Hi folks. Usually i build and tinker with Nixie tubes, so a Step-up converter is nothing new to me.
I usually use the MC34063A-based MK1,5 supply design from M. Moorrees which works wonders! Now i got a job set for me - I need to retrofit a head-mounted lamp with LED's - I got a whole bunch of 5050-style warm white LED's from some scrapped lamps (the original smps power supppled blew up) so i got a good supply of these LED's. There is 3 dies inside each LED package, and i reckon they can handle about 40 mA without any active cooling. On the original boards, these LED's are mounted in 5 chains of 6 LED's each - no resistors mounted, i guess the power supply was current limited. I milled a new PCB with room for 20 of these LED's - put them all in series, so i have a load that likes around 70V and 40 mA. I milled a pcb with a MK1,5 Power supply, replaced the voltage divider with a 33 ohm resistor for the low side, so the power supply is current-regulated, and it works just fine. The problem I am having, is the heat loss from the Mosfet and inductor - Packing this inside the bulb renders these parts at 100 degrees C, which i don't think they will last very long being that temperature... I am using a 2SK3592 switching transistor and a 10 uH low loss SMT inductor. I replaced the SMPS IC with a NCP3064B which is just a descendant of the venerable MC34063A chip, so that won't change anything really. Now, the question is, any advice on getting the efficiency bumped up a bit, and would i be better off rearranging the LED's so i have a lower voltage and higher current ? I could parallel all the LED's, but that is a big no-no as I am concerned. Any tips or advice would be welcomed ;-) // Per. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
