Capacitor discharge: Is gate voltage on IGBT proportional to collector?
For the IGBT driver, I suggest an isolated supply (galvanically isolated DC-DC converter) and opto-gate driver. One of the easiest ways to drive the gate is with an isolated gate driver such as the Avago ACPL-312U-000E. 

You need to bring the IGBT gate positive by something like 15V relative to the emitter to fully turn it on, and to drive it to zero (or a few volts negative) to fully turn it off. That should be done fast if you want the transistor to turn on snappily. It should never exceed something like +/-20V relative to the source. What you have there will not achieve that as the 15V from your voltage divider is relative to your load - terminal and not the IGBT source, so the gate will likely be damaged. 

It's possible a variation of your circuit with the HV section flipped (load on the IGBT collector to +100V) could be made to work.. but the IGBT gate has no path to discharge the charge so it will leak off slowly, which might be disastrous. 

If this is a welder you're making, keep in mind the load will short the 100V supply (the 1N4005 won't help) when the IGBT is on. 

Edit: you can derive an appropriate supply voltage from the 100V for the IGBT driver as follows: 

It supply between 0mA and 5mA without allowing the gate voltage to exceed the absolute maximum 20V voltage. 







simulate this circuit &ndash; Schematic created using CircuitLab