IRFZ32N MOSFET H-Bridge

Discussion in 'The Projects Forum' started by aGpLT, Mar 23, 2010.

  1. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Hello everyone once more :] So i am using IRZF34N for H-bridge. My input voltage to Drain is +12V and for Gate i am using +5V impulse. So this is scheme http://www.mikroe.com/en/books/pic-books/mikroc/ch3/images/fig3-78.gif which i am using. But it's not working properly, when i send impulse to Gate Q1 and Q3 i got sound from power supply and my motor doesn't work. So if you could help me with some information, advice or something else, Thank You.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    That block diagram is not enough to tell anything about the actual circuitry. An accurate schematic is necessary.
     
  3. SgtWookie

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    Jul 17, 2007
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    Like Beenthere said, we need an accurate schematic.

    The diagram you linked to has no part numbers or reference designators (item numbers) on it.

    If Q1 and Q3 are on the same side of the H-bridge, you are causing a "shoot through" condition, where the MOSFETs short out the supply.

    I hope that you are using (a) gate driver IC(s) that are non-inverting and have a high and low side driver. You cannot successfully directly control the gate of a high-side N-channel MOSFET from a 5v uC.

    Your MOSFETs are standard level. You need to get Vgs to 10v in order to fully turn them on.
     
  4. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    My schematic is the same as in this schematic only MOSFETs are IRZF32N N type and to gate i give directly 5v. So if i get it correctly for gate i need directly give 10V and its only possible with other transistors becouse my uC is PIC16F88.
     
  5. SgtWookie

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    Jul 17, 2007
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    You have to use gate drivers.
    Otherwise, you will not be able to supply your motor with any current, because you won't be able to turn the high-side gates fully on.

    You can make your own (can be complicated) or you can buy MOSFET gate driver ICs.
    Microchip has quite a selection. Many other manufacturers make gate drivers as well.
    You will need a total of four gate drivers, as shown in the diagram. The two on top are high-side drivers. The other two are low-siide drivers.
     
  6. onlyvinod56

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    Oct 14, 2008
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  7. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Thank You, you made my eyes open !, it's quite complicated situation for me.

    I think it's going coast much more than to buy 2 P type and 2 N type MOSFETs. What you all think about it ? :]

    This is schematic: http://schematics.circuitdiagram.net/images/jdv1235544233p.jpg

    I think it's quite similar to my situation.
     
    Last edited: Mar 24, 2010
  8. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Soo what you think ? :]
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    You cannot turn an IRFZ32 fully on with only 5V Vgs.

    Using P mosfets on top may simplify your drive, but still won't eliminate the 5V-problem. As others have asked, please post the actual design you want to make.

    John
     
  10. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    I want cheapest possible variant to control motor with function to reverse it. also it would be good if i could use PWM. I tryed with controller but it didn't work, and it won't for those motors so i trying now to make H-Bridge myself with MOSFETs. My motor is 2.4V 1A, i want to control H-Bridge using uC.
     
  11. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Which controller, which circuit, what did it do, why didn't it work?

    You can control a "logic level" mosfet with a uC, particulary if turn-on and turn-off times are not critical. Your need for only 1 A probably means those times are not critical, if you use large components such as you have named. For an example of a logic level mosfet, look up the datasheet for the IRLZ44 and others in that series. I might choose the IRLZ24 for your needs.

    As for the high-side mosfets, you could consider using P-channel versions. But, when you say low cost, you need to consider all parts of the drive, including your time. You might be able to get 4 N-channel mosfets plus a simple driver for less than trying to build something from scratch.

    John
     
  12. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    1.
    L298N, simple circuit with several diodes, some LEDs to show which direction motor is rotating and some resistors. Problem is that it have to big voltage drop in uC, and my motors don't get enough supply to have power to lift project. In this forum is that thread - http://forum.allaboutcircuits.com/showthread.php?t=33992&page=3 , i tryed everything and it is just not working.
    2.Ok, when price doesn't matter i need as fast as possible to do this H-bridge, so i need to choose properly MOSFETs. So for low side i have IRZF34N, but i don't know whic to choose for high-side.
     
  13. SgtWookie

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    Jul 17, 2007
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    Attached is a circuit I've been toying with. I called it the "Flying 555 H-Bridge", because I'm using LM555 timers for gate driver IC's; and the high-side 555s ground reference flies up and down with the source terminals of the high-side MOSFETs. It should work with the MOSFETs you have.

    It's not complete. R21 and R22 are current sensing resistors, with notes to me for selecting resistors for a 2A motor. It's the current sensing portion that's missing.

    A and C control the left and right high side drivers. You can't leave them high for longer than about 100mS without bringing them low to recharge the cap. The 555 has an internal 15k resistive divider that drains the boost cap fairly quickly.


    If you want gate drivers with fewer parts, then just buy gate driver ICs, or a dedicated H-bridge IC.

    If you want cheaper, then build one from discrete transistors, resistors, diodes, and caps.
     
    Last edited: Mar 25, 2010
  14. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Oh gosh, i am really in bad situation... :D i am so confused that i can't understand at all... ok thank you all for help somehow i will try to understand and learn these things.

    BTW, i have found one circuit with gate driver, http://www.circuit-projects.com/fp/motor-driver/schematic.jpg i think i could use my transistors IRFZ34N. (so lame write thread with wrong transistor name... sorry).
     
    Last edited: Mar 26, 2010
  15. Terp

    Active Member

    Jun 6, 2008
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    I'm not sure exactly what the 2.4V and 1A rating for the motor that you provided means, as I'm not experienced with motors. But, I am guessing that these either are maximum allowable limits, or are minimum I-V values for motor operation. Now, refer to this datasheet:

    http://www.datasheetarchive.com/IRFZ32-datasheet.html

    If you look at the test result plots, you'll see the I-V characteristics of the FET. Those test results show that the threshold voltage is around 4.25 V, so your gate-to-source voltage would have to be a minimum 4.25 V for the FET to conduct non-negligible current through the motor. Like others have pointed out in this thread, you probably need to up your voltages fed into the MOSFET. Without a knowledge of what the source voltage on the MOSFET is, no conclusive statement can be made as to why the motor doesn't work in your setup. Is it because you don't have enough current/voltage, or is it because the motor itself is bad?

    Hope this helped.
     
  16. SgtWookie

    Expert

    Jul 17, 2007
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    Sure, you could use that circuit.
    However, the 330 Ohm gate resistors R1 thru R4 are much too high, which will lead to slow gate charge/discharge, and resulting heat dissipation in the MOSFETs.

    I would change them to a much lower value; something on the order of 2.7 Ohms to 4.7 Ohms.

    D4 thru D7 are redundant to the body diodes in the MOSFETs. I am not certain why the author used them; perhaps to obtain a lower Vf. The 1N5818 diodes are rated for 1A average current; they could cause problems if operating an inductive load at more than about 2A current.

    The way the circuit was drawn makes it a bit harder to understand; for example C5 and D2. There are a number of parts that are isolated and connected by symbols. While this is electrically correct, the viewer has to make the connections in their mind.
     
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  17. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    So if get it right those diodes i don't need at all or i need to choose with higher parameters. is it correct ? :]
     
  18. SgtWookie

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    Jul 17, 2007
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    You can omit D4 through D7, as the body diodes in the IRFZ34 MOSFETs serve that function.
     
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  19. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Re: D4 thru 7
    They can probably be omitted, but it is not uncommon to see such diodes included. The mosfet intrinsic diode is said to be slow. You may want to consider including them in the PCB design and then not populating them. If they are needed, they are then a lot easier to add.

    As I recall, a conventional H-bridge IC was tried and "didn't work." The OP is now trying to copy a published circuit that does the same thing, but is substituting different mosfets. That change is probably insignificant, but there are other changes being discussed as well. Assuming there will be some initial glitches, I believe it is a good practice to change as few variables as possible and to leave the door open for future modifications, if needed.

    John
     
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  20. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Thank You all for your time, i will try some experiments and post here results. Maybe it will help someone with same problems :]
     
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