An AC-to-DC converter furnishing a regulated DC-output voltage from an AC-input supply voltage which is converted with a rectifier that utilizes, in at least two of its legs, IGBT (insulated gate bipolar transistor) devices, preferably of the kind that have no internal diodes. Also included in the converter of this convention is circuitry which tracks zero-crossing events relative to AC-input voltage for the purpose of establishing switching signals and times for such signals for operating the IGBT devices, and wherein thorough-safe operation is associated with malfunctioning of the zero-crossing tracking subcircuitry whereby a failure in that circuitry will result effectively in a shut down of the entire converter, and a bleed down to zero of DC-output voltage.
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