SOFT START CIRCUIT AND SWITCHING DC-DC CONVERTER EQUIPPED WITH THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a soft start circuit which reduces overshoot of output voltage at start-up and slowly raises the output voltage, in a switching DC-DC converter.;SOLUTION: The soft start circuit 10 controls a duty period of an output transistor 13 by comparing the voltage Vs by a capacitor 1 for soft start and a split resistor 2 for soft start with the reference voltage Vref that becomes equal to the voltage Vr by a divided resistor 3 for detecting output voltage when the output voltage Vout is set voltage Vt, until the output voltage Vout of the switching DC-DC converter 20 reaches the set voltage Vt. Then, when the output voltage Vout reaches the set voltage Vt, the voltage Vs becomes lower than the voltage Vr, and the soft start circuit controls the duty period of the output transistor 13 by comparing the voltage Vr with the reference voltage Vref.;COPYRIGHT: (C)2009,JPO&INPIT