PCB Technical - PCB in power supply design

As a power supply engineer, the most important thing is the PCB design in the power supply design. So what are the points to pay attention to? The editor of Baineng.com brings benefits to everyone, summing up the experience of many power supply engineers, and 5 points that cannot be ignored in PCB production in power supply design.

In the power supply design, only the PCB design process is concerned:

1. First, there must be a reasonable direction:

Such as input/output, AC/DC, strong/weak signal, high frequency/low frequency, high voltage/low voltage, etc... Their direction should be linear (or separated) and must not blend with each other. Its purpose is to prevent mutual interference. The best trend is in a straight line, but it is generally not easy to achieve. The most unfavorable trend is a circle. Fortunately, isolation can be set to improve. For DC, small signal, low voltage PCB design requirements can be lower. So "reasonable" is relative.

2. Choose a good grounding point: the grounding point is often the most important.

A small grounding point, I don’t know how many engineers and technicians have talked about it, which shows its importance. Under normal circumstances, a common ground is required, such as: multiple ground wires of the forward amplifier should be merged and then connected to the main ground, etc.... In reality, it is difficult to achieve this completely due to various restrictions, but we should try our best to follow it. This question is quite flexible in practice. Everyone has their own set of solutions. It is easy to understand if it can be explained for a specific PCB circuit board.

3. Reasonably arrange power filter/decoupling capacitors.

Generally, only a number of power filter/decoupling capacitors are drawn in the schematic diagram, but it is not pointed out where they should be connected. In fact, these capacitors are provided for switching devices (gate circuits) or other components that require filtering/decoupling. These capacitors should be placed as close to these components as possible, and too far away will have no effect. Interestingly, when the power supply filter/decoupling capacitors are arranged properly, the problem of the grounding point becomes less obvious.

4. The line is exquisite, the line diameter is required, and the size of the buried hole is appropriate.

If possible, wide lines should never be thin; high-voltage and high-frequency lines should be round and slippery, without sharp chamfers, and corners should not be at right angles. The ground wire should be as wide as possible, and it is best to use a large area of copper, which can greatly improve the problem of grounding points. The size of the pad or via is too small, or the size of the pad and the hole size are not properly matched. The former is unfavorable for manual drilling, and the latter is unfavorable for CNC drilling. It is easy to drill the pad into a "c" shape, but to drill off the pad. The wire is too thin, and the large area of the unwiring area is not provided with copper, which is easy to cause uneven corrosion. That is, when the unwiring area is corroded, the thin wire is likely to be over corroded, or it may appear to be broken, or completely broken. Therefore, the role of setting copper is not only to increase the area of the ground wire and anti-interference.

5. The number of vias, solder joints, and linear density.

Although some problems occur in post-production, they are brought about by PCB design. They are: too many vias, and the slightest carelessness of the copper sinking process will bury hidden dangers. Therefore, the design should minimize the wire hole. The density of parallel lines in the same direction is too large, and it is easy to join together when welding. Therefore, the line density should be determined according to the level of the welding process. The distance of the solder joints is too small, which is not conducive to manual welding, and the welding quality can only be solved by reducing the work efficiency. Otherwise, hidden dangers will remain.