Separate Operation Of Secondary 12 V On-Board Electrical System, Basic Function - GF54.10-P-1017A

Model all (CAR) with code 503 (Remote-controlled parking) 

Overview 

This document contains the following information:

• General 
• Normal mode 
• Separate operation 

General 

Driver assistance systems are taking over more and more of the driver's driving tasks with the aid of automated functions. This increases the demands on the electrical energy supply in terms of safety and availability. Single errors must not result in uncontrollable system failure. To achieve this objective, the regular 12 V on-board electrical system is extended to include a secondary 12 V on-board electrical system. Electrical components which are relevant for driving safety are connected in parallel to both networks. In normal operation, system-relevant consumers are supplied from the 12 V on-board electrical system. The secondary 12 V on-board electrical system is kept operational as a standby system.

If the 12 V on-board electrical system fails, system-relevant consumers are supplied via the secondary 12 V on-board electrical system. This is supplied from the secondary 12 V on-board electrical system battery. Thus, functions that are required e.g. for highly automated parking are maintained for a defined period of time. The vehicle can be secured either automatically or by means of a driver intervention.

Normal mode 

In normal operation, the secondary 12 V on-board electrical system's DC/DC converter establishes the connection between the 12 V on-board electrical system and the secondary 12 V on-board electrical system. It ensures that the charge of the secondary 12 V on-board electrical system battery is maintained. A current flow from the 12 V on-board electrical system to the secondary 12 V on-board electrical system is permitted, but a current flow in the other direction is blocked because the secondary 12 V on-board electrical system is kept at a higher voltage.

Separate operation 

If the following events occur, the DC/DC converter disconnects the connection between the 12 V on-board electrical system and the secondary 12 V on-board electrical system by means of an internal separator:

• The voltage at circuit 30t drops below a minimum value.
• A serious fault occurs in the 12 V on-board electrical system.
• Failure of the 12 V on-board electrical system.

During disconnected operation, the consumers in the secondary 12 V on-board electrical system continue to be supplied for approx. 1 minute.

	Control units
	Secondary 12 V on-board electrical system DC/DC converter control unit, basic function		GF54.10-P-2019A
	Components
	Secondary 12 V on-board electrical system battery, basic function		GF54.10-P-2020A