Secondary battery protection circuit, secondary battery protection apparatus, battery pack and temperature detection circuit

Patent metadata

Field	Value
Publication number	US-11575161-B2
Application number	US-202017069121-A
Country	US
Kind code	B2
Filing date	Oct 13, 2020
Priority date	Oct 18, 2019
Publication date	Feb 7, 2023
Grant date	Feb 7, 2023

Abstract

A secondary battery protection circuit for controlling charge and discharge using a switching circuit to protect a secondary battery from temperature is provided. The switching circuit is configured to be provided in a charge-and-discharge path between the secondary battery and an external device. The secondary battery protection circuit includes a detection terminal configured to be electrically connected, via a resistor, to between the switching circuit and the external device. The secondary battery protection circuit includes a first terminal configured to be electrically connected to a temperature detection terminal of the external device. The secondary battery protection circuit includes a second terminal to which a temperature sensitive element is configured to be electrically connected, the temperature sensitive element having a characteristic value varying in accordance with a change in temperature of the secondary battery.

First claim

What is claimed is:

1. A secondary battery protection circuit for controlling charge and discharge using a switching circuit to protect a secondary battery from temperature, the switching circuit configured to be provided in a charge-and-discharge path between the secondary battery and an external device, the secondary battery protection circuit comprising:
a detection terminal configured to be electrically connected, via a resistor, to between the switching circuit and the external device;
a first terminal configured to be electrically connected to a temperature detection terminal of the external device;
a second terminal to which a temperature sensitive element is configured to be electrically connected, the temperature sensitive element having a characteristic value varying in accordance with a change in temperature of the secondary battery;
a conversion circuit configured to convert the characteristic value into a voltage corresponding to the change in the temperature of the secondary battery, the conversion circuit being configured to output the voltage;
a comparison circuit configured to compare the output voltage of the conversion circuit with a threshold voltage and output a compared result; and
a control circuit configured to control the switching circuit based on the output of the comparison circuit,
wherein the conversion circuit includes a first switch provided between the first terminal and the second terminal, and includes a second switch provided between the comparison circuit and the second terminal, and
wherein the first switch and the second switch are configured to be controlled by the control circuit.

2. The secondary battery protection circuit according to claim 1 , wherein the temperature sensitive element is an NTC thermistor.

3. The secondary battery protection circuit according to claim 1 , wherein the control circuit is configured to:
turn the first switch on and turn the second switch off, upon determining that a voltage associated with the first terminal is a first voltage, and
turn the first switch off and turn the second switch on, upon determining that the voltage associated with the first terminal is a second voltage lower than the first voltage.

4. The secondary battery protection circuit according to claim 1 , further comprising a signal generating unit configured to generate a periodic signal,
wherein the control circuit is configured to alternately turn on the first switch and the second switch in accordance with the periodic signal.

5. The secondary battery protection circuit according to claim 4 , wherein a period during which the first switch is on is longer than a length of time to interrupt a charge current through the secondary battery, after the external device has detected an increase in temperature of the secondary battery, the switching circuit, or the secondary battery protection circuit, and
wherein a period during which the second switch is on is longer than a length of time for the control circuit to cause the switching circuit to interrupt a discharge current in the secondary battery, after a change in the output of the comparison circuit is determined.

6. The secondary battery protection circuit according to claim 4 , wherein the control circuit is configured to use the signal generating unit to generate a detection delay time duration, with respect to whether overvoltage or overcurrent for the secondary battery is detected.

7. The secondary battery protection circuit according to claim 1 , further comprising a third switch provided between the comparison circuit and the detection terminal; and
a resistive element provided between the third switch and the detection terminal,
wherein the control circuit is configured to turn the second switch off and turn the third switch on, in response to turning the first switch on.

8. The secondary battery protection circuit according to claim 1 , further comprising a fourth switch provided between the first terminal and the detection terminal; and
a resistive element provided between the fourth switch and the detection terminal,
wherein the control circuit is configured to turn the first switch off and turn the fourth switch on, in response to turning the second switch on.

9. The secondary battery protection circuit according to claim 1 , further comprising a fifth switch inserted in a power supply line via which power is supplied to the comparison circuit by the secondary battery,
wherein in response to turning the first switch on and turning the second switch off, the control circuit is configured to shut off the fifth switch.

10. The secondary battery protection circuit according to claim 1 , further comprising an auxiliary terminal configured to be electrically connected to a current path in the charge-and-discharge path, the current path being between the switching circuit and the external device; and
a resistive element,
wherein in response to turning the second switch on, the control circuit is configured to cause the first terminal to be electrically connected to the current path via the resistive element and the auxiliary terminal, without using the detection terminal.

11. A secondary battery protection apparatus comprising:
a temperature sensitive element, the temperature sensitive element having a characteristic value varying in accordance with to a change in temperature of a secondary battery;
a switching circuit configured to be provided in a charge-and-discharge path between the secondary battery and an external device; and
a secondary battery protection circuit configured to control charge and discharge using the switching circuit to protect the secondary battery from temperature, the secondary battery protection circuit including:
a first terminal configured to be electrically connected to a temperature detection terminal of the external device;
a second terminal to which the temperature sensitive element is electrically connected;
a conversion circuit configured to convert the characteristic value for the temperature sensitive element into a voltage corresponding to the change in the temperature of the secondary battery, the conversion circuit being configured to output the voltage;
a comparison circuit configured to compare the output voltage of the conversion circuit with a threshold voltage and output a compared result; and
a control circuit configured to control the switching circuit based on the output of the comparison circuit,

wherein the conversion circuit includes a first switch provided between the first terminal and the second terminal, and includes a second switch provided between the comparison circuit and the second terminal, and
wherein the first switch and the second switch are configured to be controlled by the control circuit.

12. A battery pack comprising:
the secondary battery protection apparatus according to claim 11 ; and
the secondary battery.

13. A temperature detection circuit for a secondary battery, comprising:
a first terminal configured to be electrically connected to a temperature detection terminal of an external device;
a second terminal to which a temperature sensitive element is configured to be electrically connected, the temperature sensitive element having a characteristic value varying in accordance with a change in temperature of the secondary battery;
a conversion circuit configured to convert the characteristic value into a voltage corresponding to the change in the temperature of the secondary battery, the conversion circuit being configured to output the voltage; and
a comparison circuit configured to compare the output voltage of the conversion circuit with a th

Assignees

• Watanabe Yohei
• Takeda Takashi
• Takeshita Junji
• Suzuki Daisuke
• Mitsumi Electric Co Ltd

Inventors

• Watanabe Yohei
• Takeda Takashi
• Takeshita Junji
• Suzuki Daisuke

Classifications

• H02J7/977

  of the battery · CPC title

• H02J7/663 Primary

  using battery or load disconnect circuits (H02J9/002 takes precedence) · CPC title

• H02J7/62

  against overcurrent · CPC title

• H02J7/61

  against overcharge · CPC title

• H02J7/63

  against overdischarge · CPC title