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How to fire up thyristors in this schematic?

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branek

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Hello,

please help me to find the best way to fire up SCR in this circuit, but without pulse transformer. Optoisolators can be used. Signal to turn on SCR will be from MCU.

Resistors represents internal resistance of generator and transformer.

thanx in advance
 

branek said:
Hello,

please help me to find the best way to fire up SCR in this circuit, but without pulse transformer. Optoisolators can be used. Signal to turn on SCR will be from MCU.

Resistors represents internal resistance of generator and transformer.

thanx in advance
Click to expand...
You can use the same type of circuit drive of a "dimmer". Basicaly is a resistor, capacitor and diac or diode to trigger the SCR.

Bastos
 

Probably the best way of triggering SCRs in circuits like this is through small pulse transformers.
See pictures below ..
Regards,
IanP
 

Hi IanP,
Can you suggest some schematics to work with pulse transformer, for firing thyristors of course.
Best regards.
Kieennx.
 

There are several ways of driving pulse transformers ..
Attached is an example of a driver build with some CMOS gates ..
Regards,
IanP
 

this is not a simple problem
 

What is the voltage value of seconder of transformer?
 

Thanx everyone for respond...

Voltage on secondary side of transformer is 60V with tap on center (2x30V).

I know that I could use pulse trasformer, but any other sugestion?!?

Circuit should be a rectifier with phase drive, because after this circuit is linear regulator, and I must minimize heat loses on power transistor.

thanx again
 

You can always use an optocoupler (see attached drawing), but for this application you have to select one with Vceo>60V ..
Here are some examples (4pin DIP): TLP521, TLP621, CNY17, ILD615 ..
Regards,
IanP
 

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    branek

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Voltage on secondary side of transformer is 60V with tap on center (2x30V).
Click to expand...
Pulse transformers used in firing thyristors is usually 1:1 turn ratio. Is it necessary to use high voltage (60V) to trigger thyristor? I use +24VDC on primary and it works well. You just need a power of only about 2.5-3V@300mA at G-K to do the job.
Best regards,
Kieennx.
 

I will try solution from IanP with optoisolator, a one solution with opto triac!

I will post results here.

bye
 

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