Inductor Current Step Control With Input Voltage Feedforward for Fast Load Transient of Energy Recycling DC Electronic Load

Electronic load requires high input current slew rate for the dynamic test. An inductor current step (ICS) control (nonlinear control) cooperating with input voltage feedforward (linear control) during the transient is proposed to realize fast input current step response. The ICS control pushes the inductor current and the duty cycle to the target quiescent point within minimum time. Starting from the target quiescent point, the linear control with input voltage feedforward takes over. The advantage of proposed control is that the ICS control is able to break the low bandwidth in discontinuous conduction mode current loop, improving the input current slew rate. The input voltage feedforward can compensate the input capacitance current diversion, further improving the input current transient response. Compared with the conventional linear control, the maximum slew is increased from 32.9 to 699 A/ms, the settling time is decreased from 1.42 ms to 236 μ s, increased by 21.2 times and decreased by six times respectively, when the input current steps from 1 to 24 A at 200-V input voltage in a 5-kW prototype.