Single-stage power factor corrected capacitor charger

Method of charging a storage capacitor comprising:

• providing a full-wave rectified waveform, through switches, to a primary winding of a transformer;
• connecting a secondary winding of the transformer, through a bridge rectifier comprising four output rectifiers, at least one of which is a switch, to the storage capacitor;
• providing an inductor in series with the primary winding of the transformer;
• sensing whether there is input voltage available sufficient to drive current through the inductor and the transformer primary;
• if there is input voltage available sufficient to drive current through the inductor and the transformer primary, operating the bridge rectifier as a bridge converter;
• if there is not input voltage available sufficient to drive current through the inductor and the transformer primary, switching the at least one output rectifier into a conducting state thus effectively shorting the secondary winding of the transformer and storing energy in the inductor.

Method of charging a capacitor, comprising:

• providing a full wave bridge converter having an first bridge rectifier receiving an input voltage and providing a full-wave rectified waveform on a power line and a return line, the full wave bridge converter comprising providing four switches, one of which is connected to the power line, one of which is connected to a storage capacitor and two of which are connected to the return line and further comprising a transformer having a primary winding selectively connected to the power and return lines by the four switches;
• characterized by:
• providing an inductor in series with the primary winding;
• sensing current flowing through the inductor and primary winding:
• when the input voltage is adequate, and a first threshold current is sensed, operating the full wave bridge converter in a normal manner;
• when the input voltage is insufficient to cause the current to reach the first threshold before a first predetermined timeout period, causing a next portion of the cycle to initiate and, providing that the current at the end of the first timeout period exceeds a second, lower threshold current (+imin), continuing to operate the full wave bridge converter in a normal manner;
• and
• if the current at the end of the first timeout period fails to reach the second threshold at the end of the timeout period, then reversing current in the primary winding and storing energy in the inductor.

Method of charging a capacitor, comprising:

• providing a power converter having four switches selectively connecting a full wave rectified waveform to a primary winding of a transformer;
• in a first portion of a cycle, sensing current flowing in the primary winding of the transformer;
• controlling closures of the switches based on the sensed current flowing in the primary winding of the transformer;
• and
• providing means for shorting a secondary winding of the transformer and for storing energy for driving the transformer in a subsequent portion of the cycle.