I have a 36V ebike battery that I want to use to power my dynamo bike lights (6V 3W LED lights.) I put a switch and a buck converter in between.
The schematic is as follows:
- 36V 10A Li-ion battery
- Motorbike switch with a 12V LED in series
- 22uF 50V capacitor
- TSRM 1-2465 DC/DC buck converter with a fixed output voltage of 6.5V
- 10 ohm 5W current limiter resistor
- LED Lights: Frontal - Busch + Müller Lumotec Lyt B N plus, Rear - Spanniga Solo XDvS
The problem is, when I connect the circuit the voltage at the output of the buck converter collapses (around 2.5V shows at the output.) The rear lights of the bike are on but not the front one. I tried with several buck converters of different power settings but the result is the same.
The lights are working because when I connect a 5V battery both LED lights are on. I read about starting circuits and inrush current, so I tried putting an inductor in series with the LED but there is no apparent difference.
Could somebody give me a hint on where could be the problem? If for help there would be needed more information please let me know.
Thanks @vir, indeed the problem was the capacitive load. As the dymano lights have a large capacitor to store power from the dynamo, the buck converter was entering the short ciruit mode again and again.
The solution seems to make a "soft starter" circuit. I did some research but I don't know if there would be an easy but effective solution for it. Does anybody have some thoughts/ideas on this?