Duty cycle controlled switch variable capacitor circuit

摘要

A switch controlled variable capacitor circuit that includes a capacitor having a first terminal and a second terminal; a switch connected across the first and second terminals of the capacitor; a pulse width modulator for controlling the switch to close at positive going zero crossings of a sinusoidally varying current provided to the first and second terminals, and to open at D seconds after the positive going zero crossings, wherein D is in a range of 0.25 to 0.5 times the period T of the sinusoidally varying current; and a diode connected across the first and second terminal of the capacitor for conducting the sinusoidally varying current during a portion of a negative half of each period of the sinusoidally varying current. The switch variable capacitor circuit has a capacitance that is controlled by varying D.