A 10MHz time-domain-controlled current-mode buck converter with 8.5% to 93% switching duty cycle

Abstract

Current-mode DC-DC converters offer various advantages over voltage-mode DC-DC converters such as much simpler frequency compensation, automatic over-current protection, and faster transient response [1,2]. For current-mode control, however, an accurate inductor current sensor is required which can be very sensitive to noise. Another concern in designing a current-mode DC-DC converter is the instability under certain operating conditions known as subharmonic oscillation. A peak-current-mode buck converter, for example, may become unstable when its switching duty cycle is larger than 50% and slope compensation is required to ensure stable operation. While both current-mode and voltage-mode DC-DC converters are conventionally controlled by voltage-domain controllers that use voltage signals as control variables, the works in [3] and [4] have shown that voltage-mode DC-DC converters can also be controlled by time-domain controllers consisting of only time-domain circuits such as voltage-controlled oscillators, voltage-controlled delay lines, and phase detectors (PD). Because time-domain controllers do not use any wide-bandwidth error amplifier, voltage comparator, and passive RC filter required for conventional voltage-domain controllers, they consume much less power and occupy smaller silicon area.