ADAPTIVE HOLDING CURRENT CONTROL FOR LED DIMMER

• US 20140159616A1
• Filed: 12/08/2013
• Published: 06/12/2014
• Est. Priority Date: 12/10/2012
• Status: Active Grant

• Current Assignee: Dialog Semiconductor Incorporated (Renesas Electronics Corporation)
• Original Assignee: iWatt, Inc. (Renesas Electronics Corporation)
• Inventors: WANG, XIAOYAN, ZHANG, CHENGLONG, FENG, GUANG, KNOLL, CLARITA, WANG, CHUANYANG, CHEN, JIANG, YAN, LIANG, WONG, DICKSON T.
• Granted Patent: US 9,288,864 B2
• Time in Patent Office: Days
• 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 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers

Abstract

A TRIAC dimmer controller for an LED lamp dynamically adjusts the amount of additional current supplied to the TRIAC dimmer based on the TRIAC dimmer operating mode. A TRIAC dimmer current controller continually senses the TRIAC dimmer current loading and determines a TRIAC dimmer operating mode based on the detected current. The TRIAC dimmer controller compares the detected current with a threshold current value called a TRIAC holding current, and adjusts the amount of bleeder current based on the difference between the detected current and the threshold current value. By continually sensing the TRIAC dimmer current loading, the LED controller regulates the amount of bleeder current supplied to the TRIAC dimmer using a single sink current path to satisfy the TRIAC dimmer current demands of multiple TRIAC dimmer operating modes.

Claims

1. A light emitting diode (LED) controller comprising:

a current sensor coupled to a dimmer, the current sensor configured to detect a dimmer current;

a current controller coupled to an output of the current sensor, current controller configured to;

determine a dimmer operating mode by comparing the detected dimmer current to a threshold dimmer current value, and

generate a control signal for regulating the dimmer current based on the detected dimmer current and the determined dimmer operating mode; and

a switch coupled to the current controller, the switch configured to receive the control signal and regulate an amount of additional dimmer current to be supplied to the dimmer through an additional current path based on the control signal, the amount of additional current supplied to the dimmer based on a difference between the threshold dimmer current value and the detected dimmer input current.

2. The LED controller of claim 1, wherein the current controller adjusts a duty cycle of the control signal based on the determined dimmer operating mode to regulate the amount of additional dimmer input current to be supplied to the dimmer through the additional current path.

3. The LED controller of claim 2, wherein during a first dimmer operating mode, the current controller adjusts the duty cycle of the control signal between a range of one hundred percent and forty percent based on the difference between the detected dimmer current and the threshold dimmer current.

4. The LED controller of claim 2, wherein during a second dimmer operating mode, the current controller adjusts the duty cycle of the control signal between a range from forty percent to zero percent based on the difference between the detected dimmer current and the threshold dimmer current.

5. The LED controller of claim 1, wherein the threshold dimmer current value is based on a value of the dimmer current when the dimmer stops conducting after being triggered.

6. The LED controller of claim 1, wherein the threshold dimmer current value is based on a value of a programmable circuit element, the value of the programmable element being accessible by the LED controller.

7. The LED controller of claim 6, wherein the programmable circuit element comprises a resistive circuit element.

8. The LED controller of claim 1, wherein the additional current is equal to the difference between the threshold dimmer current value and the detected dimmer input current.

9. A method of controlling dimming of an LED lamp, the method comprising:

detecting by a current sensor a dimmer current;

determining a dimmer operating mode by comparing a detected dimmer current to a threshold dimmer current value;

generating a control signal to regulate the dimmer current based on the detected dimmer current and the determined dimmer operating mode; and

regulating an amount of additional dimmer current to be supplied to the dimmer through an additional current path based on the control signal, the amount of additional current supplied to the dimmer through the additional current path based on a difference between the threshold dimmer current value and the detected dimmer input current.

10. The method of claim 9, further comprising adjusting a duty cycle of the control signal based on the determined dimmer operating mode to regulate the amount of additional dimmer input current to be supplied to the dimmer through the additional current path.

11. The method of claim 9, further comprising, during a first dimmer operating mode, modifying the control signal by adjusting the duty cycle of the control signal between a range of one hundred percent and forty percent based on the difference between the detected dimmer current and the threshold dimmer current.

12. The method of claim 11, further comprising, during the first dimmer operating mode, regulating the amount of additional dimmer current to be supplied to the dimmer through the additional current path based on the modified control signal.

13. The method of claim 12, further comprising, generating the modified control signal to turn on and to turn off a switch to regulate the amount of additional dimmer current to be supplied to the dimmer through the additional current path based on the modified control signal.

14. The method of claim 9, further comprising, during a second dimmer operating mode, modifying the control signal by adjusting the duty cycle of the control signal between a range from forty percent to zero percent based on the difference between the detected dimmer current and the threshold dimmer current.

15. The method of claim 14, further comprising, during the second dimmer operating mode, regulating the amount of additional dimmer current to be supplied to the dimmer through the additional current path based on the modified control signal.

16. The method of claim 15, further comprising generating the modified control signal to turn on and to turn off a switch to regulate the amount of additional dimmer current to be supplied to the dimmer through the additional current path based on the modified control signal.

17. The method of claim 9, further comprising:

determining a value of the dimmer current when the dimmer stops conducting after being triggered; and

modifying the threshold dimmer current based on the determined value of the dimmer current when the dimmer stops conducting after being triggered.

18. The method of claim 9, wherein the threshold dimmer current value is based on a value of a programmable circuit element, the value of the programmable element being accessible by the LED controller.

19. The method of claim 18, wherein the programmable circuit element comprises a resistive circuit element.

20. The method of claim 9, wherein detecting the dimmer current comprise sensing the dimmer current at a specified interval.