How may I increase the watt in this invertor

[Willen]

How to increase the output AC watt in this invertor?
I should have to increase the ampere of battery and trasnsformer but it's not enough to get high wattt. May I connect the IRFZ44 mosfet in parallel to get totally high watt? Please help!!
www.inverter-circuit.com/12v-to-220...2-220-ac-to-dc-inverter-circuit-mosfet-irfz44

 

[MrAl]

Hi there,


Connecting MOSFETs in parallel is a valid technique for increasing the output power for amplifiers or power supplies. More than two can be paralleled too. Your circuit there however also has an output transformer that appears to be rated at 5 amps. That means that if it is now being driven at 2.5 amps you can double the drive current. If it is already being driven at 5 amps however, you cant go any higher. That would mean in addition to paralleling the MOSFETs you'd also have to parallel the transformers which means another transformer, or get a transformer that can handle 10 amps instead of only 5 amps.
If the transformer is very conservatively rated you might squeeze a little more out of it, but if it overheats you'll know you are driving it too hard. Monitor the temperature at full load and see how hot it gets. Some wire is rated for only 80 deg C so you'll have to stay under that or risk burning up the transformer.

If you intend to parallel you should read up on the techniques for doing this properly first.

The better way to make an inverter is to make a DC to DC converter, then use an H bridge to convert the DC into AC for the output. This way you dont need a bulky low frequency transformer.

 

[ronsimpson]

My anti-virus program blocked two programs from attacking my computer from that web-sight.

Where is the bypass capacitor on the CD4047? There should be a capacitor on the "+12V". All over the internet there are inverter circuits that almost work, with no details, and missing pieces.

 

[Willen]

The better way to make an inverter is to make a DC to DC converter, then use an H bridge to convert the DC into AC for the output. This way you dont need a bulky low frequency transformer.

Make me clear about it please!! H bridge means???

 

[Willen]

My anti-virus program blocked two programs from attacking my computer from that web-sight.

Where is the bypass capacitor on the CD4047? There should be a capacitor on the "+12V". All over the internet there are inverter circuits that almost work, with no details, and missing pieces.

A capacitor between +12 and Ground? Or capacitor for coupling +12 and IC? For why?
(Wow! You have a powerful anti-virus ha ha But I'm using Java cell phone instead of PC, so nothing will happen)

 

[ronsimpson]

Any IC should have a capacitor from power to ground. This is good engineering practice.

With an inverter there are probably long wires back to the batter. You need capacitors from the transformer center tap of the primary back to ground. This helps fight the effect of long wires. With out this capacitor the +12V will be pulled to ground when a FET first turns on. When the FET turns off the +12V might jump to 20 volts for a very short time. This noise on the +12V may reset the CD4017 or it could kill the IC.

The +12V will be +14V or higher when the batteries are charging.

 

[MrAl]

Make me clear about it please!! H bridge means???

Hi,

An H bridge is a transistor bridge circuit made up of 4 transistors. The top of the circuit is fed with the DC voltage. The bottom of the circuit is connected to ground. The 4 transistors are made to turn on only 2 at a time, so that depending on which 2 you turn on the output of the circuit becomes either positive or negative. This means if you have 150v DC on your DC to DC step up power supply, you can turn that into plus and minus 150v AC which is almost like the regular home AC line.

So the idea would be to use a DC to DC converter to get from say 12v DC to 145v DC, then use the H bridge to get to plus and minus 145v DC at 68.5 percent duty cycle which emulates a real AC line voltage.

They call it an "H" bridge because the transistors are arranged like the lines that make up the capital letter "H".

In the figure below note that the output is taken not from ground but from the center of the two transistor on each side.
When Q1 and Q4 are turned on the output is positive, and then Q3 and Q2 are turned on the output is negative. That means it can be an AC output if we turn them on and off in the right sequence.

    H Bridge Circuit Using Bipolar Transistors
    -----------------------------------------
          (scroll to see the entire circuit)


  +145v o---------+------------------+
                  |                  |
            | ,---o            | ,---o  
            |/                 |/       
         o--|   Q1          o--|  Q3      
            |\                 |\       
            | \>--o            | \>--o  
                  |                  |   
                  +---O  OUT  O------+
                  |                  |   
            | ,---o            | ,---o  
            |/                 |/       
         o--|   Q2          o--|  Q4      
            |\                 |\       
            | \>--o            | \>--o  
                  |                  |
                  +-------+----------+
                          |
                        --+--
                         ---  Ground
                          -

 

[Willen]

An H bridge is a transistor bridge circuit made up of 4 transistors. The top of the circuit is fed with the DC voltage.

You mean ''invertor'' without transformer,isn't it? WOW! If you have got this kind of invertor circuit, (12V input DC to 220V AC output) please share me link (URL).

 

[MrAl]

Hi,


No i dont have a link. Also, you may still need a transformer because to get from 12vdc to 145vdc (for 120vac output) you need a DC to DC converter that can boost 12v to 145v. For a 220vac output you'd need 12vdc to 266vdc and i dont think you can do that with a boost converter, you'd need a transformer on the input. The difference is the transformer for the DC to DC converter can be much smaller than if you tried to boost the output on the AC side which is low frequency. On the DC side you can use a higher frequency like 100kHz, which means the transformer is much smaller.

To do something like this, you could first investigate how to design a DC to DC converter for 12vdc to 266vdc. Then build an H bridge and fire the transistors Q1 and Q4 with a pulse width of 68.5 percent of a half cycle of the AC output, then turn them off and fire Q2 and Q3 with a pulse width of 68.5 percent of a half cycle spaced properly away from the other transistors turning on. This would give you the pseudo sine output that many low cost inverters typically use.

It's temping to try to use a boost converter for the DC to DC converter, but im not sure if you can get such a high ratio of output to input voltages like 266/12, which is really really high but would only required an inductor. Im not sure if you could even get 145/12 using just an inductor. It's probably better to use a transformer type boost circuit.

 

[tcmtech]

It's temping to try to use a boost converter for the DC to DC converter, but im not sure if you can get such a high ratio of output to input voltages like 266/12, which is really really high but would only required an inductor. Im not sure if you could even get 145/12 using just an inductor.

Use a tapped inductor. Basically the low voltage high current winding is in series with the higher voltage lower current winding like how a common autotransformer is designed for doing buck/boost work on AC lines.

 

[MrAl]

Hi,

Yes, it doesnt need to be a transformer with isolation either.

 

[Willen]

On this invertor circuit (circuit of my 1st post) I have a problem to get exact transformer so going to make myself. May I calculate the turns of transformer regarding that- the transformer has 12V input and 220V AC output? I am going to wind primary and secondary coil using a formula of basic transformer. Can I wind like this?:-

¤ N1=70 turns (here is two input-Drain1 and Drain2, so here will be two coils of 70 turns)
¤ V1=12V
¤V2=220V
¤N2=V2 x N1 / V1
=1283 turns.
Does it work? What is the best SWG (on N1 and N2) for high watt like 100watt or 200 watt?

 

[ChrisP58]

What are you using for a core?

For line frequency (50/60Hz) transformers, you want to fill as much of the winding window as you can with copper. Half of the window area for the primary winding, and half for the secondary. So, use the largest size wire that you can get to fit the space.

When winding the primary, be careful to properly phase the two windings.

To recap other posts in this thread:
1) Yes, you can parallel mosfets for higher current. I would suggest giving each one their own gate resistor though. I can't give you a good technical reason, but it will make troubleshooting easier.
2) You absolutely need some capacitance from pin 14 to ground. Considering the 220 ohm supply resistor, I would suggest t least a 10uf electrolytic, and a 0.1uF ceramic. Position these as close as possible to the IC pins.

 

[Willen]

What are you using for a core?

I am using a transformer's iron core, I found it on my old big Audio Amplifier. Now, can I wind coil on that core according to equation of above?