| 摘要 |
A pulse-width-modulation (PWM) control system with nonlinear ramp is disclosed. A nonlinear ramp generator generates a nonlinear ramp varied with the duty (V<SUB>out</SUB>/V<SUB>in</SUB>) in a waveform signal, which could be a logarithm ramp, an exponent ramp, a multi-piecewise-linear ramp, a power ramp or a combination of above. The slope of the ramp is not a constant due to the non-linear characteristic. The voltage V<SUB>ramp </SUB>will vary with the input voltage V<SUB>in</SUB>, output voltage V<SUB>out</SUB>, and duty (V<SUB>out</SUB>/V<SUB>in</SUB>), therefore it will reduce the influence of the input voltage V<SUB>in </SUB>or output voltage Vout on the modulation gain and loop gain, even to keep the modulation gain and loop gain in constant value. As mentioned-above, the present invention improves the transient response of system, the sensitivity for variation of V<SUB>in </SUB>and V<SUB>out</SUB>, thus it is capable of correcting the output voltage quickly, for supplying a more steady power output.
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