Protection circuit and method for power transistors, voltage regulator using the same

摘要

The purpose of the present invention is to supply a method and a circuit simple and accurate enough to protect at least one transistor against exceeding a complex limit implying processing of multiple electrical quantities associated with said transistor. Since in many practical cases said complex limit corresponds to the product of at least two quantities, typically a current and a voltage, the circuit in accordance with the present invention generates electrical signals basically proportional to said quantities, multiplies them, compares the product with a reference signal corresponding to the limit placed on the transistor and acts on the transistor in such a way that said limit is not exceeded. Advantageously the multiplication of currents can be provided simply by means of connection in series of bipolar transistor junctions at which said currents are supplied to the respective emitters. In this case it is additionally advantageous to generate the reference signal by means of connection in series of the bipolar transistor junctions in such a manner as to have an analogous behaviour of the multiplier and the generator. <IMAGE>