High-Efficiency Switching Regulator using Sub Class E Switching Mode

A high efficiency switching dc-to-dc converter is presented, which operates at about 100 kHz with an ordinary bipolar transistor. A new converter is based on the buck converter. By positively taking advantage of the switching transistor output capacitance and the transformer leakage inductance, it is possible to realize little switching loss. When the "off" state transient response reaches zero voltage across the switching transistor, before the beginning of the "on" state, it does so with approximately zero slope. To maintain the above-mentioned operation mode, it is necessary that Ton/T of the transistor, primary inductance Lp, leakage inductance Le and the sum of the transistor output capacitance and the external capacitance are strictly selected by numerical analysis. An example is given of the new converter design to deliver a continuous power of 100 W at about 100 kHz with an overall system efficiency greater than 90 percent into a variable load. Further, unwanted noise is not produced.