1. Mechanism of electromagnetic interference generation in car chargers
During the operation of car chargers, electromagnetic interference mainly comes from the switching power supply circuit inside the car charger. When the switch tube is turned on and off at high speed, it will generate rapidly changing current and voltage, thus forming an alternating electromagnetic field, radiating electromagnetic waves to the surrounding space, which is radiation interference. At the same time, due to the energy storage components such as inductance and capacitance in the circuit and the parasitic parameters of the line, conducted interference will be generated in the circuit and propagated along the power line and other connecting lines. For example, under high-frequency switching action, oscillation will occur between the leakage inductance of the transformer and the parasitic capacitance of the switch tube, generating high-frequency noise signals, which will be coupled to other parts through the circuit network, interfering with the normal operation of other electronic equipment in the car, such as affecting the signal reception of the car radio, resulting in noise or signal interruption, and may also have a potential impact on the control system of the car, threatening driving safety.
2. Impact of electromagnetic interference on vehicle electronic systems
Electromagnetic interference may have serious impacts on vehicle electronic systems in many aspects. For vehicle-mounted communication devices, such as Bluetooth modules and vehicle-mounted Wi-Fi, electromagnetic interference may cause communication interruption, data transmission errors or reduced rates, affecting the information interaction between the vehicle and external devices and the normal use of the in-vehicle entertainment system. In terms of automobile safety control systems, such as anti-lock braking systems (ABS) and electronic stability programs (ESP), if they are subject to electromagnetic interference, they may malfunction or respond late, greatly reducing the safety of the vehicle. In addition, there will be interference with the vehicle instrument display system, causing inaccurate or flickering display data, interfering with the driver's accurate judgment of the vehicle status.
3. Methods for suppressing electromagnetic interference-circuit design level
In circuit design, a variety of methods can be used to suppress electromagnetic interference. First, add an EMI filter to the switching power supply circuit, and filter the conducted interference through a combination of inductors and capacitors to prevent high-frequency noise from propagating on the power line. For example, common-mode inductors can suppress common-mode noise, and differential-mode capacitors can filter differential-mode interference. Secondly, optimize the driving circuit of the switch tube, reasonably set the switching speed of the switch tube, and avoid excessively high peak voltages and currents caused by excessively fast switching actions, thereby reducing electromagnetic radiation. A buffer circuit can also be used to absorb the overvoltage and overcurrent generated when the switch tube is turned off, reducing the oscillation and electromagnetic radiation of the circuit. In addition, it is also an important design method to reasonably layout the circuit board, separate the power circuit from the control circuit, reduce electromagnetic coupling, and shield sensitive components.
4. Methods for suppressing electromagnetic interference-shielding and grounding level
Shielding technology is crucial to suppress the electromagnetic interference of car chargers. The use of metal materials for the shell of the car charger and ensuring good shielding integrity can effectively block the internal electromagnetic radiation from leaking outward, and also prevent external electromagnetic interference from entering the charger. In terms of grounding, a reliable grounding system is established so that the metal shell of the charger and the grounding terminal in the circuit are well connected to the grounding point of the car body, providing a low-impedance discharge path for electromagnetic interference. In this way, the conducted interference current can be introduced into the earth, reducing its propagation in the circuit and its impact on other equipment. At the same time, attention should be paid to the length and cross-sectional area of the grounding wire to ensure the effectiveness and stability of the grounding, thereby comprehensively improving the electromagnetic compatibility of the car charger and ensuring the stable and reliable operation of the automotive electronic system.
