Combiner Box / DC Switch / Surge Protection Reference Design
An illustrative smart combiner box monitoring unit reference design for the PV generation side: Hall sensors sample the DC current of each string, a high-frequency current transformer detects DC arcs (AFCI), DC surge protector (SPD) degradation and DC breaker open / closed status come in through dry-contact inputs, and data returns to the inverter / data logger over isolated RS-485; 24 V auxiliary supply. Each position is marked with the VOOHU parts available, recommended part numbers and package pinouts.
Illustrative PCB ⇄ Schematic
Illustrative top-side view arranged by functional zone (not the actual layout). Red numbered dots mark positions VOOHU can supply. Click a component on the board, an entry in the index below or a part in the schematic to see recommended parts and package pinouts on the right.
Illustrative AFCI detection topology: each string branch (or each pair of strings) passes through the primary of the VOOHU current transformer T1 (WHPT-EP100-018); broadband noise from DC arcs develops a signal across sense resistor Rb on the secondary, which AFCI front end U2 band-pass filters and amplifies for identification by the MCU; the DC current of each string is sampled by Hall sensor U3. The CT couples only high-frequency components and does not measure DC.
Board bill of materials
Summarized by position; click any row to locate it on the board above.
| No. | Zone | Position | Ref. | VOOHU category | Recommended part | Availability |
|---|---|---|---|---|---|---|
| 01 | A String sensing | AFCI arc-detection current transformers ×N | T1 | Current Transformers | WHPT-EP100-018 | VOOHU |
| 02 | A String sensing | AFCI front end (band-pass + ADC) | U2 | — | — | Non-VOOHU |
| 03 | A String sensing | String DC current sensors (Hall ×N) | U3 | — | — | Non-VOOHU |
| 04 | B RS-485 (isolated) | RS-485 terminal block | J2 | — | — | Non-VOOHU |
| 05 | B RS-485 (isolated) | RS-485 GDT | GDT1 | GDT | WHGT090V1P0A | VOOHU |
| 06 | B RS-485 (isolated) | RS-485 CMC | L1 | Signal Line Common Mode Chokes | WHAC-4532A-510U0 | VOOHU |
| 07 | B RS-485 (isolated) | RS-485 ESD / TVS | D1 | TVS ESD | WHALD30E2B | VOOHU |
| 08 | B RS-485 (isolated) | Isolated RS-485 transceiver | U4 | — | — | Non-VOOHU |
| 09 | B RS-485 (isolated) | Push-pull driver + rectifier / LDO | U5 | — | — | Non-VOOHU |
| 10 | B RS-485 (isolated) | Push-pull isolation transformer | T2 | Push-Pull Transformers | WHST06K02A0 | VOOHU |
| 11 | C Surge protection / switch status | Binary input terminal | J3 | — | — | Non-VOOHU |
| 12 | C Surge protection / switch status | DI ESD | D3 | TVS ESD | WHALD30E2B | VOOHU |
| 13 | C Surge protection / switch status | Optocoupler-isolated inputs | U6 | — | — | Non-VOOHU |
| 14 | D Control core | MCU (sensing + communication) | U1 | — | — | Non-VOOHU |
| 15 | E 24 V power | 24 V power terminal | J4 | — | — | Non-VOOHU |
| 16 | E 24 V power | Bidirectional input TVS | D4 | TVS ESD | WHTB058VA | VOOHU |
| 17 | E 24 V power | Input power-line common-mode choke | L2 | Power Line Common Mode Chokes | WHAL-7060A-102T0 | VOOHU |
| 18 | E 24 V power | Buck converter (24 V → 5 V) | U7 | — | — | Non-VOOHU |
| 19 | E 24 V power | Buck converter (5 V → 3.3 V / core) | U8 | — | — | Non-VOOHU |
| 20 | E 24 V power | Molded inductors ×2 (DC-DC) | L3 L4 | Molded Inductors | WHYT0630 Series | VOOHU |
Resources & downloads
Board bill of materials
Reference designators, zones, VOOHU categories, recommended parts and availability for all 20 positions. Opens directly in Excel.
Datasheet collection
Datasheet PDFs for the VOOHU parts recommended on this board.
Design files & footprint library
Schematic, PCB, and VOOHU part footprints and 3D models.
Coming soonRequest the combiner box / DC switch / surge protection reference design full package
Includes the full-board position list, datasheets for the recommended VOOHU parts and position-by-position selection notes. For advice tailored to your string count, AFCI requirements or communication method (RS-485 / PLC / wireless), please include it in your requirements. We reply within 24 hours on working days.
