| Variac |
| This is a thread for the discussion of the design of class D amps, not discussion of kits or modifying existing amps. |
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| raintalk |
I can't stand to see and empty thread :umbrella:
I think this is the first Class-d amp: US Patent 03011025 in 1961 by Herbert W. Sullivan
A tube amp, and the parts look to still be available today.
Go to: http://patft.uspto.gov/netahtml/PTO/search-bool.html
And search all fields for 03011025
Select the date: 1790 to present |
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| odnaizutra |
| Do you think a full bridge,single supply 130v ,4irf260,2 ir2010,lm319 and 4060 giving 228khz a good begining? |
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| Genomerics |
Since this thread is about Class D design issues......
The Ramblings of a Mind Gone Wrong
A journey into the ins and outs of what Class D might be about from the perspective of someone who is trying to work it out.
DNA |
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| Groman |
| Do you know any ebook or web page of class D amplifier for beginners? |
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| TJNII |
| It's tough. I've been working on one based off a PWM design for a year now and it's kicking my butt. I've got a prototype in the other room that plays, but doesn't sound too good and has a problem with ultra-low frequencies on the output. One of the few amp designs you'll come across that pass the signal through nand gates and optocouplers. On the upside, I think I have designed a successfull output stage for it. (Gotta take pride in the small victories.) |
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| richie00boy |
| There is already a thread discussing the design, classd4sure started it a year or two ago, full of useful info. Bit biased towards UcD though I believe. |
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| Electrone |
| quote: | Originally posted by TJNII
has a problem with ultra-low frequencies on the output. |
Check the power supply for the high side switch. It may be dropping too low if it is normally refreshed by bootstrapping. |
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| BWRX |
| quote: | Originally posted by TJNII
It's tough. I've been working on one based off a PWM design for a year now and it's kicking my butt. |
Hi TJNII. Care to share more about your design with the rest of us? |
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| TJNII |
| quote: | Originally posted by BWRX
Hi TJNII. Care to share more about your design with the rest of us? |
I'll tell you all about when I get it working right. ;)
I think it has a design flaw in the control circuit, so I don't want to go into too much detail right now. |
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| Variac |
I think that BWRX meant that if you shared the design some members could suggest what the design flaws might be.
Sounds like you want to tryt o get it working well on your own? |
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| BWRX |
There are lots of folks around here that may be able to help you find the design flaw, if it exists. Unfortunately that's usually easier to do with a schematic ;)
EDIT:| quote: | Originally posted by Variac
I think that BWRX meant that if you shared the design some members could suggest what the design flaws might be. |
You read my mind! |
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| TJNII |
Well, ok. Since you asked nicely.
Basically it is PWM based off a triangle wave. I generate a triangle wave, and then bias it with an offset voltage to create two waves, one biased positively and one biased negatively. The seperation between them is my dead time between the pull-up fets being energized and the pull-down fets being energized so both fets arn't on at the same time. I then compare the input to these two waves, one wave for pull-up and the other for pull-down. My output stage is an H-bridge so any diffence in turn on/off times for my high side and low side switches is nullified by the fact that (ideally) the pull-up and pull-down current paths are (ideally) identical (ideally). I've also got a minimum pulse width circuit on there, to keep the bootstrap capacitors charged when it is driven into clipping.
That's it in a nutshell. I don't want to post really specific details or schematics yet because I haven't hit a wall yet (I like to solve my own problems, it's the fun of it).
* I know I've roasted my output stage when I turned the dead time control down too low, dissipated around 250W in fets with no heatsyncs. It isn't extra crispy, but damage was done. I think the subsonics are from this because they started after I zapped them
* I know something was odd in the output stage even before that. One fet just wasn't acting right. It doesn't look like a design problem, so I need to look into that.
* I was looking at a class-D design on this board and saw some ideas in the feedback loop I want to steal. I may rip them off.
| quote: | Originally posted by Electrone
Check the power supply for the high side switch. It may be dropping too low if it is normally refreshed by bootstrapping. |
I'll try that next time. I don't think it is the problem as I took steps to prevent it, but it is an easy test.
Also, I have to start moving so in a few days it is going in a box and won't come out for a month. So I don't want to get really into it now.
And believe me, I'll post details when I get it working. And if I can't, I'll ask when I've run out of ideas. I had this prototype sounding good under slightly different conditions. I just need to test more and be more scientific about it. ;)
My first comment was just that: a comment. I was new and felt like commenting. Pardon me. |
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| Variac |
Well, welcome, and we look forward to future reports!:nod:
Variac |
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| nitrate |
Hi all,
I've been building amps for some time now and i have two very nice sounding prototype classD designs. One is a carrier based, and the other self osc. The problem is i would love to take one of the designs further and complete into a nice stereo amp for my daily amp needs ( the commercial amp in my living room is on all the time i'm in and is getting a bit tired ). The issue i have is this, EVERY CLASS D I BUILD HOWEVER GOOD IT IS ALWAYS ENDS UP DEAD EITHER BY STARTUP PROBLEMS OR BAD LOADS! I know that if used properly they are prob very reliable, but i NEED SOME KIND OF EFFECTIVE PROTECTION against overdrive, overcurrent, bad loads, startup and stall conditions. No matter how much i try i cannot impliment an effective protection system, this is the reason why regretibly i still cannot enjoy these wonderfull sounding amps in the real world, only on the test bench or at occasional parties.
Have any of you DIYers have similer issueswith your designs??
If so and you found an effective way of protection i'd love to hear about your experience.
Regards
Mad.P |
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| Andrew Eckhardt |
| Has anyone endeavored to come up with a multiphase PWM amp, self oscillating or clocked? This seems to be the solution to the band limiting of moderate switching speeds and the loss of pushing it. There is an obvious difficulty in tuning each phase leg gain to the average of the rest without servo, but it seems possible. With eight phase legs, each one could run at a cool 500kHz, with smaller output transistors, and the total switching frequency would be 4Mhz. Available bandwidth would rival the best linear amplifiers. |
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| Dave Z |
| Yes Andrew, Your should check out Karsten Nielsen's work |
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| wapajk |
@nitrate| quote: | | EVERY CLASS D I BUILD HOWEVER GOOD IT IS ALWAYS ENDS UP DEAD EITHER BY STARTUP PROBLEMS OR BAD LOADS! |
You should try IRS20955 split supply version or IRS20124 single supply version. They are mosfet drivers for high and low side, designed specific for class d amplifiers and have integrated protections for power mosfets.I never had start up problems with my amps.
maybe fets get their supply before oscillator section has started!(this can short out output mosfets to load or to supply rails...)
What topology of mosfet drive do you use,
is there soft start implementation?
What is the nature of start up failure?
... |
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| richie00boy |
No it wasn't that, it was a specific thread about designing and building class-d amp from scratch. Maybe I will try to find it when I have more time.
PS I can see classd4sure is "account disabled" was he found to be a sock puppet or something? |
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| nitrate |
Wapajk,
My driver topology consists of MAX262 drivers driving the fet directly and magnetic isolators providing the drive signal to the max i.cs. The high side is powered off a bootstrap pump. Dead time is set elsewere, not relient on gate capacitance/resistance. It is not shoot through currents destoying the fets, i'm pretty sure it is the low frequency of startup causing too much current to be passed through the output filter. Also when dodgey loads are put on the output i think this is altering the filters responce causing the same thing. After all speaker loads are reactive and the filters parameters are somwhat dependent on the output load. All these factors combining gives rise to the failures. I will do more research on this and sort things later when i have more time, i'm really busy with other things at the mo. I have succsessfully created electric motor controllers with the same topology that can throw lorry starter motors around the bench so i'm convinced the problems are to do with frequency/filter interaction. I even once tried using dc-dc isolated converters instead of bootstrap, and implemented the old resistance in the gate deadtime instead of external control, it worked exactly like all my other output stages ( i must admit much simpler to implement but more expensive ) but the same old thing. Too much stress and bang!.. or just failure on startup. I must admit however the breadboard designs prob arnt helping things and could possibly be the root of the problem :cannotbe:
^^^^^^^^^ I know, i know, breadboard.. pls don't shout at me lol
Anyways, nice to visit the D class.. i'm a great fan of this topology..
LaterZ
Leigh |
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| wapajk |
Sorry, maybe I've missed something. I looked at MAX262 datasheet - "MAX262 : uP Programmable, Universal Switched Capacitor Filter"
Did you mean MAX232 or something else.
I'm a bit confused here.
MAX232 is by no mean good driver for mosfets. Note that it has short-circuit current of only 60mA. that is to low for class D and also typical output swing of +-7.5V isn't to good(note that swing is rated under normal operation into load of 3kohm)
Also magnetic coupling isn't to good for gate driving in Class D(it can be ok if done correctly but will never be better than hi side and lo side mosfet drivers like IRS2110 or irs20955,irs20124,irs2011...)
maybe you could post schematic. It will help greatly!! |
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| nitrate |
Opp's, sorry i meant MAX626, and the magnetic isolator in question is NVE's IL711-2. Both are pretty quick and allow me great flexibility in design, i also use them for other stuff too so that sort of influences my component choice :-)
Some of my work is here
http://www.diyaudio.com/forums/show...9138#post729138
... not sure if the schematics were up to date though. Should give you an idea of whats going on or rarther was lol
Leigh |
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| ChocoHolic |
My impression is that more than 50% of the unsolved DIY headaches in class D are caused by te difficulties of proper timing, proper gate drive control and parasitic resonances.
For a first rough idea about dead time you can watch both gate signals simultaniously while applying
zero volts rail at the power stage. As long as the rail is zero you do not need a differential probe to watch the high side gate and you will also not burn the power stage.
Only if these signals are OK, then it makes sense to power up the rails for the power stage.
To get a feeling about the power stage ringing in any class D amp it is be helpful to watch the gate drives and halfbridge sloping in a load condition slightly above filter ripple current. Most simple method to generate such a load condition is to connect a resistor between positive rail and amp output. The resistor should have a value that the resulting DC is slightly above the filter ripple.
In troublesome designs it is a good idea to start with reduced rail voltage. Already watching the lower gate drive and the half bridge sloping in this condition is usually telling you a big story.
To find undesired resonances you should have a scope with 100MHz bandwidth or higher. Depending on components and layout most designs show heavy resonances between 30MHz and 100MHz.
Curing the resonances is possible by ceramic smd caps at the rail, RCL snubbers at the rail and most effective by RCL snubbers between drain&source. The L of the snubber is the parasitic L of the snubber geometry, which you must not ignore. Unfortunately. |
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| arif__anwar |
| would anyone be able to suggest a UcD design paper with a basic design and calculations so i can figure out how the thing works??..any help would be great |
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| unclejed613 |
| i found an early (1965) PWM in a IEEE circuit book. i built one of these about 20 years ago, and couldn't get it to work. i tried modeling it in LTSpice recently and found out why it didn't work when i built it. it needs DC bias on the input signal. |
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| exorcista |
I'm tendando to repair the amp SPL Dinamics ext-3000D, I had to reconstruct the entire power by replacing all IRFP064N is pilotaggi 2sa1275 transistors and other components, rebuilt part because board went to fire! wings all ok, a problem also found in secondary 4 final IRFP360LC short only that I can not finding is replacing with IRFP360 but nothing goes into protection led green then red, tolgo line end where I added the final 4 audio is always the same I realize that warms the pre-pilot that these integrated smd installed 7 +7 pin (symbol carteggiata how do I go back to its value) on bassetta the tolgo is finamlmnete only part that makes a sound type frying is I realize that the integrated pre 4556D warms a lot but I do not know where to buy it, the problem is to know the code dell'integrato sanded welded on basseta you know the code! then there are also two integrated covered by black resin but I suppose they are good!
modul DWM3640nhv_v30 , I serve the value of U2, U1 production for what it says IRF
His clones with the same chassis:
hifonics Goliath GX3000d
Ground zero GZPA 1.5000 SPL
E-Audio 3000D
American Bass VFL 200.1 |
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| fatihcol |
hi;
in board u1,u2 = ir21844s
u3 =tl072
u4 =lm211
d1,d3=12volt zener
sorry i'm little english
good luck |
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| Ouroboros |
| quote: | Originally posted by arif__anwar
would anyone be able to suggest a UcD design paper with a basic design and calculations so i can figure out how the thing works??..any help would be great |
The best place to start is Bruno's original paper to the AES.
A copy is available online at:
www.ciaudio.com/ucd_aes.pdf |
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| exorcista |
"DWM3640NHV_V30"
replaced the other problem I ic overheat njm4556 too! |
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| fatihcol |
| quote: | Originally posted by exorcista
"DWM3640NHV_V30"
replaced the other problem I ic overheat njm4556 too! |
njm4556 (u3) is hot because triangle jenerator. |
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| exorcista |
| njm4556 is the pre dell'RCA is too overheat even after 10 seconds from what may depend |
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| fatihcol |
| quote: | Originally posted by exorcista
njm4556 is the pre dell'RCA is too overheat even after 10 seconds from what may depend |
i' m repair today. g-z 5000spl same your amp :bawling:
amp's blow ir21844s an 360lc |
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| mhouston |
Is there a single Class D chip or module I can purchase, commercially, to make a complete amp from?
If so, from a musical point of view, what is the best chip or module? |
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| Jaimo |
check out 41Hz.com
I can't comment on the quality but I plan to purchase a kit as soon as I figure out what suits my needs best.
Cheers! |
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| mhouston |
| quote: | Originally posted by Jaimo
check out 41Hz.com
I can't comment on the quality but I plan to purchase a kit as soon as I figure out what suits my needs best.
Cheers! |
I thought the Tripath was Class T? |
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| Pashley |
| quote: | Originally posted by Groman
Do you know any ebook or web page of class D amplifier for beginners? |
There's one at http://sound.westhost.com/articles/pwm.htm. It was written by someone from Coldamp, a vendor of class-D amp modules.
For another module vendor's take, go to http://www.hypex.nl/ and click on "technology". |
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| BWRX |
| quote: | Originally posted by mhouston
I thought the Tripath was Class T? |
Class "T" is marketing mumbo jumbo. There is no such class. Amplifiers that utilize Tripath chips are class d.
There are tons of ICs one can use to build a class d amp. Search the websites of well known manufacturers - TI, ADI, ST Micro, National Semi, etc. If you want to dig deeper, search this forum for a while. There are some older threads that get pretty technical regarding design. |
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| mhouston |
The link is a no show! |
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| mhouston |
| Can you build your own class D from scratch? Any schematics. |
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| Pashley |
| quote: | Originally posted by mhouston
Can you build your own class D from scratch? Any schematics. |
Tripath make class-D amps on chips. You can get development boards from them. Companies like 41Hz.com sell kits for Tripath-based amps.
Quite a few of the big semiconductor companies -- at least TI, Cirrus Logic, Analog Devices, and National -- have class D products. Some are amp-on-a chip, others are controllers that expect external transistors to do the heavy work. Freescale (Motorola's embedded CPU business spun off into a separate company) have a controller that does six channels. |
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| unclejed613 |
| you can make chip based amps from scratch easily. discrete amps are much more difficult. there were some made in the 70's. they were only mildly successful. the earliest ones had very low switching frequencies of about 40-50khz. board layout is one of the biggest challenges in discrete designs. |
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| jaydeecee |
| quote: | Originally posted by mhouston
Is there a single Class D chip or module I can purchase, commercially, to make a complete amp from?
If so, from a musical point of view, what is the best chip or module? |
You can try this website. www.amplifier.co.uk
Have heared that this amp was put up against some Krell monoblocks driving Wilson Watts and it blew the Krells away. |
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| mhouston |
| Great link, thanks. |
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