I am trying to design a ultra low noise SMPS with 20 W output (85 V to 220 V) and need to make a choice between 4 layers PCB and 6 layers.
On the 4 layers we plan on having components on both sides and two ground layers. Is this a good idea on the high voltage (250 V DC) side? Should I use a component layer, ground layer, power layer, component instead?
On the 5V (secondary side) same question, should I use 2 ground layers and components (top and bottom)?
At last, 6 layers could be made better..1 components, 2 ground, 3 power, 4 hi-speed, 5 ground, 6 components.
What's your advice in order to achieve lowest noise?