Primary side control circuit and method for ultra-low idle power operation

th th A method and circuit for reducing power consumption during idle mode to ultra-low levels, such as about 1/10to 1/1000or less of active power is disclosed. An ultra-low idle power supply comprises a primary circuit, a secondary circuit and a control circuit. The control circuit monitors behavior of the primary circuit and determines whether an idle state or no load condition exists, and if so the primary circuit is disengaged. By disengaging the primary circuit, the power consumption of the ultra-low idle power supply is reduced to ultra-low levels.