12 V DC to a 220V AC Inverter AMplfier Design

[audioguru2]

A square-wave inverter 's output goes: positive pulse, negative pulse, positive pulse again, negative pulse again and repeats.

A simple modified sine-wave inverter's output goes: positive pulse, 0V pause, negative pulse, 0V pause, positive pulse again, 0V pause again, negative pulse again, 0V pause again and repeats.
It is not difficult to make the 0V pauses.

I don't bother with a modified sine-wave inverter because tools with variable speed motors and other things don't work properly with it.
 

 

[kachew]

dear audio guru do u have any idea to implement this?? for example we take kasamiko inverter how do we make it from square wave to modified sine wave?? ??? ???thanks lots

 

[audioguru2]

You could make a modified sine-wave with a CD4047 oscillator and a CD4001 quad NOR gate or CD4011 quad NAND gate.
The oscillator of the CD4047 and its Q output would be gated and drive one of the push-pull output transistors. The oscillator output and the Q-Not output would be gated and drive the other push-pull output transistor.

 

[kachew]

dear audioguru can u show or tell me how can i connect it to be modified sine wave?? can i use the circuit i posted here http://www.electronics-lab.com/forum/index.php?topic=1360.112 to change from sine wave to modified sine wave inverter? cos i wan to use mosfet than transistor to increase the efficiency of the inverter...thanks lots ;D ;D

 

[audioguru2]

I already told you how to connect a CD4047 with logic gates that drive your Mosfets with a modified sine-wave. The timing diagram looks like this:
EDIT: Corrected the clock's pin number.

View attachment 39543

 

[kachew]

hi audioguru,

i just wan to know the use which pin to connect to the pin Q and inverted Q of cd 4047? :'( :'(
and how about i add LM358 amplifier to increase the output current from the CD4047 in order to increase the efficiency? ??? ???

 

[audioguru2]

i just wan to know the use which pin to connect to the pin Q and inverted Q of cd 4047?

Sorry, I had the pin number of the clock for the CD4047 wrong. I fixed it.
Connect the pin 13 and pin 10 to one gate of a CD4011 which drives the 1st Mosfet. Connect the pin 13 and pin 11 to another gate of the CD4011 and it drives the 2nd Mosfet.

how about i add LM358 amplifier to increase the output current from the CD4047 in order to increase the efficiency?

At only 50Hz or 60Hz, I don't think the switching speed makes any difference. If it was 50kHz or 500kHz then a lot of current is needed to charge and discharge the high gate capacitance of the Mosfets for them to switch quickly so they don't get hot. An LM358 is about the slowest opamp that is made, even slower than an old 741 opamp. It would be lousy for driving Mosfets.

 

[kachew]

dear audioguru,

GUru @ master hehe ;D ;D then do u have any suggestion? and i saw u posting in the arron cake forum too....i can see u help lots ppl there... ;D ;D ;D good jobs haha...i will try to generate my circuit and post it soon....any defects there pls help me to detect... ;D ;D thanks

 

[audioguru2]

Sketch the circuit of a modified sine-wave inverter and I will check it for you. Don't forget the transformer must have an output voltage about 1.414 times higher than the transformer in a square-wave inverter, to create the peak voltage of the sine-wave. Therefore instead of a 230V to 24V center-tapped (12V-0-12V) transformer you need a 230V to 17V center-tapped (8.5V-0-8.5V) transformer.

 

[kachew]

dear audioguru,
oh....thanks ya lots ;D ;D oh ya...do you use any messenger such as yahoo messenger? or msn messenger?? i would like to add you in my list thanks again

 

[kachew]

dear nthrower,
wow...how u did it? using the pwm? how much the efficiency? can u upload the schematic of your design..thanks

 

[audioguru2]

A d-to-a converter creates an analog sine-wave so the efficiency is the same as an analog power amplifier, about only 60%. You lose nearly half the battery power.
It would be the same if a Wien Bridge or any other kind of analog sine-wave oscillator is used.

 

[kachew]

hi audioguru,

This is the circuit that i draw myself ;D ;D can u pls help me with the modification or check the circuit for me?? thanks...oh ya...1 more thing...how to make it to have continous power of 150W ??? ??? thanks again

View attachment 39552

 

[kachew]

sorry the circuit posted seems unclear so i repost again...

 

[kachew]

this is in the rar file

inverter.rar

 

[audioguru2]

Hi Kachew,
It is hard to see your schematic. Make it on the computer with Microsoft Paint or another program.

I didn't check your CD4047 circuit. It should be the same as the 500W square-wave inverter.

You show two CD4001 ICs when only one is needed. A single CD4001 has 4 gates inside.
One gate of the CD4001 needs one input from the pin 13 oscillator pin of the CD4047 and its other input from pin 10. The 2nd CD4001 gate also needs one input from the pin 13 oscillator pin of the CD4047 and its other input from pin 11. The two unused gates in the CD4001 IC should have their inputs grounded.

You have an LM393 dual comparator instead of an opamp. A comparator is not supposed to have negative feedback. It oscillates at a very high frequency when it has negative feedback like yours has. An opamp is designed to have negative feedback.
A comparator has a single transistor at its output with an "open collector" so it doesn't have anything to pull the signal positive.

You have 100k resistors at the outputs of the comparators. A resistor isn't needed.

You have 33k resistors feeding the gates of power Mosfets. Power Mosfets have an extremely high gate capacitance (12nF) which causes them to turn on in 33k x 12n= 396us plus ramping caused by Miller capacitance, which is slow enough to cause the Mosfets to overheat.

The 100k resistors in series with the capacitors at the transformer have way too high a value to do anything.

The circuit needs a single +12V power supply and ground. Yours shows a +12V and a -12V which is 24V.

If you select power Mosfets with a low turn on voltage then a single pair can drive 500W or more.

 

[kachew]

dear audioguru.,
thanks for checkin the circuit for me... ;D ;D and so sorry for the unclear circuit coz i draw and use digicam to take the circuit i drawn...audioguru do u hav any recommendation for the software to draw the circuit...coz i dont have any software for that...and for the comparator part shall i change to the opamp?? which opamp is more suit for the inverter? for the power mosfet i will try to find a suitable 1 and redesign the circuit as u guide me...thanks

 

[kachew]

dear audioguru,

is it the 396us is the operation cycle for the mosfet?? so its take to 396us to amplified the voltage in the 1st mosfet in the positive cycle and the same time to amplified the negative cycle in the 2nd mosfet...so is it u mean that the resistor in the gate mosfet the larger the better to provide sufficient time to have to cool down time for the 1st mosfet? or the smaller value for the resistor for fast switching??

 

[audioguru2]

do u hav any recommendation for the software to draw the circuit...coz i dont have any software for that.

I use Microsoft Paint program. I make straight lines with the Shift key down and I copy and paste parts and pieces of other schematics and from datasheets.

for the comparator part shall i change to the opamp?? which opamp is more suit for the inverter?

Yes, use an opamp. The LM358 has outputs that go to ground.

is it the 396us is the operation cycle for the mosfet??

396us is the time for the very high value of the 33k resistor to charge or discharge the very high 12nF input capacitance of the Mosfet. You want the Mosfet to switch as fast as possible so it doesn't heat. A low resistance will charge the capacitance quicker, use 1k. 

 

[Muhammad Abu Bakar]

I use Microsoft Paint program. I make straight lines with the Shift key down

Very good trick AU. You are genious. From where u learned it.

Thanks