Perhaps bus-pumping should be considered. But my experience (three years now with Class-D) tells me that bus-pumping is not such a problem. I have been driving a couple of amplifiers 400W rms each on 4 ohms, from a single supply with "only" 20.000uF per rail with no traces of bus pumping (the contrary is true, rails dropped a bit 
When using it in bridge mode the problem is still more negligible. And even in stereo, you can always invert the phase of one of the channels and then re-invert it again at the speaker so power pumping at low frequencies is cancelled.
So I think it won't be any problem with that.
When using it in bridge mode the problem is still more negligible. And even in stereo, you can always invert the phase of one of the channels and then re-invert it again at the speaker so power pumping at low frequencies is cancelled.
So I think it won't be any problem with that.
Workhorse said:
Hi Kanwar,
I'm also concerned about bus pumping on this circuit but my advice is to use big caps because that is the most easiest and most popular but expensive remedy at the moment.
But I am thinking to design a fast acting SMPS that will complement on my circuit. I have a positive feeling that if the supply is equipt with fast feedbackt response to compensate the fluctuation of the bus then this might be another solution..
I want to be the first one to try my circuit so that if everything is fine then I will publish the result....But I'm also worried that I can't be able to finished it because my employer calls me for duty to join their vessel..So my response to most of your post will be limited
Regards
ledmania
Pierre said:Perhaps bus-pumping should be considered. But my experience (three years now with Class-D) tells me that bus-pumping is not such a problem. I have been driving a couple of amplifiers 400W rms each on 4 ohms, from a single supply with "only" 20.000uF per rail with no traces of bus pumping (the contrary is true, rails dropped a bit
When using it in bridge mode the problem is still more negligible. And even in stereo, you can always invert the phase of one of the channels and then re-invert it again at the speaker so power pumping at low frequencies is cancelled.
So I think it won't be any problem with that.
Well, thats good news to me because I'm really concern about the outcome of this circuit when powered by mains..But I'll bet that this is a real capacitor sucker!!! LOL!
regards
ledmania
Hi guys,
I have an alternate schematic that may satisfy your hearts content regarding the location of the NFB.
You can choose wether you prefer to put it before or after the filter.....I study the result of the cicuit after a contemplative analysis before I send this to you for review. I'm sorry that I still dont have a circuit simulator so, the result is only based on my own experience in measuring "pulsed dc voltages" when I'm playing with TL494 as class D sourse about a year ago.
You will notice from the circuit that the NFB is connected before the filter with R14 and R15 as the voltage divider. I choose 2ma. of current passing thru it to get a standard value of R. You will also notice that the required 2V is unchange but the voltage output from the leg of the power fets is now 12.5V referenced to global ground (g.g).
This 12.5V is base on my analysis that "@ 50% duty cycle"(no audio),you will meassure there 1/2 of 25V referenced to g.g...So, it will swing max of +/- 12.5V reference to g.g. and +/- 25V across the speaker reference to neutral.
Of coarse these are the theoretical maximum values that losses or Vdrops are not included and duty cycles can stretch at 100% which is not possible to TL494.
So there you go...
LO and behold..........
I have an alternate schematic that may satisfy your hearts content regarding the location of the NFB.
You can choose wether you prefer to put it before or after the filter.....I study the result of the cicuit after a contemplative analysis before I send this to you for review. I'm sorry that I still dont have a circuit simulator so, the result is only based on my own experience in measuring "pulsed dc voltages" when I'm playing with TL494 as class D sourse about a year ago.
You will notice from the circuit that the NFB is connected before the filter with R14 and R15 as the voltage divider. I choose 2ma. of current passing thru it to get a standard value of R. You will also notice that the required 2V is unchange but the voltage output from the leg of the power fets is now 12.5V referenced to global ground (g.g).
This 12.5V is base on my analysis that "@ 50% duty cycle"(no audio),you will meassure there 1/2 of 25V referenced to g.g...So, it will swing max of +/- 12.5V reference to g.g. and +/- 25V across the speaker reference to neutral.
Of coarse these are the theoretical maximum values that losses or Vdrops are not included and duty cycles can stretch at 100% which is not possible to TL494.
So there you go...
LO and behold..........
An externally hosted image should be here but it was not working when we last tested it.
ledmania said:
Hi guys,
When I was on my bed last night, I could'nt sleep because of that crazy 12.5V that appear on the o/p of the power fets.
This is a big mistake on my part to assume that it is 12.5V but the trueth is, "it should not be".
The theoretical Vout there should be still 25V.
this is base on the fact that when Q1 is on Q2 is off, then Vout is 50V reference to g.g......And then when Q1 is off while Q2 is on, then Vout is 0V reference to g.g....therefor, @ 50% duty cycle with 200khz freq., this will sit on 25V which is more reasonable. So, R14 and R15 will remain as is.
LOL!
I am terribly worried that when I open my thread, there will be a lot of angry adept croud to shoot me but thanks God, you are all decent and gentle guys...Regards
ledmania
Hi guys, anyone here who tried to build the circuit already? I would like to build one pair since it's cheap and most parts are available in the philippine market except for the IR2011. I hope there will be some modifications on using IR2113 instead of 2011's due to it's availability on RS components Philippines.
Thanks,
Delon
Thanks,
Delon
class d
I have built a couple class d amps from articles in magazines but are looking for something better.Is yours a working amp yet.I have thought of using tl494,tl594,tl598 or sg3524,sg3525 as the pwm but have not got a chance to experiment yet.Take a look at some old stuff
http://www.angelfire.com/indie/jcnoernberg/switching.pdf
http://www.angelfire.com/indie/jcnoernberg/digitalcaramp1.pdf
You may want to look at Onsemi.com for some other pwm ics
I have built a couple class d amps from articles in magazines but are looking for something better.Is yours a working amp yet.I have thought of using tl494,tl594,tl598 or sg3524,sg3525 as the pwm but have not got a chance to experiment yet.Take a look at some old stuff
http://www.angelfire.com/indie/jcnoernberg/switching.pdf
http://www.angelfire.com/indie/jcnoernberg/digitalcaramp1.pdf
You may want to look at Onsemi.com for some other pwm ics
Hi Steve, thanks for the sites. I have those two articles from Electronics now and Popular Electronics magazines applying switch mode designs in audio amplification. I really appreciate your recommendation and would like to know if how does it sounds? I haven't tried those 60 watts and 100 watts 8 ohms amps though I have the schematic in my shack. hope to hear from you on those articles.
Best Regards,
Delon
Best Regards,
Delon
Delon said:
Hi guys,
HI delon,
It's nice to know that you are interested on this circuit but I am adviceing you to try it on breadboard first because there might be some tweaking needed such as the replacement of the opamp as overcurrent protector. I've noticed that ne5532 is not qualified to run on 5V but you can supply it with 12V as you like but you have to modify the two voltage deviding network on the i/p of the opamp of tl494.
I am no longer capable of modifying or showing another circuit on this thread because I am now working onboard a passenger cruise ship here in Europe in which my schematic editor software was left in Manila
, so, most of my responses to you guys will be limited .By the way, I forgot to mention that my circuit is very usefull to most students or hobbyist because it can be used to power your other electronic projects as variable voltage DC to DC converter..
In fact you can get at least 0 to 45 volts of o/p and still can retain its overcurrent protection capability by adding very few components..
I have a simple circuit that when added to the o/p of that amp can simply change the amplifier into a hi power battery charger for your car or to charge your SLA bats that give power to your beloved Tripath or Charlize
It consist of 1 fast schottky diode, one 6800uf caps, three 1/4watt resistors, one potentiometer and one miniature DPDT relay as a transfer switch selector as "amp" or "DC to DC con"...
Regards
ledmania
Re: wake this old thread
Hi Tekko,
I'm still around and checking my thread from time to time if someone is interested to it. As I said before that it is much beter to try it in breadboard first by supplying 24v(2 SLA bats in series)then recalculate the voltage divider R14/15 and R21/22 to provide 2v bias at the two inputs of the opamp and thats it...
I really wanted to try it by myself but i'm still here in EU and my sch editor was left in Manila so I'm totally handcuff in providing more reliable detail in this matter.
Now that you will try it then I'm very envy with you I will try my best to support you technically and spiritually, LOL! (I really mean it)... And I will visit this thread from time to time...
Regards,
ledmania
Tekko said:
Hi Tekko,
I'm still around and checking my thread from time to time if someone is interested to it. As I said before that it is much beter to try it in breadboard first by supplying 24v(2 SLA bats in series)then recalculate the voltage divider R14/15 and R21/22 to provide 2v bias at the two inputs of the opamp and thats it...
I really wanted to try it by myself but i'm still here in EU and my sch editor was left in Manila so I'm totally handcuff in providing more reliable detail in this matter.
Now that you will try it then I'm very envy with you
I will try my best to support you technically and spiritually, LOL! (I really mean it)... And I will visit this thread from time to time...Regards,
ledmania
Tekko said:
Yes Tekko you can use any low power schotky inverters as long as it is CMOS and not TTL due to supply voltage of 12v in w/c TTL is for 5v only.
And yes, it's LT sch. editor w/c I downloaded free from their site but I cannot download it here because we are using a very slow satellite connection shared by the passengers and crew altogether.
I'm going to print my sch on this thread so that I have a reference drawing for us to discuss while you are assembling it.
I'll be back later....
Regards
ledmania
Tekko said:
Yes, ir2010 takes both ttl and cmos inputs but remember that the inverter takes the input from TL494 in which may swing to more than 9v during modulation and your ttl may not handle the punch unless you use voltage dropping resistor to its input.
my suggestion is to use cmos.
Regards
ledmania
Tekko said:
Yo Tekko,
I intend to put that 2v from the power supply to track the voltage variation from the speaker to eliminate the offset voltage across the speaker itself. the noise that can be pick up by this can be smoothed out by the capacitor.So it's ok.
But hey Tekko, there are several corrections which must be addressed and are worth mentioning......Please print the sch in a piece of paper for quick viewing(page 4 post#37) and lets start.......
1. Ne5532 is not qualified to operate at 5v so you can supply 12v to it but change R18 to 6.8k and R19 to 4.7k.
the diode D11 and R11 from the output of the opamp should give a positive fb to the i/p to create a latch up condition to shut down the IR2010. But here is the problem, when the o/p is at logic "0" the vsat is still higher than 100mv and this will create a permanent latch up or logic "1" to the o/p disabling the fet driver permanently.....the correct diode to be put there must be Zener diode with 6v rating connected in a reverse bias mode(kathode from the o/p anode to R11)...With this, the zener is at hi impedance state when the o/p is low, but when hi then avalance conduction will take place giving positive FB to the i/p. I think this will work better.
2. you mentioned that you are going to use perfboard, well, this is not a good idea but for the sake of your curiosity and interest then its ok but please put your concentration to R9 in the sch...This must be change with a miniature trimmer pot with 500ohms resistance.. this is very important in protecting your power fets from shoot through in case the deadtime is too small. Just calibrate the pot to 20mv which will trip the power fets to 2amps and live it there for the moment, Why????. Because.....
3. Notice the pin 10 and pin12 of IR2010? In between is a U4 inverter that may cancel out the deadtime of hi side relative to the lo side...If i'm not mistaking, the hi side pin 10 is something like 25 nsec propagation delay compared to lo side but by inserting a 25nsec propagation delay of U4 inverter on pin 12 will result in a "0"nsec deadtime between the two i/ps and there you go,, shoot through will occur. Please verify my statement regarding the prop. delay of U4 and IR2010 on their respective data sheet...
Having a deadtime of less than 5nsec is very risky and if not, you might be entering into the "Realm of Quasi linear operation"..In a worst case scenario, I can call it "unexpected quasi class A" LOL!! LOL!! this means you will need larger heatsink due to hi quiscent current and also low efficiency.
for me 15nsec or more is good enough....
There are some anal soul whom are very sensitive to deadtime and distortion issue but I'm not one of them. I hope you are not one of them also.
So!! did I jeopardize your appetite in making this amp yet???
If not then you are a couragous guy!! LOL!!
Regards,
ledmania
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