A Dual-Edge Pulsewidth Modulator for Fast Dynamic Response DC–DC Converters

Abstract

Voltage regulator modules are dc-dc converters that power modern microprocessors. They must exhibit a fast dynamic response, in order to achieve satisfactory regulation performance in spite of the rapid load current variations. The pulsewidth modulator is one of the elements that determine the converter transient response. This letter introduces a dual-edge modulator that outperforms conventional modulation schemes in terms of both small- and large-signal dynamic performances: first, its small-signal transfer function exhibits a phase boost action in the high-frequency range, enabling the design of robust, wide-bandwidth control loops. Furthermore, it introduces a reduced expected delay in response to a large-signal perturbation. The modulator transfer function is derived in this letter using the describing function approach, and it is validated by comparing its predictions to SIMPLIS simulations and to the measured loop transfer function of a synchronous buck converter, designed in a 130 nm CMOS technology.