Browse Publications Technical Papers 2001-01-2717

Development of a Software Based “Virtual Fuse” For Use in Electronic Control of Electrical Loads 2001-01-2717

The increased use of power field-effect transistors instead of power relays for controlling electrical loads on vehicles has created an opportunity for the development of a software based virtual fuse. This development has several important aspects to the vehicle OEM. Not only will the cost of the fuse be saved along with the cost of the fuse holder, but also perhaps the largest cost associated with using a traditional fuse: the wiring to and from the fuse.
In commercial vehicles, the variability of one vehicle to the next may force different circuits to occupy the same physical space on the different vehicles. These differing circuits may also require different values of fuse elements. Ensuring that the correct fuse value is installed under these conditions can be a difficult task at best. Having a software based virtual fuse that can be programmed to match the vehicle configuration can eliminate having an unprotected circuit due to an assembly error.
The development of a software based virtual fuse must be well executed. The end result is far too risky to allow assumptions and/or errors to creep into the development. The goals must be clearly defined and testing of the final product must be thorough and brutal.
Before beginning the development of a software based virtual fuse, the facts regarding conventional wiring and fuses should be gathered. The only facts that this author uncovered that were pertinent to the development were:
  1. 1)
    Fuses have protected vehicle circuits for many years.
  2. 2)
    The Society of Automotive Engineers has published testing recommendations for the performance of circuit protection devices.
These two facts, not assumptions or opinions, should guide the development of a software based virtual fuse for use in electronic control of electrical loads.


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