what is DC-DC?

hi! just wonder what does DC-DC mean? is it important for the flashlight? cuz i saw in a post that if there is a DC-DC, u would have to add more $10.
thanks

AC voltage can be increased or decreased by using coils of wire and inducing a current.
If I have 100 coils with 110 running through them I can get 220 by placing them next to a coil with 200 coils in it. (In a perfect world) The fact that the voltage alternates between + 110 and - 110 is why.

DC does not alternate so currents can't be induced directly. In the old days DC was converted to AC, the change made, then it was converted to DC again. LOTS of energy loss Today solid state devices make this conversion with much less loss.

Let me hazzard a guess: Perhaps the light in question uses only a resistor to limit the current to the emitter. Adding a DC-DC convertor to regulate current instead of the resistor would add to the cost of the light. A good converter may make the light more efficient and help maintain a more consistant drive level throughout the battery life. DC-DC would mean DC in and DC out, as opposed to AC in and DC out in a AC-DC converter. I'm no expert, this is simply what I've learned from hanging out here.

You want that.

Simply stated, let's say you have an LED that needs 3.7 volts to run at it's brightest. If you use 2 AA batteries, they'd give 3 volts DC. A DC-DC converter would bring that up to the ideal 3.7 volts. As the batteries faded below 3 volts, the converter would correspondingly fall below 3.7 volts. On the other hand the more complicated "regulated" converter, would keep it at the 3.7 volts till the batteries went below a certain threshold.

Another example would be 1 AA at 1.5 volts that would be boosted to 3.7 volts by a "more powerful" DC-DC converter.

DC cannot be converted to a higher voltage directly. You have to change to AC first, convert, then change back to DC. This is accomplished by an oscillator circuit in the DC-DC converter that changes the DC to AC, and a rectifier (diode) that changes it back to DC.

Sounds complicated, and it is, but can be done in a very small package. Obviously some circuits do this better than others, giving better efficiency.

wow. thank you SMLLRisBTTR and others very much. that just gave me very good knowledge.
:thanks: