Performance improovement

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Hello,

I'm designing led power supply with 55 V 1,2 A output using LNK420EG. I used PI Expert. Prototype board has an efficiency about 87%. Due to thermal issue I need to achieve at least 90% of efficiency. I ask if someone can give me same trick to get it. I'm thinking to increase transformer primary inductance so flyback will work in CCM. Can LNK420EG support this mode?

Best regards,

Antonio Gabriele 

Link-Switch PH devices can work on CCM, it is designed to operate in this mode. On PiXls, if you want to operate in CCM, you can reduce the parameter KP (say 0.4 to 0.7) to operate it in CCM.

How to improve efficiency /thermals.

1. Make sure you have enough BP supply on the device, this lowers the thermal of the device and improve efficiency.

2. Reduce transformer losses - u can use a larger core area to reduce the number of turns and especially reduce the number of layers. Reducing the primary layers by one, u should see a big improvement in efficiency. If possible, the secondary should fit in one layer only.  Lower the leakage as low as possible, and minimize interwinding capacitance. Reducing the layers of the winding both help to achieve these 2 objectives.

3. In CCM. one of the major source of loss that heats up the primary switch (LNK420) is the reverese recovery of the secondary diode. These reverse recovery current is seen by the primary switch and increases losses. If you can use a low trr diode like Qspeed diodes, it will improve your efficiency a lot and help reduce thermals on the primary switch.