Input-voltage balancing of series-connected converters

A method of input-voltage balancing of converters that have inputs connected in series and outputs in parallel is described. The proposed method maintains balance of input voltages by using the voltage-control loop of one converter to regulate the output voltage and by using the voltage-control loop in the remaining converters to regulate their respective input voltages. In addition, to improve the output-voltage transient response during load changes, a simple high-pass filter is employed to couple output voltage changes into the input-voltage regulation loops. Because the converters have the same input and output voltages, they deliver the same amount of power and, therefore, carry the same amount of current without a need for a current sharing circuit. The performance of the proposed method was evaluated on a 1.2-kW prototype circuit that was designed to operate from an 800-V dc input and deliver a 12-V output.