LED DIMMER CONTROL

• US 20110115400A1
• Filed: 11/17/2010
• Published: 05/19/2011
• Est. Priority Date: 11/17/2009
• Status: Abandoned Application

• Current Assignee: LEDVANCE LLC (MLS Co. Ltd.)
• Original Assignee: LEDVANCE LLC (MLS Co. Ltd.)
• Inventors: Harrison, Daniel J., Davis, Steven S.
• Application Number:
  US12/948,589
• Publication Number:
  US 20110115400A1
• Time in Patent Office: Days
• US Class Current: 315/287
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 45/59 for reducing or suppressing flicker or glow effects

Abstract

A circuit dims an LED based on a duty cycle detected in an incoming power signal.

Claims

1. A dimmer adapter, responsive to a dimming signal, for dimming an LED, the adapter comprising:

a duty-cycle estimator for estimating a duty cycle of an input power signal; and

a signal generator for producing a dimming signal in response to the estimated duty cycle.

2. The dimmer adapter of claim 1, further comprising a transformer type detector for detecting a type of a transformer used to generate the input power signal.

3. The dimmer adapter of claim 2, wherein the duty-cycle estimator estimates the duty cycle based at least in part on the detected transformer type.

4. The dimmer adapter of claim 1, wherein the duty-cycle estimator comprises a zero-crossing detector.

5. The dimmer adapter of claim 4, wherein the zero-crossing detector comprises a filter for filtering out a zero-crossing signal having a time period between consecutive zero crossings less than a predetermined threshold.

6. The dimmer adapter of claim 1, further comprising:

a phase-clip estimator for estimating phase clipping in the dimming signal; and

a bleeder control circuit for controlling a bleeder circuit based at least in part on the estimated phase clipping.

7. The dimmer adapter of claim 6, wherein the phase-clip estimator determines when the phase clipping starts based at least in part on a previously-observed cycle.

8. The dimmer adapter of claim 7, wherein the phase-clip estimator determines when the phase clipping ends based at least in part on a previously-observed cycle.

9. The dimmer adapter of claim 7, wherein the bleeder control circuit activates the bleeder circuit prior to the beginning of the phase clipping.

10. The dimmer adapter of claim 9, wherein the bleeder control circuit de-activates the bleeder circuit after the end of the phase clipping.

11. A method for dimming an LED in response to a dimming signal, the method comprising:

estimating a duty cycle of an input power signal; and

producing a dimming signal in response to the estimated duty cycle.

12. The method of claim 11, further comprising detecting a type of a transformer used to generate the input power signal.

13. The method of claim 11, wherein estimating the duty cycle comprises detecting zero crossings of the input power signal.

14. The method of claim 13, further comprising filtering out high-frequency zero crossings.

15. The method of claim 11, further comprising estimating phase clipping in the dimming signal.

16. The method of claim 15, further comprising engaging a bleeder circuit during the phase clipping.

17. The method of claim 16, wherein the duty cycle is estimated while the bleeder circuit is engaged.