A non-linear load driving circuit and a controller for controlling a conversion circuit to drive a non-linear load are provided. The controller includes a feedback unit, a pulse width control unit, and an overshoot reduction unit. The feedback unit generates a feedback signal according to a current feedback signal that represents a load current flowing through the non-linear load. The pulse width control unit generates a control signal according to the feedback signal to control a power output of the conversion circuit. The overshoot reduction unit generates an overshoot reduction signal when the load current changes from being smaller than to being greater than a predetermined value according to the current feedback signal. The pulse width control unit receives the overshoot reduction signal and reduces the duty cycle of the control signal accordingly. Thereby, stability of feedback control is improved and damage to circuit is prevented.