Patent ID: 6639367
Filing Date: 2003-10-28
Classification: H05B

Abstract:
A control circuit for a piezo transformer based power supply, comprising:oscillator circuitry operative to establish an operating frequency as a function of an oscillator control signal; drive circuitry operative to generate a switching control signal at the operating frequency for a primary circuit of the piezo transformer; sense circuitry operative to generate a feedback signal indicative of an operational parameter of the power supply, the operational parameter being sensitive to frequency-dependent gain of the piezo transformer; and feedback circuitry operative in response to the feedback signal to vary the oscillator control signal in a manner tending to regulate the operational parameter to a predetermined value, the feedback circuitry including initialization circuitry operative (i) during an initialization phase, to establish an initial value of the oscillator control signal corresponding to an initial operating frequency, and (ii) thereafter to permit the feedback circuitry to gradually drive the oscillator control signal to a normal operating value, such that the operating frequency is swept from the initial operating frequency to a normal operating frequency.