| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit having a wide working voltage range by preventing breakdown of an NMOS having a gate-source voltage which varies as the input voltage varies. SOLUTION: The power supply circuit comprises a circuit generating a step-up voltage higher than an input voltage and an output voltage as a shared voltage for obtaining the gate voltage of a first N type MOSFET and a third N type MOSFET using the input voltage and the output voltage, a control circuit for turning the first N type MOSFET performing switching operation together with a second N type MOSFET and the third N type MOSFET on based on the step-up voltage, and a circuit operating when the gate-source voltage of the third N type MOSFET reaches a predetermined level depending on the magnitude of the input voltage to protect the third N type MOSFET. COPYRIGHT: (C)2006,JPO&NCIPI
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