Discrete Thyristor
When used in rectifier circuits, thyristors allow current to be controlled more accurately than diodes, which can only be ON or OFF. A thyristor can be triggered to allow current to pass in a graduated manner, by firing (switching on the thyristor) at a precise time, therefore controlling the conduction angle.
Brands
Semikron
Sirectifier
Starpower
Infineon
Vishay.