Power supply unit with connector protection circuit

A power supply unit having improved resistance to overheating caused by electrically conductive environmental contamination of electrical contacts of a connector of the power supply unit is disclosed. In one example, the connector includes one or more electrical contacts configured to receive one or more signals that indicate the connector is connected to an electronic device. The power supply unit includes a protection circuit that is configured to electrically disconnect the power supply unit from the connector based on detecting that a voltage on at least one of the one or more electrical contacts is greater than an expected/reference voltage. The higher than expected voltage may indicate that electrically conductive contamination has created a short between different electrical contacts of the connector. The power supply unit may be disabled based on detection of the electrically conductive contamination in order to prevent overheating and/or degradation of the connector.