Silicon controlled rectifier

Symbol of the thristorn.

The silicon controlled rectifier (in English SCR: silicon controlled rectifier) is a type of thyristor formed by four layers of semiconductor material with PNPN or NPNP structure. The name comes from the union of Tiratron (tyratron) and Transistor.

Tiristor.

An SCR has three connections: anode, cathode, and gate. The gate is responsible for controlling the flow of current between the anode and the cathode. It basically works as a controlled rectifier diode, allowing current to flow in only one direction. As long as no voltage is applied to the gate of the SCR, conduction is not initiated and at the instant that said voltage is applied, the thyristor begins to conduct. Working in alternating current, the SCR de-energizes at each alternation or half cycle. Working in direct current, a forced blocking circuit is needed, or else interrupt the circuit.

The switching pulse must be of a considerable duration, or repetitive if working with alternating current. In the latter case, depending on whether the trigger pulse is delayed or advanced, the point (or phase) at which the current passes to the load is controlled. Once started, we can cancel the gate voltage and the thyristor will continue to conduct until the load current drops below the holding current (in practice, when the sine wave crosses zero).

When there is a sudden voltage variation between anode and cathode of a thyristor, it can trip and go into conduction even without gate current. For this reason, the maximum rate of voltage rise that allows the SCR to be kept blocked is given as a characteristic. This effect occurs due to the parasitic capacitor between the gate and the anode.

SCRs are used in power electronics applications, in the field of control, especially motor control, because it can be used as an electronic switch.

Tetrode thyristor

SCR. The white cable is the door. The fine red serves as a reference of the cathode tension.

They are thyristors with two firing electrodes: anode gate and cathode gate. The BRY39 is a tetrode thyristor.

SCR parameters

• VRDM: maximum reverse blasting of bale (VG = 0)
• VFOM: maximum direct voltage without blinding (VG = 0)
• IF: maximum direct current allowed.
• PG: maximum power dissipation between gate and cathode.
• VGT-IGT: maximum voltage or current required in the gate (G) for the
• IH: minimum anode current required to keep SCR blind
• dv/dt: maximum voltage variation without having baked.
• di/dt: maximum current variation accepted before destroying the SCR.

Thyristor

Thor

• DIAC: diode for alternating current "SEPU".
• Diodo Shockley: four-layer diode.
• Tiristor GTO Gate Turn Off: blockable thristorn by door
• PUT Programmable UJT: transistor Union Programmable
• SBS Silicon Bilateral Switch: Bilateral silicon switch
• Unilateral silicon switch Unilateral Silicon Switch: SUS
• Triac: triode for alternating current.