As the most important force in the security system, video surveillance technology has an irreplaceable position in improving the comprehensive capabilities of disaster prevention and emergency response, safety production and emergency management. In the disaster prevention and emergency response industry, the application of video surveillance technology is diverse and versatile, adding support to the creation of a three-dimensional prevention and control system.
The video surveillance system is composed of video collection points, video access nodes (type I and II), video area nodes, and video transmission networks. The video access nodes, passenger dedicated line video nodes, and video transmission network systems are shared, and the video collection points And the monitoring terminal can be set according to the needs of each system, and it can also be shared by each system in many occasions.
Cameras installed indoors and outdoors can be used not only to protect the safety of public places (such as apartments and office buildings, factories, school campuses, and personal residences), but also to monitor traffic conditions. In all these cases, the process of connecting and disconnecting cables will be threatened by electrostatic discharge (ESD) and cable discharge events (CDE). Fragile circuits include buttons and switches, memory slots, and video output ports. For cameras installed outdoors, the video (CVBS or SDI) and data (Ethernet, USB) ports will also suffer severe and repetitive lightning transients.
Similarly, video recording hardware (digital hard disk video recorders/personal video recorders) will also be exposed to the threat of ESD and lightning surges. When video recording equipment is connected to the video and data ports, ESD is introduced. In thunderstorms, transients can be introduced into the power supply (AC/DC) circuit and the Ethernet/video port (if connected to a camera installed outdoors).
All these issues are an ever-increasing challenge for hardware designers and manufacturers. As the functions of various devices increase, so does the complexity and sensitivity of chipsets. At the same time, designers also face pressure to reduce costs.
In many cases, in the early design stage, few manufacturers will consider transient protection, which makes the equipment easy to fail, which in turn incurs corresponding maintenance costs and handling problems, and damages its brand reputation. The purpose of protecting the components is to reduce the transient energy to within a safe range, to ensure reliable application performance and prevent the normal operation of the circuit from being disturbed. For example, it must not reduce the high-speed signal by adding additional capacitance or other nonlinear effects.
The most common power protection scheme is to use a bidirectional TVS diode across the input and power supply. The bidirectional diode is chosen to avoid the line voltage regardless of polarity. For powered devices that must be compatible with both power modes A and B, how will the TVS diode be placed in the circuit, because PSE controls the specific implementation. PD needs to be compatible with these two modes at the same time. For those applications that must comply with safety standards such as UL 60950-1, the solution also provides overcurrent protection devices. For more robust protection solutions, SMB, SMC, and SMD versions can be used instead of SMAJ58CA.
In order to ensure that the security system components and network functions are reliable throughout the installation life, transient protection (ESD and surge) should be taken into consideration. In most cases, only basic ESD protection is required, and equipment or cables exposed to open outdoor environments should also be protected from the threat of lightning surges. Power circuits are also affected by transient voltage events and need protection. For all these situations, there are a large number of solutions, which will give circuit board designers more flexibility when designing.
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