Light modulation method and apparatus for cold cathode fluorescent lamps
AssigneeZippy Technology Corp.
InventorsChin-Wen Chou, Eddie Cheng, Kuang-Ming Wu, Chin-Biau Chung
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Abstract
A method and apparatus for modulating light of CCFLs that couples frequency alteration and pulse width modulation (PWM) approaches to change output voltage and current of a piezoelectric transformer to modulate the luminosity of a CCFL. The invention includes a PWM controller to alter operation cycle and a frequency control IC to change resonant frequency that drives the piezoelectric transformer at different operation cycles thereby to modulate the luminosity of the CCFL and improve the life span of the piezoelectric transformer.
Claims7
A method for modulating light of cold cathode fluorescent lamps (CCFLs) to module a luminosity of a CCFL by altering output voltage and output current of a piezoelectric transformer that actuate the CCEL, comprising:
- generating a pulse width modulation control signal that has different operation cycles Ton and Toff;
- and
- generating a high frequency AC signal with different frequencies f1 and f2 at the different operation cycles Ton and Toff of the pulse width modulation control signal to actuate the piezoelectrie transformer to alter the output voltage and the output current of the piezoelectric transformer thereby to module the luminosity of the CCFL;
- the piezoelectric transformer generates a first voltage gain at the frequency f1 of the operation cycle Ton and generates a secondvoltage gain at the frequency f2 of the operation cycle Toff, the first voltage gain being greater than the second voltage gain.
An apparatus for modulating light of cold cathode fluorescent lamps (CCFLs), comprising:
- a power supply unit to provide DC power required to actuate a CCFL;
- a pulse width modulation (PWM) control unit generating a pulse signal through a pulse width modulation technique to control the power supply unit to output a PWM control signal that has different operation cycles Ton and Toff;
- a resonant frequency control unit modulating the PWM control signal to become a high frequency AC signal which includes different frequencies f1 and f2 at the different operation cycles Ton and Toff;
- and
- a piezoelectric transformer boosting gain of the high frequency AC signal to become a high output voltage and a high output current to actuate the CCFL to generate light;
- the high frequency AC signal drives the piezoelectric transformer to generate different voltage gains at the different frequencies f1 and f2 of the different operation cycles Ton and Toff.
Dependencies are inferred from the claim text.