AC/DC Converter LS Series for Smart Home Controller

Abstract: 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. It is one kind of high efficiency management system combined the house facilities and home agenda. Based on the house, smart home integrates the facilities related to family living by technologies of generic cabling, internet communication, security, automation, and audio & 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.

Key words: smart home micro-power  AC-DC power supply module

smart home structure
Pic1 illustration of smart home structure

Illustration of smart home structure is shown as Pic 1. 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.

The cooperation of the solutions
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 2 solutions with pic2 & pic3.

Illustration of RC step-down circuit of the controller panel is shown as pic 2. We can 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. 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.

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

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. 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.

frequency transformer step-down structure
Pic 3 illustration of power supply solution for frequency transformer step-down structure

Illustration of switch power supply solution structure is shown as pic4. Base on specification of switching power supply, you can get regulated output along with protections as over-load, short circuit, etc. It has the features of simple periphery circuit, high efficiency and multi-protection. As the switching power supply is controlled by high frequency, the internal transformer can be tiny, which making the whole switching power supply compact to cover the disadvantages of the former two traditional solutions.

switch power supply solution structure
Pic4 illustration of switch power supply solution structure

A typical switching power supply product for smart home
LS series —– are high efficiency green power modules with miniature packaging provided by Mornsun. The features of this series are: wide input voltage, DC and AC optional, high efficiency, high reliability, low power consumption, safety isolation etc.

All models are particularly suitable for the applications like industrial, electric power, instrumentation, smart home, etc.

Smart Home ControllerFeatures
1. Wide input voltage: 100 ~ 400VDC (85 ~ 264VAC)
2. Over current protection and short circuit protection
3. High efficiency, high density
4. Low power consumption, green power
5. Ultra-Miniature package
6. Meet UL60950/EN60950 standards

Basic operating principle
The product image is shown as pic5. When power on, the input voltage passes pin1 and pin3, and reaches to the power transformer after rectified and filtered; under the control of high voltage switch and controller, the energy is transmitted from the primary to the secondary, then turns to the request output voltage after the rectifier and filter circuit. When there is abnormal situation at the back-side of the output makes over current or short circuit, the controller will turn off the output voltage when detecting the abnormal. Output will be self-recovery when over current or short circuit disappears.

smart curtain controller structure
Pic6 Illustration of smart curtain controller structure

Switch power supply used in smart curtain controller
The illustration of the compact switch power supply used in smart curtain controller is shown as pic6, the system operates as below:
Input: On the one hand, the power is supplied by main which is not so stable and normally with the fluctuation of ±10%, and it will even be seriously enlarged to ±30% in some remote area. So it requests the switch power supply with a wide input voltage range. The operation voltage range of LS03-15B05SR2 is 85~264VAC, which can cover the fluctuation and prevent the product not be affected. On the other hand, the power grid may supply for several equipments at the same time. If the equipments are with high power, then when high power equipment power-on or works, it will probable interfere other equipments similar as surge or transient bursts of EMC. So it is suggested to add protection circuit at the input to prevent the product from the interference.
Output: As the product LSO3-15B05SR2 holds the functions of over current protection and short circuit protection, so it is no need to add protection circuit at the output. The product can supply the power to load circuit directly, then processor receives the signal with button or wireless, and then transmit the controlling information to the relays through optical coupler or other isolators, so that to control the curtain by motor.


The untiring effort of Mornsun engineers give birth to the AC/DC power supply module of LS series not only compact in size, but also 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 LS01-XX/LS03-15BXXSR2 available for both AC input and DC input. The series can be used in power instrument, smart home and other industry, convenience for engineers to design and layout. Based on the principles of remarkable progress of technology or application, creation of design, and high cost-effective, LS series is listed Top10 in the awarding activity of power products which is hold by Electronic Products China which is sponsored by China Ministry of Information Industry and International Data Group (IDG). Mornsun is also awarded self-renovation as the technology of LS series is the first one to win such honor which is significant important for China domestic technology.

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