Smart homes are becoming more and more popular, and all kinds of electronic products and intelligent systems make our lives more comfortable. For heating, lighting, home appliances, etc., you can control from anywhere with a few smartphone buttons. The necessary data is collected and transmitted by sensors in real time to where they are needed, so these sensors require a reliable source of power.

Until a few years ago, only smart people used smart homes, and with the extensive modifications and rewiring of the original building structure, it was expensive to install the necessary equipment. Smart homes can now buy "off the shelf" directly. Multinational suppliers of Internet of Things (IoT) devices have revolutionized the market. Today, consumers can choose from a wide range of smart devices and solutions that are easy to install and operate, and the price is down

Application and supply

In order to provide people with a comfortable feeling, smart home devices need to exchange data in real time. These data are collected by a number of year-round sensors, so a reliable power supply is required to supply power continuously (as shown in Figure 1). Depending on the application, there are several options: battery power, energy extraction, DC bus or direct connection to the grid. All options have advantages and disadvantages and cannot be discussed in detail here.

Figure 1: Because smart homes have a large number of applications and sensors, they require a reliable power source. Small power supplies can meet this need, but they must meet a variety of highly specific requirements.

Many smart home applications are battery powered, providing extreme flexibility and no need to connect to a power source. However, the life of the battery is limited and must be replaced at some stage. Given the large amount of equipment in the home, replacing these batteries in time can be a time-consuming and damaging job. Energy extraction is a promising option, but current technology is still in its infancy and it will take some time to become a reliable and affordable solution on the market.

In industrial applications, the use of a Din Rail Switching Mode power supply with a stable 24V output is a recognized standard. However, this DC bus system is not a standard for office buildings or residential buildings, and the installation cost is usually very expensive.

Small modules that power sensors and other devices are more affordable. They are mounted near the application like a battery and are powered by the mains so they never lose power.

Power requirements in smart home applications

Power supplies installed in smart homes must meet some very specific requirements. In addition to being affordable, they must be very small, otherwise it is impossible to integrate them into the device. In addition, since the application periodically switches between active mode and standby mode, they must withstand frequently changing load conditions. Smart home devices are usually in standby mode, so the standby power consumption must be as small as possible. Last but not least, they must be fully certified for industrial, commercial and home systems, as this helps end-user devices to pass certification quickly.


Small and well protected

Modern sensors and wireless modules are very small in size, as are power supplies. Only a few years ago, the average size of 5W power supplies was 2" x 1" (50.8mm x 25.4mm), now they are reduced to 1" x 1" (25.4mm x 25.4mm) (Figure 2). As a result, modern power supplies can be easily integrated into ultra-small smart home devices. This very high power density is achieved by primary side regulation (PSR). Of course, small power supplies must be as safe and reliable as before, which is why they must have proper short-circuit and over-voltage protection, and must also meet residential EMC standards. In order to reduce costs, some manufacturers have eliminated integrated EMC filters at design time, which has led to the integration of these filters into devices, not only to make them larger and more expensive.

Figure 2: Smart home applications require a small power supply for easy integration into sensors and control devices. The picture shows the difference in size between RECOM's power supply introduced a few years ago and the latest generation of modules. Both provide 5W of power.

The load fluctuates every day

Power supplies for smart home applications often experience changes in load conditions. For example, the GSM module requires up to 2A of current when transmitting an SMS or communicating with a base station, and drops to 1.5mA when it is in standby. This means that the power supply must be able to handle sudden load changes without causing extreme voltage spikes. In this case, transient behavior is also an important issue. Most AC/DC specifications only describe the control mode when the load changes from 50% to 75%, which obviously has little to do with smart home applications because of the 0% to 25% variation for these applications. It is really important. In an ideal situation, the stabilization time should be 500 μs or less.

Typical sensor applications mostly operate in intermittent mode because most of the time is in energy saving or sleep mode. The European ErP (Energy-Related Products) Directive stipulates that the standby power consumption of PCB-mounted power supplies and integrated power supplies is less than 500mW. Considering that smart home and IoT applications will become increasingly popular, and there will be a large amount of power to power them, this standby power consumption is still too high. The optimal standby power consumption should be less than half of 500mW. However, low standby power is not the only problem. Many IoT and smart home applications work at very low load ranges, or frequently switch from zero to low load. Even though the specification states excellent zero-load power consumption, the facts may be very different at low loads. This is because the controller automatically switches to pulse mode to save energy when it is at zero load. It will switch back to normal operating mode as soon as the minimum load is applied.

Smart home power supply

All in all, the future of smart home technology will bring new challenges in power supply. Therefore, developers need to carefully review the specifications of the power supplies they design, otherwise they may find it too late to meet the expectations of the selected modules.

Figure 3: RECOM recently introduced a new line of small AC/DC power supplies designed for smart home and IoT applications.

RECOM offers tailor-made 1-10W AC/DC power supplies for the specific requirements of smart home and IoT applications. The new RAC-G series was developed specifically for efficient, long-term supply of technical building components. Due to their high efficiency and low standby power consumption, they are ideal for energy efficient systems. In addition to the international safety certifications (EN 60950 and EN 62368), these modules are also certified to EN 60335 for residential buildings.

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