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Old 21st October 2008, 11:51 AM   #101
Davey T is offline Davey T  United Kingdom
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what sort out output power could you get from two IRS2092 in BTL?

In theory you should be able to do 1.2-1.5kw in 8 ohms from a +-80v rail correct?

Looking to make a 1.2kw amp for my subs. (the drivers are 1200w aes!
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Old 21st October 2008, 09:47 PM   #102
mag is offline mag  Switzerland
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Hi I got around 900Wrms with two irs2092 + irfb4227
driving a 4ohm load in BTL with +/-55V rails.
Now I am designing an amp with irs2092 with +/-85V rails.
It should in theory be able to drive an 8ohm load with at least 300Wrms. I think that if you bridge it and if the power supply keeps up you will be at at least 1200-1300Wrms on 8ohm

@moer
if there is a current limit protection for me it is a nonsense to disable it or to set it to a trip level much higher that required.
If you have the OCP tipping is probably because you have too much inductance between the lower side source and the the -B power supply. You need to put a plane on the PCB in order to reduce that inductance. -B is the power reference ground for the IRS2092 (the chip substrate is connected to that pin).
This inductance probably creates some spikes that makes the current limit trip before than expected.

@ponymxy

Look at the IRS20955 datasheet, there is an explanation of how to set the current limit properly. In the iraudamp 5 reference design the explanation is not clear at all and in the irs2092 datasheet there is no explanation.

ciao

-marco
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Old 22nd October 2008, 05:36 AM   #103
MOER is offline MOER  United States
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Default IR class D chips

I have planes on our PCBs and by IR's own admission the high and low side current trip ccts are overly sensitive.

The PDF which they sent me the other day for their "1Kw" version demands the use of totem poles when using rails as high as +/-85v.

PS I have looked at the data sheet of the 20955 for the past 2 years and know how to calculate the over current trip.

Again by Jun Honda's (The guy who designed this chip) own admission, the current trip point cannot be set below 20-22 amps as the system will shut down all the time. The formulas supplied allow this level of OC trip points but it does not work.

I am using IRFP4227 in our 600w amplifier but will change to 3+3 of IRFB4020 each with their own totem driver.

Run the rails at +/-85v with no totem poles and the chip WILL burn up.
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Old 13th January 2009, 02:56 PM   #104
IVX is offline IVX  Russian Federation
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BTW, 20957 is stable, I tried. So how you think, what's reason to put to the market a full copy of previous chip for the same price?
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Old 14th January 2009, 05:45 PM   #105
witali is offline witali  Russian Federation
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Default 20957

Hi IVX! And much more it is better than 20955? In what it is visible? In Russia is not on sale yet, and on the other hand discrete UcD or IR sounds is much better
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Old 15th January 2009, 03:07 AM   #106
IVX is offline IVX  Russian Federation
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nothing special just stable
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Old 25th January 2009, 09:03 PM   #107
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@MOER
What configuration would you recommend for a 500w amp?
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Old 26th January 2009, 04:21 AM   #108
MOER is offline MOER  United States
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Default 500w amp using IRS20955

Dear Raidfibre,

If the 500w is rated at 4 ohms, you can run +/-85v with Totem drivers between the 20955 and the MOSFETS. I use 3+3 of IRFB4020 for our 600w 4 ohm amplifiers but these are supplied from a well regulated SMPS with PFC.

I disable the IRS20955 OC protection as it must be set at well over 80 amps to work (This is useless anyway)

I use a current transformer in my speaker circuit (It is there anyway as the pro amps we make have microprocessor control and the speaker current is one of the items which the microprocessor reports on).

it is a T50-26 from Micrometals with 100 turns on the secondary and 1 turn for the primary. I shape the output from the 100t secondary to give me a flat response from 50Hz to 10KHz, then I full wave rectify this to give me a DC voltage proportional to the speaker current. Using the value of this DC signal, throw it into a comparator, and use this output to shut the CSD pin down


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Zed Audio Corporation
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Old 26th January 2009, 05:31 PM   #109
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I'm confused as to why you would need to set the OCP to over 80 amps. Is this because it is too sensitive?
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Old 27th January 2009, 04:06 AM   #110
MOER is offline MOER  United States
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Default IRS20955

I'm confused as to why you would need to set the OCP to over 80 amps. Is this because it is too sensitive?

Yes and any spikes from the MOSFET switching action aggrivates the situation. I have been going on with this issue with International Rectifier for almost 3 years and the problem is quite simple. When they monitor the RDS on of the upper and lower MOSFETs, they do this internally and there is no provision to incorporate a low pass filter into the sensing leads.

I also use a discrete circuit I designed and I monitor the RDs on BUT I use LP filters into my comparators. No problem

The one advantge of the IR part is the size and the easily set dead time


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Zed Audio Corp.
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