thyristor firing circuit

[TronicBrain]

Hi all

I need simple Digital firing pulse generator for thyristor power converters circuit

any one have one?

I want to make a small thyristor power converter.

thanks

 

[Aily Sajjad]

Hi,

Do you mean digital circuits to control firing pulse timing/frequency?

If you are familiiar with UJTs, the UJT relaxation oscillator can do the job. A monostable vibrator (transistoirsed or 555 based) with very short time costant can also serve your purpose.

some years ago, i made a similar circuit but that was micro-controller based with up / down switches to control the firing frequency.

Aily

 

[TronicBrain]

Yes
About the UJTs
I'm familirar with them
But the circuit should be for three phase system (120 degree three between pulses) so how to make this phase shift to three UJT relaxation oscillators out put?

 

[em2006]

To make a simple thyristor converter of a three phase, working on a resistive load, you can use 2 simple ways for synchronization of your three UJT oscillators with the line voltage:
1-using three small monophasic transformers
2-using a single small threephasic transformer
You also can use dedicated ICs: UAA145, TCA785, etc, instead of UJT oscillators.