| Summary: | 碩士 === 義守大學 === 電機工程學系碩士在職專班 === 99 === This thesis proposes a dimmable electronic for driving a fluorescent lamp. The lamp is dimmed by controlling the conducting angle of a TRIAC. The proposed electronic ballast consists of a TRIAC, a buck-boost converter and a class-D resonant inverter which drives the fluorescent lamp at a high frequency. The buck-boost converter is operated at discontinuous current mode (DCM). It complies with the conducting angle of a TRIAC to regulate the input power, and thereby, controls the lamp power. The resonant circuit of the class D resonant inverter is designed to present inductive. Therefore, the switching losses can be effectively reduced by operating the active switches of the resonant inverter at zero-voltage switching (ZVS) on. The buck-boost converter and the class D resonant inverter share the same active switch. It helps simplify the control circuit and reduce the component count, and makes the electronic ballast have the advantage of low-product cost. Besides, dimming operation can be achieved by a TRIAC without adding any conducting wires.
The electron ballast is analyzed by using fundamental approximation based on the equivalent lamp model. Circuit operations are discussed for different operation modes according to the conducting status of the semiconductor switches. The mathematical equations are conducted and circuit parameters are designed. The circuit-simulation software IsSpice is used to verify the circuit operation. Finally, a prototype circuit for a T5-28W fluorescent lamp is built and tested. The satisfactory experimental results have verified the validity of the proposed electronic ballast.
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