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MOSFET (Si/SiC) Forum Discussions

User17150
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Is +15 VGS to high voltage for this NFET? Why is Qg VGS=0-10v only test VDD=100v? Is 180ns dead band enough recovery time for FD diode in 20kHz PWM? How is it considered fast diode yet Trr-144ns recovery typical? What is typical dead band time for IPP120N20NFD? Odd issue since first testing IRFB4227PbF diode (Trr=100ns), datasheet shows shoot through blocking time (100ns). Assume that was gate drive dead band time (100ns) - never had DS short occur.

A few NFET have shorted across DS during very random open loop commutation crash or random 1/2 bridge shoot through past dead band 100ns. Have not had another 1/2 bridge shoot through @180-200ns dead band time. Oddly reverse diode (IPP120N) Trr is slower 144-288ns MAX yet runs 40% cooler, a mind bending attribute. Does the Trr=288ns MAX infer to set dead band for worst case to 280ns? Will reducing VGS to +12v reduce Ton switch recovery transients?

Condition:

Starting low impedance BLDC (400mohm) phases, does not trip analog comparator fault - threshold (64A) peaks yet shorted DS junction twice in same location. The low side current monitor trip threshold (<2us) input to analog fault comparators. Oddly DS random short occurs, mostly high side NFET. The NFETS temperature <24*C monitored via two heat sink sensors. The IPP120N is producing higher than expected recovery transients VDD=139v recovery spike peaks <155v. Will lowering VGS=12v help to reduce these recovery spikes too?

Many thanks!
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User17150
Level 1
First question asked First reply posted
Level 1
Simple questions about IPP120N datasheet testing VGS >+10v Infineon has no answers? Why Diagram 14 (QG) graph stop 10v when maximum VGS is ±20v? QG is important to quantify gate drive resistance especially for parallel NFET's when >+10 VGS!

The OPTIMOS-FD review PDF does not elaborate how 40% reduced Trr/Qrr may effect VGS drive voltages >+12v or diode recovery period. If Qrr is 40% reduced, why body diode has abnormally high recovery period compared to other Infineon NFET's, such as IRFB4227PbF tested in same 3 phase inverter circuit? The IPP120N is 10°C cooler than IRFB42227PbF. Yet Trr body diode is faster and datasheet suggests (100ns dead time) typical - how is lower dead time possible via slower Qrr?

1. Please review the IPP220N/25NFD datasheets to add VGS testing >+10v information?
2. Please review how 40% improved Qrr why it requires larger dead time, >100ns?
3. Please add solder temp/time per case leg/pin as easy to find info in datasheet.
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