返馳式轉換器為被最廣為使用的隔離型電源轉換器架構，具有電路簡單低成本的特性。本論文提出三個一次側控制返馳式轉換器控制方法。(一)為應用於行動裝置快速充電之一次側控制可變輸出電壓控制。為因應行動裝置功能日漸複雜，所使用之電池容量日益增加，因而導致充電時間過長造成使用者不便。本文所提出之可變輸出電壓控制，充電器之輸出電壓隨著充電功率增加而上升。透過分析轉換器在不同輸出電壓下之轉換損失，設計一適用於輸出額定為30瓦之輸出電壓控制方法。並透過實驗電路的量測驗證所提出之控制方法，在輸出功率0.5~30瓦之間效率皆大於71%，最高可達到84%。由於一次側控制為使用輔助繞組來量測輸出電壓訊號，所量得之電壓包括輸出二極體的順向導通電壓。因此目前一次側控制之返馳式轉換器需將操作模式限制在不連續導通模式下。(二)為提升其應用功率，提出可應用於連續導通模式和不連續導通模式之一次側控制方法。所提出之方法為量測主開關導通瞬間的初始電流值，用以補償輸出二極體壓降所造成的誤差。除此之外，所提出之方法也可應用於控制輸出電流。本方法透過實作一輸出150 W之實驗電路驗證，其輸出電壓控制誤差在0.25%以內輸出電流控制誤差在 5%以內。(三)本論文又提出一具飛輪電流開關之返馳式轉換器，應用於TRIAC調光相容的發光二極體驅動電路及控制。在使用發光二極體取代白熾燈的應用上，會遭遇無法提供TRIAC足夠之保持電流導致光源閃爍熄火的問題。所提出之方法為在返馳式轉換器中加入一飛輪電流開關並聯於返馳式轉換器磁化電感。利用控制返馳式轉換器主開關來提供足夠之保持電流，而輸出發光二極體電流則使用加入之飛輪電流開關調節。為驗證其可行性，實作一8W的發光二極體驅動電路，最小調光導通角度可小於18度，符合NEMA-SSL-6之規範。轉換效率可達86%

Flyback converter is the most used topology for isolated power converters characterized with circuit simplicity and low cost. Three primary side control schemes are proposed in this dissertation. The first control scheme proposed is a primary side regulated (PSR) adaptive output voltage control for the mobile device fast charging. The battery capacity used in mobile device become larger and larger for the multi-functions integration, and the charging time is longer which causes the usage drawback for the user. The output voltage of the charger is controlled increasing with the increasing required power to improve the charging efficiency. The analysis of the conversion losses during various output voltage conditions is derived to obtain the proposed control. The feasibility of the proposed control is verified by the built experimental prototype. The efficiency is higher than 71 % at 0.5 W~30 W output power, and the highest efficiency is 84 %. The second control proposed is PSR control for both CCM and DCM operation. Traditionally, PSR control is limited in discontinuous conduction mode (DCM) operation and the power rating is limited in low power applications. To extend the power range, the primary side control suitable for continuous conduction mode (CCM) and DCM is proposed. The voltage drop on the secondary winding and output diode at CCM operation is compensated by sensing the secondary side current at the instant when primary side switch is being turned-on. When flyback is operated at DCM, the secondary side current is zero at the voltage sensing instant. This method is also feasible for output current control. An experimental prototype with 150 W rated power is built to verify the feasibility of the proposed control. The control accuracies of output voltage and current are 0.25 % and 5%, respectively. The third is a Flyback converter with freewheeling control for TRIAC dimmable LED driver. To provide the require holding current, freewheeling switch parallel connected to the magnetizing inductance is used in flyback converter. The required TRIAC holding current is modulated by the main power switch and the LED load current is regulated by the additional freewheeling power switch. An 10 W experimental prototype is built to verify the feasibility. The minimum conduction angle achieve is 18∘ which meet the standard of NEMA-SSL-6. And the conversion efficiency is up to 86 %.
Keywords: flyback converter, primary-side control

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