what are photothyristors ? And, in what applications they are used ? thanks

what are photothyristors ? And, in what applications they are used ?

thanks

As the name suggest. These devices are thyristors, but activated with light rather than electrical signals. Being a thyristor, once they are 'fired' they conduct until current drops below a threshold given for particular device or the voltage across anode and cathode is removed. Instead of being activated with electrical signal connected to gate, they are triggered with ligh pulse. Photothyristors can as either thyristor iwth a window in the enclosure for external light source, or integrated photothyristor with light source (similiar to phototransistors and optotriacs)

These comnponents are used mainly as safety devices ("crowbar protection circuit" for example) or in some high voltage control circuits, where thyristor action is required as well as galvanic isolation.

Hi,
Photothyristor is THYRISTOR which is activated with Light. Earlier they were being used in the Optocouplers but now their use is increasing in other circuits also. This device is now known as LASCR ( Light Activated SCR). Attached is a sketch of the same:

Ideal application os a photoMOS relay as well as static control switch.
When you need to control AC mains voltages with microprocessors giving 5VDC logic controls .

The term photothyristor mainly refers to photocouplers with thyristor output like Toshiba TLP541. Photo triacs are the more common device in this range of applications.

On the other hand, we have LTT (light triggered thyristor), a power electronics device that's commonly used in HVDC systems. Rating of individual LTTs is up to 8 kV / 4 kA **broken link removed**

Some of these used to be called LASCRs (light activated SCR).