# LTSpice SEPIC simulation current spikes

I am designing a SEPIC power supply using the LT3758. I have simulated the circuit in LTSpice and all the waveforms are as expected except the L1 current. Here I see massive overshoots when the MOSFET switches on (eg normal current is about 3A pk-pk and overshoot goes up to over 20A). The spike is extremely narrow (< 1nS).

I am new to LTSpice, so might be missing something obvious.

Is this spike real or a simulator aboration? What could be causing it and what can I do about it?

Input +28V, Output +40V 1A.

 I have posted a follow on question here LTSpice SEPIC design low freq ringing

• Are you using realistic values for parasitics? – PlasmaHH Jan 1 '16 at 10:59
• If you put 0.01 ohms in series with the inductor what happens. – Andy aka Jan 1 '16 at 11:21
• I see you are using coupled inductors; if you do not use a realistic model (preferably from the manufacturer), your results can contain 'interesting' artefacts. I have had this issue and it mostly disappeared when I used the manufacturers model. – Peter Smith Jan 1 '16 at 16:53
• The V1 source also has 0 resistance. Add the expected ESR of your power source to that. – rdtsc Jan 1 '16 at 17:35
• And why V=50 on C5? – rdtsc Jan 1 '16 at 17:37