As the core unit for energy replenishment in new energy vehicles, the operation of an on-board charger is fundamentally a systems engineering feat combining high-power-density power electronics conversion with precise control. Within its compact metal housing, high-frequency switching devices operate at speeds ranging from tens to hundreds of kHz, converting grid AC power into the DC power required by the battery. This process not only generates strong electromagnetic fields but also, due to the rapid changes in voltage and current (dv/dt, di/dt), excites broadband spectral noise extending from the switching fundamental frequency up to tens of MHz. If left unmitigated, this noise poses multiple risks: on one hand, harmonics conducted back to the grid can interfere with other equipment on the same power network, even triggering power quality issues; on the other hand, noise may couple into the low-voltage control circuits within the charger, leading to distorted current/voltage sampling, disrupted PWM modulation, and—in mild cases—reduced charging efficiency and prolonged charging times, or in severe cases—false protection triggering, damage to the Battery Management System (BMS), or power module failure, directly threatening charging safety. In this complex electromagnetic environment, feedthrough capacitors have emerged as key components ensuring the efficient, safe, and stable operation of on-board chargers, thanks to their exceptional high-frequency noise suppression capabilities and reliable mechanical structure.
The unique value of feedthrough capacitors stems from their “through-type” physical design. Unlike ordinary capacitors, their current path vertically penetrates the capacitor dielectric, completely avoiding the parasitic inductance introduced by leads or pads. This allows high-frequency noise to be channeled into the grounding plane via the shortest path. This characteristic enables them to maintain extremely low impedance even when dealing with MHz-level high-frequency interference, making them an ideal “pressure relief valve” for noise.
The installation process of feedthrough capacitors plays a decisive role in their performance. In high-vibration, high-reliability scenarios such as on-board chargers, the metal housing of the capacitor must be continuously welded around its entire 360° perimeter to the charger’s metal shielding shell or a dedicated grounding busbar. This technique ensures a contact resistance of less than 10 milliohms, establishing a true “high-frequency equipotential body” that allows interference noise to be seamlessly directed into the vehicle ground. Simultaneously, the fully sealed welded structure provides excellent resistance to dust, moisture, and salt spray corrosion, making it suitable for harsh installation environments such as the engine compartment or chassis.
Faced with the electromagnetic challenges of on-board chargers, the performance, power density, and reliability requirements for feedthrough capacitors continue to rise. Though deeply embedded within the charger, they act like silent guardians, leveraging precise electromagnetic purification capabilities to ensure that every unit of electrical energy is efficiently and safely delivered to the battery, safeguarding every journey of new energy vehicles.
