A very simple electronic project LED driver circuit can be designed using common electronic parts like in this circuit . This electronic project LED driver circuit will drive up to 3 high-bright white LEDs from a 3v supply.
The 10k potentiometer is used to adjust the brightness to provide optimum brightness for the current you wish to draw from the battery.
The transformer is wound on a ferrite slug 2.6mm diameter and 6mm long using a 0.095 mm wire . This circuit is a Boost Converter meaning the supply is less than the voltage of the LEDs. If the supply is greater than the voltage across the LEDs, they will be damaged.
K diode can be any type of high speed diode .