Driving circuit with dimming controller for driving light sources

• US 8,044,608 B2
• Filed: 12/12/2008
• Issued: 10/25/2011
• 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): Choi; Jacob Y
• Assistant Examiner(s): Vu; Jimmy T
• Application Number:
  US12/316,480
• Publication Number:
  US 20100148691A1
• Time in Patent Office: 1,047 Days
• Field of Search: 315/185.R, 315/224, 315/225, 315/244, 315/245, 315/287, 315/291, 315/307, 315/312, 315/314, 315/186, 315/193, 315/210, 315/211, 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

There is provided a driving circuit for controlling power of a light source. The driving circuit includes a power converter and a dimming controller. The power converter is coupled between a power source and the light source, and can receive power from the power source and provide a regulated power to the light source. The dimming controller is coupled to the power converter, and can receive a switch monitoring signal. The switch monitoring signal can indicate an operation of a power switch coupled between the power source and the driving circuit. The dimming controller is further operable for adjusting the regulated power from the power converter by controlling a switch coupled in series with the light source according to the switch monitoring signal.

Claims

1. A driving circuit for controlling power of a light emitting diode (LED) light source, comprising:

a power converter coupled between a power source and said LED light source and for receiving power from said power source and for providing regulated power to said LED light source; and

a dimming controller coupled to said power converter and for receiving a switch monitoring signal indicative of an operation of a power switch coupled between said power source and said driving circuit, and for adjusting said regulated power from said power converter by controlling a switch coupled in series with said LED light source according to said switch monitoring signal, wherein said dimming controller comprises;

a trigger monitoring unit for receiving said switch monitoring signal and for generating a driving signal in response to said operation of said power switch; and

a dimmer coupled to said trigger monitoring unit and for receiving said driving signal and for generating a dimming signal to adjust a target power level of said power converter.

2. The driving circuit of claim 1, wherein said operation of said power switch comprises a turn-off operation.

3. The driving circuit of claim 1, wherein said dimmer comprises:

a counter driven by said driving signal; and

a D/A converter coupled to said counter for generating said dimming signal based on a counter value of said counter.

4. The driving circuit of claim 1, 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 pulse width modulation signal controls said switch coupled in series with said LED light source.

5. The driving circuit of claim 1, 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 LED light source and generates a control signal to control said switch in series with said LED light source.

6. The driving circuit of claim 1, wherein said dimming controller comprises:

a pulse generator for generating a pulse signal; and

a flip-flop coupled to said pulse generator for generating a control signal to control said switch coupled in series with said LED light source.

7. A system comprising:

a power converter coupled between a power source and a light emitting diode (LED) light source and for receiving power from said power source and for providing regulated power to said LED light source; and

a dimming controller coupled to said power converter for receiving a switch monitoring signal indicative of an operation of a power switch coupled to said power source and for adjusting said regulated power from said power converter according to said switch monitoring signal, wherein said dimming controller comprises a counter for counting said operation of said power switch, wherein said dimming controller comprises;

a trigger monitoring unit for receiving said switch monitoring signal and for generating a driving signal in response to said operation of said power switch; and

a dimmer coupled to said trigger monitoring unit and for receiving said driving signal and for generating a dimming signal to adjust a target power level of said power converter.

8. The system of claim 7, further comprising:

a switch coupled in series with said LED light source,

wherein said dimming controller is coupled to said switch and is operable for adjusting said regulated power from said power converter by controlling said switch.

9. The system of claim 7, further comprising:

an AC/DC converter for converting an AC power from said power source to a DC power, and wherein said power switch is coupled between said power source and said AC/DC converter.

10. The system of claim 7, wherein said driving circuit further comprises:

a power storage unit coupled to said dimming controller for powering said dimming controller when said power switch is turned off.

11. The system of claim 7, wherein said dimmer comprises:

said counter, wherein said counter is driven by said driving signal; and

a D/A converter coupled to said counter for generating said dimming signal based on a counter value of said counter.

12. The system of claim 7, 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 pulse width modulation signal controls a switch coupled in series with said LED light source.

13. The system of claim 7, 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 LED light source and generates a control signal to control a switch coupled in series with said LED light source.

14. A dimming controller coupled to a light emitting diode (LED) light source, comprising:

a switch monitoring terminal operable for monitoring an operation of a power switch coupled between a power source and said LED light source;

a counter coupled to said switch monitoring terminal operable for counting said operation of said power switch;

a current monitoring terminal operable for receiving a current monitoring signal indicating a current flowing through said LED light source;

a selection terminal operable for selecting a mode from a burst dimming mode and an analog dimming mode for said dimming controller; and

a control terminal operable for generating a control signal to control a second switch in series with said LED light source to adjust power to said LED light source based on a counter value of said counter and said current monitoring signal.

15. The dimming controller of claim 14, wherein said operation of said power switch comprises a turn-off operation.

16. The dimming controller of claim 14, further comprising:

a trigger monitoring unit operable for receiving a switch monitoring signal indicative of said operation of said power switch from said switch monitoring terminal and for generating a driving signal in response to said operation of said power switch; and

a dimmer coupled to said trigger monitoring unit and operable for receiving said driving signal and for generating a dimming signal to adjust said power to said LED light source.

17. The dimming controller of claim 16, wherein said dimming controller operates in said 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 generated according to said pulse width modulation signal.

18. The dimming controller of claim 16, wherein said dimming controller operates in said analog dimming mode in which a comparator compares said dimming signal with said current monitoring signal, and wherein said control signal is generated according to a comparison result of said comparator.