Optimal trajectory control for LLC resonant converter for LED PWM dimming

1. A method of operating a resonant power converter, said method comprising steps of

generating a pulse waveform comprising pulses at a first frequency for controlling generation of switching signals to control application of input power to said power converter,

generating a pulse width modulated signal comprising pulses of controllable duty cycle at a second frequency, and

periodically interrupting said pulse waveform in accordance with said pulse width modulated signal

wherein said first frequency is sufficiently greater than said second frequency to form pulse bursts from said pulse waveform, each said pulse burst comprising at least three of said pulses.

2. The method as recited in claim 1 , wherein said resonant power converter is a LLC resonant power converter.

3. The method as recited in claim 2 wherein said power converter is a multi-channel, constant current power converter.

4. The method as recited in claim 1 , comprising a further step of

shortening at least one of a first pulse and a last pulse of a pulse burst.

5. The method as recited in claim 4 wherein a first pulse is shortened such that the voltage on a resonant capacitor due to said first pulse of a subsequent pulse burst increases to correspond to a full load, constant current voltage on said resonant capacitor.

6. The method as recited in claim 4 . wherein a last pulse is shortened such that the voltage on a resonant capacitor is brought to a voltage such that a first pulse of a subsequent pulse burst increases voltage on said resonant capacitor to correspond to a full load, constant current voltage on said resonant capacitor.

7. The method as recited in claim 1 , wherein said step of generating a pulse waveform is synchronized with said step of generating a pulse width modulated signal such that bursts of pulses having an integral number of pulses of equal pulse width are produced.

8. The method as recited in claim 7 , comprising a further step of

shortening at least one of a first pulse and a last pulse of a pulse burst.

9. The method as recited in claim 8 , wherein a first pulse is shortened such that the voltage on a resonant capacitor due to said first pulse of a subsequent pulse burst increases to correspond to a full load, constant current voltage on said resonant capacitor.

10. The method as recited in claim 8 , wherein a last pulse is shortened such that the voltage on a resonant capacitor is brought to a voltage such that a first pulse of a subsequent pulse burst increases voltage on said resonant capacitor to correspond to a full load, constant current voltage on said resonant capacitor.

11. The method as recited in claim 1 , wherein said step of periodically interruption said pulse waveform with said pulse width modulated signal shortens at least one of a first pulse and a last pulse of a pulse burst.

12. The method as recited in claim 11 , wherein said step of generating a pulse waveform is synchronized with said step of generating a pulse width modulated signal such that bursts of pulses having an integral number of pulses with at least one of a first pulse and a last pulse of a pulse burst is shortened such that a first pulse of a subsequent pulse burst causes a voltage/current state of the resonant power converter to coincide with a full load steady-state voltage/current trajectory.

13. The method as recited in claim 11 , wherein a first pulse is shortened such that the voltage on a resonant capacitor due to said first pulse of a subsequent pulse burst increases to correspond to a full load, constant current voltage on said resonant capacitor.

14. The method as recited in claim 11 , wherein a last pulse is shortened such that the voltage on a resonant capacitor is brought to a voltage such that a first pulse of a subsequent pulse burst increases voltage on said resonant capacitor to correspond to a full load, constant current voltage on said resonant capacitor.

15. A resonant power converter comprising

a switching circuit for connecting and disconnecting a resonant circuit and a source of power,

a waveform generator for generating a pulse waveform to control said switching circuit, and

a pulse width modulator for interrupting said pulse waveform to generate pulse bursts having at least three pulses in each pulse burst.

16. A resonant power converter circuit as recited in claim 15 , further including

means for shortening at least one of a first pulse and a last pulse of a pulse burst.

17. A resonant power converter circuit as recited in claim 16 , wherein said means for shortening at least one of a first pulse and a last pulse includes said pulse width modulator.

18. A resonant power converter circuit as recited in claim 15 , wherein said at least one of said first pulse and said last pulse is shortened such that a first pulse of a subsequent pulse burst charges a resonant capacitor to a voltage/current state that coincides with a full load steady-state voltage/current trajectory of said resonant power converter.

19. A light emitting diode array including a resonant power converter wherein said resonant power converter comprises

a switching circuit for connecting and disconnecting a resonant circuit and a source of power,

a waveform generator for generating a pulse waveform to control said switching circuit, and

a pulse width modulator for interrupting said pulse waveform to generate pulse bursts having at least three pulses in each pulse burst.

20. A light emitting diode array as recited in claim 19 , wherein said resonant power converter is a LLC resonant power converter.