Preface

With the upgrade of new energy vehicle high-voltage platforms from 800V to even 1500V, electrical compatibility failures of onboard Class B high-voltage components (DC 60V~1500V, including battery packs, OBC, DC/DC converters, electric drive compressors, etc.) have become frequent. Issues such as BMS misjudgment triggering contactor power-off during driving, electric drive controllers reducing output power due to ripple interference, and high-voltage component load dump surges damaging power chips directly threaten driving safety.

ISO 21498-2 is the global mandatory electrical test standard for new energy high-voltage components. It clearly specifies emission and immunity test requirements for high-voltage DC system voltage fluctuations, ripple, load dump, and slew rate variations, making it a core requirement that must be met during the component R&D phase.

This article combines measured data from high-voltage power characteristic test systems to deconstruct the interference mechanisms of ISO 21498-2 clauses. Targeting the test failure points that component R&D engineers frequently encounter, and leveraging Leiditech's high-voltage TVS, ESD, and high-power surge protection components, it provides standardized hardware protection design approaches to solve the EMC electrical compatibility failure issues of high-voltage components.

I.The underlying mechanisms of electromagnetic interference and ripple-induced failures in new energy high-voltage components

1.1 Core interference sources in high-voltage systems

Compared to the traditional 12V low-voltage architecture of conventional fuel vehicles, the high-voltage circuits of new energy vehicles contain multiple strong interference sources, which are also key control targets of ISO 21498-2:

l Electric drive inverter: The periodic switching action of IGBTs is the largest source of ripple voltage in the entire vehicle. During sudden power increases such as acceleration and climbing, a broadband ripple (10Hz~150kHz) is superimposed on the high-voltage bus.

l Onboard DC/DC and OBC power converters: High-frequency power transistor switching causes voltage spikes and current pulses.

l Vehicle high-voltage bus: All high-voltage components are connected in series, forming an interference coupling channel. Interference generated by the inverter and charger is simultaneously conducted to the battery management system (BMS).

1.2 The critical hazards of ripple on high-voltage components

电流和电压与转速和扭矩的关系

（图上方显示了运行过程中转速和扭矩的变化。底部两条曲线显示记录的电压和电流。可以看出两者都不是平滑或恒定的，而是由电力驱动系统的逆变器部分引起的纹波叠加的）

Ripple is an AC interference signal superimposed on DC high voltage, and is a core test item of ISO 21498-2 clauses 6.5 and 6.6. Measured waveforms show that the high-voltage bus voltage is not a constant smooth DC, but continuously superimposed with high and low frequency ripple from the inverter output.

Component-side failure logic: The BMS sampling frequency is approximately 30kHz. If the ripple amplitude and frequency on the bus exceed limits, it causes BMS voltage and current sampling distortion, leading to false overvoltage/undervoltage battery fault detection, which directly triggers the HV contactor to open, resulting in loss of power during vehicle operation. Meanwhile, the main control chips and sampling op-amps inside the DC/DC and OBC are affected by ripple-coupled interference, causing unstable output, communication errors, and overheating damage to power devices.

The high-voltage battery pack impedance characteristics further amplify the risk: a 400V battery has an internal resistance of only 20~50mΩ, and an 800V platform has an internal resistance of 50~100mΩ. In such low-impedance paths, even small ripple currents can generate large ripple voltages, imposing extremely high immunity requirements on high-voltage components.

1.3 Load dump, voltage slope, overvoltage, undervoltage, and other transient surge risks

ISO 21498-2 clauses 6.3/6.4 voltage slope, 6.7/6.8 overvoltage/undervoltage, and 6.10/6.11 load dump provisions, targeting transient voltage shocks in high-voltage circuits: when the vehicle's high-voltage contactor disconnects, load suddenly changes, or during rapid acceleration/deceleration, the bus generates thousands of volts of instantaneous voltage spikes and rapid voltage rise/fall slopes. Without effective protection, high-voltage MOSFETs, main control chips, and sampling circuits are highly susceptible to ESD breakdown and dielectric breakdown, leading to batch component failures.

II.ISO 21498-2:2024 Standard Core Test Clauses Breakdown

ISO 21498-2 applies to all high-voltage components in the DC 60V~1500V range. It is divided into two categories: emission tests (interference generated by the component itself) and immunity tests (component tolerance to external grid interference). All test items can be reproduced using a combination system of a bidirectional programmable high-voltage DC power supply, ripple generator, and high-voltage artificial network (HV-AN). These are mandatory verification items for component R&D.

2.1 Voltage variation tests (6.2 / 6.7 / 6.8 / 6.9)

6.2 Working range voltage variation immunity: Simulates the slow rise/fall of bus voltage caused by battery SOC fluctuations during driving, verifying that the component operates stably across four voltage levels: OS1 normal, OS2 degraded performance, OS3 protection, and OS4 shutdown.

6.7 Overvoltage / 6.8 Undervoltage immunity: Simulates battery balancing, full charge, and low charge conditions by applying sustained overvoltage/undervoltage, requiring that the component does not fail and can resume normal operation after voltage recovery.

6.9 Voltage offset: Applies a static DC offset voltage to test the reference stability of the sampling circuit.

  R&D pain points: Insufficient voltage margin in high-voltage sampling chips and op-amps; the HV/LV isolation boundary is susceptible to breakdown from offset voltage; conventional low-voltage TVS cannot withstand sustained DC bias of hundreds of volts.

2.2 Voltage slope emission & immunity (6.3/6.4)

6.3 Emission test: During full-load operation, the voltage rise/fall slope generated by sudden power changes must not exceed the limit, to avoid interfering with other components on the same bus.

6.4 Immunity test: Externally applies a fast voltage transient up to 5000V/ms, simulating contactor switching shocks.

Failure scenario: Rapid voltage changes in the power loop generate coupled electric fields, interfering with the low-voltage control area on the PCB, causing CAN/LIN communication interruption and main controller MCU lock-up.

2.3 Ripple emission and ripple immunity (6.5/6.6, the most frequent failure item for components)

l 6.5 Emission: The bus ripple amplitude generated by the component during operation must meet the limit to prevent contamination of the vehicle's high-voltage power network.

l 6.6 Immunity: External superposition of broadband ripple from 10Hz to 300kHz (up to 140Vp ripple amplitude) is applied, and the component must operate without any functional anomalies throughout the test.

The test system uses a 10kW high-power ripple generator + 1000A coupling transformer to reproduce extreme vehicle ripple conditions. In current 800V platform component testing, nearly 60% of initial prototypes require rework due to failing ripple immunity.

2.4 Load dump emission & immunity (6.10/6.11)

Simulates the sudden disconnection of a load in the high-voltage circuit, causing a large reverse load dump spike on the bus, which is the number one cause of power device breakdown. The standard requires that under full-load load dump conditions, the component's internal devices suffer no irreversible damage and functionality can be restored. Additionally, the VW 80300 EHV series adds pulse tests with superimposed narrow-pulse high-voltage shocks, further increasing the protection challenge.

III.Design challenges of interference protection for high-voltage components

Combining the test conditions of ISO 21498-2, there are three major industry pain points in circuit protection for components:

· Sustained DC high-voltage bias: The 400V/800V bus operates under continuous DC voltage. Common low-voltage ESD and TVS devices suffer from high leakage current, are prone to thermal failure, and lack sufficient reverse voltage withstand capability.

· Broadband ripple: Continuous AC ripple from 10Hz to 300kHz requires protection devices to balance high-frequency response with high power dissipation.

· Multiple transient superposition: Ripple, load dump spikes, and voltage slope impacts occur simultaneously. A single protection component cannot handle steady-state DC, AC ripple, and transient high-voltage pulses all at once.

Traditional solutions relying solely on large decoupling capacitors can only slightly suppress low-frequency ripple, but have no effect on high-frequency spikes or narrow-pulse load dump events, and therefore cannot pass the stringent ISO 21498-2 tests.

IV.Leiditech high-voltage protection components and supporting solutions for ISO 21498-2

Leiditech, with deep expertise in high-voltage TVS, automotive ESD, and high-power surge suppression components, provides a layered protection architecture for four major high-voltage components — battery pack BMS, OBC, DC/DC converter, and electric drive controller — matching all ISO 21498-2 test items and covering the entire circuit from high-voltage power bus to low-voltage sampling and communication interfaces.

4.1 High-voltage DC bus main circuit protection (400V/800V platforms, for ripple, load dump, and overvoltage)

ISO 21498-2 6.6 and 6.11 test core protection locations: High-voltage bus HV+/HV- input terminals, using high-voltage high-power TVS solutions:

l Component selection: Leiditech's high-voltage automotive TVS series covers reverse breakdown voltages from 60V to 1200V, capable of withstanding 10kW-level transient pulses, with low leakage current (<1μA) suitable for long-term DC high-voltage operation, ensuring no heating from capacitor parallel leakage current.

l Function: Suppresses instantaneous spikes of thousands of volts, clamps bus voltage to a safe range. Used in conjunction with decoupling capacitors to filter out low-frequency ripple, significantly reducing the amplitude of high-frequency interference injected by the ripple generator, easily passing the 6.6 ripple immunity test.

l Layout: Place TVS as close as possible to the high-voltage input terminals, shorten trace inductance, and prevent high-frequency ripple reflection amplification.

4.2 Low-voltage sampling / op-amp loop protection (for voltage offset and slope-coupled interference)

BMS low-voltage sampling and high-side isolation op-amps are highly susceptible to voltage slope and offset voltage interference. Use Leiditech automotive-grade bidirectional TVS to eliminate sampling zero drift caused by positive and negative voltage offsets, suppress induced interference coupled from fast voltage slopes to the low-voltage sampling end, and meet the voltage variation immunity requirements of 6.2 and 6.9.

4.3 Auxiliary protection for vehicle communication interfaces (CAN/LIN)

Leiditech uses the multi-channel integrated automotive-grade device SMC24Q for protection (targeting the Littelfuse AQ24CANA), with capacitance <50pF, ensuring signal integrity while passing ESD testing. The common-mode choke LDW43T-513T filters out common-mode interference. The solution meets IEC 61000-4-2 Level 4, achieving contact discharge of 30kV and air discharge of 30kV, and also meets the LV123 low-voltage compatibility requirements associated with ISO 21498-2.

4.4 VW80300 pulse supplementary test supporting protection

For the VW80300 EHV-10 and EHV-16 narrow-pulse high-voltage surge tests, pair with Leiditech high-power TVS to absorb 200V peak high-frequency pulses and prevent pulse interference from damaging the main control chip.

Conclusion

ISO 21498-2 is a hard threshold for market access of new energy high-voltage components. Ripple, load dump, and voltage transient shocks are the test items most prone to failure during the R&D phase. Passive filtering alone cannot meet the stringent emission and immunity requirements of the standard; dedicated high-voltage transient protection components must be used to build a complete EMC protection network.

Leiditech's automotive-grade high-voltage TVS and ESD full-series devices have been standardized and verified for 400V/800V high-voltage platforms, matching the hardware design of components such as battery packs, OBC, DC/DC converters, and electric drive controllers. They help R&D engineers simplify protection circuit design and pass the complete set of ISO 21498-2, LV123, and VW80300 high-voltage electrical compatibility tests in a single pass, shortening component development cycles and reducing later-stage rectification costs.