Guru
Joined: 05/03/2018
Location: NetherlandsPosts: 6101
| Posted: 08:58am 08 May 2019 |
What are you exactly trying to do ?
Boost 3.3V to 50V ? Or boost 12V to 50V ? I assume the later.
You mention inrush current destroys the chip. Not sure what chip type is used.
Typically in a boost convertor the current flows through inductor and diode during inrush, and not through the chip. But the inrush current WILL saturate the inductor if no current limit is applied. This may destroy the chip.
The boost convertor will have a specification about the current it can deliver.
Looking at the SOT23 chip, it will be something like 1A max input current. If you convert from 12V to 50V (roughly 4x) the max output current will be 250mA.
A suitable resistor would be 50V/250mA = 200 ohm (220 ohm).
Please note that this resistor will consume peak power of 12.5 watt. This is not continuous, so a 5 watt wire wound resistor will be fine.
Charge time of the capacitor (99% full) be 5T = 5 x R x C = 5 x 200 x 0.0047 = 5 seconds.
Hope this helps
Volhout
PicomiteVGA PETSCII ROBOTS