Blow Mosfet

opor · 9th May 2010, 10:54 AM

I have build my amp following this Schematic . Sound is good but when it was running at high level (volume up) ,Mosfets was blow. What is wrong in schematic?
Need suggestions.

J.R.Freeman · 9th May 2010, 03:53 PM

Greetings Opor,

At first glace something looks odd to me with that gate driver (IC2). Some of the pins marked NC are being used - NC usually means "no connection", I thought. Also, pin 3 is marked VCC, but is connected to +12. Also, COM is connected to VSS, which seems odd to me. U1 also has examples of NC pins in use.

To me there is certainly a few things which are odd about this schematic, but I am fairly new to class D. Still, is this a proven design?

Jim

jej · 9th May 2010, 05:14 PM

Hi,
Your Mosfet have a great input capacitance(5,4nF). So your gate resistor must be lower than 100 ohms (you can try with 10 ohms). You have to increase C10 10uF for example but with a low ESR
What is your supply voltage VCC ?

opor · 9th May 2010, 05:42 PM

my supply is +-65V

opor · 9th May 2010, 05:45 PM

And the inductor and fets are so hot.

jej · 9th May 2010, 05:55 PM

OK In this case you can use IRFB4019. This MosFet is more suitable in your design.
Otherwise if you still have problems may be a dead-time would be necessary to avoid cross-conduction

jej · 9th May 2010, 06:05 PM

If your inductor is hot, may be inappropriate magnetic circuit is used!
What is your magnetic circuit? How many turns? And what is your impedance load?

opor · 9th May 2010, 06:11 PM

I wonder that the feed back resistor too high so I have decrease it to 47K but it is still hot. IRFB4019 is hard to get here. Any substitutions?

opor · 9th May 2010, 06:17 PM

At first I use 18uH terroid core as mention in the schematic.But it get hot quickly. Now it is 55uH and it seem colder but still hot which could not be with class D amp.

opor · 9th May 2010, 06:20 PM

8 ohm load.

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9th May 2010, 03:53 PM	#2
J.R.Freeman diyAudio Member Join Date: Aug 2008	Greetings Opor, At first glace something looks odd to me with that gate driver (IC2). Some of the pins marked NC are being used - NC usually means "no connection", I thought. Also, pin 3 is marked VCC, but is connected to +12. Also, COM is connected to VSS, which seems odd to me. U1 also has examples of NC pins in use. To me there is certainly a few things which are odd about this schematic, but I am fairly new to class D. Still, is this a proven design? Jim

9th May 2010, 05:14 PM	#3
jej diyAudio Member Join Date: Apr 2010 Location: marly le roi	Hi, Your Mosfet have a great input capacitance(5,4nF). So your gate resistor must be lower than 100 ohms (you can try with 10 ohms). You have to increase C10 10uF for example but with a low ESR What is your supply voltage VCC ?

9th May 2010, 05:42 PM	#4
opor diyAudio Member Join Date: Nov 2005	my supply is +-65V

9th May 2010, 05:45 PM	#5
opor diyAudio Member Join Date: Nov 2005	And the inductor and fets are so hot.

9th May 2010, 05:55 PM	#6
jej diyAudio Member Join Date: Apr 2010 Location: marly le roi	OK In this case you can use IRFB4019. This MosFet is more suitable in your design. Otherwise if you still have problems may be a dead-time would be necessary to avoid cross-conduction

9th May 2010, 06:05 PM	#7
jej diyAudio Member Join Date: Apr 2010 Location: marly le roi	If your inductor is hot, may be inappropriate magnetic circuit is used! What is your magnetic circuit? How many turns? And what is your impedance load?

9th May 2010, 06:11 PM	#8
opor diyAudio Member Join Date: Nov 2005	I wonder that the feed back resistor too high so I have decrease it to 47K but it is still hot. IRFB4019 is hard to get here. Any substitutions?

9th May 2010, 06:17 PM	#9
opor diyAudio Member Join Date: Nov 2005	At first I use 18uH terroid core as mention in the schematic.But it get hot quickly. Now it is 55uH and it seem colder but still hot which could not be with class D amp.

9th May 2010, 06:20 PM	#10
opor diyAudio Member Join Date: Nov 2005	8 ohm load.

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