Patent ID: 7129679
Filing Date: 2006-10-31
Classification: H02M,H05B,Y02B,Y10S

Abstract:
1. A voltage booster type switching power supply circuit for boosting an input voltage supplied from a DC power source by means of PWM (Pulse Width Modulation) method so as to supply a predetermined output voltage to a load, comprising: a coil having one end thereof connected to one end of the DC power source; a rectifying element connected between other end of the coil and one end of the load; an output current detection resistor for detecting current flowing through the load; an output capacitor, connected between a node at which the rectifying element and the load are connected together and ground, for producing the output voltage across both ends thereof by being electrically charged; a switching element connected between the other end of the coil and ground; a drive circuit for stabilizing the output voltage by controlling the switching element by means of a first PWM method in accordance with a voltage appearing across the output current detection resistor; a start/stop circuit for receiving an external input signal controlled by means of a second PWM method and regulating an amount of the output current by starting and stopping the drive circuit according to the external input signal fed externally thereto; and a soft-start circuit for receiving the external input signal, controlling the drive circuit so as to increase the output voltage gradually by becoming operative when the external input signal becomes active in a first period thereof after startup, and controlling the drive circuit so as to increase the output voltage promptly by becoming inoperative when the external input signal becomes active in a second period thereof and thereafter after startup.