PCB LED switching power supply design 3
The design of the ground should note the following:
1. The right choice is usually a single point grounding, filter capacitor common ground point should be the other high-current AC coupled to the only connection point to the same level, the circuit ground point should be as close as possible, and the power circuit of the filter capacitor should then take place on the stage, mainly on account of the various parts of the circuit back to the way the current is changing, because the actual flow through the impedance of the line parts of the circuit will lead to changes in ground potential to introduce interference. In the switching power supply, its inductance between the wiring and devices less affected, while the grounding circuit loop formed by a greater impact on the interference, and thus using point grounding, about the power switch current loop (in the ground a few devices are connected to the ground pin, the output rectifier current loop of several components of the ground also received a corresponding ground pin filter capacitor, so that power supply more stable and less self-excited. can not do a single point, the common ground Department received two diode or a small resistance, in fact, connected to a piece of copper more concentrated at the can.Pcb assembly china.
2. As if the ground wire bold ground very fine, ground potential is with the current changes, resulting in electronic equipment, the timing signal level
instability, deterioration of noise performance, so make sure every high current ground as short and wide use of printed lines, try widening power supply, ground width, it is better than the power ground line width, and their relationship is: Ground> Power Line> signal line, if possible, ground wire width should be greater than 3mm, a large area of ??copper layer can also be used as a ground in the PCB to spend on the places that are not being connected with the land use as a ground. When the global routing, must follow the following principles:
(1). Wiring direction: from the welding side of view, the arrangement of components to maintain position as far as possible consistent with the schematic diagram, wiring schematic alignment with the direction of the direction of the best line, because the production process often requires a variety of parameters in the welded surface testing, so do check the easy production, commissioning and maintenance (Note: refers to the circuit performance and to meet with the panel layout of the whole installation requirements of the premise.)
(2). Design layout diagram to minimize the bend alignment, print the line width of the arc do not mutation, wire corner should be ≥ 90 degrees, and strive to simple lines.
(3). Not allowed in the printed circuit crossover circuit that might cross the line, you can use the "drill", "around" two kinds of solution. Which leads to a from the other resistors, capacitors, transistors, the gap at the foot of "drill" In the past, or may cross from one end of a lead article, "around" the past, in exceptional cases to the circuit is very complicated, to simplify the design also allows with a wire jumper to address the cross-circuit problem. Due to a single panel, line elements in the top surface, surface-mount devices in the bottom surface, so the layout of the device when the line overlap with surface-mount devices, but the pad to avoid overlap.
3. Input to and output to the switching power supply for low voltage DC-DC, wishing to return to the output transformer primary voltage feedback, both sides of the circuit should have a common reference, and thus were in the shop on both sides of the earth, after copper, but also connected together to form a common ground.
V. Check
Layout design is completed, the need to carefully check the wiring design meets the rules set by the designer, but also the rules need to confirm whether the demand forPCB production process, the general inspection line and line, line and component pad, line and through holes, component pads and the through hole, through hole and the distance between the through hole is reasonable, whether to meet production requirements. The width of the power line and ground is appropriate, whether in the PCB ground also allows widening of the place. Note: Some errors can be ignored, for example, some connectors on the part of the Outline frame, the inspection interval will be wrong; modified trace each other and vias, the copper must re-one.
Sixth, review under the "PCB Checklist", including design rules, layer definitions, line width, spacing, pad, via set, but also focus on reviewing the reasonableness of the device layout, power supply, ground network alignment, high-speed clock network of lines and shielding, decoupling capacitors are placed and the connections.
Seven design Gerber file output output Note:
a. need to output layer wiring layer (bottom), silk screen layer (including the top screen and bottom screen), solder mask layer (bottom solder mask), drilling layer (bottom), while also generating drill files (NC Drill)
b. set the screen layer Layer, do not choose Part Type, select the top (bottom) and the silk screen layer Outline, Text, Linec. in each of the Layer set, it will be Board Outline election, set screen layer Layer, do not choose Part Type, select the top (bottom) and the silk screen layer Outline, Text, Line. d. generating drill files, use the default settings Power LED PCB Do not make any change.