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Thread: Mosfet Driver

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    Default Mosfet Driver

    How to driver Mosfet P and N . Use trasitor, R,C and shocky diode. THANKS ALOT.

    I want build Haft H-bridge to driver 5 phase stepper motor

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    Quote Originally Posted by BCwanderer
    thanks your reply but i live in vietnam, i can't buy these IC. i need build driver buy descrect



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    How to fast driver?. Low side mosfet and High side mosfet in H-bridge.



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    How about these cricuit?

    Attached Thumbnails Attached Thumbnails Mosfet Driver-sch_bridge-jpg   Mosfet Driver-gatedrive-png   Mosfet Driver-mosfetbridge_180-gif  


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    Look up application note #U-102 for the TI/Unitrode UC3637 switch mode motor controller.

    You can download here:
    http://focus.ti.com/docs/prod/folder...plicationnotes

    Another app note can be found here:
    http://focus.ti.com/lit/an/slua073/slua073.pdf

    It shows a discrete based (part numbers and values) for high power fet based H (U-102) and half H bridges (U-112).

    The discrete bridge example in U-102 can run at a PWM'd frequency of 30Khz



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    how about this shecmatic?



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    Red face

    Quote Originally Posted by NC Cams
    Look up application note #U-102 for the TI/Unitrode UC3637 switch mode motor controller.

    You can download here:
    http://focus.ti.com/docs/prod/folder...plicationnotes

    Another app note can be found here:
    http://focus.ti.com/lit/an/slua073/slua073.pdf

    It shows a discrete based (part numbers and values) for high power fet based H (U-102) and half H bridges (U-112).

    The discrete bridge example in U-102 can run at a PWM'd frequency of 30Khz
    thanks you much, but in vietnam, i can't buy this IC .



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    I know that you can't buy IC from prior post. The application sheets posted shows 2 things:

    1. How to apply/use the IC

    and

    2. How to build discrete power amp (including part numbers for all parts).

    Importantly, it explains why the power amp is constructed as it is - this part of application note is simple assembly project.

    Simply ignore section regarding part 1 above

    and

    Follow the section dealing with power amp construction (part 2 above.)

    This is full and complet answer to your original question (how to build discrete based H/half H bridge with MOSFETS). I hope it helps you.



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    Ok. I have some shecma. I think that can help you use mosfet driver IC for Haft H-bridge

    Attached Thumbnails Attached Thumbnails Mosfet Driver-bldcm1-gif   Mosfet Driver-smc3hpd-png  


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    Two good options(i think) for the mosfets that are very common and cheap here are

    IRF540 (n channel)
    Vdss 100V
    Rds(on)0.077ohm
    Id 28 amps
    cost 0.88usd (in Argentina)
    http://www.irf.com/product-info/data...ata/irf540.pdf

    IRF9540 (pchannel)
    Vdss -100V
    Rds(on) 0.117 ohm
    Id -23 amps
    cost 1,3usd (here in Argentina)
    http://www.irf.com/product-info/data...a/irf9540n.pdf

    Im working on the schematic posted firs, i think it might work, bought everything and have it assembled just need to test it, ill let you know my results. I think with a little more logic it could be made more safe, i mean to preventa short on the same side



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    Quote Originally Posted by ez-cnc.com
    Two good options(i think) for the mosfets that are very common and cheap here are

    IRF540 (n channel)
    Vdss 100V
    Rds(on)0.077ohm
    Id 28 amps
    cost 0.88usd (in Argentina)
    http://www.irf.com/product-info/data...ata/irf540.pdf

    IRF9540 (pchannel)
    Vdss -100V
    Rds(on) 0.117 ohm
    Id -23 amps
    cost 1,3usd (here in Argentina)
    http://www.irf.com/product-info/data...a/irf9540n.pdf

    Im working on the schematic posted firs, i think it might work, bought everything and have it assembled just need to test it, ill let you know my results. I think with a little more logic it could be made more safe, i mean to preventa short on the same side
    Thanks your reply.
    I use irf540/9540 too. and higher vol i use irf640/9640 (200V Vds)

    I don't know how to protec mosfet, when mosfet low side and high side open, -->short cricuit Boommmmm, fire, bibobibo

    We can driver direct from CMOS logic gate, use 12V for Vcc. but you can't driver faster 100khz. need add shocley diode or use push pul transitor driver it, can driver faster 400khz



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    Quote Originally Posted by ez-cnc.com
    Two good options(i think) for the mosfets that are very common and cheap here are

    IRF540 (n channel)
    Vdss 100V
    Rds(on)0.077ohm
    Id 28 amps
    cost 0.88usd (in Argentina)
    http://www.irf.com/product-info/data...ata/irf540.pdf

    IRF9540 (pchannel)
    Vdss -100V
    Rds(on) 0.117 ohm
    Id -23 amps
    cost 1,3usd (here in Argentina)
    http://www.irf.com/product-info/data...a/irf9540n.pdf

    Im worposted firsking on the schematic , i think it might work, bought everything and have it assembled just need to test it, ill let you know my results. I think with a little more logic it could be made more safe, i mean to preventa short on the same side



    is this shecmatic. How many PWM speed you use?

    Attached Thumbnails Attached Thumbnails Mosfet Driver-sch_bridge-jpg  


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    As far as i know the speed has to be arround the 20khz, lower values generate an audible noise and if you go to higher frequencies generate too much loss in the core.
    Any ideas in how to do the pwm control using pic. I mean a flow diagram.



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    "I don't know how to protec mosfet, when mosfet low side and high side open, -->short cricuit Boommmmm, fire, bibobibo"

    I believe you are referring to a phenomenon called "shoot through". This is where the P and N fets on either the left or right side of the bridge momentarily conduct - the current "shoots through" directly from +Vs to -Vs or + to -.

    Sophisticated H bridge mosfet drivers usually have ciricuitry contained in them to prevent it. If you create a discrete driver, you have to protect for it in the design. You do so with component timing or hard logic.

    In the U-102 design posted previously, resistor timing/sizing is used in combination with the NPN/PNP transistor selections to provide "shoot through" protection. This is explained in the application note.

    It is done by forcing one of the fets in the bride to go into full saturatiion slower than the other by inserting resistance into the gate path. By careful gate resistor sizing and placement with respect to the totem pole transistors that drive the fet gates, you can 'time' the turn ons/offs so that shoot thru does not occur - or is at least minimized.

    This is how the UC-102 can work at 30Khz and at 10-12 amps.

    IF you want to run at 400khz, you may not be able to rely upon simple gate resistors to prevent shoot through - a more sophisticated scheme may be required. At 400Khz, wiring can become VERY critical to circuit timing - you may require a PCB. Do not be surprised if hand wired drives don't work or don't work well at this speed - simple board/wiring capacitance issues can affect the critical timing factors.

    This is where the dedicated driver IC's come into play - they often use hard logic to handle the critical turn on/off timing needed to prevent shoot through in ultra high speed circuits.

    For competitive reasons, I would not expect for a chip supplier to explain how to do this comlex protection scheme. It is a prime reason why their chip is used/needed in the first place...



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    I just ment a little logic just to make sure that only oposite sides of the bridge can be activated. Cause knowing myself im sure il blow everything just for not paying attention jajajaja. Is there a need to have a pwm at such high speeds like 300khz or 400khz???



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    If the freq is too high, you will end up with excessive eddy current losses in your motors and they will get hot. 20Khz works well.

    If you're using a MCU, you could simply turn off one transistor before turning on the other. As a backup you could add a transistor to cut off the other's drive when energized.



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    Quote Originally Posted by H500
    If the freq is too high, you will end up with excessive eddy current losses in your motors and they will get hot. 20Khz works well.

    If you're using a MCU, you could simply turn off one transistor before turning on the other. As a backup you could add a transistor to cut off the other's drive when energized.

    300Khz just is Step rate. Professtion stepper driver, can up step rate to 200khz. I want mosfet Reponsible 300khz, because safe speed. safe speed equad max div 2.



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    The high step rate is only required if you use a very high microstepping division. It looks good on paper, but there's really no measurable performance difference between 10 and 1000 microsteps.



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    Quote Originally Posted by H500
    The high step rate is only required if you use a very high microstepping division. It looks good on paper, but there's really no measurable performance difference between 10 and 1000 microsteps.
    thanks your reply. I can you hepl me design mosfet gate drivers. can run at 100khz step rate. and 33khz pwm speed



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