Controllers, systems and methods for controlling dimming of light sources

• US 8,508,150 B2
• Filed: 03/07/2011
• Issued: 08/13/2013
• 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:
  US13/042,349
• Publication Number:
  US 20110181199A1
• Time in Patent Office: 890 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
• US Class Current: 315/291
• CPC Class Codes: H05B 45/10 Controlling the intensity 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 controller for controlling dimming of an LED light source includes a control terminal and dimming control circuitry coupled to the control terminal. The control terminal provides a driving signal to control a control switch coupled to the LED light source, thereby controlling the dimming of the LED light source. The dimming control circuitry generates the driving signal according to a set of operations of a power switch that transfers an AC signal. The dimming control circuitry further adjusts the driving signal by counting multiple waves of the AC signal to control the dimming of the LED light source.

Claims

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

a control terminal operable for providing a driving signal to control a control switch coupled to said LED light source, thereby controlling said dimming of said LED light source; and

dimming control circuitry coupled to said control terminal and operable for generating said driving signal according to a plurality of operations of a power switch that transfers an alternating-current (AC) signal, said dimming control circuitry operable for counting a number of waves of said AC signal, and operable for adjusting said driving signal according to said number of said waves.

2. The controller of claim 1, wherein said AC signal comprises an AC voltage provided by an AC power source.

3. The controller of claim 1, wherein said dimming control circuitry counts said waves of said AC signal by counting pulses of a clock signal.

4. The controller of claim 3, wherein said dimming control circuitry compares a periodic signal indicative of said AC signal with a voltage reference to generate said clock signal.

5. The controller of claim 1, wherein said dimming control circuitry adjusts a dimming signal by counting said waves of said AC signal to adjust said driving signal.

6. The controller of claim 5, wherein said dimming control circuitry controls said dimming signal from a first preset level to a second preset level when said number of said waves exceeds a predetermined number.

7. The controller of claim 5, wherein said dimming control circuitry comprises:

a trigger monitoring unit operable for monitoring said power switch and generating a pulse in response to a detection of said operations of said power switch; and

a dimmer coupled to said trigger monitoring unit and operable for counting said waves to adjust said dimming signal based on said pulse.

8. The controller of claim 7, wherein if said trigger monitoring unit generates a first pulse based on said operations, said first pulse enables said counting of said waves to adjust said dimming signal to a level, and wherein if said trigger monitoring unit generates a second pulse based on said operations, said second pulse disables said counting of said waves to maintain said dimming signal at said level.

9. The controller of claim 5, wherein said dimming signal comprises a reference signal, and wherein said controller controls said dimming of said LED light source by comparing said reference signal with a monitoring signal indicative of a current flowing through said LED light source.

10. The controller of claim 5, wherein said dimming signal comprises a pulse-width modulation (PWM) signal, and wherein said controller controls said dimming of said LED light source according to said PWM signal and a pulse signal.

11. The controller of claim 1, wherein said operations of said power switch comprise turning off said power switch followed by turning on said power switch within a predefined time interval.

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

transferring an alternating-current (AC) signal through a power switch;

generating a driving signal according to a plurality of operations of said power switch;

counting waves of said AC signal;

adjusting said driving signal according to the number of said waves obtained by said counting; and

controlling a control switch coupled to said LED light source by said driving signal to control said dimming of said LED light source.

13. The method of claim 12, wherein said adjusting of said driving signal comprises:

comparing a periodic signal indicative of said AC signal with a voltage reference to generate a clock signal; and

counting said waves of said AC signal by counting pulses of said clock signal.

14. The method of claim 12, wherein said adjusting of said driving signal comprises:

adjusting a dimming signal by counting said waves of said AC signal to adjust said driving signal.

15. The method of claim 14, wherein said adjusting of said driving signal comprises:

controlling said dimming signal from a first preset level to a second preset level when said number of said waves exceeds a predetermined number.

16. The method of claim 14, wherein said generating of said driving signal comprises:

enabling said counting of said waves to adjust said dimming signal to a level if a first pulse is generated based on said operations; and

disabling said counting of said waves to maintain said dimming signal at said level if a second pulse is generated based on said operations.

17. A system for powering a light-emitting diode (LED) light source, said system comprising:

conversion circuitry operable for receiving an alternating-current (AC) signal through a power switch and providing regulated power to said LED light source; and

dimming control circuitry coupled to said conversion circuitry and operable for generating a dimming signal according to a plurality of operations of said power switch, operable for counting waves of said AC signal, and operable for adjusting said dimming signal according to the number of said waves obtained by said counting, wherein dimming of said LED light source is controlled according to said dimming signal.

18. The system of claim 17, wherein said conversion circuitry comprises:

an alternating-current to direct-current (AC/DC) converter for converting AC power to DC power; and

a DC/DC converter coupled to said AC/DC converter and for converting said DC power to said regulated power by controlling a control switch in series with said LED light source according to said dimming signal.

19. The system of claim 17, wherein said dimming control circuitry compares a periodic signal indicative of said AC signal with a voltage reference to generate a clock signal and counts said waves of said AC signal by counting pulses of said clock signal.

20. The system of claim 17, wherein said dimming control circuitry controls said dimming signal from a first preset level to a second preset level when said number of said waves exceeds a predetermined number.