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[Moved]: how to calculate the gate resistance of Igbt (fg25n120) /Mosfet

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Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

mobinmk said:
Thnkzz...

can i connect 7805 to the output of 7815 to get regulated supply ??

- - - Updated - - -

should i connect zener diode across gate - emiter of igbt to protect from over voltage ??
Click to expand...

you can connect the 7805 input to the output of the 7815 , but remember that it will stress the 7815 even more , his depends upon the current consumption ... how much are u consuming from the 5v regulator ? you have to do power loss calculation and determine if you need heatsink or another regulator
 
Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

shall i connect 1k resistor to 15v and vcc of optocoupler 6n137 ???

is this 1k value is enough ??
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

you can connect the 7805 input to the output of the 7815 , but remember that it will stress the 7815 even more , his depends upon the current consumption ... how much are u consuming from the 5v regulator ?
Click to expand...

The 6N137 only draws 10mA (via 7805) so it's negligible current for the 7815.

shall i connect 1k resistor to 15v and vcc of optocoupler 6n137 ???
Click to expand...

Do what you want, but if the 6N137 supply current is not quite constant (during high/low transitions) a simple series resistor won't help you too much to stabilize its supply voltage. The voltage drop across the series resitor is proportional with the supply current. You might manage to keep it between recommended range (4.5V - 5.5V) but it won't be steady nor guaranteed.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

mobinmk said:
shall i connect 1k resistor to 15v and vcc of optocoupler 6n137 ???

is this 1k value is enough ??
Click to expand...

so to conclude from red alert post , use 7805 it is the best option.

by the way where did u get that name red_alert from the game i assume ?? one of the oldest RTS games :))
 
Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

.. and I've tried hard to hide my age. ;)
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

red_alert said:
.. and I've tried hard to hide my age. ;)
Click to expand...

donot worry we are all in the same boat here :)) 1990s good old days :)
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Thnks Red _ alert

Thnks Electrino.

do u have fb acc ?? whats app acc ??

these 2 guys helped me lot..

may god bless uu

regards

mobin
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Good luck with your projects. I really appreciate your learning progress.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Thnks friends

these 3 days..

am doing pcb design in proteus.

i designed,rectifer,dclink,inverter circuit,

i attached the layout and proteus project file.

any suggestion in designing..

pls share your knowledges IMG-20150227-WA0010.jpg
 

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Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

mobinmk said:
Thnks friends

these 3 days..

am doing pcb design in proteus.

i designed,rectifer,dclink,inverter circuit,

i attached the layout and proteus project file.

any suggestion in designing..

pls share your knowledgesView attachment 114813
Click to expand...

1-my friend take care of your PCB traces , there are online trace calculators inorder to make the correct width with respect to current .
2-make the gate traces as short as possible to reduced stray inductance
3- make also the power traces as short as possible and place the diodes close to the transistors
4- also capacitors of the dc bus should be close to the transistors

3
 
Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Thnks Electro_NS

in order to reduce gate trace.

nly 2 desgin left.

1) remove Tblock -6way ( 6 gate terminals on bottom of lay out)

place 3 way tblock on top of high side switches.(right side in layout) which connect gate trace from 3 high side switches.

also place 3 way Tblock on bottom of high side switches (left side in layout). which connect gate traces from 3 low side switch.


another design is

each single pin header on near to each transistor.

which design is prefer ???

also 6 gate pulse from driver ckt is another pcb board through wires,

any problem if the length of wire is longer than 20cm?
 
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Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Besides the points already mentioned by Electro nS, there are no source terminals for the gate driver circuit. As a basic rule, the driver circuit should directly connect to transistor gate and source terminals and not share common traces with the source current. Driver gate and source connection should be short (as already mentioned) and routed next to each other, not span a large area.

Further observations:
- the tiny bus capacitor packages placed in your layout are rarely sufficient for the required capacitor valiues.
- the clearance of high voltage nodes is already limited by the TO220 package pin distance. It shouldn't be further reduced as it happens in your layout at some places.

I fear it's a path of trial and tribulation til your first working inverter design.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Thnks Fvm

This is my first invert ckt design.

there are no source terminals for the gate driver circuit. As a basic rule, the driver circuit should directly connect to transistor gate and source terminals and not share common traces with the source current. Driver gate and source connection should be short (as already mentioned) and routed next to each other, not span a large area.
Click to expand...

2 PAIR of source terminals are there in the centre of inverter ckt.

1 pair( 3 way- tblock ) for input of 3 phase induction motor.

another one for (Vs pin of IR2110 driver ic.)

if i directly connect driver ckt to gate and source of inverter circuit .

should i design driver ckt and inverter ckt to 1 pcb. ??
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

I use to design a separate PCB for the driver and mount it on pins (vertically) on the main PCB, just near the MOSFET gates. This way, you can have both drivers and DC link capacitors near the MOSFETs.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

sir

i edited the existing pcb layout.gate track ..

is this gate trace is fine ??


pcb.JPG
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Like @FvM has pointed out, you don't have a separate return path for the gate currents to the drivers. That's it, a single wire from the driver to each gate it's not enough.

One possible solution is to design a 6-pin header (G1-S1-G2-S2-G3-S3) on every outer side of a MOSFET row then use individual pairs of twisted wires from the driver PCB to each gate circuit (G-S). You have to avoid any parasitic wire inductances or mutual EMI for the gate circuits.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Thnks Sir,

you don't have a separate return path for the gate currents to the drivers. That's it, a single wire from the driver to each gate it's not enough
Click to expand...

i didnt got it.

in the centre of inverter ckt ,i put 2 no T block-3header

1 Tblock for input of 3 phase induction motor.

2nd T block for (Vs pin for 3 no driver ic IR2110)

a single wire from the driver to each gate it's not enough.
Click to expand...

i used single stranded wire for gate signal from driver ckt to gate of IGBT.

should i twisted the pair with (G-S)

6 -PIN HEADER on the top of high side igbt switches are
G1S1, G2S2, G3S3. (G1,G2,G3 - highside switches -1,2,3), S1,S2,S3 - Source terminals.


6 pin header Tblock on the bottom of lower side switches are

G4S1,G5S2,G6S3.

thus 2 no of s1,s2,s3 is needed,
1no for g1,g2,g3
and other for g4,g5,g6

right ya???

1 problem found.

i use single side pcb,(bottom layer only)

if i make 6 header on the outside of igbt row.

in bottom,

3 gate terminals are taken through gate resistor,

but s1,s2,s3 cant taken out

also

on the top side ,

3 gate terminals are easy to taken ,

but s1s2s3 cant taken out side.
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Reading from page 13 of this app note:

http://www.irf.com/technical-info/appnotes/an-978.pdf

Each MOSFET should have a dedicated connection going directly to the pin of the MGD for the return of the gate drive signal.

Best results are obtained with a twisted pair connected, on one side, to gate and source, on the other side, to gate drive and gate drive retur.
Click to expand...

Find a way to connect the twisted pair of wires from each driver just across the G-S resistor. By the way, the gate series resistor could be located on driver PCB, to simplify the main PCB. Thus only keep the G-S resistors on the main PCB.

- - - Updated - - -

By the way, don't you have some heatsinks for the MOSFETs (IGBTs)?

Aren't they overlapped with the middle pin header? (from your current PCB variant)
 

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

Sir,

i read the app notes..

hvic.jpg

For high side switch,

pin HO for driving gate terminals of high siide switches is G1 ,G2,G3.

and there source terminals are s1 s2 s3, are return terminal to driver ckt.

i made a 6 - pin header on top of igbt

6-pin header Tblock as

G1S1,G2S2,G3S3.

Like wise.

low side switches,
their gate terminals are G4,G5,G6. and their source terminals are S4,S5,S6
are return to driver circuit.

6pin -header Tblock as

G4S4,G5S5,G6S6

i use single side pcb,

thus conflict will come,
in high side switch row, the source(emitter) track is conflict with drain( collector),
in order to avoid conflict, jumper wire will use,

gate terminal can easily taken out.

thus i find 1 solution

Shall i use 2-pin header Tblock for each IGBT instead of 6-pin header Tblock ??

thus 6 no of tblock is needed,

T block can easily placed near to each igbt

each 2-pin header Tblock is G-S pair.

G1S1................................G6S6..

also These (G-S) pair wire be twisted together connected to driver circuit.

also i replaced the gate resistor G4,G5,G6 of low side switches from inverter ckt to main ckt be simple.

space is alotted for heat sink

regards

mobin
 
Last edited:

Re: NEED HELP ,how to calaculate the gate resistance of Igbt (fg25n120) /Mosfet

I think it's a good decision. Good luck with your further design!

- - - Updated - - -

You might choose to put both 6-pin headers beside every MOSFETS row, passing down the common drain trace with the gate series resistors.
 

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