Jump to content
Electronics-Lab.com Community

12 V DC to a 220V AC Inverter AMplfier Design


Recommended Posts

Use 2 Mosfets and a 200W transformer for a 200W inverter.
The IRF540 Mosfet is cheap and common. It can conduct a peak current of 33A. Therefore its RMS max current is 23A. It has a max on-resistance of 44 milliohms which produces a voltage drop of 1.0V. The 10V-0-10V transformer gets a loss of 1V in the Mosfets so the circuit's voltage is 9V RMS times the 23A= 207W.
Modern Mosfets with a lower on-resistance and a more powerful transformer can make a more powerful inverter.

Link to comment
Share on other sites


  • Replies 195
  • Created
  • Last Reply

Top Posters In This Topic

Hi Morro,
Four 0.01 ohm resistors in parallel like that is 0.0025 ohms, which is the same as a short piece of wire. It does nothing in the circuit.
All power Mosfets have the diode inside as a part of how they are made. In fact, it is a high-power zener diode which protects the Mosfet from d-s voltage spikes.

post-1706-14279143047888_thumb.png

Link to comment
Share on other sites


the oscillator CD 4047 and the CD4001 really can make it to become modified sine wave? i think in order to make modified sine wave i think we should change from NOR and inside the cd 4001 to XOR gate?

I think NAND gates or NOR gates will work. I didn't look at XOR.
Here are waveforms with NAND gates. NOR would make similar waveforms except the inputs go low to produce a high output.

post-1706-14279143054411_thumb.png

Link to comment
Share on other sites

hi audioguru,

i see the datasheet of the mosfet of IRF540, if the ic CD4047 produces output of 5V the the Vds would be 7.5A from the mosfet. ??? ??? i still cant think of how to supply the 10V to the transformer? is it from the +5 and -5V from the IC??? how do the mosfet do its job??? thanks for your reply :-[

Link to comment
Share on other sites

Hi Morro,
The IRF540 Mosfet is pretty old so has a fairly high on-resistance compared to newer Mosfets. Therefore they will get hot in a powerful inverter.

The CD4047 is Cmos with a supply voltage rating up to 18V. It doesn't need a supply of only 5V like old TTL logic chips, it works fine from 12V and can directly drive 12V to the gates of the Mosfets in a square-wave inverter so that they turn on as hard as they can.
If you are talking about a modified sine-wave inverter then the CD4001 logic gates are also Cmos and can have a 12V supply to directly drive the gates of the Mosfets with 12V.

The center-tap of the transformer is connected to +12V. Then the Mosfets ground one side alternately. There is not a -5V.

Link to comment
Share on other sites

Hi Morro,
The peak voltage of a sine-wave is 1.414 times its RMS value. Its RMS value is the same as the peak voltage of a square-wave. So the peak voltage of a modified sine-wave inverter must be higher than if it is a square-wave inverter.

The fully charged car battery is 13.8V and the Mosfets have a loss of about 1V. Therefore the remaining 12.8V into the 10V winding of a transformer produces close to the correct peak voltage for a sine-wave.

Link to comment
Share on other sites

hi audioguru,

i think there is some problem due to the circuit....i think the CD4047 and CD4001 can be act as the control circuit for the swithing circuit which must consist of four mosfet in order to get the modified sine wave?? in the 1st cycle the signal from the control circuit will go trough the 1st then to the 1st winding of the transformer and back to 4th mosfet to get the +12V at the transformer and get the positive pulse at the output of the transfomer. in the 2nd cycle, the signal from the control signal again pass through the 2nd and 3rd mosfet again to get the negative pulse at the output of the transformer....
pls comment and thanks for your reply

post-21278-14279143081321_thumb.gif

Link to comment
Share on other sites

Hi Kachew,
The center-tap on the transformer is supposed to be used to power the Mosfets while they conduct on each side alternately. Then each end of the transformer's winding is supposed to be driven by the drain of a Mosfet for the full battery voltage to be applied to the half of the winding.

You are using the Mosfets as followers since the transformer is at their sources. So when the logic drives a Mosfet's gate to +12V then the source follows to only about +2V. But then the other end of the winding isn't connected to anything (a turned-off Mosfet) so no current flows in the transformer.

Let the 1st side conduct on its pulse, then a pause while nothing conducts, then the other side conducts, then another pause when nothing conducts.

post-1706-14279143081914_thumb.png

Link to comment
Share on other sites

hi audioguru,

then what u means is the mosfet will only produce only 2V from each mosfet to the transformer so the is unactive in this circuit? then the previous kachew inverter is theoritical working (exclude latest modification) and the mosfet is acts as a switch?? and for 200w output the transformer have to be 12V and 1Amps??
thanks for your reply. ;)

Link to comment
Share on other sites


then what u means is the mosfet will only produce only 2V from each mosfet to the transformer

Yes. An N-channel Mosfet is turned on by making its gate about +10V higher than its source. Your circuit had the input going to +12V from the 4001 gate, so its source which is connected to the transformer goes up to only +2V.

so the is unactive in this circuit?

The other end of the transformer winding is connected to a turned-off Mosfet, so no current flows and the circuit does nothing.

then the previous kachew inverter is theoritical working (exclude latest modification) and the mosfet is acts as a switch??

Yes, it was correct since the transformer's center-tap connected to +12V and the drains of the Mosfets pulled their side of the transformer's winding to ground.

and for 200w output the transformer have to be 12V and 1Amps??

No. 12V and 1A is only 12W. Your transformer must be 200W for the output plus maybe 40W for heating the circuit, and must be 10V to make the peak voltage of the modified sine-wave high enough. So the transformer must be 10V-0-10V at 240VA which is 24A. A BIG transformer.
Link to comment
Share on other sites

hi audioguru,
i think i know what is kachew tryin to deliver.... ;D the concept can be found in any power electronics book ;D ;D and i also attach a circuit i think is similar to your concept using the cd 4001....and audioguru can u try to explain your circuit using the cd 4001 and mosfet as a switch?  the center tap transformer is similar to 2 transformer circuit as i attach? thanks for your information and reply ;D ;D

Figure.rar

Link to comment
Share on other sites

Hi Sonny,
You make everything very confusing when you use Kachew's account. You should register on this site as yourself. Then login as yourself each time.

You attached a DOC file instead of a GIF or PNG file for your schematics, and you compressed it as a RAR. Just attach the schematics as a GIF or as a PNG.

The CD4047 has an oscillator output and has two opposing Q and Q-not outputs which are the oscillator divided by 2. When you gate those outputs with CD4001 NOR gates then the outputs of the gates drive Mosfets with the correct timing for a modified sine-wave inverter.

post-1706-14279143084506_thumb.png

Link to comment
Share on other sites

hi audioguru,
may i know the transition of the pulse where both mosfet are turned off? you only shows the transition where 1st and second mosfet are turned on....and i would also like to ask why we want to use the drain source of the mosfet to ground the center tap transformer?
thanks for your reply :D :D

Link to comment
Share on other sites


may i know the transition of the pulse where both mosfet are turned off?

I showed it a few days ago. Here it is again clearer.

why we want to use the drain source of the mosfet to ground the center tap transformer?

What is a drain source? A Mosfet has a drain pin and a source pin. On these N-channel Mosfets, the sources are connected to ground and the drains are connected to the ends of the transformer winding. The center-tap is connected to +12V. Here is your schematic.

post-1706-14279143085167_thumb.png

post-1706-14279143085261_thumb.png

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
  • Create New...