Patent ID: 7075803

Claim:
A circuit to significantly reduce the frequency variation of a self-oscillating pulse width modulator which comprises an integrator, a hysteretic comparator and a feedback path from said hysteretic comparator's output to said integrator's input, comprising: means to generate one or more signals representing a measure of the pulse frequency of said self-oscillating pulse width modulator; means for an alternating mechanism; means for a feedback summing point, allowing to shift the threshold reference voltage of said hysteretic comparator; means for a frequency to threshold correction value generator, implemented in a first additional feedback loop, connecting said hysteretic comparator's output signal to said means to generating one or more signals representing a measure of the pulse frequency and connecting the resulting signal to said means for an alternating mechanism; and means for a correction value selector, implemented in a second additional feedback loop, connecting said hysteretic comparator's output signal to said means for an alternating mechanism, to control the selection of one of two values of said signals representing a measure of the pulse frequency, depending on the actual status of said hysteretic comparator's output and connecting the resulting combined signal to said feedback summing point.