Low line harmonic AC to DC power supply

A low line current harmonic power supply, adapted to receive power from an AC line, including a predetermined number of phase pairs, wherein the power supply comprises:

• a capacitor disposed in parallel across the output of the power supply;
• means for generating indicia of the phase of each phase pair of the AC line;
• and, for each phase pair:
• a rectifier responsive to the AC line voltage on the phase pair;
• an energy transformation circuit connected between the rectifier for the phase pair and the capacitor;
• a power switch, responsive to a control signal applied thereto, for selectively energizing the energy transformation circuit;
• a control circuit, responsive to the indicia of the desired waveform for the phase pair, for generating the control signal to the power switch, the control circuit including:
• a pulse width modulator, responsive to a modulation control signal applied thereto for generating the control signal to the power switch;
• a first error signal generator for generating an output voltage error signal indicative of the deviation of the output voltage of the power supply from a predetermined reference voltage;
• a second error signal generator for generating a phase pair RMS error signal indicative of the deviation of RMS voltage of the phase pair of the AC line from a predetermined reference value;
• synthesizing mean, phase-locked to the voltage waveform of the phase pair of the AC line, for synthesizing indicia of a desired input current waveform reference;
• a multiplier, responsive to the indicia of the desired waveform, the output voltage error signal, and the phase pair RMS error signal;
• a current sensor for generating a signal indicative of the current from the rectifier;
• and
• a differencing amplifier, receptive of the outputs of the current
• sensor and the multiplier, for generating the modulation control signal.

A method of producing a substantially constant output voltage from an AC line without producing substantial line harmonics, comprising the steps of:

• rectifying the voltage across the AC line;
• applying the rectified voltage to an energy transformation circuit;
• applying the output of the energy transformation circuit to an output voltage capacitor;
• and
• controlling the energization of the energy transformation circuit in accordance with a synthesized waveform phase-locked to the voltage waveform of the AC line to draw input current sinusoidally in phase with input voltage by:
• generating a first error signal indicative of the deviation of the output voltage from a predetermined reference voltage;
• generating an RMS error signal indicative of the deviation of the RMS voltage of the voltage waveform of the AC line from a predetermined value;
• combining the synthesized waveform, the first error signal, and the RMS error signal, to generate a multiplier output signal;
• generating a current sense signal indicative of the current from the rectifier:
• comparing the multiplier output signal to the current sense signal to generate a difference output signal;
• and
• modulating the energy of the energy transformation circuit in accordance with the difference output signal.

A method of producing a substantially constant output voltage from a predetermined number of phase pairs without producing substantial line harmonics, comprising the steps of:

• rectifying the voltage across each phase pair;
• applying the rectified voltages from each phase pair to a respective energy transformation circuit associated with the phase pair;
• applying the output of each energy transformation circuit to a common output voltage capacitor;
• and
• controlling the energization of the energy transformation circuit associated with each phase pair in accordance with a synthesized waveform phase-locked to the phase pair to draw input current sinusoidally in phase with the input voltage by:
• generating a first error signal indicative of the deviation of the output voltage from a predetermined reference voltage;
• generating an RMS error signal indicative of the deviation of the RMS voltage of the voltage waveform of the associated phase pair from a predetermined value;
• combining the synthesized waveform, the first error signal, and the RMS error signal, to generate a multiplier output signal;
• generating a current sense signal indicative of the current from the rectifier;
• comparing the multiplier output signal to the current sense signal to generate a difference output signal;
• and
• modulating the energy of the energy transformation circuit in accordance with the difference output signal.