well i agree with you but may i say this valid point....the regulations are somewhat "uncorrect", and for mains smps, they do have heavy restrictions on the amount of 150khz plus ripple......so for example a bcm boost pfc operating at 160khz, say if USA mains, would not get through the regs [at least not without a lot of (not-really-needed) filtering] , but in truth, that ripple would do little harm, even if only lightly filtered. So i agree with post #14 but the regs are sometimes against this excellent sentiment...unfortunately.