Overcurrent protection in a battery charger

Patent metadata

Field	Value
Publication number	US-9853467-B2
Application number	US-201514747912-A
Country	US
Kind code	B2
Filing date	Jun 23, 2015
Priority date	Jan 13, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

Systems and methods are provided for overcurrent protection in a battery charger. In certain embodiments, a method includes turning on an adapter switch to receive electrical power from an adapter connected to the battery charger; controlling a switching regulator to direct electrical current between the switching regulator and a battery port. Further, the method includes sensing a voltage drop that is related to the electrical current passing between the switching regulator and the battery port; comparing the sensed voltage drop against at least one reference voltage; and, when the sensed voltage exceeds the reference voltage, changing operation of the adapter switch to protect the battery charger from an overcurrent state.

First claim

What is claimed is:

1. A method for overcurrent protection in a battery charger, the method comprising:
turning on an adapter switch to receive electrical power from an adapter connected to the battery charger;
controlling a switching regulator to direct electrical current between the switching regulator and a battery port;
sensing a voltage drop that is related to the electrical current passing between the switching regulator and the battery port;
comparing the sensed voltage drop against at least one reference voltage; and
when the sensed voltage exceeds the reference voltage, changing operation of the adapter switch to protect the battery charger from an overcurrent state.

2. The method of claim 1 , wherein the method further comprises at least one of:
controlling the switching regulator such that the electrical current is received from the battery port; and
checking for an overcurrent based on the sensed voltage drop.

3. The method of claim 1 , wherein comparing the sensed voltage drop against at least one reference voltage further comprises amplifying the voltage drop across a sense resistor.

4. The method of claim 1 , wherein comparing the sensed voltage drop against the at least one reference voltage comprises at least one of:
determining whether the electrical current is an overcurrent for a programmed duration of time; and
determining whether the electrical current is an overcurrent for a programmed number of comparisons.

5. The method of claim 4 , wherein determining whether the electrical current is an overcurrent for a programmed number of comparisons comprises:
incrementing a counter when a measurement indicates that a charge comparison output exceeds the reference voltage until the counter equals the programmed number of comparisons;
periodically clearing the counter.

6. The method of claim 1 , wherein the reference voltage is at least one of:
a charge overcurrent reference voltage, wherein the sensed voltage drop is compared against the charge overcurrent reference voltage when current is provided from the switching regulator to the battery port; and
a discharge overcurrent reference voltage, wherein the sensed voltage drop is compared against the discharge overcurrent reference voltage when current is received from the battery port to the switching regulator.

7. The method of claim 6 , wherein the sensed voltage drop exceeds the discharge overcurrent reference voltage when a duty cycle of the voltage drop exceeds a threshold value.

8. The method of claim 6 , wherein the method further comprises changing operation of the switching regulator to protect the battery from an overcurrent state sensed by comparing the sensed voltage drop against the discharge overcurrent reference voltage by turning off at least one switch in the switching regulator to prevent current from passing from the battery to the switching regulator.

9. The method of claim 1 , further comprising turning on the adapter switch to provide a portion of the electrical power to the system load port with the battery power.

10. A circuit for overcurrent protection, the circuit comprising:
at least one switching regulator input node coupled to receive a switching regulator voltage, wherein the switching regulator is capable of directing a portion of current provided through an adapter switch to at least one of a system load port and a battery port;
at least one sense resistor input node coupled to receive a sense resistor voltage;
at least one amplifier configured to provide an output signal proportional to the difference between the switching regulator voltage and the sense resistor voltage; and
at least one threshold comparator configured to provide a comparison signal based on the comparison of the output signal against an overcurrent reference voltage, wherein the comparison signal is used to control the adapter switch.

11. The circuit of claim 10 , wherein the at least one amplifier comprises a charge amplifier configured to be capable of providing a charge output signal proportional to the difference between the switching regulator voltage and the sense resistor voltage when current is provided to the battery port;
wherein the at least one threshold comparator comprises a charge threshold comparator, the charge threshold comparator providing a charge comparison signal when current is provided to the battery port based on the comparison of the charge output signal against a charge overcurrent reference voltage.

12. The circuit of claim 11 , wherein an overcurrent state exists when the charge output signal exceeds the charge overcurrent reference.

13. The circuit of claim 12 , further comprising at least one of:
an adapter switch logic that controls the adapter switch, the adapter switch logic turning off the adapter switch when a fault condition exists; and
a pulse width modulation logic that controls the switching regulator, the pulse width modulation disabling electrical paths through the sense resistor when a fault condition exists.

14. The circuit of claim 13 , wherein the adapter switch logic gradually increases current allowed through the adapter switch when the adapter switch logic turns on the adapter switch.

15. The circuit of claim 12 , wherein a fault condition exists when the charge output signal exceeds the charge overcurrent reference voltage for at least one of:
a programmed duration of time; and
a programmed number of comparisons.

16. The circuit of claim 15 , wherein a counter increments up to the programmed number of comparisons, wherein the counter is periodically cleared.

17. The circuit of claim 10 , wherein the at least one amplifier comprises a discharge amplifier configured to provide a discharge output signal proportional to the difference between the sense resistor voltage and the switching regulator voltage when current is received from the battery port;
wherein the at least one threshold comparator comprises a discharge threshold comparator, the discharge threshold comparator providing a discharge comparison signal when current is received from the battery port based on the comparison of the discharge output signal against a discharge overcurrent reference voltage.

18. The circuit of claim 17 , wherein a pulse width modulation logic directs the switching regulator to disable electrical paths through the sense resistor when at least one of the discharge output signal exceeds the discharge overcurrent reference voltage; and when a comparator-duty cycle exceeds a specified value.

19. The circuit of claim 10 , wherein a first filter couples the switching regulator voltage to the at least one switching regulator input node and a second filter couples the sense resistor voltage to the at least one sense resistor input node, wherein the first filter and the second filter have different time constants.

20. The circuit of claim 10 , wherein the switching regulator comprises:
an upper switch coupled to the adapter switch;
a lower switch coupled to the upper switch; and
an inductor coupled to the upper switch, the lower switch, and the sense resistor.

21. A system for a battery powered system load, the system comprising:
an adapter, the adapter connectable to a power source, wherein the adapter alters current provided by the power source;
a battery configured to store a portion of energy provided by the power source and to provide stored energy;
a system load configured to use a portion of the current provided by the power source and a portion of stored energy p

Assignees

• Intersil Americas LLC

Inventors

• Kleine John Stuart
• Zhao Lei
• Wei Jia

Classifications

• H02J7/62

  against overcurrent · CPC title

• H02J7/865

  Battery or charger load switching, e.g. concurrent charging and load supply (H02J7/50 takes precedence) · CPC title

• H02J7/663 Primary

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

• H02J7/34

  Parallel operation in networks using both storage and other DC sources, e.g. providing buffering (H02J7/14 takes precedence) · CPC title

• H02H9/025

  Current limitation using field effect transistors · CPC title