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A silicon-controlled switch (SCS) behaves nearly the same way as an SCR; but there are a few differences. Unlike an SCR, an SCS switches off when a positive voltage/input current is applied to another anode gate lead. Unlike an SCR, an SCS can be triggered into conduction when a negative voltage/output current is applied to that same lead.
They have two MOSFETs of opposite conductivity types in their equivalent circuits. One is responsible for turn-on and the other for turn-off. A thyristor with only one MOSFET in its equivalent circuit, which can only be turned on (like normal SCRs), is called an MOS-gated thyristor. Schematic of a MOSFET-controlled thyristor
The device turns off when the anode voltage falls below a value (relative to the cathode) determined by the device characteristics. When off, it is considered a reverse voltage blocking device. [19] Gate turn-off thyristor (GTO) The gate turn-off thyristor, unlike an SCR, can be turned on and off with a gate pulse.
Here, it becomes important for the supply to pulse on and off at the correct position in the modulation cycle for a known value to be achieved; for example, the controller could turn on at the peak of a waveform or at its base if the cycle's time base were not taken into consideration.
The first-generation IGBTs of the 1980s and early 1990s were prone to failure through effects such as latchup (in which the device will not turn off as long as current is flowing) and secondary breakdown (in which a localized hotspot in the device goes into thermal runaway and burns the device out at high currents). Second-generation devices ...
It is related to the gate turn-off (GTO) thyristor. It was jointly developed by Mitsubishi and ABB. [1] Like the GTO thyristor, the IGCT is a fully controllable power switch, meaning that it can be turned both on and off by its control terminal (the gate). Gate drive electronics are integrated with the thyristor device. [2]
This current is indicated in Figure 3 by a dotted red line and is the reason why a TRIAC needs more gate current to turn on than a comparably rated SCR. [3] Generally, this quadrant is the most sensitive of the four. This is because it is the only quadrant where gate current is injected directly into the base of one of the main device ...
Since the plate turn-on voltage is much higher than the turn-off voltage, the tube exhibits hysteresis and, with a capacitor across it, it can function as a sawtooth oscillator. The voltage on the grid controls the breakdown voltage and thus the period of oscillation.