Please name the most common silicon based semiconductor devices:
- Diode
- Thyristor or silicon-controlled rectifier (SCR)
- Triac
- Gate turn-off thyristor (GTO)
- Bipolar junction transistor (BJT or BPT)
- Power MOSFET
- Static induction transistor (SIT)
- Insulated gate bipolar transistor (IGBT)
- MOS-controlled thyristor (MCT)
- Integrated gate-commutated thyristor (IGCT)
What are Power Diodes and their usage in electrical and electronics engineering?
Power diodes provide uncontrolled rectification of power and are used in applications such as electroplating, anodizing, battery charging, welding, power supplies (dc and ac), and variable-frequency drives. They are also used in feedback and the freewheeling functions of converters and snubbers.
What is the basic structure of a power diode?
A typical power diode has P-I-N structure, that is, it is a P-N junction with a near-intrinsic semiconductor layer (I-layer) in the middle to sustain reverse voltage.
What is cause of Avalanche Breakdown, how it can be avoided?
In the reverse-biased condition, a small leakage current flows due to minority carriers, which gradually increase with voltage. If the reverse voltage exceeds a threshold value, called the breakdown voltage, the device goes through avalanche breakdown, which is when reverse current becomes large and the diode is destroyed by heating due to large power dissipation in the junction.
What is a fast-recovery diode?
In a fast-recovery diode, as the name indicates, the recovery time t and the recovery charge Q are reduced by the minority carrier lifetime control that enhances the recombination process. However, the adverse effect is a higher conduction drop.
What is a Schottky diode, what are its advantages?
Schottky diode is basically a majority carrier diode and is formed by a metal-semiconductor junction. As a result, the diode has a lower conduction drop (typically 0.5 V) and faster switching time, but the limitations are a lower blocking voltage (typically up to 200 V) and higher leakage current.
What does the word “thyristor” means?
The term "thyristor" came from its gas tube equivalent, thyratron.
What devices belongs to Thyristor family?
That includes SCR, triac, GTO, MCT, and IGCT.
What is a thyristor and its construction and working?
Thyristors can be classified as standard, or slow phase-control-type and fast-switching, voltage-fed inverter-type. Basically. it is a three-junction P-N-P-N device, where P-N-P and N-P-N component transistors are connected in regenerative feedback mode. The device blocks voltage in both the forward and reverse directions (symmetric blocking). When the anode is positive, the device can be triggered into conduction by a short positive gate current pulse.
Does the gate of ordinary thyristor have ability to turn off?
Once the device is conducting, the gate loses its control to turn off the device.
In how many ways thyristor can be turned on?
Beside gate signal a thyristor can also turn on by excessive anode voltage, its rate of rise dv/dt, by a rise in junction temperature ( Ti), or by light shining on the junctions.
Please explain the turn on procedure of a thyristor using excess anode voltage?
If forward voltage is applied on the device, there will be a leakage current due to blocking of the middle junction. If the voltage exceeds a critical limit (breakover voltage), the device switches into conduction. With increasing magnitude of IG, the forward breakover voltage is reduced, and eventually , the device behaves like a diode with the entire forward blocking region removed.
What is latching current and holding current in a thyristor?
The device will turn on successfully if a minimum current, called a latching current, is maintained. During conduction, if the gate current is zero and the anode current falls below a critical limit, called the holding current, the device reverts to the forward blocking state.
What are Triacs?
A triac has a complex multiple-junction structure, but functionally, it is an integration of a pair of phase-controlled thyristors connected in inverse-parallel on the same chip. The three-terminal device can be triggered into conduction in both positive and negative half-cycles of supply voltage by applying gate trigger pulses.
What are advantages and disadvantages of Triac over traditional thyristor equivalent circuit?
A triac is more economical than a pair of thyristors in anti-parallel and its control is simpler, but its integrated construction has some disadvantages. The gate current sensitivity of a triac is poorer and the turn-off time is longer due to the minority carrier storage effect.For the same reason, the reapplied dv/dt rating is lower, thus making it difficult to use with inductive load. A well-designed RC snubber is essential for a triac circuit.
What are common applications of a Triac?
Triacs are used in light dimming, heating control, appliance-type motor drives, and solid-state relays with typically 50/60 Hz supply frequency.
