Inductive wireless power transfer systems are provided for medical devices, such as implantable medical devices (IMDs). The systems may comprise a transmitter unit and a receiver unit and may be configured for transferring power and/or signals from the transmitter unit to the receiver unit and/or vice versa. The transmitter unit may comprise an energy source, a transmitter antenna, and a supply line connected in between the energy source and the antenna. The receiver unit may comprise a receiver antenna and a rectifier output. The transmitter antenna and the receiver antenna may be configured to provide a wireless power transfer link. The supply line may comprise a virtual resistance unit, which may be configured to provide a virtual resistance, which may be determined such that the rectifier output provides a substantially constant or less varying charge current over a predetermined distance range, for a large range of implant depths.
