1. Thyristor Structure, Specifications, and Applications
By Miles Pearson
04/17/15
Abstract
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.

2. 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

3. 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”

4. Ultra-High Power Thyristor
Quantitatively understand the upper bound these devices can achieve

5. Main types of thyristors
TRIAC
SCR (Silicon Controlled rectifier)
TRIAC
GTO (Gate Turn Off)
IGTO (Integrated Gate Turn Off)
MCT (MOS-controlled Rectifier)
MCT

6. Equivalent circuits

7. How the SCR operates Three modes of operation: Reverse Blocking mode
Forward Blocking mode
Forward Active conducting mode

8. How the TRIAC Operates Modes of operation:
Forward conducting mode
Reverse conducting mode
Forward Blocking mode
Reverse Blocking mode

9. Construction of the SCR

10. 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
Largest amount of current/voltage that can be applied to gate while in conduction mode
IH – Holding Current
Minimum current flow (from anode to cathode) to keep device on
IL – Latching Current
Current flow applied to anode in order to turn the device on

11. More parameters… tgt – Gate Turn-On Time tq – Turn-Off Time
Time it takes for a gate pulse to send the SCR into conducting mode or when when the voltage drops giving it negative resistance
tq – Turn-Off Time
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
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

12. 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
I2t – Circuit Fusing Consideration
Max non-repetitive over-current capability without damage (typically rated for 60hz)
Tj – Junction Temperature
Temperature range which this device may operate without damage under load conditions

13. http://forum. allaboutcircuits

14. Characteristics of the SCR N- Regions
SCR’s have a high resistive N-base region which forms a junction J2 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 1um to 100um depending on the voltage ratings
Thicker N-base region increases forward conducting voltage drop
The Cathode region is only 2um-5 um thick and has ND range of 1016 to cm-3

15. Changing D1 and Newly added N-well
Only D1 changing

16. 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

17. 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 um thick

18. Comparing Doping Concentrations
Highest Doping Concentration:
Cathode region or n+
Next Highest level of Concentration:
Anode and Gate or p
Lowest Doping level:
Mid N-Base region or n-
However, note that this is the thickest

19. Typical Materials Used In SCR
Si - Silicon
SiC – Silicon Carbonite
GaN – 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

20. Trade-Offs In Design Forward Blocking Voltage vs. Switching time
Forward Blocking Voltage vs. Forward Voltage Drop during Conduction Mode

21. Applications of Thyristors
Rectifiers
Phase Fired Controllers
Light Dimmers
Motor Drive Speed Controllers
Strobe Lights

22. Three phase power AC to DC

23. Stun Gun Used in Power Project
Pulse rate of about 30-50hz when triggered

24. 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

25. Sources Academic Sources:
Greenburg, R., "Consumer applications of power semiconductors," Proceedings of the IEEE , vol.55, no.8, pp.1426,1434, Aug doi: /PROC
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 doi: /LED
Web Content:
ristors_application_note.pdf.pdf

26. Concept Check
Describe the 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?