Coreless power conversion suits high magnetic fields

Using the latest technology in high-frequency switching topologies and digital control with proprietary firmware to optimise efficiency and voltage regulation, Powerbox’s GB350 buck-converter module is the first building block in its category that is able to operate safely when exposed to high radiation magnetic fields of 2 to 4 Tesla.

GB350 delivers an output power of 350W and when higher power levels are required it can be paralleled using an interleaving mode thus reducing EMI. 

Medical and industrial applications such as magnetic resonance imaging (MRI) and particle accelerators (PA) generate high magnetic fields to induce the RF energy required to activate the hydrogen nuclei in the case of imaging, or to accelerate particles in research and industrial equipment.

Modern MRI systems usually generate 1.5 to 4 Tesla, making conventional power supplies using ferrite material useless due to inductance saturation as a result of the MRI magnet disturbing the energy transfer.

To prevent parasitic saturation, power supplies are traditionally positioned outside the shielded operation room. Installing the power supplies remotely requires long cables with subsequent power losses, and it is also a big challenge to power the latest generation of measuring equipment that require stable and tightly regulated voltages under fast transient load conditions.

To reduce energy consumption and to guarantee the level of quality required by integrated equipment, systems manufacturers are now integrating local power supplies near to the load. However, placing equipment directly in the radiated magnetic field requires an innovative power solution known as ‘coreless power units’ and a state of the art switching power stage.

Designed to respond to this demand and to guarantee the highest efficiency and tightly regulated output voltage at any load-condition, Powerbox’s GB350 coreless power unit is fully controlled by a digital processor that manages the complete power unit from switching parameters (e.g. dead-time and duty-cycle optimisation) to output voltage characterisation.

To guarantee a high level of flexibility and the possibility to re-profile the power unit characteristics when equipment manufacturers upgrade new hardware or implement a software revision, the GB350 micro-controller can be programed with optimised configuration files downloaded through the digital interface.

“Combining the latest technology in digital power and very advanced coreless energy transfer, the GB350 is an important component of the Powerbox Custom Power Solution toolbox,” said Tomas Isaksson, Chief Technology Officer at Powerbox.

“With more than 3,500 Custom Power projects delivered to market, it is very important to rely on a strong platform portfolio, reducing time to market in demanding applications such as medical magnetic resonance imaging.”

The standard GB350 platform delivers a nominal current of 50A and preset output voltages of 6.8, 3.3 or 1.6V. As part of the Powerbox Custom Power Solution toolbox, other output voltages are available on request.

The GB350 has a switching frequency of 600kHz. Equipment installed within the magnetic field often require higher power levels than 350W and also very low EMI. With a switching frequency of 600kHz and its 4 phase interleave mode, the GB350 has a resultant output frequency of 2.4MHz. This allows easier filtering and extremely fast regulation response times. The unit also includes EMI shielding to lower radiated emission.

As part of Powerbox’s Custom Power Solution Toolbox, the GB350 and products based on that technology are tested, verified and qualified in accordance to end customers’ specifications.