Hi, I'm trying to build a power meter that has the ability to switch on and off the attached load.
The power supply for the design is created using Viper26LD in buck mode, the processor used to control the design is STM32L051. The entire design analog part I'm trying to fit on a PCB only 80mm x 55mm.
I have tried several designs, but I didn't find the solution to the following problems:
- When I issue a command to switch ON the relays so that the load gets connected to mains, the STPM32 gets fried.
- It this possible that sometimes the STPM32 get fried only by switching on the mains for the design and not necessary switching ON the load relays.
I tried to ensure some protections on ADC inputs by using TVS and clamping diodes, MOVs on power mains entry, an RC snubber on load mains entry, but no success.
Any ideas what should be done?
Looking at the STPM32 evaluation board I see no protections. Did anyone use this evaluation board to switch on the load using a relay attached?
I'm attaching the AFE design for reference.
I have done some readings on the VIN entry and the signal is like in the attached screenshot.
It seems that the diodes have no effect on the incoming voltage spike.
