Circuit for ac adapter to reduce power drawn from an ac power source

A circuit, comprising:

• a rectifier bridge for rectifying an AC voltage from an AC power supply;
• a conversion circuit coupled to the rectifier bridge for converting the rectified AC voltage to a DC voltage;
• and
• an opto-coupler coupled to the conversion circuit for monitoring an output connection of the circuit, wherein when a system is not coupled to the output connection, the opto-coupler substantially prevents the AC voltage from being drawn from the AC power supply, wherein the opto-coupler comprises:
• a diode coupled to the output connection, and
• a transistor coupled to the diode and the conversion circuit.

A circuit, comprising:

• a rectifier bridge for rectifying an AC voltage from an AC power supply;
• a conversion circuit coupled to the rectifier bridge for converting the rectified AC voltage to a DC voltage, wherein the conversion circuit comprises:
• an electrolyte capacitor coupled to the rectifier bridge,
• a PWM coupled in parallel to the electrolyte capacitor,
• a transformer comprising a primary winding and a secondary winding,
• a switching transistor, wherein a gate of the switching transistor is coupled to the PWM and a drain of the switching transistor is coupled to the transformer,
• a first diode coupled in series to the secondary winding of the transformer, and
• a filter capacitor coupled in series to the first diode, coupled in parallel to the secondary winding of the transformer, and coupled to an output connection of the circuit;
• and
• an opto-coupler coupled to the conversion circuit for monitoring the output connection, wherein the opto-coupler comprises:
• a third diode coupled to the output connection, and
• a transistor coupled to the third diode and the PWM,
• wherein when a system is not coupled to the output connection, the third diode is not shorted and the transistor is turned on,
• wherein when the transistor is turned on, the conversion circuit is substantially prevented from drawing the AC voltage from the AC power supply.