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How to Design Automotive Power Architecture?

Views:50     Author:Site Editor     Publish Time: 2019-12-28      Origin:Site


What is the car jump starter? 


The car jump starter is a multifunctional portable mobile power supply developed for driver and business people. Its special function is to start the car when the car is out of power or other reasons can not start the car. At the same time, the car jump starter combines the functions of the air pump with the emergency power supply and outdoor lighting, which is one of the essential products for outdoor travel. However, do you know how to design a car jump starter? Actually, most car power architectures are designed to follow six basic principles. Do you know these principles?



Input voltage VIN range


A typical car battery voltage range is 9V to 16V. When the engine is off, the standard voltage of the car battery is 12V. When the engine is running, the battery voltage is around 14.4V. However, under different conditions, the transient voltage may also reach ±100V. The ISO7637-1 industry standard defines the range of voltage fluctuations in automotive batteries. In addition to ISO7637-1, there are some battery operating ranges and environments defined for gas engines. Most new specifications are proposed by different OEM, which do not necessarily follow industry standards. However, any new standard requires the system to have overvoltage and undervoltage protection.



Heat dissipation considerations


The heat dissipation needs to be designed according to the minimum efficiency of the DC-DC power converter. In applications where air circulation is poor or there is no air circulation, if the ambient temperature is high and the enclosure has a heat source, the equipment will heat up quickly. For example, most audio amplifiers need to be mounted on a heat sink and need to provide good airflow conditions to dissipate heat. In addition, the PCB material and certain copper areas help to improve heat transfer efficiency for optimum heat dissipation. If the heat sink is not used, the heat dissipation capability of the exposed pad on the package is limited to 2W to 3W. As the ambient temperature increases, the heat dissipation capacity is reduced significantly.


When the battery charger is converted to a low voltage of 3.3V and the power reaches 3W, a high-side switching converter is required, which can provide an output power of more than 30W. This is why automotive power supply manufacturers typically use switching power supply solutions to exclude traditional LDO-based architectures.



Static operating current IQ and shutdown current ISD


With the rapid increase in the number of electronic control units (ECU) in automobiles, the total current consumed from automotive batteries is also growing. Some ECU units remain active even when the engine is off and the battery is exhausted. In order to ensure that the static operating current IQ is within the controllable range, most OEM begin to limit the IQ of each ECU. For example, the EU request is 100μA/ECU. Most EU automotive standards dictate that the ECU's IQ is typically less than 100μA. Devices that are always active, such as CAN transceivers, real-time clocks, and microcontroller current losses are key considerations for ECUs and IQs, and adjustable power supply designs need to consider a minimum IQ budget.



Cost control


For products that are produced in large quantities, cost is an important factor to consider in the design. PCB type, heat dissipation capability, allowable package selection, and other design constraints are actually limited by the budget for a particular project. For example, the heat dissipation capability of the PCB can vary greatly with 4-layer FR4 or single-layer CM3.



Position


Structural design, board layout, noise sensitivity, interconnect issues with multilayer boards, and other layout limitations can limit the design of high-chip integrated power supplies. The use of point-of-load power to generate all the necessary power supplies can also result in high costs, and it is not ideal to have many components on a single chip. Power supply designers need to balance overall system performance, mechanical constraints, and cost based on specific project needs.



Electromagnetic radiation


The electric field that changes with time produces electromagnetic radiation. The intensity of the radiation depends on the frequency and amplitude of the field. The electromagnetic interference generated by one working circuit directly affects the other circuit. For example, interference from radio channels may cause airbag malfunctions. To avoid these negative effects, OEM manufacturers have set maximum electromagnetic radiation limits for ECU units.


The car emergency start power supply design concept is easy to operate, easy to carry, and can cope with various emergencies. If you are interested, follow us to learn more.



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