TDK Corporation has expanded its EPCOS ERU33 series of high-current chokes with the new ERU33M, which is engineered using a novel core material that supports higher current levels. The new core material is constructed from an alloy powder with softer saturation characteristics than prior core materials, enabling more energy storage.
ERU33M low profile inductor. Image used courtesy of TDK
With their higher current capabilities, the ERU33M models target next-generation automotive and industrial applications that must operate at increased power levels and densities. Applications include energy storage in switch mode power supplies for EV onboard chargers (OBC), solar inverters, and similar power conversion applications.
The through-hole-mounted inductors support saturation currents up to 120 A, inductance values from 1.4 µH to 7.2 µH, and a DC resistance as low as 0.46 mΩ. Flat wire windings support a compact design with a height profile of either 11 mm or 15.3 mm.
The new parts are AEC-Q200-qualified with an operating temperature range of -40 °C to 150 °C.
Energy Storage Chokes for Switching Regulators
The ERU33M chokes are essentially flat wire inductors constructed with a single winding around a magnetic core. The inductive properties of the choke allow it to store energy within the core, an essential function for DC-DC power conversion circuits.
In a step-down (buck) converter, a DC input voltage is modulated by a switch to drive an energy storage circuit. When the converter switch is closed, the output inductor absorbs energy from the DC input and stores it in its magnetic core. When the switch opens, the inductor uses this stored energy to continue providing current to the load. The switch, inductor, and capacitor are all designed and regulated to provide load current at a reduced voltage with as little power loss as possible.
Stored energy in the output inductor provides load current. Image property of EETech
These basic principles can be applied across more sophisticated power conversion architectures, like those used for EV charging.
Power architecture for EV charging. Image used courtesy of Digi-Key
Improved Saturation Characteristics
For an inductor, saturation current is the current level at which its inductance value rapidly drops. At this point, the magnetic core is fully saturated and incapable of storing more energy. Operating an inductor beyond its saturation point can be problematic since the lower inductive impedance can result in excessive currents and high heat generation.
With its alloy powder core and improved saturation characteristics, the new ERU33M supports higher current levels in a smaller area, resulting in more energy density.
Inductance vs. load current for the ERU33M-1R4L. Image used courtesy of TDK
The Need for More Power Density
Modern power conversion applications increasingly require smaller form factors with higher power densities. In power circuit design, component height is often the limiting factor in supply density, with inductors and other magnetics often being the most challenging components to meet design targets.
With its improved saturation properties and energy storage capabilities, the ERU33M moves the needle on power density, offering a high current capacity (120 A) and low profile (15.3 mm) through a hole-mountable package. The net result is designs that are small, light, and low-cost—coveted characteristics for automotive and industrial designs.
