I'm working on RD194 revH board to build a dimmable led driver with 27,2V and 0,6A output. According with DER278 to improve efficency I racalculated the transformer with a RM10 core.
From the original BOM of the RD194 I changrd the following components:
- transformer RM10 with primary splitted
- output diode BYV32E-200
- R6 feedback resistor 172KOhm
If I leave the original RM8 transformer, all is OK, also the output current is OK (630mA). When I replace the original RM8 transformer with the new one (RM10) the device goes in autorestart mode (the led string "flashes" about once per second).
I wound a new RM8 transformer (with the same pinout of RM10 and primary splitted), but the problem persist, while If I replace the original transformer all is OK.
So the problem is the construction of the transformer or the pinout.
The no-load condition with the new transformers seems to be identical to the old transformer (the board goes in OVP)
Please can you help me to fix this problem?