So I was designing a boost converter circuit with a BJT, but somehow, while doing research(like I always do) I found out that a MOSFET would be very much efficent. So I looked for a common one: IRF3205. My questions are;
1. Will the circuit actually run?
2. Will the mosfet have any issue because of no square wave input?
3.Let's assume that The dc input is 9v. Will the mosfet turn on because of the minimum vgs(th)?
4. Will a BJT be a better choice?
It is just a normal boost converter with a bjt, but in this case, the inductor is a torroid with primary and secondary winding. (Secondary to drain, primary to gate.)

 

You'll need to show us the circuit schematic.

 

Vgs(th) is the threshold where the Mosfet is turned on only a tiny amount (250uA which is only 0.25mA), it is almost turned off.
The datasheet of an IRF3205 shows that it turns on very well when Vgs is 10V, less turned on with 9V.

If the Mosfet input is not a squarewave then it will waste power when it is on the input voltage slopes.
A squarewave causes it to switch on quickly then Vds is low so wasted power is low, then it switches off quickly then current is zero so wasted power is zero.

You did not post your schematic so we do not know if a Mosfet will do anything in your circuit. "Transistor boost converter circuit" in Goggle shows 35 circuits on each page for about 8 pages.

 

Its just like a 1 transistor boost converter circuit using bjt, but this time, I want to turn things upper notch so I want to use a mosfet.

Just like this one:

And the one where the square wave input is the driving switch:
www.learnabout-electronics.org/PSU/psu32.php
Also, are There any mosfets that can turn on fully well with 3volts?

 

A.G. is correct in that without a specific circuit the best that you can get is GUESSES. So draw out the circuit on paper, clearly, and then either scan it or photograph it, and attach it to your next post. WE can provide good help if we have enough information, otherwise you will get a bunch of guesses that may not relate at all to your question.

 

My cheap solar garden lights use a simple voltage boost circuit like that.
I have seen some Mosfets that turn on fully with a Vgs of only 3V. Go to Digikey and search there.

 

Ok. I'm gonna do that.

What if I use irf540N?

 

An IRF540 datasheet tells you that its Vgs needs to be 10V for it to fully turn on.
An IRL540 turns on fully with a Vgs of only 5V and turns on pretty well with 4V. See the "L"? L means logic level.

 

Ok. Would a BJT be a more preferrable and better choice then?
This circuit......

 

The 8N60 FET in that video has a 600V Vds rating, whereas the IRF540 rating is only 100V. Depending on the coil inductances, you may get >100V on the drain in that circuit and risk frying the FET (or bjt). The feedback voltage to the FET gate could also be excessive (>20V). Voltage limiting for both the drain and gate voltages would be advisable.

 

That means adding a gate and drain resistor right?
But the truth is: I wan to convert 9vdc to 96v or 90v dc output. Its for a home appliance.

The strange thing is in the video, he used no square wave input or any of such with a mosfet for that matter

 

That means adding a gate and drain resistor right?

No. There is already a gate resistor. Zener diodes or Schottky diodes could be used to clamp gate and drain voltages to a safe level.

I wan to convert 9vdc to 96v or 90v dc output. Its for a home appliance.

What home appliance? The circuit shown is a low power one only.
To get 90V output at a current of, say, 1A would require the 9V battery to supply more than 1A x 90V/9V = 10A.
If your 9V source is a little PP3 battery then that would be impossible. If the battery can supply only 100mA, for example, then the maximum output current of the converter would be less than 10mA. If Volts go up the current comes down.

The strange thing is in the video, he used no square wave input or any of such with a mosfet for that matter

The circuit does not use a square wave source. The gate is driven by the voltage pulse generated in the secondary winding over the inductor, as a result of transformer action.

 

Since there is no squarewave then the Mosfet ramps and heats which wastes power. That is why the Mosfet has a fairly large heatsink.

 

No. There is already a gate resistor. Zener diodes or Schottky diodes could be used to clamp gate and drain voltages to a safe level.

What home appliance? The circuit shown is a low power one only.
To get 90V output at a current of, say, 1A would require the 9V battery to supply more than 1A x 90V/9V = 10A.
If your 9V source is a little PP3 battery then that would be impossible. If the battery can supply only 100mA, for example, then the maximum output current of the converter would be less than 10mA. If Volts go up the current comes down.

The circuit does not use a square wave source. The gate is driven by the voltage pulse generated in the secondary winding over the inductor, as a result of transformer action.

Dc input is ~9v 4a

 

OK, in posts #13 and #18 we finally learn the desired output voltage and the available source power, volts and amps. The challenge is that the voltage step up is over 1:10, which is rather high for a simple converter. Also, the maximum available input power would be 36 watts (9V x 4A), and so at 100% efficiency the output could be 0.30 amps. With no clue as to the desired power out it becomes confusing, and a lot more complex. So here is where more information is needed, since there are real limits on what could be achieved.

If I could design equipment that exceeded 100% efficiency I would be quite wealthy, even very rich.
And unfortunately I would not be able to share those designs in this forum.

 

High efficiency means low losses. Use a Cmos squarewave oscillator that draws almost no current. It and a Cmos inverter drive two NPN and PNP emitter follower buffers that drive the gates of two Mosfets that drive the transformer push-pull.

 

Could you please give me a circuit diagram? Thanks.

 

You did not say how much current you want at 96VDC.
Here is a squarewave inverter circuit: https://www.homemade-circuits.com/7...other_Simple_NAND_gate_Inverter_using_MOSFETs.
It produces a 150W AC output. If you select a transformer that is 67V to 24V center tapped then a normal one is 120V to 43V center-tapped. Full-wave rectify and filter the output for 96VDC.

 

High efficiency means low losses. Use a Cmos squarewave oscillator that draws almost no current. It and a Cmos inverter drive two NPN and PNP emitter follower buffers that drive the gates of two Mosfets that drive the transformer push-pull.

The original post was showing a switching power supply circuit which under ideal conditions nay be more efficient than an inverter with a transformer and rectifiers. AND, even with 100% efficiency it is not likely that with 36 watts in there will be over 36 watts out. And 30 watts is not enough for any useful kitchen appliance that I am aware of. So at this point I ask just what the TS is planning on powering with the sought-after power inverter circuit, and just how much power does that device require. A whole lot more information is required before anything better than guesses can be provided.

 

OK. Its time I come straight. The circuit is a security system with alarm and others. I WANT TO JUST MAKE IT SIMPLE AND EASY without any Ic component here. I want to add more FET'S ''IF I GET THE DESIRED OUTPUT''. I like circuits that even a 5 year old can learn.

If everybody remembers, I asked:
''4. Will a BJT be a better choice?''