GATE THRESHOLD TEMPERATURE COMPENSATION CIRCUIT FOR MOSFET FOR SWITCHING POWER SOURCE

摘要

PROBLEM TO BE SOLVED: To keep stable operation though the threshold voltage of a MOSFET being the main semiconductor element of a switching power source varies with temperature. SOLUTION: Between the gate of the MOSFET 1 and a resistor 17, series diodes 21 and 22 having temperature characteristic is inserted and a PTC resistance element 18 having a positive temperature coefficient is inserted via a transistor 23 to form the charging circuit of a capacitor 7 with the element 18 and a resistor 8. When a temperature is raised, forward voltage is lowered by the temperature characteristic of the diodes 21 and 22 to reduce the charging current of the capacitor 7 to compensate the temperature.