The Cascade Connection of Switching Regulators

A method for the cascade connection of switching regulators is introduced which is useful for low-voltage power supplies. It is common to use a reactor with a secondary winding in order to obtain a sufficiently small step-down ratio (E out /E in ). In this method, how-ever, a switching surge occurs because of the leakage inductance of the two-winding reactor. On the other hand, by the method presented here, we will be able to have a sufficiently small step-down ratio and a sufficiently large regulation range with no occurrence of the switching surge. Furthermore, a new method is proposed for isolating the supply and the load circuit.