How the 110/220VAC switch on an SMPS work

[CoffinDodger]

Been having a little trouble looking this one up since.  All my searches just bring up topics about plugging 110 VAC devices/appliances into 220 VAC. 

So the source voltage selector switch on my little Chinese SMPS.  Would like to get an idea as to how exactly it works as it looks like it's tying the neutral between the filter caps on the DC side of the rectifier.  I'm assuming the Caps act like a voltage divider for the 60hz 120VAC and this some how biases/bumps the DC side so the circuit thinks it has 220VAC.  Not really sure but I drew up a circuit based on what I see and probing.

It doesn't help that i'm trying to repair the little guy since I fat probed it a while back.  I was trying to get a measurement of VCC on the switching regulator IC and my DMM probe lipped and shorted VCC to OUT and blew open the whole switching circuit.  I've replaced everything i've found to be blown: MOSFETs, BJTs, resistors, rectifier, and fuse.  Then tested the remaining components in the switching circuit.  I'm sure there's a good chance the IC is dead, but I'm hoping not.

[Prehistoricman]

I've attached a simulation of the rectifier with and without the voltage doubler.
In 110 mode, the two diodes at the top of the bridge (sorry I couldn't make it diamond-shaped) are bypassed/unused. The remaining two make two half-wave rectifiers that charge each cap separately.

[Prehistoricman]

I should add that the 110 circuit can then be massaged and simplified in a really satisfying way, and it becomes more obvious how it works.

[CoffinDodger]

That makes total sense.  Forgot about voltage doublers  .... So measured the output of the doubler circuit and it's approx. 340VDC... So that's good, took a look at the LD7575PN datasheet to find the next rabbit hole and I think I found my problem.  When I fat probed Vcc with OUT it's very likely I fried the current sense pin seeing as the resistors it pulled from were about vaporized.

It's a dead chip  much like this horse.  One more dead silicon soldier.  Thanks for the lesson!