thyristor reset

[2SK1058]

Hi

I am looking for a circuit, on how to auto reset the thyristor after triggering it.

I couldnt find any ideas on the google!

any help?

 

[JonSnell Electronic]

Use a transistor to remove the bias. In other words, remove the load by switching a transistor across the junctions.

 

[sofaspud]

You'll need to provide more details or show the circuit.
"Thyristor" can be a general name for a class of semiconductor devices. Which are you using... SCR? Triac?
If SCR, you'll need to reduce the current through it to a level below the holding current. That could done with a transistor switch to short the SCR as suggested in the previous post.

 

[DF96]

Thyristors have an 'on' button. They don't have an 'off' button. Maybe you need a Gate Turn-Off thyristor (but they tend to be big)?

 

[AndrewT]

Do Thyristor automatically switch off, if the AC passes through the zero crossing AFTER the trigger has been removed?

i.e. Thyristor remains triggered as long as the trigger signal is present
and
after removing the trigger signal the Thyristor needs to have the passing current reduced to near zero to allow it to turn off.

 

[JonSnell Electronic]

GTOs were widely used by Sony ih the early trinitron colour TVs. They were expensive!
Remove the DC across the thyristor with a switching transistor. That is what I did for amusement machines running on 110v DC generators many years ago. I would use a switching power MosFet now.

 

[Ketje]

Hi

I am looking for a circuit, on how to auto reset the thyristor after triggering it.

I couldnt find any ideas on the google!

any help?

😉 Mona

 

[2SK1058]

Hello

Thanks for replaying.

Check attached schematic of the circuit.

Its very simple, once the over current reaches the specified thershold, it will trigger the thyristor, so the SMPS will shut down, the only way to bring it back online, is to disconnect it from the mains supply for a few seconds.

There, I need a circuit or modification so I can make it AUTO recover after 3 seconds for example. without disconnecting it from the mains supply.

Regards

 

[DF96]

Two options:
1. don't use a thyristor if you don't want thyristor-type operation
2. arrange for the latch current to reduce below the thyristor holding current

 

[Mooly]

Do Thyristor automatically switch off, if the AC passes through the zero crossing AFTER the trigger has been removed?

i.e. Thyristor remains triggered as long as the trigger signal is present
and
after removing the trigger signal the Thyristor needs to have the passing current reduced to near zero to allow it to turn off.

Yes. Once, the trigger is removed and the main A to K current drops below the specified minimum hold current for the device, it will drop out of conduction.

 

[Ketje]

Hello

Thanks for replaying.

Check attached schematic of the circuit.

Its very simple, once the over current reaches the specified thershold, it will trigger the thyristor, so the SMPS will shut down, the only way to bring it back online, is to disconnect it from the mains supply for a few seconds.

There, I need a circuit or modification so I can make it AUTO recover after 3 seconds for example. without disconnecting it from the mains supply.

Regards

Probably some errors in your drawing ?
And and idea how to solve the restart problem.No values given, depents on the rest of the circuit and properties.
Mona

 

[2SK1058]

In your modified circuits above, D21 will feed +12V directly to the SMPS controller, and the SMPS controller will remain in the SHUTDOWN mode. So i think your drawing now is incorrect also!

 

[Ketje]

Normaly the shutdown is active when pulled to ground.With shutdown on the + that starts the supply.
Also to ignite the thyristor it needs a positive pulse on it's gate in respect to the cathode.But with the cathode floating somewhere ?? And an chemical between gate and cathode a pulse will pull the cathode up too.
Mona