DC to AC inverter improvents

[transforman2]

Ok audioguru than you a lot for your information. I will remove then the 100ohm resistor. Have you got something to recommend to me for a high power fast switching PNP and NPN transistors ?

Thanks

 

[audioguru]

Most inverters are made with a center-tapped transformer primary winding and two N-channel Mosfets.

 

[transforman2]

Yea, i just want to keep things simple by avoiding center tapped transformers

 

[KeepItSimpleStupid]

When you bifilar wind (two wires at the same time) the xformer, there is essentilly no difference in time to wind.

 

[transforman2]

Can i put x2 TIP transistors in parallel in order to increase the current ?

 

[audioguru]

Transistors have a wide spread of spec's. Unless they are matched (buy a few hundred, test them all then group them) then the most sensitive one will hog all the current and the other one does nothing.

 

[audioguru]

The 555 has an output voltage loss of 5V p-p when its load is 200mA and the output transistors have an additional output voltage loss of about 3V p-p. The output coupling capacitor also has a loss of about 1V p-p for a total loss of 9V p-p which is why the original circuit with an additional loss in its inductor did not work.

 

[transforman2]

Ok i have some news. I removed one small transformer from a mobile charger and i connected it in reverse. It has 6 pins out. 2 for output 2 for primary and 2 for driver. I connected the output of my 555 circuit with the primary and i got only about 60v, same with the driver. This transformer is i guess 6v-0-6v to 220 so it looks like my circuit is not the best for this purpose. I will try to change the circuit and make something like this to see how it is going to work.

I tried to drive the small transformer with this circuit that i found from net but i used a BU808DFI from a TV but it didn't work. The transistor was getting hot and it did not producing any output. Also i ordered this from ebay, it is suppose to run with that circuit but i t also does not working.

Thanks

 

[dr pepper]

If you use 2 bipolar trannies in parallel you need emmiter resistors to balance the current across them.
And really you should design your own trans for the system, excellent It is a free transformer calc that might do the trick.

 

[chemelec]

Ok i have some news. I removed one small transformer from a mobile charger and i connected it in reverse. It has 6 pins out. 2 for output 2 for primary and 2 for driver. I connected the output of my 555 circuit with the primary and i got only about 60v, same with the driver. This transformer is i guess 6v-0-6v to 220 so it looks like my circuit is not the best for this purpose. I will try to change the circuit and make something like this to see how it is going to work.

I tried to drive the small transformer with this circuit that i found from net but i used a BU808DFI from a TV but it didn't work. The transistor was getting hot and it did not producing any output. Also i ordered this from ebay, it is suppose to run with that circuit but i t also does not working.

Thanks

You Need Base Resistors to Each Transistor.
And Did you put Suitable Heat Sinks on the Transistors?

 

[transforman2]

Yea i have put Heat Sinks on both of them. I have tried to make my own transformer but i failed too. I thought that i did not coil it properly cause i was taken the same results, that is why i tried one from a mobile charger but the results are the same. In my opinion the problem is the circuit.

 

[chemelec]

What Size of transformer Core?
How did you Wind the Transformer?
Number of Turns and Wire Sizes on both the Primary and Secondary?

Well it is Not a very good circuit, but It can work.
However Just use Two of the Transistors, Not all Four.
Also put a 100 or 220 Ohm Resistor between Pin 3 and the Base of these transistors.
Depending on How much Wire on your Primary, you might Eliminate C8.

 

[transforman2]

Well i tried one with about 600 turns primary and 20 turns secondary and i got about 60v from this... I tried also to make a high voltage with about 1000 turns primary and about 20 secondary with no success. For some reason the high voltage one become hot and it didnt give any output. Transformers was E shape ferrite core that i took from an old PC power supply.

 

[audioguru]

I explained that the original circuit has 9V of losses so if the battery is 12V then only 3V gets fed to the transformer.

 

[transforman2]

Hmm ok i will try to run the circuit with 9v battery and the transistors with the 12v battery, but the multi-meter it measures 11v output from the transistors

 

[chemelec]

I Think you have your Primary and Secondary Reversed in you mind.
This is a STEP UP Design, So the Primary is the Input Side with the 20 turns.
Secondary is the Output Side, Your 600 or 1000 turns.

 

[audioguru]

The datasheet of an ordinary 555 shows that with a load of 200mA and powered from 12V then its output is typically 7V p-p but some will be less.
Your transistors are emitter-followers with no voltage gain, they might have a loss of 2V to 3V. Then the output to the transformer is only 4V p-p to 5V p-p.
Your multimeter cannot accurately measure frequencies higher than about 400Hz and cannot measure the p-p of a squarewave.

If you power the 555 with a 9V supply and a 200mA load then its output will be nothing or 1V p-p and the output of the transistors will always be zero.

 

[transforman2]

I Think you have your Primary and Secondary Reversed in you mind.
This is a STEP UP Design, So the Primary is the Input Side with the 20 turns.
Secondary is the Output Side, Your 600 or 1000 turns.

For step up, primary have fewer turns than secondary

 

[dr pepper]

Correct.
In #3 you said 600 turns pri and 20 sec.

 

[transforman2]

Correct.
In #3 you said 600 turns pri and 20 sec.

Yes you have right, that is my mistake sorry. I meant 600 turns sec and 20 pri

Thanks