The electronic content of the automobile has been rising at a rate of about 6% per year to the point that currently the value of electronics is almost $2000 for the high-end luxury vehicle. Due to the replacement of mechanical components with electrical components and the desire to add more new and sophisticated electronics, the electronic content is expected to grow even more rapidly during the next decade and will approach 40% of the total cost of a high-end luxury vehicle.
Another way to look at this growth is to consider that in the mid 50s a wiring harness was a mere 75 meters in length. Today a high-end vehicle can have a wiring harness over two kilometers in length with a mass of 35 kg. In fact, in some of the newest vehicles, the wiring harness can have 5600 parts and over 200 different harnesses can be used in a particular car line due to variations in content.
As the electronic content has grown, so has the demand for on-board power. The demand for electrical energy has grown from roughly 500 watts in 1970 to about 2000 watts for the current model year vehicles. This rate of growth translates into an increase in power demand of about 100 watts per year for the past 5 years. It is expected that the rate of growth will increase 300% during the next decade. In fact, according to Upton Bowden, Technical Liaison Manager, Higher Voltage Vehicle Systems, Visteon Corp., the expected power requirements for vehicles in the next decade are expected to approach 10,000 watts (see Figure 1). This is the basic reason that the industry is considering a move from the 14 V to a 42 V electrical system. Because of Ohms Law, tripling the voltage while holding the power the same, the current is one third of what it would be at the lower voltage. For example, at a fixed power level of 10,000 watts, the current level at 14 V would be 714 amps but at 42 V it would be 238 amps.
The switch to a 42 V electrical system is an enabler that will allow engineers to add more "power hungry" devices to the automobile. Table 1 is a list of some of these new devices that are under consideration along with the power requirements of some present day systems. However to understand what is going to occur, it is important to look at the total electrical system in an automobile.
Myron Trenne, Vice President, Advanced Technology, Advanced Marketing, Yazaki North America, Inc. described the electrical network in an automobile as a 4-layer architecture as shown in Figure 2. The four layers are:
• Power distribution network
• Chassis network
• Body network
• Information and entertainment network.
Figure 3 shows the evolution of each of the four layers over the decades. The switch to the 42 V electrical system fits into layer one, the power distribution network. However as shown in the figures, the layers are interdependent and a change in one area has ramifications on the other three. The new electronic systems such as electric steering, fully-active suspension systems, and electric brakes can have an effect on not only the power distribution but also the chassis and body networks. The area that is beginning to see a lot of interest and activity is the information and entertainment network. High speed audio and video networks, which are under development, will be required before this layer begins to mature.
As noted in Figure 3, this fourth layer will be seeing more activity in 2005 and beyond. This fourth layer is also drawing interest from suppliers outside the normal automotive arena such as Intel, Microsoft, and the like. This is the area where the high speed data transfer audio and video connections will bring a new era of audio and video possibilities into the automobile.
