Little improvement to the latest schematic: don't connect the two emitters together. Keep them separated and connect each one with two different Rg to the mosfet gate. In this way, you naturally protect BJTs from shoot trought and you get different values of Rg for turn-on and turn-off of the mosfet.
@mudasirnazir This is the reason they fail so much, the gate voltage is not hard on or hard off and that generates excessive heat and ultimately the destruction of the mosfet. The last diagram has a much higher more expensive parts count than the more commonly used in cheap inverters, which is a variation of the diagram with the diode across Rg. So if you updated the inverter gate drive to a variation of the last circuit your failure rate would go down considerably.
ShOcK & AWE. That was the most jam packed teaching moment I've seen yet. I'll need to rewind and re-watch a few times to get the benefits (a bit advanced for me :). Thanks for a GR8T "teaching segment". This is all going on my resume! Cheers from So.Ca.USA 3rd House On the Left (pls call before stopping by)
Thank you, but there is an issue with placing a transistor in the path to the gate of the MOSFET. I chose a MOSFET in my circuit, because of the fast switching speed in comparison with a transistor, which would be slowed down by the transistor controlling the gate or am I missing something here?
Thank you for your attention. You are absolutely right. Gate Drive is the best solution for all MOSFETs. It has high speed. In addition, it is isolated. It also works correctly with respect to the return of the voltage from the gate side. The advantages of gate drive are many.❤
Thanks for explaining, i got a degree in electrical engineering but, this stuff was never explained very well. I want to control some brushless motors with an Arduino.
Hello, thank you for your comment. I know these topics to some extent. I can present, but because my channel is very small, I try to start with simpler topics to gradually reach advanced topics. Thank you again for taking the time to watch the video
Mosfet is better than Bipolar in that it consume less current and give less switching time. If ones use Bipolar to drive the Mosfet, was it better using direct bipolar transistor instead?
Hello, your opinion is absolutely correct. In some circuits, it is necessary to use BJT, but in general, MOSFET is always better, provided that they are turned off and on correctly.
I saw at some high amper DC motor driver circuit they put 555 timer ic (non inverting buffer mode) between microcontroller and array of MOSFETs gates . They put small resistor and fast diode to fast turn off MOSFETs . This circuit work fine with motor but when I re make my self the 555 is hot and microcontroller rest. Please advice .
hello Pay attention to a few points. What is your MOSFET? What is the value of RDS on? What is gate-source resistance and gate-diode type? Does the consumer need high current? These factors play an important role in circuit efficiency
Hello, often this resistance is necessary to turn off the MOSFET. Of course, according to the type of load and MOSFET used in the circuit, as well as the value of RDSon and RG resistance, we can put corresponding values in the gate-source.
There´s a point that I can never understand: Let´s suppose, in the latest schematic, the 3 power-sources are of different voltage to each other... Are their 3 grounds connected to each other, or are each of the 3 different grounds, just the negative leads of the respective power-source...??? Thanks á priori for any answers, I´m a beginner, and although I quickly understand what´s being told (in this, excellent, or even in other tutorials), I have problems and doubts about topics, that are never discussed (like the "common ground"-topic)...
hello In every electronic circuit, we must be able to use different voltages and signals. For example, in a satellite receiver, several voltages are prepared for different parts of the circuit, such as 1.2, 1.7, 3.3 and... In all these materials, the ground is common, but the voltages are different. It is not mandatory that all are supplied from the same power source, but according to the type of circuit, they must have a common ground. However, in a series of other devices we have two or more separate grands. So, the voltages of each section must be connected to their ground separately. As an example, we can point to switching power supplies that have a cold ground and a hot ground, and there is no direct connection between them.
@@Electronic4U-david As said, I understand some things, even if the fundamentals are missing (things like common-ground-or-not-fundamentals...)... But then, I´ll still somewhen stumble upon such fundamentals, and fail, even if the "more difficult" stuff is already understood...!!!! So, thanks a lot...!!!
Awesome video .I have locally made mppt solar charger .I have replaced it's MOSFET with other model .I will check if they are ringing . So to check onwhicj pins of MOSFET should ibconnvet the oscilloscope so I will have to play with gate resistors.
@@Electronic4U-david yes I have replaced with closest rating MOSFET. please can you clarify if I need to see MOSFET ringing which terminalsof MOSFET should I connect to which terminals of MOSFET
If you have a ring, you need to adjust the gate resistance carefully. The role of this resistance is very vital. In strong MOSFETs, this is a little different. The methods of turning off the MOSFET are very diverse and are determined according to the circuit.
@@Electronic4U-david yes that's very important to have appropriate valued resistor at gate . I saw in your video and another video of some other guy showing the ringing of MOSFET in oscilloscope. What information I still am looking for is to which pins of MOSFET do I need to connect oscilloscope to see the ringing affect . I will use variable resistor and vary Nd see wave shape to find perfect valve for gate resistor.thanks a lot once again for your kind replies . It would be helpful if you could make a video on finding appropriate gate resistor using oscilloscope for such repair works .
Высокая скорость переключения может повредить транзистор, так как могут возникать перенапряжения на индуктивностях и большие токи при запирании диодов. High switching speed can damage the transistor, as overvoltages can occur on the inductors and high currents can occur when turning off the diodes.
Hello, thank you for your support. yes It is absolutely true. A free-wheeling diode should be used for the MOSFET or inductor. I hope to benefit from your comments again. Write in your native language, I will translate. thank you very much
Excuse me .when we use bjt as Amplifier when bjt goes off an hole creates because structure of bjt .if get voltage from emmiter pwm have best situation .you can like in tl494 test it.get amplify pwm from collector .then know i want to say what .excuse me.
i mean thats just ways to drive mosfets.... i was really hoping for an explenation as to why the turn off is more important. misleading title, still good video
Hello, thank you for your comment. My intention was not to mislead the viewer. I'm sorry. My goal was to show the methods of turning off the MOSFET, such as putting a resistor between the gate and the source, or using a PNP resistor, or using a Push-pull or a totem pole in the gate path. I hope to benefit from your valuable comments again.
