Fast-recovery epitaxial diode field-effect transistor

A fast-recovery epitaxial diode field-effect transistor (also fast-reverse epitaxial diode field-effect transistor , abbreviated FREDFET or FredFET , English ) is a special power field effect transistor , which is especially used for switching inductive loads ( transformers , electric motors ) in full-bridge circuit ( four-quadrant controller or quasi-resonant push-pull switching power supplies ) is suitable.

Structure and application

Circuit symbol of a self-locking n-channel and p-channel MISFET with an additional inverse diode

In this transistor, the inverse diode (also called body diode, see structure of an n-MOSFET ) caused by the semiconductor structure is equipped with switching times that are particularly short compared to conventional power MOSFETs. This is achieved by doping with heavy metals , which significantly reduces the storage charge and the blocking delay time .

This makes it possible to switch inductive loads in very short periods of time. FredFETs are mostly used in so-called four - quadrant controllers and other applications with a full bridge ( H-bridge ) made of MOSFET switches. Without a fast inverse diode, a fast disconnection and reconnection of inductive loads would result in a current flow in the switching-on MOSFET due to the storage charge of the body diode in the opposite MOSFET, which can damage the switching-on MOSFET. This can partly be avoided by switching on the MOSFET at the moment the body diode is conducting, whereby it takes over the current flow of the diode and the diode can already recover. At high working frequencies or low modulation levels, combined with high reactive current, this time is not enough for the diode to be released. A further destruction mechanism is therefore more important, which is based on the fact that if the body diode has not yet been released and a reverse voltage is forced on it, a parasitic transistor structure in this blocking MOSFET can break down and destroy it.

However, fast rectifier diodes , also referred to as fast recovery rectifier diodes , which are connected externally as free-wheeling diodes in parallel to the internal inverse diode, have even shorter and therefore better switching behavior. This follows from the fact that an external diode and its structure can be optimized for short switching times and forward voltage regardless of the MOSFET structure . This applies in particular to fast rectifier diodes based on the semiconductor material silicon carbide (SiC). In the case of low working voltages, silicon Schottky diodes can be used as freewheeling diodes , which are not only significantly faster, but also completely take over the inverse current flow through the body diode due to their low forward voltage.

Alternative name

The abbreviation FREDFET sometimes also denotes the term free running extinction diode FET (FET with free-wheeling extinction diode ).

literature

Jon Harper: MOSFETs with fast body diodes . In: electronics industry . No. 5 , 2007, p. 30–31 ( PDF [accessed February 23, 2013]).

Web links

Power MOSFET Modules Rated for 100V . On: powerelectronics.com. November 30, 2005.
High-Speed, High-Voltage Gate Driver IC and Half-Bridge FredFET Combo Delivered in Compact 11-Pin SIP (MiniSIP) . On: International Rectifier. February 2004.

Individual evidence

↑ Ulrich Nicolai, Tobias Reimann, Jürgen Petzoldt, Josef Lutz: Application manual IGBT and MOSFET power modules . 1st edition. ISLE Verlag, 1998, ISBN 978-3-932633-24-9 , pp. 27 ( PDF version ). PDF version ( Memento of the original dated December 20, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2
↑ Hubert Aigner, Kenneth Dierberger, Denis Grafham: Improving the full-bridge phase-shift ZVT converter for failure-free operation under extreme conditions in welding and similar applications . In: Conference Record - IEEE Industry Applications Society Annual Meeting . tape 2 . IEEE INC, 1998, pp. 1341–1348 , doi : 10.1109 / IAS.1998.730318 .
↑ Alexander Fiel, Thomas Wu: MOSFET failure modes in the zero-voltage-switched full-bridge switching mode power supply applications . In: Applied Power Electronics Conference and Exposition, 2001. APEC 2001. Sixteenth Annual IEEE . tape 2 , 2001, p. 1247–1252 , doi : 10.1109 / APEC.2001.912525 ( PDF ).
↑ Jonathan Dodge: Power MOSFET Tutorial . In: Jonathan . No. 12 , 2006, p. 1-4 ( PDF ). Also: Jonathan Dodge: Power MOSFET Tutorial . In: Application note APT (Advanced Power Technology) . tape
403 , 2004 ( PDF ).

[1] Ulrich Nicolai, Tobias Reimann, Jürgen Petzoldt, Josef Lutz: Application manual IGBT and MOSFET power modules . 1st edition. ISLE Verlag, 1998, ISBN 978-3-932633-24-9 , pp. 27 ( PDF version ). PDF version ( Memento of the original dated December 20, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2

[2] Hubert Aigner, Kenneth Dierberger, Denis Grafham: Improving the full-bridge phase-shift ZVT converter for failure-free operation under extreme conditions in welding and similar applications . In: Conference Record - IEEE Industry Applications Society Annual Meeting . tape 2 . IEEE INC, 1998, pp. 1341–1348 , doi : 10.1109 / IAS.1998.730318 .

[3] Alexander Fiel, Thomas Wu: MOSFET failure modes in the zero-voltage-switched full-bridge switching mode power supply applications . In: Applied Power Electronics Conference and Exposition, 2001. APEC 2001. Sixteenth Annual IEEE . tape 2 , 2001, p. 1247–1252 , doi : 10.1109 / APEC.2001.912525 ( PDF ).

[4] Jonathan Dodge: Power MOSFET Tutorial . In: Jonathan . No. 12 , 2006, p. 1-4 ( PDF ). Also: Jonathan Dodge: Power MOSFET Tutorial . In: Application note APT (Advanced Power Technology) . tape
403 , 2004 ( PDF ).