Power amp under development

Hi quasi :wiz:

I use UR design but in deferent way the bottom side and
Component side are reversed

Unfortunately I made pcbs in mirror image :spin:

Except mje 350/340 and Single turn pots, all components
and power fets are between pcb and heatsink and it look
good :D

now I am designing high power (10 FET)
stereo version pcb with dc and temp protection,
when I complete I’ll send U Gerber files :nod:

I am waiting for U R short cct

Can U help me in (inverse CMMR) please see passive
surround sound thread :apathic:


:) :)

regards
ravi
 
Short cct protection

Short cct protection;

The most common short cct protection that I have seen involves using 2 transistors b-e to monitor the voltage across the output stage source (emmitter) resistors. These transistors then shunt the gate drives.

I prefer to disconnect the load permanently until the amp is manually reset.

In my mind there are pros and cons for both.

What I had in mind was an optocoupled sense across the source resistors activating the DC protect cct with a latch that could only be reset by turning the amp off and on.

Any thoughts from our knowledgeable friends?
 
Hi,

may I suggest a protection circuit that uses n-channel fets to switch the supply to the output stage (while keeping the input and VAS alive in order to recover from failure)?

It has been discussed a couple of times in the solid state and pass labs forums. One would need a "high side" drive (i.e. an elevated supply that could also be used for the input/VAS) and two n-channel mosfets that are capable of withstanding twice the rail voltage at the maximum current and incorporate a very low Rds(on) in order to minimize power loss and heat.

Would work like a solid state relais without the relais contacts (and switching time, sound, arcing, etc.) and require less board space while really switching off the current through both output transistors and speakers. Either ON, ST, IRF and IXYS manufacture suitable mosfets in TO3P/TO247 case (could be mounted and would look like the rest of the output stage).

Note that one would only need one set of power-mosfets per amplifier channel, because when fully on, a single mosfet can sustain (and switch) *a lot* more current than a linear class A/B output stage.

Can anyone report some experience with such an attempt? I remember a couple of DIYers have tried it but I couldn't find the threads right now.


What I had in mind was an optocoupled sense across the source resistors activating the DC protect cct with a latch that could only be reset by turning the amp off and on.

Could work like a charm. ;)

Ciao,
Sebastian.
 

Attachments

  • nchan mos350 with dc detect v1-4.pdf
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You can use this schematic for soft start...

POZDRAV;)
 

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  • delay.jpg
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