Bus pre-charge control using a buck converter

A vehicle is disclosed having a traction battery and an electrical impedance connected by a contactor. A pre-charge circuit is disclosed that controls current flow from the traction battery through the pre-charge circuit to the electrical impedance to increase voltage at the electrical impedance such that as the voltage approaches a voltage of the traction battery, a duty cycle of the pre-charge circuit approaches a maximum value and a current through the pre-charge circuit approaches a minimum value. In response to current falling below a predetermined value, the contactor is closed. A current sensor is disclosed that is located in the pre-charge circuit. A method of operating the pre-charge circuit is disclosed.