Active Suspension Comes of Age Bolstered by High Density Power Modules

­Picture this. You are taking a trip to the city with some friends in your economy car, and you encounter an atrocious stretch of road. As you endure the bumpiest ride you have ever faced, you are passed by a sleek sedan, easily going twice your speed. ‘That can’t be comfortable’ you think to yourself, but then you notice something odd: The sedan is gliding across these horrific roads. The wheels are absorbing the hit, but the rest of the car is floating! With every bump and dip, the wheels seem to magically rise and fall matching every bump in the road, cruising along like a private jet. What is going on? How can it do that?

The secret is an active suspension system. It is considered a premium feature and is found in only about 10% of vehicles because of the power challenges it presents. In order to bring this technology to more vehicle platforms, OEMs need to design a lighter-weight, more affordable and efficient power system. The Vicor newly-unveiled power dense, automotive-grade power modules can help OEMs make this leap, solving a power problem that has plagued the industry for decades.

The challenge of active suspension systems

Active suspension systems require sophisticated software, sensors and electromechanical hardware that are instantaneously synched to deliver a premium riding experience. Each individual wheel of the car has a programmable element to it. This can be a hydraulic actuator, electric motor or even just an adjustable dampener – and these components are linked to a camera (or sensor) that tells the car what irregularities are approaching on the road ahead. This allows the vehicle to predictively adjust its suspension to the road’s contours, which stabilizes the ride quality. This technology isn’t new. It has been around for well over half a century – in the form of hydro pneumatics and was pioneered by Bose, the company best known for premium audio.

Bose installed an electromagnet-based active suspension system into a prototype vehicle in the 1990s. Known as Project Sound, the concept was used to demonstrate the capabilities of electromagnetic drivers in high-load applications – as similarly seen on the famous Maglev train. However, Project Sound also highlighted active suspension’s biggest flaw: power system complexity and weight.

Each wheel required an electromagnetic motor that weighed 200lbs! Carrying an extra 800 pounds plummeted fuel efficiency and dampened immediate viability. Additionally, the power requirements were far too demanding for a 12V battery to support.

Advancing active suspension with today’s electrified power designs

Fast forward to 2024, multiple OEMs have been able to mimic the Bose ride quality using alternative technology. All of these designs have managed to dramatically reduce electromagnetic weight, but weight still remains an issue – in the form of power delivery and power-conversion electronics.

While automakers may be able to fit the necessary power source for an active suspension in a car using 12V, most systems are still too heavy and impractical for broader adoption. For example, an internal combustion engine vehicle requires an additional large auxiliary battery and a DC-DC converter dedicated to powering active suspension, which adds almost 30lbs. This is too much weight. However, the equation changes when designing for an electrified vehicle where a large auxiliary battery is foundational to the vehicle power system and supports a variety of other loads.

A mild hybrid is an excellent example of an effective modern-day vehicle that leverages a 48V auxiliary battery to power a plethora of luxury electronics plus the active suspension. In this design 48V is run directly from the 48V battery to the active suspension system. The one drawback to larger vehicle systems design is that 12V is still the common bus. That leads to the need for additional DC-DC converters in the vehicle. Also, the active suspension power delivery network (PDN) weighs nearly 20kg and fills around 18L of space.

An alternative approach is 400V-battery based active suspension found in plug-in hybrid vehicles. Here, active suspension is linked directly to the car’s 400V battery, which, while efficient, requires the OEM to run heavy, expensive high voltage cables all around the car. Running 400V increases risk for maintenance and for first responders. While effective, it’s more likely that 48V-based active suspension systems will become the industry standard in the near-term – running from an 800V or 400V primary battery and DC-DC converter.

It should be noted, that one of the largest benefits of linking active suspension directly to the battery is energy recuperation. Similar to how a spring can absorb and expend energy, active suspension can absorb energy that be stored in the battery. While this can technically be done via a DC-DC converter, few manufacturers are able to design a system with a fast enough transient response, high slew rate, and power efficiency to manage bidirectional power flow between a device and its power source…cue Vicor. (Figure 1)

Power modules and 48V usher in the next generation of active suspension

New high-performance vehicles using power modules from Vicor feature the most advanced solution for powering active suspension. Not only are the Vicor DC-DC converters capable of matching the power and transient requirements to optimize energy recuperation, they also offer the highest power density in the industry enabling OEMs to save weight and space in the PDN design.

The Vicor BCM6135 is a 98% efficient 2.5kW isolated fixed-ratio BCM® bus converter, which converts 800V from the traction battery to 48V. (Figure 2.) Inherently bidirectional, its rapid current transient response rate of 8 million amps/second is a perfect match for the power profiles of active suspension in electrified vehicles. As fast as the system captures power, it can also respond rapidly to deliver power in fractions of a second and is uniquely able to process up to 2.5kW in either direction, maximizing energy recovery. With a high slew rate and unparalleled efficiency, the BCM6135 can achieve almost the same bidirectional power transmission as a direct cable, without relying on an auxiliary 48V battery or high-voltage cables. No other active suspension PDN is as efficient at power regeneration.

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Figure 2: Combining a BCM6135 with 48V delivers optimal performance and reduces size and weight of the active suspension power system as well as a 48V zonal architecture.  The BCM6135 is a 98% efficient 2.5kW isolated fixed-ratio BCM® bus converter, which converts 800V from the traction battery to 48V

With a power density of 158kW/L, the BCM6135 provides EV system designers a lightweight high-density primary DC-DC converter, further reducing vehicle weight using lighter cabling. The device can also be easily paralleled for higher power providing flexibility and scalability to the power system designer.

Innovating with 48V and scalable, power-dense new products

We are entering an age of advanced automotive electrification; where battery-powered vehicles combined with 48V zonal architectures provide new opportunities to innovate. Active suspension systems, which are found in only premium vehicles today, can become ubiquitous across fleets within a short time. Active suspension, like anti-lock brakes, will transition from an expensive luxury feature, to a standard feature as the industry electrifies their fleets. Vicor power modules will be instrumental in achieving this result, supporting OEMs with newly-released automotive grade DC-DC power modules – the BCM1635, and 48V DC-DC regulators, the DCM3735 and the PRM3735 ( Figure 3).

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Figure 3: Vicor BCM6135, DMC3735 and PRM3735 power modules have set a new standard for power density in the automotive industry.  Collectively they solve complex conversion challenges with 800V, 400V, 48V and 12V systems for xEVs power systems

The Vicor suite of new products can streamline design and reduce the PDN size of today’s active suspension systems. Advanced power modules combined with 48V can help overcome a decades-old power problem by minimizing bloated power electronics and optimizing energy recuperation. Furthermore, Vicor enables 48V zonal architectures, which allow a decrease in cable size and a reduction in the overall weight of an active suspension system by multiple kilograms – a savings that is a game changer in a world of overweight BEVs.

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