Patent ID: 8872441

Claim:
A controller with protection function, used to control a transistor having a control terminal, a first terminal coupled to a load and a second terminal, comprising: a judgment unit, coupled to the transistor and generating a current reducing signal when a potential of the first terminal of the transistor or the voltage difference between the first terminal and the second terminal of the transistor is higher than a first preset value; and a current control unit, coupled to the control terminal of the transistor to control a current flowing through the transistor to substantially be a preset current value and reducing the current when receiving the current reducing signal, wherein the second terminal of the transistor is coupled to a current detecting unit which generates a current detecting signal according to an amount of a current flowing through the current detecting unit and controls the current flowing through the transistor according to the current detecting signal, the current detecting unit comprises a first current detecting resistance and a second current detecting resistance and the current control unit comprises a select switch, and an end of the select switch is coupled to the second terminal of the transistor and the other end thereof is coupled to the first current detecting resistance or the second current detecting resistance according to the current reducing signal.