Patent ID: 9293981
Filing Date: 2016-03-22
CPC Classification: H02M

Claim Text:
1. A controller for a switch mode power supply (SMPS), the controller comprising: a first terminal for coupling to a startup resistor and to a control terminal of a power switch which is coupled to a primary winding of the power supply; where the controller is configured: during a startup, to cause the power switch to amplify a startup current from an external input voltage through the startup resistor and provide a startup power to the controller; and during a normal operation, to provide a power switch control signal to turn on and off the power switch for controlling a current flow in the primary winding and regulating an output of the power supply; wherein: during startup, the controller is configured to provide a current path for the amplified startup current to flow from an output of the power switch to charge up a startup capacitor and to provide the startup power to the controller; and during normal operation, the controller is configured to separate the power switch from the startup capacitor, and to provide the power switch control signal by amplifying a pulsed control signal from a pulse signal generation circuit.