Offline
Sea of Souls

What do you all want out of a replacement regulator board?
Low heat?
Low noise?
High efficiency switching?
Smaller dimensions?

Me too.

So what do we need to do? The circuit has to output +5v and -18v from a single raw input of +6v. Now, they make ICs that are called voltage doublers and inverting doublers utilizing a strange collection of capacitors, diodes and an oscillator all in one chip (although sometimes you have to provide the large caps). I have found that these chips are a little more expensive than I would hope for just one of the many components we'll need on the board... And the cheaper ones a lot of times use oscillators within the audio range...

So I think I'll try designing a discrete voltage doubler (probably tripler) oscillating at 20k+ Hz and then use an off the shelf -18v regulator to make sure it doesn't drop too much when the batteries start to die.
The +5v rail should be very easy.

Does that all sound logical? Who has played with voltage doublers? Any comments?

Offline
Sea of Souls

Here is the original "DC CONV2 DMG" board. Problem is, I can't identify everything. For starters, the large barrel shaped part completely eludes me and 3/5 of the diodes have absolutely no markings. The transistors are labelled but the code for Q4 could potentially point to an NPN or PNP.
And since I can't figure out what the big part is, simulations in LTspice don't do a whole lot for us.


Offline

There's another schematic here: https://gbdev.gg8.se/wiki/articles/DMG_Schematics. Pretty sure the mystery part is a flyback transformer.

Offline
Sea of Souls
Knife Crimes wrote:

There's another schematic here: https://gbdev.gg8.se/wiki/articles/DMG_Schematics. Pretty sure the mystery part is a flyback transformer.

Oh nice. I literally looked at that page today for another schematic and have always glazed over that portion of the pic. It seems to be from one of the older "DC CONV DMG" boards where as I chose to draw (one of) the "DC CONV2 DMG."

I currently have three different revisions of the board on hand.

Offline

Yeah, I noticed the schematic I linked seemed to have fewer components than the one in your post, makes sense that they are different revisions.

Offline
NUMBSKULL

uXe is the only person I've seen make a "modern" power supply, though it's different than what you're doing here. Here's his documentation: https://community.arduboy.com/t/arduboy-classic/293

Somewhere there he says that running lower than -18v results in better contrast??? So You should play with that to see what the best voltage is.

Offline
Sea of Souls

I remember that project, just assumed he used the original board.
Good part, but yikes! Its pricey. I was looking at similar parts, but they all range between 5 and 9 USD for just the inverter.

I think I will experiment with the voltage. When testing the regulator board, it outputs about -22v unloaded and then drops down to the usual -18.0 to -18.6v with a 22k load. Its just a little sketchy. Too much load on the negative rail actually shut down the 5v rail to 0.

EDIT: And the RO-0524S part is physically huge!

Last edited by Orgia Mode (Oct 24, 2019 12:47 am)