This is the best tutorial and best tutor I have seen on RU-vid so far 👍 I have subscribed to your channel and looking forward seeing more videos and tutorials from you. Do you have any tutorials about simulating a pwm source or generator?
Hello Hassan AR! I am happy you enjoy my videos! Regarding PWM sources, basically you need to set up a generic voltage source as a pulse source and configure all the parameters you are interested in. This video should help - ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-nPZ7vneN3v8.html
Great simulations - thanks for making them available. I tried changing the series resistance for V2 in the boost.asc simulation from 1K to 100R, which gives a better waveform at the gate of the MosFet as it is capacitative, increasing the efficiency from 91.1% to 95.6%.
I like your intro, BTW; they have small intro. explanations about what is going to be covered, and then you have your channel intro. - which is very short, and not annoying in anyway, IMHO. Not-to-mention, you cover topics that are generally needed knowledge in order to understand most electronic circuits, again IMHO. Keep up the great work!
You can avoid such "free energy" cases during the simulation when you start your power sources at 0V during the transition simulation. Otherwise LTSpice calculates an unrealistic operating point for the start of the simulation, where there is allready energy stored somewhere in the circuit, which was never drawn from the power source.
I'm happy you liked these! I wanted to lay some ground work regarding SMPS simulation and afterwards I will be getting to filtering also, as you previously requested. Its just gonna take a bit of time
Your LTspice video library is really wonderful. But how about SiC MOSFET's? Do you mind if you simulate SiC MOSFET circuit on LTspice? Some companies such as Cree has given their SiC MOSFET LTsice models. If you simulate them you will both enlarge your library and teach us also an unknown thing and help me my problems. Thank you a lot...
Thank you for your video and explanation. One thing I just don't get is why many people show current going from positive to negative when in fact electrons go from negative to positive. I learned vacuum tubes before semiconductors, and I know for a fact that a heated cathode emits electrons which is negative in relation to the plate. Why all this confusion? Is this just to make things seem simpler to non-engineers?
Hello Craig! You are right, the conventional representation is that current goes from positive to negative, but the current carrying electrons go from negative to positive. The reason for this, from what I found, is that the direction of current flow was established before the electron was identified (it was assumed that there are positive charge carriers so current should go from positive to negative); to keep thing simple, people just didn't change it afterwards.
In all of your simulations you show the behaviour of the circuit in the "steady" state after several ms. Could you explain why in case of boost and buck conv. the voltage first goes up way higher than it should? Isn't this related to the oscillator that we are creating by connecting L and C?
The initial spike does not have to do with the LC circuit, but the oscillation that happens afterwards - until the output stabilizes is influenced by that. Unlike a proper power supply, I am using a fixed duty cycle regardless of peak current or output voltage - basically during the initial period the current in the inductor rises to higher values than in the steady state and then it has to drop down, but it can't do that instantly since the switch continues switching, so the output voltage rises above the needed value but after a while things stabilize. A proper supply with a proper feedback network would not let this happen.
Why you use for driving mosfet gate transistor 2N2222 instead directly by using voltage V2 producing pulses (practicaly any shape you wish) (at 9:47) ?
Both ways will work of course, I think I was just trying to make a more realistic driving circuit. Using a dedicated switch (SW) from Ltspice would have also worked. Usually if you build a high side driver its quite difficult to properly drive it, most likely you will have an NPN transistor somewhere driving the PNP (or Pchan mosfet) transistor. I think I was intending to vary the input voltage, and then the pulse source would also need to be varied in accordance - if it was referenced to ground, like this it was easier.
No, the direction of the current trough the inductor does not change (going from top to bottom); only the direction of voltage is different - when the inductor is a load you have +/- and when the inductor is a generator its -/+ but current direction trough the inductor is the same. The same way in the above diagram for the capacitor, current direction changes - once current enters the capacitor, once it exits, but voltage polarity stays the same.
If you are making a simulation with an ideal voltage source as power supply and no wire parasitics, then the capacitor is not needed. In real life on the other hand, the wiring going from the input supply up to the SMPS (wiring between the switch and Vin) has quite a bit of inductance and resistance; by placing a capacitor on the SMPS input, the switch pulls energy directly from the capacitor during fast switching, and then the capacitor gets re-charged from the input supply more slowly trough the input wiring. This keeps input noise and ripple much lower and maintains the SMPS input voltage more stable. You can try to simulate such a circuit without an input capacitor but adding ~1R and ~5uH between the input supply (Vin) and the SMPS to see how the supply would behave without C1; and afterwards, add C1 of course.
Hello Dave! Well if you are interested in formulas, most SMPS datasheets from major manufacturers contain a design procedure; One such document would be this: datasheets.maximintegrated.com/en/ds/MAX16930-MAX16931.pdf See page 18-19 on the buck input capacitor
Hi, you have to put the coursor over the component you want to measure then, Alt + click (Alt will display the termometer). Once you have done that a graphic must show. Click over the name of the new graphic (typically displayed with the same color as graphic) and a pop up window will be displayed. I'm using LTSpice XVII and is kinda different from creator's video but this must work for you as well.
Hello Mr. Remmoz. You are right... But I think it was based on your observations that I no longer use white background, this video was unfortunately done before that point... Thank you for all your feedback, I constantly try to improve video quality, and viewer feedback is the most important.
