Overcurrent protection in a battery charger

Patent metadata

Field	Value
Publication number	US-2016204631-A1
Application number	US-201514981776-A
Country	US
Kind code	A1
Filing date	Dec 28, 2015
Priority date	Jan 13, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

Systems and methods for overcurrent protection in a battery charger are provided. For example, a method for overcurrent protection may include 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; applying a first ramp voltage to the sensed voltage drop generating a modified sensed voltage drop; comparing the modified sensed voltage drop against at least one reference voltage; and when the modified sensed voltage drop exceeds the at least one reference voltage, changing operation of the switching regulator 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:
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; applying a first ramp voltage to the sensed voltage drop generating a modified sensed voltage drop; comparing the modified sensed voltage drop against at least one reference voltage; and when the modified sensed voltage drop exceeds the at least one reference voltage, changing operation of the switching regulator to protect the battery charger from an overcurrent state.

2 . The method of claim 1 , wherein the method further comprises adding a second ramp voltage to the at least one reference voltage, whereby the second ramp voltage may or may not be different from the first ramp voltage.

3 . The method of claim 1 , wherein the method further comprises:
turning on an adapter switch coupled between an output of an adapter and an input of the battery charger; and when the modified sensed voltage exceeds the reference voltage, changing operation of the adapter switch to protect the battery charger from an overcurrent state.

4 . The method of claim 1 , further comprising controlling the switching regulator to provide a portion of the electrical power to the system load port from the battery.

5 . The method of claim 1 , wherein the method further comprises at least one of:
turning off a switch in the switching regulator such that a portion of the electrical current is not provided to the battery port; and periodically turning on the switch in the switching regulator to check for the overcurrent.

6 . The method of claim 1 , wherein comparing the voltage drop against the overcurrent reference voltage further comprises amplifying the voltage drop across a sense resistor.

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

8 . The method of claim 7 , 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.

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

10 . The method of claim 9 , wherein the modified sensed voltage exceeds the discharge overcurrent reference voltage when a duty cycle of the voltage drop exceeds a threshold value.

11 . The method of claim 9 , wherein the method further comprises changing operation of the switching regulator to protect the battery charger from an overcurrent state sensed by comparing the modified sensed voltage drop against the discharge overcurrent reference voltage by turning off a switch in the switching regulator to prevent current from passing from the battery to the switching regulator.

12 . A circuit for overcurrent protection, the circuit comprising:
at least one switching regulator input node coupled to receive a switching regulator voltage proportional to ae current provided by a switching regulator, 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 proportional to the current provided by the switching regulator through a sense resistor; at least one amplifier configured to provide an output signal proportional to the difference between the switching regulator voltage and the sense resistor voltage; a ramp voltage generator configured to generate a ramp voltage; at least one summer configured to add the ramp voltage to the output signal generating a modified output signal; and at least one threshold comparator configured to provide a comparison signal based on the comparison of the modified output signal against an overcurrent reference voltage, wherein the comparison signal is used to control the adapter switch.

13 . The circuit of claim 12 , wherein the at least one summer is further configured to add a second ramp voltage to the overcurrent reference voltage whereby the second ramp voltage may or may not be different from the ramp voltage.

14 . The circuit of claim 12 , 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 with the added ramp voltage against a charge overcurrent reference voltage.

15 . The circuit of claim 14 , wherein an overcurrent state exists when the charge output signal with the added ramp voltage exceeds the charge overcurrent reference.

16 . The circuit of claim 15 , 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.

17 . The circuit of claim 16 , wherein the adapter switch logic gradually increases current allowed through the adapter switch when the adapter switch logic turns on the adapter switch.

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

19 . The circuit of claim 18 , wherein a counter increments up to the programmed number of comparisons, wherein the counter is periodically cleared.

20 . The circuit of claim 12 , 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 with

Assignees

• Intersil Americas LLC

Inventors

• Houston Michael Jason
• Kleine John Stuart
• Zhao Lei
• Wei Jia

Classifications

• H02J7/90

  Regulation of charging or discharging current or voltage · CPC title

• H02J7/62 Primary

  against overcurrent · CPC title

• H02H3/202

  for DC systems · CPC title

• H02J7/685 Primary

  using connection detecting circuits (H02J7/68 takes precedence) · CPC title

• H02J7/0029 Primary

  Electricity · mapped topic