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kASD

kASD

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Joined 2004
fredos said:
Not really EMI generator...Already done with differential output choke, ground referenced floating full bridge output...

Fredos
Click to expand...

Then i think for the level shifting easiest way is to use 6N137 optocoupler + MIC4420 Gate Drivers........Which type node is Ground referenced ->after inductor or before inductor[common mosfet junction].....??

Fredos, why did you prefer bridge output, since the 600V 47A Mosfets are already available on the market and one can make a Half bridge amp upto 4KW @ 4 ohms very easily.....
What are the benefits of floating bridge over half bridge.....
 
Eva

Eva

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Joined 2003
200V MOSFETs have both substantially lower Rds-on and body diode reverse recovery charge.

On the other hand, in order to feed a half bridge you can "easily" get +/-200V with some ripple but perfect DC regulation from 160..250V AC mains with the help of a PFC frontend.
 
kASD

kASD

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Joined 2004
fredos said:
Grounded after output filter! These mosfet are too slow for switching amplifier! Look at spec!
`
Fredos
Click to expand...

Have a look
http://users.etech.haw-hamburg.de/users/mueller/LE/Mosfet_SPW47N60C3.pdf

What is the advantage of having floating bridge Vs Conventional single supply bridge......

I think in conventional single supply bridge you can use one common supply for all channels whereas in floating bridge seperate supply for each channel would be required.....
 
kASD

kASD

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Joined 2004
Eva said:
200V MOSFETs have both substantially lower Rds-on and body diode reverse recovery charge.

On the other hand, in order to feed a half bridge you can "easily" get +/-200V with some ripple but perfect DC regulation from 160..250V AC mains with the help of a PFC frontend.
Click to expand...


Evita,

I think isolation is also required after PFC frontend in order to realize this.....;)
 
Eva

Eva

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Workhorse said:

I think isolation is also required after PFC frontend in order to realize this.....;)
Click to expand...

This depends on amplifier construction and target application, but output isolation makes little difference in safety when you deal with over 120V AC of amplified audio, over 500Vp-p switching waveforms and big capacitor banks charged to 400V.
 
Eva

Eva

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F

fredos

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d-amp.com
I'm surprise of the post of Eva....Certification always need isolation between AC network and user side of an appartus...Even with fews 100 volt on user side...

Ground referenced is required for professional amplifier. You can't have a half DC voltage on output terminal referenced to ground input or case.

And you can't bridge a non-ground referenced amplifier...And yeah, feedback could be done as usual half bridge amplifier..

Fredos
 
F

fredos

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Power soft have more than 40VDC on each leg of the output referenced to absolute ground...Need more explication or already understand why this is not acceptable for professional application? Fews mV of offset is nothing, so any half bridge are OK..

Yeah STW50NB20 are only 32A...But take a look at the 75A and 100A 200V device of APT or IXYS....That's what I use in HVI series...Only advantage to go to ground referenced full bridge amplifier!

Fredos
 
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fredos

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I did'nt use anymore STW50NB20...I have move from a will to APT. Now whit quantity, they are cheap as ST one...Look into 200V device..Not 360V..STW75NB20 seem promising too...Yould always take care of dv/dt on power device...This is a major case of faillure for lot of DIYers...dv/dt have more influence on 300-400V rail than 180V!

Fredos
 
kASD

kASD

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Joined 2004
fredos said:
Power soft have more than 40VDC on each leg of the output referenced to absolute ground...
Click to expand...

If they have more than 40V between output node and ground reference there is nothing to worry just because the speaker is connected between output nodes of H-bridge.....not between ground reference.....
Simply stating that H-Bridge must be ground referenced doesnot hold any solid conclusion.........as long as the speaker is connected between output nodes of H-bridge[where there is very low millivolt level offset] poses no harm to speakers connected....

fredos said:
I did'nt use anymore STW50NB20...I have move from a will to APT. Now whit quantity, they are cheap as ST one...Look into 200V device..Not 360V..STW75NB20 seem promising too...Yould always take care of dv/dt on power device...This is a major case of faillure for lot of DIYers...dv/dt have more influence on 300-400V rail than 180V!
Fredos
Click to expand...

Oh great to hear that you finally decided to use all APT......;)
I agree with you that in high voltage rails operation, situation is lot more different than lower rail designs.......

Thanx
 
F

fredos

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Just imagine that you feed a speakon 8 cable to a 4 ways system, and that 2 amplifier have 40VDC offset and 1 at 80VDC and another one at 0VDC. Now a stupid lift driver pass over your cable ( when amplifier are on...) and short everything. Oh, I forgot to mention that this happen 5 minute before the begining of a show and you sound shop is 45 minute away....

Still professional to use amplifier with DC offset on speaker terminal?

That's just 1 situation....They are maybe 1000 other situation that an amplier with DC offset will fail in ''professional'' world...

Think about this...An amplifier with zero offset to ground have a lot more chance to survive in may stress condition, even with audio signal...

Wish that you got my point and that you did'nt design amplifier in that way..

Fredos
 
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