Set-Top Box Protection Solution

Set Top Box (STB) is a device that connects a TV to an external signal source. It converts compressed digital signals into television content and displays them on the television. From the simple functional set-top box that initially only received digital TV signals to today's various set-top box high-definition players with many functions, with the development of set-top box technology, today's set-top boxes can complete many high-definition, interactive, multi-mode, and multi-format data support. decoding. In terms of interfaces, in order to obtain more data sources, equipment generally provides many types of choices, and generally supports USB, HDMI, Ethernet interfaces, hard disk interfaces, etc.

The support of different types of interfaces makes today's high-definition players increasingly powerful in entertainment functions, but it also brings many requirements for the protection of different interfaces. We know that interfaces of various data types are susceptible to many fault conditions such as overvoltage, overcurrent, static electricity, etc. during the hot swapping process. Manufacturers of set-top boxes and high-definition players must take different unexpected factors into consideration during the product design process. , and adding corresponding protection to the input end of the interface can reduce the repair rate of the product and provide customers with a good user experience. Next, we will take a look at these common interfaces on set-top boxes to see what protection devices can be used to protect the equipment well.

The first is the USB interface. Whether it is USB2.0 or the increasingly popular USB3.0, the USB interface is our most common and widely used data interface. In the process of convenient use, we often encounter some fault conditions, the more common of which is damage to the USB master device due to short-circuit failure of the USB slave device. Using PPTC (resettable fuse) devices is a cost-effective solution Protection scheme: In the short-circuit fault state, the PPTC device can quickly change from a low-resistance state to a high-resistance state, thereby limiting the current to protect the USB device. Another common USB fault is caused by static noise. During the hot plugging process, the impact of static electricity is very obvious. To reduce the impact of static electricity on the circuit, we can use ESD (silicon-based ESD protection devices) ), the ESD device has low capacitance, low clamping voltage, high ESD resistance energy and small package size, making it an ideal choice for USB interface electrostatic protection. Figure 1 below is a typical application of using PPTC resettable fuse and ESD electrostatic protection on a USB port.

HDMI is also a very popular multimedia signal interface nowadays. Similar to the USB interface, the HDMI interface is also susceptible to various fault conditions such as short circuit, overcurrent, and static electricity during use. Similarly, we can use PPTC self-restoring fuses and ESD static electricity to Protect the interface from failure. As shown in Figure 2, a PPTC resettable fuse is used on the power line of the HDMI port for overcurrent protection, and multi-channel ESD is used on other signal lines to protect against static electricity.

Many set-top box devices have DC power input ports and need to be powered by AC/DC adapters. There are too many devices in our lives that require similar adapters. Different adapters may have different power supply voltages, powers, and even power supplies. Positive and negative polarity, incorrect use of the adapter will cause serious damage to the equipment, and the peak noise formed during the plugging and unplugging process of the adapter will also cause damage to the load circuit. For protection similar to power ports, the PPTC resettable fuses and TVS transient suppression diode series devices of the Yintek Circuit Protection Department, as surface-mounted independent devices, can simultaneously complete overvoltage, overcurrent, power misconnection, and power supply. Reverse connection and other multi-faceted protection. The small size design makes it very suitable for thin and compact environments with limited space. In a fault state, the TVS diode can quickly and effectively clamp the voltage and shunt the fault current, and the PPTC resettable fuse assembly can then quickly switch off. interrupts excessive current, helping to protect the TVS diodes and downstream electronic components. Figure 3 below describes a typical application of DC input port protection.

For the RJ45 port on the set-top box device, considering the equipment damage caused by static electricity during frequent plugging and unplugging, ESD devices can also be added to the port to protect against electrostatic interference. Figure 4 shows the application of using ESD devices for protection on 10/100baseT and 1G Ethernet respectively.

For xDSL ports on set-top boxes, consider using a circuit with a gas discharge tube (GDT) device combined with a PPTC device to protect the device. GDT devices can be used in the primary protection of circuits and can play a role in transient overcurrent and limiting overvoltage in lightning protection, while PPTC devices can be used in power line touch protection and play a very good role in overcurrent faults. protective effect. The circuit in Figure 5 is a typical application using PPTC resettable fuse and GDT gas discharge tube device for lightning strike and power line touch protection.

To sum up, today's set-top boxes can already provide a variety of multimedia entertainment functions. At the same time, we are also paying attention to the fact that devices need to support multiple data interfaces to help obtain various multimedia data resources. How to better provide The protection of these interfaces is key to whether the device can provide customers with a good experience.