An operating method for a light-emitting diode (LED) power supply includes the following operations: controlling an output voltage to be a first voltage by a control circuit; detecting a load current by a detection circuit; maintaining the output voltage as the first voltage by a constant voltage control circuit when the load current is greater than zero, changing the output voltage from the first voltage to a second voltage by the control circuit when the load current is equal to zero, and the second voltage being greater than the first voltage.