Patent ID: 7489487

Claim:
A multi-level power converter, comprising: a DC power source having N terminals with N-level voltage potentials, wherein N is an Integer more than two; a plurality of switching legs connected in parallel to the DC power source having, 2(N- 1 ) switching elements connected in series, and 2(N- 2 ) clamp diodes connected between (N- 2 ) intermediate DC potential terminals and middle points of the switching legs respectively, in order to clamp the potential of the middle points of the switching legs; a control means for supplying gate pulses to the switching elements so that a N-level phase voltage may be obtained from a central point of each of the switching legs; a plurality of supervising means, each supervising means for supervising a respective of the switching elements to output a failure signal when a voltage between positive and negative terminals of the respective of the switching elements exceeds a predetermined threshold voltage level during a period of its ON-state, by inputting to an AND circuit the voltage and a gate pulse for switching the respective of the switching elements; and a logic operating means for detecting an over-current failure of main circuit elements to output a device fault signal using the failure signals from the plurality of supervising means; wherein an operation of the logic operating means at least includes AND condition of at least two failure signals to output the device fault signal.