Power supply revamp

A project log for OpenEVSE II

A new design for OpenEVSE - the open hardware EV charging station

nick-sayerNick Sayer 01/16/2019 at 18:570 Comments

There's been a bit of a revolution in how power is handled with this project. Along with the Hydra, I think we may migrate from a 12v primary AC/DC supply to 5v, and then derive the 12v with a boost converter rather than deriving the 5v with a buck converter.

Unlike the Hydra, however, 12 volts is not just used for the pilot generator, it's also used to power the relays on two of the AC board variants. The internal relay variant has two relays with 1W coils, so 2W of power is needed just for them. That means those variants need 5W supplies, but it's probably not worth stocking a 3W supply just for the contactor variant.

The good news is that the new PSK-P5B unit is footprint-compatible with the old VSK-S3 unit we were using on the contactor AC board - much smaller than the VSK-S5 unit we were using on the other two. This allows us to shrink the "external relay" AC board slightly (the "internal relay" board's size is dictated by the relays, unfortunately). In fact, I've managed to shoehorn the "external relay" board into the OpenEVSE board's original footprint. That means that that particular variant should install in the OpenEVSE chassis without any modification at all!