Method for regulating an operating current of a lighting unit and control device and motor vehicle

A method of controlling an operating current of a lighting unit by a control device, wherein the lighting unit is connected to a contact pair of the control device, the contact pair being formed of two electrical contacts, and the lighting unit has a light emitting diode arrangement that is operable via the contact pair, and the control device operates the light emitting diode arrangement by generating an operating current that flows via the contact pair, the method comprising:

• setting with the control device at least one parameter of the operating current depending on a diode type of the lighting unit;
• with the lighting unit switched off, generating a measurement current with the control device that flows through the lighting unit via the contact pair, and ascertaining a measurement value of a predetermined measurement variable that results on account of the measurement current, and identifying the diode type based on the measurement value thus ascertained;
• a) providing a hysteretic regulator for setting the at least one parameter of the operating current and during an operation of the lighting unit setting a reference signal at a comparator by way of a current source circuit, and using the current source circuit for generating the measurement current when the lighting unit is inactive;
• and/or
• b) using a precharge device of the control device to charge an output capacitance which is effective at the contact pair, the output capacitance being independent of the lighting unit that is actually connected and being part of the control device, by way of a predetermined precharge routine and ascertaining a deviation from a predetermined expected value as the measurement value.