JPH11113180A - Series discharge circuit for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate an adverse effects on a load at the time of disconnecting a battery by a switch, when the battery is fully discharged. SOLUTION: When a battery 2 is fully discharged, a voltage monitor means 3 disconnects the battery 2 from a circuit by a switch 4. When the battery 2 is disconnected, the charges stored in a capacitor 21 by the battery 2 are discharged, and the voltage across the load 11 changes gradually. Therefore, the adverse effects on the load 11 caused by an abrupt drop of the voltage across the load 11 can be eliminated when the switch 4 disconnects the battery 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery series discharge circuit in which a battery reaching a discharge end voltage is disconnected from a series circuit, and the remaining batteries supply current to a load via a bypass.

[0002]

In general, in a series discharge circuit in which a plurality of batteries having a set discharge end voltage are connected in series to a load to perform a discharge, the variation in the individual batteries causes the battery to be faster than other batteries. Unless the battery that has reached the discharge end voltage is disconnected more quickly than the series circuit, the discharged battery is reversely charged by another battery, which causes problems such as shortening the life of the battery. Therefore, conventionally, when one of the batteries connected in series to the load reaches the discharge end voltage, the battery is disconnected from the circuit by the switch means, and the load is removed from the remaining batteries by the bypass means connected between both ends of the battery. A series discharge circuit of a battery for supplying a current to a battery has been proposed.

FIG. 3 shows an example of a series discharge circuit of the battery. In FIG. 1, reference numeral 1 denotes a discharge circuit connected in series to a load 11, to which a secondary battery such as a nickel-cadmium battery or the like, which can repeatedly perform charging and discharging, that is, a battery 2, is connected. .
Reference numeral 3 denotes voltage monitoring means for monitoring the voltage across the battery. When the voltage across the battery 2 reaches the discharge end voltage, the voltage monitoring means 3 is connected to the battery 2 in series with a semiconductor such as a transistor. The switch means 4 using a switch is turned off to disconnect the battery 2 from the discharge circuit 1.

In each discharge circuit 1, a diode 5 serving as a bypass means is connected in parallel between a series circuit of the battery 2 and the switch means 4. This diode 5 has a cathode connected to the anode side of the battery 2 and an anode connected to the cathode side of the battery 2. When the switch means 4 is in the ON state, a current flows in the reverse direction through the diode 5. When the battery 2 reaches the end-of-discharge voltage and the switch 4 is turned off, the diode 5
The current from the other battery 2 is supplied to the load 11 via the.

However, as shown in the graph of FIG. 4 showing the voltage change across the load 11 during discharging, such a battery series discharging circuit, when an arbitrary battery 2 reaches the discharge end voltage, When the switch means 4 connected to the load 11 is turned off, there is a problem that the voltage across the load 11 drops sharply and adversely affects the load 11.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a series discharge circuit of a battery which does not adversely affect a load when disconnecting the switch means.

[0007]

In order to achieve the above object, a series discharging circuit for a battery according to the present invention comprises a plurality of batteries connected in series to a load, and when any battery reaches a discharge termination voltage, a switch means. And a capacitor is connected to both ends of the bypass means in a battery series discharge circuit in which current is supplied from the remaining batteries to the load by the bypass means connected between both ends of the battery. .

According to this configuration, when the battery reaches the discharge end voltage and the battery is disconnected from the circuit by the switch means, the charge stored in the capacitor by the battery is discharged, and the voltage across the load is reduced. Changes slowly. Therefore, when the switching means is disconnected, it is possible to eliminate the adverse effect on the load due to the sharp drop in the voltage across the load.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a battery series discharge circuit according to the present invention will be described below with reference to the accompanying drawings. In FIG. 1 showing the circuit diagram, the same parts as those in FIG.

In FIG. 1, each discharge circuit 1 in this embodiment includes a capacitor 21 which is charged by energy from the battery 2 and discharged when the battery 2 is disconnected by the switch means 4, and includes a diode 5 serving as a bypass means. Are connected to both ends. Otherwise, it has the same configuration as the circuit shown in FIG.

Next, the operation of the above configuration will be described with reference to the graph of FIG. When the voltage between both ends of the battery 2 is equal to or higher than the discharge end voltage, the switch means 4 is turned on by the voltage monitoring means 3 for monitoring the voltage, and a circuit in which the battery 2 is connected in series to the load 11 is formed. Is supplied from the battery 2 to the load 11. At the same time, in each discharge circuit 1, a closed circuit of the battery 2 → the capacitor 21 → the switch means 4 → the battery 2 is formed,
The capacitor 21 is charged to the same voltage as the battery 2.

Thereafter, as the battery 2 discharges, when the voltage across the battery 2 decreases to the discharge end voltage, the voltage monitoring means 3 turns off the switch means 4 to discharge the battery 2 which has reached the discharge end voltage. Separate from circuit 1 sequentially. Then, since charges are accumulated in the capacitor 21, the voltage across the load 11 changes gradually due to the discharge of the capacitor 21. When the capacitor 21 is completely discharged, current is supplied from another battery 2 to the load 11 via the diode 5.

In this case, the time t0 from when the battery 2 is disconnected from the discharge circuit 1 by the switch means 4 until the voltage across the capacitor 21 is completely discharged can be expressed by the following equation.

[0014]

(Equation 1)

Where Ic is the discharge current of the capacitor 21, Vc
c is the voltage across the capacitor 21 and C is the capacitance of the capacitor 21. That is, only by appropriately selecting the capacitance of the capacitor 21, it is possible to obtain a desirable discharge time t0, and thus a change in voltage across the load 11.

As described above, in this embodiment, a plurality of batteries 2 are connected in series to the load 11, and when any battery 2 reaches the discharge end voltage, the battery 2 is disconnected by the switch means 4 and A capacitor 21 is connected to both ends of the diode 5 in a series discharge circuit of batteries for supplying current from the remaining battery 2 to the load 11 from a diode 5 which is a bypass means connected between both ends of the diode 5. With this configuration, when the battery 2 reaches the discharge end voltage and the battery 2 is disconnected from the circuit by the switch means 4,
The electric charge stored in the capacitor 21 is discharged by the battery 2 until then, and the voltage across the load 11 changes gradually.
Therefore, when the switch means 4 is disconnected, the load 11
It is possible to eliminate an adverse effect on the load 11 caused by a sharp drop in the voltage at both ends. Also, by using the capacitor 21, the load at the time of disconnecting the battery 2 can be reduced.
Since the voltage change of 11 only needs to consider the capacitance C of the capacitor 21, there is also an advantage that the setting is simplified.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, the switch means 4 is not limited to a semiconductor switch, but may be a relay or the like.
Also, the diode 5 disclosed in the embodiment as a bypass unit may be replaced by a circuit or element exhibiting the same function.

[0018]

According to the battery series discharge circuit of the present invention, a plurality of batteries are connected in series to a load, and when any battery reaches a discharge end voltage, the battery is disconnected by switch means.
In a battery series discharge circuit for supplying current from the remaining battery to the load by a bypass means connected between both ends of the battery, a capacitor is connected to both ends of the bypass means. And a series discharge circuit for the battery that does not adversely affect the battery.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a graph showing a voltage change between both ends of a load at the time of discharging.

FIG. 3 is a circuit diagram showing a conventional example.

FIG. 4 is a graph showing a change in voltage between both ends of a load during a discharge according to the first embodiment;

[Explanation of symbols]

 2 Battery 4 Switching means 5 Diode (bypass means) 11 Load 21 Capacitor

Claims (1)

[Claims] 1. A plurality of batteries are connected in series to a load, and when any battery reaches a discharge end voltage, the battery is disconnected by a switch means, and the remaining batteries are separated from bypass batteries connected between both ends of the battery. A battery series discharge circuit for supplying current to said load, wherein capacitors are connected to both ends of said bypass means.