This can be as simple as a shunt capacitor, although the typical method is to place a pi-filter to shunt AC noise to ground. The output filter on a DC/DC converter (whether buck/boost or other topology) is a low-pass filter. Starting a Switching Power Supply Output Filter Design
As an example, let’s look at a buck-boost converter topology to see how to implement an output filter for a switching power supply.
As I’ve discussed in an earlier article on this blog, and as we’ll see from some simulation results, reducing noise depends on the values of the components in the output filter and the inductor in the circuit. In this article, I’ll show how a switching power supply output filter can be used to dampen output noise and how you can use some simulation tools to optimize your filter design for low noise. Keeping the output noise-free and stable might require using an output filter, which can be implemented using passives in your PCB layout. It’s also ideal to dampen the effects of any residual ripple from rectification or remove any noise on the input. The goal in designing these systems is to ensure stable DC power delivery to the rest of your system with minimal noise. Switching power supplies come in many forms, such as in a high-power benchtop lab power supply, or embedded onto a PCB with specialty ICs and passives.