自振直流變壓器式的轉換器是一極具經濟效益之電路架構，且具有理想直流變壓器的特性，即無漣波量之輸入與輸出電流特性。但並不具備負載調節能力，且其自振頻率會隨負載的變動而改變。本論文提出一新型自振推挽式(self-oscillating push-pull)電源轉換器。用兩個線圈取代Royer自振電路之主變壓器來提供額外的自由度，以解決自振式直流變壓器(DC transformer)之負載調節問題。
　　新型自振推挽式電源轉換器具有可飽和線圈之「自振昇壓衍生(boost-derived)型」直流對直流轉換器，以改變變壓器間的控制電流達到負載穩壓能力。轉換器使用一具脈寬調變(pulse-width modulation)與再生功能的控制廻路，操作在最佳責任週期(duty cycle)下，以完成具低漣波輸入輸出電流之理想直流變壓器。此電路在不同負載下，其自振頻率幾乎保持不變。功率晶體上的電壓波形接近方波(quasi-square)，切換時的湧入電流與開關應力皆受到抑制。且在寛廣的負載範圍內，開關的導通與截止具零電壓切換(zero-voltage switching)。本論文採用一輸入48V、輸出12V 100瓦，其操作頻率在100kHz時，效率可達86%雛型電路，以印證所提之新型電路架構的可行性及正確性。
　　若以氧鐵芯(ferrite core)取代可飽和鐵芯，則自振昇壓衍生型直流對直流轉換器電路，將成為一具E類特徵之新型「電流饋入型自振推挽式E類」反用換流器。此架構將具合併晶體上的寄生電容到共振廻路，與零電壓切換之E類特性，且具原自振推挽式電源轉換器的開路、短路保護能力。由雛型系統結果顯示由無載到滿載在無控制電流下，電路的操作頻率變動率在10%以內。
　　文中亦應用「電流饋入型自振推挽式E類」提出其延伸電路，利用射頻扼流圈的激磁電感與功率晶體的並聯電容形成共振槽，成為一新型「電壓饋入型自振推挽式E類」轉換器，以進一步的簡化電路架構。此延伸電路包括直流對交流之反用換流器、具直流變壓器特性之直流對直流轉換器，以及低輸入電壓漣波之交錯型直流對交流與直流對直流轉換器。隔離型之直流對交流反用換流器與同步整流亦將加以介紹。實驗結果顯示，直流對交流之反用換流器操作頻率在1MHz下效率可達97.5%，證明此電路之優異特性。

　　This dissertation proposes novel high-performance, self-oscillating push-pull power converters. The operation of the proposed converter is similar to that of a DC transformer; it provides both input and output currents as pure, ripple-free DC quantities. Conventionally, the self-oscillating DC transformer (SODT) type of scheme can be implemented in a very cost-effective manner. However, the structure of an SODT-type converter does not provide regulation, and its oscillating frequency changes in accordance with the load. The proposed topology of this dissertation uses two cores, which replace Royer’s main transformer to offer additional degrees of freedom, thus overcoming the output-regulation problem of the SODT-type converter.
　　The proposed self-oscillating, boost-derived (SOBD) DC-DC converter with saturable cores (SCs) will allow output-voltage regulation to be accomplished by varying only the control current between the transformers, as occurs in a pulse-width modulation (PWM) converter. A control network that combines PWM schemes with a regenerative function is used for this converter. The optimum duty cycle is implemented to achieve low levels of input- and output-current ripples, which are characteristic of an ideal DC transformer. The oscillating frequency will spontaneously be kept near-constant, regardless of the load, without adding any auxiliary or compensation circuits. The typical voltage waveforms of the transistors are found to be close to quasi-square. The switching surges are well suppressed, and the voltage stress of the component is well clamped. The switch turns on and off with zero-voltage switching (ZVS), and its resonant transitions can occur over a wide range of load current levels. A prototype circuit of an SOBD converter shows 86% efficiency at 48V input, with 12V, 100W output, and presents an operating frequency of 100 kHz.
　　Replacing SCs with ferrite cores, a novel current-fed self-oscillating push-pull (CF-SOPP) Class-E inverter is proposed, which has some features of the self-oscillation and Class-E schemes. This proposed topology can be implemented in a very cost-effective manner and has Class-E features, such as incorporating the transistor’s parasitic capacitance into the resonant circuit and an allowance for ZVS operation. The self-oscillating inverter is inherently immune to short- and open-circuiting. From no-load to full-load conditions, and without the use of a control current, the measured operating-frequency variation of the proposed inverter was less than 10%.
　　Furthermore, a novel voltage-fed self-oscillating push-pull (VF-SOPP) Class-E converter is presented and its experimental results are described. This family includes the basic VF-SOPP Class-E inverter and some of its extended VF-SOPP Class-E topologies. The input and output currents of the proposed VF-SOPP DC-DC converter remain almost constant as a DC transformer, and both the power switches and the rectifier diodes achieve ZVS. In the interleaved-type converters, the ripple-cancellation of input- and/or output-current ripples among the voltage-fed Class-E cells yields several benefits, including low ripple amplitude and high ripple frequency in the aggregate input and output waveforms. A prototype of the proposed basic inverter shows 97.5% efficiency at 48V input, with 110 Vrms, 25W output, and an operating frequency of 1 MHz.

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