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What should be the ground design of a power adapter

In power adapters, grounding is an important method of suppressing interference. If the grounding and shielding can be used correctly in combination, most of the interference problems can be solved. electronic equipment in the ground structure is roughly the system ground, chassis ground (shielding), digital ground (logic ground) and analog ground, etc. In the ground design of the power adapter should pay attention to the following points.

1. the correct choice of single-point grounding and multi-point grounding. in low-frequency circuits, the signal operating frequency is less than 1MHz, its wiring and the inductance between the device has less impact, and the formation of grounding circuits have a greater impact on the interference, and thus should be used as a point of grounding. when the signal operating frequency of more than 10MHz, the ground impedance becomes very large, at this time, should try to reduce the impedance of the ground line should be used in close proximity to the grounding of the multiple. when the operating frequency of 1~10MHz, the ground impedance becomes very large, at this time should try to reduce the impedance of the ground line should be used in close proximity. Operating frequency of 1 ~ 10MHz, if the use of a point of grounding, the length of the ground should not exceed 1/20 of the wavelength, otherwise it should be used multi-point grounding method.

2. digital and analog circuits are separated. circuit boards have both high-speed logic circuits, and linear circuits, they should be separated as far as possible, and the two ground should not be mixed, respectively, with the power supply end of the ground connected to the circuit board to maximize the grounding area of the linear circuits.

3. try to thicken the grounding line. if the grounding line is very thin, the ground potential changes with the current changes, resulting in electronic equipment, timing signal level instability, anti-noise performance is bad. therefore, the grounding line should be as thick as possible, so that it can pass three times the permissible current located in the printed circuit board. if possible, the width of the grounding line should be greater than 3mm.

4. will be grounded to form a closed loop. design only by the digital circuitry of the printed circuit board ground system, will be grounded into a closed loop can significantly improve the anti-noise capability. the reason is: printed circuit boards have a lot of integrated circuits components, especially in the case of power-consuming components, due to the limitations of the thickness of the ground wire will produce a large potential difference in the ground, resulting in a decline in anti-noise capability, if the grounding If the grounding structure into a loop, it will reduce the value of the potential difference, improve the noise immunity of electronic equipment.

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