Regulating the Output Voltage of the Resonant Switched-Capacitor Converters Below Their Resonant Frequencies

Resonant switched-capacitor converters have widely been used recently to increase conversion power density. The most significant drawback of these converters is voltage regulation problem when their input voltages vary in wide ranges. Here, a basic double voltage-ratio resonant switched-capacitor converter (SCC) is analyzed and simulated below its resonant frequency under the different operation modes to overcome this problem. The converter different parameters are calculated under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) conditions. The advantages and drawbacks of these operation modes are compared and the closed-loop control of the converter is also investigated based on the extended describing function approach. The given analyses demonstrate that the output voltage can be well-regulated under the CCM1 and DCM2 operation modes even when wide input voltage and load variations are applied. Besides, the DCM1 operation mode must be avoided when output voltage regulation is important. Based on the given analytical and experimental results, switching frequency varies in a reasonable range to regulate the output voltage. Also, faster transient responses, smaller output capacitor, and smaller resonant tank components can be used below the resonant frequency, as compared to the above resonant frequency, but lower efficiency value is achieved. The given approach has been extended to the other resonant SCCs as well.