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Questions and Answers
What is the number of terminals in an SCR?
What is the number of terminals in an SCR?
What type of switches are TRIACs and DIACs considered as?
What type of switches are TRIACs and DIACs considered as?
How can a TRIAC be turned ON?
How can a TRIAC be turned ON?
What is the main difference between an SCR and a TRIAC?
What is the main difference between an SCR and a TRIAC?
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What is the process of triggering a TRIAC when biased with an external voltage more positive on 𝐴' compared to 𝐴''?
What is the process of triggering a TRIAC when biased with an external voltage more positive on 𝐴' compared to 𝐴''?
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What is the analogy between Shockley Diode and DIAC, and SCR and TRIAC?
What is the analogy between Shockley Diode and DIAC, and SCR and TRIAC?
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What is the advantage of using SBS to trigger a TRIAC over using a DIAC?
What is the advantage of using SBS to trigger a TRIAC over using a DIAC?
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What is the purpose of 𝐶# in the flash-on effect scenario?
What is the purpose of 𝐶# in the flash-on effect scenario?
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What happens to the charge of 𝐶# when the TRIAC is ON?
What happens to the charge of 𝐶# when the TRIAC is ON?
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Why does the light of the lamp become brighter during the succeeding half cycles?
Why does the light of the lamp become brighter during the succeeding half cycles?
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What is the role of the external Zener diode in the SBS characteristic curve?
What is the role of the external Zener diode in the SBS characteristic curve?
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What type of device is the SBS?
What type of device is the SBS?
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What is the condition for the effective period of V!(t) in a TRIAC Phase-Control Circuit?
What is the condition for the effective period of V!(t) in a TRIAC Phase-Control Circuit?
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What is the purpose of the gate terminal in a Silicon Bilateral Switch (SBS)?
What is the purpose of the gate terminal in a Silicon Bilateral Switch (SBS)?
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What is the typical rating for the breakover voltage (VQP) of a Silicon Bilateral Switch (SBS)?
What is the typical rating for the breakover voltage (VQP) of a Silicon Bilateral Switch (SBS)?
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What happens when the current through the anodes of a Silicon Bilateral Switch (SBS) falls below the holding current (IOP)?
What happens when the current through the anodes of a Silicon Bilateral Switch (SBS) falls below the holding current (IOP)?
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What is the characteristic of a TRIAC that allows it to conduct in both directions?
What is the characteristic of a TRIAC that allows it to conduct in both directions?
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What is the purpose of a DIAC in a TRIAC Phase-Control Circuit?
What is the purpose of a DIAC in a TRIAC Phase-Control Circuit?
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Study Notes
Silicon Bilateral Switch (SBS)
- A bilateral breakover device, similar to a DIAC
- Conducts until the current through its anodes falls below the holding current (𝐼OP)
- Gate terminal can alter breakover voltage in one direction
- Popular in low-voltage trigger circuits with a typical 𝑉QP rating of ± 8 V
SBS Characteristic Curve (Floating Gate)
- No description provided
SBS Characteristic Curve (With External Zener Diode)
- No description provided
Applications of SBS
- Can be used to trigger a TRIAC, eliminating hysteresis or flash-on effect encountered with DIACs
Flash-On Effect
- Occurs when a DIAC is used to trigger a TRIAC
- Causes the TRIAC to turn ON earlier during succeeding half cycles, resulting in a brighter lamp light
- Caused by the charge of 𝐶# taking longer to charge to a certain value in the other direction
TRIAC Phase-Control Circuit
- 𝛼 and 𝜋+𝛼 waveforms are used to analyze the circuit
- The effective period of 𝑉!& (𝑡) is 𝜋, resulting in a load RMS voltage of 𝑉!,'()
- The power delivered to the load is 𝑃!-.= 𝑅!
Sample Problems
- Sample Problem 1: Find the firing delay angle, 𝑉G,IJK, 𝑉G,LMN, 𝐼G,IJK, and power dissipated by the load
- Sample Problem 2: Find the firing delay angle, 𝑉G,IJK, 𝑉G,LMN, 𝐼G,IJK, and power dissipated by the load
Silicon Controlled Rectifier (SCR)
- A 4-layer device with three terminals: Anode, Cathode, and Gate
- Simplified structure and schematic symbol shown
SCR Characteristic Curve
- 𝐼!= 0 for various values of 𝐼!
DIAC Characteristic Curve
- No description provided
Triode for AC (TRIAC)
- Essentially a DIAC with a gate terminal
- Can be turned ON by a pulse of gate current
- Does not require breakover voltage for initial conduction
- Can conduct current in either direction, depending on main terminal voltage polarity
- Considered a "Bilateral Switch"
TRIAC Construction and Schematic Symbol
- No description provided
TRIAC Characteristic Curve
- No description provided
TRIAC Equivalent Circuit
- No description provided
Comparison: DIAC and TRIAC
- Analogy: Shockley Diode → DIAC; SCR → TRIAC
- Compared in terms of construction, schematic symbol, and characteristic curve
TRIAC Triggering
- Triggered by current from the gate to 𝐴# when biased more positive on 𝐴" than 𝐴#
- Triggered by sending gate current from 𝐴# to gate when biased more positive on 𝐴# than 𝐴"
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Description
Learn about the characteristics and applications of Silicon Bilateral Switch (SBS) including its use in triggering TRIAC, eliminating hysteresis and flash-on effect.
