Input voltage sensing for a switching power converter and a triac-based dimmer
An electronic lighting system and method described herein control energy provided to an electronic lighting device, such as one or more light-emitting diodes (LEDs) and/or compact fluorescent lamps (CFLs), of the electronic lighting system. A triac-based dimmer phase cuts a line voltage provided to the electronic lighting system. A controller of the electronic lighting system utilizes a probing system to overcome idiosyncrasies of the triac-based dimmer to allow the controller to probe and sense the line voltage. To reduce energy consumption, rather than probing each cycle of the output voltage of the triac-based dimmer, the controller periodically or intermittently probes the output voltage of the triac-based dimmer.
1. A method comprising:
controlling energy transfer in a switching power converter; and
during the controlling of energy transfer in the switching power converter, probing an output of a triode for alternating current (“triac”)-based dimmer only every Nth half cycle of an alternating current (AC) output voltage of the dimmer to allow a controller of a lighting system to sense the output voltage from a time when the triac connects an input voltage source to an output of the dimmer until an occurrence of a predetermined event, wherein N is an integer greater than 1.
2. The method of claim 1 wherein the predetermined event is a time when the triac disconnects the input voltage source from the output of the dimmer.
3. The method of claim 1 wherein the predetermined event is when the output voltage reaches a predetermined threshold value.
4. The method of claim 1 wherein N varies over time.
5. The method of claim 1 wherein N is a constant.
6. The method of claim 1 wherein N is odd.
7. The method of claim 1 further comprising:
detecting an approximate zero crossing of the output voltage of the dimmer from the sensed output voltage of the dimmer.
8. The method of claim 1 further comprising:
detecting a type of the dimmer from the sensed output voltage of the dimmer.
9. The method of claim 1 wherein probing the output of a triac-based dimmer comprises:
introducing a resistance coupled to the output of the dimmer sufficient to prevent the triac from disconnecting prior to reaching a predetermined voltage level.
10. The method of claim 1 wherein probing the output of a triac-based dimmer comprises:
introducing a current source coupled to the output of the dimmer sufficient to prevent the triac from disconnecting prior to reaching a predetermined voltage level.
11. The method of claim 9 wherein the predetermined voltage level is an approximately zero voltage of the output voltage of the dimmer.
12. The method of claim 1 further comprising:
operating the lighting system in accordance with information derived from the sensed output voltage of the dimmer.
13. The method of claim 12 wherein the lighting system includes one or more light emitting diodes.
14. An apparatus comprising:
a controller to control energy transfer in a switching power converter of a lighting system, wherein the controller is configured to:
during control of energy transfer in the switching power converter, generate a control signal to control probing an output of a triode for alternating current (“triac”) based dimmer only every Nth half cycle of an alternating current (AC) output voltage of the dimmer to allow the controller to sense the output voltage from a time when the triac connects an input voltage source to an output of the dimmer until an occurrence of a predetermined event, wherein N is an integer greater than 1.
15. The apparatus of claim 14 wherein the predetermined event is a time when the triac disconnects the input voltage source from the output of the dimmer.
16. The apparatus of claim 14 wherein the predetermined event is when the output voltage reaches a predetermined threshold value.
17. The apparatus of claim 14 wherein N varies over time.
18. The apparatus of claim 14 wherein N is a constant.
19. The apparatus of claim 14 wherein N is odd.
20. The apparatus of claim 14 wherein the controller is further configured to detect an approximate zero crossing of the output voltage of the dimmer from the sensed output voltage of the dimmer.
21. The apparatus of claim 14 wherein the controller is further configured to detect a type of the dimmer from the sensed output voltage of the dimmer.
22. The apparatus of claim 14 further comprising:
a probing circuit coupled to the controller and an output of the dimmer, wherein the probing circuit comprises a switch and a resistor coupled to the switch, wherein the control signal controls the switch to couple the resistor to the dimmer and prevent the triac from disconnecting prior to reaching a predetermined voltage level.
23. The apparatus of claim 22 wherein the predetermined voltage level is an approximately zero voltage of the output voltage of the dimmer.
24. The apparatus of claim 14 further comprising:
a probing circuit coupled to the controller and an output of the dimmer, wherein the probing circuit comprises a controllable constant current source, wherein the control signal controls the constant current source so that the constant current source generates a current through the dimmer to prevent the triac from disconnecting prior to reaching a predetermined voltage level.
25. The apparatus of claim 14 wherein the controller is further configured to operate the switching power converter in accordance with information derived from the sensed output voltage of the dimmer to control at least a brightness of one or more lighting devices.
26. The apparatus of claim 25 wherein the one or more lighting devices include one or more light emitting diodes.
27. An electronic lighting system comprising:
a switching power converter;
a controller, coupled to the switching power converter, to control energy transfer in a switching power converter of a lighting system, wherein the controller is configured to:
during control of energy transfer in the switching power converter, generate a control signal to control probing an output of a triode for alternating current (“triac”) based dimmer only every Nth half cycle of an alternating current (AC) output voltage of the dimmer to allow the controller to sense the output voltage from a time when the triac connects an input voltage source to an output of the dimmer until an occurrence of a predetermined event, wherein N is an integer greater than 1; and
an electronic lighting device, coupled to the controller and the switching power converter.
28. The electronic lighting system of claim 27 wherein the electronic lighting device comprises one or more light emitting diodes.
29. The electronic lighting system of claim 27 wherein the switching power converter is a two stage switching power converter.
30. The electronic lighting system of claim 27 wherein the predetermined event is a time when the triac disconnects the input voltage source from the output of the dimmer.
31. The electronic lighting system of claim 27 wherein the predetermined event is when the output voltage reaches a predetermined threshold value.
32. The electronic lighting system of claim 27 wherein N varies over time.
33. The electronic lighting system of claim 27 wherein N is a constant.
34. The electronic lighting system of claim 27 wherein the controller is further configured to detect an approximate zero crossing of the output voltage of the dimmer from the sensed output voltage of the dimmer.
35. The electronic lighting system of claim 27 wherein the controller is further configured to detect a type of the dimmer from the sensed output voltage of the dimmer.