BATTERY CHARGER USING PHASE SHIFT DOUBLE FORWARD CONVERTING CIRCUIT

• US 20100225280A1
• Filed: 03/06/2009
• Published: 09/09/2010
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: Illinois Tool Works Inc.
• Original Assignee: Illinois Tool Works Inc.
• Inventors: Vogel, Bernard J.
• Granted Patent: US 8,179,100 B2
• Time in Patent Office: Days
• US Class Current: 320/145
• CPC Class Codes: H02J 7/007184 in response to battery voltage gradient
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved
• CPC Class Codes: H02M 3/3353 having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
• CPC Class Codes: H02M 3/33561 having more than one ouput with independent control
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current

Abstract

A technique for dynamically adjusting an output voltage of forward converter circuits for a battery charging operation is provided. The technique allows for varying voltage at the charging battery by manipulating the duty cycles of two forward converter circuits. The present disclosure provides methods and systems for increasing synchronized duty cycles in a pair of forward converter circuits in response to a changing battery charge state that requires a higher voltage output then changing a phase shift between the duty cycles in response to further increases in output voltage demand. The present disclosure also provides methods and systems for setting a phase shift between duty cycles in a pair of forward converter circuits based on battery rating and then altering pulse width in response to changing battery charge state. The invention provides a controller designed to receive input signals and generate output pulse width modulation signals that control the duty cycle width and phase shift of the outputs of the forward converter circuits in response to these signals. Methods of accommodating for the time needed for the transformer core to reset via leading edge or lagging edge compensation are provided.

Claims

1. A method of dynamically adjusting an output voltage for battery charging operation, comprising:

setting a phase shift between duty cycles of a pair of forward converter circuits based on a detected battery voltage rating of a battery; and

adjusting the duty cycles of the pair of forward converter circuits to accommodate changes in a voltage requirement of the battery.

2. The method of claim 1, wherein the upper limit for each of the duty cycles is based on time required for a transformer core in each of the respective forward converter circuits to reset.

3. The method of claim 1, wherein setting the phase shift comprises delaying a leading edge of a pulse in a switching period to reduce the duty cycle of a one of the pair of forward converter circuits.

4. The method of claim 1, comprising preventing saturation of a transformer in one of the pair of forward converter circuits by monitoring voltage and/or current in the transformer and disabling initiation of a new pulse when the voltage and/or current indicates that the transformer has not been reset.

5. The method of claim 1, comprising flowing current through the pair of forward converter circuits in parallel or in series.

6. The method of claim 1, wherein adjusting the duty cycles of the pair of forward converter circuits comprises increasing they duty cycles to accommodate a higher voltage requirement of the battery.

7. The method of claim 1, wherein adjusting circuit components comprises switching one or more transistors in each of the forward converter circuits to pulse width modulate a voltage output of each forward converter circuit.

8. The method of claim 1, comprising ceasing to charge the battery based on reaching a target value of a charging algorithm.

9. A battery charging system, comprising:

a pair of forward converter circuits capable of coordinating to accommodate a dynamic voltage requirement of a battery; and

a controller, comprising;

a regulator capable of receiving at least one input related to a desired combined voltage output for the pair of forward converter circuits based on the dynamic voltage requirement of the battery, and capable of generating a control signal; and

a processor capable of receiving the control signal and driving switches in the pair of forward converter circuits to facilitate control of duty cycles of the pair of forward converter circuits based on the control signal to produce the desired combined voltage output.

10. The battery charging system of claim 9, wherein the processor is configured to drive the switches via control of gate drive circuitry.

11. The battery charging system of claim 9, wherein the processor is configured to output an additional control signal for an auxiliary device.

12. The battery charging system of claim 9, wherein regulator is capable of receiving a measured value for an actual output from an output sensor.

13. The battery charging system of claim 9, wherein the processor is capable of shifting the duty cycles of the pair of forward converter circuits based on the control signal to produce the desired combined voltage output.

14. The battery charging system of claim 9, wherein the processor is capable of adjusting a pulse width of the duty cycles of the pair of forward converter circuits based on the control signal to produce the desired combined voltage output.

15. The battery charging system of claim 9, wherein the pair of forward converter circuits are arranged in parallel or in series.

16. A method of accommodating a voltage requirement of a battery charging operation, comprising:

increasing synchronized duty cycles in a pair of forward converter circuits to accommodate an increase in a battery charge state of the battery; and

changing a phase shift between the duty cycles upon reaching an upper limit for each of the duty cycles to accommodate a further increase in the battery charge state.

17. The method of claim 16, wherein changing the phase shift comprises delaying a leading edge of a pulse in a switching period to reduce the duty cycle of a one of the pair of forward converter circuits.

18. The method of claim 16, wherein changing the phase shift comprises initiating an early lagging edge of a pulse in a switching period to reduce the duty cycle of a one of the pair of forward converter circuits.

19. The method of claim 16, wherein changing the phase shift comprises skipping a pulse in a switching period of a one of the pair of forward converter circuits.

20. The method of claim 16, wherein changing the phase shift comprises increasing the duty cycles to a maximum limit, shifting outputs of the pair of forward converter circuits fully out of phase, and reducing pulse widths in the switching period for each of the forward converter circuits.