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Class D Switching Power Amplifiers and Power D/A conversion

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Old 19th June 2010, 12:44 AM   #251
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Quote:
Originally Posted by Don Jerry View Post
I explored the same idea in the past, realizing that it's dangerous, because if the 'response time' of the switching controller on the first SMPS is not *identical* to the 'response time' on the other SMPS, they could start to oscillate... damaging the TP2050 board, themselves or more simply stop working (entering in protection mode).
So I don't suggest you to try that configuration, 2 switching controllers into the same PSU are never a good idea, although I have no doubt that in most cases it works.
Bye!
Also please notice that a typical AT/ATX PC SMPS performs the feedback on the +5V line (more is the current consumption on that line, more the switching controller widens the pwm to mantain the correct +5V voltage).
A typical move to have a good +12V output is to apply a fixed load on the +5v line:
"One note of caution - most power supplies require a minimum load on the main output (5V in your case) - indeed some PSUs fail to start up (or even blow up!) without one. It seems like you've been ok so far, but (perhaps surprisingly) it would improve long-term reliability to draw maybe half an amp from the 5 volt output - perhaps using a 10 ohm, 5W wirewound resistor. Doing this should improve the regulation of the other outputs, and might alter the sound quality..."

...but in such way you got a fixed regulation of the +12v output, so more is the current consumption on the +12v line, more is the voltage drop on that line... because the pwm is fixed, based only on the +5v resistor current absorption.
To solve that issue you have to modify the feedback circuit so that it reads the voltage drop on the +12v line instead of the +5v line.
Do that and you will have a true +12v regulated output without the necessity of applying a resistor on the +5v line.
I did that modification on some old AT PSU and they worked fine.
Of course that modification requires knowledge of how a SMPS works.
Basically you have to connect the feedback line to the +12v output instead of the +5v, decreasing properly the +12v with a zener diode so that the switching controller "believes" to regulate the +5v but in reality is regulating the +12v line.
Choosing the proper zener diode is also possible to achieve over +15v on the +12v output, so for example you could connect 2 x 14.5v modified PSU obtaining a 29v output... just perfect for the TK2050.

I prefer a single SMPS for the reasons I explained above but I think that I could try with a couple of SMPS connected in series... I have 5 x 300W ATX identical power supply at home that are waiting to be used in any way!
Bye!
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Old 19th June 2010, 02:47 PM   #252
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Quote:
Originally Posted by Don Jerry View Post
You added the white spacers to the bolts that retain the heat sink, I'm correct?
Thanks, bye!!
hi, we can tight the heatsink by doing this.and prevent bending the PCB.

Last edited by hifimediy; 19th June 2010 at 02:52 PM.
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Old 19th June 2010, 04:10 PM   #253
glt is offline glt  United States
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Originally Posted by glt View Post
...

I'm referring to http://www.st.com/stonline/products/...e/an/10606.pdf in my comments below:

I suppose the amp uses two STA505 output stage (one per channel) in parallel BLT configuration (Figure 7 of spec)

But according to figure 11, you can parallel the two ST505 in parallel BLT for higher current capability.

...
Now that I think of it, wouldn't paralleling the two ST505 support a mono configuration at 200W? This would be nice for a sub amp. It seems (from reading some of the posts in the sureelectronics thread) that the issue is to null the outputs to zero DC.
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Last edited by glt; 19th June 2010 at 04:23 PM.
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Old 19th June 2010, 04:41 PM   #254
glt is offline glt  United States
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Originally Posted by glt View Post
Now that I think of it, wouldn't paralleling the two ST505 support a mono configuration at 200W? This would be nice for a sub amp. It seems (from reading some of the posts in the sureelectronics thread) that the issue is to null the outputs to zero DC.
Further reading into the spec:


"To drive loads having very low impedance obtaining higher output power it is possible to furtherly
connect together on the same load two STA50x IC's (each one already configured as
single-paralleled bridge) doubling the current capability.
The correct connection is putting together the inductor (L1 with L3 and L2 with L4) terminals
on the load side. This to avoid uncontrolled shootrough current spikes, due to time mismatch
between the two IC's, which could be possible if the outputs are directly paralleled on the same
inductor.
The L and C values of the output filter have to be calculated tacking in account the load impedance:
to be noted that the inductance is now provided by two self-inductors in parallel (L1/
/L3 and L2//L4), so each one must have double value.
The inputs must be driven in parallel."

I guess some modification in the output filter is required... But certainly a mono configuration with two sta505 in parallel is possible (idea for next version)
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Old 19th June 2010, 09:42 PM   #255
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If you want a 200W mono amplifier, you might be better off using a higher power Tripath chip such as the TA3020 (2*200W at 4 ohms) instead of fighting to squeeze more performance out of a midrange chip like the TK2050.
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Old 20th June 2010, 05:46 AM   #256
glt is offline glt  United States
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Originally Posted by SoldierAnt76 View Post
If you want a 200W mono amplifier, you might be better off using a higher power Tripath chip such as the TA3020 (2*200W at 4 ohms) instead of fighting to squeeze more performance out of a midrange chip like the TK2050.
I'm aware of TA3020 amps. I do want to get the most out of a 12V battery...
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Old 20th June 2010, 09:47 AM   #257
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Originally Posted by glt View Post
I'm aware of TA3020 amps. I do want to get the most out of a 12V battery...
Hi, we can use sta508 parallel to achive 160W/ch to 4ohm.
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Old 20th June 2010, 10:14 AM   #258
v-bro is offline v-bro  Netherlands
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Quote:
Originally Posted by hifimediy View Post
Because of TP2050 is almost out of stock on the market now, STA505 is the best compatible part in my opinion.
Most alike yes, not the best. In all aspects the STA516/517 are the best replacement, but probably cost a bit more...

Or some Apogee chips also are capable of more current/higher voltage, but I never tried those...
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Old 20th June 2010, 12:57 PM   #259
sendler is offline sendler  United States
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Default STA517 still not available

Quote:
Originally Posted by v-bro View Post
Most alike yes, not the best. In all aspects the STA516/517 are the best replacement, but probably cost a bit more...

Or some Apogee chips also are capable of more current/higher voltage, but I never tried those...
It is strange that the STA517 or 516 is still not available in the US.
.
STMicroelectronics | Digital Audio Amplifiers
.
I can buy STA508, 505, or 518 though.
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Old 20th June 2010, 10:10 PM   #260
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Originally Posted by v-bro View Post
Most alike yes, not the best. In all aspects the STA516/517 are the best replacement, but probably cost a bit more...
With STA517 you have to double the voltage input... and that becomes another project (different power supply and some adjustments on the board).
Could be interesting, but instead of being an improvement I think that it would be something different.
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