Driving circuit with dimming controller for driving light sources

• US 8,378,589 B2
• Filed: 05/27/2011
• 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:
  US13/117,795
• Publication Number:
  US 20110285323A1
• Time in Patent Office: 634 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 45/3725 Switched mode power supply [SMPS]
• 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 dimming controller for controlling dimming of a light-emitting diode (LED) light source includes a monitoring terminal and a control terminal. The monitoring terminal receives a switch monitoring signal indicative of an operation of a power switch which transfers power from an AC power source to a bridge rectifier when the power switch is on. A power converter receives input power from the bridge rectifier and provides output power to the LED light source. The control terminal generates a control signal to adjust the output power according to the switch monitoring signal so as to control dimming of the LED light source.

Claims

1. A dimming controller for controlling dimming of a light-emitting diode (LED) light source, said dimming controller comprising:

a monitoring terminal configured to receive a switch monitoring signal indicative of an operation of a power switch, wherein said operation of said power switch is selected from a group comprising a turn-on operation and a turn-off operation, wherein said power switch transfers power from an AC power source to a bridge rectifier when said power switch is on, wherein a power converter receives input power from said bridge rectifier and provides output power to said LED light source, and wherein an average current flowing through said LED light source has a first value if said power switch performs a first turn-on operation; and

a control terminal configured to generate a control signal to adjust said average current from said first value to a second value if said switch monitoring signal indicates that said power switch performs a set of operations comprising a second turn-on operation following a turn-off operation so as to control dimming of said LED light source.

2. The dimming controller of claim 1, further comprising:

a trigger monitoring unit configured to receive said switch monitoring signal and generate a driving signal in response to said operation of said power switch; and

a dimmer, coupled to said trigger monitoring unit, and configured to receive said driving signal and generate a dimming signal to adjust said average current flowing through said LED light source.

3. The dimming controller of claim 2, wherein said dimmer comprises:

a counter driven by said driving signal; and

a D/A converter, coupled to said counter, and configured to generate said dimming signal based on a counter value of said counter.

4. The dimming controller of claim 2, wherein said dimming controller operates in a burst dimming mode in which a pulse width modulation signal is generated based on said dimming signal, wherein a duty cycle of said pulse width modulation signal is determined by said dimming signal, and wherein said control signal is determined based on said pulse width modulation signal.

5. The dimming controller of claim 4, further comprising:

a comparator configured to compare a current monitoring signal indicating a current flowing through said LED light source with a reference signal and to generate an output signal, wherein said control signal is determined based on said output signal.

6. The dimming controller of claim 2, wherein said dimming controller operates in an analog dimming mode in which a comparator compares said dimming signal with a current monitoring signal indicating a current flowing through said LED light source and generates an output signal, and wherein said control signal is determined based on said output signal.

7. The dimming controller of claim 1, further comprising:

a current monitoring terminal configured to receive a current monitoring signal indicating a current flowing through said LED light source.

8. The dimming controller of claim 1, further comprising:

a selection terminal configured to select a mode from a burst dimming mode and an analog dimming mode for said dimming controller.

9. A system comprising:

a power converter configured to receive input power from a bridge rectifier and provide output power to a light-emitting diode (LED) light source, wherein a power switch transfers power from an AC power source to said bridge rectifier when said power switch is on; and

a dimming controller, coupled to said power converter, and configured to receive a switch monitoring signal indicative of an operation of said power switch, wherein said operation of said power switch is selected from a group comprising a turn-on operation and a turn-off operation, wherein an average current flowing through said LED light source has a first value if said power switch performs a first turn-on operation, and wherein said dimming controller adjusts said average current from said first value to a second value if said switch monitoring signal indicates that said power switch performs a set of operations comprising a second turn-on operation following a turn-off operation so as to control dimming of said LED light source.

10. The system of claim 9, further comprising:

a control switch coupled in series with said LED light source,

wherein said dimming controller coupled to said control switch adjusts said average current flowing through said LED light source by controlling said control switch according to said switch monitoring signal.

11. The system of claim 9, wherein said dimming controller comprises:

a trigger monitoring unit configured to receive said switch monitoring signal and generate a driving signal in response to said operation of said power switch; and

a dimmer, coupled to said trigger monitoring unit, and configured to receive said driving signal and generate a dimming signal to adjust said average current flowing through said LED light source.

12. The system of claim 11, wherein said dimmer comprises:

a counter driven by said driving signal; and

a D/A converter, coupled to said counter, and configured to generate said dimming signal based on a counter value of said counter.

13. The system of claim 11, wherein said dimming controller operates in a burst dimming mode in which a pulse width modulation signal is generated based on said dimming signal, wherein a duty cycle of said pulse width modulation signal is determined by said dimming signal, and wherein said dimming controller controls a control switch coupled in series with said LED light source according to said pulse width modulation signal.

14. The system of claim 13, wherein said dimming controller further comprises a comparator configured to compare current monitoring signal indicating a current flowing through said LED light source with a reference signal and to generate an output signal, and wherein said dimming controller controls said control switch according to said output signal.

15. The system of claim 11, wherein said dimming controller operates in an analog dimming mode in which a comparator compares said dimming signal with a current monitoring signal indicating a light source current flowing through said light source, and wherein said dimming controller controls a switch coupled in series with said LED light source according to an output signal of said comparator.

16. The system of claim 9, wherein said power converter comprises a DC/DC converter.

17. The system of claim 9, further comprising:

a power storage unit coupled to said dimming controller and configured to power said dimming controller when said power switch is turned off.