Patent ID: 7869499

Claim:
A variable-frequency circuit with a compensation mechanism, applying to a power supply having a frequency-division mode, wherein said power supply has a feedback unit generating a feedback signal and a PWM (Pulse Width Modulation) unit outputting a working cycle signal; said feedback signal enables said PWM unit to change said working cycle signal, and the power output by the secondary side of a transformer is thus adjusted; said PWM unit generates said working cycle signals according to a reference level signal, a reference frequency signal and said feedback signal, and wherein said variable-frequency circuit with a compensation mechanism comprises: a load sensing/decision unit determining whether to output a frequency-variation signal according to said feedback signal to decide whether said variable-frequency circuit operates in a normal mode or a frequency-division mode; a frequency-division unit receiving a first clock signal, wherein in said normal mode, said frequency-division unit outputs a reference frequency signal having a frequency identical to the frequency of said first clock signal; in said frequency-division mode, said frequency-division unit divides the frequency of said first clock signal by an integer to obtain a second clock signal and then outputs a reference frequency signal having a frequency identical to the frequency of said second clock signal; and a level modulation unit outputting said reference level signal, defining a normal level for said reference level signal and including a slope generator and a compensation unit, wherein said slope generator receives said frequency-variation signal and controls said compensation unit to generate a compensation current to modulate said reference level signal and then restore said reference level signal to said normal level within a buffering interval; thus, transient-state compensation and stabilized output is achieved during frequency variation.