Guru
Joined: 08/02/2015
Location: New ZealandPosts: 1136
| Posted: 11:28am 04 Feb 2023 |
Its been a good while since I looked in my box of inverter half finished projects, specifically the PI Pico RP2040 Controller; the original version can be improved upon and implemented in a more modular fashion. With JLCPCB lowering their prices of 100mm footprint 4 layer boards to $7, it makes better sense to alter the circuit somewhat and redesign for 4 layers, achieving better noise and EMI performance.
So a new schematic and PCB, the new PCB has the power supplies and AC current\voltage sensing split off on their own "Hat" 2 layer modules 100 x 50mm, these sit above the main 4-layer CPU board. I can re-use the PSU module in other projects as its somewhat generic with its 12, 5, 3.3 volt outputs.
The new controller still uses the PIO to create the SPWM wave form, but I have ditched the PIO generated dead-time delays, instead have opted for using 2 tiny 1/2 bridge chips each with variable dead-time adjustment. Each 1/2 bridge chip is used in a complementary low side driver format to allow multiples of "E-Opto" isolated mosfet drivers in an interlock arrangement on the 1/2 bridge mosfet power modules. These 100 x 100mm boards can be connected in daisy-chain for whatever power output is required.
Still want to use "Feed-Forward" DC battery voltage sensing to control AC output and is simply done by the CPU selecting one row in a table of pre-generated SPWM lookup sine values based on a modulation depth, there are hundreds of rows of 180 degree value range to choose from. After every 50 Hz period a new row can be selected depending on voltage.
I will start posting the schematics with comments then the PCB layouts.
CPU:
Here we see the RP2040 module connections, not all pins are used, some are output to terminal strip for generic use. The on board switching PSU has been turned off and replaced by analog DC inputs, noting that a 5v rail has to be present in order to disable the PSU chip, or it could be unsoldered from the pcb.
Getting late, continue tomorrow...
Mike
Edited 2023-02-05 05:54 by Solar Mike