MOSFETs and FREDFETS in motor drive equipment

The authors discuss the properties of the FREDFET, a technology which yields a MOSFET with a very fast built-in reverse diode with properties similar to a discrete fast epitaxial rectifier. It is shown that its characteristics make the device an excellent choice for high frequency bridge leg systems such as 20 kHz AC motor control systems. Investigations have been carried out in dedicated test circuits as well as in a 20 kHz ACMC system which show that the FREDFET exhibits very low diode losses. It compares favorably with a discrete solution, using two extra diodes to overcome the slow speed of the standard built-in diode, and also with devices from the standard ranges.<
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