An Electrical Variable Capacitor Circuit Utilizing a Floating Diode for Fast Impedance Matching

Recently, there has been growing interest in electrical variable capacitor (EVC) circuits for fast impedance matching applicable to advanced semiconductor fabrication processes. However, the conventional EVC circuit suffers from the need for a large filter inductor L_f, which hinders fast capacitance adjustment. To address these limitations, a new EVC circuit is proposed. The proposed EVC circuit allows the use of a smaller L_f by swapping the positions of the switching diode D_SW and the variable capacitor C_var compared with the conventional EVC circuit, and by adding a shunt inductor L_S. With a smaller L_f, the proposed EVC circuit achieves much faster capacitance adjustment, while also reducing the cost and volume of the circuit. To validate the feasibility of the proposed EVC circuit, a 1.4 kW prototype was tested.