Author Topic: Can anybody make sense of this?  (Read 1232 times)

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Offline MadScientist267

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Can anybody make sense of this?
« on: March 18, 2014, 04:18:28 AM »
I have a Ryobi P130 in-vehicle cordless tool battery charger that I'm looking into doing some modification to so as to come out with an isolated power supply.

Here's the problem: The topology is not clear, and google isn't providing any help on the transformer or even the board. The only information available is the user manual, which of course doesn't tell me what I need to know.

It has traits of both flyback and forwarder, and a rather unusual utilization of a primary side main filter cap (across pins 1 & 2 in the schematic below). The drawing is not complete, however does contain all of the components in the "grunt" section. I included the voltage feedback and current sense networks to help with "the big picture" just in case there's a hint in there somewhere that means something to someone that I'm missing.

To clarify what I do know about the transformer:

Pins 1 & 6 are a coil, and from what I can tell, is 4 in-hand litz wire. It is isolated from the other coils.

Pins 4 and 5 are multiple in-hand, but exact number going to each pin is unknown. It appears to be at least 4 each.

Pins 2 and 3 have low impedance continuity to pins 4 & 5, and are 1 in-hand each.

The cross section of all of the wire is identical.

Below is the schematic I've come up with, double and triple checked for accuracy at this point, along with a pic of each side of the board, the top down view containing a lighter for scale.

The unmarked non-polarized capacitors in the schematic are of the small ceramic variety, I did not dig up their values in the interest of time. If anyone thinks they'll help, I have no issue retrieving them.

The diode above the schottky is a small (~1A?) epoxy bead type. The Fluke shows ~0.9V across it in diode check mode.

The diode in series with the 82R for Vfb is a signal diode.

The value of the MOSFET gate protection zener is unknown.

Any insight as to the configuration of the transformer, the actual topology in use, and why the 1000uF/50V electrolytic is where it is would be greatly appreciated  :o

Steve

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