Wiring principles for high frequency switching power supplies
Line spacing: With the continuous improvement and enhancement of the manufacturing process of printed circuit boards, the general processing plant to produce a line spacing equal to or even less than 0.1mm has been no problem, fully able to meet the majority of applications. Considering the switching power supply components and production processes, general double-sided panel * small line spacing is set to 0.3mm, single-panel minimum line spacing is set to 0.5mm, pads and pads, pads and holes or holes and holes, the minimum spacing is set to 0.5mm, to avoid welding operations in the process of "bridging" phenomenon. This way, most of the board manufacturers can easily meet the production requirements, and can control the yield to a very high level, but also to achieve a reasonable wiring density and have a more economical cost.
Minimum line spacing is only suitable for signal control circuits and low voltage circuits below 63V, when the voltage between the lines is greater than the value of the line spacing can generally be taken in accordance with the 500V/1mm empirical value.
Given that there are some relevant standards on the line spacing has more explicit provisions, it is necessary to strictly follow the standard implementation, such as the AC inlet end to the fuse end of the line. Some power supplies have high volume requirements, such as modular power supplies. General transformer input side line spacing of 1mm has proved to be feasible. For AC input, (isolated) DC output power supply products, the more stringent regulations for the spacing to be greater than or equal to 6mm, of course, this is determined by the relevant standards and implementation methods. General spacing can be feedback optocoupler distance on both sides as a reference, the principle is greater than or equal to this distance. Can also be in the photocoupler below the printed circuit board groove, so that the creepage distance to increase to meet the insulation requirements. General switching power supply AC Input side of the line or board components from the non-insulated shell, radiator spacing should be greater than 5mm, the output side of the line or device from the shell or radiator spacing should be greater than 2mm, or in strict accordance with the specification.
Commonly used methods: the above mentioned circuit board slotting method is applicable to some of the spacing is not enough occasions, by the way, the method is also commonly used as a protective discharge gap, commonly used in television picture tube tail plate and power supply AC input. The method has been widely used in the module power supply, under the condition of potting can get good results.
Method 2: pad insulating paper, can be used green shell paper, polyester film, PTFE directional film and other insulating materials. General power supply with a green shell paper or polyester film pad in the circuit board in the metal chassis, this material has high mechanical strength, there is a certain resistance to moisture. PTFE directional film has been widely used in modular power supply due to its high temperature resistance. Between the component and the surrounding conductor can also be pad insulation film to improve the insulation resistance to electricity.
Note: some devices insulating jacket can not be used as an insulating medium and reduce the pitch, such as electrolytic capacitors, the outer skin, in high temperature conditions, the outer skin may be subject to thermal contraction. Large electrolytic explosion-proof tank front to leave space to ensure that the electrolytic capacitor in the very situation can be unimpeded pressure relief.
