| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 103 === As for power supplies, the specifications of universal input range and dual-outputs are generally appealing to user’s conveniences. In order to achieve the purposes of multiple-outputs and good output voltage regulation, several design approaches can be adopted. The power circuit proposed in this thesis assigns a main output with feedback control to obtain a stable output voltage; while the other outputs is coupled together with cascaded transformer windings to acquire the regulated voltage output.
In addition to the dual-output arrangement, this thesis proposers a variable-frequency control flyback converter. Its control IC is able to adapt its operating frequency according to different load conditions. And the circuit can be operated under discontinuous conduction mode (DCM) or continuous conduction mode (CCM). When the converter is operated at light load, the switching frequency gets lower. The low frequency operation reduces the switching loss. Contrarily, as the load gets heavier, the switching frequency becomes higher and the inductor current turns into CCM. While the flyback converter operates at CCM, the peak inductor current is lower and the conduction loss is smaller, too. The application of frequency-adaption control and toggling operation between DCM and CCM absorbs the advantages and excludes the disadvantages of these two operation modes. These all comes to a result that the flyback converter has a better efficiency with wide input voltage range.
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