| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 96 === In general, the closed-loop system of a DC/DC converter, connected to DC bus, is well designed with good performance and stability. However, an input EMI filter is needed between the DC/DC converter and DC bus to eliminate the high frequency noise. The noise on the DC bus is kept away from disturbing the operation of the DC/DC converter, and the switching frequency harmonics noise of the DC/DC converter is prevented from polluting the DC bus. However, the performance and stability of the closed-loop system of a DC/DC converter may be affected by an adding input EMI filter. To overcome this problem, the output impedance of the input EMI filter must comply with some design criteria.
The small-signal block diagram of a DC/DC converter for the voltage or current feedback control is derived individually in the thesis. Applying Extra Element Theorem (EET) to the block diagram, the design criteria for output impedance of input EMI filter is thereby obtained separately for voltage or current feedback control. An input EMI filter based on the design criteria is then constructed to suppress the high frequency noise.
If the input EMI filter is an lowpass circuit, a damping resistor is required to pull down the resonant peak of the output impedance to meet the design criteria. In addition, the capabilities of input EMI filter prevent noise on the DC bus from disturbing the operation of the DC/DC converter, and also prevent noise on the DC/DC converter from reducing DC bus quality. The noise suppression capabilities of the input EMI filter conform with Reciprocity Theorem.
Finally, for input and output, a prototype of the buck converter is established. Then three input EMI filters of the DC/DC converters are investigated. The effects on the performance and stability of the closed-loop system of a DC/DC converter with input EMI filter are verified by the experimental results in the presence of the variations of input voltage and load resistance.
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