In the design of power adapters, one of the most commonly used methods is floating ground technology. In this method, the signal ground of the circuit board is not connected to the external public ground, thereby ensuring good circuit isolation.
In floating ground technology for car ac power adapters, the circuit is well isolated from the external ground system and is not easily affected by the interference of external system. However, static electricity is easy to accumulate on the circuit, causing static electricity interference, and dangerous voltage may be generated. Small-scale low-speed (<1mhz) equipment can adopt the method of floating ground in working ground (or single-point connection of the working ground to the metal shell), and single-point connection of the metal shell to the ground.
Series single-point grounding is a more recommended grounding method. Because of its simplicity, there is no need to pay so much attention to the circuit board design, so this method is more used. However, this kind of circuit is prone to common impedance coupling, so that each circuit module affects each other.
Parallel single-point grounding can get rid of the problem of common impedance coupling that series single-point grounding has, but in actual use, it will introduce too many grounding wires. As for which one to use, it needs to be comprehensively evaluated in the actual process. If the circuit board area allows, use the parallel mode, and if the connection between the various circuit modules is kept simple, then use the series mode.
Generally, there are power adapter modules, desktop ac adapter modules, analog circuit modules, digital circuit modules, and protection circuit modules in the downloaded board. In this case, the method of parallel single-point grounding is adopted.
Multi-point grounding technology is used more in daily design, and more used in multi-module circuit design. This grounding method can effectively reduce the problem of high-frequency interference, but it is also prone to design problems of ground loops, This point must be fully considered in the design to improve the stability of the system design. To choose a professional power adapter manufacturer is a good way for solving these problems.
The working ground of small high-speed (>10MHz) equipment should be grounded at multiple points with its metal casing, the distance between the grounding points should be less than 1/20 of the wavelength of the highest operating frequency, and the metal casing should be connected to the ground at a single point.