EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Experimentonomen on July 04, 2013, 01:54:07 pm
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Hola!
I used to be a member here a few years ago but im not sure if i cancelled my account or if it was suspended due to inactivity but it seems my mickname was still available to use.
Anyways just wanned to share my latest project, a stereo amplifier of the Class D veriety. Its been a long road but i was finally able to make both modules run together without dramatic increase in noise, and i've come to the conclusion i wont be meeting any EMC standards unless i go full SMD on everything.
Schematic:
http://i.imgur.com/M2DHewv.png (http://i.imgur.com/M2DHewv.png)
And a video, i's sorry about the choice of music and rather crappy camera mic :-[
UcD CLass D Amplifier project (https://www.youtube.com/watch?v=asC3zPaB9mY#ws)
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I bet you had a lot o fun ripping those Erricson DC-DC converters from a communication center (?).
Alexander.
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Actually i bought them new.
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love the bench, keep it up!
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The video has been removed by the user? :-//
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I need to move all videos and pictures of this to a different location after an incident on another forum which i no longer wish to share my work with, so the pics and vids will return in a few days.
Some members on some forums just make me wanna :rant: all day long |O
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Christ! What happened?
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I'm not gonna bring it up here, just gonna upload the stuff elsewhere and move on.
Schematic and video back up.
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Schematic:
http://i.imgur.com/M2DHewv.png (http://i.imgur.com/M2DHewv.png)
Outstanding job! Your circuit design - an open-loop comparator with complementary outputs driving a bootstrapped half-bridge MOSFET driver IC - is extremely elegant, and neatly sidesteps the stability problems usually encountered with trying to close the loop around the output.
Some things that might help in future iterations:
1. You ideally want the turn-on and turn-off times of the switches to be the same in a Class D amp (to minimize intermodulation and harmonic distortion products), thus the inclusion of the turn-off diodes across the gate resistors - which are generally good in a SMPS application - could be bad here. I would try removing them and dropping the gate resistors to 10-12 ohms. You will then need better bypassing of the supply voltages to the MOSFETs as a result, though (try adding 100uF of electrolytic a few cm away and 1uF + 100nF ceramic right at the MOSFETs).
2. The output inductor in a full-range Class D amp needs a core that is capable of handling some level of DC bias - not because any DC is present, but because the low end of the audio frequency range is tantamount to DC for most ungapped core materials - and the windings must have minimal interwinding capacitance. Often the first requirement (ie - needing a gapped core) conflicts with the second, so it could be beneficial to split your inductance unequally across two different inductors so that you will present an inductive reactance to a much higher frequency (this is important to prevent tweeter burnout). As for the core material itself, while it is tempting to go with powdered iron because it is cheap, a better/more stable material like permalloy powder (ie - Sendust, MPP) would probably be worth the expense.
And hey - never apologize for your taste in music. Other people don't have to like it to hear how well your amp is working (though, to be fair, that does help... along with not relying on the camcorder's mic... ;D )
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The inductor used is actually specifically designed for class d amplifiers, manufactured by CoilCraft.
Im not sure about removing the diodes, when you look at the circuit for the philips UcD class d, its gate drive circuitry is done in such way that turn-off is faster than turn-on, atleast as far as i can tell. There are already capacitors right next to the mosfets, small 1µF X7R ones right at the mosfets on the bottom and a set of 1000µF lytics as close as you can physically put them.
I do however agree that the board layout is not the best and there are so many bodges on these modules than im gonna cad new boards at some point.
http://www.nxp.com/documents/user_manual/UM10155.pdf (http://www.nxp.com/documents/user_manual/UM10155.pdf)
A pic of both channels: http://i.imgur.com/zzHj0ue.jpg (http://i.imgur.com/zzHj0ue.jpg)
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hi my friend, you can send model of ltspice IR2110.asy to my email?