How do I select the correct transformer (voltage) to drive a series of LED's.
Note: I have seen other Questions about this, but not like this here.
The voltage for a series of ordinary LED's are simple:
Example: Using 10 pcs. @ 1.6 Volt requires 10 x 1.6 Volt = 16 Volt (and at a voltage source above, using voltage divider/regulator).
But transformers, have:
- a non-load voltage factor, and;
- a the peak voltage on the AC sinus.
So take a 16 Volt transformer, then the sinus peak voltage is 16/0.707 = 22.3 Volt
Note: it is presumed the AC is already rectified to DC-sinus with diodes (bridge).
- If I go for the 16 Volt (the transformer RMS) in the LED calc, then the LED'S are overloaded from their 16 Volt max. to the sinus peak at 22.3 Volt. Considering the fraction of time they are, may still not be a healthy solution.
- If I go for the 22.3 Volt (and use 14 diodes x 1.6V = 22.4V), then they are underpowered most of the time (only full at the sinus 22.3 Volt peak). A capacitor could help, but considered as the "bulky" solution.
- The I could use one of those famous L78xx/LM317 regulators. But this poses another problem: To get the most from the DC sinus, I need the lowest sinus part AKA not the small top to get most efficiency. That means regulating a higher voltage down (chopping off the small sinus top). A capacitor could also help. Either both burns off energy as heat in the regulator.
Are there any suggestions (here answers) for the best compromise to make such LED power source?