運用在返馳式轉換器之切換式穩定供應電壓電路設計與實作

Abstract

在隔離型電源轉換器中，返馳式轉換器由於具有電路架構簡單、低成本、和較少的元件數目之特性，因此廣泛地使用在低功率電子產品上。在返馳式轉換器中，控制晶片的供應電壓對功率電晶體的導通損耗影響非常大。將供應電壓維持在一較低的值將會使導通損耗降低。在本論文中提出一種切換式穩定供應電壓電路架構，包含了取樣電阻、比較器、SR閂鎖器、位準平移器、以及開關元件。藉由調整電路中取樣電阻值的大小，可以決定供應電壓所欲穩住的範圍。另外，使用切換式穩定供應電壓電路架構能夠讓輔助繞組的耦合係數提高，藉此降低待機時的損耗。最後實際進行晶片製作，並量測電路結果確認此電路能達到穩定供應電壓的效果。

Among isolated power converters, flyback converters are widely used for low power electrical appliances, for its features of the simple circuit topology, low cost, and fewer components. In flyback converters, the supply voltage of control IC has the dominant influence on driving loss of power MOS. Keeping supply voltage at a low level will reduce the driving loss. A switch-mode supply voltage regulator is proposed. It can stabilize the supply voltage of control IC in flyback converter. This circuit is composed of sample resistors, comparators, SR-latch, level shifter, and switch element. Changing the value of sample resistors in this circuit can adjust the stable region of supply voltage. Besides, higher coupling coefficient of the auxiliary winding and lower standby power loss are possible by using the proposed switch-mode supply voltage regulator. Finally, an experimental circuit is implemented for verification.