DC/DC voltage converting device.

摘要

A DC/DC voltage converting device is obtained for boosting a DC power supply voltage to provide a higher output voltage,comprising soft start circuit 20 for gradually increasing the turning-on duration of transistor 34 in boosting circuit 30; pulse width control circuit 60 for providing a modulated pulse signal P2to control the boosted voltage. The device further comprises boosting circuit 30 including an inductor 32, diode 36 and transistor 34. Boosting circuit 30 provides a predetermined boosted voltage higher than the power supply voltage by alternately turning on and off transistor 34. The turning-on duration of transistor 34 is gradually increased during the initial operation period by soft start circuit 20, and is controlled by modulated pulse signal P2 during a stable operation period. The device further comprises gate circuit 40 having diode 46 and transistor 44, and step up circuit 70. Step up circuit 70 turns off transistor 44 during the initial operation period, and turns it on while transistor 34 is off during the stable operation period to allow an efficient current flow from boosting circuit 30 to output terminal 58. Any counter current flow from output terminal 58 to boosting circuit 30 is inhibited during the initial operation period.