Protection account in switch power supply design-grounding Treatment

Nowadays, switching power supply has replaced linear regulated power supply and is active in the electronic power design field. People gradually realized that the switch power supply has changed the technical direction of the electronic design industry. In the power supply design, safety is always the first priority. In the switch power supply, grounding can protect the user's personal safety and ensure the normal operation of power equipment, so what is the proper grounding method in the switching power supply? What are common grounding symbols? This article will introduce the grounding problem in the switch power supply.

What is the definition of grounding?

In the modern concept of grounding, for line engineers, the term is generally a reference point for line voltage ". For system designers, it is often a cabinet or rack. For an electrical engineer, it is a green ground or connected to the Earth. A general definition is that "grounding is the low-impedance channel for the current to return to its source ". Note that "low impedance" and "Pathway" are required ".

Common grounding symbols

PE, pgnd, FG-protected area or chassis; bgnd or DC-RETURN-DC-48 V (+ 24 V) power supply (battery) reflux; Gnd-work location; dgnd-digital location; agnd-analog site and lgnd-protected area.

What is an appropriate grounding method?

There are multiple grounding methods, such as single point grounding, multi-point grounding, and hybrid grounding. Single point grounding is divided into series single point grounding and parallel single point grounding. In general, single point grounding is used for simple circuits. Different functional modules are ground-differentiated, and multi-point grounding or multi-board (complete ground plane layer) must be used for low-frequency (f10mhz) circuits ).

Why is the switching power supply grounded?

The introduction of Grounding Technology was initially a protective measure designed to prevent lightning strikes on power or electronic devices. The purpose was to introduce lightning strikes produced by lightning to the Earth through lightning rods, this protects buildings. At the same time, grounding is also an effective means to protect personal safety. When the phase line (such as poor wire insulation, line aging, etc.) and the device shell Touch Caused by some reason, the shell of the device generates dangerous voltage, and the fault current generated will flow through the pe to the Earth to protect the device. With the development of electronic communication and other digital fields, only lightning protection and security considerations in the grounding system are far from meeting the requirements.

For example, signals between various devices need a "Ground" as the benchmark reference for signals. With the complexity of electronic devices, the signal frequency is getting higher and higher. Therefore, in the Grounding Design, electromagnetic compatibility issues such as mutual interference between signals must be paid special attention. Otherwise, improper grounding will seriously affect the reliability and stability of system operation. Recently, the concept of "land" has also been introduced in the signal reflux Technology of High-speed signals.

Why do we need to separate analog and numbers?

Both analog and digital signals need to flow back to the ground, because the speed of digital signal changes is fast, so the noise on the digital ground will be very high, analog signals require a clean reference. If the analog and digital fields are mixed together, the noise will affect the analog signal.

Generally, the simulated and numerical locations must be separated and then connected together through thin cabling or single points of connection. The general idea is to try to block the noise from the digital ground to the simulated ground. Of course, this is not a very strict requirement that the simulated and digital locations must be separated. If the simulated numbers nearby are still very clean, they can be combined.

How is the signal on the board grounded?

In general, it is best to use nearby grounding for design, and after a complete multi-board design, it is very easy to ground the common signal, the basic principle is to ensure the continuity of the line, reduce the number of holes, close to the ground plane or power plane, and so on.

How is the interface device of a single board grounded?

Some boards have external input and output interfaces, such as the serial port connector and the network port RJ45 connector. If they are not properly grounded, the normal operation will also be affected, for example, the network port interconnect has an error code, packet Loss, etc., and will become an external electromagnetic interference source, the noise in the board is sent out. Generally, an independent interface location is separated separately. The connection to the signal location uses a thin strip connection, which can be a string of 0 ohm or a small resistance. A thin line can be used to block noise from the signal ground to the interface ground. Similarly, filtering the interface and interface power supply must be carefully considered.

How do I ground the Screen Layer in a cable with a screen layer?

The shield layer of the shield cable must be connected to the interface ground of the Board, rather than the signal ground. This is because of various noises on the signal ground. If the shield layer is connected to the signal ground, noise voltage will drive the common-mode current to interfere outward along the screen. Therefore, unreasonable cables are generally the maximum noise output source of electromagnetic interference.

Modern people's lives are increasingly inseparable from electronic devices, and electronic devices must rely on stable and secure power supply modules. Switch power supply technology has penetrated into various electronic equipment fields. I hope everyone can find their current puzzles in this article and get answers smoothly.

 

Jin shengyang dcdc Power Supply Module www.mornsun.cn

Protection account in switch power supply design-grounding Treatment