Class D for ultrasonic!

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E

epilot

Member
Joined 2006
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:)
 
E

epilot

Member
Joined 2006
ViennaTom said:
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)...
Click to expand...

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
 
A

AP2

Banned
Joined 2009
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
 
E

ebeinecke

Member
Joined 2012
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 ?
 
gmarsh

gmarsh

Member
Joined 2004
Piezo transducers are almost always capacitive, your amp needs to be properly designed and compensated to drive one.

If harmonics aren't an issue, why not just drive the piezo with a simple half bridge and use a resonating inductor?

Sent from my Nexus 4 using Tapatalk 2
 
DUG

DUG

Member
Joined 2003
Use circuits like HF amateur radio amplifiers use (L and C) and match the load impedance to your source.

DIY inductive heating also uses impedance matching with line rectified supply to half bridge drive circuits.

High Frequency Induction Heating

You will end up with a sine wave in the matched power band ... don't try to use class D as a drive to PWM your 55KHz...go right to 55KHz as the power frequency.

IMHO

:)

Edit: gmarsh I did not see your post. :)
 
E

ebeinecke

Member
Joined 2012
Piezo transducers generally have capacitive behavior between the ressonance and anti ressonance area, actually I have a L for compensation in the second wind of the transformer, I manage to solve the problem by adding an output large series capacitor to remove DC current (2.2uFx250V).

I'll try to use class D amp due to its high efficiency and small heatsink.

My application is a 55Khz ultrassonic Scalpel for medical surgery.

Thanks for helping me :)
 
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