Efficient Boost Oscillator Led Lamp

[SkyWatcher123]

Hi all, I changed out both NPN transistors for smaller rated ones.

I used a BD135 NPN as the main drive transistor and a 2SD882 NPN for the other position.

The efficiency is better, getting a noticeable increase in light output at only 134 milliwatts input.

These smaller transistors have a higher gain, so that might also help and probably waste less power also.

Looking at the led bulb at ceiling height burns my eyes, so it is fairly useful light output.
peace love light

[nul-points]

hi skywatcher

good move on the transistor change, it can make quite a difference to use some with a lower ON voltage

ah ok, i wasn't sure how 'gutted' the LED lamp was

if you still have the utility connector end of the circuit in place then it should have its own rectification in place (and you might find you can really reduce the size of the output cap, make it non polarised, or even remove it altogether)

if you do need to use diodes you can reduce some losses by using Schottky diodes (sufficiently high current and low-leakage rating ones)


all the best
np

[SkyWatcher123]

Hi nul-points, thanks for the positive reply and good suggestions.

The gutted led bulb is just the casing and the leds on the aluminum plate, no diodes on that existing board.
I'll look around here for some schottky diodes, I know i salvaged some.

Here are some pics of the setup.

peace love light 

https://ibb.co/T1HPJZt

https://ibb.co/0ZXhsdq

[nul-points]

hi skywatcher

that's a neat coil wind you've done there - wish mine looked as tidy as that!   

i would expect to find the drive electronics for the lamp inside the white casing between the LED heatsink and the lamp screw connector (but don't try to get inside at the moment)

if the circuit is still inside, your lamp should work regardless of which way round its 2 connections are connected across your buffer cap

if the lamp does work either way round then you should be able to remove the 200uF buffer cap (and then you can probably remove the diode too) - in which case you could try different value non-polarised caps across the lamp (in place of the 200uF) and see if you can tune the output at all to better match the output to the primary/switch side

(as i mentioned above, changing the turns ratio by secondary rewinds, might get to a better matched load, but trying various non-polarised caps** is going to be a whole lot less work!)  **check any new caps are rated well above the pk-to-pk volts across the lamp

just an idea

NB.  don't handle anything around the coil or lamp output side whilst ON or soon after switching off!


nice clean build btw!

all the best
np

[SkyWatcher123]

Hi nul-points, thanks for the positive reply.
As the circuit drawing shows, the led bulb is definitely gutted of internal circuitry.
The non-polarized capacitor on secondary sounds like something to try, I will experiment with that.
peace love light