Patent ID: 6061259
Filing Date: 2000-05-09
Classification: H02M

Abstract:
A protected, transformerless power converter for converting mains AC power to low voltage DC, comprising:a resistor and varistor connected across input AC mains voltage, whereby the peak input voltage applied to a rectifier is limited by safely absorbing the energy of any input voltage transients appearing on the AC mains;said rectifier which receives AC input voltage from said resistor and varistor and supplies pulsating DC voltage to a pass element resistor;a controlled electronic switch connected between said pass element resistor and an output filter capacitor which selectively interrupts the current flowing into the output filter capacitor from the pass resistor;an averager electrically connected to said AC input voltage, wherein said averager extracts the average value of the AC input voltage, wherein said average value is proportional to the rms value of a sinusoidal AC input voltage;an adaptive thresholder electrically connected to said averager and to said switch, wherein said switch is controlled by said thresholder by using the instantaneous AC input voltage, said average value of the AC input voltage and the output voltage as electrical inputs to turn on the switch at a predetermined switching voltage;said output filter capacitor electrically connected to said switch and said AC current whereby said output capacitor averages the pulsed current drawn from the AC input line to provide a constant DC output voltage to a load;whereby said switch allows said pass element resistor to be electrically connected to said output filter capacitor only during the portion of the AC voltage waveform when the instantaneous AC input voltage is below a predetermined value.