Regulated switched-capacitor power converter (SCPC) is a critical class of power management integrated circuits, which is widely utilized in today's portable electronic devices. The importance of SCPC is demonstrated by its capability of providing up/down dc-dc conversions without inductors and generating less conducted electromagnetic interference to other systems. Until now, however, there is lack of discussion on optimizing the performance of regulated switched-capacitor power converters from the design perspective. In this research, different design techniques have been investigated to significantly enhance the performance of the most popular regulated cross-coupled voltage doubler.

This research first analyses the problems of the open-loop cross-coupled voltage doubler deliverin...[ Read more ]

Regulated switched-capacitor power converter (SCPC) is a critical class of power management integrated circuits, which is widely utilized in today's portable electronic devices. The importance of SCPC is demonstrated by its capability of providing up/down dc-dc conversions without inductors and generating less conducted electromagnetic interference to other systems. Until now, however, there is lack of discussion on optimizing the performance of regulated switched-capacitor power converters from the design perspective. In this research, different design techniques have been investigated to significantly enhance the performance of the most popular regulated cross-coupled voltage doubler.

This research first analyses the problems of the open-loop cross-coupled voltage doubler delivering hundred-milliwatt output power. A new doubler has been developed to minimize both the shoot-through current and switching noise by adopting break-before-make mechanism and gate-slope reduction technique, respectively. In addition, an area-efficient control architecture based on direct regulation has been proposed. The proposed control architecture allows the regulated doubler to operate at low switching frequencies for better power efficiency and use small off-chip capacitors for cost reduction. Good line and load regulations, small voltage ripple, and fast transient responses can also be achieved provided that the regulated voltage doubler has large low-frequency loop gain and fast loop response.

In order to enhance the low-frequency loop gain in low-voltage condition, a three-stage amplifier based on pole-splitting loop-gain compensation has been introduced in the controller. The loop stability and loop response of the regulated doubler then depend on the compensation of the three-stage amplifier. Both active-feedback frequency compensation (AFFC) and its performance-enhancement techniques have been developed to improve the stability, bandwidth and transient responses of low-power three-stage amplifiers. Consequently, large low-frequency loop gain, robustness of loop stability, and fast loop response of the regulated voltage doubler are achieved simultaneously in low-voltage low-power condition.

To implement the proposed direct-regulation controller effectively, a three-stage two-phase switchable opamp and time-multiplexed enhanced AFFC have been developed. Therefore, by adopting the open-loop voltage doubler with break-before-make mechanism and gate-slope reduction technique as well as employing the direct-regulation controller with the three-stage two-phase switchable opamp and time-multiplexed enhanced AFFC, a high-performance regulated cross-coupled voltage doubler has been successfully realized.