Abstract: A protection circuit for at least one power transistor which has at least one control terminal and two main conduction terminals defining a main conduction path includes a first detection means designed to generate a first electrical signal approximately proportional to current flowing in the main conduction path. Second detection means are designed to generate a second electrical signal approximately proportional to voltage across the main conduction path. Multiplying means receive at input the first and second signals and are designed to generate an electrical product signal substantially corresponding to the product of at least the latter. A generator generates an electrical reference signal, and operational amplifier means receive at input the product signal and the reference signal and are designed to generate an electrical difference signal substantially corresponding to their difference.