Yes, it will work as long as they can share a common ground. You could also use a 3-terminal 7812 since 28V is comfortably lower than the max input voltage rating of a 78xx regulator. Power dissipation in the regulator will be the same 0.64W you've already calculated. You could provide a small heatsink to keep it cool but that's not essential as it can easily deal with that level of dissipation without a heatsink.
Thank you Pjdd for your suggestion. I would have to use the "another series regulator method" instead of a 7812 IC mainly because my objective is to build an "as simple as possible" circuit, hence using discrete components would be my first choice. And if you're interested to know, I would build a 2nd converter with an improved topology where I changed the catch diode with another mosfet as well as this "double" series reg with an All-in-one IC chip package like this:
https://www.ti.com/lit/ds/symlink/tl783.pdf. But still, I appreciate your suggestion and I especially like your idea of the "change-over supply" method to reduce power wastage.
For complex diagrams, I use CAD programs like CircuitMaker 2000, Protel and others, but for those small simple circuits, I use a very unsophisticated process - namely art progs like MS Paint, Ultimate Paint, etc. It's a legacy from the days when I used an Amiga as my main computer. Some Amiga art programs had provision to store small bitmap images as brushes, somewhat like the way CAD programs have symbol libraries.
Basic Windows programs don't have such a provision. I use either of two methods with MS Paint: 1) I made a standard bitmap image with various symbols at the top of the page. I Cut/Copy and Paste the symbols and arrange them as needed on the lower part of the page. 2) I save each symbol as a small individual bitmap image file and store them all in a common folder. Then I use the "Paste From...." tool in MS Paint to call them up as needed.
After the drawing is finished, I save the page with an appropriate name and crop it as necessary. Irfanview is very nice for cropping and other manipulations. The whole process is rather tedious and not really suitable for large complex diagrams. OTOH, I like the ease with which new symbols and elements can be created, and the way the schematics can be saved directly as bitmap images with a wide range of formats to choose from. PNG is perhaps the most efficient format for images with a small number of different colours. Many of the small schematics I've posted in this forum are less than 1KB in size.
I think I would just stick to LTspice when posting a schematic. Everyone has their own style which suits them best, and most probably you've already mastered your way for some time. :-D
And that reminds me of something else. If I may make a suggestion regarding your images: Take this latest one as an example. It's 1.40MB which is quite large, especially for those with slow connections, and it's not as clear as it could be. It can be much improved after you've downloaded it from your Blackberry. I did a few things to it and re-uploaded it here.The one on the left is 40.3KB and the smaller one on the right is 12.5KB. It took me a couple of minutes with Irfanview.
You definitely could suggest, because when you suggest, I learned. I am a little surprise as you knew I was using a Blackberry to capture these photos, though it is actually very simple to find out by copying the image URL into this site: **broken link removed**.
My intention for such a high resolution is because just in case someone would be interested to view a detailed information from the picture as sometimes I do post the actual connection on breadboard, etc. The image I attached earlier was abit hard to see despite large file size was most probably due to my shaky hands, my apology.
I think I'll start down sizing my uploaded images from now on, as I did forget that not all users have fast enough connection speed as I do. Thanks for the reminder!
---------- Post added at 00:49 ---------- Previous post was at 00:35 ----------
Here is some updates from my hardware progression.
Attached is the breadboard connection of a
shunt linear regulator. The power resistor has a 10W rating and it is rather hot to touch after some time although only dissipating of only about 3.52W! And if you look at the long piece of red wire connecting to the right, it is actually being connected to the Vcc terminal of the IR2117 gate driver. The whole system works.
The edaboard_oscope_Vz.jpg image shows V(z) in CH1, a 11.86V value very close to the desired 12V.
But what I could not understand is why V(z) has a 4V when I had off the main 100V supply. This 4V only disappears when I switched off the Function gen. By the way, the function gen. is providing a 100kHz, 50% duty cycle, 10Vpk-pk voltage PWM. edaboard_oscope_Vz(off).jpg depicts this.