CONTROL CIRCUIT FOR STEP-DOWN AND BOOST TYPE SWITCHING SUPPLY, STEP-DOWN AND BOOST TYPE SWITCHING SUPPLY, AND METHOD OF CONTROLLING STEP-DOWN AND BOOST TYPE SWITCHING SUPPLY

摘要

PROBLEM TO BE SOLVED: To expand a range of an input voltage capable of controlling an output voltage.

SOLUTION: A state control circuit 34 generates a mask signal Smk for controlling the ON time of a transistor 21 connected between an input terminal P1 to which an input voltage Vin is applied and an inductor 25 to a PWM control signal Spwm generated based on the output voltage Vout. Also, the state control circuit 34 generates a mode signal Smd for changing between a boost mode and a step-down mode. Then, the state control circuit 34 selectively outputs one of the mask signal Smk and the mode signal Smd according to the input voltage Vin.

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