Thyristor Structure Specifications and Applications By Miles Pearson
Thyristor Structure, Specifications, and Applications By Miles Pearson Abstract 04/17/15 This presentation will cover the structure, specifications and applications of several different type of thyristors. This will lead into the explanation of all the different modes and regions affiliated with these curves. We will examine the characteristics by taking a look at the I-V curves and construction of mainly the SCR (Silicon Controlled Rectifier). The exploration of certain parameters that limit this device will also be important. Finally, were going to take a look at some specific applications of thyristors and why they are used.
Overview Expose the main types of thyristors Different modes of operation Important parameters of the SCR Show construction and characteristics of SCR and TRIAC Applications of thyristors
Background On Thyristors They name Thyristor comes from two similar device names ‘Thyratron’ and ‘Transistor’ Thyristors are useful due to their ability to handle large current in power applications and fast switching The most common thyristor is the SCR which stands for “Silicon Controlled Rectifier”
Ultra-High Power Thyristor Quantitatively understand the upper bound these devices can achieve http: //www. datasheetarchive. com/dl/Datasheet-020/DSA 00357098. pdf
Main types of thyristors TRIAC SCR (Silicon Controlled rectifier) GTO (Gate Turn Off) TRIAC IGTO (Integrated Gate Turn Off) MCT (MOS-controlled Rectifier) MCT
Equivalent circuits http: //www. allaboutcircuits. com/vol_3/chpt_7/ 6. html
How the SCR operates Three modes of operation: Reverse Blocking mode Forward Active conducting mode http: //upload. wikimedia. org/wikipedia/commons/thumb/f /f 1/Thyristor_I-V_diagram. svg/1280 px-Thyristor_IV_diagram. svg. png
How the TRIAC Operates Modes of operation: Forward conducting mode Reverse conducting mode Forward Blocking mode Reverse Blocking mode http: //www. onsemi. com/pub_link/Colla teral/HBD 855 -D. PDF
Construction of the SCR N N http: //www. littelfuse. com/~/media/electronics/application_notes/switching_thyristors/lit telfuse_thyristor_fundamental_characteristics_of_thyristors_application_note. pdf
Some Important Parameters di/dt dv/dt – Critical Rise of On-State Current/voltage Maximum rise of current/voltage that the device can handle Things to consider: High frequencies and large amounts of current/voltage Igm Vgm – Forward Peak Gate Current/Voltage IH – Holding Current Largest amount of current/voltage that can be applied to gate while in conduction mode Minimum current flow (from anode to cathode) to keep device on IL – Latching Current flow applied to anode in order to turn the device on
More parameters… tgt – Gate Turn-On Time tq – Turn-Off Time it takes for SCR to start blocking current after external voltage has switched to negative cycle VDRM Ileakage – Peak Repetitive Off-State Forward Voltage/current Time it takes for a gate pulse to send the SCR into conducting mode or when the voltage drops giving it negative resistance Maximum repetitive voltage/current applied to Anode that wont breakdown the SCR or damage it VRRM IRRM – Peak Repetitive Off-State Reverse Voltage/Current Maximum repetitive voltage/current applied to Cathode that wont breakdown the SCR or damage it
Even More Parameters IGT VGT – Gate Trigger Current/Voltage Minimum value of current/voltage that will trigger the device from off to on Important for considering false triggering I 2 t – Circuit Fusing Consideration Max non-repetitive over-current capability without damage (typically rated for 60 hz) Tj – Junction Temperature range which this device may operate without damage under load conditions
http: //forum. allaboutcircuits. com/attachments/scr-voltage-current-characteristics-jpg. 69922/
Characteristics of the SCR N- Regions SCR’s have a high resistive N-base region which forms a junction J 2 as shown This region is typically doped with Phosphorus atoms where ND has a range of values from 1013 to 1014 cm-3 This regions thickness generally ranges from 1 um to 100 um depending on the voltage ratings Thicker N-base region increases forward conducting voltage drop The Cathode region is only 2 um-5 um thick and has ND range of 1016 to 1018 cm-3
Only D 1 changing Changing D 1 and Newly added N-well
Current Density Map • More heat dissipation in the thicker N-base region • Addition of the N -well seems to spread the charge carriers more unformly
Characteristics of the SCR P-Regions High voltage SCRs are generally made by diffusing Al or Ga making it a P-region Typical NA values range from 1015 to 1017 cm-3 These P-regions are generally on the order of 10 -50 um thick
Comparing Doping Concentrations Highest Doping Concentration: Next Highest level of Concentration: Cathode region or n+ Anode and Gate or p Lowest Doping level: Mid N-Base region or n- However, note that this is the thickest http: //www. radio-electronics. com/info/data/semicond/thyristor/structurefabrication. php
Typical Materials Used In SCR Si - Silicon Si. C – Silicon Carbonite Ga. N – Gallium Nitride C – Carbon P – Phosphorus Al – Aluminum Au – Gold Pl - Platinum • Used to create charge carrier recombination sites • This slows the switching time but increases forward conducting voltage drop
Trade-Offs In Design Forward Blocking Voltage vs. Switching time Forward Blocking Voltage vs. Forward Voltage Drop during Conduction Mode
Applications of Thyristors Rectifiers Phase Fired Controllers Light Dimmers Motor Drive Speed Controllers Strobe Lights http: //www. renesas. eu/products/discrete/thyristor_triac/ind ex. jsp
Three phase power AC to DC http: //www. allaboutcircuits. com/vol_3/chpt_7/5. html
Stun Gun Used in Power Project Pulse rate of about 30 -50 hz when triggered
Conclusion The main types of thyristors specified are the SCR, TRIAC, GTO, and MCT Operation modes for SCR include: Forward Active Conduction, Reverse Blocking, and Forward Blocking Characteristics of the SCR are dependent on large current and voltage Manufacturers strive for a good trade off between forward conducting voltage drop and switching time Applications are mainly centered around control of high current flow
Sources Academic Sources: Greenburg, R. , "Consumer applications of power semiconductors, " Proceedings of the IEEE , vol. 55, no. 8, pp. 1426, 1434, Aug. 1967 doi: 10. 1109/PROC. 1967. 5846 http: //ieeexplore. ieee. org/stamp. jsp? tp=&arnumber=1447776 Shurong Dong; Jian Wu; Meng Miao; Jie Zeng; Yan Han; Liou, J. J. , "High-Holding-Voltage Silicon-Controlled Rectifier for ESD Applications, " Electron Device Letters, IEEE , vol. 33, no. 10, pp. 1345, 1347, Oct. 2012 doi: 10. 1109/LED. 2012. 2208934 http: //ieeexplore. ieee. org/xpls/icp. jsp? arnumber=6286984 Web Content: http: //www. onsemi. com/pub_link/Collateral/HBD 855 -D. PDF http: //electrical 4 u. com/thyristor-silicon-controlled-rectifier http: //www. radio-electronics. com/info/data/semicond/thyristor/structure-fabrication. php http: //www. littelfuse. com/~/media/electronics/application_notes/switching_thyristors/littelfuse_thyristor_fundamental_characteristics_of_thyr istors_application_note. pdf http: //www. allaboutcircuits. com/vol_3/chpt_7/6. html http: //www. learnabout-electronics. org/diodes_07. php
Concept Check Describe three modes of operation for SCR and where they relate to the I-V curve Are you able to distinguish between the main types of thyristors specified? What are the significant trade offs in design? What is the difference between latching and holding current? If you change the N-Base region thickness of an SCR how will the resulting forward conducting voltage drop change?
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