Driving a JFET from a micro

[ivconic]

By Joop's calculation:

"... The remaining routines are where extra processing gets done. It is critical that all processing is complete before the next TCNT2 interrupt occurs, which depends on the TX pulse rate, TX pulse width, and sampling time.
If the pulse rate = 600Hz, pulse width = 100us, and max sampling time = 35us then the processing time available is 1667us - 100us - 35us = 1532us.
With a 16MHz clock we have an instruction cycle of 0.0625us, so there is time for 24512 code instructions, including calls and returns..."

We'll have 1532uS available for the remaining stuff to add to code if like.
So each spared uS is valuable in case you want to add more functionalities to code later.

[Vadim18]

A couple fast optocouplers in one case - HCPL-314 (0.4 Amp's minimum with 0.7uS maximum delay), this might be enough for driving mini-tesla coil directly. Also i discovered a good mosfet STB14NK60Z (600V, 0.45 Ohm, Coss 240pf/25v) i already use them in my inductor tester. Offcourse i found all this stuff from LCD TV power board.

[6666]

Hi ivconic, thanks for reply's #74 + #75, interesting that IDE code sure is a time waster, if the times are consistent maybe they can be factored into a simple PI code , UNO's are not my favourite toy but they are easy to work on and I've got a bit more interested in them since you have been using them for Bara etc.

“et al.” RE driving a PI TX fet with just a micro via a resistor, thanks for various reply's etc, my main interest with this idea is to test a lot of Russian circuits that use that simple system, yes it violates what various graphs show, but it works, who knows what is happening on the micro pin, and what current it dumps from the gate, but with 12 volts, 300uH coil and pps of ~1000, my 740's dont get hot and seem to produce an acceptable wave shape at preamp out, but I guess it needs to be tested running for a few days to see if it holds up, but I guess that active turn off on gate with a transistor should be bare minimum.

[ivconic]

For not time critical automation; Cpp is quite alright.
More human to understand and easier syntax to handle.
But for time critical and precise processes Cpp can be problematic.
First step towards assembler is direct port/pin manipulation.
And most important is to understand timers and how to handle them.

[6666]

For not time critical automation; Cpp is quite alright.
More human to understand and easier syntax to handle.
But for time critical and precise processes Cpp can be problematic.
First step towards assembler is direct port/pin manipulation.
And most important is to understand timers and how to handle them.

[daluka]

If i want to replicate Barracuda timing circuit and place CD40106 in simulator, its power pins are hidden.
Clicking on its properties i can see the hidden pins and designate them power supply connections.
But i have narrow choice.
Either Vdd or Vss or GND.

You have to edit the hidden pin and make sure the name matches the name as you wrote it on the schematic.

[ivconic]

[ATTACH]50301[/ATTACH]
You have to edit the hidden pin and make sure the name matches the name as you wrote it on the schematic.

[6666]

Been doing some testing today.
As I mentioned I drive my IRF740's direct from micro to gate via a resistor, works ok.
I went to the trouble of adding a npn transistor in active pull down config to gate
when fed direct to gate from micro the 740 current drops to zero very fast
but with active pull down tranny takes 10 micro seconds to stop
maybe I need a faster tranny.

[DonCaffeDelaSkobalj]

Common people it's 21 century. SiC FETs are reality today.

For those who wanna learn KNOW HOW driving MOSFETs and IGBTs. Take it and read all 816 pages.
Unitrode Design notes: ---> https://archive.org/download/Unitrod...andbookOCR.pdf

Usually, when you turn on the MOSFET, the drain current rises faster than the fall on voltage in the DS channel of the MOSFET. As a result, significant power losses during switching can be observed, causing same increase in gate control current.



This is example of optimal charge current envelope for fastest driving. But it's impossible mission. What is important is that the gate current has a rise time equal to the sum of the rise time of the drain current and the time voltage drop, and sufficient amplitude for an effective charge gate capacities!