High efficiency off-line linear power supply

摘要

A power supply circuit comprising a first switching transistor having a control terminal and a control terminal switching threshold and that charges current from a voltage source into a charge storage capacitor, a control circuit controlling the on/off operation of the switching transistor whereby the switching transistor is turned on when the voltage of the voltage source is below a predetermined level and turned off when the voltage of the voltage source is above the predetermined level, a control voltage supply circuit providing a control voltage to the control terminal of the switching transistor substantially in excess of the switching threshold when the voltage of the voltage source is below the predetermined voltage thereby to drive the switching transistor on in a saturated region of operation; and a charge storage capacitor for providing an output voltage of the power supply.