Size and cost reduction of the storage capacitor in AC/DC converters under hold-up time requirements

When a designer is looking for the best option to implement an AC/DC converter which complies with the customer requirements (size, cost, regulations compliance, etc.), the features and capabilities of each alternative topology must be checked. In AC/DC converters under hold-up time requirement, the size and cost of the storage capacitor is one of the decisive aspects, mainly in low power applications. Is a 400 V_DC storage capacitor voltage always the best option?, or some other voltage values can provide similar or even better results?. In this paper, the main factors that determine the size and cost of the storage capacitor will be revised. Besides, some design and selection criteria will be provided.