MOSFET reverse leakage

[Kajunbee]

I am looking for a mosfet that can handle 200volt 30 amps for 15 to 20 milliseconds 5 volt gate. Also is there any chance voltage can bleed back when mosfet is in off state.

 

[SK245230]

You can go on digikey or mouser or Farnell website and they have a filter tool that will help you to find your mosfet. Just a question, why do you want only 5v on your gate?

 

[Kajunbee]

the gate could be higher. The signal generator I bought will only output 15 v p-p . This will be my first time working with transistors and I am not sure of what information to look for on data sheets that would tell me how long the duration of current it can handle. To inexperienced eye information is hard to interpret. I will try sites you suggest . Thanks

 

[KlausST]

Hi,

"the first time"..
and then 200V and 30A.

You risk your life! Especially when you don´t know where and what to care for. Safety regulations. How to protect yourself and others....

***
"Back bleed"
Do you mean reverse current? --> MOSFETS usually have built in reverse diodes. So they are conductive in reverse current direction.

Klaus

 

[SK245230]

All what I will say needs to be checked/confirmed because I am also a 'Newbie' in electronics.
Ok. I don't know what signal generator you have but usually they are low power TTL output signal. Which means that they can't give enough current for switching ON and OFF high current transistors. Why? Because they have a big capacitor at the gate and you need to charge this capacitor very fast. So usually you have to put an intermediate device between your mosfet and your logic signal. This device is called a "gate driver" it can turn ON and OFF very fastly by charging the gate capacitor with high current.
Here for you have many example of gate drivers at the TI website:
https://www.ti.com/lsds/ti/power-management/mosfet-and-igbt-gate-drivers-products.page
I'll say that any of them will fit with your application as you have not complicated requirements, just find one that is cheap, simple package, low number of components and enough fast for your application. You can find others on linear, AD, digikey, farnell,... websites.
For your mosfet lets go to farnell for example in mosfet section:
https://www.newark.com/webapp/wcs/s...tegoryId=800000055005&langId=-1&storeId=10194
You need Ids>=30A and Vds>=200. So apply the filters and you will find only a few mosfets.

Concerning the 15 to 20ms you need to look into dissipation, the mosfet has a resistor called Rdson which dissipates energy through heat. For example if rdson is
30 mOhm, then you will dissipate 30mOhm*30A=1.2Watt during the 15-20ms. Probably a heat sink could help but it depends on the frequency of your 15-20ms signal.

Another thing be carefull with your 200V 30A, its deadly dangerous.

 

[KlausST]

Hi,

I don´t agree:

For example if rdson is
30 mOhm, then you will dissipate 30mOhm*30A=1.2Watt during the 15-20ms.

P = I * I * R = 30A * 30A * 0.03Ohms = 27W

Klaus

 

[dick_freebird]

For sparse short-time pulsed heating you should
figure the Joule energy (P*t) and then do the figuring
of die temperature rise. You can find die dimensions
and thickness if you dig. From there, volume and mass
of the silicon (figuring that thermal time constants
mean that the bulk of the package and heat sink
will not be accessed).

There may be single pulse avalanche energy ratings
(depending on the particular device and whether
the answer would sell more, or less of them).

15-20mS is pretty long for a gate controlled event.
The idea would be to switch from 200V at zero current
to 0 volts at 30A current at a reasonable slew rate
(limited by competing interests; too much slew rate
gives you EMI and may violate drain dV/dt guidance
(if you had the driver to do it - a 50-ohm pulse gen
is not that driver). Too slow and you spend too much
time in dissipative regions of operation. Like instead
of the two desired "square" states, you're seeing a
trapezoidal transition where you spend time at (say)
100V and 15A for 10mS (averaged for convenience)
which is 1.5kW and 15J. Now take a FET die that's
maybe 1cm x 1cm x 1mm of silicon. 0.001 cm3 of Si
is 0.0024g of Si. Heat capacity of 0.7 J/(g-degC) then
says your gross slow pulse would heat the die to
a sweet 15J / (0.7 J/(g-degC)*0.0024g) or 8928 degC
temperature rise.

Sound like fun? No? Then do way, way better on gate
drive (or on specifying the problem).

If you got the transition time down to 10uS then you
would be looking at a slightly more tolerable 8 degC
of temp rise.

Suggest you broaden the picture to include the load,
draw yourself a time domain drain voltage and drain
current waveform set, do a poor-boy integral for the
power and then the event energy, and see if there is
any reason to expect success.

 

[Kajunbee]

Appreciate the safety concerns. Maybe the power rating I specified is overkill. What I am working on is capacitor to capacitor charge transfer through inductor to see what is most that can be recovered with different resistances, coil configurations etc. Have found that the speed of the on/off switching effects the recovered charge voltage. I'm hoping the switching speed of a transistor can give me much better results. I am not working with continuous power. A 50 uf 370 vac cap.-1 joule discharge per pulse. The signal generator is 50 ohm output impedance 20v p-p.

 

[SK245230]

@KlausSt: Ah yes you're right
@Kajunbee: I'm sorry but it's very hard to understand you. Maybe you can draw a scheme of what you want to do

 

[Kajunbee]

this is schematic for capacitor to capacitor charge transfer.