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Old 12th September 2012, 05:21 PM   #2521
paskal9 is offline paskal9  Malaysia
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guys, anyway suggestion to improve the irs900d performance? i've used the original irs900d with some extra caps bypass but still sticking to the original tl071, cd4049, ir2110 but with irfb5615 and 20uh i got these at the output:

at the mosfet gate:
Click the image to open in full size.

at the inductor input:
Click the image to open in full size.

initial testing done at +-30V using uf4007 and 1n4148. gate resistor is 10ohm. the amp plays fine without distorting but just wondering if the result i'm getting is optimal?
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Old 12th September 2012, 06:12 PM   #2522
exflaco is offline exflaco  Armenia
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Manojtm ,of course talking about woofer amp
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Old 12th September 2012, 07:24 PM   #2523
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[QUOTE=paskal9;3162236]guys, anyway suggestion to improve the irs900d performance? i've used the original irs900d with some extra caps bypass but still sticking to the original tl071, cd4049, ir2110 but with irfb5615 and 20uh i got these at the output:

at the mosfet gate:

Look at the gate drive's supply, measure first the largest spurious swing at the gate pin of the FET. Then select cer-cap to comply resosnance frequency.
Then take new curves. And now the largest again, put that MLCC in between driver power supply pin and previously chosen cap. 3 different is enough. you increase efficiency many %!!! and that serial res, lower that to 3R or so...
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Old 12th September 2012, 08:22 PM   #2524
Pafi is offline Pafi  Hungary
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Quote:
Originally Posted by paskal9 View Post
guys, anyway suggestion to improve the irs900d performance? [...] the amp plays fine without distorting but just wondering if the result i'm getting is optimal?
Dead time seems to be very high (400/200 ns), this leads to distortion, however feedback tries to compensate it.

P.S. Nice to see someone who does measurements, and posts it!

Last edited by Pafi; 12th September 2012 at 08:25 PM.
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Old 13th September 2012, 02:01 AM   #2525
paskal9 is offline paskal9  Malaysia
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first of all guys, i'm not formally educated in electronics so please bear with me. use simple english if you can. still learning here.

Quote:
Originally Posted by Touho-serkku View Post
Look at the gate drive's supply, measure first the largest spurious swing at the gate pin of the FET. Then select cer-cap to comply resosnance frequency.
Then take new curves. And now the largest again, put that MLCC in between driver power supply pin and previously chosen cap. 3 different is enough. you increase efficiency many %!!! and that serial res, lower that to 3R or so...
for the most part, i have no idea what i'm supposed to do (refer above). changed the gate resistor to 3 ohm and the results are posted below.

Quote:
Originally Posted by Pafi View Post
Dead time seems to be very high (400/200 ns), this leads to distortion, however feedback tries to compensate it.

P.S. Nice to see someone who does measurements, and posts it!
most people don't have access to a scope so it's quite hard to measure anything and for those that do, you guys could be quite intimidating. so it's much easier to just keep quiet and just browse through any idea on how to optimize the dead time?

anyway here's the irs900d schematic that i'm using:
the component values are correct and used for this measurement.
Click the image to open in full size.


measurement points:
Click the image to open in full size.

point A:
(removed 100k feedback resistor, ir2110 and mosfet just in case). feed 1khz sine.
Click the image to open in full size.

point B:
(removed 100k feedback resistor, ir2110 and mosfet just in case). feed 1khz sine.
Click the image to open in full size.

point C:
no input signal. amp is idle.
Click the image to open in full size.

point D:
no input signal. amp is idle.
Click the image to open in full size.

IRF5615: 150V, 35A, 0.039ohm rds(on), gate charge 26nc (typ)/40nc (max), trr 80ns (typ)/120ns (max), qrr 312nc (typ)/468nc (max)

targeted implementation as a subwoofer amp. will be bridging them and feeded with balanced signal from minidsp. target operational voltage is at +-63V. target load is a 4ohm subwoofer with around 1200w or so peak power. the amp would only be seeing <150Hz signal.
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Old 13th September 2012, 03:41 AM   #2526
CPX is offline CPX  Romania
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Do you have isolated probes?
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Old 13th September 2012, 04:13 AM   #2527
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by CPX View Post
Do you have isolated probes?
i don't. though i could try and ask around for it. issit important to have one?
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Old 13th September 2012, 10:11 AM   #2528
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Hi,paskal9 does by not changing the RSS(8k2) will not affect the whole circuit?cause you're using -/+30,for your initial test. i think 8k2 is for -/+ 90v please correct me if i'm wrong.thank's.
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Old 13th September 2012, 10:55 AM   #2529
paskal9 is offline paskal9  Malaysia
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Quote:
Originally Posted by don2007ksa View Post
Hi,paskal9 does by not changing the RSS(8k2) will not affect the whole circuit?cause you're using -/+30,for your initial test. i think 8k2 is for -/+ 90v please correct me if i'm wrong.thank's.
supposedly, yes. but i measured at the TL071 rail and got 4.5V something from using 4.7V zener. so i assumed that the TL071 still get enough voltage for it to work.
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Old 13th September 2012, 12:09 PM   #2530
manojtm is offline manojtm  India
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Quote:
Dead time seems to be very high (400/200 ns),
Hi Pafi

how you say that 400/200 ns . picture shows 12.14ns (1st picture at the mosfet gate)

Hi paskal9,

did you use NE5534 instead of TLO71

Regards
Manoj
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