DC-DC converters are widely used in energy harvesting systems for maximum power point tracking (MPPT) from energy sources. It is desirable to accommodate different energy sources (a wide input voltage VtextIN range), together with a wide range of output voltage VtextOUT range, from down-to-0.5V to up-to-2V (for button battery). Therefore, a buck-boost converter with high efficiency over a wide voltage conversion ratio (VCR) range is favorable. To reduce the volume and cost, switched-capacitor (SC) converters are in demand. However, a conventional SC only obtains good efficiency at discontinuous VCRs [1] (Fig. 30.7.1). This stems from the large voltage swing (Delta VtextCF) on the flying capacitors CF at non-optimum VCRs, leading to large charge sharing loss (PCSL) and CF bottom plate (BP) parasitic capacitance loss (proportional to Delta VtextCF 2). Multi-phase continuously scalable-conversion-ratio SC (CSC) converters [2-5] split the large Delta VtextCF into small steps, with the help of multiple internal voltage rails from the CF of the adjacent phases, and the out-phasing technique [2]. For example, in a CSC step-down converter (Fig. 30.7.1), the CF top plate (TP) in each phase connects to either VtextIN, VtextOUT, or the M internal TP rails (VT1 to VtextTM), while the bottom plate connects to either VtextOUT, ground VtextSS or N internal BP rails (VB1 textto VtextBN) '. Then the VtextCF step is Delta VT when TP connects to an internal rail: Delta VT=(VtextIN-VtextOUT)/(2M+1). Likewise, the VtextCF step becomes Delta VB when BP connects to an internal rail: Delta VB=VtextOUT/(2N+1). This reduces the PCSL and BP parasitic losses at non-optimum VCRs, and hence allows a high efficiency over a continuous VCR range. The CSC step-up converter [3] shares the same benefit. Yet, with a fixed M+N value (amount of resources consumed), once at a non-optimum VCR, e.g. VtextOUT becomes small, the reduction in Delta VB is too small such that the efficiency improvement is negligible, while the increased Delta VT degrades the efficiency greatly, as shown in Fig. 30.7.1.