The final stage of power delivery is done by a power supply when DC power is needed. The overall architecture of a power supply design involves five stages. First, the surge protection stage: the main focus is to lower the impact of a transient overvoltage. The key part here is transient, where the overvoltage spike is of short duration and the joules dissipated are well within the range of the MOV components used for protection. Second is the EMI filter stage: this stage takes care of unwanted emissions escaping the design. The idea here is to meet safety regulations and agency certifications. Third, the transformer and rectification stage: this stage transforms AC into unregulated DC power. Depending on the architecture, the designer has a PFC (power factor correction) circuit here, as well as a stage for stepping up voltage to reduce component sizes and improve overall efficiency (I²R). Fourth is smoothing: the smoothing section takes care of making the output of the transformer stable. This means it will be charging and discharging based on the load. Finally, regulation: this stage is the final step in the PSU. The designer can have a linear regulator and a switching regulator. The use of switching regulators is very common in order to improve efficiency. Here, it is very important to keep a good relationship between the output capacitor and inductor size in order to maintain the power.