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Old 9th July 2011, 02:50 PM   #1
epilot is offline epilot  United States
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Default Class D for ultrasonic!

Hello guys,

I need an at least 150W or higher class D amplifier capable of working almost linearity up to 60KHz (the frequency response I expect is from 30KHz to 60KHz). If needed to be mentioned, I do not care of the audio frequencies for it (I.e 20Hz till 20KHz). I do not mind if it works from several Hertz till 60KHz or linearity or just from 30KHz till 60KHz because I want it to drive a big piezo load at ultrasonic range (as already mentioned from 30kHz to 60kHz).
DO you guys kindly know any brand or module to do so please?

Thanks a bunch for any help or suggestion
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Old 9th July 2011, 05:30 PM   #2
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Hello,

I m not sure what your application is. To scare off some mosquitoes, I think it is enough to produce some square wave at these frequencies (i. e. the generator can also be the amplifier for much simpler overall design)...
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Old 9th July 2011, 05:45 PM   #3
epilot is offline epilot  United States
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Quote:
Originally Posted by ViennaTom View Post
Hello,

I m not sure what your application is. To scare off some mosquitoes, I think it is enough to produce some square wave at these frequencies (i. e. the generator can also be the amplifier for much simpler overall design)...
Thanks sir,
No mosquitoes repeller I meant!

The system which I want to construct is some kind of imaging system by ultrasonic. It needs a lot of piezo transducers all in parallel to create a very powerful output. The impedance of each transducer is almost 500 ohms, So using 100 of them or even higher will reduce the impedance to less than 5 ohms.
Any way I prefer to use a class D amplifier for this project if possible.

Thannks
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Old 9th July 2011, 06:40 PM   #4
ssanmor is offline ssanmor  Spain
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Please keep in touch with us (info@coldamp.com) We have a lot of experience in custom designs.
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Old 9th July 2011, 08:55 PM   #5
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Class d usually has an output filter which will lose the 60KHz.

You might have to buy a class d amp and change the output filter to get it upto 60KHz.

You would also need a class d amp with a high class d frequency to get a good resolution at 60KHz.
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Last edited by nigelwright7557; 9th July 2011 at 09:15 PM.
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Old 10th July 2011, 03:41 AM   #6
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Yes, you need a Class-D design with a >600kHz carrier and an output filter properly calculated for your needs.

For a 5R load 15uH + 500nF will give a Fc of ~58kHz and be will be about -50dB @ 1MHz.
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Old 10th July 2011, 08:28 AM   #7
AP2 is offline AP2  Italy
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Hi,
I agree with theAnonymous1,
And add: If your signal input is sub-modulated or sin continuos, requires power re-calculation or use a 500w-600w power amplifier for 150w output.
Also, You can add a second outbound filtering, to reduce the residual HF.

Regards
Roberto
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Old 10th July 2011, 12:57 PM   #8
ssanmor is offline ssanmor  Spain
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It all depends on your requirements (THD, supply rejection, etc.) It is not only a matter of the output filter.
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Old 11th July 2011, 06:24 AM   #9
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Yes, exactly ! Could you describe what your Signal looks like ? Is it always the same freqency ? The same Level ? Or even both ?

If even only one of these apply then it might be much easier to use an application specific amplifier type.

Regards

Charles
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Old 5th July 2013, 06:36 PM   #10
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I am trying to develop a 100W/55khz for ultrasonic scalpel.

I am using an IRS2092 with IRFB4019, 10uH/.1uF filter. (500Khz switching)

In my first prototype with no load the amp works fine, but I need to put a transformer in the output of the amplifier to step up the 72Vpp to 300Vpp the low side mosfet burns.

Any hints ? Probably something related with the low impedance of the first wind.

Any solution ?
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