Aaron's Homepage Forum
Aaron's Homepage Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Electronics
 Power Supply
 12/120V inverter again
 New Topic  Reply to Topic
 Printer Friendly
Previous Page | Next Page
Author Previous Topic Topic Next Topic
Page: of 63

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 19 2008 :  1:50:01 PM  Show Profile  Reply with Quote
I have never made a PWM circuit for an inverter. I made one to control the speed of a DC electric motor.

The LM393 and LM339 are not opamps. They are comparators. Their outputs are the collector of an NPN transistor not the complete output circuit that opamps have. The low battery cut-off circuit will need to be changed a little to use them.
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 20 2008 :  12:00:48 PM  Show Profile  Reply with Quote
The comparator has only the collector of a single NPN transistor at its output. It needs a resistor connected to the positive supply to pull the output high. Opamps have multiple transistors and PNP pullup transistors at their outputs.
But the LM393 and LM339 comparators are low power so their minimum output current is low, only 6ma. Opamps have a minimum output current of 20mA.

Why use a low power dual comparator or quad comparator to replace a single more powerful opamp? What will you do with the extra comparators?
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 21 2008 :  12:26:02 AM  Show Profile  Reply with Quote
Look at the datasheet for an LM1458 dual opamp. The MC1458 is the same. Their spec's are the same as a 741 opamp.

Why will the battery voltage be too high??
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 21 2008 :  11:41:41 AM  Show Profile  Reply with Quote
The high and low cutoff circuit STOPS the inverter when the battery voltage is too high or is too low. I think Dennis uses it to stop the inverter from working when somebody connects a 24V battery to it.
The circuit with the two opamps as a window comparator does not regulate and does not sense the output voltage so it does not regulate the output voltage.
Go to Top of Page

rauf
New Member

Pakistan
2 Posts

Posted - May 21 2008 :  12:44:09 PM  Show Profile  Send rauf an AOL message  Click to see rauf's MSN Messenger address  Reply with Quote
quote:
Originally posted by audioguru

quote:
Originally posted by mrenjan

One Question to AudioGuru.. Is there any advantage of using 2N3055 instead of Mosfet's like IRF540 directly tied to CD 4047. We dont even need the OP-amps since Mosfet requires only less Drive current. Probably the only other change required is in the Transformer side (9-0-9 instead of 12-0-12). I thought the efficiancy of Mosfet is much higher than Transistor since leakage current is less. Not sure whether i am wrong.


2N3055 transistors were used in the 100W and 500W inverter because the circuit is very old and 2N3055 transistors atre available in countries that don't have Mosfets. Mosfets are much better.

The IRF540 Mosfet is also getting pretty old since much better Mosfets are available now.

The CD4047 can directly drive two Mosfets in an inverter and the output power depends on their current rating and the size of the heatsink. Cheap Chinese inverters use Mosfets.

Efficiency is determined by how much power is wasted as heat in the transistors when they conduct, not leakage current.
A 2N3055 transistor has a max saturation voltage of 3V at a collector current of 10A and a huge base current of 3.3A. That is 35W of heat for a 100W inverter.
An IRF540 Mosfet has a max saturation voltage of 0.44V at 10A so wastes only 4.4W in a 100W inverter. Better Mosfets would operate cooler and therefore the efficiency would be higher.

If you use a 9-0-9 transformer with Mosfets then with a fully charged battery at 13.8v the output voltage will be 170VAC instead of 115VAC or will be 341VAC instead of 230VAC.

If you use a 12-0-12 transformer with Mosfets and a fully charged battery then the output will be 128VAC instead of 115VAC and will be 256VAC instead of 230VAC.

Go to Top of Page

rauf
New Member

Pakistan
2 Posts

Posted - May 21 2008 :  12:45:04 PM  Show Profile  Send rauf an AOL message  Click to see rauf's MSN Messenger address  Reply with Quote
quote:
Originally posted by audioguru

quote:
Originally posted by mrenjan

One Question to AudioGuru.. Is there any advantage of using 2N3055 instead of Mosfet's like IRF540 directly tied to CD 4047. We dont even need the OP-amps since Mosfet requires only less Drive current. Probably the only other change required is in the Transformer side (9-0-9 instead of 12-0-12). I thought the efficiancy of Mosfet is much higher than Transistor since leakage current is less. Not sure whether i am wrong.


2N3055 transistors were used in the 100W and 500W inverter because the circuit is very old and 2N3055 transistors atre available in countries that don't have Mosfets. Mosfets are much better.

The IRF540 Mosfet is also getting pretty old since much better Mosfets are available now.

The CD4047 can directly drive two Mosfets in an inverter and the output power depends on their current rating and the size of the heatsink. Cheap Chinese inverters use Mosfets.

Efficiency is determined by how much power is wasted as heat in the transistors when they conduct, not leakage current.
A 2N3055 transistor has a max saturation voltage of 3V at a collector current of 10A and a huge base current of 3.3A. That is 35W of heat for a 100W inverter.
An IRF540 Mosfet has a max saturation voltage of 0.44V at 10A so wastes only 4.4W in a 100W inverter. Better Mosfets would operate cooler and therefore the efficiency would be higher.

If you use a 9-0-9 transformer with Mosfets then with a fully charged battery at 13.8v the output voltage will be 170VAC instead of 115VAC or will be 341VAC instead of 230VAC.

If you use a 12-0-12 transformer with Mosfets and a fully charged battery then the output will be 128VAC instead of 115VAC and will be 256VAC instead of 230VAC.

Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 22 2008 :  12:29:13 AM  Show Profile  Reply with Quote
A lead-acid battery is not fully charged when its voltage reaches a certain voltage. It is fully charged when its current drops to a certain low amount.

Go to the Battery University and read about it. http://www.batteryuniversity.com/partone-13.htm

Download Attachment: lead-acid battery charging.PNG
19.96 KB

Go to Top of Page

ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - May 22 2008 :  9:25:23 PM  Show Profile  Reply with Quote
Hi audioguru, as you can see I am new here. But not particularly new to electronics. I am a EEET level 1 student who likes to do practicals whenever I have free time. I am currently working on an inverter project. I've tried Aaron's schematic twice and ended up with 4 fried transistors and 3 fried capacitors. After that I decided to read the forums from pages 1-45 . Since you are the expert hear can you help me design an inverter circuit? All I have to start is a 10A Transformer with 12v-0-12v IN and 110/220v 60/50Hz OUT. This would be able to deliver 120W right? Please feel free to correct me if I am wrong, I am eager to learn. Oh! I would like to run a 110W Television or a 100W radio on it. Would these be able to work on a square wave?

Edited by - ElectroEgg on May 23 2008 01:28:43 AM
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 23 2008 :  10:50:08 AM  Show Profile  Reply with Quote
Hi ElecroEgg,
I have already helped enough people make a very simple inverter on this website.
A radio and TV might not work from a square-wave inverter because their power supply usually runs on the peak voltage of a sine-wave which is 1.414 times higher than a square-wave. In The Philippines they have TVs that run from any voltage from 80V to 150V and they work fine from a simple square-wave inverter.

Your little transformer is designed to have an output of 12V-0V-12V when it has a load of 10A and the primary has 110V or 220V. Its output is probably 13.5V-0V-13.5V without a load. So when you turn it around and put a 12V square-wave into it, its output voltage will be 12V/13.5V= 0.89 times what you expect and lower when loaded.
A transformer with a higher power rating will not have such a high loss.

The circuit will not give a 12V square-wave because the transistors or Mosfets have a voltage loss (that heats them). So the output of an inverter using your transformer will be about 100W at 90V or 180V.
Go to Top of Page

ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - May 23 2008 :  9:53:02 PM  Show Profile  Reply with Quote
Hmmm...That's bad news Audioguru. Because that was the largest Transformer I got after checking various electronic shops. I payed a wopping $160TT ($20ca) for it and at that same store I saw a 400w inverter for $400. I will be at a great loss if I will have to buy another larger one (which obviously will cost more than the first). Oh well I got to forget my losses and see if I get a 15 or 20A Transformer. It's just that I get such a great feeling when I build something myself. Thanks a lot for your help.
Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 23 2008 :  11:01:42 PM  Show Profile  Reply with Quote
Hi ElectroEgg,
$20ca is nothing in Canada. I can buy a pretty good 100W inverter for $20ca. I think it has a modified sine-wave output but it mighr have a true sine-wave output so it can power anything up to 100W. It doesn't use a huge heavy transformer. It uses a voltage stepup circuit that operates at a high frequency so a small transformer is used and it uses high voltage Moafets instead of transistors.
Go to Top of Page

ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - May 24 2008 :  07:26:27 AM  Show Profile  Reply with Quote
Ok. Well I'm off for components searching. I hope I get the required ones for your 100w inverter. Since it's a square wave I will basically be able to operate only the lights at my home then. Hmmm....I'm just wondering. Do you know how to make a sine wave inveter also?
Go to Top of Page

kivdenn
Nobel Prize Winner

Uganda
535 Posts

Posted - May 24 2008 :  09:54:51 AM  Show Profile  Reply with Quote
Hey am working on 48V DC-AC inverter circuit bellow.Please look at it and tell me if it can work.

Download Attachment: 48v inverter.jpg
70.37 KB



I have also tried to make a 48V low battery disconnect circuit for it. please also have a look at it and tell me if it can work. Thanks
Dennis

Download Attachment: 48v sensor.jpg
58.2 KB

Go to Top of Page

audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 24 2008 :  6:59:18 PM  Show Profile  Reply with Quote
I am tired of checking your millions of circuits. Maybe somebody else can.
Go to Top of Page

ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - May 24 2008 :  9:43:48 PM  Show Profile  Reply with Quote
Hi Audioguru,
If you don't mind can you tell me what formulas you used and what calculations you did to determine that a 47k resistor will give 50Hz output and a 39K will give 60Hz output.

Edited by - ElectroEgg on May 24 2008 9:58:20 PM
Go to Top of Page
Page: of 63 Previous Topic Topic Next Topic  
Previous Page | Next Page
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Aaron's Homepage Forum © 1995-2020 AARONCAKE.NET Go To Top Of Page
This page was generated in 0.16 seconds. Snitz Forums 2000