| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 103 === This thesis mainly designs a power supply converter for the dimmable LED lighting system. Based on the two-stage design, it takes boost power factor correction (PFC) circuit in boundary conduction mode as the front stage voltage stabilizer and quasi resonant flyback converter as the rear stage to reduce switching loss and improve conversion efficiency.
At present, the requirement of universal voltage results in high DC bus voltage in the design of power supply, which makes the PFC generating more switching loss in low voltage input. Therefore, the active power factor correction circuit in the front stage developed in this thesis has the function of adjusting output voltage. That is to say, lower PFC output voltage in low voltage input can reduce the switching loss in the front stage. On the other hand, when the demand for output power decreases, the switching loss of the PFC will result in poor light load efficiency. Therefore, in this thesis, the PFC function is shut down when it is in light load to improve the overall efficiency. In addition, the rear stage adopts quasi resonant flyback converter featured in switching of voltage valley, which can reduce the switching loss and the noise effectively with the advantages of simple topology framework and low cost.
This thesis also develops an RGB LED color-mixing circuit as the load of the LED drive. In order to verify the design of LED drive circuit with changing load, it utilizes a microcontroller to transmit dimming data to an RGB color-mixing IC through SPI communication to adjust the RGB LED luminance. Moreover, the simulation software SIMetrix / SIMPLIS is utilized to establish the IC model of LED drive and to simulate the circuit behavior for circuit analysis. Finally, an LED power supply converter with input power of 100W and active power factor adjustment is manufactured with AC input range 90Vac-264Vac, highest power factor 0.99, and light load efficiency 88%.
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