Monday, April 8, 2013

H-Bridge Inverter Circuit Using 4 N-channel Mosfets - Modified Sine Wave

The following post describes an H-bridge modified sine wave inverter circuit using four n-channel mosfets. Let's learn more about the circuit functioning.


We all know that among the different inverter typologies, the H-bridge is the most efficient one, since it does not necessitate the use of center tap transformers, and allows the use of transformers with two wires. The results become even better when four N-channel mosfets are involved.

With a two wire transformer connected to an H-bridge means the associated winding is allowed to go through the push pull oscillations in a reverse forward  manner. This provides better efficiency as the attainable current gain here becomes higher than the ordinary center tap type topologies.

However better things are never easy to get or implement. When identical type mosfets are involved in an H-bridge network, driving them efficiently becomes a big problem. It is primarily due to the following facts:

As we know an H-bridge topology incorporates four mosfets for the specified operations. With all four of them being N-channel types, driving  the upper mosfets or the high side mosfets becomes an issue.

This is because during conduction the upper mosfets experience almost the same level of potential at their source terminal as the supply voltage, due to the presence of the load resistance at the source terminal.

That means the upper mosfets come across similar voltage levels at their gate and source while operating.

Since as per the specs, the source voltage must be close to the ground potential for efficient conduction,  the situation instantly inhibits the particular mosfet from conducting, and the entire circuit stalls.

In order to switch the upper mosfets efficiently  they must be applied with a gate voltage at least 6V higher than the available supply voltage.

Meaning if the supply voltage is 12V, we would require at least 18-20V at the gate of the high side mosfets.

The proposed H-bridge inverter circuit having 4 n channel mosfets tries to overcome this problem by introducing a higher voltage bootstrapping network for operating the high side mosfets.

N1, N2, N3, N4 NOT gates from the IC 4049 are arranged as a voltage doubler circuit, which generates about 20 volts from the available 12V supply.

This voltage is applied to the high side mosfets via a couple NPN transistors.

The low side mosfets receive the gate voltages directly from the respective sources.

The oscillating (totem pole) frequency is derived from a standard decade counter IC, the IC 4017.

We know that the IC 4017 generates sequencing high outputs across its specified 10 output pins. The sequencing logic shuts subsquently as it jumps from one pin to the other.

Here all the 10 outputs are used so that the IC never gets a chance of producing incorrect switching of its output pins.

The groups of three outputs fed to the mosfets keep the pulse width to reasonable dimensions. The feature also provides the user the facility of tweaking the pulse width that's being fed to the mosfets.

By reducing the number of outputs to the respective mosfets, the pulse width can be effectively reduced and vice versa.

This means the RMS is tweakable here to some extents, and renders the circuit a modified sine wave circuit ability.

The clocks to the IC 4017 is taken from the bootstrapping oscillator network itself.

The oscillating frequency of the bootstrapping circuit is intentionally fixed at 1kHz, so that it becomes applicable for driving the IC4017 also, which ultimately provides about 50 Hz output to the connected 4 N-channel H bridge inverter circuit.


The proposed design can be much simplified as given here: http://homemadecircuitsandschematics.blogspot.in/2013/05/full-bridge-1-kva-inverter-circuit.html





64 comments:

  1. @swagatam, the values of the components is not shown. Pls what values are required?

    ReplyDelete
    Replies
    1. click the diagram to enlarge, the values are given in the diagram itself.

      Delete
    2. Exactly sir, can the circuit be used for 220vdc inverting, like i can see some kind of arrangement in chopper transfomer inverters

      Delete
  2. can you please add battery charging circuit to this also

    ReplyDelete
  3. But how could an input voltage of 220vdc be regulated to 12v in my quest to use your circuit to invert 220 to supply the circuit. I have a little diverted, pls bear with me.

    ReplyDelete
    Replies
    1. I did not understand your question, please provide a clear description of your requirement, are you referring to compact ferrite-core inverter circuit??

      Delete
  4. Dear Swagatam . It is really an innovative idea.

    ReplyDelete
  5. Verily true quoating you, "I did not understand your question, please provide a clear description of your requirement, are you referring to compact ferrite-core inverter circuit??"
    Yes because that is where they primarily use a centre tap ferrite-core to generate high frequency ac then rectify and smoothen it to give that kind of around 350vdc and then use a h-bridge connection to re invert to 220vac.
    So how applicable is your circuit to drive the transistors assuming their voltage rating is upto 500v. That is why i want to assure myself b4 testing your idea. Thanks.

    ReplyDelete
    Replies
    1. The mosfets can be connected to the high voltage DC in the above circuit for your application. the IC stages may be powered from the battery.

      It might work, but not sure.

      Delete
  6. Pls another observation.
    How could constant voltage be maintained when more load is applied on the output.

    ReplyDelete
  7. This comment has been removed by the author.

    ReplyDelete
    Replies
    1. for that we will have to add another controller stage, I'll possibly update it soon.

      Delete
  8. dear swagatam
    everything looking very nice, i need your help with making pure Sine Wave inverter to build. i have mod-sine wave inverter 3500w and i was hoping to make it to pure sine wave out put. is this can be done?

    regards
    Mohamed

    ReplyDelete
    Replies
    1. Dear Mohamed,

      It may be possible, you may take the help of the following article

      http://homemadecircuitsandschematics.blogspot.in/2013/04/how-to-modify-square-wave-inverter-into.html

      Delete
  9. http://www.eeweb.com/electronics-forum/need-help-regarding-ups-as-a-final-year-project/
    I have exported one of your ideas here. You may login to see.

    ReplyDelete
  10. sir swagatam,
    what the value of transformer?
    the out put is ac or dc?

    ReplyDelete
    Replies
    1. shabbir, transformer rating will depend on your required specs, the output would be AC

      Delete
  11. Hi Kassim,

    I know that you have done it with a good intention, but instead of exporting the diagrams it would be better if you invited your friends to my site by providing them the relevant links.

    ReplyDelete
  12. As you could see there on the circuit not a single value is given, the student needed to know that to get the values he needed to hit on the 'link' to extract the values to execute the project. That is the essence of the internet global village.

    ReplyDelete
  13. Hello Swagatam
    i did your circuit but it did not work and when i test the out AC Volt I find it only 4 Volt and i supply the circut by 12 DC Volt also i test the out of CD4049 it is only 8 Volt can u help me and l look for all lines and componenet and all is ok
    thanks

    ReplyDelete
    Replies
    1. It would be difficult to say without knowing about the entire set up that you have used....is this your first inverter project? are you well versed with the concepts? if its your first attempt then you would first have to know many things related to the subject for succeeding...

      the output from the 4049 stage should be at least 18V, it's a tested design

      Delete
  14. congrats sir swagatam nw you can create this H-brigde circuits ,and what I can see no more preset this design that I realy find .thanks sir swagatam your great Engineer hoping you can devilope this circuit..

    ReplyDelete
  15. Dear Mr Swagtam,
    i need your help in his circuit i have 22 Volt on the Collector or the 2 BC547 but on the High Mosfets gate the volt is 4.0 Volt and i check all lines and connection and also i test the out of CD4017 by Led it is pulsed so i have only 4 Ac volt before the Transformer after it i have 80 volt only so i need your Suggest and help to solve this problem
    thanks too much

    ReplyDelete
    Replies
    1. Disconnect the mosfets completely from the transistors, and supply.

      after disconnecting the gates from the emitter of the transistor, check the voltage at the emitter of the transistors.

      tell me the results, then we can proceed.

      Delete
    2. Dear Swagatam

      i Disconnect the gates of Mosfets from the Emitter of Transistors and i have the Collector Volt is 22 Volt and the Emitter Volt is 4 Volt
      this problem make me Crazy so I change the Emitter 1 K Resistor by 10 K and the Emitter Volt is 8 Volt

      :(

      Plz Told Me where is the problem

      Delete
    3. Connect a BC557 transistor stage with the BC547 transistors in the following manner:

      connect the emitter of the BC547 directly to ground.

      connect the collector of the BC547 to the 22V source via a 1K resistor.

      connect BC557 base with the collector of BC547 via 10K resistor.

      connect collector of BC557 to ground via a 1K resistor.

      Connect the mosfet gates directly to the collector of BC557

      Delete
    4. thanks Swagatam for ur help
      But you forget to told me about the Emitter of BC557


      Delete
    5. emitter of 557 will go to 22V source.

      Delete
  16. hey i would like to build that circuit but where do i get
    parts

    ReplyDelete
  17. Iam not sure ur configuration is ok, why not upload ur connection to identify the problem visually, anyway Swagatam is there.

    ReplyDelete
  18. my brother thanks for the nice idea,, but my question is that is this a sine wave inverter? is it suitable to carry inductive loads?




    ReplyDelete
    Replies
    1. Hi Tessy,

      By removing one or two diodes, the design can be made into a modified sine wave, but I am not sure about the exact results how it would be.

      Delete
  19. sir Swagatam, can I use this for ic sg3525 inverter circuit and will I need to use two of ic 4017 since sg3525 has two output, please help me on this, cos am having problem with ic ir2110 for full H bridge and I see yours is better. thanks.

    ReplyDelete
    Replies
    1. Foma, if you want to include SG3525 then you won't require the IC 4017.

      you may replace the 4017 IC with sg3535, the outputs of the SG3525 now directly gets connected with the mosfets and the transistors. The following diagram will provide a better picture.

      The connection from the N1 and N2 gates can be ignored because the sg3525 will have its own separate oscillator.

      http://homemadecircuitsandschematics.blogspot.in/2013/05/full-bridge-1-kva-inverter-circuit.html

      Delete
  20. hello sir. i have found in some website,the H-bridge was made of 2 n-channel and 2 p-channel MOSFET, but here H-bridge is made up of 4 n-channel MOSFET. is this given circuit is right?

    ReplyDelete
    Replies
    1. using 4 n-channel mosfets is more efficient, therefore 4 n-channel bridge config is always better.

      Delete
  21. can you please tell me how 4 mosfet n-channel h bridge works in few sentences.i am in a great confusion.

    ReplyDelete
    Replies
    1. with every alternate pulse from the IC, the diagonally situated mosfets switch ON together alternately.

      Delete
  22. hello sir swagatam
    i have a question about the circuit that i already build. when i test my circuit, one irf 540 from pin #6 get blowed. would you like to tell me why it was happened.
    (sorry for my bad english) thx before

    arif from indonesia

    ReplyDelete
    Replies
    1. Hello Arif,

      please modify the circuit as shown in the following link:

      http://homemadecircuitsandschematics.blogspot.in/2013/05/full-bridge-1-kva-inverter-circuit.html

      Delete
  23. Swagatam
    Thanks for the information,
    I will try it and give you feed back

    ReplyDelete
  24. Thanks
    I am Tunde,
    I have been trying to build an inverter with this H-bridge concept and you have finally come to my rescue
    I am very great full Swagatam.

    ReplyDelete
  25. Hi Mr. Swagatam,

    I've recently taken interest in your blog as I'm working on a similiar project like this. What I'm trying to do is feed in 12VDC into a Flyback converter which will step up to 240VDC. From here, I wish to invert this supply to 240VAC using a H-Bridge inverter.

    Can I email you my schematic and perhaps teach me a few things? If yes, where can I drop my email to?

    Apologies for commenting as Anonymous but this is written in genuine intention to learn from you, Sir.

    Thanks

    ReplyDelete
    Replies
    1. Hi, thanks for reading my blog!

      yes, you can send it to homemadecircuits@gmail.com

      Delete
  26. using solar panel as input can i get 600W at output side in this inverter circuit...??
    and what should be the circuit and specification of transformer and solar panel....???

    ReplyDelete
    Replies
    1. for 600 watts, the solar panel must be at least 200 watts rated and the transformer at 800 watts.

      The battery should have minimum current capacity of 200ah.

      Delete
  27. Hi, Swag,
    I am have built an inverter but the problem lies in the charging area in that when there is power from the mains and the inverter is charging, do we have to build a different charger for the inverter or we should allow the power mosfet to charge the battery.
    Also what are the side effect of charging with the mosfet. And is it advisabe to build a different charger for the inverter.

    Regards

    ReplyDelete
    Replies
    1. Hi Itoro,

      Which circuit are you referring too?
      All inverters mostly use a separate transformer or winding for charging.
      Without actually inspecting the circuit it will be difficult for me to comment precisely.

      Delete
  28. hi swagatam
    this is srinivas cani use this design for 3kva transformer (0-36 volts)220volt out put,please suggest me

    regards

    ReplyDelete
  29. hi sir in this circuit i want to ask you that the IC4049 please sir is N1 start from (2 to 3) and (N2 4 to 5) up to 15? i guess you are understand what i mean cos im confused about it i build it but it don't work that is why im asking maybe i didn't connected the pins correctly thank you sir im looking forward to hear from you son.

    ReplyDelete
    Replies
    1. Hi bianzz, all gates inside the 4049 are identical so you can organize them as per your choice, only the input and outut pins of the selected gates needs to be connected correctly as per the diagram.
      check the datasheet of this IC you will get the idea regarding the involved gate pinouts.

      Delete
  30. ok sir thank you but sir please im still in the 4049 some of the pins is not shown in the circuit such as pin8 and pin16 i can see the pin8 is gnd or ground please sir where is the pin16 connect to? that is all my problem im looking forward to hear from you.

    ReplyDelete
    Replies
    1. bianzz, what does the datasheet say about pin16? Please follow exactly as mentioned in the datasheet

      Delete
  31. hi swagatam,
    thank you for sharing your knowledge
    I have implemeted your circuit but it has some problems.
    the first is oscillating frequency. How 1 khz on the 4017 ic will be 50 hz on the h bridge?

    The second is that the output is 220 volt ac without load but with load the volt decreases suddenly to 40 volt ac.
    How could I preserve the volt with load?

    ReplyDelete
    Replies
    1. Hi Ahmed,

      I have divided the 1khzwith the total number of outputs used from the IC 4017, so 1000/10 = 100Hz, and this fvrequency when divided across two mosfet arms gives 50Hz.

      You can adjust it as per your own calculations if the above results look incorrect.

      The output voltage will depend on trafo wattage and battery AH capacity, they must be sufficiently rated well above the load wattage, otherwise it will drop proportionately.

      Delete

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