In some examples, a controller circuit comprises: a voltage subtractor circuit having a subtractor output and first and second subtractor inputs, the first subtractor input adapted to be coupled to a first current terminal of a transistor, and the second subtractor input adapted to be coupled to a second current terminal of the transistor; an internal voltage generator circuit having a generator input and a generator output, the generator input adapted to be coupled to the first current terminal; and a gate control circuit having a gate control input and a gate control output, the gate control input coupled to the subtractor output, the gate control output adapted to be coupled to a gate of the transistor, the gate control circuit including a switch coupled between the gate control output and the generator output.