Controlling Gate turn off thyristors GTO

[pns2050]

Hello,

Its been sometime now that i am trying to figure out an efficient way to turn on and off a GTO thyristor but i cannot find a solution,
i ve searched the net a lot but i couldnt find any information regarding the triggering of a GTO.

I know that it requires a positive pulse to its gate like a thyristor would do to start conducting , and a negative pulse with current of around 20-30% of its anode-cathode current to turn it off. But how would i manage to produce that from a single circuit and feed it the gate?

I tried to produce a positive pulse and a negative pulse from two different circuits and connect both outputs to gate but of course its not an efficient solution, sometimes it works , sometimes it doesnt respond correctly.

Please can you refer a book where i can learn more about this ? Or anyone who worked with GTO's before can tell me a few ideas? I want so much to make this work but i cant find a lead from where to start, the information on internet is really limited about the specific subject

Thanks in advance

 

[goldsmith]

Dear pns2050
Hi
Can you show me the schematic that you're referring to , please ? thus perhaps i can help you .
Best Wishes
Goldsmith

 

[pns2050]

Hello goldsmith,

i tried with the simple circuit below to experiment with the GTO thyristor BT-157 , to be able to see its triggering characteristics before going any further..

.

I have tried 2 ways to turn it on/off both failed..

First way

i used 2 PIC16F871 microcontrollers, one was producing a positive Voltage pulse , and the other one was producing a negative voltage pulse to turn it off theoretically.
I managed to do that my having the second PIC microcontroller having as reference voltage -5V and 0V as ''High''.
But having two different outputs connected on THYRISTORS gate was not resulting to reliable turn on/off. Sometimes it was working sometimes was not.So i figured out i had to produce the triggering pulses from a single source..

Second way



With sending inputs to Q1 and Q2 i was able to get the following pulses but it wasnt enough to trigger the thyristor currentwise. BT-157 needs more than 100mA to turn on and more than 200mA to turn off..



So my question is what is an efficient way to control a GTO thyristor. I tried some ideas i had because i cant find anywhere information how to do so..

Thank you for your reply