Voltage control of flying capacitor in adaptive multilevel converters

Abstract

In described examples, a DC-DC converter provides electrical power. The converter includes an inductor and a flying capacitor. In response to an input voltage transitioning from below a normal operation threshold to above the threshold, a first transition phase and a second transition phase are repeatedly performed. The first transition phase comprises coupling an input terminal of the inductor to a ground, and the second transition phase comprises delivering power through the inductor by discharging the flying capacitor through the inductor. After the input voltage is above the normal operation threshold, and a voltage across the flying capacitor has reached a target voltage proportional to the input voltage, a charging phase, a freewheeling phase and a discharging phase are repeatedly performed. The charging phase comprises charging the flying capacitor by coupling the flying capacitor to the input voltage, and delivering current from the input voltage through the inductor. The freewheeling phase comprises coupling the input terminal to the ground. The discharging phase comprises coupling the capacitor to the input terminal to deliver current from the flying capacitor and discharge the flying capacitor through the inductor.