JPH10313544A - Overcharge preventing circuit, overdischarge preventing circuit and charge/discharge control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overcharge of batteries connected in series with a simple circuit configuration, by providing a detector for sequentially detecting charging states of the batteries, providing an overcharge preventing discharging circuit connected to one of the batteries, and selectively connecting the discharging circuit to the battery of highest charging state. SOLUTION: A control circuit 54 sequentially monitors charging states of batteries B1 to Bn based on battery voltages sequentially detected by a voltage detector 51 and past battery voltage stored in a memory 53 at the time of charging the batteries B1 to Bn. And, when any of the batteries B1 to Bn indicates a specific or more charging state, the circuit 54 outputs a control signal indicating which is the battery indicating the highest charging state of them. A switch change-over circuit 91 receives this signal and connected a charging circuit 6 in parallel with the designated battery. Thus, thereafter, the discharging circuit is sequentially connected to the battery indicating the highest charging state, and hence the charging states of all the batteries B1 to Bn are made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an overcharge prevention circuit, an overdischarge prevention circuit, and a charge / discharge control circuit for preventing overcharge or overdischarge of a plurality of batteries connected in series.

[0002]

2. Description of the Related Art When charging and discharging a plurality of batteries to be charged connected in series, there is a problem in that overcharging or overdischarging of the batteries occurs due to variations in characteristics among the individual batteries. In other words, when a plurality of batteries connected in series include a battery with a smaller capacity than the other batteries, even if the battery with a small capacity reaches a full charge, the battery as a whole still has a full charge. If not, charging will continue. as a result,
Small capacity batteries lead to overcharging. Similarly, even if the small-capacity battery is in the discharge stop state, if the entire battery is in a dischargeable state, the discharge is continued thereafter, and the small-capacity battery is in an overdischarged state.

Therefore, a circuit for preventing overcharging or overdischarging of a plurality of batteries to be charged connected in series and bringing them into the same charged state or discharged state is disclosed in Japanese Patent Laid-Open No. 7-1995.
No. 163060.

[0004] The circuit described in the publication has an overcharge prevention circuit for each battery so that none of the batteries is overcharged or overdischarged even if there are variations in a plurality of batteries connected in series. An overdischarge prevention circuit. The overcharge prevention circuit includes a diode connected in series to the battery, a switching element that bypasses a charging current, and a voltage detector that controls on / off of the switching element. On the other hand, the overdischarge prevention circuit includes a switching element connected in series to the battery, a diode that bypasses a discharge current, and a voltage detector that controls on / off of the switching element.

[0005] In such a circuit, when a small-capacity battery is charged to a fully charged state when the battery is charged, an overcharge prevention circuit for the battery operates to bypass the charge current of the battery and to overcharge the battery. Prevent charging. Other batteries are subsequently charged, and all batteries are fully charged without being overcharged.

[0006] On the other hand, when the battery is discharged, if the small capacity battery is discharged to the discharge stop state, the overdischarge prevention circuit of the battery is activated, and the battery is overdischarged by discharging. To prevent Other batteries are discharged thereafter, and all batteries are discharged almost uniformly without being over-discharged.

[0007]

As described above, the circuit disclosed in the above publication can prevent overcharge or overdischarge of all batteries. However, since each battery is provided with an overcharge prevention circuit and an overdischarge prevention circuit, the number of circuit components is large and the circuit configuration becomes very complicated.

Further, since the diode constituting the overcharge prevention circuit is connected in series with the battery, energy loss due to the diode occurs. In particular, as the number of batteries connected in series increases, such energy loss also increases. Further, a switching element connected in series with the battery and constituting an overdischarge prevention circuit must have a rating corresponding to the discharge current capacity.

An object of the present invention is to prevent overcharge and overdischarge of a plurality of batteries connected in series with a simple circuit configuration.

[0010]

According to the present invention, an overcharge prevention circuit for preventing overcharge of a plurality of batteries connected in series includes a detection circuit for sequentially detecting the state of charge of each of the batteries, At least one connected to one of the
And a connection circuit for selectively connecting the discharge circuit to a battery in the highest charge state based on the detection result of the detection circuit.

An overdischarge prevention circuit for preventing overdischarge of a plurality of batteries connected in series includes a detection circuit for sequentially detecting a discharge state of each of the batteries, and an overdischarge prevention circuit connected to one of the batteries. And a connection circuit for selectively connecting the power supply circuit to the battery in the deepest discharge state based on the detection result of the detection circuit.

Further, a charge / discharge control circuit for preventing overcharge and overdischarge of a plurality of batteries connected in series includes a detection circuit for sequentially detecting a charge state and a discharge state of each of the batteries; At least one overcharge prevention discharge circuit connected to one of the above, at least one overdischarge prevention power supply circuit connected to one of the batteries, and detection of the detection circuit when the battery is charged. The discharge circuit is selectively connected to the battery in the highest charge state based on the result, and the power supply circuit is selected as the battery in the deepest discharge state based on the detection result of the detection circuit when the battery is discharged. And a connection circuit for electrically connecting.

[0013]

FIG. 1 is a block circuit diagram showing an embodiment of the present invention. B1 to Bn are a plurality of batteries to be charged connected in series, and are composed of a nickel cadmium battery, a nickel hydride battery, a lithium ion battery or the like. 1 is a charging circuit for charging these batteries B1 to Bn.
It comprises a well-known constant current charging circuit or constant voltage charging circuit depending on the type of batteries B1 to Bn. 2 is a charge switch inserted between the charging circuit 1 and the batteries B1 to Bn, 3 is a load driven by the batteries B1 to Bn, 4 is a load 3 and the battery B
1 is a discharge switch interposed between Bn.

Reference numeral 5 denotes a detection circuit for detecting the charge / discharge state of each of the batteries B1 to Bn. A voltage detection circuit 51 for sequentially detecting the battery voltage of each of the batteries B1 to Bn, A / D conversion circuit 52 for converting the A / D into a digital value, a storage circuit 53 for storing the battery voltage output from the A / D conversion circuit 52, and a battery voltage and storage circuit 53 output from the A / D conversion circuit 52 And a control circuit 54 for monitoring the charge / discharge state of each of the batteries B1 to Bn based on the battery voltage stored in the control circuit 54 and outputting a control signal.

The control circuit 54 comprises a microcomputer. At the time of charging the batteries B1 to Bn,
Based on the battery voltage sequentially detected by the voltage detection circuit 51 and the past battery voltage stored in the storage circuit 53, the state of charge of each of the batteries B1 to Bn is sequentially monitored. Then, when any of the batteries B1 to Bn shows a charge state equal to or higher than a specific value, a control signal indicating which battery has the highest charge state is output.

On the other hand, at the time of discharging the batteries B1 to Bn, if any one of the discharging states becomes lower than a specific state (for example, a specific battery voltage), the deepest discharging state (that is, the most A control signal indicating which battery is in the low voltage state) is output.

The above-mentioned specific charge state or discharge state is appropriately set according to the magnitude of the charge current or discharge current of the batteries B1 to Bn. For example, when the batteries B1 to Bn are discharged, the specific discharge state is set so as to be substantially proportional to the magnitude of the discharge current.

Reference numeral 6 denotes an overcharge preventing discharge circuit connected in parallel to one of the batteries B1 to Bn when the batteries B1 to Bn are charged, such as a resistor having an appropriate resistance value or a battery of the same type as the batteries B1 to Bn. Consists of Reference numeral 7 denotes an overdischarge prevention power supply circuit connected in parallel to one of the batteries B1 to Bn when the batteries B1 to Bn are discharged, or a battery of the same type as the batteries B1 to Bn, or a combination of the battery and an appropriate booster circuit. It comprises an appropriate external power supply circuit and the like. Reference numeral 8 denotes a discharging circuit 6 or a power supply circuit 7 corresponding to charging and discharging of the batteries B1 to Bn.
Switch.

Reference numeral 9 denotes a detection circuit 5 for charging the batteries B1 to Bn.
The discharge circuit 6 is selectively connected to the battery in the highest charge state based on the detection result, and power is supplied to the battery in the deepest discharge state based on the detection result of the detection circuit 5 when the batteries B1 to Bn are discharged. This is a connection circuit for selectively connecting the circuit 7. The connection circuit 9 includes a switch switching circuit 91 that responds to a control signal from the control circuit 54, and selection switches SW1 to SWn including relay switches and semiconductor switches.

The circuit operation of this embodiment will be described first when the batteries B1 to Bn are charged. At the start of charging, all the selection switches SW1 to SWn are turned off, and the changeover switch 8 is connected to the overcharge prevention discharge circuit 6 side.

The batteries B1 to Bn are charged by a charge switch 2
Is started by turning on. When the charging is started, the voltage detection circuit 51 sequentially detects the battery voltage of each of the batteries B1 to Bn periodically and outputs the battery voltage to the A / D conversion circuit 52. The control circuit 54 monitors the state of charge of each of the batteries B1 to Bn based on the battery voltage output from the A / D conversion circuit 52 and the battery voltage stored in the storage circuit 53.

When all of the batteries B1 to Bn have the same characteristics, there is no problem since the charging states of the batteries B1 to Bn change in exactly the same state. However, if this is not the case, the battery with the smallest capacity among the batteries B1 to Bn approaches the full-charge state earliest. Therefore, the control circuit 54 controls any one of the batteries B1 to Bn (tentatively, the battery B1).
, Exceeds a specific state of charge and assumes the highest state of charge, outputs a control signal.

In response to the control signal, the switch switching circuit 91 turns on the selection switch SW1 to connect the discharging circuit 6 to the battery B1 in parallel. Therefore, the charging rate of the battery B1 is made lower than that of the other batteries B2 to Bn, thereby preventing the battery B1 from being overcharged.

Thereafter, when a battery (for example, battery B2) having a higher charge state than battery B1 appears, switch switching circuit 91 switches the connection of discharging circuit 6 from battery B1 to battery B2. Thereafter, by sequentially connecting the discharge circuit 6 to the battery showing the highest charge state, all the batteries B1 to B
The state of charge of n is made uniform.

Next, the operation at the time of discharging the batteries B1 to Bn will be described. In starting the discharge, the selection switches SW1 to SWn are all turned off, and the changeover switch 8 is connected to the overdischarge prevention power supply circuit 7 side. The discharge of the batteries B1 to Bn is started by turning on the discharge switch 4. The voltage detection circuit 51 sequentially detects the battery voltages of the batteries B1 to Bn periodically,
Output to the D conversion circuit 52. The control circuit 54 monitors the discharge state of each of the batteries B1 to Bn based on the battery voltage output from the A / D conversion circuit 52 and the battery voltage stored in the storage circuit 53.

The control circuit 54 outputs a control signal when any one of the batteries B1 to Bn (assuming that the battery is B1) falls below a specific discharge state and is in the deepest discharge state. In response to the control signal, the switch switching circuit 91 turns on the selection switch SW1 to connect the power supply circuit 7 to the battery B1 in parallel. Therefore, the discharge rate of the battery B1 is made lower than that of the other batteries B2 to Bn, and an overdischarge state is prevented.

Thereafter, when a battery (for example, battery B2) having a charge state deeper than that of battery B1 appears, switch switching circuit 91 switches the connection of power supply circuit 7 from battery B1 to battery B2. Thereafter, by connecting the power supply circuit 7 to the batteries showing the deepest charge state in sequence, all the batteries B1 to B
With n, the discharge state is made uniform without being in an overdischarge state.

In this embodiment, the discharge circuit 6,
Although only one combination of the power supply circuit 7 and the changeover switch 8 is provided, if the number of batteries connected in series is extremely large, two sets of the combination of the discharge circuit 6, the power supply circuit 7, and the changeover switch 8 are provided. Alternatively, three sets may be provided. However, from the viewpoint of simplification of the circuit configuration, it is preferable that the number is as small as possible.

[0029]

According to the present invention, a discharge circuit is selectively connected to a battery in the highest charge state when charging the battery among a plurality of batteries connected in series, or when discharging the battery. Equipped with a connection circuit that selectively connects the power supply circuit to the battery that is in the deepest discharge state, preventing overcharge or overdischarge of all batteries without requiring a complicated circuit configuration, and ensuring uniform Can be charged or discharged.

[Brief description of the drawings]

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

[Explanation of symbols]

 B1 to Bn Battery 5 Detection circuit 6 Discharge circuit 7 Power supply circuit 9 Connection circuit

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02J 7/02 H02J 7/02 H

Claims (3)

[Claims] An overcharge prevention circuit for preventing overcharge of a plurality of batteries connected in series, comprising: a detection circuit for sequentially detecting a state of charge of each of the batteries;
At least one overcharge prevention discharge circuit connected to the battery, and a connection circuit for selectively connecting the discharge circuit to a battery in a highest charge state based on a detection result of the detection circuit. Characteristic overcharge prevention circuit. 2. An over-discharge prevention circuit for preventing over-discharge of a plurality of batteries connected in series, comprising: a detection circuit for sequentially detecting a discharge state of each of the batteries;
At least one over-discharge prevention power supply circuit connected to the battery, and a connection circuit for selectively connecting the power supply circuit to a battery in a deepest discharge state based on a detection result of the detection circuit. Over discharge prevention circuit. 3. A charge / discharge control circuit for preventing overcharge and overdischarge of a plurality of batteries connected in series, comprising: a detection circuit for sequentially detecting a charge state and a discharge state of each of the batteries; At least one overcharge prevention discharge circuit connected to one of the batteries, at least one overdischarge prevention power supply circuit connected to one of the batteries, and the detection circuit when the battery is charged Selectively connecting the discharging circuit to the battery in the highest charge state based on the detection result of the power supply circuit, and connecting the power supply circuit to the battery in the deepest discharge state based on the detection result of the detection circuit when the battery is discharged. And a connection circuit for selectively connecting the control circuit.