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The news D-Amp DLS3000....

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kASD

kASD

Member
Joined 2004
Eva said:
Workhorse, I recommend you to build a simple adjustable switching circuit allowing to measure inductances and saturation currents, if you don't have something similar already. Standard LCR meters and the like are not suited at all for gapped ferrites (or iron powder), they will always provide an erratic measurement.
Click to expand...


I am experimenting with Gapped Ferrites yet ! :D

Let you know the resultant outcome very soon....

K a n w a r
 
Eva

Eva

Member
Joined 2003
Two quick prototype pictures. Vertical board is gate driver. Heatsink and IGBTs are under the horizontal PCB (only a pair of TO-220s currently mounted):
http://eva.eslamejor.com/t_sine19.jpg
http://eva.eslamejor.com/t_sine20.jpg

Capture of 10Khz output at the onset of slew rate limiting with 60V single power supply and a 4 ohm load. Shows output voltage and inductor current at 20mV=1A:
http://eva.eslamejor.com/t_sine18.gif

Note that this is not designed as an audio amplifier but as a full bridge low frequency motor driver that must operate on 330V DC single rail and provide 20A rms overload-proof output with little EMI and dissipation (they even want it without fans!) The output filter resonates at 3600Hz, yet the output is kept flat within +/-1.5dB up to 10Khz independent of load.

I use 60V for most tests since it's more comfortable to the touch than 330V. Switching spikes seen on the output voltage waveform are mostly due to filter capacitor inductance (400V wound foil types are not as good as the 63V or 100V stacked foil ones used for audio). Small spikes seen on current sense waveform are due to inductor parasitistic capacitance.
 
Eva

Eva

Member
Joined 2003
Oh, it's intentionally done that way, frequency is dynamically controlled to achieve the lowest switching losses without exceeding a certain amount of output ripple voltage, and to score better in EMI emission tests. It will drop to 25Khz under normal operation at full load, as in practice the amplifier will be hardly required to produce any output above 1Khz.

I would operate it in a different way if it was intended for audio, as music allows for very high switching frequencies without too much losses due to its low average power content.
 
Eva

Eva

Member
Joined 2003
With the average current mode control scheme that I'm employing, spread spectrum is not advantageous for audio as the poles introduced by the current amplifier are shifted down as frequency is decreased.

My frequency control is based in keeping inductor peak to peak current ripple constant. That would cause the frequency to shift to zero near clipping, so a lower limit has to be put. The limit is currently not well implemented as it becomes quite complex to achieve in the analog domain, but I will use a PIC with D/A for that (which I need for other duties anyway).
 
Eva

Eva

Member
Joined 2003
The way in which the current amplifier is designed makes core saturation impossible despite the load applied. Shorting the output to the rectified rails or to the mains input is also allowed without problem. Core saturation is only possible if the control circuit ever becomes faulty.

I was asked to design an industrial four-quadrant power supply, not an audio amplifier. It has to be reliable and provide some basic fool-proof features :)
 
kASD

kASD

Member
Joined 2004
kartino said:
Hi Kanwar, seems that you facing problem as me. If you want to step to commercial amp then yuu must spent lot of money to hunting best material. Like fredos did.

May in copy your amp? :devily: :Pirate:
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Hi Kartino,
I am already in professional amplifier manufacturing business for more than 7 years...
Money isn't problem, But the accessibility is much more important , hi quality cores arenot available in our country...


K a n w a r
 
kASD

kASD

Member
Joined 2004
fredos said:
Anyways, I think we can do better than lot of big company with lot of money for R&D!

Fredos
Click to expand...

Hi Fredos,

Same situation is here, yes we could do much better than other bigger players!

You must have become rich enough to buy bulk stock of spare parts for your R&D....


fredos said:
He guy look at this!!!! Really good price!

http://partsandkits.com/kitsandparts/toroids.asp

fredos
Click to expand...

That Link was great Fredos, thanks alot....

Cheers,
K a n w a r
 
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