For this driver I tried using the TPS61288 again, it’s the boost IC used in the new zebralights, Loneoceans’ LumeX1 (although production versions use the MP3431) and the one I used when I made my first driver.
The Pulse Skip Mode used with that one allows very low power consumption at low output, but because that means the switching frequency decreases a lot at low output you get audible noise in the audio range and then flicker/blinking at low moonlight levels, hence why I switched to the MP343x in my drivers which has an ultrasonic mode with 30kHz floor (but higher no load consumption, which is why the D3AA has relatively high moon/low power consumption).
To eliminate the noise I used special MLCCs on interposers, which are very effective. And for the flickering I used a load resistor to increase the load floor, thus increasing the frequency floor, now unfortunately even with the min frequency being around 200Hz, which is usually enough to prevent obvious flickering in moonlight, there is still some visible flickering due to the unstable pulse width the boost IC has at some input voltages. Same reason the stock SC65 has visible flickering on the min mode (although apparently nobody complains about it).
If it was constant at 200Hz then it would be okay for a 10~20uA moonlight (very low moonlight), at higher moon and lows it’s already in the kHzs range so no problem there.
I could increase the load/frequency floor, but then the power consumption gains become less and less meaningful as more power is wasted in the load resistor.
So due to this I’ll probably make a new version with the MP343x.
10 Thanks
Excuse my ignorance. But would something like this be available for sale? An efficient, UDR, high cri, potted light is definitely endgame like another user mentioned.