As intelligent rapidly spreads to many "things" around us - from light bulb, household appliances and cars to medical sensors, industrial machinery, and even the entire city - IoT (IOT) is obviously rising. According to Gartner, by 2020, the number of connected Internet of Things nodes is expected to reach $ 20.4 billion, which is equivalent to several times the human being lived on earth.
However, the development of the Internet of Things is not obstacles. One of the challenges is to keep hundreds of millions of Internet of Things devices 24x7 all-weather running, regardless of their location and application. Regularly replace the battery needs cost and human resources. In addition, all increased energy impact requirements require consideration of these devices.
The solution that can be offset now is energy collection. With this technique, energy captures and converts to electrical energy from the surrounding environment. This may come from many possible sources that may be lost (eg, ambient light, vibration, heat or RF).
In the background of the Internet of Things, the goal of energy collection is not to produce a large amount of energy, but how to use a small amount of energy to power the Internet of Things devices. For example, depending on the ambient light, the harvested power is typically between 10 μW / cm 2 and 10 mW / cm 2, depending on whether the light source is outdoors or indoors. The energy generated is about 4 μW / cm2 to 100 μW / cm2, which also depends on the light source (ie, whether or the person or the machine). Similarly, the thermal energy absorbed from the human body is about 30 μW / cm2, and RF is about 0.1 μW / cm2.
Simply, energy collection will enable the company to truly use the power of the Internet of Things, while saving the money and time that may be wasted on the battery. According to Market Research Corporation IDTechex, by 2022, the world's annual energy collection business should exceed $ 5 billion. But considering the trajectory of future growth, how is the technology formed?
Energy collection system
In essence, energy collection is divided into three steps: collecting, adjusting, and storing. Sensor captures energy from energy (such as environmental light, heat, vibration, pressure, RF, etc.) and outputs electrical energy. Next, the power management IC adjusts the input voltage before passing the input voltage to the storage device (usually the supercapacitor) to accommodate the load, the storage device acts as a buffer between low power, intermittent master, high power source, high power and continuous load .
According to the main energy source, the energy collection system uses different types of sensors. For example, the photovoltaic energy collector captures light energy from outdoor and indoors to supplement or even eliminate batteries from consumer and industrial applications. Similarly, the piezoelectric transducer generates a voltage when mechanical stress is subjected to pressure or motion. With the vibration around the car, aircraft, automation equipment, even around the body, these sensors are expected to supply power to many Internet of Internet equipment. Mide's PPA-1021 is a 0.74 mm thick piezoelectric sensor that produces 4.5 mW of DC output at 28.2V by capturing vibration energy.
Using waste heat, when there is a temperature difference in the connection of two different metals, the thermoelectric sensor generates electrical energy - this phenomenon is referred to as the Saffbeck effect. The MicroPELT TE-CORE Thermal Collection Module is designed to capture locally available waste heat and convert them into electrical energy. Working at the temperature difference of. 1881.10 ° C, a configurable output of 1.8V to 4.5V can be provided.
How do I use the resulting energy?
In order to adjust the collected energy and maintain a stable power supply to the connection load, the energy collection device will require some form of power management integrated circuit (PMIC). Cypus S6AE101a energy collection PMIC is designed for ultra-low power deployment, and its operating current and startup power are only 250 nA and 1.2μW, respectively.
By this chip, a compact solar cell under a low brightness condition of about 100 LX can provide sufficient power to run an Internet of-connected device. As shown in the figure below, it uses a built-in switch to control the power generated in the output capacitor. If the power from the solar cell is not enough to connect the load, it will supplement the power supply of the battery reserve. As a battery-free wireless sensor node solution with an overvoltage protection (OVP) mechanism, its application includes wireless sensors for HVAC, illumination, and security systems, and Bluetooth intelligent sensors.
Solar Acquisition Power Management System Based on Cypus S6AE101A PMIC
Lingllet's LTC3588-2 is another energy acquisition PMIC, designed to be directly connected to piezoelectric, solar or magnetic sensors. It can rectify the voltage waveform and store the collected energy on the external capacitor. It discharges any excess electrical energy through the internal parallel regulator while adjusting the output voltage by high-efficiency nano-power synchronous buck regulator. It has four optional output voltages of 3.45V, 4.1V, 4.5V and 5.0V, which can provide up to 100 mA continuous output current. In order to provide OVP, the chip includes a 20V input protection shuffler. Tire pressure sensors and mobile assets track are potential purposes.
In order to charge and protect the micro-power storage unit, Maxim Integrated provides a boost adjustment circuit for the MAX17710 PMIC. The chip uses a 12-pin UTDFN package, which is optimized for a poorly adjustable power supply, such as the common power supply in the energy collection scheme, and the voltage level is low to 0.75V. Although the output value ranges from 1 μW to 100 mW, the MAX17710 also includes an internal regulator for overcharge protection. The output voltage supplied to the target application is adjusted using a low pressure drop (LDO) linear regulator, and the selectable voltage is 3.3 V, 2.3V or 1.8V. Output regulators operate in selectable low-power or ultra-low power mode to minimize the exhaustion of the battery.
Energy collection charged by Maxim MAX17710 for micro-power storage unit
Always stable and reliable power supply
With high energy storage capacity, the supercapacitor provides stable power to continuous loads in devices that are dependent on energy collected. Murata's DMH Series Supercapacitor has a high capacitance level that can be used as an energy buffer and peak power aid of these devices. These supercapacitors have 35 mF capacitors, 4.5V rated voltages, and 300MΩ electrostatic resistance (ESR), with 20 mm x 20 mm x 0.4 mm package, suitable for applications with limited space and battery life. They have a thin profile, which can be placed under the button battery, the inside of the smart card or the device screen. Main applications include wearable technology, retail system, e-reader, and low-key I / O smart devices.
New products development
Texas Instruments Solar Acquisition and Development Tools EZ430-RF2500-SHE enables design engineers to create and test a wireless sensor network that permanently powered. Under the driving of ultra-low power MCU, the tool includes a high-efficiency solar panel, even in indoor lighting conditions, sufficient power can be provided to operate the wireless sensor application without any additional battery.
WURTH Electronics's To Go Kit provides energy collection, energy management, and storage in a package, and a complete development tool. The kit includes a solar cell (32 mm x 50mm) and a thermoelectric generator (40 mm x 40mm) as two energy collection sources and is equipped with an EFM32 Giant Gecko MCU using a 48 MHz ARM CortexTM M3 core.
As the energy collection technology is almost ubiquitous, the researchers are busy exploring new application possibilities. In one such case, Michigan's scientists have been powered by a device capable of acquiring energy from human heartbeat, thereby powering the heart pacemaker or implantation defibrillator, thereby achieving the core of the technology. This development can potentially eliminate risks and troubles related to regular battery replacement of key medical devices. Similarly, researchers are also committed to accessing energy from human body heat, motion, and vibration to support the power requirements of implantable IoT equipment. Energy is rich in all parts, but currently, it is not the case. Because energy collection can make up for this gap, it doesn't have to doubt, energy collection is one of the best ways to obtain low power power supply.
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