A SC DC-DC converter with pseudocontinuous output regulation using a three-stage switchable opamp
ISSCC. 2005 IEEE International Digest of Technical Papers. Solid-State Circuits Conference, 2005.
SC dc-dc converters with continuous-output regulation (COR) for delivering hundred-milliwatt output power have been recently reported [1, 2] . The control schemes of these converters can reduce both input-current ripple  and output-voltage ripple . These converters, however, require one extra power transistor cascaded either in front of  or behind  the power stage for output regulation. The additional power transistor increases the chip area of the converter. This paper proposes a
... paper proposes a new control scheme for the regulated SC dc-dc converter to achieve COR without using any additional power transistor. Moreover, a three-stage switchable opamp in the proposed control is developed to improve both load-transient response and light-load power efficiency of the converter. Fig. 15.7.1 shows the structure of the regulated cross-coupled voltage doubler with the proposed pseudo-continuous control (PCC). In the cross-coupled power stage, there are eight power transistors Ml1-Ml4 and Mr1-Mr4, and two flying capacitors C f1 and C f2 for voltage conversion. The additional circuitries Mal, Mar, Ral and Rar are used to reduce both the shoot-through current and switching noise of the converter, while the increase in area due to the additional circuitries is insignificant . With PCC, both Ml2 and Mr2 operate as regulation transistors, while other power transistors function as switches. Therefore, no extra power transistor is needed to regulate the output continuously. The proposed converter is area efficient. The principle of operation can best be discussed using the timing diagram in Fig. 15 .7.2. The control mechanism operates in non-overlapping clock phases Φ 1 and Φ 2 alternately. When Φ 2 = V DD , both power