Tony Armstrong, Linear Technology
To better understand why Industrial automation is so important, a few trends need to be discussed and reviewed. First up is sustainability. Sustainability, in terms of energy and resource efficiency, is a key ingredient for the success of the global manufacturing industry.
The growing focus on the implementation of energy efficient solutions in both process and discrete industries will also promote sustainable manufacturing. By way of an example, energy efficiency concerns will dominate business in the electric motors market, with class IE3 energy efficiency. (This classification comes from the premium efficiency industry standard, new in Europe or “Nema Premium” in the United States (EISA) applicable from January 2015 or 2017 depending on the power ratings). Similarly, wastewater treatment and handling pumps will dominate traditional water pumps across the globe.
Factories of the future will be driven by megatrends such as cloud computing, cyber security and mobile and wireless communication technologies. Accordingly, the need for higher productivity and greater efficiency will drive organizations to implement greater interaction between the factory floor and enterprise across all end users. Asset management and flexible manufacturing will also drive factory integration with vitality and there will be high potential for automation and customized service solutions in industrial applications.
Power is key
Next up is power consumption, since its conservation is a key to minimizing the consumption of our natural resources. Power consumption in any system can be addressed in two ways. Firstly, by maximizing conversion efficiency across the entire range of load current, and secondly, by reducing the quiescent current drawn from the DC/DC converters in all modes of operation. Therefore, in order to have an active role in the reduction of system power consumption, power conversion and management ICs must be more efficient. That is, have lower power loss and have very low levels of power consumption in both light load and sleep modes.
By way of an example, consider if you will an embedded system commonly found in many industrial automation systems. These embedded systems are usually powered via a 48V backplane. This voltage is normally stepped down to a lower intermediate bus voltage of typically 12V to 3.3V to power the racks of boards within the system. However, most of the sub-circuits or ICs on these boards are required to operate at voltages ranging from sub-1V to 3.3V at currents ranging from tens of milliamps to hundreds of amps. As a result, point-of-load (POL) DC/DC converters are necessary to step down from the intermediate bus voltage to the desired voltage required by the sub-circuits or ICs. These rails have strict requirements for sequencing, voltage accuracy, margining and supervision.
Since there can be upwards of 50 POL voltage rails in a datacom, telecom or storage systems, system architects need a simple way to manage these rails with regards to their output voltage, sequencing and maximum allowable current. Certain processors demand that their input and output (I/O) voltage rise before their core voltage, alternatively certain digital signal processors (DSPs) require their core voltage rise before their I/O. Furthermore, power down sequencing is also necessary. Therefore, system architects need an easy way to make changes to optimize system performance and to store a specific configuration for each DC/DC converter in order to simplify the design effort.
Furthermore, in order to protect expensive application specific integrated circuits (ASICs) from the possibility of an over voltage condition, high-speed comparators must monitor the voltage levels of each rail and take immediate protective action if a rail goes out of its specified safe operating limits. In a digital power system, the host can be notified when a fault occurs via the PMBus alert line and dependent rails can be shut down to protect the powered devices such as an ASIC. Achieving this level of protection requires reasonable accuracy and response times on the order of tens of microseconds.
In areas of great innovation, it’s not always easy to convey the content of the innovation to the end user. It is generally accepted that there are many opportunities in the new and clean energy market for power management, also known as alternative energy. As there is plenty of ambient energy in the world around us, the conventional approach for energy harvesting has been through solar panels and wind generators. However, new harvesting tools allow us to produce electrical energy from a wide variety of ambient sources.
It is not the energy conversion efficiency of the circuits that is important, but more the amount of “average harvested” energy that is available to power it. For instance, thermoelectric generators convert heat to electricity, Piezo elements convert mechanical vibration and photovoltaics convert sunlight or any photon source. This makes it possible to power remote sensors, or to charge a storage device such as a capacitor or thin film battery, so that a microprocessor or transmitter can be powered from a remote location without a local power source.
It is evident that efficient energy management can bring many benefits to those who implement them in their applications or end products while also reducing the burden on our precious and limited global resources. This is not only good for business but also the environment. However, where does one find the right products with which to design such systems? Well, Linear Technology for one has been designing and developing many of its newer power management and conversion ICs to be more efficient, have digital telemetry and interface capabilities, scavenge low levels of ambient energy and have very low quiescent currents.
The use of a standard serial digital bus, for example I2C, enables simple and efficient communications to and from digitally equipped DC/DC converters, and emerging standards like PMBus facilitate component interoperability. Important regulator parameters, including startup characteristics and timing, output voltages and current limits, margining specifications and over- and undervoltage supervisory limits can all be directly programmed digitally instead of set with resistors and space-consuming sequencing and monitoring products. Further, critical operating parameters such as temperature and input and output voltages and currents can be routinely monitored and used to optimize system performance and reliability.
When digital power is done correctly, it can reduce data center power consumption, shorten time to market, have excellent stability and transient response, and increase overall system reliability such as in networking equipment.
System architects of networking equipment are being pushed to increase the data throughput and performance of their systems as well as add functionality and features. At the same time, pressure is being applied to decrease the systems overall power consumption. In data centers, the challenge is to reduce overall power consumption by rescheduling the work flow and moving jobs to underutilized servers, thereby enabling shutdown of other servers. To meet these demands, it is essential to know the power consumption of the end-user equipment. A properly designed digital power management system can provide the user with power consumption data, allowing for smart energy management decisions to be made.
The LTC388x family of digital power ICs from Linear Technology provides highly accurate digital power system management with its high resolution programmability and fast telemetry read-back for real-time control and monitoring of critical point-of-load converter functions. For example, the LTC3880 is a dual output high efficiency synchronous step-down DC/DC controller with I2C-based PMBus interface with over 100 commands and onboard EEPROM. The device combines a best-in-class analog switching regulator controller with precision mixed signal data conversion for unsurpassed ease of power system design and management, supported by the LTpowerPlayTM software development system with easy-to-use GUI.
For the harvesting of low levels of power to be used in industrial wireless sensor or even wearable technology applications, Linear Technology its LTC3331 to specifically address these requirements, as illustrated in Figure 1.
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Figure 1. LTC3331 Energy Harvester & Battery Life Extender
The LTC3331 is a complete regulating energy harvesting (EH) solution that delivers up to 50mA of continuous output current to extend battery life when harvestable energy is available. It requires no supply current from the battery when providing regulated power to the load from harvested energy and only 950nA operating when powered from the battery under no-load conditions. The LTC3331 integrates a high voltage EH power supply, plus a synchronous buck-boost DC/DC converter powered from a rechargeable primary cell battery to create a single non-interruptible output for energy harvesting applications such as those in wireless sensor nodes (WSNs).
The LTC3331’s EH power supply, consisting of a full-wave bridge rectifier accommodating AC or DC inputs and a high efficiency synchronous buck converter, harvests energy from piezoelectric (AC), solar (DC) or magnetic (AC) sources. A 10mA shunt allows simple charging of the battery with harvested energy while a low battery disconnect function protects the battery from deep discharge. The rechargeable battery powers a synchronous buck-boost converter that operates from 1.8V to 5.5V at its input and is used when harvested energy is not available to regulate the output whether the input is above, below or equal to the output.
The LTC3331 battery charger has a very important power management feature that cannot be overlooked when dealing with micro-power sources. The LTC3331 incorporates logical control of the battery charger such that it will only charge the battery when the energy harvested supply has excess energy. Without this logical function the energy-harvested source would get stuck at startup at some non-optimal operating point and not be able to power the intended application through its startup.
The LTC3331 automatically transitions to the battery when the harvesting source is no longer available. This has the added benefit of allowing the battery operated WSN to extend its operating life from 10 years to over 20 years if a suitable EH power source is available at least half of the time, and even longer if the EH source is more prevalent. A supercapacitor balancer is also integrated allowing for increased output storage.
There are many products which help to make are lives more comfortable, productive and easier. However, one of the cost penalties is the depletion of our natural resources. Nevertheless, society is not going let this happen without attempting to mitigate the potential negative effects. A major action to address this is the responsible use of our energy resources. And one of the most effective ways to enact this is through the efficient energy management of industrial automation systems, communications equipment and networking infrastructure.
However, to do this, the necessary building block power management and conversion ICs need to be available. Fortunately, thanks to analog supplies like Linear Technology, systems designers have a choice to make the right selection for their end equipment.