DIMMER-DISABLED LED DRIVER

• US 20130069555A1
• Filed: 11/16/2012
• Published: 03/21/2013
• Est. Priority Date: 06/30/2010
• Status: Active Grant

• Current Assignee: Balu Balakrishnan
• Original Assignee: Balu Balakrishnan
• Inventors: Balakrishnan, Balu
• Granted Patent: US 8,816,596 B2
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An integrated circuit controller for use in a light emitting diode (LED) driver includes a comparator, an input signal absence timer and a regulator circuit. The comparator receives a first voltage representative of an ac input signal and compares the first voltage with a reference voltage. The input signal absence timer determines whether the first voltage is less than the reference voltage for a threshold duration and in response thereto generates a detect signal indicating that a portion of an ac half cycle is absent from the ac input signal. The regulator circuit controls switching of a switch to regulate a transfer of energy from the ac input signal to an LED load. The regulator circuit is disabled from switching the switch in response to the detect signal indicating the absence of the portion of the ac half cycle from the ac input signal.

Claims

1. An integrated circuit controller for use in a light emitting diode (LED) driver, the controller comprising:

a comparator coupled to receive a first voltage representative of an ac input signal and to compare the first voltage with a reference voltage;

an input signal absence timer coupled to an output of the comparator to determine whether the first voltage is less than the reference voltage for a threshold duration and in response thereto generate a detect signal indicating that a portion of an ac half cycle is absent from the ac input signal; and

a regulator circuit coupled to control switching of a switch to regulate a transfer of energy from the ac input signal to an LED load to be coupled to an output of the LED driver, the regulator circuit coupled to be disabled from switching the switch in response to the detect signal indicating the absence of the portion of the ac half cycle from the ac input signal.

2. The integrated circuit controller of claim 1, wherein the reference voltage has a value such that the first voltage being less than the reference voltage indicates that the ac input signal is substantially zero.

3. The integrated circuit controller of claim 1, further comprising a signal absence counter to detect the absence of the portion of the ac half cycle for consecutive ac half cycles of the ac input signal in response to the detect signal, wherein the regulator circuit is disabled from switching the switch in response to the signal absence counter detecting the absence of the portion of the ac half cycle for consecutive ac half cycles.

4. The integrated circuit controller of claim 3, wherein the regulator circuit comprises a latch coupled to the signal absence counter and to disable the regulator circuit in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.

5. The integrated circuit controller of claim 4, wherein the latch is further coupled to enable the regulator circuit to switch the switch in response to a presence of a substantially entire ac input signal for at least one ac half cycle of the ac input signal.

6. The integrated circuit controller of claim 4, wherein the regulator circuit further comprises an oscillator coupled to generate an oscillating signal, wherein the regulator circuit generates a drive signal in response to the oscillating signal to control the switching of the switch, and wherein the latch is coupled to disable the oscillator from generating the oscillating signal in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.

7. The integrated circuit controller of claim 4, wherein the regulator circuit further comprises a logic gate that generates a drive signal to control switching of the switch, and wherein the latch is coupled to disable the logic gate from providing the drive signal in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.

8. The integrated circuit controller of claim 1, wherein the switch is included in the integrated circuit controller.

16. The LED driver circuit of claim 1, wherein the switch is included in the integrated circuit controller.

9. A light emitting diode (LED) driver circuit, comprising:

an energy transfer element coupled to an input and to an output of the LED driver circuit;

a switch coupled to the energy transfer element; and

an integrated circuit controller coupled to the switch, the controller comprising;

a comparator coupled to receive a first voltage representative of an ac input signal at the input and to compare the first voltage with a reference voltage;

an input signal absence timer coupled to an output of the comparator to determine whether the first voltage is less than the reference voltage for a threshold duration and in response thereto generate a detect signal indicating that a portion of an ac half cycle is absent from the ac input signal; and

a regulator circuit coupled to control switching of the switch to regulate a transfer of energy from the ac input signal to an LED load to be coupled to the output of the LED driver circuit, the regulator circuit coupled to be disabled from switching the switch in response to the detect signal indicating the absence of the portion of the ac half cycle from the ac input signal.

10. The LED driver circuit of claim 9, wherein the reference voltage has a value such that the first voltage being less than the reference voltage indicates that the ac input signal is substantially zero.

11. The LED driver circuit of claim 9, wherein the integrated circuit controller further comprises a signal absence counter to detect the absence of the portion of the ac half cycle for consecutive ac half cycles of the ac input signal in response to the detect signal, wherein the regulator circuit is disabled from switching the switch in response to the signal absence counter detecting the absence of the portion of the ac half cycle for consecutive ac half cycles.

12. The LED driver circuit of claim 11, wherein the regulator circuit comprises a latch coupled to the signal absence counter and to disable the regulator circuit in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.

13. The LED driver circuit of claim 12, wherein the latch is further coupled to enable the regulator circuit to switch the switch in response to a presence of a substantially entire ac input signal for at least one ac half cycle of the ac input signal.

14. The LED driver circuit of claim 12, wherein the regulator circuit further comprises an oscillator coupled to generate an oscillating signal, wherein the regulator circuit generates a drive signal in response to the oscillating signal to control the switching of the switch, and wherein the latch is coupled to disable the oscillator from generating the oscillating signal in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.

15. The LED driver circuit of claim 12, wherein the regulator circuit further comprises a logic gate that generates a drive signal to control switching of the switch, and wherein the latch is coupled to disable the logic gate from providing the drive signal in response to the detection of the absence of the portion of the ac half cycle for the consecutive ac half cycles.