CHARGE/DISCHARGE CONTROL DEVICE AND BATTERY APPARATUS

A charge/discharge control device and a battery apparatus which are compatible with a quick-chargeable charging device which changes a charging current stepwise, the charge/discharge control device and a battery apparatus include an alarm output circuit connected to a control circuit, and a timer circuit which counts a preset period according to an output of an alarm signal from the alarm output circuit and supplies a signal which inhibits the charging to the control circuit after counting the preset period.

RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2019-227616, filed Dec. 17, 2019, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a charge/discharge control device and a battery apparatus.

2. Description of the Related Art

FIG. 3illustrates a block diagram of a conventional battery apparatus. The conventional battery apparatus20includes a battery1, a discharge control FET3, a charge control FET4, a charge/discharge control device21, external terminals EB+ and EB−, and an external terminal ALM. The charge/discharge control device21includes a voltage detection circuit210, a control circuit211, power supply terminals T1and T2, FET control terminals T3and T4, and an alarm output terminal T5.

The battery apparatus20does not supply an alarm signal while the voltage of the battery1is normal and lower than the overcharge voltage. Connection of a charging device5to the external terminals EB+ and EB− of the battery apparatus20starts charging at the maximum current in the absence of the alarm signal input to the charging device. The voltage of the battery1above the overcharge voltage causes the battery apparatus20to supply the alarm signal from the external terminal ALM. By the input of the alarm signal, the charging device5gradually reduces the charging current and continues charging.

The battery apparatus20constituted as described above is capable of quick and safe charging of the battery up to a voltage close to the full capacity with a simple circuit configuration (refer to, for example, Japanese Patent Application Laid-Open No. 2010-141987).

In the conventional battery apparatus, however, at an occurrence of anomalous situation in the charging device5which has started charging at the maximum current, a condition comes up in which the charging device5continues charging at the maximum current in spite of high voltage of the battery1even though the battery apparatus20supplies the alarm signal. A dangerous state may occur in which the charging at high current is performed in the vicinity of the maximum voltage of the battery voltage.

SUMMARY OF THE INVENTION

The present invention provides a charge/discharge control device and a battery apparatus which, even if an anomalous situation occurs in the charging device5having started charging at the maximum current, securely prevents the battery1from reaching above the overcharge voltage and provides high safety.

According to one aspect of the present invention, a charge/discharge control device includes: a first power supply terminal to which one end of a battery is connected, and a second power supply terminal to which the other end of the battery and a source of a discharge control FET are connected; a discharge control terminal to which a gate of the discharge control FET is connected, and a charge control terminal to which a gate of a charge control FET is connected; a voltage detection circuit having a first input terminal connected to the first power supply terminal, and a second input terminal connected to the second power supply terminal; a control circuit having a first input terminal connected to an output terminal of the voltage detection circuit, a discharge FET control terminal connected to the discharge control terminal, and a charge FET control terminal connected to the charge control terminal; an alarm output circuit having an input terminal connected to an output terminal of the control circuit; an alarm output terminal to which a first output terminal of the alarm output circuit is connected; and a timer circuit having an input terminal connected to a second output terminal of the alarm output circuit, and an output terminal connected to a second input terminal of the control circuit, in which the alarm output circuit makes an output of an alarm signal from the alarm output terminal according to a detection of a voltage between the first input terminal and the second input terminal above an alarm signal output voltage by the voltage detection circuit, and in which the timer circuit counts a preset period according to the output of the alarm signal and sends an anomaly detection signal from the output terminal to the control circuit to stop charging after counting the preset period.

According to the present invention, there can be provided a charge/discharge control device and a battery apparatus which securely prevent high current charging in the vicinity of the maximum voltage of a battery and provide high safety even if an anomalous operation of a charging device takes place since a timer circuit which monitors a time for supplying an alarm signal from an alarm output circuit is provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a block diagram illustrating a battery apparatus10according to the embodiment of the present invention. The battery apparatus10includes a battery1, a discharge control FET3, a charge control FET4, a charge/discharge control device11, external terminals EB+ and EB−, and an external terminal ALM.

The battery1has a positive terminal connected to the external terminal EB+. The charge/discharge control device11has a power supply terminal T1connected to the positive terminal of the battery1, a power supply terminal T2connected to a negative terminal of the battery1, an FET control terminal T3connected to a gate terminal of the discharge control FET3, an FET control terminal T4connected to a gate terminal of the charge control FET4, and an alarm output terminal T5connected to the external terminal ALM. The discharge control FET3has a source terminal connected to the negative terminal of the battery1and a drain terminal connected to a drain terminal of the charge control PET4. A source terminal of the charge control PET4is connected to the external terminal EB−.

The charge/discharge control device11includes a voltage detection circuit110, a control circuit111, an alarm output circuit112, a timer circuit113, power supply terminals T1and T2, FET control terminals T3and T4, and an alarm output terminal T5. The voltage detection circuit110has a first input terminal connected to the power supply terminal T1, a second input terminal connected to the power supply terminal T2, and an output terminal connected to a first input terminal of the control circuit111. The control circuit111has an output terminal connected to an input terminal of the alarm output circuit112, a second input terminal connected to an output terminal of the timer circuit113, a discharge control terminal connected to the FET control terminal T3, and a charge control terminal connected to the FET control terminal T4. The alarm output circuit112has a first output terminal connected to the alarm output terminal T5, and a second output terminal connected to an input terminal of the timer circuit113. The output terminal of the timer circuit113is connected to the second input terminal of the control circuit111.

The operation of the battery apparatus10constituted as described above will next be described. Here the voltages detected by the control circuit111include an overcharge voltage, an alarm signal output voltage, and an overdischarge voltage among which the magnitudes are assumed to be overcharge voltage>alarm signal output voltage>overdischarge voltage.

The voltage detection circuit110monitors the voltage of the battery1supplied from the power supply terminals T1and T2and sends a signal corresponding to the voltage to the control circuit111. The control circuit111sends signals from the FET control terminals T3and T4according to the signal provided from the voltage detection circuit110to turn ON and OFF the discharge control FET3and the charge control FET4.

Connection of a charging device5between the external terminals EB+ and EB− of the battery apparatus10starts the charging of the battery1by the charging device5. At this time, while the voltage of the battery1is above the overdischarge voltage and lower than the alarm signal output voltage, the control circuit111sends a signal which inhibits the output of an alarm signal from the output terminal to the input terminal of the alarm output circuit112. In an initial state in which no alarm signal is supplied from the battery apparatus10, the charging device5starts charging of the battery1at the maximum charging current. That is, quick charging is made to the battery1.

At the detection of the voltage of the battery1being higher than or equal to the alarm signal output voltage, the voltage detection circuit110sends a detection signal from the output terminal to the first input terminal of the control circuit111. By the input of the detection signal from the voltage detection circuit110, the control circuit111sends a signal which permits the output of the alarm signal from the output terminal to the input terminal of the alarm output circuit112. The alarm output circuit112sends the alarm signal from the output terminal to the charging device5through the external terminal ALM. By the input of the alarm signal from the battery apparatus10during charging, the charging device5reduces the charging current one step. Since the reduction of the charging current causes lowering of the voltage of the battery1to a voltage under the alarm signal output voltage, the voltage detection circuit110stops the supply of the detection signal. Then, the alarm output circuit112stops the alarm signal to the charging device5. The battery apparatus10repeats the charging, the supply of the alarm signal, the reduction of the charging current, and the stop of the alarm signal and thereby carries out quick and safe charging of the battery1.

Here, the timer circuit113counts a preset period while the input terminal thereof is supplied with a signal indicating the output of the alarm signal from the alarm output circuit112and stops counting by the stop of the alarm signal, initializing the counting state. Then, the timer circuit113sends an anomaly detection signal from the output terminal to the second input terminal of the control circuit111after counting the preset period. The preset period counted by the timer circuit113is set longer than the time required to supply the alarm signal from the alarm output circuit112, reduce the charging current one step by the charging device5, and detect the decrease in the voltage of the battery1by the voltage detection circuit110.

By the input of the anomaly detection signal from the timer circuit113to the second input terminal of the control circuit111, regardless of an overcharge state of the output signal from the voltage detection circuit110, the control circuit111supplies a signal from the FET control terminal T4to turn OFF the charge control FET4and stops charging. Even if an anomaly occurs, for example, in the operation of the charging device5having started quick charging of the battery1with the maximum charging current, the charge control FET4can be turned OFF accordingly to stop the charging regardless of the overcharge state of the output signal of the voltage detection circuit110.

As described above, according to the embodiment, there can be provided a highly safe charge/discharge control device and a battery apparatus which are compatible with a quick-chargeable charging device allowing stepwise change of the charging current.

FIG. 2is a block diagram illustrating another example of the battery apparatus according to the embodiment. Even if a high-side charge/discharge control is carried out as in the battery apparatus10ofFIG. 2, the present invention can be applied in the same manner.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Various changes can be made thereto within the scope not departing from the spirit of the present invention.

For example, in the embodiments described above, the alarm signal itself may be used as the signal indicating the output of the alarm signal supplied from the alarm output circuit112to the timer circuit113. Further, for example, in the embodiment, although the alarm signal output voltage is not provided with a release voltage, hysteresis may be provided in the alarm signal output voltage, i.e., an alarm signal release voltage may be provided.