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MOSFET Mania

Various MOSFET driving circuits for various projects

SUFSUF
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Properly drive MOSFETs (or IGBTs) is not an easy task. When I started this project, I just realized obvious problems with the RAMPS board (trace width, polyfuse, lack of cooling, etc.). I learned lot since. This is why I changed the title. Now I want to document (previously built), and create new MOSFET driving circuits. Simple drivers, half bridges, full bridges.

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  • 1 × IRLZ44 High Current N-Channel MOSFET, logic level
  • 1 × INA168/INA169/INA193-INA195 Current Shunt Monitor
  • 1 × R005 Shunt resistor

  • In work

    SUF08/11/2014 at 04:38 0 comments

    Yesterday finally I installed the finished board into my 3D Printer. It works correctly with some minimal heatsink added.

    The next will be the test of the current monitoring.

  • Correct MOSFET

    SUF08/06/2014 at 21:12 0 comments

    I just replaced the IRFZ44 MOSFET to an IRLZ44. Now it works perfectly. It switch on around 2.1V

    Hopefully I can test it in the 3D Printer tomorrow morning

  • Inapropriate MOSFET

    SUF08/06/2014 at 03:57 0 comments

    Today I switched on and started to measure the circuit.

    It switches on correctly and working except one thing. My original feeling unfortunately had been verified. The switch on voltage of the MOSFET I used (this one I found at home) is to high.

    It switches on at 4.5-4.7V what is not really acceptable for the output of the Arduino inside the 3D Printer.

    So I need to change the MOSFET to something else before I can continue.

    I checked the datasheet of this one. It states that the Vgs threshold voltage should be in between 2 and 4 volts. :-(

    But, I've the replacement type: IRLZ44N. This is definitely a logic compatible one. Hopefully during today I'll be able to pickup some.

  • Finished Board

    SUF08/04/2014 at 09:48 0 comments

    The first board (this for my 3D Printer) has been finished. It is ready for testing some cleanup would be useful :-) There will be some measurement (FET Rgson, current measurement calibration, etc.)

    Seeing this project I'm thinking about two derivatives: an enhanced RAMPS board, and a Brushed DC rpm controlled driver for my CNC.

  • Finished Design

    SUF07/30/2014 at 21:53 0 comments

    The Schematics and the PCB design is finished. The current version is suitable for the 3D Printer. The CNC spindle driving will need some more work because the massively inductive behaviour

  • Scematics v1

    SUF07/23/2014 at 06:40 0 comments

    I started working on this project. The first version of the schematics is published on the github.

    I've a little problem with the current sensing amplifier and therefore some modifications are still come: I want to make it a little bit more versatile therefore I plan to add INA193-INA195 also as an option. This ones are not able to work from 48V supply so in addition I'll add a zener based regulator as an option.

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K.C. Lee wrote 07/23/2014 at 13:27 point
That's what I think you are doing based on your description. The IRSF3010 is a 11A part. Don't know enough about 3D printers to know your rating.

The hotswap controllers can be think of as a MOSFET controller that protect against faults. Isn't that what you are building around your MOSFET?

You can size the MOSFET for your voltage/current. The Safe Area Operation (SOA) is what is a pain to implement if you are going discrete. I hope you are familiar with MOSFET parameters know what they means far beyond just voltage and current ratings.

> I want to make it a little bit more versatile therefore I plan to add INA193-INA195 also as an option. This ones are not able to work from 48V supply so in addition I'll add a zener based regulator as an option.

That's the reason why I pointed out high voltage linear and SMPS regulators that are designed for providing a low voltage for your control circuits i.e. INA193-INA195

Or are you responding to mr.jb.swe ???

  Are you sure? yes | no

SUF wrote 07/23/2014 at 15:13 point
No, no, using the INA parts are totaly independent of the basic operation of the circuit. I'm using them just for measurement purposes. As we are talking about relatively high current, the voltage drop across the shunt resistor is getting crucial (wasted energy, disipated heat, remaining voltage of the load). I had bad experience with a malfunctioning and an out-of spec SSR (4V and 2V drop in a 12V DC circuit). With the first one I wasn't able to heat my bed over 75°C and with the second one it was hard to keep a constant 105°C.
Based on this I've choosen an R005 shunt, what produces 50mV drop at 10A. I want to measure the current of the bed with an ADC in an MCU what have roughly 3V input range for the full scale. Based on this I need some amplification.

To be honest I'm just picking up some knowledge on the MOSFETs. In this situation I copied the original RAMPS switching circuit, and only intend to do two modification, what is mainly on implementation and not on design side:
1. Use much wider tracks on the PCB. On the original I was able to blow the track with a short cicuit without fireing the polyswitch
2. Use real fuse instead of the polyswitch, because it fired when it should not. The cricuitry around it produces some heat what lowered the switch of point below the heated bed's operating current. (On my opinion this practicular 3D printer has a bed design, mechanically and electronicaly)

I hope this circuitry will be good enough for the heated bed. For shure I'll need to pick up more information for the CNC spindle drive, because of it's highly inductive load.

  Are you sure? yes | no

K.C. Lee wrote 07/23/2014 at 08:26 point
There are a lot of high voltage switch solutions out there. Might be worth looking into before rolling your own from discrete solutions.

Fully protected low side such as IRSF3010 which is essentially a rugged MOSFET with protection circuit built-in.

Negative Hot Swap / Inrush Current Controller that limits power dissipation to the external MOSFET so it stays within SOA during a fault.
e.g. http://www.ti.com/product/lm5067

There are high voltage regulators and they come in linear regulator or even switch mode supplies. Search on TI - their Nation part SMPS was 100V and TI's TL783 linear regulator 1.25V to 125V 700mA (watch out for power dissipation if you are drawing a lot of current ) .

I came up with the idea of using a constant current source (using discrete part) to a zener diode as shunt regulator in a product line. It works well.

  Are you sure? yes | no

SUF wrote 07/23/2014 at 11:44 point
Hi,
I may misunderstand you, but I'm working on a tiny little load switch here to replace the load switch of my 3D printers heated bed, and provide computer based switching capability for my CNC machines spindle, and not trying to design power a supply here. The power supplies I already have. Some Chinese industrial SPMS ones.
The IRFS3010 what you mentioned would be a good option but unfortunately has some issues in this project:
1. Obsolate part. It can not even be found on IRF's site
2. Not available trough the channels reachable to me
3. The maximum DS current is not enough for the heated bed
I checked at IRF, the part may good for my purposes is the IPS0151, but it is also not available to me (at least on reasonable cost)
The constant current source would be a good idea for the heated bed, but not right now. I'll consider some as an improvement when my 3D printer is fixed finally.

  Are you sure? yes | no

mr.jb wrote 07/23/2014 at 06:57 point
you might find something useful here http://www.prodctodc.com/

  Are you sure? yes | no

SUF wrote 07/23/2014 at 11:45 point
Thank you for the link, but I'm trying to build a High current switch and not a PSU. Unfortunately I haven't found any on the site you mentioned.

  Are you sure? yes | no

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