LM3478: Minimum load

Hi user,

There is a minimum on time spec, which leads to the minimum load. The max value of the min on time (600ns max) according to the datasheet. If you sepic primary inductance is Lm, switching frequency is Fsw, then the minimum load to cover the worst case can be calculated by the following formula:

Pmin = 0.5 x Lm x Fsw x (Vinmax x 600ns /Lm)^2

Increasing the inductor value can reduce the Pmin.

Thanks,
Youhao Xi, Applications Engineering