below the set voltage and a low level may be output momentarily from the comparator, and the power supply is cut off even though the connection is in a normal state. It may cause malfunction.

Therefore, after the power switch S1 is turned on, a time constant of the resistor R4 and the capacitor C, that is, an operation of detecting whether the capacitor C is charged or not is determined until the capacitor C is charged. Thereafter, when the normal connection is detected, when the collector output of the transistor Q2 is input to the base of the transistor Q1 through the loop of the integration circuit and the OR circuit 7, the transistor Q1 turns on in the electronic device use state. Therefore, malfunction due to a voltage drop when the electronic device is used can be avoided.

Further, as shown in the drawing, a display means such as a light emitting diode 14 is provided between the output side of the AND circuit 9 and the ground G via an inverter 13 so that the light emitting diode or the like is made conductive at the time of reverse connection to provide the user with a display. You can let it know.

As described above, even if the user mistakenly connects the battery to the electronic device, the connection state can be immediately detected and the power supply can be stopped, so that the reversely connected battery can be prevented from being charged.

In the power supply circuit, the power switch S1
Is turned off, the input impedance of the comparator is set to a high impedance in order to reduce the discharge of the battery when the electronic device is not used. As an example, it is preferable to use a comparator constituted by a MOS-FET having an extremely large input impedance.

[0024]

According to the power supply circuit of the present invention, since a plurality of batteries connected in series are divided into a plurality of blocks and the connection state of the batteries in each block is detected, the state of reverse connection is detected. It becomes easy to do.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply circuit of the present invention.

FIG. 2 is a circuit diagram showing a connection example of a battery for explaining the principle of the power supply circuit of the present invention.

FIG. 3 is an explanatory view of a conventional battery housing in which reverse connection of a battery is prevented.

[Explanation of symbols]

6, electronic equipment 8, switch circuit 11, battery connection state detection circuit # 1, # 2, divided battery blocks 10a, 10
b ・ ・ Comparator

Claims (4)

[Claims] In a power supply circuit of an electronic device using a plurality of batteries connected in series as a power source, the plurality of batteries connected in series are divided into a plurality of blocks, and a connection state of a plurality of batteries belonging to these blocks is provided. A power supply circuit, comprising: a battery connection state detection circuit for detecting the state of each block. 2. When a reverse connection state of a battery is detected from at least one block of the plurality of blocks, power supply to the electronic device is turned off, and a normal connection state of the battery is detected from all blocks of the plurality of blocks. 2. The power supply circuit according to claim 1, further comprising a switch circuit that turns on power supply when the power supply is detected. 3. An electronic device to which power is supplied from a plurality of batteries connected in series, and a plurality of the batteries connected in series divided into a plurality of blocks, and connection of the batteries connected in series belonging to each block. A plurality of comparators each detecting a state, an AND circuit to which output terminals of the plurality of comparators are connected, an OR circuit to which an output terminal of the AND circuit is connected, and a second circuit which is turned on / off according to an output of the OR circuit. A power supply circuit comprising: one switching transistor; and a second switching transistor connected to the first switching transistor and connected to a power supply terminal and a power switch of the electronic device. 4. The power supply circuit according to claim 3, wherein an integration circuit is connected between said second switching transistor and an input terminal of said OR circuit.