Lecture 2 - Scr, Gto, Diac, Triac.pptx

SILICON CONTROLLED RECTIFIER (SCR) 1

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BASIC SCR CIRCUIT

IGT & VGT

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EXAMPLE Determine the value of VIN needed to trigger the SCR?

VSCR ≈ 0.7 V

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EXAMPLE Determine the value of the supply voltage needed to turn off the SCR? VSCR ≈ 0.7 V

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GATE TURN-OFF THYRISTOR (GTO) 5

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GTOs  also known as GATE CONTROLLED SWITCH  Invented by GENERAL ELECTRIC

 a variation of an SCR  10 times faster than an SCR

 turn off: 20% of anode load current

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GTOs

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SCR APPLICATIONS

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1. HALF WAVE POWER CONTROL

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HALF WAVE POWER CONTROL

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HALF WAVE POWER CONTROL

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HALF WAVE POWER CONTROL

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EXAMPLE Show the voltage waveform across the SCR in relation to the load current for 180°, 45°, 90° conduction. Assume an ideal SCR.

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EXAMPLE

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EXAMPLE

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EXAMPLE

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EXAMPLE

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2. CROWBAR CIRCUIT

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DIAC 19

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DIAC  DIode Alternating Current  bidirectional device with no gate control

 behaves exactly like a Shockley Diode back to back

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DIAC

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DIAC

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I-V CURVE

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AC OPERATION

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TRIAC 25

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TRIAC  TRIode Alternating Current  bidirectional device

 behaves like a back-to-back SCR

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TRIAC

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TRIAC

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TRIAC

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I-V CURVE

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MODES OF OPERATION

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QUADRA C 32

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QUADRACs

 internally triggered TRIAC  save space by reducing component count 33

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