www.vicorpower.com 48V POWER INFUSIONS 9 www.power-mag.com Issue 3 2025 Power Electronics Europe bidirectional power switching capability. It’s imperative that the direction of the current change rapidly for top performance in each direction. 3. Fast transient response times. A DC-DC converter with high slew rate is critical for active suspension. With anything less, a battery or supercapacitors must be added to compensate for inadequate transient performance. The Hongfa approach to solving these tough system challenges was to rely on the benefits of a 48-volt PDN without an intermediary battery. The main challenge was that, even while some conventional DC-DC converters can deliver power without the need for an intermediate battery, they face a tradeoff in that they are bulky and lack the fast response time required to meet the regenerative demands to recoup and store power. Hongfa uses Sine Amplitude Converter Technology to address top technical challenges Alternatively, Vicor bidirectional, fixed-ratio 800V-to-48V DC-DC bus converters provide the fastest transient response of any DC-DC converter. They also have industry-leading power density and efficiency and are designed specifically for a 48V-centric power delivery architecture. Their advanced planar packaging simplifies thermal management systems design further reducing overall footprint and weight. Unique among DC-DC converters, they offer symmetrical performance with their ability to buck or boost with the same level of power (Figure 2). This feature, which is essential to deliver optimal power regeneration for active suspension, is a result of proprietary Vicor Sine Amplitude Converter (SAC™) technology. The SAC uses a zero-current and zero-voltage soft-switching technique and fixed switching frequency in excess of 1MHz to provide fixed-ratio DC-DC conversion. The SAC output voltage (VOUT) is proportional to its input voltage (VIN) at no load per Equation 1. VOUT = K•VIN (1) In Equation 1, K is commonly referred to as the transformation ratio and is defined as the ratio of output voltage and input voltage. K is a fixed value for a given model of SAC. In bidirectional mode, a single SAC can be deployed with the intent that once excited, the module is to deliver power in either the forward or reverse direction, depending on the way in which the SAC is being actively driven at a given instant in time. Such performance is essential to deliver optimal power regeneration for active suspension. Linking active suspension directly to the main battery with a bidirectional power converter enables top energy recuperation. Similar to how a spring absorbs and releases energy, active suspension uses regenerative shock absorbers to collect kinetic energy that is returned to the battery. While this can be done with a conventional bidirectional DC-DC converter, few manufacturers can design a system with the performance necessary for transient response, peak power slew rate (about 8 million amps per second), and power efficiency to manage the bidirectional power flow between the converter and battery power source (Figure 3). Fully capitalizing on these advantages, Hongfa has designed and developed a compact system that includes CAN communication, high-voltage protection and EMI filtering. Their innovative mechanical assembly optimizes thermal dissipation within a very compact footprint. In the regenerative active suspension application, the 800V battery sources current when the vehicle travels over smooth road surfaces, and the suspension actuation motor is the 48V load. When the vehicle traverses a bumpy road, the linear motors in the suspension system momentarily become generators (compression), increasing the voltage on Figure 2 Sine Amplitude Converter (SAC) -- with TM SAC™ application topology options.The SAC operates as forward, reverse or bidirectional power converters which have isolation barriers set between their primary and secondary power ports. The gray bar represents the SAC inbuilt galvanic isolation barrier between the input and output power ports Figure 3 Vicor BCM6135 DC-DC converter di/dt is 8 million amps per second, offering an unrivaled slew rate which is essential to support optimal energy recuperation and storage for the Hongfa active suspension system.
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