Power Solution for Smart Home Controller


With the rising of living standard, people have new requirements of security, intelligence, comfort, beauty, and entertainment in housing. Smart home is the one to meet these demands. Based on the house, smart home integrates the facilities related to family living by technologies of generic cabling, internet communication, security, automation, audio and video to improve the living circumstance and save energy at the same time. The power supply system is the core of these facilities and the foundation to ensure each control system well running.

Smart home structure

We can get a clear idea that smart home is consisted of lights, power socket control system, background music system, electronic door and curtain, audio-visual system, security system, generic cabling system, etc. Because of the compact of the residential houses, the controllers of these systems have the general character- compact size, as small as the common power socket.

Therefore, the power supply for these controllers also should be small in size to meet the layout requirement of the controller. Moreover, it will be more convenient for people to decorate the house to be beautiful and comfortable with these compact controllers and panels.

Smart Home
Figure 1: Illustration of smart home structure

Two common solutions of power supply

Among the traditional design solutions of power supply in controller circuit, the most common solutions are: RC (resistance-capacitance) step-down and the industrial frequency transformer step-down. We will talk about the features of these solutions with pic 2 and pic 3.

Illustration of RC step-down circuit of the controller panel is shown as pic 2. We know that the power supply is for the main controller, signal-isolation, and display circuit. The solution shows that, a surge-protection circuit at input side is to ensure the reliability and stability of the power supply circuit, and then the RC step-down circuit converts the voltage, finally using LDO to get regulated voltage to supply for MCU and signal isolation. And the output over-current detection circuit will protect the back-side load when the power supply works abnormal.

Pic 2 illustration of power supply solution for RC step-down structure
Pic 2 illustration of power supply solution for RC step-down structure

The advantages of this solution are low cost and small area occupation on PCB, which are the exact demands of smart home. While, the disadvantages are: 1) low efficiency, 2) narrow range of input voltage, 3) value of load is easy to be affected, 4) uneasy to test the circuit. The worst point is the non-isolation between the input and output. It may easily lead to electric shock which may cause harm to personal safety.

Illustration of industrial frequency transformer step-down circuit of the controller panel is shown as pic 3. Input and output circuits are same as RC step-down solution as both of them need to protect the voltage and back-side load. The difference is that the power is converted by transformer. Supplying by AC input with frequency of 50HZ Transformer step-down the input power, and then using rectifier and filter circuit and LDO to get a regulated voltage for the load.

Figure 3
Figure 3: Illustration of power supply solution for frequency transformer step-down structure

The advantages of this solution are: 1) easy to test, 2) simple in circuit structure, 3) safety level upgraded as the input and output is isolated by transformer, and 4) lower cost. Its disadvantages are 1) limitation of input range, 2) bulky in size and low in efficiency, which is against the demands of smart home as compact size and energy-saving.

A typical AC/DC power module for smart home

The above two solutions have different disadvantages. RC (resistance-capacitance) step-down circuit may cause harm to personal safety and the industrial frequency transformer step-down circuit don’t satisfy the request for compact size and energy-saving. To eliminate the disadvantages, Mornsun provides high efficiency green AC/DC power modules with miniature packaging LS series for smart home applications.

Figure 4: Illustration of switch power supply solution structure
Figure 4: Illustration of switch power supply solution structure

LS series is not only compact in size, but also with protections as over-load, short circuit and over-current and compliant with CE and UL. Meanwhile, it only needs to add an extra filter capacitor at both the input and output by following the recommended circuit, then can make the LS series available for both AC input and DC input. The series can also be used in power instrument and other industries, convenience for engineers to design and layout.

Advantages of LS series

LS series achieves an isolated regulated output with compact size and energy-saving that RC step-down circuit and industrial frequency transformer step-down circuit can’t. As the LS series is controlled by high frequency, the internal transformer can be tiny, which making LS series compact to eliminate the disadvantages of the former two traditional solutions.

Courtesy Mornsun