Dimmable offline LED driver

• US 8,680,784 B2
• Filed: 06/15/2011
• Issued: 03/25/2014
• Est. Priority Date: 06/15/2010
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Hariharan, Suresh
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): PHAM, THAI N
• Application Number:
  US13/161,278
• Publication Number:
  US 20120212134A1
• Time in Patent Office: 1,014 Days
• Field of Search: 315/200.R, 315/201, 315/209.R, 315/210, 315/246, 315/247, 315/291, 315/294, 315/297, 315/307, 315/308
• US Class Current: 315/297
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Embodiments of the present invention provide a system and method for controlling the amplitude of a current from a diode bridge into an EMI filter and LED array. Due to the manner in which certain dimmers (i.e., leading edge dimmers) operate, there is a delay on its output in transmitting a voltage when the voltage crosses zero.

Claims

1. A dimmable LED driver apparatus comprising:

an input interface coupled to a power source and dimmer, the input interface receives an input voltage from the power source and dimmer;

a sensor coupled to the power source and dimmer, the sensor detects a first voltage on the input voltage and generates a sensed voltage signal representative of a voltage drop on the input voltage caused by a dimmer;

a control loop coupled to receive the sensed voltage and compare the sensed voltage to a first threshold level and a second threshold level, the control loop generating a control signal based on a comparison of the sensed voltage to the first threshold level and the second threshold level;

a regulator and control block coupled to receive the control signal, the regulator and control block generates an LED driver signal based at least in part on the control signal; and

an output interface comprising a capacitor, the LED driver signal is provided to an LED array at the output interface.

2. The dimmable LED driver apparatus of claim 1 further comprising a diode bridge coupled between the sensor and the regulator and control block, the diode bridge converts the input voltage, which is an alternating current signal, to a direct current signal.

3. The dimmable driver apparatus of claim 2 further comprising an EMI filter, coupled between the diode bridge and the regulator and control block, the EMI filter reduces the amount of electromagnetic interference on the direct current signal generated by the diode bridge.

4. The dimmable driver apparatus of claim 1 wherein the regulator and control block comprises an offline buck LED driver.

5. The dimmable driver apparatus of claim 1 wherein the regulator and control block comprises an offline buck-boost LED driver.

6. The dimmable driver apparatus of claim 1 wherein the regulator and control comprises a flyback LED driver.

7. The dimmable driver apparatus of claim 1 wherein the sensed voltage signal is proportional to a dimming value generated by a dimmer in the power source and dimmer.

8. A dimmable LED driver apparatus comprising:

an input interface coupled to a power source and dimmer, the input interface receives an input alternating current signal from the power source and dimmer;

a diode bridge coupled to receive the input voltage, the diode bridge converts the input alternating current signal into a direct current signal;

a sensor coupled to receive the direct current signal, the sensor detects a first voltage on the direct current signal and generates a sensed voltage signal representative of a voltage drop on the direct current signal caused by a dimmer;

a control loop coupled to receive the sensed voltage and compare the sensed voltage to a first threshold level and a second threshold level, the control loop generating a control signal based on a comparison of the sensed voltage to the first threshold level and the second threshold level;

a regulator and control block coupled to receive the control signal, the regulator and control block generates an LED driver signal based at least in part on the control signal; and

an output interface comprising a capacitor, the LED driver signal is provided to an LED array at the output interface.

9. The dimmable driver apparatus of claim 8 further comprising an EMI filter, coupled between the sensor and the regulator and control block, the EMI filter reduces the amount of electromagnetic interference on the direct current signal.

10. The dimmable driver apparatus of claim 8 wherein the regulator and control block comprises an offline buck LED driver.

11. The dimmable driver apparatus of claim 8 wherein the regulator and control block comprises an offline buck-boost LED driver.

12. The dimmable driver apparatus of claim 8 wherein the regulator and control comprises a flyback LED driver.

13. The dimmable driver apparatus of claim 8 wherein the sensed voltage signal is proportional to a dimming value generated by a dimmer in the power source and dimmer.

14. A method of generating an LED driver signal representative of an offline dimming operation, the method comprising:

receiving an input signal from a power source and dimmer, the input having a voltage drop caused by a dimming operation;

sensing the voltage drop on the input signal and generating a sensed voltage signal;

comparing the sensed voltage signal to a first threshold level and a second threshold level and generating a control signal based at least in part on the comparing step;

generating a regulated LED driver signal based at least in part on the control signal and at least one characteristic of an LED array; and

providing the regulated LED driver signal to the LED array via an output interface that comprises a capacitor.

15. The method of claim 14 wherein the input signal is an alternating current signal and the sensed voltage drop is identified on the alternating current input signal.

16. The method of claim 15 wherein the alternating current input signal is converted to a direct current signal using a diode bridge.

17. The method of claim 15 further comprising the step of removing at least a portion of electromagnetic interference on the direct current signal using an EMI filter.

18. The method of claim 14 wherein the input signal is a direct current signal generated by a diode bridge that converts the an alternating current on the input signal into a direct current signal.

19. The method of claim 18 further comprising the step of removing at least a portion of electromagnetic interference on the direct current signal using an EMI filter.

20. The method of claim 14 wherein the sensed voltage signal is proportional to a dimming value generated by a dimmer in the power source and dimmer.