Design of Switched-Capacitor AC-DC Voltage-Down Converters Driven by Highly Resistive Energy Transducers

This paper proposes switched-capacitor ACDC converters driven by highly resistive energy transducers. Unlike a previously reported input-voltage-tracking method, the number of capacitors (N) and on-time ($T_{1}$) are fixed with the certain values in the proposed design, which can be determined using optimum design theory for the DC-DC switched-capacitor voltage-down converter driven by a highly resistive DC energy transducer with a DC voltage amplitude as high as the RMS value of the amplitude of the AC voltage. This fixed method is suitable for low-power applications aiming to maximize output power. To prevent reverse current with the fixed method, a suspending circuit or a Schottky barrier diode is employed. Model equations, including the loss due to the bottom plate parasitic capacitance, reveal that the fixed operation requires 66% fewer switches and 66% fewer control signals, while achieves 60% higher output power compared to the tracking method. SPICE simulations and measurements validate the effectiveness of the proposed fixed method on the entire power efficiency.