Patent ID: 6909585

Claim:
Protection circuit ( 1 ) to be located between a power supply ( 2 ) and further circuitry ( 20 , 30 ) for protecting said further circuitry ( 20 , 30 ) against voltage irregularities and comprising on input ( 3 , 4 ) to be coupled to said power supply ( 2 ) and an output ( 5 , 6 ) to be coupled to said further circuitry ( 20 , 30 ) and a main transistor ( 7 ) of which a first serial electrode is coupled to said input ( 3 ) and of which a second serial electrode is coupled to said output ( 5 ) and of which a control electrode is coupled to a switching circuit ( 10 ) for rendering said main transistor ( 7 ) operative/non-operative dependently upon an input voltage at said input ( 3 , 4 ), wherein the switching circuit ( 10 ) comprises a comparator ( 11 ) for comparing said input voltage at said input ( 3 , 4 ) with a threshold voltage (Vth) and for in dependence of comparison results controlling a control electrode voltage at said control electrode of said main transistor ( 7 ) by using at least one switch ( 12 , 13 ) to couple the control electrode to ground, or couple the control electrode to a higher reference voltage source, to switch the main transistor off or on.