Inverter Circuit 12V DC to 230VAC Sine Wave

[ante1]

Hi Audioguru,

Yes you are correct, there are twice the number or more of the N type around but the Rds and the price does not differ that much. However I agree, N-channel would be a better choice for this inverter. I bet they came from his junkbox ! 

 

[MP1]

The project of the 500W square wave inverter is here: http://www.electronics-lab.com/projects/power/033/index.html and is updated with a circuit that works.

You could make a pure sine wave inverter with a high current linear amplifier driving a transformer and waste a lot of battery power as heat, or you could make a complicated pulse-width-modulation (class-D) circuit drive a transformer with variable width pulses and waste less power. I have never seen a circuit because a pure sine wave is rarely needed.

That thread is actually a re-make of the project and not a correction. There were not many problems in it. Some traces were connected where they should not be and the decimals were off in the clock components. Either way, you have a square wave. Using a linear amp for a sine wave will waste too much energy. If you live in the arctic, it could certainly be beneficial as a heater.

Here is a schematic from a link ante sent me some time ago. This might be what you are looking for.

MP
View attachment 37662

 

[MP1]

Another form of sinewave conversion and a much more effective way to do this is to use a micro to generate varying levels of square waves which are very close together in timing and which, when smoothed with a capacitor, will become a sine wave. This will give you the efficiency of a square wave inverter, but a sinewave output. See the drawing below. It is not a very good one but gives you an idea. You would need many more waves than in this depiction to get a smooth sine wave.
Hope this helps.

MP

View attachment 37663

 

[audioguru2]

The linear sine-wave inverter/heater is nice because it regulates the output voltage.
The digital then smoothed sine-wave circuit is how class-D audio amplifiers work.
;D

 

[MP1]

actually class D is a far cry from being digital. It is PWM. Class D uses triangle wave controlled by input signal (sine) to produce a PWM type of controlling signal. I was referring to a constant clocked squarewave controlled by a sinewave to produce varying heights of squarewaves, which when smoothed, creates a representative sinewave. Class D produces all the same height PWM waves. This is less useable as an inverter type circuit.  ;D

MP

View attachment 37665

 

[audioguru2]

Actually, since the digital PWM waves of a class-D amplifier all have the same height, and are also constantly clocked, there is far less heating than in your proposed "vaying heights" plan. Most fairly high power class-D amplifiers are surface-mount, and don't even need a heatsink.
Class-D amps are perfect for a sine-wave inverter. ;D

View attachment 37667

 

[MP1]

Yeah, even TI would like to pass this chip off as a digital experience. Your PWM controlling signal does not make this a digital project. But go for it. I have seen much worse projects on the web.

MP

 

[audioguru2]

MP,
Is your proposed digital sine wave amplifier or inverter with "varying heights of its steps" on the web?
What would be its efficiency as an amplifier or inverter?

I showed a square-wave inverter and a modified sine-wave inverter with large digital steps with a pause in between. Their efficiency using transistors is about 80%, about 90% when using Mosfets.
I showed a digital PWM class-D amplifier that could be an inverter. Its efficiency is about 90%.

You showed an analog sine-wave inverter with an efficiency of only about 60%.
How on earth could a sine-wave be made with pulses of varying heights and not waste a lot of power? ???

 

[MP1]

You showed an analog sine-wave inverter with an efficiency of only about 60%.
How on earth could a sine-wave be made with pulses of varying heights and not waste a lot of power? ???

Actually, I have not shown you a design of anything. Is it common for a theory expert to build a complete inverter from a picture of a pulse? Perhaps you did not build it well.

MP

 

[audioguru2]

Actually, I have not shown you a design of anything.

You showed Ante's analog sine-wave inverter with an efficiency of only about 60%.

EDIT: The output Mosfets operate in class-A, so the inverter's efficiency might be as low as 33%.

 

[Alun]

audioguru,
PWM isn't digital, it's squarewave who's duty cycle depends on an external signal, you could also look at it as a complex wave with harminics from both the carier and modulating signal up to (in theory) infinity, on the output of the amplifier is a low pass filter that only passes the lower audio frequencies. Digital is totally differant it's used where tow states represent 0s and 1s, the only thing PWM has in common with digital is the transistors are either on of off. I wish people would stop calling class-D amplification digital - it's very confusing, even more so to newbs.

MP,
I'm very interested about you would go about generating differant voltage steps without loosing a hell of a load of power or using a switching regulator which would be  effectively  class-D amplification anyway.

 

[audioguru2]

Hi Alun,
Of course I know that a PWM class-D amplifier isn't truely digital with 1's and 0's.
It isn't truely analog either, it is a switching type.

My extremely low distortion sine-wave generator uses varying step heights like MP's idea.
It uses a CD4018 Johnson walking ring counter driving 4 resistors with special ratios to produce a sine-wave with 10 steps and no distortion up to the 9th harmonic.
I use a switched-capacitor lowpass filter IC to remove remaining harmonics. ;D

 

[Alun]

How will this help with the power wasting problem though?

 

[audioguru2]

Hi Alun,
You and I don't think it is possible to produce a sine-wave inverter having many voltage steps without wasting a lot of power.
I think the only way is by using only 3 voltage steps to get 230VAC RMS out:

View attachment 37671

 

[aakaash]

Hi,
I want to built a ckt to drive CFL directly from battery.
Can  anybody yell me something abt it ?
Does it need pure sine wave or not?
Ckt diagram?
AAKAASH

 

[audioguru2]

Hi Sasi,
You have a very powerful-looking square-wave inverter with PWM voltage regulation.
How many kW?

You can see any of Silicon Chip's projects for free if you find them in Google. I entered Silicon Chip Compact Fluorescent and found a link to their whole project for free:

View attachment 37676

 

[audioguru2]

OK guys,
Mixos should have a contest.
We can combine the last few posts which have all the ingredients to make a powerful, efficient, voltage-regulating pure-sine-wave inverter. Like the Compact Fluorescent Driver, it can even have a ground-fault interrupter built-in.
It can use any of the SMPS PWM controller ICs like Sasi's european one or the TL494 or TL497. It can use as many Mosfets as you like for tonnes of power.

A good challenge for me, but what do I need an inverter for with Niagara Falls nearby churning-out kilo-megawatts continuously? My ship is beached (my joke on another forum where everyone pins their locaton on earth-google's satellite-pics globe), so I can't use an inverter there.

Here's what a PWM stepped sine-wave looks like:

View attachment 37677

 

[nura100]

Hello Forum!

I have been in the inverter & UPS Field for Quite Some time,

I have a manufacturing unit For Inverters & UPS, M/s. Sunlite Technologies, HYD, India.

I'd Like to Comment on Mr. SASIDHARAN's

 

[MP1]

You showed Ante's analog sine-wave inverter with an efficiency of only about 60%.

EDIT: The output Mosfets operate in class-A, so the inverter's efficiency might be as low as 33%.

Just passing on something that ante posted years ago. Not my design, nor have I made the circuit. If you go back and read the posts, you will see that I was talking about several different methods, but not advising to use any particular one. I think you take posts much too personally, audioguru.....and it seems that when you have the urge to argue with someone, you twist the quotes to make fuel for your argument. (for example, trying to prove class D is digital, then admitting to alun you knew it was not). I will not add to this kaos. There is no longer anything constructive in this conversation.

MP

 

[audioguru2]

[There is no longer anything constructive in this conversation.

Sure there is!
We found ways to make a really good inverter by discussing these things.
It will work exactly like a class-D "digital" amplifier. ;D