Method and apparatus for reducing standby power of switching mode power supplies

摘要

An apparatus for coupling a switching mode power supply (SMPS) controller to a rectified line voltage. The apparatus includes a high-voltage startup transistor configured to provide a charging current during a startup phase of the SMPS controller and to provide substantially no current during a normal operation phase of the SMPS controller. A switch coupled to the high-voltage startup transistor. The switch receives a control signal from the SMPS controller, for turning off the switch during the startup phase and turning on the switch during the normal operation phase. A biasing device is connected in series with the switch and maintains the startup transistor in an off state when the SMPS controller is in the normal operation phase. A standby current in the apparatus is substantially lower when the SMPS controller is in the normal operation phase than the charging current in the apparatus when the SMPS is in the startup phase.

主权项

1. An apparatus for coupling a switching mode power supply (SMPS) controller to a rectified line voltage, the apparatus comprising:
a high-voltage startup transistor configured to provide a charging current during a startup phase of the SMPS controller and to provide substantially no current during a normal operation phase of the SMPS controller; a switch coupled to the high-voltage startup transistor, the switch being configured to receive a control signal from the SMPS controller, the control signal turning off the switch during the startup phase and turning on the switch during the normal operation phase; and a biasing device connected in series with the switch, the biasing device being configured to maintain the startup transistor in an off state when the SMPS controller is in the normal operation phase, whereby a standby current in the apparatus is substantially lower when the SMPS controller is in the normal operation phase than the charging current in the apparatus when the SMPS is in the startup phase.