Method and apparatus for dimming

• US 8,558,474 B1
• Filed: 11/24/2010
• Issued: 10/15/2013
• Est. Priority Date: 11/25/2009
• Status: Expired due to Fees

• Current Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Zhang, Wanfeng, Choi, Jinho, Park, Yangsoo
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US12/954,047
• Time in Patent Office: 1,056 Days
• Field of Search: 315/291, 315/247, 315/224, 315274-279, 315/307, 315/185.S, 315312-326
• US Class Current: 315/247
• 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 45/385 using flyback 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 lighting system includes a transformer having a primary winding on a receiving path and a secondary winding on a delivering path. The receiving path receives electric energy regulated based on a dimming angle. The delivering path delivers the received electric energy. The lighting system includes a secondary switch, and a dimming controller. The secondary switch is switched on to couple a light source, such as an LED array, and the like, with the delivering path to emit light in response to the delivered electric energy and is switched off to decouple the light source from the delivering path. The dimming controller is configured to detect the dimming angle based on an electrical property of the delivering path. Then, the dimming controller switches on and switches off the secondary switch based on the dimming angle.

Claims

1. A lighting system, comprising:

a transformer having a primary winding on a receiving path and a secondary winding on a delivering path, the receiving path receiving electric energy regulated based on a dimming angle, the received electric energy being delivered by the delivering path;

a secondary switch being switched on to couple a light source with the delivering path to emit light in response to the delivered electric energy and being switched off to decouple the light source from the delivering path; and

a dimming controller configured to detect the dimming angle based on an electrical property of the delivering path, and switch on and switch off the secondary switch based on the dimming angle, the dimming controller including a counter configured to provide a count based on a voltage signal on the secondary winding.

2. The lighting system of claim 1, wherein the received electric energy is regulated by a triode for alternating current (TRIAC) dimmer.

3. The lighting system of claim 1, wherein the dimming controller further comprises:

a low pass filter configured to pass low frequency components of the voltage signal on the secondary winding;

a comparator configured to compare the filtered voltage signal with a reference signal to generate a rectangular shaped signal;

the counter configured to count a number corresponding to a width of the rectangular shaped signal; and

a dimming angle determination module configured to determine the dimming angle based on the counted number.

4. The lighting system of claim 1, wherein the light source is a light emitting diode (LED) array

the secondary switch is switched on to couple the light emitting diode (LED) array with the delivering path to emit light in response to the delivered electric energy and is switched off to decouple the LED array from the delivering path.

5. The lighting system of claim 1, further comprising:

a primary switch being switched on to enable the receiving path, and being switched off to disable the receiving path and to allow the delivering path to deliver the received electric energy.

6. The lighting system of claim 5, further comprising:

a primary controller configured to generate first pulses and to use the first pulses to switch on and switch off the primary switch.

7. The lighting system of claim 1, wherein the dimming controller is configured to generate second pulses having widths that are modulated based on the dimming angle, and the second pulses being used to control the secondary switch.

8. The lighting system of claim 7, wherein the dimming controller is configured to modulate the widths according to a sine wave that is regulated based on the dimming angle.

9. An integrated circuit (IC), comprising:

a secondary transistor switch being switched on to couple a light source with a delivering path for delivering electric energy received and stored by a transformer, and being switched off to decouple the light source from the delivering path, the transformer having a primary winding on a receiving path to receive electric energy regulated based on a dimming angle and a secondary winding on the delivering path; and

a dimming controller configured to detect the dimming angle based on an electrical property of the delivering path and switch on and switch off the secondary transistor switch based on the detected dimming angle, the dimming controller including a counter configured to provide a count based on a voltage signal on the secondary winding.

10. The IC of claim 9, wherein the received electric energy is regulated by a triode for alternating current (TRIAC) dimmer.

11. The IC of claim 9, wherein the dimming controller is configured to generate second pulses having widths that are modulated based on the dimming angle, and the second pulses being used to control the secondary transistor switch.

12. The IC of claim 9, wherein the dimming controller is configured to modulate the widths according to a sine wave that is regulated based on the dimming angle.

13. The IC of claim 9, wherein the dimming controller further comprises:

a low pass filter configured to pass low frequency components of the voltage signal on the secondary winding;

a comparator configured to compare the filtered voltage signal with a reference signal to generate a rectangular shaped signal;

the counter configured to count a number corresponding to a width of the rectangular shaped signal; and

a dimming angle determination module configured to determine the dimming angle based on the counted number.

14. The IC of claim 9, further comprising:

a primary transistor switch being switched on to enable the receiving path, and being switched off to disable the receiving path and to allow the delivering path to deliver the received electric energy.

15. The IC of claim 14, further comprising:

a primary switch controller configured to generate first pulses and to use the first pulses to switch on and switch off the primary transistor switch.

16. A method, comprising:

repetitively switching on a primary switch on a receiving path to allow a transformer to receive and store electric energy regulated based on a dimming angle, and switching off the primary switch to deliver the stored electric energy via a delivering path, the transformer having a primary winding on the receiving path and a secondary winding on the delivering path;

detecting the dimming angle based on an electrical property on the delivering path, wherein the detecting the dimming angle further comprises counting a number, by a counter, based on a voltage signal on the secondary winding; and

switching on and switching off a secondary switch to couple and decouple a light source based on the detected dimming angle.

17. The method of claim 16, wherein switching on and switching off the secondary switch based on the detected dimming angle to couple and decouple the light source, further comprises:

generating pulses having widths that are modulated based on the dimming angle; and

using the pulses to control the secondary switch.

18. The method of claim 17, wherein generating the pulses having the widths that are modulated based on the dimming angle further comprises:

modulating the widths of the pulses based on a sine wave that is regulated based on the dimming angle.

19. The method of claim 16, wherein detecting the dimming angle based on the electrical property on the delivering path further comprises:

detecting the dimming angle based on the voltage signal on the secondary winding.

20. The method of claim 19, further comprising:

filtering the voltage signal to pass low frequency components;

comparing the filtered voltage signal with a reference signal to generate a rectangular shaped signal;

measuring a width of the rectangular shaped signal by counting the number corresponding to the width; and

determining the dimming angle based on the width of the rectangular shaped signal.