# Review of isolated dual power supply circuit for IGBT gate driver

I need to build an isolated power supply for an IGBT gate driver. +15V, -8V.

What I'm trying: I'm using a 1:1.3 transformer and driving it with a 15V square wave. The output voltage is split 1/3, 2/3, using capacitors. I'm a little uncertain on the theory of this circuit though.

I simulated this circuit with LTSPICE and it seems to be working except I am not getting the voltages that I expect on the output. Spice shows +36V and -18V. I must be doing something wrong but I'm not sure what. The right side is just a resistor/ cap acting as crude model of an igbt gate. And the bottom part generates a pwm with deadtime to drive the gate signals.

What do I change to get +15V and -8V instead of 36/-18?

• The transformer switching should be 100KHz not 10Khz but it didn't make a big difference in the simulation. Commented Mar 9, 2023 at 20:31
• Can you zoom in a little? It's not clear if the primary is 34 or 84uH. Commented Mar 9, 2023 at 20:32
• Should be 94u on primary and 158u on secondary. I got the 94u value from the datasheet of the tx, I calculated the 158u Commented Mar 9, 2023 at 20:34
• Key observation: DC current flow G-E is zero. Why not use a simple regulator (e.g. zener shunt) to set that voltage (plus generous bypass caps), and a total supply of ~23V? Then the driver can be common-ground e.g. IXDD614CI. Commented Mar 9, 2023 at 20:34
• I considered using a shunt regulator. But this IGBT needs a lot of gate drive current. All the shunt resistors I say have a max of 100mA. I'm not sure if that's enough for this IGBT. FF1400R12IP4 is the IGBT. Commented Mar 9, 2023 at 20:36