METHOD AND APPARATUS FOR CHARGING BATTERIES HAVING DIFFERENT VOLTAGE RANGES WITH A SINGLE CONVERSION CHARGER

• US 20140159641A1
• Filed: 12/07/2012
• Published: 06/12/2014
• Est. Priority Date: 12/07/2012
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola Solutions, Inc.
• Inventors: GEREN, MICHAEL D.
• Granted Patent: US 9,209,676 B2
• Time in Patent Office: Days
• US Class Current: 320/106
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/335 using semiconductor devices only

Abstract

Embodiments for a battery charger include a single conversion switched mode power supply having a bias winding on the primary side of the power transformer. The bias winding produces an output that is proportional to the voltage produced on the secondary winding, and is sensed by a programmable voltage sensing circuit. The programmable voltage sensing circuit is programmed by a voltage select signal from the secondary side of the charger to produce an sense signal that is proportional to the output of the bias winding by a selected factor corresponding to a battery type of a battery being charged.

Claims

1. A battery charger, comprising:

a single conversion switched mode power supply including a power transformer, the transformer defines a primary side and a secondary side of the battery charger and converts an input alternating current (AC) power on the primary side to a direct current (DC) charging current on the secondary side, the DC charging current is provided to charging interface configured to connect to a rechargeable battery;

a bias winding on the primary side of the power transformer that provides an output corresponding to output of the secondary side of the power transformer;

a programmable voltage sensing circuit that senses the output of the bias winding and produces a voltage sensing output that is proportional to the output of the bias winding by a selected factor;

a comparison circuit that compares the voltage sensing output to a reference and generates a fault signal when the voltage sensing output exceeds the reference; and

the single conversion switched mode power supply include a switched mode control circuit that controls the single conversion switched mode power supply to produce the DC_charging current, and which shuts off the switched mode power supply responsive to the fault signal.

2. The battery charger of claim 1, wherein the programmable voltage sensing circuit is operably coupled to a controller on the secondary side of the battery charger via an isolated communication link.

3. The battery charger of claim 2, wherein the isolated communication link is an opto-isolater.

4. The battery charger of claim 1, wherein the programmable voltage sensor comprises a circuit for setting a maximum over-voltage level.

5. The battery charger of claim 4, wherein the programmable voltage sensor comprises a programmable resistor divider network.

6. The battery charger of claim 1, wherein the programmable voltage sensing circuit is set such that the fault signal occurs when an over-voltage condition occurs on the secondary side of the transformer.

7. The battery charger of claim 6, wherein the over-voltage condition is based on a battery type of a battery being charged, and wherein the programmable voltage sensing circuit is programmed based on the battery type.

8. The battery charger of claim 1, wherein the single conversion switched mode power supply is a flyback power supply.

9. The battery charger of claim 1, further comprising a programmable current sensing circuit on the primary side that produces a current sensing signal that is selectively proportional to the charging current;

and

the current sensing signal is provided to the comparison circuit and the comparison circuit produces the fault signal if the current sensing signal indicates the DC charging current has exceeded an over-current limit.

10. The battery charger of claim 9, wherein the programmable current sensing circuit is programmed by a controller on the secondary side via an isolated communication link.

11. The battery charger of claim 1, further comprising a programmable current sensing circuit on the secondary side that produces a current sensing signal that is selectively proportional to the charging current;

and

the current sensing signal is provided to the switched mode control circuit on the primary side.

12. The battery charger of claim 11, wherein the programmable current sensing circuit on the primary side is programmed by a charge controller on the secondary side via an isolated communication link.

13. A method of operating a battery charger, comprising:

detecting connection of a battery to the battery charger;

determining a battery type of the battery;

communicating a voltage select signal corresponding to an over-voltage limit for the battery type from a secondary side of the battery charger to a programmable voltage sensor on a primary side of the battery charger, wherein the programmable voltage sense circuit senses an output of a bias winding on the primary side of a power transformer and provides a sense signal that is proportional to the output of the bias winding by a selected factor, wherein the voltage select signal sets the programmable voltage sense circuit to the selected factor;

comparing the sense signal with a reference;

producing a fault signal in response to the sense signal exceeding the reference; and

shutting down a power supply of the battery charger in response to the fault signal.

14. The method of claim 13, wherein communicating the voltage select signal comprises communicating an on/off signal to a switch in the programmable voltage sensor.

15. The method of claim 13, wherein communicating the voltage select signal comprises communicating a digital word to the programmable voltage sensor comprising a plurality of bits, each bit corresponding to one of a plurality of switches in the programmable voltage sensor that each control connection of a resistance in a voltage divider network.

16. The method of claim 13, further comprising:

communicating a current select signal from the secondary side of the battery charger to the a programmable current sense circuit on the primary side of the battery charger, the current select signal corresponding to a over-current limit of the battery type, wherein the programmable current sense circuit provides a current sense signal that is proportional to a DC charging current provided to the battery by a selected proportion, and wherein the current select signal configures the programmable current sense circuit according to the selected proportion;

comparing the current sense signal with a reference; and

shutting down the power supply when the current sense signal exceeds the reference.

17. The method of claim 13, wherein communicating the voltage select signal comprises communicating the voltage select signal over an optical link between the primary and secondary sides of the battery charger.

18. The method of claim 13, wherein shutting down the power supply comprises shutting down a single conversion power supply.

19. The method of claim 13, wherein shutting down the power supply comprises shutting down the power supply until the battery is removed from the charger.

20. A single conversion switched mode power supply, comprising:

a power transformer that defines a primary side and a secondary side of the single conversion switched mode power supply;

a bias winding on the primary side of the power transformer that provides an output corresponding to an output of the secondary side of the power transformer;

a programmable voltage sensing circuit that senses the output of the bias winding and produces a voltage sensing output that is proportional to the output of the bias winding by a selected factor, wherein the programmable voltage sensing circuit is programmed to the selected factor by a voltage select signal provided to the programmable voltage sensing circuit from the secondary side of the single conversion switched more power supply;

a comparison circuit that compares the sensing output to a reference and generates a fault signal when the voltage sensing output exceeds the reference; and

a switched mode control circuit that controls the single conversion switched mode power supply, and which shuts off the switched mode power supply responsive to the fault signal.

21. The single conversion switched mode power supply of claim 20, wherein the single conversion switched mode power supply is a flyback switched mode power supply.

22. The single conversion switched mode power supply of claim 20, wherein the single conversion switched mode power supply provides a charging current and voltage to a charging interface of a battery charger using the single conversion switched mode power supply, and wherein the voltage select signal corresponds to one of a plurality of battery types the battery charger can charge.