As vehicle electronic content proliferates, electronic component quality and reliability must improve to maximize vehicle performance and reduce warranty issues. While component quality and reliability were always important, the new trend towards hybrid (HEV/PHEV) vehicles and battery-powered electric vehicles (BPEV) adds a new dimension.
Older gas power vehicles had only a minimum of electronics - an electronic component failure may have stopped the radio from working but not prevent anyone from getting home ok. Simple engine control functions where added, to improve engine efficiency and fuel economy. This created the need for quality and reliable components as a single component failure could stop the engine from functioning.
Today, with vehicles that are almost completely controlled by electronics, drivers can face different kinds of reliability risks. Typical, the electronics begin their work when a driver walks up to the car and the passive entry system unlocks it. The interrogator pings the key to allow you to start the car with a press of a button. Numerous power supply, analog and microcontrollers circuits start up and control your engine, transmission and almost everything else in the vehicle. Then there are additional feature systems to power, including navigation, anti-lock brakes, cruise control radars, infotainment electronics, etc, etc.
Reliability standards (ISO/TS16949) in the harsh automotive environment are vital because the average car today requires an electrical power processing capability of 250 to 1,500W, a number that is increasing rapidly due to the high power electrical system required in vehicles for powering the car or truck, and also for entertainment and efficiency. Because a vehicle battery is a relatively unregulated low voltage source, it requires a regulated high voltage DC-DC system, which in most cases means a boost DC-DC converter using a multiphase boost architecture.
As an example, consider the simple starting and stopping functions. In the automotive environment, a start/stop system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby improving the fuel economy. This is most advantageous for vehicles that spend significant amounts of time in traffic jams, requiring frequent start and stop. During the starting period, the battery undergoes what is known as voltage cranking deep, which can be as low as 6V. In order to protect all the electronics connected to the battery bus, the bus line voltage has to be protected from seeing the battery-cranking transient.
One method to solve this issue is by having a regulated multiphase boost DC-DC converter temporally connected between the battery and voltage bus in order to overcome the dip when a cranking transient happens. In this configuration, when the battery voltage is below an 11.5V threshold, the battery voltage will be boosted by the multiphase boost DC-DC to provide a stable bus voltage.
For the complete article, which describes the circuitry involved with the start/stop system, infotainment power electronics protection, and how the multiphase boost converter works onr hybrid, electric, and fuel cell vehicles, click here, courtesy of Automotive Designline Europe.
If everything stays at 12V, just a boost is not good enough as there is also a load dump situation when the input voltage can fly up as high as 100V (with TVS clamp it can also be around 40-60V) so a 12V system indeed is not a 12V system. So I don't think a boost converter boosting the input o 12V or 24V (for audio as mentioned in the article) helps. Fortunately, most electronics run at much lower voltage (3.3V, 5V etc.) so there is a high voltage buck after the so-called 12V rail. However, if a real robust 12V is needed, people have to consider the buck-boost or SEPIC design.
Not sure what you mean by "main battery". I believe this article is addressing simple, stop-start only, micro-hybrid vehicles (not mild or full hybrid vehicles which have a secondary high voltage battery). These micro-hybrid vehicles typically use a single 12V lead-acid battery, often an AGM for better cycle life. They are prone to voltage sag during starting since the starter (either an enhanced cranking motor or a Belted-Alternator-Starter or an Integrated Starter Generator) rely on the 12V battery for cranking energy.
Mild or full hybrids with a secondary high voltage battery all use the high voltage battery for re-starting and therefore do not have the voltage sag problem during re-starts.
Certainly a bigger battery would help, but it is a trade-off between a bigger battery and a DC-DC boost converter. The bigger battery will still have voltage sag during cranking which may be noticed by the customer in the form of dimming lights, slower blower speeds, etc.
The big difference here is that during a normal start the electrical accessories are (intentionally) turned off. During stop-start the accessories are still active and one of the goals is to make the stop-start function as transparent to the customer as possible.
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