Adjustable AC/DC conversion topology to regulate an isolated DC load with low AC ripple

A power converter to provide a DC output signal to an anode structure in an electroplating or painting system, comprising:

• an adjustable voltage, adjustable frequency pulse width modulation (PWM) inverter to generate a first AC signal according to a desired fundamental inverter AC output frequency and a voltage reference;
• a sinewave filter, including an input to receive the first AC signal, and an output to provide a filtered AC signal;
• a multiphase isolation transformer, including a primary winding to receive the filtered AC signal, and a multiphase secondary to provide a plurality of isolated AC signals;
• a multi-pulse diode bridge rectifier, including a plurality of rectifier inputs to receive the plurality of isolated AC signals, and a rectifier output to provide a DC rectifier output signal;
• an output filter, including an input to receive the DC rectifier output signal, and an output to provide a filtered DC rectifier output signal;
• and
• a blocking diode, including an anode connected to the output of the output filter, and a cathode to provide the filtered DC rectifier output signal to a corresponding tank anode structure to promote formation of material on a workpiece travelling along a process direction between an entry end and an exit end.

A method to apply a coating to a workpiece, comprising:

• moving a workpiece through a solution in a tank along a process direction between an entry end and an exit end;
• providing a DC voltage signal to each of a plurality of tank anode structures distributed in the solution along the process direction between the entry end and the exit end of the tank to promote formation of material on the workpiece;
• and
• generating the individual DC voltage signals according to a profile defining setpoints for the individual power converter modules, including for each tank anode structure:
• generating a first AC signal at a frequency in a range of about 120 Hz to about 600 Hz using an adjustable voltage, adjustable frequency pulse width modulation (PWM) inverter according to a desired fundamental inverter AC output frequency and a voltage reference,
• filtering the first AC signal to generate a filtered AC signal using a sinewave filter,
• generating a plurality of isolated AC signals according to the filtered AC signal using a multiphase isolation transformer,
• rectifying the isolated AC signals to generate a DC rectifier output signal using a multi-pulse diode bridge rectifier,
• filtering the DC rectifier output signal to generate a filtered DC rectifier output signal using an output filter, and
• providing the filtered DC rectifier output to the tank anode structure through a blocking diode.