help, how do i calculate these current things

Hi
I know some basics of electronics like watts, currents and voltages but this one thing I havent figured out.

When I read about a flashlight, someone might say that it pulls 2.5A on max and its "superbright".

How do you make the led draw 2.5a instead of 2a? There is a circuit board many times in a flashlight and switching modes makes the lamp draw different amounts of current.

Higher amps is brighter. So I mean do you give it more voltage for the led to draw more amps? Is switching modes simply swithing voltages?

Or does a circuit board usually restrain the led from receiving the battery directly, i mean something that is called direct drive. Is direct drive 3.7v on a Q5 something that makes the Q5 draw maximum amount of amps and you restrain it by swithing modes to a lower one? Lower mode has some resistors in its way to the led so it doesnt get so much voltage or something? What regulates it? The components and is it current or what..

If someone understood something that i typed and can answer something then thank you. (some calculation things like volts times amps or something that might clarify this would help a lot too thanks) I read some threads with search but I couldnt find an answer to this. :help:

If we leave out some details, I can give you a simplified answer.

Firstly, if you connected an LED directly to a battery, it would either draw too little current, or two much current, or (sometimes) the right amount of current.

In order to fix the situation of too much or too little, electronic circuits can be put between the battery and the LED. These circuits measure the current flowing, and do one of two things:

1) If the current is too low, the circuit may boost the output voltage until enough current flows;

2) If the current is too high, the circuit may reduce the output voltage until a small enough current flows.

There are different ways circuits can do this boosting or reducing, but all of them boil down to the same result at the end of the day. Actually designing the circuits can require detailed knowledge of electronics, so most people buy the circuits ready-made.

Henry of RA lights (formerly HDS) has written articles and "white papers"
Click here

Scroll down to the article regarding power supplies and LEDS for flashlights.

Ohms law applies to current regulation.....these articles may give a better idea.

Flashlights generally are "direct drive", or converter "buck" or "boost" and circuity is designed to drive and or regulate the battery power for runtime, Led shift, multiple levels etc.

Hope this helps.

jeffb

Thanks for that link. Never saw that site before.

You might try the Welcome Mat.