Electric vehicles are definitely one of the most complex network electronic systems today, with physical interconnections becoming highly complex. This vast network connects numerous new security devices and sensors to each other, and is connected to new higher-level control layers.

For bidirectional communication, automotive network architecture has introduced automotive Ethernet, and for unidirectional communication, LVDS has also been introduced. LVDS, Low Voltage Differential Signal, is a low-power, low bit error rate, low crosstalk, and low radiation differential signal transmission technology that can achieve high transmission rates and suppress EMI as much as possible. It is commonly used in systems such as car mounted cameras. In LVDS transmission, in order to reduce the weight of the wiring harness, PoC (coaxial cable power supply) technology, which uses a coaxial cable to achieve signal transmission and power supply, is widely used.

PoC and LVDS
Simultaneously supplying DC power and transmitting AC signals on a single cable is a power supply scheme used by many car mounted camera modules and other similar remote devices, known as PoC coaxial cable power supply. It utilizes power superposition technology to simultaneously process DC power supply and AC signals through a coaxial cable without interfering with each other.
PoC is a single line transmission method that only uses a two core coaxial cable architecture, which is relatively simple. However, PoC requires single end long-distance transmission of high-frequency analog video signals, and the technical difficulty is significant.

Especially in systems such as car mounted cameras that transmit signals through LVDS, the number of car mounted interfaces continues to increase, and the required data capacity continues to expand, requiring higher transmission rates and higher transmission power. LVDS PoC continuously improves transmission speed and power to meet the transmission needs of more sensors.

In PoC applications, the problem of signal interference on power lines is already quite serious and needs to be solved through appropriate EMC filtering. In LVDS PoC, the speed is faster and the frequency is higher, and the interference encountered will be more severe. At this point, inductance will play an important role in the circuit, improving signal quality and power supply efficiency.

For the communication signal path, the AC signal in coaxial cables is generally in a high-frequency state. At this time, the higher the impedance of the inductor, the better, which can prevent the loss of high-frequency signal in this link and cause signal attenuation, seriously affecting communication quality. At the DC end, it is necessary to minimize the internal resistance of the inductor and the cable, in order to reduce the loss of DC power supply and improve power supply efficiency.

Application of Inductance in LVDS PoC

With the rapid development of in car interfaces, the usage of in car high-speed interfaces is also constantly increasing in the entire vehicle. In systems such as in car cameras that transmit signals through LVDS, PoC coaxial cable power supply technology plays an important role. In order to solve various interference problems in PoC transmission, isolate wideband signals and power sources, and ensure high impedance in wideband, the application of inductors is crucial.

Specifically, when it comes to inductance performance, it is necessary to first have a wide frequency band and high impedance. Secondly, with the upgrading of transmission requirements in the vehicle, high current capability is also necessary. While meeting these performance requirements, it is necessary to minimize the size as much as possible, otherwise it will affect the DC internal resistance. A large DC internal resistance will increase the loss of DC power supply and reduce power supply efficiency.

Broadband and high impedance are the two most basic requirements, and the common second-order and third-order filtering schemes on the market are also aimed at building high impedance schemes with sufficient bandwidth. These performance mainly depends on the optimization of coil structure design and material preparation. A dedicated PoC filtering inductor will avoid the expansion of parasitic capacitance on the coil structure, thereby obtaining a larger resonant frequency and filtering bandwidth.

The higher the impedance of the inductor, the better it is to prevent the loss of high-frequency signals at this stage, which can lead to signal attenuation and effectively prevent high-speed signals from being affected and interfering with communication quality.

At the same time, high current capability is also an indispensable capability applied in vehicle systems. There must be a sufficiently high saturation current to support the current passing through full load, in order to reduce impedance changes in current applications and improve the performance of the entire PoC system.
Smaller dimensions are also more friendly to the limited space of in car sensor modules, and the lightweight development of in car devices requires PoC systems to be implemented with fewer components and smaller dimensions.

The performance of in vehicle networks has been significantly improved with the support of PoC technology, and the demand for higher passive components behind PoC technology has also driven the iterative upgrading of devices.