| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage regulator, having both features of a linear voltage regulator which generates a smooth and quick response output voltage and features of highly efficient switching type voltage regulator. SOLUTION: The pulse frequency modulation (PFM) voltage regulator converts an unregulated input voltage to a regulated output voltage, by using a first transistor controlled by a pulse control circuit and a second transistor controlled by a linear voltage regulator circuit. When the regulated output voltage falls to a predetermined minimum target voltage level, the linear voltage regulator circuit controls the second transistor so as to maintain the regulated output voltage at the minimum target voltage level. The pulse control circuit detects the current flowing through the second transistor, generates a pulse with a predetermined duration to maintain the first transistor in a complete on state, in response to the current, and refreshes the regulated output voltage to a maximum target voltage level. When a pulse signal ends, the regulated output voltage falls toward the predetermined minimum target voltage level. COPYRIGHT: (C)2007,JPO&INPIT
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