I ordered this inverter from Aliexpress supplier LQ Inverter Store, product link (out of stock, similar). We tried to power a water pump (900 W power, TODO: power factor?) and the inverter died after 1 minute or so. No output, dark voltage displays (both DC and AC).

The supplier said our terminal wires were too thin. I opened it finding the red LED on the SPWM board blinking in some pattern. There was no output from the DCDCs. I then found a broken Capacitor with a thermal camera. The cap shortcut the 12 V primary supply, so the PWM controller didn’t start. After replacing the cap, the inverter worked. I noticed a very high start current and a very sensible under-voltage protection (without recovery), so I needed to power cycle a couple of times until it kept working. The idle PWM burst mode causes a click noise and voltage peeks and probably a lot of EMI.

The inverter features 12 isolated DCDC converters in push-pull transformer topology working at 32,5 kHz. All DCDC use the same PWM signal and are wired in parallel.

Chips

• DCDC PWM board: 3x LM356, SG3525AP
• DCDC MOSFETS: FHP3205 (55V, 110A, 8mΩ)
• SPWM board:
  • LM393 (comparator, probably over-current shut-down)
  • 2x SLM2106 (600V high&low MOSFET/IGBT driver, 1.4/1.8A (or 130mA/270mA?), no dead-time, t_on=220ns)
  • XCL1719 (SPWM signal controller)
• DCDC Rectifier: ES5J
• Isolated SPWM Power supply: UC3843AN