PROTECTION SWITCH CIRCUIT, CHARGING CIRCUIT, AND ELECTRONIC DEVICE

• US 20160072322A1
• Filed: 09/01/2015
• Published: 03/10/2016
• Est. Priority Date: 09/04/2014
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: YOSHIMATSU, Yusaku
• Granted Patent: US 9,941,716 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02H 3/202 for dc systems
• CPC Class Codes: H02H 3/207 also responsive to under-voltage window comparators for indication G01R19/165
• CPC Class Codes: H02H 3/243 for DC systems
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A protection switch circuit includes: an input terminal configured to receive a DC input voltage; an output terminal; a switch provided between the input terminal and the output terminal; a determination circuit configured to compare the input voltage with N threshold voltages (N is a natural number); and a gate controller configured to control the switch based on a comparison result of the determination circuit, wherein the determination circuit includes: an OTPROM (One Time Programmable Read Only Memory) to which N pieces of setting data indicative of each of the N threshold voltages are written under software control, and a comparison circuit configured to compare the input voltage with each of the N threshold voltages according to the N pieces of the setting data written to the OTPROM.

Claims

1. A protection switch circuit comprising:

an input terminal configured to receive a DC input voltage;

an output terminal;

a switch provided between the input terminal and the output terminal;

a determination circuit configured to compare the input voltage with N threshold voltages (N is a natural number); and

a gate controller configured to control the switch based on a comparison result of the determination circuit,

wherein the determination circuit includes;

an OTPROM (One Time Programmable Read Only Memory) to which N pieces of setting data indicative of each of the N threshold voltages are written under software control, and

a comparison circuit configured to compare the input voltage with each of the N threshold voltages according to the N pieces of the setting data written to the OTPROM.

2. The protection switch circuit of claim 1, wherein the setting data indicative of a first threshold voltage and a second threshold voltage corresponding respectively to an upper limit and a lower limit of a normal voltage range where the switch is turned on are written to the OTPROM, and

wherein the comparison circuit is configured to compare the input voltage with each of the first threshold voltage and the second threshold voltage.

3. The protection switch circuit of claim 1, wherein the comparison circuit includes:

N voltage divider circuits corresponding to the N pieces of the setting data, each of the voltage divider circuits dividing the input voltage by a voltage dividing ratio according to the corresponding setting data; and

N comparators corresponding to the N pieces of the setting data, each of the comparators comparing an output voltage of the corresponding voltage divider circuit with a predetermined reference voltage.

4. The protection switch circuit of claim 3, wherein each of the voltage divider circuits includes:

a plurality of resistors connected in series between the input terminal and a ground line; and

a plurality of bypass switches provided in parallel with the plurality of resistors,

wherein the plurality of bypass switches are set to be turned on or turned off according to the corresponding setting data.

5. The protection switch circuit of claim 1, wherein the protection switch circuit is integrated on a single semiconductor substrate.

6. An electronic device comprising the protection switch circuit of claim 1.

7. A charging circuit that charges a secondary battery by an external DC power supply and supplies electric power to a load, the charging circuit comprising:

a DC input terminal configured to receive a DC voltage from the DC power supply;

a battery terminal which the secondary battery is removably connected to;

a system terminal to which the load is connected;

a charging transistor provided between the system terminal and the battery terminal;

a charging controller configured to control a gate voltage of the charging transistor;

a switch provided between the DC input terminal and the system terminal;

a determination circuit configured to compare an input voltage of the DC input terminal with N threshold voltages (N is a natural number); and

a gate controller configured to control the switch based on a comparison result of the determination circuit, wherein the determination circuit includes;

an OTPROM (One Time Programmable Read Only Memory) to which N pieces of setting data indicative of each of the N threshold voltages are written under software control, and

a comparison circuit configured to compare the input voltage with each of the N threshold voltages corresponding to the N pieces of the setting data written to the OTPROM.

8. The charging circuit of claim 7, wherein the setting data indicative of a first threshold voltage and a second threshold voltage corresponding respectively to an upper limit and a lower limit of a normal voltage range where the switch is turned on are written to the OTPROM, and

wherein the comparison circuit is configured to compare the input voltage with each of the first threshold voltage and the second threshold voltage.

9. The charging circuit of claim 7, wherein the comparison circuit includes:

N voltage divider circuits corresponding to the N pieces of the setting data, each of the voltage divider circuits dividing the input voltage by a voltage dividing ratio according to the corresponding setting data; and

N comparators corresponding to the N pieces of the setting data, each of the comparators comparing an output voltage of the corresponding voltage divider circuit with a predetermined reference voltage.

10. The charging circuit of claim 9, wherein each of the voltage divider circuits includes:

a plurality of resistors connected in series between the input terminal and a ground line; and

a plurality of bypass switches provided in parallel with the plurality of resistors,

wherein the plurality of bypass switches are set to be turned on or turned off according to the corresponding setting data.

11. The charging circuit of claim 7, wherein the switch includes a transistor, and

wherein the gate controller is configured to adjust gate voltages of the transistor such that a voltage of the system terminal approaches a predetermined target voltage.

12. The charging circuit of claim 11, wherein the setting data indicative of the target voltage is written to the OTPROM under software control.

13. The charging circuit of claim 11, wherein the gate controller is configured to adjust gate voltages of the transistor such that an electric current flowing through the transistor does not exceed an overcurrent threshold.

14. The charging circuit of claim 13, wherein the setting data indicative of the overcurrent threshold is written to the OTPROM under software control.

15. The charging circuit of claim 7, wherein the OTPROM includes a power-on reset circuit to reset memory cells of the OTPROM if the input voltage is lower than a threshold voltage for power-on reset.

16. The charging circuit of claim 7, wherein the charging circuit is integrated on a single semiconductor substrate.

17. An electronic device comprising:

a secondary battery; and

a charging circuit of claim 7 that charges the secondary battery.