15-kV 100-A single-bias all-optical SiC emitter turn-off thyristor

A new design of a very high-voltage, single-bias, and optically-controlled emitter turn-Off thyristor (ETO) is introduced. Both the thyristor and the controlling switch are triggered optically using two lasers. In the outlined structure, only a single power bias of 15 kV is required. The low-voltage control bias, typically used for triggering devices in an electrical ETO thyristor [1, 2], is eliminated due to all-optical control. This eliminates the problem of susceptibility to electromagnetic interference (EMI) and yields complete electrical isolation between the power and the control stages. It is found that this new optically-triggered ETO is capable of switching the thyristor to the conducting mode in less than 65 ns for a rated current of 100 A. In order to use high current levels, a Darlington structure is used in our silicon controlling switch which is called optically triggered power transistor (OTPT). The first stage of the Darlington OTPT is triggered with a 5 W laser of 808 nm wavelength and the current is then amplified through the second electrical stage of the Darlington OTPT. The main silicon carbide (4-HSiC) SGTO thyristor is triggered with a low wavelength laser of 266 nm. The current fall time is found to be 393 ns and the total on-state voltage drop across the ETO is 5.4 V at 100 A current. This is about 0.04 % of the total applied voltage. The designed optical switch is able to conduct the rated current of 100 A at a low on-state voltage of 0.8 V under a laser power of 5 W.