USB (Universal Serial Bus) interface circuit

Abstract

The invention provides a USB (Universal Serial Bus) interface circuit which comprises a USB connector, a power common mode filter module, a signal common mode filter module, a power differential mode filter module, a signal differential mode filter module and an electrostatic protection module. Common mode interference, differential mode interference, electrostatic interference and the like on a power line and a signal line in the circuit can be eliminated; particularly, the additionally arranged power common mode filter module can eliminate common mode interference between a power VBUS and a working ground GND; and the circuit is small in size, low in cost and high in practicability, has very good protection effects on electrostatic discharge (ESD) and electromagnetic interference (EMI), allows a USB signal to be free from distortion, and ensures that a product smoothly passes USB certification and EMC (Electromagnetic Compatibility) certification. In addition, a high-voltage protection module and a high-frequency filter module can eliminate high-voltage signal interference and high-frequency signal interference in the circuit, so that the interference resistance of the USB interface circuit is further improved, and the signal transmission performance of the USB interface circuit is improved.

Description

technical field [0001] The invention relates to the technical field of USB interface, in particular to a USB interface circuit. Background technique [0002] Due to the development of multimedia technology, there is a higher demand for the data transmission rate between the peripheral and the host computer, so the USB bus technology emerges as the times require. USB (Universal Serial Bus) is translated into Chinese as Universal Serial Bus, which is jointly researched and developed by companies such as Conpaq, DEC, IBM, Inter, Microsoft, NEC and Northen Telecom to simplify the interconnection between PCs and peripherals. A free standardized connector, which is characterized by fast speed, good compatibility, no interruption, can be connected in series, supports hot plugging, etc. It supports various PCs and scanners, digital cameras, digital cameras, audio systems, monitors, The connection between peripherals such as input devices can also realize digital multimedia integrat...

AI Technical Summary

Problems solved by technology

However figure 1 In the circuit shown, on the one hand, the grounding line is not designed for isolation, which leads to the direct conduction between the working ground GND and the output ground. As long as there is high voltage outside, it will directly enter the internal circuit of the device, causing damage to the machine. The insulation spacing is not enough to meet the requirements of the industry, and the withstand voltage cannot meet the requirements; on the other hand, the action time of diodes D1, D2, and D3 is ps level, while the action time of inductor L1 is μs level. L1 acts before, but because the diode D3 has too little current resistance, it is easy to be broken down, and the inductance L1 loses its protective effect, so that it lacks a common-mode or differential-mode filter protection circuit, which makes it difficult to achieve the desired effect in the end.

Therefore, the current typical USB interface circuit makes electronic equipment have great risks when passing USB certification and EMC certification, USB signals are easily distorted, and USB certification and EMC certification are prone to failure

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