TIDUFB1 December 2024
After power on, the charging current of the electrolytic capacitors (C15, C16, C24, and C25) is limited by PTC RT1. Once the DCBUS voltage is high enough, auxiliary power supply and isolated power supply start to work to provide low-voltage rails for the chips to work. The LED also starts to blink, and the relay is engaged after a delay. Make sure the DC load is less then 800Ω when the board is powered on, or else RT1 is triggered by a large inrush current. Figure 3-35 shows the waveform of the board powering on under 380VAC.
Total power on time including DCBUS electrolytic capacitor charging time, auxiliary power supply start time, MCU reset, relay close delay. Figure 3-36 shows about 4 seconds power-on time under 380VAC input.