| 摘要 |
PROBLEM TO BE SOLVED: To provide time ratio control method and circuit of PWM signal arranged to limit the on time ratio with high accuracy. SOLUTION: The time ratio control circuit section of a DC-DC converter comprises an error amplifier 11 generating an error output signal Vfb, a comparator 12 for comparing the error output signal Vfb with a triangular wave signal Vosc1 of a specified period to generate a PWM signal Vpwm1, a triangular wave oscillation circuit 13 generating the triangular wave signal Vosc1 of a given period and a first pulse signal Vosc2 synchronous with the triangular wave signal Vosc1, a delay circuit 14 generating a second pulse signal Vd with a given delay time td behind the first pulse signal Vosc2, a logic circuit 15 for releasing forced turn-off of the PWM signal Vpwm1 by a second pulse signal Vd, and an output buffer 16. COPYRIGHT: (C)2005,JPO&NCIPI
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