| 摘要 |
PROBLEM TO BE SOLVED: To provide a PWM utilization type voltage regulator, capable of changing a back (step-down) mode and a boost (step-up) mode stably as a single-chip product. SOLUTION: The PWM utilization type voltage regulator operates in the back mode or boost one, according to whether an input voltage is higher or lower than the desired adjusted output voltage. The PWM utilization type voltage regulator uses two saw-tooth voltages, having a phase difference of 180°mutually. A point where the two saw-tooth voltages cross is a back-mode/boost-mode transition level. An error voltage, corresponding to a duty cycle required for generating an adjusted voltage, is compared with the two saw-tooth voltages. Transition from one mode to the other occurs at a point, where the error voltage crosses the back-mode/boost-mode transition level. A PWM pulse is supplied to the back switching transistor or a boost switching transistor at a voltage regulator power stage from a logic circuit, according to whether the error voltage is higher or lower than the back-mode/boost-mode transition level, and voltage-adjusted output is generated. COPYRIGHT: (C)2008,JPO&INPIT
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