PMICs for energy harvesting applications
Power management integrated circuits, in short PMICs are specialized blocks/circuitry of any embedded / autonomous systems, that are responsible for delivering/ managing power requirements of the system. The importance of PMICs goes a long way in energy harvesting applications, since every minuscule of energy from ambient environment has to be micromanaged. This article throws some light upon basics of energy harvesting along with key design considerations to be taken while choosing / selecting an energy harvesting power management IC
Introduction
Harvesting energy from the environment is a vital subject by itself, since random energy is freely available around us in various forms. The real challenge of energy harvesting lies in the very fact as to how this randomized energy can be converted to suitable electrical energy, which can be used for powering various IOT sensor nodes, that are already being used in different smart city applications such as building automation, smart homes, industry 4.0 to name a few.
Major blocks of an EH system consists of four elements.
1. Energy Harvester
2. Energy storage system
3. Load (MCU, sensor)
4. Wireless module / transceiver
1. Energy harvester: An energy harvester is an ECM ( Electronic control module), that can harvest various types of ambient energy sources such as solar energy, kinetic energy, electromagnetic energy , RF energy etc, to name a few.
2. Energy storage system: The captured energy from the ambient sources has to be 'power
-conditioned' to deliver the required energy to the load. A suitable power management block or a dedicated power management IC (PMICs) will do the job. The incoming energy will be suitably conditioned by PMICs to deliver the required power to the end load. It is also to be noted that energy from PMIC has to be stored in secondary energy storage system such as batteries, capacitors. Secondary storage devices are used in case the power density of the EH remains low.
3. Load: The conditioned energy from PMICs or batteries will have to be delivered to suitable loads such as MCUs, sensors interfacing the MCUs, other IOs, It is noteworthy to mention that the energy requirements of the load has to be calculated before choosing PMICs for your application.
4. Wireless module / transceiver: A wireless module is imperative in any EH system, to network the sensor data / data available from the EH to any suitable user interface/GUI for the purpose of data logging. Data can be networked using suitable short range wireless network protocols such as zigbee, BLE, LIN etc to name a few.
Power management is one of the most vital sections of any electronic circuitry that really cannot be ignored, since the very absence of this block halts the functioning of the entire system. In simple layman terminology the main task of any power manager in a system is to deliver the required amount of voltage to all blocks of the system. It will be seen that a power manager performs more than just delivering voltage, which will be seen in this article.
Energy harvesting
Energy harvesting is the process of utilizing energy sources available around us, such as solar, wind, kinetic, electromagnetic, radio frequency, to name a few to power various electronic systems and sub systems.
1. Energy Harvester
2. Energy storage system
3. Load (MCU, sensor)
4. Wireless module / transceiver
1. Energy harvester: An energy harvester is an ECM ( Electronic control module), that can harvest various types of ambient energy sources such as solar energy, kinetic energy, electromagnetic energy , RF energy etc, to name a few.
-conditioned' to deliver the required energy to the load. A suitable power management block or a dedicated power management IC (PMICs) will do the job. The incoming energy will be suitably conditioned by PMICs to deliver the required power to the end load. It is also to be noted that energy from PMIC has to be stored in secondary energy storage system such as batteries, capacitors. Secondary storage devices are used in case the power density of the EH remains low.
3. Load: The conditioned energy from PMICs or batteries will have to be delivered to suitable loads such as MCUs, sensors interfacing the MCUs, other IOs, It is noteworthy to mention that the energy requirements of the load has to be calculated before choosing PMICs for your application.
4. Wireless module / transceiver: A wireless module is imperative in any EH system, to network the sensor data / data available from the EH to any suitable user interface/GUI for the purpose of data logging. Data can be networked using suitable short range wireless network protocols such as zigbee, BLE, LIN etc to name a few.
Getting inside PMIC
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| A PMIC in an embedded system |
A power management IC, in a system can be housed as a separate unit or it can be a part of a larger circuit/sub circuit. If the system is a simple system, then power can be delivered or managed, using a linear regulator, and if the system is a bit demanding, then switching regulators can takeover the seat. But for delivering power for multiple power rails and for other specialized functions, a dedicated PMIC is a must.
Functions of a PMIC
As mentioned previously, a dedicated PMIC has quite a number of functions to be executed. Some of it's very common house keeping activities include
1. DC to DC conversion
2. Power sequencing
3. Voltage scaling
4. Power selection from multiple sources
In order to facilitate all the above operations, a dedicated PMIC in a system, might consist of various functional blocks such as set of linear regulators, DC DC converters, low dropout regulators (LDOs), and many passive elements. Depending on its intended end usage/application, there can be 'n' numbers of functional blocks. There is no one hard and fast rule. It depends for what the PMIC is designed for that dictates the internal architecture of the PMIC.
In order to facilitate all the above operations, a dedicated PMIC in a system, might consist of various functional blocks such as set of linear regulators, DC DC converters, low dropout regulators (LDOs), and many passive elements. Depending on its intended end usage/application, there can be 'n' numbers of functional blocks. There is no one hard and fast rule. It depends for what the PMIC is designed for that dictates the internal architecture of the PMIC.
