小功率開關(guān)電源外文翻譯

1、<p><b>　　外文文獻原稿和譯文</b></p><p><b>　　原 稿</b></p><p>　　Introduction</p><p>　　Switching power supply work in high frequency, high pulse state, are analog

2、circuits in a rather special kind. Cloth boards to follow the principle of high-frequency circuit wiring.</p><p><b>　　Layout</b></p><p>　　Pulse voltage connection as short as possibl

3、e, including input switch connected to the transformer, output transformer to the rectifier tube cable. Pulse current loop as small as possible such as the input filter capacitor is returned to the transformer to the swi

4、tch capacitor negative. Some out-ended output transformers are the output rectifier to the output capacitor back to transformer circuit X capacitor as close as possible to the input switching power supply, input lines sh

5、ould be avoided </p><p>　　General the output capacitor can be used the other two a close rectifier output terminal should be close to, can affect the power supply output ripple index, two small capacitor in

6、parallel results should be better than using a large capacitor. Heating devices to maintain a certain distance, and electrolytic capacitors to extend machine life, electrolytic capacitors is the switching power supply bo

7、ttleneck life, such as transformers, power control, high power resistors and electrolytic to mainta</p><p>　　Control part to pay attention to: Weak signal high impedance circuit connected to sample the feedb

8、ack loop as short as in the processing as far as possible avoid interference, the current sampling signal circuits, in particular the current control circuit, easy to deal with some unexpected bad The accident, which had

9、 some skill, now to 3843 the circuit example shown in Figure (1) Figure 1 better than Yu Figure 2, Figure 2 Zai full time by observing the current waveform oscilloscope Mingxian supe</p><p>　　Second, routing

10、</p><p>　　Alignment of current density: now the majority of electronic circuit board using insulated copper constitute tied. Common PCB copper thickness of 35μm, the alignment value can be obtained in accord

11、ance with 1A/mm experience the value of current density, the specific calculations can be found in textbooks. To ensure the alignment principles of mechanical strength should be greater than or equal to the width of 0.3m

12、m (other non-power supply circuit board may be smaller minimum line width). PCB cop</p><p>　　Add that, now Changyong circuit board design tool design software generally items such as line width, line spacing

13、, hole size and so dry plate Guo Jin Xing parameters can be set. In the design of circuit boards, design software automatically in accordance with the specifications, can save time, reduce some of the workload and reduce

14、 the error rate.</p><p>　　Generally higher on the reliability of lines or line density wiring can be used double panel. Characterized by moderate cost, high reliability, to meet most applications.</p>

15、<p>　　The ranks of some of the power module products are also used plywood, mainly to facilitate integration of power devices such as transformer inductance to optimize wiring, cooling and other power tube. Good co

16、nsistency with the craft beautiful, transformer cooling good advantage, but its disadvantage is high cost, poor flexibility, only suitable for industrial mass production.</p><p>　　Single-sided, the market ci

17、rculation of almost universal switching power supply using single-sided circuit board, which has the advantage of lower costs in the design and production technology are also taken some measures to ensure its performance

18、. Single PCB design today to talk about some experience, as a single panel with low cost, easy-to-manufacture features, the switching power supply circuit has been widely used, because of its side tied only copper, the

19、device's electrical connections, </p><p>　　To ensure good performance of the mechanical structure welding, single-sided pad should be slightly larger to ensure that the copper and substrate tied good foc

20、us, and thus will not be shocked when the copper strip, broken off. General welding ring width should be greater than 0.3mm. Pad diameter should be slightly larger than the diameter of the device pins, but not too large,

21、 to ensure pin and pad by the solder connection between the shortest distance, plate hole size should not hinder the nor</p><p>　　Electrical connection should be as wide as possible, in principle, should be

22、larger than the width of pad diameter, special circumstances should be connected in line with the need to widen the intersection pad (commonly known as Generation tears), to avoid breaking certain conditions, line and pa

23、d. Principle of minimum line width should be greater than 0.5mm.</p><p>　　Single-board components to be close to the circuit board. Need overhead cooling device to device and circuit board between the pins p

24、lus 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

25、the weight of large parts can increase the connection point, can enhance joint strength between the circuit board, such as transformers, power devi</p><p>　　Single-sided welding pins without affecting the su

26、rface 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 wel

27、ding 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 th

28、e design o</p><p>　　Two-panel 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

29、process solder solution conducive to penetrate 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 lowe

30、r part of the device may go up, have some flaws.</p><p>　　High current handling of alignment, line width in accordance with pre-quote processing, such as the width is not enough to go online in general can b

31、e used to increase the thickness of tin plating solution, the method has a good variety of </p><p>　　1. Will take the line set to pad property, so that when the circuit board manufacturing solder alignment w

32、ill 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 pla

33、ced 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 </p><p>　　Double-sided circuit bo

34、ard 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

35、 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 the non-gro

36、unded wiring layer in the same place,</p><p>　　Alignment change from a wiring layer to another wiring layer generally used hole connected, not through the pin pad device to achieve, because the plug in the d

37、evice may be damaged when the relationship between this connection, there is current in every passage of 1A, at least two through-hole, through hole diameter is greater than the principle of 0.5mm, 0.8mm generally proces

38、sed ensure reliability.</p><p>　　Cooling devices, in some small power supply, the circuit board traces can be and cooling, characterized by the alignment as generous as possible to increase the cooling area

39、is not coated solder, conditions can even be placed over holes, enhanced thermal conductivity .</p><p>　　Aluminum plate by its own structure, has the following characteristics: very good thermal conductivity

40、, single Mianfu copper, the device can only be placed in tied copper surface, can not open electrical connection hole so as not to place jumper in accordance with a single panel.</p><p>　　Aluminum plate is g

41、enerally placed patch device, switch, the output rectifier heat conduction through the substrate to go out, very low thermal resistance, high reliability can be achieved. Transformer with planar chip structure, but also

42、through substrate cooling, the temperature is lower than the conventional, the same size transformer with a large aluminum plate structure available output power. Aluminum plate jumper bridge approach can be used. Alumin

43、um plate power are generally composed by </p><p>　　As the excellent thermal conductivity of aluminum plate, in a small amount of manual welding more difficult, solder cooling too fast and prone to problems o

44、f a simple and practical way of existing, an ironing ordinary iron (preferably temperature regulation function), over and iron for the last, fixed, and temperature to 150 ℃ and above the aluminum plate on the iron, heati

45、ng time, and then affix the components according to conventional methods and welding, soldering iron temperature is appropri</p><p>　　Recent years, with the multi-layer circuit board applications in switchin

46、g power supply circuit, printed circuit transformer makes it possible, due to multilayer, smaller spacing also can take advantage of Bianya Qi window section, the main circuit board can be re- Add 1-2 formed by the multi

47、layer printed coil to use the window, the purpose of reducing circuit current density, due to adopt printed coil, reducing manual intervention, transformers consistency, surface structure, low leakage induct</p>&

48、lt;p>　　Switching power supply is divided into, two forms of isolation and non-isolated, isolated here mainly to talk about switching power supply topologies form below, non-specified, are to isolate the power. Isolate

49、d power supply in accordance with the structure of different forms, can be divided into two categories: a forward and flyback. Flyback transformer primary side means that when the Vice-edge conduction cut-off, transforme

50、r storage. Close of the primary, secondary side conduction, the energy</p><p>　　Forward and flyback circuits have their own characteristics in the process of circuit design to achieve optimal cost-effective,

51、 can be applied flexibly. Usually in the low-power flyback can be adopted. Slightly larger forward circuit can use a single tube, medium-power can use Double Forward circuit or half-bridge circuit, low-voltage push-pull

52、circuit, and the half-bridge work in the same state. High power output, generally used bridge circuit, low voltage can be applied push-pull circuit.</p><p>　　Flyback power supply because of its simple struct

53、ure, and to cut the size of a similar size and transformer inductance, the power supply in the medium has been widely applied. Presentation referred to in some flyback power supply can do dozens of watts, output power ex

54、ceeding 100 watts would be no advantage to them difficult. Under normal circumstances, I think so, but it can not be generalized, PI's TOP chips can do 300 watts, an article describes the flyback power supply can be

55、on the KW, but </p><p>　　Flyback power transformer leakage inductance is a critical parameter, because the power needs of the flyback transformer stored energy, to make full use of transformer core, the gene

56、ral must be open in the magnetic circuit air gap, the aim is to change the core hysteresis back line of the slope, so that transformers can withstand the impact of a large pulse current, which is not core into saturation

57、 non-linear state, the magnetic circuit in the high reluctance air gap in the state, generated in </p><p>　　Transformer coupling between the first pole is the key factor determining the leakage inductance, t

58、he coil to be very close as far as possible the first time, the sandwich can be used around the law, but this would increase the distributed capacitance transformer. Use core as core with a long window, can reduce the le

59、akage inductance, such as the use of EE, EF, EER, PQ-based EI type magnetic core effective than good.</p><p>　　The duty cycle of flyback power supplies, in principle, the maximum duty cycle of flyback power

60、supply should be less than 0.5, otherwise not easy loop compensation may be unstable, but there are some exceptions, such as the U.S. PI has introduced the TOP series chip can work under the conditions of duty cycle is g

61、reater than 0.5.</p><p>　　Duty cycle by the transformer turns ratio to determine former deputy side, I am an anti-shock view is, first determine the reflected voltage (output voltage reflected through the tr

62、ansformer coupling the primary voltage value), reflecting a certain voltage range of voltage increase is duty cycle increases, lower power loss. Reduce the reflected voltage duty cycle decreases, increases power loss. Of

63、 course, this is a prerequisite, when the duty cycle increases, it means that the output diode cond</p><p>　　Duty cycle increases, change the transformer turns ratio, transformer leakage inductance will incr

64、ease, its overall performance change, when the leakage inductance energy large enough, can switch to fully offset the large account space to bring low-loss, no further increase when the meaning of duty, because the leaka

65、ge inductance may even be too high against the peak voltage breakdown switch. Leakage inductance as large, may make the output ripple, and other electromagnetic indicators deteriorat</p><p>　　Some netizens s

66、aid switching power supply feedback loop parameter settings, work status analysis. Since high school mathematics is rather poor, "Automatic Control Theory," almost on the make-up, and for the door is still feel

67、ing fear, and now can not write a complete closed-loop system transfer function, zero for the system, the concept of feeling pole vague, see Bode plot is only about to see is a divergence or convergence, so the feedback

68、compensation can not nonsense, but there are a number o</p><p>　　Then today, on the duty cycle of flyback power supply (I am concerned about the reflected voltage, consistent with the duty cycle), the duty c

69、ycle 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 pr

70、essure tubes, easy to manufacture, or low-pressure pipes are more reasonable conduction losses and switching characteristics, as this line</p><p>　　Reflected voltage 600V tube proved not more than 100V, 650V

71、 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 s

72、upplies are generally used 700V or 750V or 800-900V the switch. Like this circuit, overvoltage capability against a number of switching transformer reflected voltage can be done a bit higher, the maximum reflected voltag

73、e</p><p>　　TOP PI's recommendation for the 135V chipset with transient voltage suppression diode clamp. But his evaluation board generally reflected voltage to be lower than the value at around 110V. Bot

74、h types have their advantages and disadvantages:</p><p>　　Category: shortcomings against over-voltage, low duty cycle is small, a large pulse current transformer primary. Advantages: small transformer leakag

75、e inductance, electromagnetic radiation and low ripple index higher switch loss, the conversion efficiency is not necessarily lower than the second.</p><p>　　The second category: a large number of shortcomin

76、gs of power loss, a large number of transformer leakage inductance, the ripple worse. Advantages: Some strong against over-voltage, large duty cycle, lower transformer losses and efficiency higher.</p><p>　　

77、Reflected voltage flyback power supply with a parameter related to that is the output voltage, output voltage, the lower the larger the transformer turns ratio, the greater the transformer leakage inductance, switch to w

78、ithstand higher voltage breakdown switch is possible to absorb power consumption is higher, has the potential to permanently absorb the circuit power device failure (particularly with transient voltage suppression diode

79、circuits). In the design of low-voltage low-power flyback po</p><p>　　1, using a large core of a power level lower leakage inductance, which can improve the low-voltage flyback power conversion efficiency, r

80、educe losses, reduce output ripple and improve multi-output power of the cross regulation in general is common in household appliances with a switch power, such as CD-ROM drive, DVB set-top boxes.</p><p>　　2

81、, if the conditions were not increased core, can reduce the reflected voltage, reducing the duty cycle. Reduce the reflected voltage can reduce the leakage inductance but may reduce the power conversion efficiency, which

82、 is a contradiction between the two, must have an alternative process to find a suitable point, replace the transformer during the experiment can detect the transformer original side of the anti-peak voltage, peak voltag

83、e to minimize the anti-pulse width, and magnitude of the wo</p><p>　　3, enhance the coupling, reducing losses, the introduction of new technologies, and the routing process, transformers to meet the security

84、 specifications will between the primary and secondary side to insulation measures, such as pad tape, plus side air insulation tape. These will affect the performance of transformer leakage inductance, the reality can be

85、 used in production around the primary winding secondary wrapping method. Or sub-system with a triple insulated wire wound to remove the insul</p><p>　　The article refers to low voltage output is less than o

86、r equal to 5V output, as this type of small power supply, my experience is that the power output of more than 20W output can use a forward, get the best value for money, of course, this is not the right decision , and pe

87、rsonal habits, relationship between the application environment, the next time to talk about the flyback power supply with a magnetic core, magnetic circuit air gap opening some understanding, I hope you receive adequate

88、 guid</p><p>　　Flyback power transformer core magnetization state at work in one way, it needs to open the air gap magnetic circuit, similar to the pulsating direct current sensor. Part of the magnetic coupl

89、ing through the air gap. Why I understand the principle of open air gap as follows: As the power ferrite also has a similar rectangle of the operating characteristics (hysteresis loop), operating characteristics curve in

90、 the Y-axis magnetic induction (B), now the general production process saturation point </p><p>　　Flyback Power Transformer magnetization state in one way, not only to pass through the magnetic coupling ener

91、gy, is also responsible for input and output isolation voltage transform multiple roles. Therefore, the treatment gap need to be very careful, the air gap leakage inductance can become too large, increase the hysteresis

92、loss, iron loss, copper loss increases, affecting the power of the whole performance. Air gap is too small has the potential to transformer core saturation, resulting in d</p><p>　　The so-called flyback powe

93、r supply is continuous and discontinuous mode transformer working conditions, working in full load condition in the power transformer complete transfer, or incomplete transmission mode. General design of the working envi

94、ronment, conventional flyback power supply should work in continuous mode, this switch, circuit loss are relatively small, and can reduce the stress of work input and output capacitors, but that there are some exceptions

95、.</p><p>　　Requires in particular that: As the characteristics of the flyback power supply is also more suitable for design into a high-voltage power supply, and high-voltage power transformers generally wor

96、k in discontinuous mode, I understand the need for as high voltage power supply output voltage of the rectifier diodes. Because of the manufacturing process characteristics, high-tension diode, reverse recovery time is l