Power Electronics

Structure of a Power MOSFET Structure of a power MOSFET : The power MOSFETS are generally enhancement type. In order to increase the voltage rating of the enhancement MOSFET, a drift layer is included as shown in Figure. The power MOSFET has the vertically oriented four layer structure of alternate p and n layers as … Read more

Power MOSFET The long form of MOSFET is Metal Oxide Semiconductor Field Effect Transistor. The new power MOSFETS have improved current carrying capacity and higher off state blocking voltage capacity and they are replacing the power transistors in many applications. Power MOSFETS are capable of switching at very high frequencies upto about 100 kHz. This … Read more

Advantages of SCR It can handle large voltages, currents and power. The voltage drop across conducting SCR is small. This will reduce the power dissipation in the SCR. Easy to turn on. Triggering circuits are simple. It can be protected with the help of a fuse. We can control the power delivered to the load. … Read more

Operation of SCR : Operation of SCR can be studied under two different operating conditions. They are as follows : SCR Operation without gate current : Refer to Figure (a) The gate terminal of SCR is left open so that IG = 0. SCR is forward biased by applying a positive voltage to anode with respect to … Read more

How to turn off SCR ? The gate current can turn on SCR but once turned on, the gate loses control. Even if we reduce the gate current to zero, SCR continues to conduct. We can turn off a conducting SCR by : Reducing its anode current below the holding current for a minimum specified … Read more

Reverse IV characteristics of SCR Figure shows that the reverse characteristics of an SCR is very similar to that of a diode. As long as the reverse anode to cathode voltage is less than the reverse breakover voltage, a small reverse anode current flows due to minority carriers. But as soon as a reverse voltage … Read more

Difference between holding and latching currents in IV characteristics of SCR Q. What is Holding Current in SCR Q. What is Latching Current in SCR The latching current is important only at the time of SCR turn on, whereas holding current is important only at the time of SCR turn off. If the anode current … Read more

I-V Characteristics (Static/Output Characteristics) Q. Define following terms of SCR and state their typical values : 1. Holding current 2. Latching current. Q. Sketch V-I characteristics of SCR and label VBO , IL and IH. Q. Draw and explain zero gate signal characteristics of SCR. Q. Draw construction of SCR and explain its operation with … Read more

Construction of SCR Q. Draw construction of SCR. Explain its operating principle using two transistor analogy. Q. Draw construction of SCR and explain its operation with V-I characteristics. Q. Describe the construction of SCR with neat sketch. Also draw SCR’s symbol. Q. Draw the symbols of SCR The basic structure of SCR is as shown … Read more

Silicon Controlled Rectifier (SCR) SCR is one of the oldest types of solid state power device. It was invented in 1957 by the General Electric Research Laboratories. SCRs have the highest power handling capacity of all the power semiconductor devices. They have a four layer construction with three user accessible terminals namely anode, cathode and … Read more