A pyrotechnic circuit breaker, comprising a body, an igniter, a bus bar, and a piston which comprises a cutting edge and is movable along a normal direction to cut a portion of the bus bar, thereby separating the bus bar to break a circuit, wherein the cutting edge of the piston is stepped so that the portion of the bus bar is cut sequentially, in at least two successive cutting operations, characterized in that the bus bar comprises a breakable portion configured to be cut by the cutting edge of the piston, wherein said breakable portion comprises slots in order to divide the breakable portion into multiple sub-portions that are adapted to be cut sequentially by the stepped cutting edge of the piston.