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Class D Switching Power Amplifiers and Power D/A conversion

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Old 26th August 2010, 04:21 PM   #471
Andy F is offline Andy F  Spain
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I mean V1 and V2 on the schema, it is 18v, for a 200v fet you can play with higher voltage (maybe 60 or 70v)
IRFB5620 is a better mosfet for class D if you get the model and has 200v limit also, he must add some dead time control on Ir2110 input or the fets will go in cross-conduction, the simplest way is to add a series resistor and diode with a cap to common(the Ir2110 has a schmidt trigger on input to square the signal so you can save some gates), no problem for simulation but risk of sparks and smoke on real application without any dead time provision.
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Old 26th August 2010, 04:55 PM   #472
savu is offline savu  Romania
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hello andy,

how about inductors in the switching node just before the output inductor and some clamp diodes to the + and to the -

that should solve cross-conduction problems.

regards,
savu
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Old 26th August 2010, 06:53 PM   #473
Baldin is offline Baldin  Denmark
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Seems like a lot of suggestions are coming up again
ucd 25 watts to 1200 watts using 2 mosfets

I agree with Andy that you have to measure prop delay at some more realistic voltages 18V seens a bit low ....

Andy; about the dead time .... In my current amp I did provide dead time using 4 gates at the input ... but it is disabled as the gate resistors produce enough dead time ...
And the circuit as shown in the post mentioned abowe it ran ok without any troubles at +-30V without heat sinks etc. ....

IRFB5620 is a very good choice for "low power" applications ... say up to at least 200 W ....
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Old 26th August 2010, 08:08 PM   #474
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I use 18V because i dont need more than 25 watts, my speakers are rated 20W max.
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Old 27th August 2010, 02:13 PM   #475
savu is offline savu  Romania
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i sugest powering the amp at higher rail voltage and limit the input signal.
that way the amp will behave better.
better thermal, better thd, better dinamics (higher dv/dt or slew rate).

regards,
SAVU
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Old 27th August 2010, 04:25 PM   #476
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Can anyone explain this phenomenon ? I swapped the transformer to get 2x35V instead of 2x18V, regulators for the comparator are fed 15V from a separate winding. Everything is fine until i bring the amp into run, then the gate driver starts sucking all juice it can, making the amp give a brief pulse of audio output.

I even tried with a 12V 4A smps, and even it detects a short as soon as the amp is turned on and starts pulsing = pulsed audio output.

Wtf is going on here ? when its turned back into standby, the IR2010 stops pulling current.

The pulsed audio output suggests that everything is working, but the pulsing indicates some fault i dunno what it is.

Im stumped
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Old 27th August 2010, 04:52 PM   #477
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With a battery driving the IR2010, the amp works no prollem, but a smps or 7812 doesent wanna drive it.
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Old 27th August 2010, 05:42 PM   #478
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This video shows the weird behaviour:
YouTube - class d amp weird behaviour
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Old 27th August 2010, 08:29 PM   #479
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Increasing the voltage was a bad idea, it lasted around 5 minutes before the high side fet overheated and lifted its lid, even the plastic insulator had melted itself stuck to the tab. Hopefully the speakers survived, tho i heard weird noises from them after i ripped the plug outta the wall, so they have be dead too.
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Old 27th August 2010, 09:25 PM   #480
Pafi is offline Pafi  Hungary
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Increasing the voltage was a good idea, because it showed that the design is basically wrong.

If you need only this low power, then you could choose much higher performance devices, like TAS5162, etc...
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