For the weakest links and operating scenarios of photovoltaic inverters that are most prone to failure, a high-performance digital signal processor is used to collect the power consumption information of power semiconductor devices, magnetic components, and automatic switching relays, with voltage and current acquisition accuracy of up to 100 mV and 10 mA, respectively. The onboard MCU monitors and protects critical components inside these devices, in addition to recording key information before and after failure, extracting fault features within 100 microseconds, and by combining an analysis of the failure modes of critical components, typical diagnosis coverage for such critical components exceeds 90%.