Control circuit for power factor corrected electronic ballasts and power supplies

Abstract

The control circuit provides an improved method for power factor correction characteristics and low Electro Magnetic noise. This control circuit uses an Electro Magnetic Interference abatement circuit that consists of a series connected diode in one of the DC input lines from the full wave rectifier and a capacitor connected across the DC input lines from the full wave rectifier to eliminate the Electro Magnetic Interference generated by the active power factor corrections and resonant circuit operations. This is accomplished in part by the operation of the series connected diode which blocks reverse currents, thereby preventing high frequency current present in the gas discharge control circuit from flowing back to the AC input line through the full wave rectifier. In addition, the use of the capacitor across the DC input line helps to absorb high frequency current that is present on the input lines from the full wave rectifier. The cost of these two elements is small compared to the use of an inductor, yet their synergistic effect on the input lines provides a significant abatement of the Electro Magnetic Interference generated by the active power factor corrections in conjunction with resonant circuit operations for such devices as gas discharge lamp ballasts and power supplies.