Capacitor coupled converter

Abstract

The capacitor coupled converter (CCC) is a DC-DC converter which produce a DC source as the output. It has two input terminals for connection to a DC voltage source, two output terminals for connection to a load, and a plurality of circuit control terminals for receiving a plurality of control waveforms. The basic elements of the CCC are two switches connected in series across the input terminals. An inductor in series with a transformer is connected to the junction of the two switches. Two capacitors with parallel diodes are connected across the input DC voltage source. The junction between the two capacitors is connected to one of the primary terminal of the transformer. The secondary terminals of the transformer is connected to an AC-DC converter, typically two diodes which rectify the AC to DC. The DC is then filtered by an inductor-capacitor filter. During operation, the two switches periodically and alternately open and close. The two capacitors across the input terminals are charged and discharged alternately by a current through the primary circuit. Triangular waveform is produced across the transformer which transfer power to the output. The power output is limited inherently by the charging process. The CCC also enables zero voltage switching. A switch is closed only when a near-zero voltage exists across the switch. In order to bring about this result, a diode and capacitor are connected in parallel with each switch. When one switch opens, the other switch closes usually when there is less than 0.7 volts across the switch. The time period during which the voltage across the switch to be closed is less than 0.7 volts is a function of the resonant frequency of the capacitance associated with the switch to be closed and the inductance associated with the primary circuit. Zero voltage switching reduce loss associated with the switches.