Applications of MOSFET

Hello friends, I hope you all are doing fine. I have already shared a detailed guide on MOSFET, where we have discussed the basics along with its construction & working. I hope you have grasped something out of it.

Today, I am going to discuss a few applications of MOSFET, to give an idea of why they are so popular. There is an endless list of applications and uses of MOSFET from a simple circuit to the complex automated processes and whatnot, we will go through some of the most widely used ones.

Street Light System Designed With MOSFET

• Previously, when there was not much advancement in technology, street light systems were essentially made using high-intensity discharge lamps HID. A major drawback associated with their working was the fact that they were not energy efficient, and secondly, they lacked the automated mechanism through which the whole system could self-regulate according to the external environment, the tiring days of humanity and technology when everything was manual! You might have seen a lot of streetlights still on during the daylight during your childhood, I'm talking about them!
• So, LEDs came to the rescue to control the intensity of the light and timings of being switched on and switched off, to make our lives lighter, brighter and easier!
• Nowadays, MOSFETs are used in the above-mentioned setting of the LED-based lighting system. A cluster of LEDs are used for the display, one MOSFET can’t do the job obviously!
• There are certain plus points to this system because of the pulse wave modulation provided by the MOSFET. Other than this, they are programmed to self-regulate and respond according to real-time situations.

• The high-intensity discharge system cannot control the intensity of light during the non-peak hours, why would you need a fully bright Street light at 4 pm or 5 pm? Or when no one is passing through the street?
• The modern and intelligent system of LEDs sense everything and respond accordingly, the light dims when there is not much illumination needed, in some places, it turns on itself when someone is passing through the street and then turns off eventually, and in the daylight, they keep themselves fully turned off.

MOSFET in Space Vector pulse width modulation system

• Space Vector pulse width modulation is used to control AC motors through the generation of a sine wave, providing a pure voltage to the ac motor with the least amount of harmonic distortion, you can read it again to absorb the fact, I know it can’t be engulfed at once!
• Previously, the Space pulse width modulation was used for controlling the AC motor but there was a huge drawback associated with this method; it tends to produce high harmonic distortion because of the switching characteristics peculiar to older pulse width modulation.

• In Space Vector, pulse width modulation single-phase AC produces a DC supply after rectification.
• Afterward, the DC supply is fed into an inverter which is three-phased having six MOSFETs.
• We have in total three phases and a pair of MOSFET is used for each of the phases.
• In order to control the speed of the motor by the production of a three-phase supply, Six MOSFETs, being in three pairs are switched on at a time during different intervals of the cycle.
• There is a light indicator as well for highlighting the faults in the control circuit.
• MOSFETs are also used in power appliances where PWM is required i.e. Inverters, Multilevel Inverters, Converters etc.

BLDC Motors and MOSFET

• Let's talk about BLDC motors first, Brushless DC motors are the new normal of the mechanical industry, as they have addressed a lot of issues industry was facing previously like higher noise, more cost for a project, wear and tear, lesser efficiency and a lot more with conventional old school motors.
• BLDC motors provide higher power to weight ratio, improved torque than conventional motors, they are lighter, they are cost-effective and above all, they have a wider dynamic response rate.
• As we have switched to the BLDC motors we need a better system to drive them too, modern problems require modern solutions! Let us ignore the other elements and talk about the involvement of MOSFETs in the process.
• MOSFETs are the switching elements of BLDC motors, the coils of DC motors are arranged in half-bridge topology and are energized through MOSFETs.
• In BLDC motors switching element is responsible for the efficiency and performance of the system, so you can yourself imagine how important the MOSFET selection for a brushless DC motor is!
• Speed control is very important for the BLDC motors, EEROM speed control of BLDC motors is also carried out by the MOSFET. It operates the DC motor at varying speeds during the duty cycles according to the embedded program fed into the microcontroller.

High voltage generation using MOSFET

• The process of generating a high voltage pulse from a low voltage pulse is carried out by Marx generator.

• To establish such a circuit, capacitors and MOSFETs are used accordingly as you can see in the diagram given above.
• A number of capacitors are connected in parallel which charges at a particular time.
• These capacitors are then connected in series during the off period for developing a higher voltage.
• The output Voltage is three times the value of the input Voltage.
• MOSFET switches are used to switch the capacitors from parallel to series mode.
• A 555 timer is used to send the clocked pulses for charging the capacitors in the series mode during the on-time.
• You can measure the altered voltage which is triple the input voltage through a multimeter.

So, that was all for today. I hope you have enjoyed today's lecture, will meet you guys in the next lecture. Take care!!!