The use of light-emitting diodes needs to be driven by current source (or constant current source), and the bead string of the landlord is driven by voltage source without resistance. Due to the nonlinearity of the diode (as shown in the figure), when the voltage rises, the current flowing through the bead string will greatly increase, thus burning out the diode. After the weakest LED is burnt out, others will not continue to burn out due to the open circuit protection.
It is suggested to reduce the number of beads and calculate the required current limiting resistance according to the lowest voltage and highest voltage that may appear in your power supply. The principle is:
1 ? When the voltage is the highest, the working current of the bead string is still within the allowable range;
2 ? At the lowest voltage, the bead string still has enough working current to avoid excessive brightness drop;
3 ? Under the above conditions, connect as many LEDs as possible in series (this is more efficient).