Diode or resistor

[AttyPops]

This is just a guess because I haven't researched the boost/buck circuit that much yet - I believe the output pulse wave is being clipped (removing the negative pulse) by the diode lowering the effective voltage below the 5V that the chip is rated for. Like I said it's just a guess but it allows the chip to be adjusted lower than it was designed to go.

I thought these things output DC... there is a frequency since it ends up being a pulsed circuit to boost... but I don't think there is a negative part of the wave. I could be wrong. I think of it as "a black box" xx volts input and yy volts output pulsed (pretty fast) and smoothed with caps to standard DC. e.g. if there is a negative wave internally, it is already rectified by the time it comes out, not clipped.

@DaveP we're talking about the OPs question on why he sees diodes in boosted vv mods (see post 13). Not AC current. The implication is single battery DC non-pulsed.... so no rectification needed if the above is correct.

The "variable DC supply" you refer to is normally created with a switching regulator (or even linear), but requires 2 x 3.7 v batteries since it needs higher input than output. So people use boosting circuits to take, say a single 18650, and boost it to higher voltage.

Of course, IMHO, the easiest thing to do is use 2 smaller batteries and a switched adjustable regulator and forget boosting altogether until super batteries (like the nano tech stuff) are available. That will make boosting practical in a smaller lighter package, but that's me. To me, 2 14500s are close to the same bulk as 1 18650 so buck, no boost for me.

 

[AttyPops]

Oh, and to WillyB's point....+ 1, I just don't care that much about efficiency in this case. lol. I use those inefficient regulators as a mainstay and love em. lol. I get 3/4 to 1 full day out of 2 14500's and a 50 cent 5v regulator (OK, not 50 cents, but you get the idea). No muss, no fuss. lol.

If you do the cost/benefit calculations.... getting real efficient gets real expensive real fast. And there's little need for it. It only takes 10 seconds to change batteries. I carry a spare set anyway. lol. K.I.S.S. Keep It Simple Simon.

I usually try to remain silent when people complain about efficiency in these circuits since this whole thing is "to each his own" and I respect their concerns and admire the design of, say, the evercool. I probably won't build one however, since there's not enough benefit to justify the extra costs...(other than the fun factor).

My absolute favorite is the usual complaints about LEDs "using up all my battery capacity" or some such nonsense. lol.

So cheap regulators (vv or fixed), and diodes, and resistors, all have their place.