Control circuit and system for switch mode power supply

摘要

A switch-mode power supply (SMPS) includes a transformer having a primary winding coupled to a power switch, a secondary winding for providing an output of the power supply, and a controller. The controller includes a first input terminal for receiving a current sensing signal related to a current in the primary winding, a second input terminal for receiving a feedback signal related to a current in the secondary winding, and an output terminal for providing a control signal to turn on and off the power switch. When the feedback signal is higher than a first reference voltage, the controller is configured to cause the SMPS to maintain a constant output current at a first current magnitude. When the feedback signal is lower than the first reference voltage, the controller is configured to cause the SMPS to provide a second output current at a second current magnitude higher than the first current magnitude.

主权项

1. A controller for a switched mode power supply (SMPS), wherein the SMPS includes a transformer having a primary winding coupled to a power switch and a secondary winding for providing an output of the power supply, the controller comprising:
a first input terminal for receiving a current sensing signal, which is related to a current in the primary winding; a second input terminal for receiving a feedback signal related to a current in the secondary winding; and an output terminal for providing a power switch control signal to turn on and off the power switch; wherein:
when the feedback signal is higher than a first reference voltage, the controller is configured to cause the SMPS to maintain a constant output current at a first current magnitude; andwhen the feedback signal is lower than the first reference voltage, the controller is configured to cause the SMPS to provide a second output current at a second current magnitude higher than the first current magnitude.