Resonant inverter having crest factor control

An arrangement comprising:

• rectifier means operative to connect with the AC voltage on an ordinary electric utility power line and to provide a DC supply voltage at a pair of DC terminals, the magnitude of the DC supply voltage varying synchronously with the instantaneous absolute magnitude of the AC voltage;
• inverter means connected with the DC terminals and operative to convert the DC supply voltage to a squarewave voltage having an instantaneous absolute magnitude proportional to that of the DC supply voltage and being provided at a squarewave output, the inverter means having control input means and being operative in response to a control signal provided thereto to change the frequency of the squarewave voltage;
• frequency-responsive circuit means connected with the squarewave output and operative to provide a substantially sinusoidal voltage at a pair of output terminals;
• load means connected with the output terminals and operative to receive a load current therefrom, the magnitude of the load current being a function of the magnitude of the DC supply voltage as well as of the frequency of the squarewave voltage;
• and
• sensor means responsive to the instantaneous magnitude of the DC supply voltage and operative to provide said control signal, thereby to effect adjustment of the frequency of the squarewave voltage such that the magnitude of the load current remains relatively constant irrespective of the variations in the magnitude of the DC supply voltage.

An arrangement comprising:

• a source having control input means and being operative to provide an AC voltage across a pair of AC terminals, the magnitude of the AC voltage exhibiting periodic variations, the frequency of the AC voltage being adjustable above a certain base frequency in response to a control signal received at the control input means;
• a series-combination of an inductor and a capacitor connected across the AC terminals, the series-combination being resonant at or near the base frequency and having a pair of output terminals effectively parallel-connected with the capacitor;
• load means connected with the output terminals and operative to receive a load current therefrom, the magnitude of the load current being a function of the magnitude as well as the frequency of the AC voltage;
• and
• sensor means responsive to the magnitude of the AC voltage and operative to provide said control signal, thereby to effect adjustment of the frequency of the AC voltage such that the magnitude of the load current remains relatively constant irrespective of the periodic variations in the magnitude of the AC voltage.