TABLE OF CONTENTS Chapter 9 of Wu [2] shows that power switching devices encounter severe electrical stresses, consume significant power, and generate heat that must be properly displaced. Excessive electrical stresses in the form of repetitive voltages or currents and heat, as well, eventually shorten the operating life of those devices. Figure 9.10 of Wu [2] indicates that the major power dissipation for those devices takes place at the switching edges, when neither the device voltage across nor the current through equals zero. This is true for both the main switch on the primary side and the rectifiers on the secondary side. It is therefore imperative to create, by some means, either a zero-voltage or zero-current state for at least one, or better both, at the time of transition.
It was also long understood that an inductor in series with a switch can slow down the time rate of current through the switch while a capacitor in parallel is capable of slowing down the rise of voltage across. This being given, the first question is where to incorporate both components and the second is what value to use. In 1983, both questions were answered by a device (patent 4,415,959). We examine the circuit revealed in the patent in the next section.
Sometimes, one feels that nature seems deceptively simple. This sentiment also holds for the answer to the section's question. In Figure 8.1, a capacitor, C r, in parallel with a diode and the leakage inductance
