In this thesis, zero-voltage switching DC/DC converters are proposed. In the proposed converter high efficiency can be achieved in spite of high switching frequency.
In chapter 2, a new type of dual output zero voltage switched (ZVS) DC/DC converter is proposed. One output is dependent on the effective duty ratio and the other is largely dependent on the switching frequency. Two completely regulated outputs are obtained with only one bridge circuit by combining the different configurations of secondary output. Using ZVS technique, switching loss can be reduced to quite low at several hundred kHz.
In chapter 3, A new constant frequency PWM dual converter which has fully regulated dual outputs is proposed. The proposed converter is the superposition of forward converter and flyback converter. The switches in the forward converter for synchronous rectification which are usually used to increase the efficiency when output voltage is low provide another degree of freedom in controlling the flyback converter. Thus, not only forward converter but also flyback converter can be fully regulated by constant frequency PWM control in continuous conduction mode (CCM).
In chapter 4, a new type of PWM series resonant converter is proposed. One pole of proposed converter is zero-current switched and the other is zero-voltage switched. By introducing auxiliary inductor, zero-voltage switching is possible at no load. The proposed converter is suitable for high-voltage dc/dc converter because voltage stresses of switching devices are minimized.
