System and methods may calibrate an AC rms voltage applied to a coronode of a charging device to achieve a predefined operating current at a target value of DC shield voltage. The target value of DC shield voltage may be set to be substantially below an over-voltage condition. System and methods may use a calibration routine that may determine a minimum AC voltage required to achieve the target value of DC shield voltage. Systems and methods may alternatively, or additionally, sense current and adjust the applied voltage to obtain a target current.