I'm trying to determine the proper power supply type and output current requirement to drive a three phase IGBT driver (this is a follow up to a previous question I asked, although focused on a different aspect)
I am driving these with PWM at 4 kHz, as that seems a common number (although, as a bonus question: what are the criteria for choosing the optimal frequency?). For the purposes of safety, I want to use an isolated DC/DC converter to supply the voltage that is driven into the gates. The input to that will be 12v (as this is for a electric vehicle motor) What are the current requirements for this supply?
My understanding is that the key component of this is the transistor switching time, and, more specifically, the rise time for the gate voltage. This is determined by the gate capacitance for the IGBT and the supply current (let's assume this IGBT module for the sake of clarity: Mitsubishi CM300DY-24T). The datasheet defines the input capacitance Cies as 61.5 nF. I can determine the rise time by looking at that and the current, but, how fast do I need it to turn on? Each of the six transistors will switch twice during the 250 microsecond PWM cycle, but that's not very useful by itself.
Second part of this question: for my first board spin, I used a PDSE1-S12-S15 chip. The output current for this is defined as 67 mA, which I'm guessing is way too small, although I've been hard pressed to find these modules that source much more. Although the internal details of this design are a bit vague, I'm guessing it is a switched capacitor design. As such, I'm wondering how relevant the 67 mA figure is for this use case, since it is an average.
When the IGBTs switch on, the initial current flow will presumably be much larger and cause the output capacitors in the DC/DC converter to fully discharge. I don't think adding external capacitance to the output of the DC/DC solves the problem.
I'm considering using a transformer to generate the isolated gate driver voltage. How is this generally done for these sorts of applications? I've looked at a bunch of application notes on designing gate driver circuits, but they don't seem to talk about the input power supply.