TDK has introduced two new aluminum electrolytic DC link capacitor series, B43655 and B43656, targeted at on‑board chargers (OBCs) in electric vehicles.
These DC link snap‑in capacitors address the trend toward higher battery voltages and higher charging currents while maintaining compact size and long life in forced‑cooling environments. Their combination of high CV product, high ripple capability and AEC‑Q200 qualification makes them relevant for both design engineers and sourcing teams working on next‑generation EV platforms.
Key features and benefits
The B43655 aluminum capacitors series is designed for 800 V battery architectures, with rated voltages up to 475 V and 500 V and capacitance values from 110 µF to 880 µF, making it suitable as the main DC link energy buffer in modern high‑voltage OBC designs. At the same time, the B43656 series is rated at 450 V and optimized for even higher ripple currents up to 4.42 A at 105 °C, targeting high‑power topologies that stress the DC link with significant AC content.
Key features of B43655 and B43656 include:
- Extremely high CV product with ultra‑compact snap‑in can sizes, allowing designers to minimize board footprint and mechanical height in the OBC power stage.
- High ripple current capability (up to 3.29 A for B43655 and 4.42 A for B43656 at 120 Hz, 105 °C) supporting higher charging power without excessive self‑heating.
- ESR values down to 100 mΩ (typical at 120 Hz, 20 °C) to reduce conduction losses and improve overall OBC efficiency.
- Design optimized for base cooling and high ripple current density, which fits forced‑air or cold‑plate concepts in automotive chargers.
- Useful life of more than 3,000 hours at 105 °C, supporting demanding thermal profiles in compact EV power electronics.
- Available types with tight length tolerance (±0.5 mm), which simplifies mechanical integration, heatsink contact and automated assembly tooling in series production.
- Integrated pressure relief device on the case wall, contributing to controlled failure behavior under severe overload conditions.
- RoHS‑compliant construction and qualification according to AEC‑Q200 Rev. E, which reduces risk for automotive qualification and sourcing approval.
In practical terms, the low ESR and high ripple ratings help keep capacitor temperature rise under control at high charging power, which is often a limiting factor in compact OBC designs. The dimensional options and tolerance control support platform reuse across several vehicle variants without major mechanical redesign.
Typical applications
The primary target application for these series is the DC link of on‑board chargers in battery electric vehicles. In this role, the capacitors smooth the rectified AC line, provide energy buffering for high‑frequency switching stages, and stabilize the DC bus seen by downstream converter stages.
Typical use cases include:
- DC link capacitors directly after the PFC stage in single‑ or three‑phase OBC topologies in EVs with 400 V and 800 V battery systems, depending on series selection.
- Energy buffering at the DC bus of high‑frequency LLC or phase‑shifted full‑bridge stages within the charger.
- Use in forced‑cooled automotive power modules where base‑cooling concepts are already implemented, such as integrated OBC plus DC/DC units.
- Potential suitability for other automotive DC link functions that require AEC‑Q200 qualified aluminum electrolytics with high ripple capability, according to the manufacturer’s datasheet.
Because the parts are AEC‑Q200 qualified and designed for base cooling, they are particularly attractive where the capacitor bank sits close to heatsinks or power modules and shares the vehicle’s thermal management system.
Technical highlights
From a component selection perspective, the most relevant electrical parameters of the new series can be summarized as follows. Values are typical ranges; exact ratings are according to the manufacturer datasheet.
- B43655 series
- Rated voltage: 475 V and 500 V DC.
- Capacitance range: 110 µF to 880 µF.
- Typical ESR range: 100 mΩ to 800 mΩ at 120 Hz, 20 °C.
- Ripple current (IAC,R): approximately 0.76 A to 3.29 A at 120 Hz, 105 °C.
- Designed explicitly to meet 800 V battery architecture requirements in e‑mobility OBCs.
- B43656 series
- Rated voltage: 450 V DC.
- Capacitance range: 120 µF to 820 µF.
- Typical ESR range: 120 mΩ to 830 mΩ at 120 Hz, 20 °C.
- Ripple current (IAC,R): approximately 1.08 A to 4.42 A at 120 Hz, 105 °C.
- Mechanical and qualification data (both series)
- Case style: snap‑in aluminum electrolytic capacitors with diameters from 22 mm to 35 mm and lengths from 25 mm to 60 mm (depending on rating).
- Several variants with tight length tolerance ±0.5 mm, easing mechanical stack‑up in compact charger enclosures.
- AEC‑Q200 Rev. E qualification and RoHS‑compatible materials.
In practice, the combination of high rated voltage and compact can sizes enables designers to hit required DC link capacitance with fewer cans, reducing assembly complexity and cost. The specified useful life at 105 °C is a key design‑in parameter for meeting automotive lifetime targets, especially when combined with the manufacturer’s lifetime calculation tools.
Design‑in notes for engineers
When designing DC link stages in EV on‑board chargers, the key trade‑offs are often between capacitance, ripple current capability, ESR and mechanical constraints. The B43655 and B43656 series are optimized for forced‑cooling and base‑cooled setups, so the thermal path from capacitor base to heatsink should be considered early in mechanical design.
Practical design‑in hints:
- Series selection
- For 800 V battery systems and DC bus voltages approaching this range, B43655 (475 V / 500 V) is the natural choice to maintain adequate voltage derating.
- For lower DC bus voltages or where even higher ripple currents are required, B43656 (450 V) can be attractive thanks to its higher ripple ratings.
- Ripple and ESR considerations
- Use the specified ESR and ripple current data at 105 °C to estimate self‑heating, and combine this with the manufacturer’s AlCap Useful Life Calculation Tool to check lifetime under real operating conditions.
- Because these capacitors have relatively low ESR, they help limit bus voltage ripple and loss, but layout (bus bar or bus PCB) remains critical to overall loop impedance.
- Thermal management
- The parts are optimized for base cooling and high ripple current density, so achieving good thermal contact at the base can significantly extend useful life compared with purely free‑air cooled mounting.
- Forced air or liquid‑cooled cold plates should be evaluated together with capacitor placement, especially in compact OBC housings.
- Mechanical and tolerance aspects
- The availability of types with ±0.5 mm length tolerance is useful when multiple capacitors are mounted in tight mechanical frames or clamped arrangements, reducing mechanical stress distribution issues.
- The pressure relief device on the case wall is a safety‑relevant feature; ensure that mechanical design does not block or constrain this area.
- Standards and qualification
- AEC‑Q200 Rev. E qualification is advantageous for EV platforms where many subsystems must comply with automotive component standards; this can reduce validation effort at OEM and Tier‑1 level.
- RoHS‑compliance is important for global deployments and regulatory conformity.
For detailed electrical curves (impedance versus frequency, ripple current derating versus temperature, lifetime curves), engineers should consult the official datasheets and use them in conjunction with the AlCap tool.
Source
This article is based on information from an official TDK Corporation press release on the B43655 and B43656 aluminum electrolytic DC link capacitor series for electric vehicle on‑board chargers, complemented with general application context for power electronics design engineers.