| 摘要 |
PROBLEM TO BE SOLVED: To stabilize a switching frequency in a power unit. SOLUTION: A first comparator 21 compares a feedback voltage Va with the first reference voltage VREF1, and generates a signal Vc1 according to the comparison result. A second comparator 22 compares the feedback voltage Va with the second reference voltage VREF2, and generates a signal Vc2 according to the comparison result. A control signal generating circuit 24 generates a control signal fsw, in answer to the signals Vc1 and Vc2. A converting circuit 26 generates a voltage Vfd according to a difference (frequency difference) between the frequency of the control signal fsw and the frequency of the reference signal fo. A reference voltage generating circuit 23 changes the potential of the first reference voltage VREF1 and the second reference voltage VREF2 according to the frequency difference voltage Vfd output from the converting circuit 26. COPYRIGHT: (C)2011,JPO&INPIT
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