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Why are they putting electrolytic capacitors in these light bulbs? The SM2082D datasheet specifically calls for an electrolytic cap, but wouldn't a power cerami
by brianpgordon 8y ago
Why are they putting electrolytic capacitors in these light bulbs? The SM2082D datasheet specifically calls for an electrolytic cap, but wouldn't a power ceramic cap last longer? 4.7uF is doable with ceramics. Is it just a really minor cost thing, and hoping the bulb fails so you have to buy a new one?
- dfox 8y agoYou have to take into account the voltage that the capacitor runs at. 4u7 200V X7R MLCC is going to be huge and certainly several orders of magnitude more expensive than Al electrolytic.
- rmu09 8y agoCould be the driver is designed for a specific range of equivalent series resistance of the capacitor. High ESR could help with peak current and EMC.
- brianpgordon 8y agoYou have to add a resistor across the cap anyway according to the wiring diagram. I think dfox is probably right that it's a voltage rating thing.
- rmu09 8y agoThat's a bleed resistor to discharge the capacitor when turning off, else it could keep dangerous charge for a long time. ESR limits current inrush into the capacitor, with ceramic caps you would need some additional current limiting. Voltage should not be that much of a problem, but there may be other issues with ceramic caps (like cracking due to thermal stress, voltage dependent capacity, microphoning, ...)