Threshold-based zero-crossing detection in an electrical dimmer

• US 8,736,193 B2
• Filed: 12/22/2011
• Issued: 05/27/2014
• Est. Priority Date: 12/22/2011
• Status: Active Grant

• Current Assignee: Leviton Manufacturing Company Incorporated
• Original Assignee: Leviton Manufacturing Company Incorporated
• Inventors: Gallo, Marc
• Primary Examiner(s): A, Minh D
• Application Number:
  US13/334,705
• Publication Number:
  US 20130162167A1
• Time in Patent Office: 887 Days
• Field of Search: 315/291, 315/307, 315/308, 315/224, 315/360, 315/209.R
• US Class Current: 315/291
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Threshold-based zero-crossing detection is provided. A power phase threshold detector detects when absolute value of a voltage level of the electrical power rises above a non-zero voltage threshold and outputs a zero-crossing signal to a controller to indicate occurrence of the zero-crossing. Delaying the zero-crossing signal to the point when the absolute value of the voltage level of the electrical power rises above the non-zero voltage threshold ensures completion of the zero-crossing of the power phase prior to signaling the controller. The controller provides signals to a switching circuit for controlling switching of electrical power to a load based on the zero-crossing indications.

Claims

1. A dimmer for controlling AC electrical power to a load, the dimmer comprising:

a line input terminal and a load output terminal;

a switching circuit electrically coupled between the line input terminal and the load output terminal; and

a threshold detector configured to;

(a) detect when absolute value of a voltage level of the AC electrical power rises above a non-zero voltage threshold indicative of an occurrence of a zero-crossing of the AC electrical power, wherein the non-zero voltage threshold corresponds to a time delay (t) in a cycle of the AC electrical power after the occurrence of the zero-crossing of the AC electrical power; and

(b) output a zero-crossing signal indicative of the occurrence of the zero-crossing of the AC electrical power;

wherein the switching circuit is controlled at least partially by the zero-crossing signal output by the threshold detector.

2. The dimmer of claim 1, wherein the threshold detector further comprises one or more selected from the group consisting of a voltage divider, a comparator, and a transistor.

3. The dimmer of claim 1, wherein the threshold detector further comprises a signaling component, the signaling component configured to output the zero-crossing signal, and wherein the signaling component comprises at least one selected from the group consisting of a transistor, a comparator, and a controller logic.

4. The dimmer of claim 1, wherein the time delay (t) is calculated according to the equation:

5. The dimmer of claim 1, wherein power is delivered to the load during a predetermined portion of the cycle of the AC electrical power with respect to the zero-crossing of the AC electrical power calculated based on the zero-crossing signal and the time delay (t).

6. The dimmer of claim 1, wherein non-zero voltage threshold comprises a value in a range of 20% to 30% of a peak voltage of the AC electrical power.

7. The dimmer of claim 1, wherein the AC electrical power comprises a 120 volts alternating current, and wherein the non-zero voltage threshold comprises a value in a range of 35 to 50 volts.

8. The dimmer of claim 1, wherein the load comprises at least one light emitting diode.

9. The dimmer of claim 1, further comprising a minimum dimming level, wherein if the minimum dimming level is below a minimum voltage level sufficient to power-on the load, the switching circuit is configured to supply a sufficient voltage level to power-on the load.

10. The dimmer of claim 1, wherein the dimmer has a dimming range between a minimum intensity dimming level and a maximum intensity dimming level, and wherein the dimmer further comprises a minimum intensity adjustment setting to set the minimum intensity dimming level of the dimming range.

11. The dimmer of claim 1, further comprising a programming switch for programming at least one of a kick-start mode or a minimum intensity dimming level of the dimmer.

12. A method of controlling AC electrical power to a load, the method comprising:

detecting when absolute value of a voltage level of the AC electrical power rises above a non-zero voltage threshold, the non-zero threshold being indicative of an occurrence of a zero-crossing of the AC electrical power, wherein the non-zero voltage threshold corresponds to a time delay (t) in a cycle of the AC electrical power after the occurrence of zero-crossing of the AC electrical power;

outputting a zero-crossing signal indicative of the occurrence of the zero-crossing of the AC electrical power; and

providing power to the load based at least partially on the zero-crossing signal.

13. The method of claim 12, wherein the step of detecting when the absolute value of the voltage level of the AC electrical power rises above a non-zero voltage threshold further comprises detecting the voltage level of the AC electrical power by using one or more selected from the group consisting of a voltage divider, a comparator, and a transistor.

14. The method of claim 12 wherein the outputting the zero-crossing signal further comprises using one or more from the group consisting of a transistor, a comparator, and controller logic to generate the zero-crossing signal.

15. The method of claim 12 where the step of providing power to the load further comprises providing power to the load during a predetermined portion of the cycle of the AC electrical power with respect to the zero-crossing of the AC electrical power calculated based on the zero-crossing signal and the time delay (t).

16. The method of claim 12, wherein the time delay (t) is calculated according to the equation:

17. The method of claim 12, wherein the AC electrical power comprises a 120 volts alternating current, and wherein the non-zero voltage threshold comprises a value in a range of 35 to 50 volts.

18. The method of claim 12, wherein the step of providing power to the load further comprises providing power to at least one light emitting diode.

19. The method of claim 12, wherein the method is implemented within a dimmer, wherein when the dimmer is set to provide power to the load below a minimum voltage level sufficient to power-on the load, the method further comprises applying a voltage level above the minimum voltage level sufficient to power-on the load.

20. The method of claim 19, wherein the voltage level is subsequently decreased to the set voltage level of the dimmer.

21. The method of claim 12, wherein the method is implemented within a dimmer, wherein the dimmer has a dimming range between a minimum intensity dimming level and a maximum intensity dimming level, and wherein the method further comprises providing a minimum intensity adjustment setting for setting of the minimum intensity dimming level of the dimming range.

22. The method of claim 12, wherein the method is implemented within a dimmer, and wherein the method further comprises providing a programming switch for programming at least one of a kick-start mode or a minimum intensity dimming level of the dimmer.