A power apparatus for an external load comprises a transformer, a power coordinating unit, a control unit and an internal load. The transformer is adapted for transforming an input voltage into an output voltage and an auxiliary voltage in response to an operating signal. The transformer comprises a first coil, a second coil and an auxiliary coil electromagnetically coupled to one another. The power coordinating unit comprises a first resistor, a transistor, a second resistor, a diode and a capacitor. The control unit is coupled between the first node and the first coil and configured to selectively generate the operating signal. When the control unit operates in a protective mode, the control unit is configured not to generate the operating signal, the power coordinating unit is configured to generate a coordinating current supplied to the internal load by using a starting voltage of the first node.