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Old 22nd April 2011, 11:25 PM   #981
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Quote:
Originally Posted by Dzony988 View Post
Put Elkos near by ouptut fets. For that PCB put them under board, 470uF will be good. Change cap of 330p to 100p, and swiching freq will be around 260KHz. Output filter from 30uH to 20uH and cap from 1.5uF to 1uF.

My amp works good with that changes, even on 2ohm load and IRFP240 on +-50V
Ty Dzony ,
How much watts are you getting??

So you now are using irfp250 or IRFB4227 ?


Quote:
Originally Posted by nigelwright7557 View Post
Perhaps the HIN and LIN inputs are too high a voltage and latching up the 2110 ?
The inputs are getting 11v , the supply its 12v , the 1 logical its about 9.5v to 12v.

ty

Last edited by electroconico; 22nd April 2011 at 11:29 PM.
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Old 22nd April 2011, 11:35 PM   #982
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For that volatage +-50V I use IRFP240PBF from Vishay. But tumorrow I will build with IRFB4227 for +-70V on 4ohm load. Use IRFB4227, that are one of the best fets for class D, but first use cheap fets, and when amp works good, then change to IRFB
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Old 22nd April 2011, 11:43 PM   #983
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Quote:
Originally Posted by electroconico View Post
Ty for repply.

My first try was with the irfp250 , but i haven´t more of them. I know irfp460 its slow but i havent any problem with the mosfet stage.

I use mpsa92 instead of 2n5401.I checked the footprint and it´s ok.

(irfp250)I had one prototype working a long time , but when i did the test to get max power the power supply blows up again.(12v supply Zener-transistor ,Opened Zener).I measure atleast 150W@4ohms (4ohms speaker and 6ohms pure resistor.)


I thought that i got bus pumping effect when i was trying bass tracks. But now trying with 1Khz signal it happened again.
I measured all supplies.
10,000uF by rail

I use bypass diode , mur120
Snubber 100pf-10ohm , I did not see spikes in the output stages.

Also the amp its oscillating at 150Khz

I read all thread , spanish and english threads.

I change the Rg resistor 27ohm to 22ohms.Whit the 12v external supply to the ir2110 the signals looks better less noise and oscillations.

The pics below are with irfp250.

i´ll upload more captures soon.
What is the resistor before the 12V zener? You should check it. At your schematic its 4k7, but it should be 6k8 for you supply rail (but that should not be an issue).
If you have a FET with high gate charge you should not decrease the turn on resistor. At higher temperature, the fet usually gets slower, so cross-conduction rises. Ant it can kill not only the FETs, but driver, and every other.
Put some scope probe on the supply rails, and see them at load condictions. You have absolutely no decoupling, they will be extremely noisy. Then anything can happem...

Your gate signals are really messy, but switching signal seems nice.

You must put the oscillation frequency up over 200-250kHz. I looked the spanish forum, and from the schematics (as I cannot understand spanish) nobody tried the normal connection of the comparator, and even raising switching freq. I haven't seen any input stage with differential inputs.
(offset is a tiny problem, and for example differential inputs should decrease it too, and I've seen lots of photos with air-coil inductors... forget them. Most of all the inductors heat up because low switching frequency and the bad filtering)

Rule of tumb: switching freq should be a decade higher then corner freq, to ensure good filtering of carrier signal.

Dzony988: output filter is good as is (for 4-8 Ohm load), with your values, the corner frequency incereases. For 2 Ohm you should redesign the filter: 20uH and 2.2uF would be better.
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Old 22nd April 2011, 11:47 PM   #984
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Quote:
Originally Posted by Dzony988 View Post
For that volatage +-50V I use IRFP240PBF from Vishay. But tumorrow I will build with IRFB4227 for +-70V on 4ohm load. Use IRFB4227, that are one of the best fets for class D, but first use cheap fets, and when amp works good, then change to IRFB
Well-well-well.
I did the same, tried with cheap IRFP240 first. Then with IRFB4227 for big power...
Now I even made some modules with IRFP250N ("el-cheapo" models), and I was surprised, I expected worse. The disspiation only became a problem at high loads.
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Old 23rd April 2011, 12:09 AM   #985
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Yes lorylaci

The resistor before the Zener its 6.8K.

After the mess i checked the components and the tip31c was shorted in emiter whith colector.Other times the Zener was opened or shorted.

I´ll try with better filtering in rails then i´ll post the results.

Ty again!
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Old 23rd April 2011, 01:39 AM   #986
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Default new pcb design with dc and current limit

Hi guys,

I think the trouble is they really understand how this amp UCD

and it is likely that the sequence of failure is that the transistor Q5 is set to short, and destroys the IR2110 IC with failure of the other components

as 5401 and the mosfet
I comment on how important this good design is to choose well the first mosfet value
vds max 20% of the value to be used in vcc

and consider it very important Qg value always less than 100 Nc

this depends on which ic not going to burn 2110

I recommend it because it works great is to put a 12 v source independently of negative v vcc pin 3 of IC IR2110 is removed so the transistor Q5 and heater and many possibilities of failure of the amplifier

L1 coil recommend an air core is much more linear at different loads and anyone can do it. how?

16 gauge wire about 56 laps in a diameter of .750 "and diameter of them

the capacitor C4 is very easy to get from any source atx is in series with the main transformer and is proper for high Frequence work

Soon I will put a PCB to Protect DC and current limit

all greetings from MEXICO
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Old 23rd April 2011, 07:39 AM   #987
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last picture shows cross conduction... first few have a lot of oscilations, as waveforms show
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Old 23rd April 2011, 07:42 AM   #988
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Quote:
Originally Posted by pedro1958 View Post
Hi guys,

I think the trouble is they really understand how this amp UCD

and it is likely that the sequence of failure is that the transistor Q5 is set to short, and destroys the IR2110 IC with failure of the other components

as 5401 and the mosfet
I comment on how important this good design is to choose well the first mosfet value
vds max 20% of the value to be used in vcc

and consider it very important Qg value always less than 100 Nc

this depends on which ic not going to burn 2110

I recommend it because it works great is to put a 12 v source independently of negative v vcc pin 3 of IC IR2110 is removed so the transistor Q5 and heater and many possibilities of failure of the amplifier

L1 coil recommend an air core is much more linear at different loads and anyone can do it. how?

16 gauge wire about 56 laps in a diameter of .750 "and diameter of them

the capacitor C4 is very easy to get from any source atx is in series with the main transformer and is proper for high Frequence work

Soon I will put a PCB to Protect DC and current limit

all greetings from MEXICO
Air coils are big, ineffective, and radiate noise.
Because they are big they were able to dissipate the loss because of the high current (because of low switching freq).

Since this is an UcD amp, the feedback is after inductor, so every non-linearitiy of the inductor is compensated by the feedback. Gapped ferrites also very linear until 80% of saturation. Iron-powder cores are less linear.

So chosing air-core inductor for linearity is stupid. I think they chose it because any other could not dissipate, mainly because the low switching freq. A bad solution for a bad choice.
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Old 23rd April 2011, 08:36 AM   #989
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Now I'm making this pcb .It is like 80% done.
I have to check the gnd returns

Ty luka, I´m working on it.
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File Type: png ucd new pcb.png (108.2 KB, 1049 views)
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Old 23rd April 2011, 09:52 PM   #990
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Gate signal is closest to mosfet.
Power supply line is direct on mosfet pins.
Capacitors are closest to Drain and Source pins.

What do you think about this new pcb routing?

Is there anything to change ?

I´ll apreciate your comments and tips.

ty
regards!

P.D. I´ll add some test points to pcb.
Attached Images
File Type: png pcb routing.png (127.9 KB, 989 views)
File Type: jpg new pcb amp.jpg (47.3 KB, 969 views)
File Type: png sch mpli ucd modificaciones v7.png (35.8 KB, 976 views)

Last edited by electroconico; 23rd April 2011 at 09:55 PM.
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