100kHZ HV Mosfets recommendation

[CV]

Allo

I'm looking to drive a small PP ferrite tx at 100kHz, at about 400V p-p, current up to 500mA.

Want to drive them using op-amps so ideally looking for a device >600V and with low input capacitance.

Any recommendations before I trawl through a ton of hexfet datasheets?

Ta very much,
cv

[mwh-eng]

IRFIBE20G
Description HEX/MOS N-CH 800V 1.4A TO-220FP


Easy way to look for Mosfets:
www.digikey.com
Enter "Mosfet" and click search.

[richie00boy]

www.irf.com

IR have on their website a product specifier thing where you just choose what voltage etc. you want from drop-down lists and you can narrow it down to a manageable amount of current products.

www.onsemi.com

I'm sure OnSemi have something similar.

Manufacturers websites are the best places to look anyway as you can be sure that the info is current and the datasheets are correct and the latest version.

[Eva]

If you are looking for something easy to drive up to 100Khz, I strongly recommend IGBTs


Check this out :
http://www.infineon.com/cgi/ecrm.dll...rent_oid=19621

SKP02N60 from Infineon :

- 142pF input capacitance [Vce=25V, Vge=0, f=1Mhz]
- 10pF reverse transfer capacitance
- 18pF output capacitance
- 14nC total gate charge [Vge=15V, Ic=2A, Vcc=480V]
- Integrated soft, fast recovery anti-paralell diode
- 2V voltage drop at Ic=2A

Compare this IGBT to the IRFIBE20G MOSFET suggested by mwh-eng

The MOSFET has lower current rating and still 10 times higher output and reverse transfer capacitances, and 4 times higher input capacitance

The only drawback of the IGBT is slighty slower turn-off, but actually, given the same limited gate discharge current, the IGBT may turn off faster than the MOSFET due to lower capacitances

Gate charge is not comparable because in the MOSFET it's measured for Vgs=10V and Id=1A while in the IGBY it's measured at Vge=15V and Ic=2A [but it's still 3 times lower for the IGBT in these conditions]

[JonMarsh]

Another alternative to consider for easy drive and low losses are charge compensation structure MOSFETs, like Infineon CoolMOS and ST MDMesh. These transistors have about 1/5 the chip size of conventional HV MOSFETs at 600V, with of course lower overall capacitance and gate charge. Compared with the IGBT, CoolMOS FETs don't have any tail current due to the carrier recombination time in an NPT IGBT, which substantially increases switching loses above 40 kHz.

From Infineon, the SPN02N60C3 is a 2A rated device in SOT223 package,

Ciss = 200 pF
Crss = 4 pF


Due to the low feedback miller capacitance, overall gate charge is very low and switching time is quite fast.

Qg[total] = 9.5 nC tyipcal, 12 nC max

Another factor in favor of the CoolMOS transistor is that it doesn't have an intrinsic junction drop due to the PN junction in the collector of the IGBT, so with reducing current the forward drop can be less than 1V. At 0.4A you'll see a total drop between 1 and 2V, depending on junction temperature and the foil area you use for cooling.

Best regards,

Jon

[CV]

Should have said that I'll be driving sine and not square waves - cross between switch mode and a regenerative supply...

Nonetheless, thanks very much indeed for all the responses so far - enlightening to say the least... keep em coming!

Cheers,
cv

[mwh-eng]

"Compare this IGBT to the IRFIBE20G MOSFET suggested by mwh-eng"

Hmm! I should be more careful. My intention was not to suggest a specific part. The perception must have been such; however, even though I did not use the word suggest or suggested.

I intended to offer a method of searching for switches. I should have suggested, search for "Mosfets", "IGBTs", "Bipolars", etc. I apologize for my un-intentional misleading.

I agree with another poster, go to the manufacturers' websites to get specific information. In most cases using the digikey website, it links to the manufacturer's data sheet. No, I don't work for digikey or have any stock in that company. I have purchased parts from them and others that will sell in small quantities. In recent times more electronics suppliers are selling in small quantities at reasonable prices, and I am thankful.

I have a question: Is it legal, ethical, and/or appropriate to post a schematic belonging to someone else or a company on this forum, without their permission? I assume that schematics obtained from a government patent office is fair game. What about a schematic that is obtained through reverse engineering a circuit board? Sometimes I request a schematic, in order to aid in troubleshooting. Maybe this should be handled with private email, and even then I'm not sure if it's appropriate.

Thanks

[PMA]

Originally posted by Eva
If you are looking for something easy to drive up to 100Khz, I strongly recommend IGBTs

Eva,

which frequency would you recommend as a border line between the use of MOSFET's and IGBT's.

Regards,
Pavel

[JonMarsh]

which frequency would you recommend as a border line between the use of MOSFET's and IGBT's

This is highly dependent on the specific technology of the IGBT, as well as the application- PT type IGBTs, for example, have relatively high peak tail current, but a low intrinsic carrier lifetime due to irradiation or other lifetime control processing, and so decay fairly quickly- they work well in some resonant circuits at higher frequencies. OTOH, NPT type IGBTs, such as Infineon and Toshiba make, have relatively low tail current magnitude, but long lifetime, and depend on the voltage rise at turn off to start carrier sweep out. Field stop IGBTs are improved over NPT types in this regard, but still far from perfect.


A good rule of thumb is to take a look at the Eoff losses, multiply times the proposed switching frequency, and see how the combination of switching losses and conduction losses trades off with frequency. Don't forget one point, though- many types of IGBTs have strong temperature dependency of switching loss (most do, other than NPT types), and at frequency like 100 kHz, can go into thermal runaway.

~Jon

[PMA]

Thanks, Jon.