IRS2092 Rail Voltage Limit with single pair of mosfets? - diyAudio
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Old 4th August 2012, 03:19 PM   #1
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Default IRS2092 Rail Voltage Limit with single pair of mosfets?

I would like to build a class-d amp using the IRS2092 chip and a single pair of mosfets connected directly to the 2092 without driver transistors as per the data sheet. I have an existing power supply that I want to use with +/- 85v rails and 12v reference etc. I was hoping to only use a single pair of mosfets per channel but most of the designs i have seen with a single pair of mosfets have rails around 65v at max.

all of the designs I have seen with 80+ volt rails use two pairs of mosfets with driver transistors and produce more power than i really need. I have limited space inside the chassis and I want to keep the design as simple as possible. power output is not my first priority as i know it is possible to get at least 200 watts from 65v rails so with 85v rails this should easily make more power than i really need.

Can I build the design sheet example with a single pair of mosfets and 85v rails and be ok? is there a best choice for mosfets for such an application?


Zc
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Old 4th August 2012, 04:33 PM   #2
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Maybe IRFB5620PbF or IRFB4620PbF would work without drivers? Ciss and Rds are kind of high though.

The IRS2092 and FETs would probably both run really hot if they managed to work without drivers.
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Old 4th August 2012, 04:43 PM   #3
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what about IRFB4227 i have seen several 200-300 watt designs that use these without drivers but with 65v rails.
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Old 4th August 2012, 04:49 PM   #4
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I found a design that uses one pair of STW38NB20 devices with 85v rails but that design uses a Tripath TA0105 chip so im not sure if I can use those with a IRS2092??


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Old 4th August 2012, 05:11 PM   #5
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STW38NB20 is very old and outdated. I know from reading others experience here that IRFB4227 won't work without drivers.

I guess just wait for input from one of the pro's here.
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Old 5th August 2012, 10:06 PM   #6
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IRFB4019's work well with the irs2092.
I get 300watts from one pair at +/- 45 volts supply into 4 ohms.
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Old 6th August 2012, 08:54 AM   #7
lithoc is offline lithoc  Malaysia
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IRFB4020 fits your requirement ... compact (4020 generate less heat), high voltage rail of 80V and > 200w @ 8ohm .

if your speaker is 4ohm then IRFB4019 is even generate less heat but you need to reduce the voltage rail to 50V

May be you try to look at LJM L25D or L20 for references...
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Old 7th August 2012, 01:24 AM   #8
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I have 85 volt rails to work with and i am looking for 200-300 watts at 8 ohms but i will be using the amp with both 8 and 4 ohm speakers depending on which set i end up sticking with so the design has got to fit that requirement~!
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Old 7th August 2012, 07:28 AM   #9
Cristi is offline Cristi  Europe
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Default IRS2092 + IRFB4227

Quote:
Originally Posted by Zero Cool View Post
what about IRFB4227 i have seen several 200-300 watt designs that use these without drivers but with 65v rails.
IRS2092 + IRFB4227 design can deliver up to 800W on 4R supplied with +-91V at <0.5% THD and over 750W at ~0.1% THD.
Before anyone would rush in to say that is impossible to drive IRFB4227 with IRS2092 without buffers, I would announce that I already did, I have lots of boards with this pair and no one had failed since more than one year.
Recently I discovered that this combination is used even in some PA amplifiers rated from 500W to more or less 3000W (BTL) per channel. without buffers of course. The secret to keep them up and running is in layout and gate resistors.
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Old 7th August 2012, 11:51 AM   #10
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Quote:
Originally Posted by Zero Cool View Post
I would like to build a class-d amp using the IRS2092 chip and a single pair of mosfets connected directly to the 2092 without driver transistors as per the data sheet. I have an existing power supply that I want to use with +/- 85v rails and 12v reference etc. I was hoping to only use a single pair of mosfets per channel but most of the designs i have seen with a single pair of mosfets have rails around 65v at max.

all of the designs I have seen with 80+ volt rails use two pairs of mosfets with driver transistors and produce more power than i really need. I have limited space inside the chassis and I want to keep the design as simple as possible. power output is not my first priority as i know it is possible to get at least 200 watts from 65v rails so with 85v rails this should easily make more power than i really need.

Can I build the design sheet example with a single pair of mosfets and 85v rails and be ok? is there a best choice for mosfets for such an application?


Zc
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