On 2023-May-09, at 12:28 AM, Brent Hilpert via cctalk wrote: > I thought I must be off somewhere by 10^n when first doing the calc. The 51Ω > is 3 orders of magnitude away from the 0.01Ω on the other outputs, so a > similar diff could be anticipated on the current sense. > > The low current sense might be explained as follows: > > ...
> I'm speculating the unusual shunt regulator in the -12V output is actually a > 'controlled freewheeling diode' for a -12V bucking step-down. The choke would > be stepping down the voltage from the -12 output secondary from something > higher down to the actual -12V output. With a higher V from the secondary, a > lower current is needed for the same energy throughput, and thus sense on a > lower max current from the secondary. However, one would anticipate the > regulation V sense point in such operation to be on the other side of the > choke than what's shown in the schematic. Thinking further this morning. The TIP121 is the wrong orientation or polarity to be acting as a freewheeling conductor (--explanation). However, that's the transistor section. The 121 has a built-in flyback diode which is the right orientation (++explanation). Still some things that don't make sense though, like the high EI ratio needed from the order 100 I difference (--explanation), and how the load current would be supplied during the charge portion of the cycle (--explanation).
