THE I IN


NTERNET of THING


HINGS


SUPPLEM SUPPLEMEN T


mismatch along the cable, which causes the energy to be reflected back to the source or radiated into the air. Figure 1 shows a graphical representation of loosely coupled windings connected via a magnetic field.


The LTC4120 fromthe Power by Linear Group is a wireless synchronous buck charger. It is not compliant with the Qi standard; rather this solution has been designed to address the needs of high reliability applications. Thi s device embodies an underlying technology and wireless power architecture to allow a LTC4120-based systemto operate at a greater power transmission distance with more tolerance for misalignment. This is achieved efficiently so that the receiver does not experience thermal problems. In addition, most industrial WSNs, IoT and medical applications would prefer not to be interoperable with consumer-grade products .


Dynamic harmonisation control (DHC) tuning technology is embedded in the LTC4120 which allows it to provide significant advantages over other


wireless power solutions. In response to environmental and load changes, DHC varies the resonant frequency of the receiver dynamically. DHC achieves greater power transfer efficiency, enabling smaller receiver sizes and generating negligible electromagnetic interference even as it all ows greater transmission range.


,


Unlike other wireless power transfer technologies, DHC allows intrinsic power levelmanagement via the inductive power field, eliminating the need for a separate communication channel to validate receivers or tomanage variation in load demand during the batter y charge cycle .


BAT


ATTER CHARGING FROM WIRELESS POWER


TTERY CHARGING FROM WIRELESS POWER


Wireless charging with the LTC4120 enables or improves many different applications. For example, expensive connectors that become failure prone in harsh industrial environments can be eliminated. Two good examples are chemical processing facilities and gasoline refineries. Similarly, wireless charging allows for completely sealed enclosures for applications that require sterilisation, such as rotating robotics and medical imaging syste ms Clearl y, eliminating wires enables rechargeable batteries to be placed in these types of moving or rotating equipment. Another examples is in applications that are too small to use a conventional connector.


.


LTC4120 so that is can cha So, how is power transfer


rge a battery? red to the


foreign objects. The LTC4125 automatically adjusts its driving frequency to match the LC network resonant frequency. This Auto Resonant switching allows the device to deliver maximumpower froma low voltage input supply (3V to 5.5V) to a tuned receiver such as Linear’s LTC4120 wireless receiver and battery charger. Wireless power receivers can also be designed with the LTC4071 shunt battery charger or the LT3652HV multi -


bj


chemistry battery charger. To optimise systemefficiency, the LTC4125 employs a periodic transmit pow adjusts the transmissi


on power based on er search and


the receiver load requirements. The device stops delivering power in a fault condition, or in the case of a detected foreign obj


LTC4120 and LTC415 can be used for a complete wireless power transfer and battery charging solution . This device also includes a


programmable maximumcurrent limit and an NTC input as additional means for foreign obj


bject and overload protection. Applications include handheld


instruments, industrial/military sensors and similar devices in harsh


Well, a wireless transmitter circuit and coils are needed. To this end, Analog Devices’ Power by Linear Group designed and developed the LTC4125 - a wireless power transmitter that complements wireless receiver ICs in the wireless


charging solution space. The LTC4125 is a simple and high performance monolithic full bridge resonant driver capable of delivering up to 5W of power wirelessly to a properly tuned


functions as the receiver. It


component in a transmit circuit


complete wireless


systemcomprised power transfer


circuitry, transmit of transmit


coil, receive coil and receive circuitry.


This device’s power controller


improves upon a basic wireless power transmitter by providing three key


features: an Auto Resonant function that maximises available receiver power, an OptimumPower Search algorithm that maximises overall wireless power system efficiency, and foreign obj


ensure safe and reliable operation when working in the presence of conductive


/ ELECTRONICS ELECTRONICS e a


“”“Simply put wireless power transmission is the


transmission of electrical


energy from a power source to an electrical load through electrical insulator(s) ...”


Figure 2. Figure 2. LTC4125 & L LTC4125 & LTC4120LTC4120


demo circuits for wireless battery charging


demo circuits for wireless battery charging


environments, portable medical devices and electrically isolated devices. LTC4125-based systems offer robust, standalone solutions capable of large transmission distance of up to 15m m, and are tolerant of poor coil coupling due to misalignment.


The IoT market has exploded in recent years and includes a wide variety of products for the medical, military and industrial application spaces. A new wave of products, including sensor-filled medical health products and dustrial sensors for monitoring vironmental conditions for proved safety are growing at a apid pace. Similarly, the


m n


oliferation of EH in WSNs in plications for improved building ergy efficiency and systemhealth monitoring for machines and idges are key drivers for low wer conversion solutions. So,


n p r


o r


hile powering low-current devices hard environments by utilising ireless power transfer might seem


lik daunting task, Analog Devices’ Power by Linear Group offers an off-the - shelf easy-to-use solution to do just that.


bject detection to


Analog Devices Ltd. www.linear.com www.analog.com


www.linear.com www.analog.com 01628 477 066


ELEC ELECTRONICS | DECEMBER JANUAR 201 ECEMBER//JANUARY 2018 S5 S5


bject. See Figure 2 for how the


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