Don't be surprised if it does not work.The following guidelines are strongly recommended when laying out application circuits:
your sense res is 0.27v
You clamped the current to 0.4a.
So your sense voltage is only 0.108v.......this is below the threshold of 15% above 100mv....so no wonder the fet is on all the time.
What voltage is across the leds....?
Set psu to say 2v above this, and set the psu supply current limit to 0.6a, and try again
What is the current rating of your inductor?
What is the voltage across the sense res...if it is flat dc, and above 120mV, then the fet is broken and on all the time....or you have a misconnection somewhere
I have used normal diodes as LEDs are very expensive ( this is the diode I have used: CD123D-B140LR ).
the forward drop on the CD123s is about 0.35 V, so 10 in series is the 3.5V you measured across the diodes.
the forward drop on LEDs is 2? 3? V.
you have essentially shorted the output
the regulator is trying to produce the desired output voltage and/or current, but your load is too small
add a series resistor consistent with the expected V and I for the real LEDs you want to use
or replace the schottkey diodes with plain cheap LEDs -
digikey has about 500 different LEDs, surface mount, less than $1 (American) in stock
Are you sure your diode is not dry joint?....because if it was then the fet may get overvoltaged when it switches off.
As you know, the inductor current always needs somewhere to flow to
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