| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 94 === Based on the LFR model, the harmonics balance and TL-model methods are proposed in the work to derive the dc values, voltage ripples, and phase angle shift of the output voltage. By virtue of the LFR model and system block diagrams, we can derive the DC operating point and the small-signal model of the basic AC/DC converters under the operation of the DCM mode. Rather than the averaged state equations, the dynamic behaviors of a converter can be well established. It is the main contribution of this thesis.
In addition, by means of graft scheme, the buck-boost power converter and improved wide range diagonal half-bridge flyback power converter are combined to create a novel single-stage high power factor correction (HPFC) diagonal half-bridge flyback converter. The novel single-stage HPFC converter proposed in this thesis has inherent gift of power factor correction (PFC), when the buck-boost converter in the first stage is operating in DCM mode. Hence the PFC controller is not necessary to be designed.
In addition to PFC, the output voltage regulation and the bulk capacitor voltage invariance with the load variations must be considered. It reveals from the circuit analysis and averaged state equations that the high bulk capacitor voltage stress of the novel single-stage HPFC converter is avoided while the power converter is operating in DCM+DCM mode. The proposed converter (DCM+DCM) exhibits high power factor , low voltage stress of the bulk capacitor, and the output voltage regulation.
With the operating in DCM+DCM mode of the power converter, the LFR model of the novel single-stage HPFC converter is established. By virtue of the TL-model method on the LFR model, we can analyze the dc values, voltage ripples, and phase angle shift for the bulk capacitor and output voltages. Moreover, component values of the converter are well designed according to the conditions of the proposed converter operation.
A prototype of power converter with output voltage 48 V and power 100 W is built to test the theoretical analysis. It is successfully validated by IsSpice software simulations and experimental results.
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