Design of rectifier diode temperature compensation circuit in flyback converter

Abstract

A rectifier diode temperature compensation circuit is presented for primary-side controlled flyback converter. By compensating the variation of secondary-side rectifier diode forward voltage with temperature, the error rate of output voltage in flyback converter will be effectively improved at high temperature. The design of the circuit is based on the negative temperature characteristics of the base-emitter voltage VBE of bipolar transistors. Besides, the circuit can also provide overtemperature protection. Results of simulation based on 0.5 mm bipolar complementary metal oxide semi-conductor process show that the compensation voltage is 0.1 V at 125°C and 0 V at 25°C. The maximum output voltage error rate of flyback converter with compensation is from 3.8 to 0.6% under the temperature between 25 and 125°C. The thermal shutdown threshold is 140°C, and the over-temperature protection hysteresis threshold is 110°C.