Hi,
Apparently this is the PS RPS-1500-xx MEAN WELL line.
U7 (pin2, J2_2) gives +5V SB.
T3 (TIP122 Darlington) forms from +26V -> +13V to power the drivers U9 & U10 [Vcc 3] (UCC27424 s) of the inverter itself Q13;Q14;Q15;Q16 and has a switching circuit (HV-ON) Q11;Q12 that controls PWM module (PCB1 DC1500_CNTRL_BORD).
Q17; SCR1 & ZD1 - OVP.
It would be interesting to see the diagrams of the PFC & PWM modules themselves.