Abstract: An electronic ballast includes a series resonant inductor and capacitor and a filament winding magnetically coupled to said inductor. The filament winding forms a closed circuit with a filament in a gas discharge lamp, wherein the current induced in the winding opposes a portion of the current through the inductor to reduce the net voltage on the filament during normal lamp operation. In accordance with another aspect of the invention, the filament winding is reversely wound with the inductor on a common core to reverse the phase of the current induced in the filament winding from the current through the inductor.

Abstract: A standby power supply system (SPS) is connected to supply power to a load by way of a transfer switch, to replace power from the AC lines, when the AC line fails to provide sufficient voltage to operate the load (e.g., 85% of nominal RMS voltage usually 120 VAC-RMS). The SPS has an inverter which switches voltage from a battery to generate AC power when the line fails. The inverter is controlled by varying the width of switching pulses in order to regulate the AC output voltage and compensate for reductions in battery voltage as the battery discharges. The AC output voltage is also synchronized with the line voltage when the line voltage returns (increases to greater than 85% of nominal value) so that on switch over back to the AC line, the AC waveform applied to the load does not change substantially before and after switch over.

Abstract: An inverter power supply system (DC input, AC output) with a bridge type power stage having switching devices (transistors) in each arm is used to create an AC output voltage across the bridge center terminals. The transistors execute numerous switching cycles per period to create an output waveform that has a low frequency AC component together with a high frequency AC component that is removed via a low pass filter. Unless some means is provided to prevent it, a DC component is usually present at the output of the inverter as well. This DC component will cause saturation in transformer coupled loads with attendant excessive inverter device currents unless means are provided to limit or eliminate the DC component of the output voltage.