Applying FPGA Control with ADC-Free Sampling to Multi-Output Forward Converter

In this paper, a forward converter with multiple outputs is employed to build up a circuit system with full-digital control without any analog-to-digital (ADC) converter adopted. In this circuit, all the output voltages can be regulated by individual feedback control loops. As transient load variations due to the main output happens, the secondary outputs are affected quite slightly. Furthermore, the output voltage with the largest output current adopts not only the voltage mode control but also the interleaved control and current sharing control. Therefore, if this circuit system adopts full-digital control, the number of ADCs employed is relatively large, and the corresponding cost is expensive. Accordingly, the sampling of multiple output voltages and two-phase currents without any ADCs is used herein. Moreover, a nonlinear control strategy is proposed and applied to the traditional proportional-integral-derivative (PID) controller to accelerate the load transient response. In addition, the field programmable gate array (FPGA) is used as a control kernel.