PCB layout design principle of non-isolated switching power supply

Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

Overview:
A good layout design optimizes efficiency, slows thermal stress, and minimizes noise and effects between traces and components. It all comes from the designer's understanding of the current conduction path and signal flow in the power supply.
When a prototype power board is powered up for the first time, the best thing is that it not only works, but also quiet and low heat. However, this situation is rare.
A common problem with switching power supplies is the "unstable" switching waveform. In some cases, the waveform jitter is in the sound band and the magnetic components produce audible noise. If the problem lies in the layout of the printed circuit board, it may be difficult to find the cause. Therefore, the correct PCB layout at the beginning of the switching power supply design is critical.
Power supply designers need to have a good understanding of the technical details and the functional requirements of the final product. Therefore, from the beginning of the board design project, the power supply designer should work closely with the PCB layout designer on the critical power layout.
A good layout design optimizes power efficiency, slows thermal stress, and more importantly, it minimizes noise and the interaction between traces and components. To achieve these goals, designers must understand the current conduction path and signal flow inside the switching power supply. To achieve the correct layout of the non-isolated switching power supply, it is important to keep these design elements in mind.

Layout Planning For embedded dc/dc power supplies on a large board, for optimal voltage regulation, load transient response, and system efficiency, the power supply output should be placed close to the load device to minimize interconnect impedance on the PCB traces. And conduction pressure drop. Ensure that there is good air flow and limit thermal stress; if forced air cooling is used, place the power supply close to the fan position.
In addition, large passive components (such as inductors and electrolytic capacitors) must not block airflow through low surface packaged semiconductor components such as power MOSFETs or PWM controllers. In order to prevent switching noise from interfering with the analog signal in the system, it should be avoided to place sensitive signal lines under the power supply as much as possible; otherwise, an internal ground plane should be placed between the power supply layer and the small signal layer for shielding.
The key is to plan the location of the power supply and the need for board space during the early design and planning phases of the system. Sometimes designers ignore this advice and focus on the more "important" or "exciting" circuits on large system boards. Power management is seen as an afterthought, and the power is placed on the extra space on the board. This is a disadvantage for efficient and reliable power supply design.
For multilayer boards, a good method is to place a DC or DC input/output voltage layer between the high current power component layer and the sensitive small signal trace layer. The formation or DC voltage layer provides an AC ground for shielding small signal traces from high noise power traces and power components.
As a general rule, the ground plane or DC voltage layer of a multilayer PCB should not be separated. If this separation is unavoidable, the number and length of traces on these layers should be minimized, and the routing should be kept in the same direction as the large current to minimize the effects.
Figures 1a and 1c show the poor layer structure of a six-layer and four-layer switching power supply PCB, respectively. These structures sandwich the small signal layer between the high current power layer and the ground plane, thus increasing the capacitive noise coupled between the large current/voltage power layer and the analog small signal layer.

1b and 1d in the figure are good structures for the six-layer and four-layer PCB designs, respectively, to help minimize interlayer coupling noise, and the formation is used to shield small signal layers. The main point is: Be sure to place a ground plane next to the outer power level layer. Use a thick copper foil for the external high-current power layer to minimize PCB conduction loss and thermal resistance.
(Please read the PDF for details)