BOOST DC/DC CONVERTER AND LOGIC CONTROLLING CIRCUIT THEREOF

摘要

A boost DC/DC converter and a logic controlling circuit thereof. The logic controlling circuit (300) is used to regulate pulse width modulation (PWM) signals of the boost DC/DC converter. The logic controlling circuit includes a judging circuit (320) for judging whether the PWM signals reach a maximal duty cycle; a counting circuit (340) for counting the times that the PWM signals reach the maximal duty cycle and sending out regulating signals when the times that the PWM signals reach the maximal duty cycle continually have reached a preset value; and a controlling circuit (360) for regulating the PWM signal in one cycle to a minimal duty cycle or zero according to the regulating signals. In this way, it can help to soft start the boost DC/DC converter effectively, avoid an overshoot input current and an overshoot output voltage, and achieve a normal operating state as quickly as possible.