We are designing an LLC resonator PSU to feed a class D amplifier.
The switching frequency of the LLC PSU is 80-140 kHz. At the end of the PSU we are thinking to add a low pass filter (PI filter) with a cutoff frequency of 50 kHz.
This AMP board will be fed by 2 PSUs...one as discussed above, second we want any laptop brick to be able to feed it (usually the switching frequency of those laptop bricks are 500 kHz to 1.2 MHz) so we are thinking to add a second low pass filter (LC) with cutoff frequency of 400 kHz.
Can we have a second low pass filter (LC) on the AMP? In case of using the LLC resonator there will be 2 filters..one on the PSU PCB (cutoff frequency at 50 kHz) and second on the AMP PCB, cutoff frequency at 400 kHz.
In case that we power the AMP PCB using a laptop brick, there will only be 1 filter (400 kHz cutoff). Should we use an LC or PI filter?