A power supply apparatus is provided, and which includes a power conversion circuit, a control chip with soft-start function and a short protection circuit. The power conversion circuit is configured to provide a DC output voltage to a load in response to an output pulse-width-modulation (PWM) signal. The control chip is operated under a DC input voltage, and configured to generate the output PWM signal to control the operation of the power conversion circuit. The short protection circuit is configured to pull-down the level of a soft-start pin of the control chip, so as to substantially/significantly reduce the frequency and duty cycle of the output PWM signal, and then substantially/significantly reduce the current flowing through the shorted load.