Patent ID: 7161776

Claim:
A method for monitoring a power output stage including at least one half bridge with upper and lower semiconductor switches connected in series and to which an operating voltage is applied, the semiconductor switches being alternately controllable to a switched-on state and a switched-off state by pulse-width modulated pulses, and wherein a junction point between the upper and lower semiconductor switches in the at least one half bridge form an output, the method comprising the steps of: measuring a first measured voltage across the lower semiconductor switch when the upper semiconductor switch is switched on and measuring a second measured voltage across the lower semiconductor switch when the lower semiconductor switch is switched on; comparing a difference between the operating voltage and the first measured voltage with a predetermined voltage and comparing the second measured voltage with the predetermined voltage which is the maximum permissible voltage across a semiconductor switch when it is switched on; and identifying one of the power output stage and the output of the at least one half bridge as faulty when at least one of the difference and the second measured voltage is each greater than the predetermined voltage.