Switching action delays in voltage regulator modules

Switching actions in voltage regulator modules (VRMs) cause delays in transient responses. The transient voltage variances due to the switching action delays cannot be neglected. This paper analyzes the relationship between the time instant of the load transient and the transient voltage spikes. The worst case is identified. The switching action delays in the "step up" and "step down" transients are different. The delay also depends on modulation methods. In trailing edge modulation, the delays in "step up" transients are more severe than those in "step down" transients. In leading edge modulation, the cases are opposite. In multi-channel interleaving VRMs, there are more worst-case points in a switching cycle. However, the delays at the worst cases are reduced. Analytic formulae are provided to describe the worst-case delays in different cases.