LED driver power supply PCB design skills and specifications
In any power supply design, the physical design of the PCB board is the last link. Its design method determines the electromagnetic interference and power supply stability. Let’s analyze these links in detail:
1.Design process from schematic to PCB Establish component parameters-》Enter principle netlist-》Design parameter setting-》Manual layout-》Manual wiring-》Verify design-》Review-》CAM output.
2.Parameter setting The spacing between adjacent wires must meet the electrical safety requirements,
and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing must at least be suitable for the voltage to be tolerated. When the wiring density is low, the spacing between signal lines can be appropriately increased. The signal lines with high and low levels should be as short as possible and the spacing should be increased. In general, the routing spacing is set to 8mil.
The distance from the edge of the inner hole of the pad to the edge of the printed board should be greater than 1mm, so as to avoid pad defects during processing. When the trace connected to the pad is thin, the connection between the pad and the trace should be designed into a water drop shape. The advantage of this is that the pad is not easy to peel, but the trace is not easy to disconnect from the pad.
3.Component layout Practice has proved that even if the circuit schematic is designed correctly
improper printed circuit board design will have an adverse effect on the reliability of electronic equipment. For example, if two thin parallel lines on the printed board are close to each other, the signal waveform will be delayed and reflected noise will be formed at the terminal of the transmission line; interference caused by inconsiderate consideration of the power supply and ground line will reduce the performance of the product. Therefore, when designing the printed circuit board, you should pay attention to using the correct method.
4.Wiring The switching power supply contains high-frequency signals. Any printed line on the PCB can act as an antenna.
The length and width of the printed line will affect its impedance and inductance, thereby affecting the frequency response. Even the printed line passing the DC signal will couple to the RF signal from the adjacent printed line and cause circuit problems (even radiate interference signals again).
5.After the wiring design is completed, it is necessary to carefully check whether the wiring design conforms to the rules set by the designer.
At the same time, it is also necessary to confirm whether the rules set meet the requirements of the printed circuit board production process. Generally, check whether the distance between lines, lines and component pads, lines and through holes, component pads and through holes, and through holes are reasonable and meet production requirements. Whether the width of the power line and the ground line is appropriate, and whether there is still a place in the PCB that can widen the ground line. Note: Some errors can be ignored. For example, part of the Outline of some connectors is placed outside the board frame, which will cause errors when checking the spacing; in addition, each time the routing and vias are modified, the copper must be re-coated.
6.Review According to the “PCB Checklist”, the content includes design rules, layer definition, line width, spacing, pads, and via settings. It is also necessary to focus on reviewing the rationality of the device layout, the routing of the power and ground network, the routing and shielding of the high-speed clock network, and the placement and connection of the decoupling capacitors.
