Electronics > Beginners

MOSFET low side switching, Opto-Isolated Driver, isolated Amp Votage sensing !

<< < (4/5) > >>

HB9EVI:
I don't see, that the UCC27424 is isolated at all.

If you go for the VO3150, you are using it like your current opto; the LED is fed by the uC circuit, the rest by the load circuit.

castingflame:
Thank you HB9EVI. Appreciated  :-+  1 down, 1 to go.


On to the next ...

HB9EVI:
Still, you should watch out for the Vgs; the VO3150 has a typical high voltage level of Vcc - 2,1V, so you are about to exceed the typical Vgs of 20V.

castingflame:
Yes, I need to make sure I reduce the voltage for the VO3150 and the FQP30N06L.

With that in mind I have looked at the voltage and current requirements for both components in their datasheets.



VO3150  MOSFET driver    Datasheet http://www.ti.com/lit/ds/symlink/ucc27424.pdf][url]http://www.ti.com/lit/ds/symlink/ucc27424.pdf[/url]

Supply Voltage = 4 to 15v
(A/B) Input Voltage = -2 to 15v

OUT_DC Output current (OUTA, OUTB) DC = 200mA    <-----
Output Current @14v  = 4A                  <---- I am confused between these two quoted figures as they both quote Output Current.




FQP30N06L MOSFET    Datasheet  http://www.mouser.com/ds/2/149/FQP30N06L-112819.pdf

I can not see in the data sheet the Gate to Source current requirements.




While I understand that a MOSFET is a voltage controlled component, the reason - as I understand it, for using a 'Driver' is to over come the capacitance issues when trying to switch the Gate of the MOSFET at a higher frequency - by 'Driving' the Gate with a higher current. Of course my fundamental understanding could be incorrect as I have had to try and get to grips with a lot over the last few days.


What I am really trying to understand is...


To provide the correct voltage and current for the VO3150 to drive the MOSFET correctly from my 24v 'n'Amp supply ...


Do I need a Buck Converter to supply the correct voltage and current for the VO3150 to drive the Gate of the MOSFET using my 24v supply OR can I use passive components, like a voltage divider, to supply the correct voltage at a much lower current? I can not see the figures in the data sheets to enable me to work out exactly what I need other than an educated guess. I wish to understand what I am doing, not just get the circuit working.


It is also worth noting that I may not even use PWM for the Driver/Gate in the final design but at this point I wish to include that as part of my design so I can treat it as a practical learning exercise and change the design later if need be.



 :phew:  Paul

HB9EVI:
You are messing with the datasheets; you don't have the parameters of the VO3150 but of the UCC27424.

The VO3150 delivers up to 0,5A

You're right; the FET is voltage controlled, since its gate is isolated from the conducting channel, it acts like a capacitor; to build up a voltage in a cap, there has to flow a current - the higher this current is, the faster you reach a certain voltage.

So, if you drive a FET directly from a uC which sinks or sources maybe 25mA, it can take a considerable time to get the gate of high power FET charged and conducting - in other words - when using a FET driver, the parameter of sink- and sourceable current tells you, how fast you can switch the FET on and off - via I = dQ/dt

0,5A for a driver is not such a great parameter; there are drivers, which can sink and source several Amps, but it's surely better than your setup with a common opto or directly driven by a I/O-pin of a uC

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod