| Summary: | 碩士 === 長庚大學 === 電子工程研究所 === 94 === Abstract
This paper presents a multi-lamp driving system for Cold Cathode Fluorescent Lamp (CCFL).
The proposed multi-lamp driving system adopts a push-pull inverter with series resonant
parallel loads to drive four CCFLs. Besides, a uniform current control circuit that
ensures uniform brightness of the four series CCFLs is proposed in the system. The uniform
current control circuit is achieved with an inverter sharing a common choke to drive
a series of two lamps. Since there exists a relationship between the current of lamp and the
brightness, as a result, not only the uniform current is achieved when all the lamps
illuminate but also which is achieved when light modulation proceeds. The error rate
of the voltage and current of each lamp is reduced in the range of 0.4%. Light modulation
is achieved by using the technique of soft start and soft finish of a PWM controller IC to
reduce unnecessary pulses generated during the very short time of lamp start and finish
so that system efficiency is enhanced. A complete protection circuit is built inside the system
and if CCFLs cannot be started in 1.5 seconds, the lamps will be protected by cutting of
the power switches immediately. The life-span of CCFLs is increased by the protection circuit
and technique of soft start. Experimental results show that the prototype revels low power
consumption, low cost, uniform lighting, and high protection in voltage and current demand.
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