In the design of power adapters, the most commonly used method is floating ground technology, where the signal ground of the circuit board is not connected to the external common ground, thereby ensuring good isolation of the circuit. The circuit has good isolation from the external grounding system and is not easily affected by interference from the external grounding system. However, static electricity can accumulate on the circuit and generate static interference, which may generate dangerous voltages. Small low-speed (<1mhz) equipment can use floating ground (or single point metal casing at the working ground) or single point metal casing grounding.

Series single point grounding:

This grounding method is a recommended grounding method by the company. Due to its simplicity, there is no need to pay too much attention in circuit board design, so it will be used more frequently. However, this type of circuit is prone to common impedance coupling, causing various circuit modules to affect each other

Parallel single point grounding:

Although this method of grounding eliminates the problem of common impedance coupling in series single point grounding, it can introduce too many troubles in practical use. As for which method to use, it needs to be comprehensively evaluated in the actual process. If the circuit board area allows, parallel mode is used. If the connection between various circuit modules is kept simple, series mode is used. In general, the downloaded board includes a power adapter module, an analog circuit module, a digital circuit module, and a protection circuit module. In this case, I use a parallel single point grounding method.

Multipoint grounding:

Multipoint base technology is commonly used in daily design, especially in multi module circuit design. This grounding method can effectively reduce high-frequency interference problems, but it is also prone to design issues with ground loops. This design should fully consider this and improve the stability of the system design. The working ground of small high-speed (>10MHz) equipment should achieve multi-point grounding with its metal casing, and the distance between the grounding points should be less than 1/20 of the highest working frequency wavelength, and the metal casing should be grounded at a single point.