This is why I prefer to use a LED driver chip with on board MOSFET.
I am currently doing a 1A driver for 16 white 2.85V LEDs and a 48V Vin.
Using a TI LM3414HV. I can set the switching frequency between 250 Khz and 1 Mhz.
This circuit is almost 98% efficient using a 250 Khz switching frequency and a 1.5 mOhm 33 µH inductor which keeps it in continuous conduction mode. I could use a less expensive 110 mOhm inductor and lose 2% efficiency using a switching frequency of 400 Khz.
Very simple, low parts count, and minimal real estate. And I do not have to manage the PWM.
Source: TI WebBench
Could you send a picture of the inductor L1
I have not finalized the BOM. I have a footprint on the PCB that will accommodate over 50 BOMs. I have designs for 500mA, 750mA, and 1A with efficiencies ranging from 94% to 98% all using one PCB layout.
The easiest way to make component selection is to use TI's WebBench app. The you go to the BOM and pop up a list of alternate parts for L1. You can easily see many trade offs between cost, footprint size, height, and DCR. After selecting a new inductor it will recalculate the optimum switching frequency, efficiency and thermal characteristics. It is a great learning tool. When you change a part value or target efficiency you can find exactly what parameters are affected.
The LM3414HV datasheet has a good 1A design and an eval board for it.
The one inductor for the above circuit was the $2 (qty 100) Bourns PQ2614BLA-330K
But with the low DCR the winding is very heavy and the inductor is too big at 1.098" L x 0.780" W (27.90mm x 19.80mm)
Looking at my latest BOM this 68µH, 140 mOhm, Panasonic ELL-8TP680MB 0.315" L x 0.315" W (8.00mm x 8.00mm) Height: 0.197" (5.00mm) is a contender.