| 摘要 |
PROBLEM TO BE SOLVED: To provide a charge pump power supply circuit and its drive method capable of reducing noise that is generated in an output voltage when its operation mode is shifted from a step-up mode to a step-down mode or from the step-down mode to the step-up mode. SOLUTION: When an input voltage V<SB>in</SB>shifts from a state of being higher than an output voltage V<SB>o</SB>to a state of being lower than it, a first edge signal S<SB>E1</SB>is supplied from a mode change-over circuit 6a to a control circuit 5a to perform a first transition preparatory operation that switches transistors Q1, Q2 on and transistors Q3, Q4 off during a prescribed period of time. Conversely, when the input voltage V<SB>in</SB>shifts from a state of being lower than the output voltage V<SB>o</SB>to a state of being higher than it, a second edge signal S<SB>E2</SB>is supplied from a mode switching circuit 6a to a control circuit 5a to perform a second transition preparatory operation that switches transistors Q1, Q3 on and transistors Q2, Q4 off during a prescribed period of time. COPYRIGHT: (C)2005,JPO&NCIPI
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