How to limit the current on the LEDs without energy loss?

Question

Electronics

A three-color LED (BL-L515RGBC-CA) is connected to the microcontroller (STM8S001J3) through resistors. The power consumption restrictions are very strict, I want to somehow save the energy dissipated by the resistors.
It is possible to put a step down LDO, but maybe there is a cheaper way?

Answer 1

a linear stabilizer dissipates as much heat as a resistor :)
if you want to make a simple reduction in energy consumption, then reduce the supply voltage to 4v through a pulse converter, then at 20 mA you will lose only 34 mW on the red LED resistor, the operating voltage of the green and blue LEDs in PDF files are described as 3.8 ... 4.5 V, but most likely there will be an unequal glow of different LEDs.
if you want to get really confused, then put an inductance in series with the LED and programmatically make PWM output control. together with the output stage of the CMOS logic, you get a full-fledged synchronous buck converter. it will not be enough to just calculate the inductance and write the correct code.

Answer 2

If indeed "Restrictions on power consumption are very strict" all sorts of LEDs are thrown out as a class.