Voltage and current-mode control for a multiphase bi-directional DC-DC converter

This paper describes a completely digitally controlled bidirectional multi-phase dc-dc converter capable to operate in buck-and boost mode. All necessary tasks are performed within a FPGA circuitry. The voltage and current mode control is based on a voltage to frequency converter (u/f), also called voltage control oscillator (VCO), performing measurements of input/output-voltages and inductor-currents, respectively. This measurement principle uses digital counters (digital integrators) in order to obtain the average values of the output-voltages and inductor-currents. In analogue current-mode control the instantaneous current-value-measurement is used for the switching action. In case of using VCO measurement principle the digital equivalents of average values of input/output voltages and all measured currents will appear in the counter, which is the part of FPGA unit. All other tasks, like control algorithm and pulse width modulation, were also implemented within the FPGA. This approach enabled programmability and configurability of the control tasks. The proposed approach was verified experimentally.