DC/DC converter including a zener diode having a substantially zero temperature coefficient

摘要

A DC/DC converter has a transformer having a primary winding (N P ), a secondary winding (N S ), and an auxiliary winding (N B ), a switching transistor (Q1) connected in series to the primary winding, a control transistor (Q2) for turning the switching transistor on or off, and a feedback control circuit connected to the control transistor and the auxiliary winding. The feedback control circuit includes a Zener diode (D5) having a substantially zero temperature coefficient. The Zener diode (D5) has a Zener voltage which lies in a range between 5 volts and 6 volts. In order to cancel a temperature characteristic of the control transistor (Q1), the temperature coefficient of the Zener diode (D5) is selected.