PCB News - The following points should be paid attention to in the ground wire design

In the PCB design, the following points should be paid attention to in the ground wire design

1. Correctly choose single-point grounding. Generally, the common end of the filter capacitor should be the only connection point for other grounding points to couple to the AC ground of high current. It should be connected to the grounding point of this level. The main consideration is that the current returning to the ground in each part of the circuit is changed. The impedance of the actual flowing line will cause the change of the ground potential of each part of the circuit and introduce interference. In this switching power supply, its wiring and the inductance between the devices have little influence, and the circulating current formed by the grounding circuit has a greater influence on the interference. Connected to the ground pin, the ground wires of several components of the output rectifier current loop are also connected to the ground pins of the corresponding filter capacitors, so that the power supply works more stably and is not easy to self-excite. When a single point is not available, share the ground Connect two diodes or a small resistor, in fact, it can be connected to a relatively concentrated piece of copper foil.

   

2. Thicken the grounding wire as much as possible. If the grounding wire is very thin, the ground potential will change with the change of the current, causing the timing signal level of the electronic equipment to be unstable and the anti-noise performance to deteriorate. Therefore, ensure that each large current grounding terminal Use printed lines as short and wide as possible, and widen the width of the power and ground lines as much as possible. It is better to make the ground line wider than the power line. Their relationship is: ground line>power line>signal line. If possible, ground line The width should be greater than 3mm, and a large area of copper layer can also be used as a ground wire, and the unused parts on the printed circuit board are connected to the ground as a ground wire. When performing global wiring, the following principles must also be followed:

(1). Wiring direction: From the welding surface, the arrangement direction of the components should be as consistent as possible with the schematic diagram. The wiring direction should be consistent with the wiring direction of the circuit diagram, because various parameters are usually required on the welding surface during the production process. Therefore, it is convenient for inspection, debugging and maintenance in production (Note: It refers to the premise of meeting the circuit performance and the requirements of the whole machine installation and panel layout).

(2). When designing the wiring diagram, the wiring should be turned as little as possible, the line width on the printed arc should not be abrupt, the corner of the wire should be ≥90 degrees, and the lines should be simple and clear.

(3). Cross circuits are not allowed in the printed circuit. For the lines that may cross, you can use "drilling" and "winding" to solve the problem. That is, let a lead "drill" through the gap under other resistors, capacitors, and triode pins, or "wind" from one end of a lead that may cross. In special circumstances, how complex the circuit is, it is also allowed to simplify the design. Use wires to bridge to solve the cross circuit problem. Due to the single-sided board, the in-line components are located on the top surface and the surface-mount devices are located on the bottom surface, so the in-line devices can overlap with the surface-mount devices during layout, but overlap of the pads should be avoided.

3. Input ground and output ground This switching power supply is a low-voltage DC-DC. If you want to feedback the output voltage back to the primary of the transformer, the circuits on both sides should have a common reference ground. Therefore, after laying copper on the ground wires on both sides, you must Connect together to form a common ground

The above is the introduction of the following issues that should be paid attention to in the ground wire design. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.