Systems and methods of applying bleed circuits in LED lamps
View Patent ↗A bleed circuit is applied to a transformer based on a bleed-on time and a bleed-off time determined by monitoring an output voltage waveform of the transformer.
1. A method of operating an LED system including an electronic transformer, the method comprising:
monitoring an output voltage waveform of the transformer;
starting a bleed-on timing cycle upon sensing a first voltage-waveform condition and ending the bleed-on timing cycle after the determined bleed-on time has elapsed;
starting a bleed-off timing cycle upon sensing a second voltage-waveform condition different from the first voltage-waveform condition, and ending the bleed-off timing cycle after the determined bleed-off time has elapsed; and
engaging a bleed circuit to the transformer based on a state of the bleed-on timing cycle and disengaging the bleed circuit from the transformer based on a state of the bleed-off timing cycle, the bleed circuit being engaged for a duration adequate to ensure a minimum load on the transformer sufficient to avoid cut-off throughout the output voltage waveform,
wherein the bleed-on timing cycle starts when a trailing edge of the output voltage waveform falls below a predetermined threshold and ends when a subsequent trailing edge of the output voltage waveform falls below a predetermined minimum threshold.
2. The method of claim 1 , wherein the state of the bleed-on timing cycle is a start thereof and the state of the bleed-off timing cycle is an end thereof.
3. A method of operating an LED system including an electronic transformer, the method comprising:
monitoring an output voltage waveform of the transformer;
starting a bleed-on timing cycle upon sensing a first voltage-waveform condition and ending the bleed-on timing cycle after the determined bleed-on time has elapsed;
starting a bleed-off timing cycle upon sensing a second voltage-waveform condition different from the first voltage-waveform condition, and ending the bleed-off timing cycle after the determined bleed-off time has elapsed; and
engaging a bleed circuit to the transformer based on a state of the bleed-on timing cycle and disengaging the bleed circuit from the transformer based on a state of the bleed-off timing cycle, the bleed circuit being engaged for a duration adequate to ensure a minimum load on the transformer sufficient to avoid cut-off throughout the output voltage waveform,
wherein the bleed-off timing cycle starts when a leading edge of the output voltage waveform begins to rise and ends when the leading edge of the output voltage waveform exceeds a predetermined maximum threshold.
4. The method of claim 1 , further comprising, for a current bleed-on timing cycle:
starting the current bleed-on timing cycle upon sensing that the trailing edge of the output voltage waveform falls below the predetermined threshold;
determining a time interval since the trailing edge of the output voltage waveform previously fell below the predetermined threshold; and
ending the current bleed-on timing cycle after the time interval has elapsed.
5. The method of claim 3 , further comprising:
(i) for an initial bleed-off timing cycle:
starting the bleed-off timing cycle upon sensing that the leading edge of the output voltage waveform has begun to rise;
ending the bleed-off timing cycle upon sensing that the leading edge of the output voltage waveform exceeds the predetermined maximum threshold; and
determining a time interval between the starting and ending of the bleed-off timing cycle; and
(ii) for a subsequent bleed-off timing cycle:
starting the bleed-off timing cycle upon sensing that the leading edge of the output voltage waveform has begun to rise; and
ending the bleed-off timing cycle after the time interval has elapsed.
6. The method of claim 4 , further comprising, for a plurality of subsequent bleed-on timing cycles, omitting the determining step and ending a subsequent bleed-on timing cycle after the time interval has elapsed.
7. The method of claim 5 , further comprising repeating step (ii) for a plurality of subsequent bleed-off timing cycles.
8. The method of claim 1 , wherein the bleed-on and bleed-off timing cycles are determined based on a period of the output voltage waveform.
9. The method of claim 8 , wherein the bleed-on timing cycle and the bleed-off timing cycle are adjusted until the period of the monitored output voltage waveform is equivalent to a predetermined period of the output voltage waveform generated by the transformer.
10. A system for minimizing flicker in a circuit comprising an LED lamp and an electronic transformer, the system comprising:
a bleed circuit;
an analyzer for monitoring an output voltage waveform of the transformer and determining a bleed-on timing cycle and a bleed-off timing cycle based at least in part on the monitored output voltage waveform;
a memory for storing a duration of the bleed-on timing cycle and a duration of the bleed-off timing cycle; and
control circuitry for engaging the bleed circuit to the transformer during only a portion of a period of the output voltage waveform and based at least in part on the stored durations, the bleed circuit ensuring a minimum load on the transformer sufficient to avoid cut-off.
11. The system of claim 10 , wherein the bleed circuit comprises at least one of a resistor or a transistor.
12. The system of claim 10 , wherein the analyzer is configured to start a bleed-on timing cycle when a trailing edge of the output voltage waveform falls below a predetermined threshold and to end the bleed-on timing cycle when a subsequent trailing edge of the output voltage waveform falls below a predetermined minimum threshold.
13. The system of claim 12 , wherein the analyzer is configured to start a bleed-off timing cycle when a leading edge of the output voltage waveform begins to rise and to end the bleed-off timing cycle when the leading edge of the output voltage waveform exceeds a predetermined maximum threshold.
14. The system of claim 13 , wherein the control circuit is configured to engage the bleed circuit at a start of a bleed-on timing cycle and to disengage the bleed circuit at an end of a bleed-off timing cycle.
15. The method of claim 3 , wherein the state of the bleed-on timing cycle is a start thereof and the state of the bleed-off timing cycle is an end thereof.
16. The method of claim 3 , wherein the bleed-on and bleed-off timing cycles are determined based on a period of the output voltage waveform.
17. The method of claim 16 , wherein the bleed-on timing cycle and the bleed-off timing cycle are adjusted until the period of the monitored output voltage waveform is equivalent to a predetermined period of the output voltage waveform generated by the transformer.