In this case you ned to design the driver with full load power of 36V x 1.5A = 54W. You can set the IFB current at full power to 150uA. Then, a potentiometer can be used to the adjust the operating IFB to reduce the power. In your case, the RFB value on the spreadsheet will be your potentiometer or RFB = potentiometer value + series resistor.

The idea is to reduce the IFB fed to the FB pin to reduce output current. Just make sure that min IFB doesnt hit IFBAR at the minimum IFB setting (max potentiometer resistance) at your minimum target cc operation.

For Full power Operation of LNK IC it is not possible to bring output current below 850 mA.But I want to reduce it upto 500mA.pPlease suggest the solution

If you designed your power supply to deliver 850mA at full power, the out put current can be reduced by increasing the RFB resistor.

hi,

I've designed a CC isolated dimmable led driver with LNK409 device, performing 2 different output power (15W-30W) selectable via Ifb resisitor. Since this device is no more recommended for new designs, in the future I want to migrate to LYTSWITCH-4 family. Which are the major Tips I've to consider in new design? Just for start to test new device can I start from old schematic changing the device, transformer, and few other components?

thank you for answering

The main difference between LinkSwitch-PH and LYTSwitch-4 is the switching frequency. LYT 4 is switching at 132kHz which allows you to use a smaller transformer compared with the LinkSwitch-PH design. Note also that LYT 4 is optimized for single line. There are dedicated devices for low line and for high line. The BP capacitor value for power programming is also different. Those basically are the 3 major difference from LinkSwitch-PH and the rest of the operation are identical.

Ok, very clear, thank you