thyristor ebook


Joined Apr 5, 2008

Take a look at this quote from the ePanorama:

  • Thyristor and TRIAC

    Thyristor is a component that acts like a very special diode. At the thyristor, the timing which the forward direction electric current flows through can be controlled. The thyristor has the three terminals. They are the T2(The terminal which is equivalent to the anode), the T1(The terminal which is equivalent to the cathode) and the gate. The electric current in the forward direction doesn't flow when the electric current doesn't flow through the gate. When the trigger electric current(Pulse) flows through the gate, the forward direction electric current of the thyristor begins to flow. The forward direction electric current of the thyristor to have begun to flow through once alwayses fall through even if the electric current at the gate passes away until the forward voltage passes away. The gate function is again restored when the forward voltage passes away. So, the forward direction electric current of the thyristor doesn't flow until the trigger electric current flows through the gate even if the forward voltage is applied once again.The basic principle of using a PNPN structure to producea thyristor, and a NPNPN structure (with two PNPN.s inantiparallel) to produce a triac has been known fordecades.Some thyristor types:
    • SCR: SCR (Semiconductor Controlled Rectifier) is name for "a normal thyristor" used in many different applications
    • GTO: GTO (Gate Turn Off) is a special type of thryristor that can be turned on and off with control current on the gate. A positive current pulse turns GTO on and negative current pulse turns it off.
    • RCT: This is a combination of SCR and reverse connected diodes. This will conduct current to both directions and current flow to one direction is controllable.
    • LASCR: LASCR (Light Activated SCR) is a light controller tyristor that is used in applications where very high voltages are controlled.
    • SITh: SITh (Static Induction Thyristor) is a thyristor that work usign JFET principle
    • IGCT: IGTC (Integrated Gate Controlled Thyristor)
    • GATT, GATO: Gate-Assisted Turn-Off Thyristor is a special thyristor used in some TV deflection circuits and in radar technology
    • FCT: FCT (Field Control Thyristor) is a thyristor that work usign JFET principle
    • IGCT: IGCT (Integrated Gate Controlled Thyristor) is a thyristor type that is used in high power inverter circuits.
    • TRIAC: TRIAC is a trade name of bidirectional triode thyristor. TRIAC is a component that is like two thyristors in one case on different directions. It can control the current flow in both directions with the control pulse turing it on until the next current zero crossing.
    The bidirectional triode thyristor (TRIAC) is the thyristor which can be used in the alternating current. It is possible to work the gate function in each of the alternating current sides of the positive voltage, the sides of the negative voltage. Because it is, the electric power of the alternating current can be controlled.DIAC is a trigger diode that has the special characteristic. At the trigger diode, the electric current flows through bidirectionaly. When the voltage across the DIAC is less that the DIAC norminal voltage, no current flows. When the voltage which is applied to the DIAC crosses the DIAC nominal voltage, the diode becomes the ON condition and the voltage of the both edges of the diode falls rapidly. This characteristic matches well to control the gate of the bidirectional triode thyristor, and this is the main application for DIACs.
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