Controlling the Light Output of One or More LEDs In Response to the Output of a Dimmer

• US 20120299511A1
• Filed: 05/24/2012
• Published: 11/29/2012
• Est. Priority Date: 05/26/2011
• Status: Active Grant

• Current Assignee: Dongguan EMEI Components Limited, Emei (HK) Components Limited
• Original Assignee: Charles J. Montante
• Inventors: Montante, Charles J., Trzyna, William
• Granted Patent: US 8,963,444 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light

Abstract

An apparatus for controlling the brightness of one or more light emitting diodes includes a sensing circuit to sense a dimming level of a dimmer. A microprocessor receives from the sensing circuit a signal indicative of the dimming level, and a drive circuit drives the one or more light emitting diodes. The microprocessor is arranged to generate a PWM waveform or current level corresponding to the dimming level and to provide the PWM waveform or current level to the drive circuit.

Claims

1. An apparatus for controlling the brightness of one or more light emitting diodes, the apparatus comprising:

a sensing circuit to sense a dimming level of a dimmer, wherein the sensing circuit includes a capacitive element to integrate a waveform based on the dimmer output;

a circuit to provide a signal to the microprocessor indicative of whether the dimmer is conducting;

a drive circuit to drive the one or more light emitting diodes;

a snubber circuit to absorb energy generated by ringing of an inductive element in the dimmer;

a power factor correction circuit for coupling between an output of the dimmer and the drive circuit,

a microprocessor to receive from the sensing circuit a signal indicative of the dimming level, wherein the microprocessor is arranged to generate a PWM waveform and to provide the PWM waveform to the drive circuit,

wherein the microprocessor is further arranged to control whether the snubber circuit is on or off based on the signal indicative of whether the dimmer is conducting, and

wherein the microprocessor is arranged to receive a signal from the power factor correction circuit indicative of whether the power factor correction circuit is on or off, wherein, if the signal from the power factor correction circuit indicates that the power factor correction circuit is on, the microprocessor generates a PWM waveform having a duty cycle in accordance with the signal from the sensing circuit indicative of the dimming level and provides the PWM waveform to the drive circuit, and wherein, if the signal from the power factor correction circuit indicates that the power factor correction circuit is off, the microprocessor generates the PWM waveform having the same duty cycle as just prior to receiving the signal indicating that the power factor correction circuit is off.

2. The apparatus of claim 1 wherein the microprocessor is arranged to generate first and second PWM waveforms based on the signal indicative of the dimming level and to provide the PWM waveforms to the drive circuit to drive respective groups of light emitting diodes, and

wherein the first PWM waveform has a first duty cycle and the second PWM waveform has a second duty cycle, and wherein a ratio of the first duty cycle to the second duty cycle is in accordance with pre-established criteria.

3. An apparatus for controlling the brightness of one or more light emitting diodes, the apparatus comprising:

a sensing circuit to sense a dimming level of a dimmer, wherein the sensing circuit includes a capacitive element that charges when an output of the dimmer is non-zero;

a microprocessor to receive from the sensing circuit a signal indicative of the dimming level; and

a drive circuit to drive the one or more light emitting diodes,

wherein the microprocessor is arranged to generate a PWM waveform or current level corresponding to the dimming level and to provide the PWM waveform or current level to the drive circuit.

4. The apparatus of claim 3 wherein the capacitive element integrates a waveform based on the dimmer output.

5. The apparatus of claim 3 wherein the sensing circuit includes a resistor divider network, wherein the capacitive element is in parallel with a portion of the resistor divider network.

6. The apparatus of claim 3 wherein the microprocessor includes a look-up table, the microprocessor arranged to look up settings for the PWM waveform or the current level based on a voltage level across the capacitive element.

7. The apparatus of claim 3 wherein the microprocessor is arranged to determine settings for the PWM waveform or the current level based on a voltage level across the capacitive element.

8. An apparatus for controlling the brightness of one or more light emitting diodes, the apparatus comprising:

a sensing circuit to sense a dimming level of a dimmer;

a microprocessor to receive from the sensing circuit a signal indicative of the dimming level; and

a drive circuit to drive the one or more light emitting diodes,

wherein the microprocessor is arranged to generate a PWM waveform or current level corresponding to the dimming level and to provide the PWM waveform or current level to the drive circuit,

the apparatus further including a snubber circuit to absorb energy generated by ringing of an inductive element in the dimmer.

9. The apparatus of claim 8 further including a circuit to provide a signal to the microprocessor indicative of a state of the dimmer, wherein the microprocessor is arranged to control whether the snubber circuit is on or off based on the signal indicative of the state of the dimmer.

10. The apparatus of claim 9 wherein the snubber circuit includes a capacitive element in series with a resistive element.

11. The apparatus of claim 10 wherein the snubber circuit includes a transistor in series with the capacitive element and resistive element, wherein the transistor has a gate that receives a signal from the microprocessor to control a state of the transistor.

12. The apparatus of claim 9 wherein the circuit to provide a signal indicative of the state of the dimmer rectifies an output signal from the dimmer and converts the rectified signal into a square wave signal that is positive when the dimmer is on, wherein the square wave signal is provided to the microprocessor.

13. The apparatus of claim 12 wherein the microprocessor is arranged to cause the snubber circuit to turn on before the start of each half cycle of the square wave and to extend to a specified amount time after the dimmer turns on.

14. An apparatus for controlling the brightness of one or more light emitting diodes, the apparatus comprising:

a sensing circuit to sense a dimming level of a dimmer;

a microprocessor to receive from the sensing circuit a signal indicative of the dimming level;

a drive circuit to drive the one or more light emitting diodes; and

a power factor correction circuit coupled between an output of the dimmer and the drive circuit,

wherein the microprocessor receives a signal from the power factor correction circuit indicative of whether the power factor correction circuit is on or off,

wherein, if the signal from the power factor correction circuit indicates that the power factor correction circuit is on, the microprocessor generates a PWM waveform having a duty cycle that is based on the signal from the sensing circuit indicative of the dimming level and provides the PWM waveform to the drive circuit, and

wherein, if the signal from the power factor correction circuit indicates that the power factor correction circuit is off, the microprocessor maintains the duty cycle of the PWM waveform as previously generated.

15. The apparatus of claim 14 wherein the sensing circuit includes a capacitive element that integrates a waveform based on the dimmer output.

16. The apparatus of claim 14 wherein the microprocessor includes a look-up table, the microprocessor arranged to look up settings for the PWM waveform based on a voltage level across the capacitive element.

17. The apparatus of claim 14 wherein the microprocessor is arranged to determine settings for the PWM waveform based on a voltage level across the capacitive element.

18. An apparatus for controlling the brightness of multiple groups of light emitting diodes, the apparatus comprising:

a sensing circuit to sense a dimming level of a dimmer, wherein the sensing circuit includes a capacitive element that charges when an output of the dimmer is non-zero;

a microprocessor to receive from the sensing circuit a signal indicative of the dimming level; and

a drive circuit to drive the one or more light emitting diodes,

wherein the microprocessor is arranged to generate first and second PWM waveforms based on the signal indicative of the dimming level and to provide the PWM waveforms to the drive circuit to drive respective groups of light emitting diodes,

wherein the first PWM waveform has a first duty cycle and the second PWM waveform has a second duty cycle, and wherein a ratio of the first duty cycle to the second duty cycle is in accordance with one or more input signals received by the microprocessor.

19. The apparatus of claim 18 wherein the ratio of the first duty cycle to the second duty cycle is adjustable upward or downward in fixed increments.

20. The apparatus of claim 18 wherein the microprocessor is arranged such that a pulse applied to an input pin causes the ratio of the first and second duty cycles to increase or decrease by a predetermined amount.

21. The apparatus of claim 20 wherein the ratio of the first and second duty cycles is user-configurable.

22. A method of controlling the brightness of one or more light emitting diodes, the method comprising:

sensing a dimming level of a dimmer, wherein the sensing includes integrating a waveform based on the dimmer output;

generating a PWM waveform or current level based on the dimming level; and

providing the PWM waveform or current level to a drive circuit that drives the one or more light emitting diodes.