How to identify max switching frequency of a MOSFET - diyAudio
 How to identify max switching frequency of a MOSFET
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 15th July 2008, 06:36 AM #1 diyAudio Member   Join Date: Feb 2008 hwo to identify max switching frequency of a MOSFET Hi all, Can anyone help me to identify the maximum operating frequency range of IRPB450 power MOSFET. http://www.euroelektronik.com.pl/sit...rs/IRFP450.pdf Thank You
 15th July 2008, 08:49 AM #2 diyAudio Member   Join Date: Feb 2005 Location: south of lower saxon The switching speed (measured in V/µs for instance) of such MOSFETs is basically determined by the value of the gate resistor (which prevents unwanted oscillation) and the current capability of the gate driving circuit. Since the gate is isolated from the drain and source pin it reacts as a capacitor and therefore to charge/discharge a capacitor with a certain speed a(n un)limited current is necessary to perform that task. So, without knowing the circuit, you're using this MOSFET in, it's almost impossible to make any predictions on how far you can drive the switching frequency. Post the schematic and someone might be able to calculate/predict the maximum switching frequency.
 15th July 2008, 03:07 PM #3 diyAudio Member   Join Date: Feb 2008 could that IRFP 450 mosfet operate at 100KHz frequency.
 15th July 2008, 04:59 PM #4 diyAudio Member     Join Date: Oct 2003 Location: Near the sea Your question does not make much sense. You can usually get over 30Mhz bandwidth from 500V/600V TO-247 MOSFET and over 70Mhz from TO-220 ones. Switching losses and gate drive losses are the actual limiting factors for operating frequency, not the "speed" of the MOSFET itself. BTW: 100Khz is hardly a problem for any MOSFET. __________________ I use to feel like the small child in The Emperor's New Clothes tale
 15th July 2008, 05:17 PM #5 diyAudio Member     Join Date: Jun 2008 Location: Dhaka Hi, 100kHz is hardly a problem for IRFP450. I have used it upto 200kHz with no problems. You can calculate the maximum switching frequency of the MOSFET from the datasheet by calculating the turn on and turn off time / propagation delay time. __________________________________________________ ___________________________ The strongest man in the world is one, who stands alone for achieving something good. পৃথিবীতে সেই সবচেয়ে শক্তিশালী ব্যক্তি, যে ভাল কিছু অর্জনের জন্য একাই নিরন্তর চেষ্টা চালিয়ে যায়।
 16th July 2008, 01:48 AM #6 diyAudio Member   Join Date: Feb 2008 [QUOTE]Originally posted by Tahmid [B]Hi, 100kHz is hardly a problem for IRFP450. I have used it upto 200kHz with no problems. You can calculate the maximum switching frequency of the MOSFET from the datasheet by calculating the turn on and turn off time / propagation delay time. so u mean to say that the formula to calculate the max switching frequency of a MOSFET is = ( turn on delay time + turn off delay time) / ( rise time + fall time).....please correct if im wrong.
 16th July 2008, 04:16 AM #7 diyAudio Member   Join Date: Apr 2006 Location: Minnesota jegandren, Eva answered your question in post #4. Any switching device (MOSFET) has losses associtaed with the switching, and it also has conduction losses. Together these will determine the maximum switching frequency. Stated diffferently, Psw=(Eon+Eoff)*Freq+DutyCycle*(Pcond). You also need to consider the losses, if any, in the free wheeling diode. Rick
 16th July 2008, 07:27 AM #8 diyAudio Member     Join Date: Oct 2003 Location: Near the sea In other words: It's the amount of residual heat produced in every switching event what limits the maximum allowable number of events per second. You would burn most MOSFET before getting close to the frequency limit imposed by switching times. __________________ I use to feel like the small child in The Emperor's New Clothes tale
 17th July 2008, 07:12 PM #9 diyAudio Member   Join Date: Jun 2008 Hi jegandren, Do not bother for max. frequency as most of the mosfets can be operated at MHZ range if you can use proper configuration. Since you are new in this field, instead of going for 100 khz, you should try first with 30 khz range, then try 100/200 khz range and you can be rest assured that irfp450 is capable to take you more than that range. Thanks.

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