【正文】 uit, according to the work of state for analysis. Will be harvested, the Forum has a message, coach feedback loop to study the design, debugging, in which CMG good answer, I think we can reference. Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty cycle with the voltage selection switch is related to some early flyback switching power supply using a low pressure tube, such as 600V or 650V AC 220V input power as a switch, perhaps when the production process, high pressure tubes, easy to manufacture, or lowpressure pipes are more reasonable conduction losses and switching characteristics, as this line reflected voltage can not be too high, otherwise the work order to switch the security context of loss of power absorbing circuit is quite impressive. Reflected voltage 600V tube proved not more than 100V, 650V tube reflected voltage not greater than 120V, the leakage inductance voltage spike when the tubes are clamped at 50V 50V working margin. Now that the MOS raise the level of manufacturing process control, flyback power supplies are generally used 700V or 750V or 800900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltage in the 150V is appropriate, to obtain better overall performance. TOP PI39。s electrical connections, mechanical fixation should rely on the copper layer, the processing must be careful. To ensure good performance of the mechanical structure welding, singlesided pad should be slightly larger to ensure that the copper and substrate tied good focus, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than . Pad diameter should be slightly larger than the diameter of the device pins, but not too large, to ensure pin and pad by the solder connection between the shortest distance, plate hole size should not hinder the normal conditions for the degree of investigation, the pad diameter is generally greater than pin diameter . Multipin device to ensure a smooth investigation documents can also be larger. Electrical connection should be as wide as possible, in principle, should be larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (monly known as Generation tears), to avoid breaking certain conditions, line and pad. Principle of minimum line width should be greater than . Singleboard ponents to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins plus casing, can play a supporting device and increase the dual role of insulation to minimize or avoid external shocks on the pad and the pin junction impact and enhance the firmness of welding. Circuit board supporting the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power device heat sink. Singlesided welding pins without affecting the surface and the shell spacing of the prior conditions, it can be to stay longer, the advantage of increased strength of welded parts, increase weld area and immediately found a Weld phenomenon. Shear pin long legs, the welding force smaller parts. In Taiwan, the Japanese often use the device pins in the welding area and the circuit board was bent 45 degrees, and then welding process, its reasoning Ibid. Double panel today to talk about the design of some of the issues, in relatively high number of requests, or take the line density of the larger application environments using doublesided PCB, its performance and various indicators of a lot better than a single panel. Twopanel pad as holes have been high intensity metal processing, welding ring smaller than a single panel, the pad hole diameter slightly larger in diameter than pins, as in the welding process solder solution conducive to perate through the top hole solder pad to increase the welding reliability. But there is a disadvantage if the hole is too large, wave soldering tin when the jet impact in the lower part of the device may go up, have some flaws. High current handling of alignment, line width in accordance with prequote processing, such as the width is not enough to go online in general can be used to increase the thickness of tin plating solution, the method has a good variety of 1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment will not be covered, the whole hot air normally be tin plated. 2. In the wiring by placing pads, the pad is set to take in line shape, pay attention to the pad holes set to zero. 3. In the solder layer placed on line, this method is the most flexible, but not all PCB manufacturers will understand your intentions, needed captions. Place the line in the solder layer of the site will not coated solder tinning line several methods as above, to note that, if the alignment of a very wide all plated with tin in solder after the solder will bond a lot and distribution is very uneven, affecting appearance. Article tin can be used generally slender width in the 1 ~ , length can be determined according to lines, tin part of the interval ~ 1mm Doublesided circuit board for the layout, the alignment provides a very selective, make wiring more reasonable. On the ground, the power ground and signal ground must be separated, the two to converge in filter capacitors, in order to avoid a large pulsed current through the signal ground connection instability caused by unexpected factors, the signal control circuit grounding point as far as possible, a skill, as far as possible the alignment of th