A power controller in a switching mode power supply dynamically performs high-voltage charging to maintain an operating voltage. The power controller includes a PWM signal generator, a high-voltage charging circuit, and a high-voltage charging controller. The PWM signal generator provides a PWM signal to a power switch to perform power conversion regulating an output voltage of the switching mode power supply at a voltage rating. The high-voltage charging circuit has a high-voltage-tolerant switch connected between a line voltage and the operating voltage, wherein rectifying an AC voltage generates the line voltage. The high-voltage charging controller turns ON the high-voltage-tolerant switch to perform high-voltage charging at the same time when performing the power conversion. The high-voltage charging directs a charging current from the line voltage through the high-voltage-tolerant switch to charge the operating voltage.