Lecture-6 : Semiconductor Power Switching Devices-3

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This is Lecture-6 on Power Electronics. In this lecture we discuss triacs, diacs, and GTOs.

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Lecture-6 : Semiconductor Power Switching Devices-3

  1. 1. Semiconductor Power Switching Devices-3 (Lecture-6) R S Ananda Murthy Associate Professor and Head Department of Electrical & Electronics Engineering, Sri Jayachamarajendra College of Engineering, Mysore 570 006 R S Ananda Murthy Semiconductor Power Switching Devices-3
  2. 2. TRIAC MT2 MT1 G Circuit Symbol of TRIAC J1 J2 J3 Structure of TRIAC + indicates heavily doped region - indicates lightly doped region MT1 MT2 G J4 ON OFF ON OFF MT2 positive w.r.t. MT1 and G positive w.r.t. MT1 Pulse triggered MT2 negative w.r.t. MT1 and G negative w.r.t. MT1 Pulse triggered MT1 MT2 G TRIAC is equivalent to two SCRs in anti-parallel Shorting of p1 region to n3 region due to MT2 metal contact, and the p2 region to the n2 region due to MT1 metal contact results in two anti-parallel SCR structures: p1n1p2n2 and p2n1p1n3. R S Ananda Murthy Semiconductor Power Switching Devices-3
  3. 3. TRIAC used in ACVC VRMS Constant f AC ACVCV, AC Variable same as inputf (a) vi vo (b) Triac+ − R + − vi vo tω tω (c) 0 Trigger 0 Trigger Trigger π 2π π 2π R S Ananda Murthy Semiconductor Power Switching Devices-3
  4. 4. Limitations of TRIAC as Compared to SCRs Has lower dv/dt rating. Requires well designed R-C snubber connected across it to limit dv/dt. Has longer turn-off time. Has lower power handling capability. Typically used in small motor speed regulators, temperature control, illumination control, liquid level control, phase control circuits, power switches. Cannot be used in A.C. systems of frequency more than 400 Hz. R S Ananda Murthy Semiconductor Power Switching Devices-3
  5. 5. Specifications of TRIAC BT139 R S Ananda Murthy Semiconductor Power Switching Devices-3
  6. 6. Specifications of TRIAC BT139 R S Ananda Murthy Semiconductor Power Switching Devices-3
  7. 7. Specifications of TRIAC BT139 R S Ananda Murthy Semiconductor Power Switching Devices-3
  8. 8. Diac MT1 MT2 P N P J1 J2 MT1 MT2 MT1 MT2 Structure and symbols of diac Diacs are typically used to trigger TRIACS in ceiling fan regulators and light dimming circuits. R S Ananda Murthy Semiconductor Power Switching Devices-3
  9. 9. Typical Diac Specifications R S Ananda Murthy Semiconductor Power Switching Devices-3
  10. 10. Typical Diac Specifications R S Ananda Murthy Semiconductor Power Switching Devices-3
  11. 11. Typical Diac Specifications R S Ananda Murthy Semiconductor Power Switching Devices-3
  12. 12. Simple Fan Regulator Circuit using TRIAC Diac DB2 is used to trigger TRIAC BT136. R S Ananda Murthy Semiconductor Power Switching Devices-3
  13. 13. Some High Power TRIACS (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  14. 14. Ratings of Some High Power TRIACS (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  15. 15. Gate Turn Off Thyristor (GTO) A K G J1 J2 J3 Buffer layer A K G Anode contact Buffer layer structure Anode shorted structure Anode short A A K K GG Circuit symbols of GTO Increases reverse voltage blocking capability Decreases reverse voltage blocking capability A K G Inter digitized gate-cathode structure increases di/dt rating of the device and also improves turn-off performace of the device. R S Ananda Murthy Semiconductor Power Switching Devices-3
  16. 16. Static Characteristic of GTO A K G Circuit Symbol of GTO ON OFF = Latching Current = Holding Current Forward Leakage Current Symmetrical GTO Asymmetrical GTO R S Ananda Murthy Semiconductor Power Switching Devices-3
  17. 17. Control Characteristics of GTO vo iG vo + − iG t V t + − GTO RV GTO can be turned on by applying a positive gate current pulse and turned off by applying a negative gate current pulse. To prevent unwanted turn-off during transients, it is recommended to apply a low value of continuous positive gate current as long as GTO has to be kept on. R S Ananda Murthy Semiconductor Power Switching Devices-3
  18. 18. GTO Compared with SCR GTO SCR Fully-controlled Semi-controlled VON = 3-4 V VON =1.5-2 V Higher IL and IH IL and IH very low compared to GTO Assymetric GTO has very low VBR Has VBR ≈ VBO Typically dv/dt = 1000 V/µs Typically dv/dt =200-500 V/µs Turn-off Current Gain: 6-15 Not applicable Max. operating frequency: 1-4 kHz Typcally operated at 50 or 60 Hz R S Ananda Murthy Semiconductor Power Switching Devices-3
  19. 19. Photographs of GTOs Asymmetric Type Reverse Blocking Type (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  20. 20. Stud Type GTO (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  21. 21. Specifications of Asymmetric GTOs (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  22. 22. Specifications of Symmetric GTOs (Source: www.china-rectifier.com) R S Ananda Murthy Semiconductor Power Switching Devices-3
  23. 23. Next Lecture... In the next lecture we will discuss some more power semiconductor switching devices used in power electronics. Thank You. R S Ananda Murthy Semiconductor Power Switching Devices-3

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