September 05, 2019
| By: Anthony T. Huynh
Principal Member of the Technical Staff, Applications, Industrial Power, Maxim Integrated
Thanks to modern control and automation techniques and technologies, smart buildings can yield significant energy savings, protect the environment, improve the health and safety of their occupants, and enhance quality of life.
Automation systems allow building operators to manage larger buildings remotely, via the cloud. Their software platforms provide real-time performance monitoring, data analytics, visualization, fault detection and diagnostics, and portfolio energy management. By networking the equipment data to the cloud, analytics can be run in real time using advances in artificial intelligence (AI) to determine the action to be taken. The most prevalent use of automation in buildings is in HVAC (heating/ventilation/air conditioning), lighting, monitoring, access control, fire detection, and closed-circuit television (CCTV) surveillance systems.
Building automation system architecture includes different layers for management, control, and the field. From a central location, the management layer operates and controls the smart building and records and optimizes data as needed. Since problems are identified in real time, action can be taken right away. This layer uses network protocols like BACnet and Modbus.
Figure 1. Building automation technologies create comfortable, energy-efficient environments.
The control layer (the building automation block shown in Figure 2) deals specifically with the building’s equipment control at the hardware level and uses decentralized protocols like KNX and LonWorks. At the field layer, intelligent sensors and actuators collect data and perform tasks. For example, the system can sense the lighting level and automatically adjust it to match the time of day or provide shading to ensure optimal use of natural light without glare.
Figure 2. Smart Building System
Advances in hardware and software make all of this intelligence, networking, and control possible. At the field level are controllers, sensors, I/Os, and actuators. A controller can be a programmable logic controller (PLC), motor/motion controller, or a distributed control system (DCS) using advanced processors and microcontrollers. Sensors can be either digital or analog and used to measure temperature, humidity, ventilation, and occupancy. Actuators can be used in locks, window alarms, security camera positioning, solar panels, blinds, and other moving mechanisms. In a modern building, sensors and actuators can communicate on wire or wireless gateways to the control center. They are powered by batteries or wired DC voltages, typically in the 5V to 24V+ range.
The controller receives inputs from sensors on the field, processes them, and drives the proper actuators. Today’s sensors and actuators are equipped with internal processors that make simple decisions locally without escalating to the controller, which improves throughput.
With the proliferation of intelligent, internet-connected equipment in the smart building comes a demand for more processors and connectivity interfaces in every controller, sensor, and actuator in the field. This, in turn, places new requirements on system hardware: reduced component size to fit additional electronics in the same chassis, improved energy efficiency to perform within the same or lower thermal budget, and increased electrical/mechanical safety and reliability to reduce downtime.
The miniaturization that drives demand for smaller PCB sizes creates thermal dissipation challenges. The power-supply solution must, therefore, be extremely efficient as it delivers higher power while occupying a smaller area. Sensor and actuator applications are often characterized by a 24V nominal DC voltage bus. However, the maximum operating voltage for industrial applications is expected to be 36V to 40V for non-critical equipment, while critical equipment, such as controllers, actuators, and safety modules, must support 60V (IEC 60664-1 insulation and 61508 SIL standards). Popular output voltages are 3.3V and 5V with currents varying from 10mA in small sensors to tens of amps in motion control, CNC, and PLC applications. This makes a step-down (buck) voltage regulator the obvious choice for building and industrial control applications (Figure 3).
Figure 3. Fully Integrated Synchronous Buck Converter
Another important question to address as sensors become more commonly used is: how do you safely deliver low-voltage power to tiny sensors, while minimizing solution size and maximizing efficiency? Sensors, which detect and diagnose many parameters and make decisions, must be durable and reliable regardless of the environment. The sensor “box” is powered by a voltage regulator, which delivers the appropriate voltage to the ASIC/microcontroller/FPGA, analog front-end (AFE), and the sensing element.
The sensor is typically powered by a 24V DC power source. However, a building can be a very challenging environment in which to install sensors, which require long cable connections to the power source that result in high-voltage transients. Accordingly, the step-down converter inside the sensor must withstand voltage transients of 42V or 60V, which are much higher than the sensor operating voltage. As noted previously, for 24V rails, it is best to rely on devices that have an operating maximum of 42V.
According to SELV/FELV regulations, input voltages below 60V are considered inherently safe to touch, but the need for isolation in this operating range is still pervasive for functional safety and reliability reasons. In this voltage range, the power-supply electronic load, typically a very delicate and expensive microcontroller, needs protection. If inadvertently exposed to high voltage, this electronic load could potentially self-destruct. Isolation is also beneficial in preventing ground loops, which could trigger reactions that degrade equipment reliability.
Protection circuits are the unsung heroes of today’s electronics. They can help guard against stressors that can damage electronic loads, such as inrush and reverse currents, overvoltages, and undervoltages.
In summary, building automation technologies are resulting in more comfortable, energy-efficient homes and offices. But these technologies are also introducing challenges in energy efficiency, miniaturization, and system reliability. Power management ICs can help address these challenges. For a deeper dive on this topic, read the Power Management for the Smart Building design guide. A similar version of this blog appeared on Electronic Design earlier this year.