COVER ST RY R STORY


to dissipate the excess power as heat. There are several ways to deal with


excess power capacity when the demanded receiver power is low. The rectified voltage can be clamped with a power Zener diode or transient voltage suppressor. However, this solution is typically large and generates considerable heat. The


transmitter power can be reduced, but this will either limit the available received power or it will reduce the transmit


distance. It is also possible to communicate received power back to the transmitter and adjust transmit power accordingly. This is the technique used by wireless power standards such as the Wireless Power ConsortiumQi standard. However, it is also possible to solve this issue in a compact and efficientmanner without resorting to complicated digital


communication techniques. Techniques that communicate via small variations in the transmitted power level require a minimumamount of power transmission andmay not work for systems wit h variable transmit distances .


AN EASY TO USE C FOR WIRELESS CHARG NG


AN EAS CHARGINGI


Tomeet these goals, Linear Technology’s LTC4120 wireless power rec battery charger integrates t PowerbyProxi, Linear’s tech partner. PowerbyProxi’s pat


echnology by eiver and


ented Dynamic nology


Harmonisation Control (DHC), technique enables high efficiency contactless charging without thermal or electrical overstress concerns in the receiver Using this technology, up to 2Wcan be


. WORKING IN PA


transmitted at a distance of up to 1.2cm. However, for single-cell Li-Ion batteries, themaximumcharge voltage of 4.2V and maximumcharge current of 400mA will limit this value to 1.7W. Similarly, the 2W maximumwill limit 2 Series Li-Ion


batteries (8.4Vmaximumcharge voltage) to 240mA of charge current.


Themetrics of power, efficiency, range and size determine syste mperformanc e


WORKING IN PAR NERSHIP ARTNERSHIP


PowerbyProxi has been working to deliver wireless power solutions for industrial customers since 2007. Rather than invest


marketing efforts, a great deal ofmo


they decided to develop ney into its own


and improve their technology and to partner with industry leaders such as Linear Technology to bring the technology tomarket. With significant success and a broad portfolio of technology


and so the LTC4120-basedwtireless power systemwas designed to receive up to 2W at the battery up to a distance of 1.2cm when used with one of several transmitter options. Efficiency calculations vary


tremendously based on the technique and components used. Typically, the battery will receive 45%– 55%of the DC input power fed to the transmitter in an LTC4120-based system.


PowerbyProxi’s DHC tuning technology embedded in the LTC4120 provides


significant advantages over other wireless power solutions. In response to


environmental and load changes, DHC dynamically varies the resonant frequency of the resonant tank circuit receiver. DHC achieves grea


ter power on the


transfer efficiency, enabling smaller / ELECTRONICS ELECTRONICS ELEC RO ELECTRONICS CS | JUNE 201 JUNE 2016 13 13 embodiments to its credit, they are now Figure 2: Figure 2 : LTC4120 application


LTC4120 application schematic illustrates aschematic illustrates a complete wicomplete wirelessreless


battery charging circui battery charging circuitt USE I IC FOR WIRELES S


receiver sizes, even as it allows greater transmission range. Unlike other wireless power transfer technologies, DHC enables intrinsic power levelmanagement as part of the inductive power field, eliminating the need for a separate communication channel to validate receivers or tomanage variation in load demand during the battery charge cycle.


It is clear that DHC solves a problem fundamental to all wireless power


systems. Every systemmust be designed to receive a certain amount of power at a givenmaximumtransmit distance. Every systemmust also be designed to survive a no-load condition atminimumtransmit distance. The competitive alternatives solve this problemwith a complicated digital communication systemthat adds complexity and cost, limiting power transmission distance. The LTC4120- based wireless power systemeasily solves this problemby incorporating PowerbyProxi’s DHC technology .


Figure 1: Figure 1:


Wireless power transfer from a primary transmit coil (Tx) to a


Tx) t o a


secondary secondary receive coilreceive coil ((Rx), including the LTC4120


Rx), including the LTC4120


Wireless power transfer from a primary transmit coil (Tx


gaining recognition as the leading glo lab wireless power company.


One of the key reasons why Linear partnered with PowerbyProxi was d ue to their significant IP portfolio and solution design know-how that offers customers the leading technology in the industry and also assurance that the technology is fully backed by IP. PowerbyProxi hasmore than 30 patents in process andmany more in the review and filing stages, making themthe leading innovator and IP leader in the wireless power field.


Outside of themass consumermarket for the wireless charging of “i” this, or “robot” that, there is a class of portable industrial andmedical products where the ability to wirelessly charge their internal batteries across air gaps or through non- ferritematerials up to a centimetre or so, is a “must have” requirement for their deployment. Up until now, a design engineers’ options have had limitations, which have hindered their end products’ success and viability. Fortunately thank s to the recent introduction of the LTC4120 fromLinear Technology, that’s all about to change. This highly integrated IC, which can wirelessly receive power transmitted froma coil of up to 1.2cm apart, as well as charg provides a simple and


,


is the embodiment of wireless charging made easy – no connectors necessary!


Linear Technology (UK) Ltd. www.linear.com


li


FEAT RE FEA ATURE


effective solution. It e a battery,


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