A 6.87W 3.7-5V Input 12.6-24V Output Switched-Capacitor Sigma Converter with Multiple Voltage Domains

Boost converters are commonly used in DC-DC step-up conversion applications such as display drivers and sensor biasing. As the demand for high efficiency, high power density, and wide voltage conversion ratio (VCR) of power modules intensifies, it becomes more difficult for traditional single-stage converters to satisfy all three performance metrics concurrently. The sigma converter [1], which is a converter with input-series output-parallel connection, has been proposed to combine the merits of using two converters. This architecture leverages the high efficiency and wide VCR of a transformer for step-down voltage conversion on the high voltage side, and uses a buck converter on the low voltage side to achieve precise output regulation. Several sigma converter topologies based on switched-inductor converters and switched-capacitor converters (SCCs) have been proposed [2]–[4] and achieved wide VCR range, high output power and high efficiency as compared to a single-stage converter. However, the switched-inductor converter on the low-voltage side has slow load transient response and low power density. To obtain fast load transients in step-up voltage conversion, a reverse SC sigma converter is proposed [5] using a SCC in high-voltage (HV) domain and a low dropout (LDO) regulator in low-voltage (LV) domain. The LDO regulator has fast dynamic response. However, an additional low supply voltage $(\mathrm{V}_{\text{INL}})$ is needed to allow a very low dropout voltage for enhancing the LDO regulator efficiency and to have a small pass transistor with low gate oxide capacitance to achieve high bandwidth. Yet, the additional VINL adds cost and limits the VCR range and loading capability.