Nearly there TK!   

You're an Electronics GURU! Feel up to posting a Circuit with Layout?

All the Best

  Chris

The application of the circuit really needs to have parameters placed around it.  One size fits all does not work well in power electronics.

Hi MarkE,

Yes, I hear you and agree it will not be an easy task to achieve a "One size fits all"!

But we can get close!

The Circuit I Posted, from Selfonlypath, is that! Very Close!

All the Best

  Chris

Chris there are a couple of things that you should look at in your circuit.

1. Critical:  The MOSFET avalanche protection is limited to the snubber network.  With a big inductive load that will either end up dissipating a lot of power or you will blow the MOSFET.  The flyback diode anode should be on the MOSFET drain, and the cathode on +DC where it is decoupled through a long inductance back to the MOSFET source.  The size of the decoupling capacitor depends on how much inductance there is back to the +DC supply.   This is particularly true given that you have a 1 Ohm gate turn-off resistor.

2. Design Improvement:  One section of the MCP1403 should be more than adequate for each MOSFET.  If you are going to drive more than 4.5A of gate current, you will have more issues with layout than driver strength.  The only reason that I would allocate by halves of that driver to one MOSFET would be if that made a big difference in the parasitic inductance in the layout.

3. Design Improvement:  You should place a 200uF capacitor in series with a 0.5 Ohm resistor across C4.  This will keep the filter L1/C4 from resonating uncontrollably when the MOSFETs are driven near 3kHz.

4. Design Improvement:  C5 should have a 47 Ohm or so resistor in series so as to limit the peak current load on the ATMEGA.  Otherwise you can kill the output pin from electromigration.

5. Design Consideration:  Z1 will only be effective if it has a very low inductance between the MOSFET gate and source.  Also, a typical zener will not act quickly enough to protect the MOSFET gate.  A TVS device rated at 16V that will trip by 20V would be a better choice.

5. Documentation Error:  The notes say D2 is for asymmetric gate drive.  It should say D3 and R4.

Chris there are a couple of things that you should look at in your circuit.

1. Critical:  The MOSFET avalanche protection is limited to the snubber network.  With a big inductive load that will either end up dissipating a lot of power or you will blow the MOSFET.  The flyback diode anode should be on the MOSFET drain, and the cathode on +DC where it is decoupled through a long inductance back to the MOSFET source.  The size of the decoupling capacitor depends on how much inductance there is back to the +DC supply.   This is particularly true given that you have a 1 Ohm gate turn-off resistor.

2. Design Improvement:  One section of the MCP1403 should be more than adequate for each MOSFET.  If you are going to drive more than 4.5A of gate current, you will have more issues with layout than driver strength.  The only reason that I would allocate by halves of that driver to one MOSFET would be if that made a big difference in the parasitic inductance in the layout.

3. Design Improvement:  You should place a 200uF capacitor in series with a 0.5 Ohm resistor across C4.  This will keep the filter L1/C4 from resonating uncontrollably when the MOSFETs are driven near 3kHz.

4. Design Improvement:  C5 should have a 47 Ohm or so resistor in series so as to limit the peak current load on the ATMEGA.  Otherwise you can kill the output pin from electromigration.

5. Design Consideration:  Z1 will only be effective if it has a very low inductance between the MOSFET gate and source.  Also, a typical zener will not act quickly enough to protect the MOSFET gate.  A TVS device rated at 16V that will trip by 20V would be a better choice.

5. Documentation Error:  The notes say D2 is for asymmetric gate drive.  It should say D3 and R4.

Hey MarkE,

Excellent! Thank you! We are a step ahead! Anyone an Eagle expert? Anyone like to put these changes MarkE has suggested/proposed into an updated schematic?

Thanks MarkE! Excellent Post!

All the Best

  Chris

Gunther has put a lot of effort into this design:
http://www.source-for-innovations.com/switch.htm

I have used the circuitry myself and it works quite well.


@MarkE

Jump in here Mark, make improvements and post some EAGLE files we can use to build breakout boards.  As sharp as you are in this area it shouldn't take you more than an hour or two to get us all setup.

Doug, I use OrCAD.  Is Eagle the choice around here for low cost?

Doug, I use OrCAD.  Is Eagle the choice around here for low cost?

I use DipTrace, but have had to learn EAGLE as it appears to be more compatible in the community.  Concepts are the same and there are a lot of tutorials out there to get up to speed quickly.

Doug, I use OrCAD.  Is Eagle the choice around here for low cost?

Hey Guys,

I agree, Eagle seems to be more 'Industry Standard'. I use different software also and am not confident enough to put Eagle Files out there that may have errors or bad practices that I am not yet aware of.

Eagle is Free also: -->Download Eagle<-- with lots of custom Library's.

Eagle does allow a full, one stop from start to finish solution. It can even get quotes for the manufacture of the completed Gerber Files. I am practising Eagle, learning its techniques so in the future I hope to be able to provide more help in this area.

All the Best

  Chris

Hey Dog-One,

For Sure! BeagleBone... Its awesome!

In saying that I did find the documentation a little confusing when I purchased mine. Its a 200MHz Clock for the PWM's but the embedded CPU is 1GHz on the Black. I was a little disheartened that this wa snot more clearly documented at the time I purchased. All in all, this is the best board I have purchased for overall wide range of features. FEZ Hydra can also run Linux on the Embeded CPU but its CPU Intensive compared to the BeagleBone.

WOW What a price drop! BeagleBone Black - $45.00 Thus far, this is the best option for price for our project!

Imagine VNC to your Home Power Unit to check stats and do maintenance all on a Credit Card Sized Unit! I guess we already see in in the phone technology so its not that hard to imagine...

Lurkers, Join in! we need to get the best from this thread so let us know your thoughts!

All the Best

  Chris

That does look like a nice kit for $45.