JPH088745B2 - Battery charge / discharge circuit - Google Patents

Description

The present invention relates to a battery charging / discharging circuit that supplies a charging current to a battery from a charger and also supplies power to a load, and supplies current to the load from the battery when the charger is stopped, and more particularly to a battery. This is related to the protection of the battery and the load when the polarity is reversed. Conventionally, a circuit shown in FIG. 3 has been proposed as this type of circuit. In this operation, when the battery B is connected to the regular polarity, the relay contact rl ₁ is made, and when the battery B is connected to the opposite polarity, the relay contact rl ₁ is broken and the load L is applied with a voltage of the opposite polarity to the normal polarity. This is to prevent it from getting scratched.

However, when battery B is replaced during operation of this device, if battery B is reversely connected, relay contact rl
_{Since 1} is already made, an excessive current will flow through the diode D ₁ connected in parallel with the load L until the relay detects a reverse connection and breaks the contact Fuse F ₁
Or the diode D ₁ may be damaged.

Therefore, the relay RL1 has a drawback that it requires an extremely fast operation time and a large breaking capacity. Further, the diode D ₁ needs to have a large overcurrent capacity.

INDUSTRIAL APPLICABILITY When the battery is connected in parallel to the charger and the load, even if the battery is connected in the opposite polarity, the normal operation can be restored without damaging the components and the load without damage. A circuit for enabling the above is provided, and a semiconductor switch circuit for switching a circuit for supplying a charging current and a discharging current of the battery is provided between the charger and the battery, and the switch circuit is provided by detecting a connection polarity of the battery. It is characterized by having a control circuit for controlling. This will be described below with reference to the drawings. 1 and 2 are circuit diagrams of an embodiment of the present invention, and FIG. 4 is a diagram for explaining the operation in comparison with the conventional example. In the figure, 1 is a semiconductor switch circuit, 2 is a control circuit, Tr1 and Tr2 are bipolar transistors, D1 and D2 are diodes, and R1 to R3 are resistors. The operation of this circuit is that, when the battery B is properly connected, the base current is supplied to the transistor Tr1 through the diode D1 and the resistor R1 to conduct Tr1 so that the charging current flows to the battery and the power to the load L is supplied. To do. Also, when the battery B is discharged, a diode
Power the load L through D2.

Furthermore, when battery B is connected to the opposite polarity, such as when replacing battery B while the device is operating, the reverse polarity is detected by resistors R2 and R3, transistor Tr2 is reverse biased and becomes non-conductive, and base current is applied to transistor Tr1. The supply is stopped and the transistor Tr2 is immediately turned off. 4A and 4B are characteristic diagrams showing the relationship between the discharge current (vertical axis) and the operating time (horizontal axis) of the battery comparing the present invention and the conventional example. FIG. 4A is a conventional example, and FIG. ) The figure shows the characteristics of the present invention. That is, according to the present invention, the discharge flow at the time of reverse connection of the battery is small and the operation time is short, so that the fuse and the load are not damaged. FIG. 3 shows another embodiment of the present invention. MOSTr is a MOS-FET, Tr2 and Tr3 are bipolar transistors, D1 is a diode, DZ1 is a constant voltage diode, R1 to R4 are resistors, and L1 is an inductor. . This circuit uses a MOS-F instead of Tr1 and D1 in the above embodiment (FIG. 1).
Using ET, the battery charging current is made to flow from the drain to the source of the MOS-FET and the discharging current is made to flow from the source to the drain. Note that L1 is an impedance that enables R2 and R3 to detect the reverse polarity of the battery even if there is a wiring drop on the battery side. or
The block consisting of Tr3, R4, and DZ1 is a circuit for speeding up the turn-off of Tr1.

As is clear from the above description, according to the present invention, by using the semiconductor switch as a switch that cuts off the discharge current of the battery when the battery is connected in the reverse polarity, it is possible to cut off the battery as compared with the case where the conventional relay is used. The speed is extremely fast, and there is no risk of damaging the fuse or load. In addition, it is not necessary to connect a diode in parallel with a load such as D1, which is a great practical effect.

[Brief description of drawings]

1 and 2 are circuit diagrams of an embodiment of the present invention, FIG. 3 is a conventional circuit diagram, and FIG. 4 is a characteristic explanatory view comparing the conventional example and the embodiment of the present invention. In the figure, 1 is a semiconductor switch circuit, 2 is a control circuit, CH is a charger, B is a battery, L is a load D _01.
~ D ₂ is a diode, Tr ₁ ~ Tr ₃ is a transistor, R ₁ ~ R ₄ is a resistor, MOS Tr is a MOS field effect transistor, L ₁ is an inductor, RL ₁ is a relay, rl ₁ is a contact, DZ ₁ is a constant voltage diode Is.

Claims (4)

[Claims] 1. A battery charging / discharging circuit connected to charge a battery by a charger and to supply a load connected in parallel with the battery from the battery when the operation of the charger is stopped. A battery charging / discharging characterized in that a semiconductor switch circuit for switching between a circuit for supplying a charging current and a discharging current of the battery is provided between the battery and a control circuit for detecting the connection polarity of the battery and controlling the semiconductor switching circuit. circuit. 2. The battery charging / discharging circuit according to claim 1, wherein an antiparallel circuit of a bipolar transistor and a diode is used as the switch circuit. 3. The battery charging / discharging circuit according to claim 1, wherein a MOS field effect transistor is used as the switch circuit. 4. A battery charging / discharging circuit according to claim 1, wherein an inductor is inserted between the switch circuit and the control circuit.