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CD 4047 inverter

duke37

Jan 9, 2011
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What frequency did you use? If the frequency is too low, the transformer will saturate and give a low output.
The transformer is vey small and the output will drop significantly when a load is applied.
 

Alec_t

Jul 7, 2015
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The lowest oscillation frequency your circuit will produce, according to a Spice simulation, is about 90Hz. There will be some shoot-through, so the FETs are likely to overheat. I think that poor little 3VA transformer will probably saturate, as duke says.
 

duke37

Jan 9, 2011
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The link shows that there was considerable problems, did it ever work?

A capacitor discharge ignition needs about 300V on the primary to get 6kV on the secondary. Considerable power will be needed depending on the spark rate.

You could get a 6-0-6V 3A transformer running at 200Hz and voltage double the output if necessary.
An alternative is to wind your own transformer to suit. I have made one with a TV line output transformer core with one turn per volt, running at about 10kHz to generate 400V for a transmitter.
 

duke37

Jan 9, 2011
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When I was in hospital, I was 'tidied up' and I do not know where things are.
The ferrite TV transformer core is square shaped and the windings are put on one side. The advantage of this transformer is that it has an air gap made with a thin sheet of paper or plastic. As a result it can easily be dismantled. It should be re-assembled without the gap since the circuit is push-pull.

What resistor do you mean? There are timing resistors connected to the 555.
A 39pF timing capacitor will give a very high frequency which would not suit a transformer with iron laminations.
 

Oldsnake00

Apr 15, 2015
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When I was in hospital, I was 'tidied up' and I do not know where things are.
The ferrite TV transformer core is square shaped and the windings are put on one side. The advantage of this transformer is that it has an air gap made with a thin sheet of paper or plastic. As a result it can easily be dismantled. It should be re-assembled without the gap since the circuit is push-pull.

What resistor do you mean? There are timing resistors connected to the 555.
A 39pF timing capacitor will give a very high frequency which would not suit a transformer with iron laminations.
Thanks.
Now I get transformers from pc power supply.it same EE25 ferrite core.
Please Describe the transformer windings.
 

duke37

Jan 9, 2011
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I am not familiar with the EE25 ferrite core. My attempt at taking cores apart have mostly failed due to the glue being so strong and the core breaks.

The primary needs to be wound in a bifilar way. Use two wires wound side by side to make this. The wire must be thick enough to keep the temperature low. The number of turns/volt will be dictated by the frequency and some experiment will be needed to make sure that the core is not saturated.
 
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