Industrial IoT Wireless Charging Tool LTC4125

The term “Internet of Things (IoT)” refers to a continuing trend that not only connects people and computers to the Internet, but also connects various “objects” to the Internet and connects various “objects” to each other. For example, if you are deploying an industrial manufacturing facility or a large infrastructure project, connecting more sensors (or actuators) in more places can increase efficiency, improve security, and enable new business models. This constant increase in the level of data exchange is often referred to as "Industry 4.0."

 

Traditionally, various types of sensors used in such plants are connected to a power source by wires. However, there may be no challenges and costs of installing and maintaining cables everywhere in the factory, as reliable, industrial-strength wireless sensors can now be installed, and these sensors can be collected from small batteries or even from sources such as light, vibration or temperature gradients. The energy runs for years. It is also possible to use a combination of rechargeable batteries and a variety of environmental energy sources.

 

Advanced and off-the-shelf energy harvesting (EH) technologies, such as vibration energy harvesting and indoor or wearable photovoltaic cells, generate milliwatts of power under typical operating conditions. Although such low power may seem to be of limited use, years of operation of energy harvesting components such as wireless sensor nodes may mean energy harvesting technology and long-life primary batteries, both in terms of energy supply and cost per unit of energy provided. They are roughly equivalent. Although the main battery is claimed to provide a life of up to 10 years, this depends to a large extent on the level of power drawn from the main battery and the frequency at which power is drawn from the main battery. Systems that offer EH functionality typically recharge after the energy is exhausted, while systems powered by the main battery do not. However, most deployments will use environmental energy as the primary power source, supplemented by the main battery as the main power source, and if the environmental energy disappears or is interrupted, the main battery can be connected. This can be thought of as a “battery life extender” function that provides a longer working life for the system (near the battery's working life), which is typically about 12 years for a battery with lithium thionyl chloride chemistry. In addition, for inherent safety reasons, some rechargeable batteries cannot be charged by wires, but need to be charged by wireless power transfer technology.

 

In many of these applications, it is difficult or impossible to use a connector to charge. For example, some products require a sealed enclosure to target harsh environmentally sensitive electronic components. Other products may simply be too small to fit into the connector, and in products where battery-powered applications may move or rotate, it is almost impossible to charge with a wire. So what alternatives can be used to deal with this type of environment? Obviously, there is a need for a method that requires no connectors and can be wirelessly charged. Wireless charging solutions increase value, reliability and ruggedness in such applications where connectors are not available.

 

In those examples where ohmic connectors are not available, wireless power is a good solution. So what is wireless power? In short, wireless power transfer is the transfer of electrical energy from a power source to an electrical load through an electrical insulator. There are several challenges to transmitting power in this way. When a current flows through the conductor, a magnetic field is generated. In particular, when alternating currents flow through the conductor, a varying magnetic field is created around the conductor. If another conductor is placed in this magnetic field, an alternating current is induced in the second conductor.

 

The magnetic field density is proportional to the magnitude of the current flowing through the conductor. The energy is transmitted from any conductor (secondary magnetic field) that produces a magnetic field (main magnetic field) to the main magnetic field through which the above magnetic coupling exerts a significant influence. In a loosely coupled system, the coupling factor is low, the high-frequency current does not flow a long distance along the conductor, and energy is quickly lost because the impedance along the cable does not match, which causes energy to be reflected back to the source. Or radiate into the air. Figure 1 graphically illustrates a loosely coupled coil connected by a magnetic field.

Figure 1: Wireless power transfer from the primary transmit coil (Tx) to the secondary receive coil (Rx) (including the LTC4120)

The LTC4120 is a wireless synchronous buck charger. The device does not follow the Qi standard; this solution is designed to meet the needs of high reliability applications. The LTC4120's low-level technology and wireless power architecture allow the LTC4120-based system to provide longer power transmission distances and greater tolerance for misalignment. These results are all efficiently implemented so that the receiver does not experience overheating problems. In addition, most industrial WSNs, IoTs, and medical applications do not like interoperability with consumer products.

 

The Dynamic Coordination Control (DHC) tuning technology is embedded in the LTC4120, which gives the device a significant advantage over other wireless powering solutions. To accommodate environmental and load changes, the DHC dynamically changes the resonant frequency of the receiver. DHC achieves higher power transfer efficiency, allowing for smaller receiver sizes, negligible electromagnetic interference, and even allowing for longer transmission distances. Unlike other wireless power transfer technologies, the DHC itself allows for inherent power level management through the inductive energy field, eliminating the need for a separate communication channel to acknowledge the receiver or manage load demand changes during the battery charge cycle.

Wireless charging with the LTC4120 enables or improves many different applications. For example, it is possible to remove connectors that are prone to failure and expensive in harsh industrial environments. Two good examples are chemical treatment plants and refineries. Similarly, for applications requiring sterilization, such as rotary robots and medical imaging systems, wireless charging allows for a completely sealed enclosure. Obviously, after the wires are removed, the rechargeable battery can be placed in such moving or rotating equipment. Another example is an application that is too small to use a conventional connector.

 

So how does the power transfer to the LTC4120 to charge the battery? This requires a wireless transmitter circuit and coil. To this end, Linear Technology designed and developed the LTC4125, a wireless power transmitter that complements the wireless receiver IC in the wireless charging solution space. The LTC4125 is a simple, high performance, single-chip, full-bridge resonant driver that wirelessly delivers up to 5W into a properly tuned receiver. In a complete wireless power transfer system consisting of a transmitting circuit, a transmitting coil, a receiving coil and a receiving circuit, the device is used as a transmitting circuit component.

 

The LTC4125 power controller provides three key functions to improve the basic wireless power transmitter. These three functions are: Auto Resonant, which maximizes the power available to the receiver; optimum power The Optimum Power Search algorithm, which maximizes the overall efficiency of the wireless power system; foreign object detection, which ensures safe and reliable operation when operating in environments with conductive foreign objects. The LTC4125 automatically adjusts its drive frequency to match the LC network resonant frequency. This “auto-resonant” switching allows the device to provide maximum power from a low-voltage input supply (3V to 5.5V) to a tuned receiver such as the Linear Technology LTC4120 wireless receiver and battery charger. The wireless power receiver can also be designed with the LTC4071 parallel battery charger or the LT3652HV multiple chemical battery charger. To optimize system efficiency, the LTC4125 uses periodic transmit power search and adjusts transmit power based on receiver load requirements. The device stops supplying power in the event of a fault or when a foreign object is detected. See Figure 2 for an overview of how the LTC4120 and LTC4125 can be used to implement a complete wireless power transfer and battery charging solution.

Figure 2: LTC4125 and LTC4120 Demonstration Circuitry for Wireless Battery Charging

The LTC4125 also includes a programmable maximum current limit and an NTC input to provide additional protection against foreign objects and overload. Applications include handheld instruments, industrial/military sensors, and similar devices used in harsh environments, portable medical devices, and electrically isolated devices. The LTC4125-based system provides a rugged, stand-alone solution that supports transmission distances up to 15mm and allows for poor coil coupling due to misalignment.

Conclusion: The IoT market has experienced explosive growth in recent years and has involved a variety of products for medical, military and industrial applications. New wave products, including sensor-filled healthcare products and industrial sensors that monitor environmental conditions to improve safety, are growing rapidly. Similarly, EHs for WSN have proliferated in applications such as improving building energy efficiency and system health monitoring for machines and bridges, which are key drivers of low power conversion solutions. Therefore, while using wireless power to power small current devices in harsh environments may seem like a daunting task, Linear Technology offers off-the-shelf, easy-to-use solutions to facilitate this task. .