Patent ID: 8773869
Filing Date: 2014-07-08
Classification: H02M

Abstract:
1. An apparatus for converting high voltage alternating current (AC) power input to a low voltage direct current (DC) power output, comprising: a first rectifier to receive a high voltage AC line power input and to output a full wave rectified waveform; an electronically actuated switch coupled to receive the full wave rectified waveform and provide a voltage-modulated pulse output in response to a gating signal; an input voltage detector to provide an input voltage signal corresponding to a voltage of the AC power input; a threshold voltage generator connected to receive the low voltage DC power output and provide a threshold voltage signal that varies in proportion to the low voltage DC power output; a voltage comparator to compare the input voltage signal to the threshold voltage signal and to provide a control signal when the input voltage signal is below the threshold voltage; a pulse generator to generate the gating signal at a predetermined frequency in response to the control signal; a transformer having a primary coil coupled to the switch to receive the voltage-modulated pulse output and a secondary coil coupled with a second rectifier that provides the DC power output; and a filter capacitor to smooth the DC power output, whereby the apparatus is to provide the low voltage DC power output using the transformer, and the filter capacitor has voltage ratings less than a voltage peak of the AC power input by only gating power though the switch to the transformer and the filter capacitor when the AC power input voltage is below a predetermined value.