Light-emitting module, LED driving circuit, and LED driving method
AssigneeLextar Electronics Corporation
InventorsLiang-Ta Lin, Lei-Hsing Liu
Life of this patent
Estimating the term…
Abstract
A light-emitting diode (LED) driving circuit is configured for driving at least one group of LEDs. The LED driving circuit includes a constant current source, a pulse width modulation (PWM) element, and at least one pulse frequency modulation (PFM) element. The constant current source is configured for generating a current signal with a constant current value; the PWM element is electrically connected to the constant current source and configured for modulating the current signal to generate a PWM signal corresponding to the current signal; the PFM element is electrically connected between the PWM element and the LED and configured for modulating a frequency width of the PWM signal to generate at least one PFM signal for driving the LED.
Claims10
A light-emitting diode (LED) driving circuit configured for driving at least one group of LEDs, wherein the LED driving circuit comprises:
- a constant current source configured for generating a current signal with a constant current value;
- a pulse width modulation (PWM) element electrically connected to the constant current source and configured for modulating the current signal to generate a PWM signal corresponding to the current signal, wherein the PWM signal comprises a plurality of pulses identical in width;
- and
- at least one pulse frequency modulation (PFM) element electrically connected between the PWM element and the at least one group of LEDs and configured for modulating a frequency width of the PWM signal to generate at least one PFM signal for driving the at least one group of LEDs;
- wherein when the at least one PFM element modulates the frequency width of the PWM signal, the at least one PFM signal is changed, and light-emitting frequencies of the at least one group of LEDs are also changed.
A light-emitting module, comprising:
- plural groups of light-emitting diodes (LEDs), wherein these groups of LEDs are connected in parallel with each other;
- and
- a driving circuit configured for driving the groups of LEDs, wherein the driving circuit comprises:
- a constant current source configured for generating a current signal with a constant current value;
- a pulse width modulation (PWM) element electrically connected to the constant current source and configured for modulating the current signal to generate a PWM signal corresponding to the current signal;
- and
- a plurality of pulse frequency modulation (PFM) elements each electrically connected between the groups of LEDs and the PWM element and configured for modulating a frequency width of the PWM signal to generate a plurality of PFM signals for driving the groups of LEDs.
A method of driving a light-emitting diode (LED), comprising:
- modulating a current signal with a constant current value into a pulse width modulation (PWM) signal;
- and
- modulating the PWM signal into at least one pulse frequency modulation (PFM) signal for driving at least one group of LEDs;
- wherein the step of modulating the current signal into the PWM further comprises:
- modulating the current signal into a plurality of pulses as the PWM signal, wherein these pulses are identical in width;
- wherein when time intervals among the pulses are modulated, light-emitting frequencies of the at least one group of LEDs are changed.
Dependencies are inferred from the claim text.