I had a weird thing happen to my inductor test circuit I built from ronald dekkers nixie clock site.
The 'scope trace was opposite to what I expected on larger inductors, the current sense resistor in ronalds design is in the + rail, at larger currents the current limit on my bench supply was being hit dropping the voltage on the + line, which was 'scope ground, so obviously the 'scope saw this as a major drop in signal voltage causing the trace to go down not up.
I dont spose many will beuild this circuit but if you do put the sense resistor in the ground leg between the switching fet drain and the - rail, then the 'scope ground is test circuit ground and then everything will work.
With the 4 820uF 25v low esr caps I can get over 50 amps through a test inductor.
The 'scope trace was opposite to what I expected on larger inductors, the current sense resistor in ronalds design is in the + rail, at larger currents the current limit on my bench supply was being hit dropping the voltage on the + line, which was 'scope ground, so obviously the 'scope saw this as a major drop in signal voltage causing the trace to go down not up.
I dont spose many will beuild this circuit but if you do put the sense resistor in the ground leg between the switching fet drain and the - rail, then the 'scope ground is test circuit ground and then everything will work.
With the 4 820uF 25v low esr caps I can get over 50 amps through a test inductor.