Power supply with resonant inverter circuit using variable frequency control for regulation

Claim 1

A switching power supply circuit comprising: input means for receiving a first alternating current (AC) signal; first rectifying and filtering means coupled to said input means for providing a first direct current (DC) signal in response to said first AC signal; inverter means generating minimal radio frequency interference (RFI) coupled to said first rectifying and filtering means for providing a second AC signal having a substantially sinusoidal waveform in response to the first DC signal and to an inverter control signal, said inverter consisting of a pair of SCR's alternately triggered and negatively biased; inverter control means coupled to said inverter means for providing said inverter control signal and for varying the frequency of said inverter control signal in response to an indication of a desired power output from said inverter, said inverter control means further comprising: a first comparator means for providing a first comparison signal in response to a comparison of a DC output signal with a preselected reference signal; an oscillator coupled to said first comparator means for providing an oscillator output signal in response to said first comparison signal; a differentiator means coupled to said oscillator for simultaneously providing a negative differentiated pulse to one and a positive differentiated pulse to the other of said pair of SCR's via a transformer in response to said oscillator output signal; and means for providing said inverter control signal in response to said oscillator output signal; and second means coupled to said inverter means for providing said DC output signal in response to said second AC signal.