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Class D Switching Power Amplifiers and Power D/A conversion

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Old 1st September 2012, 08:53 AM   #11
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Take a bread board and start with philips ucd and dont attach fets untill you think that every thing is clear use 24volts supply for start up...and use slow fet like 250n....on philips said you can see R9 330 ohms resistor....place a differential resistor instead....you get all fine
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Old 1st September 2012, 09:28 PM   #12
stewin is offline stewin  Kenya
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Originally Posted by darkamikaze View Post
@stewin

I'm not sure whether to go UCD or nonUCD as I'm not entirely sure what that means... but I have been snooping for quite sometime and I've looked at some of those threads. Unfortunately some of them hosted schematics or posted links elsewhere that they're no longer available.


Thanks everyone for the advice!

in your schematic please replace all diodes with high speed ones e.g 1n4148 and d4 and d12 make sure you use mur120 or uf4007 to be on the safe side.

q11 use tip41 or bd139 .


http://www.diyaudio.com/forums/attac...ip-capture.jpg

Last edited by stewin; 1st September 2012 at 09:32 PM.
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Old 4th September 2012, 07:57 PM   #13
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Just finished swapping out those diodes with the ones you requested. I still feel like I set something up wrong since my output is always a constant 35V or is that how it is on transient solver?


anyways hopefully tonight I can mess with it more and figure out what I can do. Thanks
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Old 5th September 2012, 08:46 AM   #14
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1N750 is only 4V7 I believe, you need more like 12V zener
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Old 5th September 2012, 08:51 AM   #15
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Also I think 3.9M and 5.6M are understood as a 'mili' by many simulators, go 3900k or 3.9Meg
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Old 17th September 2012, 07:12 AM   #16
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Alright, so I've been working on my amplifier again and also a replicate of the Phillips UCD.

I think I figured out why my output is always just my power supply voltage. I've been taking the voltage reading AFTER the inductor as opposed to before it. (Attached is the results of taking the readings of input v. output before inductor. The Philips UCD schematic is attached a page back.)

I also have my own class D design going as well which is attached below (2nd picture. Results 3rd picture) Let me know what you guys think! The driver portion of the design was taken from diyaudio's very own stewin. Thank you very much and I hope it's okay X_x.

I still have to figure out how to tweak it so that it's in line with my professor's specifications but I think this is a start for me .
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Old 10th November 2012, 01:21 AM   #17
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Hi Guys,

So I finally bread boarded this circuit (attached below is the updated schematic).

I've tested having an input from a Function Generator and the output to a speaker. Tested some freq from 20Hz to 10kHz which you can hear the pitch sound.

My problem now is figuring out how to get an audio signal in (perhaps my cellphone's headphone jack?) as the input.

I bought a 3.5mm jack (CA-2205 Tensility International Corp | CP-2205-ND | DigiKey) and I've tried plugging my cellphone in, (Red wire as input, blacks to ground. I believe the smaller black is for another channel..)

The problem is I'm not getting any sound. I'm guessing my cellphone does not output voltage ? X_x I'm not entirely sure how to work with the 3.5mm as I've never worked with one before. Any help would be appreciated!
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Old 10th November 2012, 04:01 AM   #18
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Can try something like this. Not *exactly* discrete, but I think of comparators as time-savers rather than ICs.
http://t3sl4.dnsdynamic.net/Current%20Mode%20Buck.pdf

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Old 10th November 2012, 04:58 AM   #19
stewin is offline stewin  Kenya
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Originally Posted by Sch3mat1c View Post
Can try something like this. Not *exactly* discrete, but I think of comparators as time-savers rather than ICs.
http://t3sl4.dnsdynamic.net/Current%20Mode%20Buck.pdf

Tim
for such low wattage the schematic is complecated maybe the link can be considered an option Ultra Simple Class D
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Old 12th November 2012, 10:38 PM   #20
tomi is offline tomi  Wales
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That's one hell of an ask for an undergraduate project - certainly far more ambitious than anything I was ever asked to contemplate at university.
A response to 100kHz seems barely feasible - surely that'd take your switching speed close to 1MHz or even beyond. Good luck & keep us posted!

On the subject of valves (or tubes), I'm sure I remember reading about PWM choppers built from valves being used as VCAs before the advent of transistors.
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