Method and apparatus for detecting presence of dimmer and controlling power delivered to solid state lighting load

• US 10,015,860 B2
• Filed: 03/29/2011
• Issued: 07/03/2018
• Est. Priority Date: 04/14/2010
• Status: Expired due to Fees

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Inventors: Datta, Michael, Campbell, Gregory
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Chan, Wei
• Application Number:
  US13/639,880
• Publication Number:
  US 20130193866A1
• Time in Patent Office: 2,653 Days
• Field of Search: 315291, 315224, 315247, 315209, 323320
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A system and method control an amount of power delivered by a power converter (220) to a solid state lighting load (240). It is determined whether a dimmer (204) is present between a voltage source (201) and the power converter (220) based on a rectified input voltage from the voltage source. When the dimmer is determined to be present, an operating point of the power converter is adjusted to increase the amount of power delivered by the power converter to the solid state lighting load by a compensation amount, so that the increased amount of power is equal to an amount of power delivered by the power converter when the dimmer is not present.

Claims

1. A method of controlling an amount of power delivered by a power converter to a solid state lighting load, the method comprising:

determining whether a dimmer is present between a voltage source and the power converter based on a rectified input voltage from the voltage source, wherein the determining includes;

obtaining, from a digital input coupled to a capacitor that is coupled to the rectified input voltage, a plurality of digital samples during a predetermined time interval,

incrementing a counter for each of the plurality of digital samples that has a predetermined level,

identifying a value of the counter at the end of the predetermined time interval as a detected phase angle of the rectified input voltage, and

comparing the detected phase angle to a predetermined threshold, wherein the dimmer is determined to be present when the detected phase angle is less than the predetermined threshold, and the dimmer is determined to be absent when the detected phase angle is not less than the predetermined threshold; and

when the dimmer is determined to be present, adjusting an operating point of the power converter to increase the amount of power delivered by the power converter to the solid state lighting load by a compensation amount, so that the increased amount of power is equal to an amount of power delivered by the power converter when the dimmer is not present.

2. The method of claim 1, wherein the step of adjusting the operating point of the power converter comprises setting a power control signal to a predetermined adjusted value corresponding to the increased amount of power to be delivered by the power converter, wherein the adjusted value comprises a pulse width modulation (PWM) signal having a first duty cycle.

3. The method of claim 1, further comprising maintaining a nominal operating point of the power converter when the dimmer is determined not to be present.

4. The method of claim 3, wherein the step of maintaining the operating point of the power converter comprises:

setting the power control signal to a predetermined nominal value corresponding to the amount of power to be delivered by the power converter when the dimmer is not present.

5. The method of claim 4, wherein the nominal value comprises a PWM signal having a second duty cycle.

6. A system for controlling power delivered to a solid state lighting load, the system comprising:

a power converter configured to deliver a predetermined nominal power to the solid state light load in response to a rectified input voltage originating from voltage mains; and

a dimmer presence detection circuit comprising;

a processor comprising a digital input;

a first diode connected between the digital input and the voltage mains;

a second diode connected between the digital input and ground;

a first capacitor connected between the digital input and a detection node;

a second capacitor connected between the detection node and ground; and

a resistance connected between the detection node and a rectified voltage node, which receives the rectified input voltage;

wherein the processor is configured to sample digital pulses at the digital input based on the rectified input voltage and to detect a phase angle based on lengths of the sampled digital pulses;

wherein the dimmer presence detection circuit is configured to determine whether a dimmer is connected between the voltage mains and the power converter, to generate a power control signal having a first value when the dimmer is present and having a second value when the dimmer is not present, and to provide the power control signal to the power converter, wherein the dimmer presence detection circuit determines whether the dimmer is connected by detecting the phase angle, comparing the detected phase angle with a predetermined threshold, and determining that the dimmer is present when the detected phase angle is less than the threshold;

wherein the power converter increases output power by a compensation amount in response to the first value of the power control signal, the increased output power being equal to the nominal power.

7. The system of claim 6, wherein the power converter does not increase the output power in response to the second value of the power control signal, the output power being equal to the nominal power.

8. The system of claim 7, wherein the first value of the power control signal comprises a pulse width modulation (PWM) signal having a first duty cycle, and the second value of the power control signal comprises a PWM signal having a second duty cycle different from the first duty cycle.

9. The system of claim 8, wherein the first duty cycle comprises a 100 percent duty cycle, and the second duty cycle comprises a 0 percent duty cycle.

10. The system of claim 6, wherein the first capacitor is charged though the resistance on a rising edge of a signal waveform of the rectified input voltage, and the first diode clamps the digital input pin one diode drop above the voltage mains when the first capacitor is charged, providing a digital pulse having a length corresponding to the signal waveform, and wherein the first capacitor discharges through the second capacitor on a falling edge of the signal waveform, and the second diode clamps the digital input pin one diode drop below ground when the first capacitor is discharged.

11. A method of controlling a power converter to deliver a predetermined nominal power to a light-emitting diode (LED) light source corresponding to an input voltage from voltage mains, regardless of whether a dimmer is present in a circuit between the voltage mains and the power converter, the method comprising:

detecting a phase angle based on signal waveforms of a rectified input voltage, wherein detecting the phase angle comprises;

obtaining, from a digital input coupled to a capacitor that is coupled to the rectified input voltage, a plurality of digital samples during a predetermined time interval,

incrementing a counter for each of the plurality of digital samples that has a predetermined level, and

identifying a value of the counter at the end of the predetermined time interval as the detected phase angle;

comparing the detected phase angle with a predetermined threshold;

when the detected phase angle is below the predetermined threshold, setting a power control signal to a dimmer value and providing the power control signal to the power converter, causing the power converter to increase an output power to the predetermined nominal power and to deliver the increased output power to the LED light source; and

when the detected phase angle is not below the predetermined threshold, setting the power control signal to a no dimmer value and providing the power control signal to the power converter, causing the power converter to deliver an output power to the LED light source without increasing the output power, the output power being equal to the predetermined nominal power.