Eshal
Advanced Member level 1
- Joined
- Aug 29, 2012
- Messages
- 470
- Helped
- 16
- Reputation
- 32
- Reaction score
- 15
- Trophy points
- 1,298
- Location
- Nowhere :)
- Activity points
- 5,149
Heyyy... new thing for me. wait a second. let me understand this point.
If I reduce the voltage amplitude to the MOSFET then I can lose the efficiency. And also, the MOSFET will not work as a switch anymore, it will work as resistance instead. Is it?
And if I want to retain the efficiency of the Boost Converter then I should reduce duty cycle not voltage amplitude. Did I understand right?
Now I want to know is there any precaution which I should remember like MOSFET heating or something like that?
Also, I want to know why reducing duty cycle didn't affect too much at the output voltages. But it affect the output current.
I have heard from someone that the increasing duty cycle will increase the on time of the MOSFET and the long the MOSFET will conduct (means on time) the more the efficiency. Is it not true at all. huh?
And we drive the MOSFET switch to its minimum ON resistance if we reduce the Duty Cycle or if we reduce amplitude of voltage of the MOSFET Switch. Right sir?Yes, normally the aim in this topology is to drive the mosfet/transistor as a switch (that is, drive it to its minimum ON resistance).
Yes sir, I will surely try it in real life. But before I will attenuate its frequency which is included in the output DC voltage. See my figure in post#61 there is a frequency in the output. It is f=100KHz. Did you see? It is a boost converter (its input is DC and output is DC) so it should not have frequency at the output. So I have thought to use a PI-filter or L-filter in order to attenuate this unwanted frequency. By the way, I want to ask you sir, which filter is good to use so that my efficiency could not be reduced. PI, L or else?Yes, check for components overheating under various operating conditions:
no load
light load
heavy load
etc.
The easy way for me to test is by holding components between my fingers. If it is too hot to keep my fingers on, then it needs heatsinking, or else the circuit needs adjusting, etc.
I have learned about the parasitic capacitance but not resistance. I will read about it and then ask you question regarding with this.If you can succeed at minimizing parasitic resistances, then you have gone a long way toward obtaining maximum efficiency.
And we drive the MOSFET switch to its minimum ON resistance if we reduce the Duty Cycle or if we reduce amplitude of voltage of the MOSFET Switch. Right sir?
Yes sir, I will surely try it in real life. But before I will attenuate its frequency which is included in the output DC voltage. See my figure in post#61 there is a frequency in the output. It is f=100KHz. Did you see? It is a boost converter (its input is DC and output is DC) so it should not have frequency at the output. So I have thought to use a PI-filter or L-filter in order to attenuate this unwanted frequency. By the way, I want to ask you sir, which filter is good to use so that my efficiency could not be reduced. PI, L or else?
Got it sir.No, instead the mosfet needs a greater volt amplitude at the gate, if we want minimum 'On' resistance. (We're talking about enhancement-mode mosfets here, not depletion-mode.)
Duty cycle is a different concept from 'On' resistance.
Normally we want to have minimum 'On' resistance in the mosfet switch, whatever length of time it is switched on.
OK sir, I try with some higher value.My simulation shows that your ripple is several percent, with the 7.5uF smoothing capacitor in your schematic.
You can reduce ripple by increasing the Farad value. Example, you'll get 2% ripple by increasing the capacitor to 30uF.
The capacitor has several hundred mA going through it, back and forth, each cycle. If you find that a single capacitor gets hot, then you may want to divide the load across 2 or more caps.
Also, you have provided a link to the falstad simulation website. There are ready made circuit. Can't we draw our own to see the current flow?
Thank you.
Yes. My post #45 gave a link that will:
1) open the Falstad.com website,
2) load my boost converter schematic (battery charger version) into Falstad's simulator, and
3) run it on your computer.
Below is a link that will do the same with my simulation of your post #61 schematic (with slight modifications):
https://tinyurl.com/m2v89xx
But again I want to ask you. It is a DC to DC converter. then why it has frequency 50KHz at the output (in the yellow probe's tag, in the last Freq.: 50.0 kHz)
MOSFET switch frequency is 50KHz. Is it due to this? Should it not be reduced to 0Hz because it has DC output that's why it should be 0Hz signal. Are you getting sir what I am trying to deliver you?
Yes, I have tried. But again I have same question, I want to draw my own circuit on Falstad's simulator. Is it possible? Not the one ready made which has just to change the values for modification. I want to create whole circuit on Falstad's simulator.
Thank you.
I have gotten your words sir.By turning the mosfet fully on or fully off, we cause it to carry high current, yet without creating a resistive drop across it. The resistive drop method generates heat and wastes power.
By chopping the plain DC into pulsed DC, we can use it to operate a circuit that converts its volt level to another volt level.
We turn it on and off at a frequency which gets the best performance out of the components.
It is really a very very good simulator. It shows a current flow which help me to understand the working of the circuit. I am wonder if it has UJT too.To select which component you will place, right-click on an empty area, and select your desired component.
To clear the canvas, go to the Circuits menu and select Blank Circuit.
To save your circuit, go to the File menu and select Export. A window appears containing text. Copy the contents to the clipboard, paste it into a separate text processor (example, Wordpad). Then save it to disk.
To load a circuit file into the simulator, you must first open it in the text processor. Copy the text to the clipboard. Then switch to Falstad's simulator, select Import. An empty window appears. Paste the clipboard contents into the window, and click Okay.
oooo... thank you. finally i have some theory on pi-filter.
But there is not any formula to assist me in designing. how to start designing the simple pi-filter?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?