A Versatile Commutation Circuit for PWM Inverters

A new commutation circuit, especially suitable for pulsewidth-modulated (PWM) inverters, is described. The circuit does not require precharging of a commutation capacitor and is therefore ready for commutation at any time. This results in a very flexible and possibly programmable commutation control. Further-more, during PWM operation, the number of commutations per cycle can be halved when compared with other existing circuits. This further improves the circuit efficiency which is already one of the highest available on a per commutation basis. By slightly modifying the basic circuit, one obtains an inherent fuseless protection during shoot-throughs or short circuits. The basic circuit with all its modifications is presented. A detailed circuit analysis is given, together with the efficiency evaluations. The detailed design procedure is outlined and the experimental results obtained on an actual inverter are included.