Voltage transformation using saturating oscillator - has field effect transistor controlled from transformer secondary winding

摘要

The efficiency and accuracy of transformers is improved by using a saturating oscillator and a FET in place of one of the two transistors normally employed. The gate of the FET (Q2) is connected through a regulating circuit (CR1, CR2, C1, R2) to the secondary winding (W3) of a transformer (T1). The bifilar wound primary (W1, W2) windings are connected thus: one to the supply terminal and one to the source-drain circuit which, in turn, controls the base of a switching transistor (Q1). A limiting resistor (R1) is included. With a voltage on the FET gate the transistor (Q1) turns off; thus reducing the secondary transformer voltage. This reduces the source-drain circuit resistance and thereby tends to turn the transistor (Q1) on and repeat the cycle.