Dimmer output emulation

• US 8,569,972 B2
• Filed: 08/17/2010
• Issued: 10/29/2013
• Est. Priority Date: 08/17/2010
• Status: Expired due to Fees

• Current Assignee: Philips Lighting Holding BV (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Primary Examiner(s): Cho, James H
• Application Number:
  US12/858,164
• Publication Number:
  US 20120043913A1
• Time in Patent Office: 1,169 Days
• Field of Search: 315/209.R, 315/227.R, 315/246, 315/247, 315/283, 315/291, 315/307, 315/308, 315/360
• US Class Current: 315/307
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A lighting system includes a dimmer output voltage emulator to cause a power converter interface circuit to generate an emulated dimmer output voltage. In at least one embodiment, the emulated dimmer output voltage corresponds to an actual dimmer output voltage but is unaffected by non-idealities in the dimmer output voltage, such as premature shut-down of a triac-based dimmer. By generating an emulated dimmer output voltage, the energy delivered to a load, such as a lamp, corresponds to a dimming level setting.

Claims

1. An apparatus comprising:

a dimmer output voltage emulator configured to cause a power converter interface circuit to draw current from a capacitor in the power converter interface during a period of time when a dimmer coupled to the power converter interface circuit is non-conducting to generate an emulated dimmer output voltage, wherein the emulated dimmer output voltage emulates part of a cycle of a non-zero alternating current dimmer output voltage of the dimmer after a triac of the dimmer prematurely stops conducting that would occur if the triac continued conducting during the part of the cycle.

2. The apparatus of claim 1 wherein the emulated dimmer output voltage is generally decreasing over time during the emulated part of the dimmer output voltage cycle.

3. The apparatus of claim 1 wherein the emulated dimmer output voltage comprises multiple linear segments each having a unique slope.

4. The apparatus of claim 1 wherein the emulated dimmer output voltage comprises a concave parabolic waveform.

5. The apparatus of claim 1 wherein the dimmer output voltage emulator is further configured to provide current that interacts with components of the power interface circuit to provide the emulated dimmer output voltage.

6. The apparatus of claim 1 wherein the dimmer output voltage emulator comprises a pull-down circuit to pull-down current of the power converter interface circuit and generally decrease the emulated dimmer output voltage during a first period of time and a glue circuit to maintain the emulated dimmer output voltage below a threshold value during a second period of time.

7. The apparatus of claim 6 wherein the glue circuit provides a steady state current draw from the power converter interface circuit to maintain the emulated dimmer output voltage below the threshold value during the second period of time.

8. The apparatus of claim 6 wherein the first period of time begins when a triac of a triac-based dimmer circuit ceases conducting during a cycle of an AC supply voltage, the second period of time begins when the supply voltage is below the threshold voltage, the first period ends when the second period begins, and the second period ends when the supply voltage begins to increase.

9. A method comprising:

causing a power converter interface circuit to draw current from a capacitor in the power converter interface during a period of time when a dimmer coupled to the power converter interface circuit is non-conducting to generate an emulated dimmer output voltage, wherein the emulated dimmer output voltage emulates part of a cycle of a non-zero alternating current dimmer output voltage of the dimmer after a triac of the dimmer prematurely stops conducting that would occur if the triac continued conducting during the part of the cycle.

10. The method of claim 9 wherein causing the power converter interface circuit to generate an emulated dimmer output voltage comprises generally decreasing the emulated dimmer output voltage over time during the emulated part of the dimmer output voltage cycle.

11. The method of claim 9 wherein causing the power converter interface circuit to generate an emulated dimmer output voltage causing the power converter interface circuit to generate the emulated dimmer output voltage to include multiple linear segments each having a unique slope.

12. The method of claim 9 wherein causing the power converter interface circuit to generate an emulated dimmer output voltage causing the power converter interface circuit to generate the emulated dimmer output voltage comprises generating the emulated dimmer output voltage to include a convex parabolic waveform.

13. The method of claim 9 further comprising:

providing current that interacts with components of the power interface circuit to provide the emulated dimmer output voltage.

14. The method of claim 9 further comprising:

pulling-down current of the power converter interface circuit to generally decrease the emulated dimmer output voltage during a first period of time; and

maintaining the emulated dimmer output voltage below a threshold value during a second period of time.

15. The method of claim 14 further comprising:

drawing a steady state current from the power converter interface circuit to maintain the emulated dimmer output voltage below the threshold value during the second period of time.

16. The method of claim 14 wherein the first period of time begins when a triac of a triac-based dimmer circuit ceases conducting during a cycle of an AC supply voltage, the second period of time begins when the supply voltage is below the threshold voltage, the first period ends when the second period begins, and the second period ends when the supply voltage begins to increase.

17. The method of claim 9 further comprising:

generating an emulated dimmer output voltage in a power converter interface circuit, wherein the emulated dimmer output voltage emulates part of a cycle of an alternating current dimmer output voltage of the dimmer.

18. An apparatus comprising:

a dimmer;

a power converter interface circuit coupled to the dimmer;

a dimmer output voltage emulator, coupled to the power converter interface circuit, wherein (i) the dimmer output voltage emulator is configured to cause the power converter interface circuit to draw current from a capacitor in the power converter interface during a period of time when the dimmer coupled to the power converter interface circuit is non-conducting to generate an emulated dimmer output voltage and (ii) the emulated dimmer output voltage emulates part of a cycle of an alternating current dimmer output voltage of the dimmer;

a power converter coupled to the dimmer output voltage emulator; and

a controller coupled to the dimmer output voltage emulator and the power converter, wherein the controller is configured to control the power converter in accordance with the emulated dimmer output voltage.

19. The apparatus of claim 18 wherein:

the dimmer comprises a triac-based dimmer; and

the power converter is a switching power converter.

21. The apparatus of claim 18 wherein the emulated dimmer output voltage emulates part of a cycle of a non-zero portion of the alternating current dimmer output voltage of the dimmer after a triac of the dimmer prematurely stops conducting that would occur if the triac continued conducting during the part of the cycle.

20. An apparatus comprising:

means for causing a power converter interface circuit to draw current from a capacitor in the power converter interface during a period of time when a dimmer coupled to the power converter interface circuit is non-conducting to generate an emulated dimmer output voltage, wherein the emulated dimmer output voltage emulates part of a cycle of a non-zero alternating current dimmer output voltage of the dimmer after a triac of the dimmer prematurely stops conducting that would occur if the triac continued conducting during the part of the cycle.