Adapter power supply

An adapter power supply, comprising:

• an AC/DC converter for converting an AC power into a DC power;
• a DC/DC converter including a transformer having a primary terminal and a secondary terminal for converting a link voltage of the DC power into an output power;
• and
• a controller for estimating a load current of the output power through a primary current of the transformer and varying the link voltage of the DC power according to variation of the estimated load current,
• wherein the controller includes:
• a first coupler for outputting a difference between an output voltage of the output power and a reference output voltage;
• a gain controller connected to the first coupler;
• an Opto coupler connected to the gain controller;
• a current sensor for sensing the primary current;
• a variation controller connected to the current sensor for outputting an output voltage control signal and a link voltage control signal;
• a second coupler for coupling a control signal passing the Opto coupler with the output voltage control signal;
• an integral controller connected to the second coupler;
• a frequency modulator connected to the integral controller for controlling switching of the DC/DC converter;
• a third coupler for coupling the link voltage control signal with a difference between the link voltage of the DC power and a reference link voltage;
• a gain/integral controller connected to the third coupler;
• and
• a pulse width modulator connected to the gain/integral controller for controlling switching of the AC/DC converter.