The safety and reliability of power supply systems, including power supplies, is the key to ensuring all power-up products. Therefore, it is understandable that engineers pay special attention to the power supply and circuit protection of power supply systems. The concept of smart home has gradually been accepted by most consumers, and it has begun to take the initiative to understand the hot-selling smart home products in the market. Smart home consists of the following aspects: lighting, socket control system; background music system; electric curtains, electric windows and doors, etc.; audio and video systems; security systems; integrated wiring systems. The power supply system is the heart of all these intelligent devices, and it is the guarantee for the normal operation of each control system. This article is a selection of power protection devices to analyze the design ideas of the circuit protection solutions for smart home power supply systems.

First, we all know that power is used to convert electrical energy from one form to another in order for the device to function properly. Common examples of power supplies include: AC to DC converters that convert AC voltage to a stable DC voltage; DC to DC converters that convert battery power to a desired voltage level. The power supply of the smart home mainly supplies power to the main control circuit, signal isolation and display circuit. The power solution is to add a surge protection circuit at the input port to ensure the reliability and stability of the power circuit operation.

Inter-industry coordination and standard unification are still not mature enough. This requires that only the home system should consider the safety features of the product. In addition, the installation and wiring of the smart home may be one-off, so the system is preferably very high. Reliability, timely protection against lightning surges, grid overvoltages, static electricity, etc. that may occur during application. In practical applications, the power interface and signal interface of the smart home system are highly vulnerable to overvoltage and overcurrent faults such as lightning surges, grid voltage fluctuations, static electricity and aging short circuits, and wiring errors, resulting in system failure or damage. In order to improve the safety and reliability of the system, it is necessary to consider the protection of its corresponding interface in the design.

After understanding the main points of protection, it is necessary to understand the circuit protection components used in the surge protection circuit. The circuit protection device used for power protection has SOCAY Shuo Kai's lightning protection voltage limiting ceramic discharge tube and TVS diode. , varistor, and overcurrent protection device PTC self-recovery fuses, etc., ceramic discharge tube, TVS diode and varistor are all overvoltage devices, the following are the key points:

The following four points should be noted in the selection of overvoltage protection devices:

1) Selection of the shutdown voltage Vrwm. Generally, the shutdown voltage is at least 10% higher than the maximum operating voltage of the line;

2) Selection of clamp voltage VC. VC refers to the voltage passing through the TVS in the ESD strike state, which must be less than the maximum transient voltage that can be withstood by the protected circuit;

3) Selection of surge power Pppm. Different power, different protection time, such as 600w (10/1000μs); 300W (8/20μs);

4) Selection of the interelectrode capacitance. The higher the operating frequency of the protected components, the smaller the capacitance of the TVS is required.

Particular attention should be paid to the selection of TVS diodes. Since TVS diodes are divided into one-way and two-way, engineers must choose to use two-way or one-way TVS according to different application interfaces. The DC power interface generally uses a one-way TVS; the AC power interface and the communication interface generally use a two-way TVS.

PTC self-recovery fuse selection points:

1. Keep the current slightly larger than the normal operating current of the user.

2. Vmax should be greater than or equal to the user's maximum operating voltage.

3. Imax is greater than the maximum fault short-circuit current.

SOCAY circuit protection components provide protection against short-circuit and overload conditions. They offer a wide range of choices in form factor, current rating, voltage rating, current interrupt capability and mounting options, providing design engineers with flexibility in design.

A metal oxide varistor (MOV) across the power supply input provides overvoltage clamping protection. They are cost effective and minimize transient power that may pass into downstream electronics. The choice of metal oxide varistor is based on a range of parameters including rated voltage, peak pulse current, device size, and wire configuration.

MOVs and fuses need to form a coordinated solution so that the power required to blow the fuse element (also known as the “i2t” value) is high enough to allow the MOV to function under surge conditions without the fuse Tripped. In other words, the fuse should not be opened under the conditions of surge energy dissipation and dissipation. It should only trip when an overload or short circuit condition occurs.

Even with a varistor in the AC input, there are instances where the circuit is not immune to surge events. In these cases, a TVS diode can be added to the input circuit of the inverting pole. This TVS diode provides secondary protection for transients. The "permitted pass" of electrical energy from the varistor will be further reduced by this TVS diode to a level that will not cause the circuit to fail.

With a wide product line and excellent customer service capabilities, Shuo Kai Electronics meets the needs of design engineers and procurement personnel through the latest generation of advanced technology products. We have a state-of-the-art EMC laboratory, and professional FAE engineers follow-up to provide customers with the latest design projects to provide the highest level of protection and high-level circuit protection solutions and circuit protection components. The company's official website is updated daily. has a complete product catalog, data sheet, industry information, application solutions, testing services, etc. More online customer service is always available for customers to answer questions.

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