Advances in automotive technology have been amazing over recent decades. Electronics has entered the scene as an enabler of improved mileage and performance. Yet, as impressive as electronics integration has been, the future holds even greater promise.
Electronics use has a dual impact upon auto performance. The first is the ability to optimize performance in real time through precision control technology. It also offers the ability to help reduce weight considerably, thereby yielding significant miles per gallon (MPG) improvement. Though the exact MPG increase depends on the weight of the car, every 100 pounds of weight reduction will improve fuel efficiency approximately 2 percent.
Examples of common weight reductions resulting from electronics are multiplexed communication buses and electric power-assist steering, which also reduces belt loading on the engine, thereby offering additional MPG improvements.
Hybrid cars will demand a wide variety of electronic improvements, which will entail new requirements for capacitors. The extent to which capacitors will be challenged will correspond to the hybrid car type — e.g., plug-in hybrid, mild hybrid, etc.
Power capacitors will be required for decoupling the power source and the drive train. Although electrolytics are commonly used now, as voltages increase and failure mode considerations expand, film capacitors appear to be winning favor on next-generation higher voltage inverters and converters.
Supercapacitors are commonly used in regenerative braking schemes, but design trends have already pushed supercapacitors to higher power density for larger energy recovery schemes. A novel design trend is calling for smaller case size, smaller values with dramatically lower ESRs for use in “point of load” circuits within vehicles.
Safety capacitors are being required throughout hybrid vehicles on high voltage lines in large numbers. Safety capacitors typically utilize ceramic or film technology. High voltage snubber capacitors are being required to work at temperatures above 125°C. There is a growing need for high-voltage, high-temperature capacitors to evolve quickly to protect expensive IGBTs and other sensitive electronic components.
The typical trends of higher C/V and reliability will continue for automotive-grade small signal capacitors. Form factor will need to change as well, from traditional case sizes to filter configurations. Because of concerns over hybrid vehicle EMI emissions and susceptibility, automotive-grade versions of miniature SMT EMI filters have already been introduced to designers.
This is just a snapshot of major capacitive trends within the hybrid vehicle. External trends of charging, monitoring, and control all have their own set of significant requirements on other capacitor types.