Low Energy Base Drive Using Regenerative Turn Off for Switching Regulators
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
A known base drive for a proportional drive Dual Switch (DS) experiences circuit limitations, a chief one of which is that the transformer saturates, causing excessive current to flow. A reconfiguration of the circuit solves these problems in the following manner. The known base drive is shown in Fig. 1. When transistor Q1 turns off, magnetizing current is forced to flow in windings N2 and N3. The DS turns on and proportional drive begins. As Q1 turns off, Q2 turns on and begins charging capacitor C1 toward VB . Q1 then turns on, and the voltage on C1 is applied to N1 (neglecting the drop in D2 and Q1). The DS begins to turn off, and reverse turn-off current is supplied by C1. When turn off is complete, C1 will still have a voltage present. C1 must continue to discharge, and its energy is transferred to N1 as Im .