Power Electronics Europe April/May Issue 2022

INDUSTRY NEWS 11 www.power-mag.com Issue 2 2022 Power Electronics Europe Markets are expected to open up for sensors capable of delivering response times as low as 100 ns and unprecedented cut-off frequencies above 1MHz. Much of what many operators in the industrial world are looking to achieve in terms of sustainability and productivity gains revolves around having the most efficient power converters. Suitable for working in the harshest of environments, including in a wide range of temperatures, the power converter of the future will need to be high- power yet lightweight, quiet and capable of high-frequency operation. Low power consumption will be essential. The high-frequency requirement and the need to be as compact as possible mean that power converters must incorporate smaller passive components if benefits of reduced size and weight are to be realised. The trend to move away from pure silicon and increasingly make use of high-frequency SiC MOSFETs in high-voltage pulsed- power circuits has made it possible to cut space requirements, reduce costs, boost efficiency and enhance performance. Because of their faster switching capabilities, SiC-based devices are able to operate at bandwidth frequencies that are greater than 100 kHz. This has led to them being used in such applications as uninterruptible power supplies (UPSs), solar inverters, AC variable speed and servo motor drives, power factor correction (PFC) and computer-controlled welding machines. However, there has always been a trade-off between performance and response time and users in these various market sectors have been struggling for a solution that can satisfy their increasingly demanding requirements. While classic open loop transducers and closed loop versions are capable of frequency responses as high as 300kHz, in today’s market these are still not sufficient for the high bandwidth sensing needs that have been Are hybrid transducers the future for power converters with SiC MOSFETs? driven by the adoption of SiC insulated-gate bipolar transistors (IGBTs). Bandwidth above 1 MHz LEM was approached by a customer in the welding sector, for whom existing response times and frequency responses on their power converters were proving to be inadequate. It was against this backdrop that LEM developed a hybrid transducer that more than trebled the performance levels of anything else on the market. The hybrid is a mix of ASIC and DC-based transducer with a pure inductive coil to speed up the signal. Thanks to the pick-up coil on LEM’s ASIC, the transducer is capable of reacting like a current transformer. While existing AC transducers based on a pure coil can achieve higher levels, there is no DC transducer featuring open loop technology and a pick-up coil that can perform at bandwidths above 1MHz – until now. The LEM solution – the HOB family of around 20 low power consuming multi-range current sensors capable of measuring DC, AC or pulsed current up to 250A – was developed to meet high bandwidth sensing targets when using fast-switching SiC MOSFETs in high-voltage pulsed-power circuits where rapid and flexible high-voltage pulses are essential. The customer specifically wanted a top performance solution that delivered rapid response reaction times and expanded bandwidth, all in a smaller footprint. Totally different semiconductor technology W hile a closed loop sensor would ordinarily represent a high-cost option for any sector wanting to achieve these goals, LEM expects its hybrid transducer to become rapidly attractive to a range of markets that are looking to adopt any kind of switch-mode converters based on SiC and GaN WBG power modules. The growing trend to switch-mode converters is being driven by the need for devices and equipment to be as small as possible and to achieve superior power/weight ratios. Thanks to what LEM calls “a totally different semiconductor technology”, SiC or GaN very high-speed transistors not only ensure faster switching times but also offer higher frequency capabilities and higher voltage withstanding. The company expects that this transistor technology will become the norm in just five years. Far more important than bandwidth frequency in the HOB family, however, is response time – the time between the primary current and the output on the transducer. This was a key factor for the customer who was aware that transistors that are switching faster and faster must have a current transducer able to follow the di/dt as closely as possible. Response rate as little as 100 ns T raditionally, while the di/dt could be as high as 500 A per microsecond (possibly even 1kA/µs) with this technology, the response The Litz Wire Experts We help power the EV and e-mobility platforms of today & the future Insulated Litz for High- Frequency Applications Triple Insulated Winding Wires for Power Electronics UL & VDE certifications for applications up to 1,500 Vpk and thermal classes of 155°C and 180°C Specialty Litz conductors for applications up to 260°C Rubadue.com +1 970.351.6100