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Developing power management solutions to meet the demands of harsh environments

In industrial applications, the concept of predictive maintenance is changing, thanks to the Internet of Things (IoT). What might once have been based on hours of service can now be more precisely modelled using real-world data, gathered at its source. The impact of this will be most apparent in factory automation, as well as causing widespread change in the transportation and energy infrastructures. In order to capture the data needed to enable this new paradigm, it will be necessary to deploy a vast array of sensors. In an industrial installation, design engineers face an additional consideration: the impact harsh environments will have on sensitive electronic components.

Because of the added challenge presented by harsh environments, there will also be new opportunities in the way the data is generated, gathered and analyzed. According to the Wall Street Journal, General Electric’s (GE) jet engine business has reported it expects to ‘reap $1 billion in added productivity from its operations as more factory and design processes are fed into digital systems that improve collaboration and speed up production cycles’. It is also turning terabytes of performance data into cost savings, partly due to the way it is using that data in the modification of its maintenance and repair schedules. This clearly demonstrates how GE is using data gathered through the Industrial IoT to enable new and better predictive models.

There is a long history of adapting sensitive electronics for use in harsh environments, of course. The oil and gas industry has accrued a lot of experience in developing ‘downhole electronics’, addressing the demands that a particular environment imposes on active and passive components. Amazingly, electronic equipment operating in such an environment must withstand temperatures that can reach 200o C (415o F) and pressures as high as 30,000 PSI. Although extreme, these demands are not unique to the oil and gas industry.

Electronic systems operating in any environment need to be reliable; in a harsh environment that becomes more challenging, and it all starts with the power supply. Integrated circuits now operate from lower voltage rails and are less tolerant of fluctuations.

Power management devices are now required to deliver stable and accurate voltages under the most extreme conditions, often with large fluctuations in load current. These load variations are inherent to harsh environments, where pulse motor control and auto ignition systems are commonplace.

Manufacturers recognize this and are developing solutions that meet the requirements of harsh environments. An example is the Mean Well HEP-100, an industrial power supply designed to operate across a temperature range of -55o C to +70o C. This range of five power supplies accepts an input voltage of between 90VAC and 350VAC, producing output voltages of 12V, 15V, 24V, 36V, 48V or 54V with an efficiency of 94%.

These AC/DC switching power supplies offer either 100W, 150W, 185W, 240W or 320W total output power; the 320W version can be used in a factory automation environment to power PLCs (programmable logic controllers), or in a telecommunications center powering server cards with high on-time duty cycles, for example. Each power supply also includes short-circuit, over-voltage and current overload protection and can withstand supply surges up to 6kV.

Figure 1

 Mean Well HEP-100 block diagram

Mean Well HEP-100 block diagram

The value of the power management sector (which includes voltage regulators, motor drivers, and pulse and spark generators) is now driven primarily by the industrial control market, according to some leading market researchers. It is now larger than the previously dominant market – computer power supplies. This means more power management ICs and modules are consumed by the industrial control market than all of the computer sector; however, they are each worth in the region of $3.5 billion to the semiconductor market per year.

Although similar in value, these end-markets have very different requirements in terms of the voltage levels required. Industrial power management devices are operating at much higher voltages than their computer, communication and data center counterparts. This has its own challenges in terms of energy transfer efficiency and waveform control. A typical application would be a power supply connected to a 3-phase 220VAC supply. In this situation, all components must be rated for at least 600VAC. Even with high conversion efficiency, this increases the complexity associated with maintaining precision and introduces the need for large heat sinks to dissipate the heat generated during conversion.

Standardized protection

It is common for electronic devices designed for harsh environments to comply with the most stringent specifications possible. But despite being able to operate in temperatures that range from -40o C to 125o C, sensitive electronic devices still need to be protected from other hazards in the environment, which may take the form of solids or fluids. Engineers will be familiar with these standards, as they define the amount of protection an enclosure can provide under specific conditions.

An ECU (engine control unit) will likely be exposed to hazards such as humidity, oil, and water, as well as heat and vibration. This kind of protection is covered by specifications such as the IP code IEC 60529. For example, the standard IP68 (expressed as ‘six eight’, not ‘sixty eight’; each number has a specific meaning) defines an enclosure that can withstand permanent immersion in a liquid to a depth of up to three meters and offers complete protection against dust.

The range of HEP-100 power supplies has been designed to offer IP68 protection; its components are potted in a heat-conductive silicone compound. This means it is completely sealed and can withstand up to 10G of vibration. This makes it perfect for outdoor telecommunications equipment, as well as for use in other hazardous areas such as petroleum plants and mine shafts.

The level of protection required, based on the environmental conditions, will define which standard an enclosure should meet. The standards published by the NEMA (National Electrical Manufacturers Association) cover a range of conditions. For example, cellular base stations will often be designed to meet NEMA Type 4X, while NEMA Type 3 provides protection from the ingress of water in its various states. A NEMA Type 1 enclosure will provide protection for workers against falling debris, and the Association has standards covering Building Systems, Commercial Products, Connected Systems, Industrial Products & Systems, Lighting Systems, Medical Imaging and Utility Products.

Integrated solutions

Electronics developed for the automotive market represent a prime example of how harsh environments can be tamed. Infineon Technologies is a leader in supplying semiconductors to the automotive market and its portfolio includes power management devices. An example is the TLF80511EJ LDO Linear Regulator, which offers all the benefits of a conventional regulator (such as low quiescent current, just 38 μ A) with AEC qualification. It uses a series pass topology and is designed for load currents of up to 400mA.

With an extended operating temperature range of -40o C to 150o C it is perfect for automotive applications, while its low-power design means it can be permanently connected to a battery without risk of draining it. This makes it ideal for a range of automotive applications, including instrument clusters as well as ECUs, and engines that employ the latest start-stop technology.

Figure 2

Block diagram of Infineon's TLF80511

Block diagram of Infineon’s TLF80511

Integrated devices developed for harsh environments often include on-die temperature sensors, and that’s also true for power management devices. For example, the SB0410 from NXP Semiconductor is a complete motor controller on a chip, developed for industrial applications. This SoC integrates a quad valve and pump controller with four low-side regulated solenoid drivers, as well as a high-side PWM (pulse width modulator) to drive a DC motor (using external power MOSFETs). The PWM can drive a pulsed motor at up to 5kHz.

Figure 3

SB0410 simplified internal block diagram

SB0410 simplified internal block diagram

Conclusion

Designing electronics to operate in harsh environments is challenging, and the future of the Industrial IoT and all the benefits that can bring in terms of efficiency and productivity will rely on OEMs meeting that challenge. Fortunately, while the IoT is still emerging, the use of electronics in harsh environments is well established. There exists a wide range of solutions perfectly suited to even the most extreme conditions, and support is available to help engineers find the solution that meets their specific needs.

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