Patent ID: 7084697

Claim:
A charge pump circuit comprising: an input voltage receiving terminal; a power supply terminal whose voltage is lower than that of said input voltage receiving terminal; an output terminal; a step-up capacitor having first and second terminals; a first charging switching element formed by a first transistor connected between said input voltage receiving terminal and the first terminal of said step-up capacitor; a second charging switching element connected between the second terminal of said step-up capacitor and said power supply terminal; a first discharging switching element connected between said input voltage receiving terminal and the second terminal of said step-up capacitor; a second discharging switching element formed by a second transistor connected between the first terminal of said step-up capacitor and said output terminal; a first switch circuit connected between said input voltage receiving terminal and a back gate of said first transistor and between the first terminal of said step-up capacitor and the back gate of said first transistor; a second switch circuit connected between the first terminal of said step-up capacitor and a back gate of said second transistor and between said output terminal and the back gate of said second transistor; and a logic circuit which compares a voltage at the first terminal of said step-up capacitor with an output voltage at said output terminal to control said second switch circuit in accordance with whether or not said output voltage is lower than the voltage at the first terminal of said step-up capacitor, when said first and second charging elements are turned ON.