Q1 Thyristors-for-students.pdf - THYRISTORS Engr Mary Charlemaine Abas MECE Typical Packaging of THYRISTORS Intended Learning Outcome \u2022 Analyze the

Q1 Thyristors-for-students.pdf - THYRISTORS Engr Mary...

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Engr. Mary Charlemaine Abas, MECE THYRISTORS
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Typical Packaging of THYRISTORS
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Intended Learning Outcome Analyze the characteristics, operations, and circuit implementations of Thyristors. Specifically the following: o Shockley Diode o SCR o SCS o DIAC o TRIAC o UJT o PUT o Other solid-state devices used as Triggers o Phase Control o Other Control applications
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What is THYRISTOR?
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What is THYRISTOR?
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Applications of Thyristor Light dimmers Power-switching circuit Relays Logic circuits Heaters Welders Battery chargers DC and AC motor speed controls Voltage regulators
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SHOCKLEY DIODE Constructed of 4 pnpn semiconductor layer.
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SHOCKLEY DIODE Basic Construction Equivalent Circuit Symbol
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Basic Operation of SHOCKLEY DIODE FB: open switch at Forward Blocking region ( very high forward Resistance) = OFF state where V AK = 0 V up to a value of FORWARD-BREAKOVER VOLTAGE V BR(F).
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Basic Operation of SHOCKLEY DIODE FB: As I A = I S, V AK = V BR(F) . V AK drops and diode enters to Forward Conduction region closed switch or ON state as long as I A > I H .
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SHOCKLEY DIODE HOLDING CURRENT (I H ) Minimum forward current required to maintain conduction. SWITCHING CURRENT (I S ) Value of the anode current at the point where the device switches from forward-blocking (OFF) to forward-conduction region (ON). Always less than the I H.
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SHOCKLEY DIODE Once I A drops below I H until I S , the device is driven back into cutoff. When V AK reaches forward breakover voltage: The device current I A rapidly increase as the device is driven into saturation. Breakover-refers to the way a thyristor breaks down and then immediately goes into saturation. (increasing VCC breaks down either Q1 or Q2 and drives both transistors into saturation.
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A certain diode is biased in the forward-blocking region with an anode-to-cathode voltage of 20V. Under this bias condition, the anode current is 1μA. Determine the resistance of the diode in the forward-blocking region.
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Determine the value of anode current when the device is on. VBR(F) = 10V. Assume the forward voltage drop is 0.9V.
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