I. Part of the output power control loop of the power board
The key part of the output power board is the output power control circuit. In the case of layout, you should first know the characteristics of the power circuit of the part of the output power. The key parts of the output power circuit in the power supply are di/dt power circuit and dv/dt power circuit, and the routes of these two power circuits are different under the condition of reasonable layout and wiring.
Di/dt power supply circuit has a large change in current per unit time, so these power supply circuits are most important in wiring. The total loop area of all power supply circuits should be as small as possible. It’s best that the wiring of one loop overlaps on different layers, so that the total loop area of the power supply circuit is the least, and its own influence can be coupled away.
The emphasis of dv/dt power supply circuit is completely different. Because the working voltage of this kind of power supply circuit changes greatly in unit time, it is very easy to affect the outside. Therefore, the copper skin of this kind of power supply circuit should not be too wide when wiring. Considering the load-bearing current, the total width of the copper skin should be as small as possible, and the overlapping area of different layers should be as small as possible. For sensitive data signals, this kind of wiring should be avoided as far as possible.
Second, a part of the power board driver
At first, the total area of all driver control circuits should be taken into account in the line of a part of the driver, which should be as small as possible, prevent interference signals and be as close as possible to the driven part. When wiring drivers of output power components such as MOS tubes, it is necessary to pay attention to the fact that the wiring of G pole and D pole does not have to go in parallel. In most cases, the power supply circuit of D pole of MOS tubes is the power supply circuit of dv/dt, and the G pole is an optocoupler circuit. If it goes in parallel, the data signal of drivers will be easily affected, thus causing the wrong operation of MOS.
III. Sampling data signal of power board
In the output power board, the sampled data signals such as some working voltage sampling and current sampling are also particularly important. Because the data signals of the power board are accurately and immediately related to the control terminal, all the sampled data signals should bypass other data signals as much as possible. If there is a standard, the sampled data signals can be sampled by differential signals, and a detailed ground plan can be provided in the corresponding wiring area.
Fourth, the solution of power board.
Not to mention the necessity of land, no matter on which kind of board, the solution to land is crucial.
In the output power board, the ground is relatively complicated. In many cases, some of the output power goes to the ground with large current, some of the ground with small current is common, so it is very important to solve this kind of ground at the moment. In my working experience, the key to solve this kind of ground is to choose an appropriate point-and-shoot connection point. Because the design scheme of each power supply is different, the selection of this point-and-shoot node is also different. In small output photovoltaic inverters, one ground pin of BUS capacitor is generally selected. In soft starter, I usually lead a thick wiring from the ground pin of one capacitor with large current to the ground pin of which capacitor is at the input end of the power switch power supply, and then lead it from this ground pin to the ground plan of these small current behind the power switch power supply. Naturally, there are some other places, such as the ground of active crystal oscillator, sampling ground, etc. The PCB design standards of each enterprise are different.
V. Electrical safety of power panel
Electrical safety is essential in the design scheme of power products. The electrical safety policies and regulations of power boards are different in different countries and regions, and the environmental pollution level and average altitude of application scenarios are all harmful to the electrical safety. Therefore, we must make clear the above factors at the beginning of the design scheme. If there are electrical safety technical engineers, please ask them to work out the distance between creepage and clearance. In the case of PCBLayout, people should pay attention to the location of these metal components on the PCB, for example, the insurance tube, whose two sides are metal materials and the middle is nonmetal materials. If there is no base, the metal materials on both sides of the insurance tube will touch the PCB, and all the surface wiring around the insurance tube should be careful to avoid this metal material area.
Six, the power board heat pipe heat dissipation
As far as these system softwares with large output power are concerned, heat pipe heat dissipation is also particularly important. This general situation needs to be well matched with the structure. Before designing the scheme, we should master the heat pipe heat dissipation method of the overall structure, whether it is refrigeration, air-cooling or water-cooling heat dissipation, in which air-cooling is divided into air inlet and blower, all of which will do great harm to the reasonable layout.
VII. Power board EMC
As far as possible, the total width of the wiring that is mainly a part of the output power doesn’t have to change suddenly. If it is necessary to turn, the turning area should be as calm as possible, without sudden change. There are also and sometimes some of the sampled data signals with large current and small current. Although some of them share the same Internet, it is not necessary to use the same control loop in the case of self-satisfied wiring. It is better to separate them and take their own control loops.
