Circuits and methods for driving light sources

• US 8,378,588 B2
• Filed: 02/16/2011
• Issued: 02/19/2013
• Est. Priority Date: 12/12/2008
• Status: Active Grant

• Current Assignee: Feit Electric Company Incorporated
• Original Assignee: O2 Micro International Limited (O2 Micro Incorporated)
• Inventors: Kuo, Ching Chuan, Lin, Yung Lin
• Primary Examiner(s): VU, JIMMY T
• Application Number:
  US13/028,626
• Publication Number:
  US 20120038292A1
• Time in Patent Office: 734 Days
• Field of Search: 315/185.R, 315/186, 315/193, 315/209.R, 315/210, 315/211, 315/219, 315/224, 315/225, 315/244, 315/245, 315/246, 315/283, 315/287, 315/291, 315/307, 315312-314, 315/362
• US Class Current: 315/291
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A driving circuit for driving a light source includes a converter and a dimming controller. The converter coupled to a power source is operable for receiving power from the power source and for providing regulated power to the light source according to control signals. The dimming controller coupled to the converter is operable for monitoring a power switch coupled between the power source and the converter, for receiving a color change signal indicating a first set of operations of the power switch and a dimming request signal indicating a second set of operations of the power switch, for controlling the control signals to change the color of the light source in response to the color change signal, and for controlling the control signals to adjust the brightness of the light source in response to the dimming request signal.

Claims

1. A driving circuit for driving a light source comprising a plurality of light-emitting diodes (LEDs), said driving circuit comprising:

a converter coupled to a power source and operable for receiving power from said power source and for providing regulated power to said light source according to a plurality of control signals; and

a dimming controller coupled to said converter and operable for monitoring a power switch coupled between said power source and said converter, for receiving a color change signal indicating a first set of operations of said power switch and a dimming request signal indicating a second set of operations of said power switch, for controlling said control signals to change the color of light emitted from said light source in response to said color change signal, and for controlling said control signals to adjust the brightness of said light in response to said dimming request signal, wherein said dimming controller comprises;

a trigger monitoring unit operable for receiving a detection signal indicating a conductance status of said power switch, and for identifying said first set of operations and said second set of operations based on said detection signal.

2. The driving circuit as claimed in claim 1, wherein said first set of operations comprises a first turn-off operation followed by a first turn-on operation, wherein said second set of operations comprises a second turn-off operation followed by a second turn-on operation, and wherein a time interval between said first turn-off operation and said first turn-on operation is different from a time interval between said second turn-off operation and said second turn-on operation.

3. The driving circuit as claimed in claim 1, wherein said dimming controller adjusts said brightness in response to said dimming request signal until a dimming termination signal indicating a third set of operations of said power switch is received.

4. The driving circuit as claimed in claim 3, wherein said second set of operations comprises a first turn-off operation followed by a first turn-on operation, wherein said third set of operations comprises a second turn-off operation followed by a second turn-on operation, and wherein a time interval between said first turn-on operation and said second turn-off operation is less than a time threshold.

5. The driving circuit as claimed in claim 1, wherein said light source comprises a first LED light-source operable for emitting light having a first color and a second LED light source operable for emitting light having a second color.

6. The driving circuit as claimed in claim 1, wherein said trigger monitoring unit identifies a plurality of operations of said power switch comprising a turn-on operation and a turn-off operation based on said detection signal, and identifies said first set of operations and said second set of operations based on time intervals between said plurality of operations.

7. The driving circuit as claimed in claim 1, wherein said dimming controller comprises:

a plurality of dimmers operable for adjusting counter values of a plurality of counters respectively according to said color change signal and said dimming request signal, wherein said dimming controller adjusts said control signals respectively according to said counter values.

8. The driving circuit as claimed in claim 7, wherein said dimming controller further comprises:

an under-voltage-lockout circuit coupled to said dimmers and operable for detecting a supply voltage, for setting said counter values to a first set of predetermined values when said supply voltage drops below a voltage threshold, and for setting said counter values to a second set of predetermined values when said supply voltage rises above said voltage threshold.

9. The driving circuit as claimed in claim 7, wherein said dimmers exchange said counter values of said counters if said color change signal is received, and wherein said control signals are adjusted according to said exchanged counter values to change said color and maintain said brightness.

10. A method for driving a light source comprising a plurality of light-emitting diodes (LEDs), said method comprising:

delivering power from a converter to said light source;

monitoring a power switch coupled between a power source and said converter;

receiving a color change signal indicating a first set of operations of said power switch;

adjusting color of said light source in response to said color change signal;

receiving a dimming request signal indicating a second set of operations of said power switch;

adjusting brightness of said light source in response to said dimming request signal;

receiving a detection signal indicating a conductance status of said power switch;

identifying a plurality of operations of said power switch comprising a turn-off operation and a turn-on operation according to said detection signal; and

identifying said first set of operations and said second set of operations according to time intervals between said plurality of operations.

11. The method as claimed in claim 10, further comprising:

adjusting the brightness of said light source in response to said dimming request signal until a dimming termination signal is received.