A new duty cycle parallel control method and FPGA implementation for AC-DC converters with power factor correction (PFC)
A new duty cycle parallel control method for AC-DC converter with power factor correction is proposed. The duty cycle required to achieve unity power factor consists of two terms: current term and voltage term. They are calculated directly based on the reference current and sensed inductor current, input voltage and output voltage. It requires only one multiplication and three addition operations for digital implementation so that the proposed PFC control method can be implemented by a low cost DSP, microprocessor, FPGA or an ASIC to achieve high switching frequency. This duty cycle parallel control essentially distinguishes from the conventional current mode control in which there are two regulators, one for voltage regulation and one for current regulation. Test results for a digital PFC implementation show that the proposed method can achieve unity power factor under both steady and transient state. Sinusoidal input current can be achieved under nonsinusoidal input voltage condition. The switching frequency of FPGA control boost PFC is 400 kHz. The proposed duty cycle parallel control strategy has high potential for the next generation of high switching frequency PFC implementation, due to its lower calculation requirement, lower cost and better performance than average current mode control