does pwm for control brightness in flashlight works until the battery dead?

[audioguru]

LEDs take time to heat up. If the duration of each pulse is short then the current can be higher.
Every LED has a maximum continuous current spec and a maximum pulsed current spec. The maximum duration of the pulses is also spec'd then the pulsed current can be higher than the continuous current and the heating will be the same.

 

[rgbbv]

so the answer is yes? that the current pulses,regarding to the example,will be 5600mA on the high mode when battery voltage is 3v?

what about the issue of battery's voltage drop on high currents?(even if it is pulsed). the image has been taken for flashlight that uses also 3 alkaline aaa batteries.
so even if we take a strong aaa battery like energizer lithium ultimate(stronger when compare to alkaline),even this battery can,only,handle max. 2A pulsed current(when 2sec on/8 sec off=20%dutycycle).so even if we choose the resistor to give us low current like 500mA when the battery voltage is 2.25v and 100% switched:

ronsimpson:...We program the IC to give (in this case) 25% at 3V, 100% at 2.25V

even then,we can't get 2000mA(500*4) when the battery 3v without exceed the 20% duty cycle of the data sheet,and this is before i am talking about higher currents like the PULSED 5600mA or using alkaline batteries.
so how could it be?the flashlight output is more than +200lm~+1000mA,and the led can handle max. 1.8A pulsed current with 10% dutycycle(regarding the data sheet of xr-e led)

i want to mention that i am not argue,i am just try to understand it,something is not make sense to me.

 

[ronsimpson]

i want to mention that i am not argue, i want to mention that i am not argue,i am just try to understand it,something is not make sense to me.

I understand.

Capacitors are used to "average" the current from the battery. If the peak current is 4A at 25%, using a capacitor will help to average the current from the battery. A good LC filter will pull 1A at 100% of the time from the battery and deliver 4A at 24% of the time for the LED driver. A simple C filter is not as good but will help the batter. To say it a different way; LED=off, Battery and Capacitor are fully charged. Now turn on the LED (PWM). If you try to get 4A from the battery its internal resistance will cause the battery voltage to drop. The capacitor will supply much of the LED current. Now turn off the LED (PWM). The capacitor will be charged from the battery.

This type if "regulation" is never used at 5.3A like you are talking about! 1) At high current, 2) with $10.00 LEDs 3) where battery life if important, the current is monitored and regulated (with out ac current limit resistor). This type of regulation usually is good to 2% or 5% accurate.

The type of "regulation" you talk about is only used with small LEDs. It is not accurate! But it works and save a very small amount of money. One company I work for makes 12,000,000 LED products a year. A very small amount of mone

 

[rgbbv]

ronsimpson,why didn't you explain it from the begining?

only,now i understand what is ,really,the purpose of the capacitor and how it prevent the battery voltage drop.
what can i say,it is very difficult to understand this technology,if you don't know how each component function and what is its job. where are the days that every thing was simple.(in spite of the fact that we can't compare at all between the amazing power of the cree led vs the incandenscent ones).

thank you very much for your professional replies.you help me alot.