Distributed noise caused by the inherent impedance of the power supply. In high-frequency circuits, power supply noise has a greater impact on high-frequency signals. Therefore, a low-noise power supply is first required. A clean ground is as important as a clean power supply; common-mode field interference. Refers to the noise between the power supply and the ground. It is the interference caused by the common mode voltage caused by the loop formed by the interfered circuit and the common reference surface of a certain power supply. Its value depends on the relative electric field and magnetic field. The strength depends on the strength.

In ከፍተኛ-ድግግሞሽ PCB, a more important type of interference is power supply noise. Through systematic analysis of the characteristics and causes of power noise on high-frequency PCB boards, combined with engineering applications, some very effective and simple solutions are proposed.

የኃይል አቅርቦት ጫጫታ ትንተና

የኃይል አቅርቦት ጫጫታ በኃይል አቅርቦቱ በራሱ የሚፈጠረውን ወይም በረብሻ ምክንያት የሚፈጠረውን ድምጽ ያመለክታል. ጣልቃ-ገብነት በሚከተሉት ገጽታዎች ይታያል.

1) Distributed noise caused by the inherent impedance of the power supply itself. In high-frequency circuits, power supply noise has a greater impact on high-frequency signals. Therefore, a low-noise power supply is first required. A clean ground is as important as a clean power source.

Ideally, the power supply has no impedance, so there is no noise. However, the actual power supply has a certain impedance, and the impedance is distributed on the entire power supply. Therefore, noise will also be superimposed on the power supply. Therefore, the impedance of the power supply should be reduced as much as possible, and it is best to have a dedicated power layer and ground layer. In high-frequency circuit design, it is generally better to design the power supply in the form of a layer than in the form of a bus, so that the loop can always follow the path with the least impedance. In addition, the power board must also provide a signal loop for all generated and received signals on the PCB, so that the signal loop can be minimized, thereby reducing noise.

2) የኤሌክትሪክ መስመር ማያያዣ. የ AC ወይም የዲሲ የኤሌክትሪክ ገመድ ኤሌክትሮማግኔቲክ ጣልቃ ገብነት ከተገጠመ በኋላ የኃይል ገመዱ ጣልቃ ገብነትን ወደ ሌሎች መሳሪያዎች የሚያስተላልፈውን ክስተት ያመለክታል. ይህ የኃይል አቅርቦት ጫጫታ ወደ ከፍተኛ ድግግሞሽ ዑደት ቀጥተኛ ያልሆነ ጣልቃገብነት ነው። የኃይል አቅርቦቱ ጩኸት በራሱ ብቻ ሳይሆን በውጫዊ ጣልቃገብነት የሚነሳው ድምጽ ሊሆን እንደሚችል ልብ ሊባል ይገባል, ከዚያም ይህን ጩኸት በራሱ (ጨረር ወይም ማስተላለፊያ) ከሌሎች ወረዳዎች ጋር ጣልቃ እንዲገባ ማድረግ. ወይም መሳሪያዎች.

3) Common mode field interference. Refers to the noise between the power supply and the ground. It is the interference caused by the common mode voltage caused by the loop formed by the interfered circuit and the common reference surface of a certain power supply. Its value depends on the relative electric field and magnetic field. The strength depends on the strength.

በዚህ ቻናል ላይ የ Ic መውደቅ በተከታታይ የወቅቱ ዑደት ውስጥ የጋራ ሞድ ቮልቴጅን ይፈጥራል፣ ይህም የመቀበያውን ክፍል ይነካል። መግነጢሳዊ መስኩ የበላይ ከሆነ በተከታታይ የምድር ዑደት ውስጥ የሚፈጠረው የጋራ ሞድ ቮልቴጅ ዋጋ፡-

Vcm = — (△B/△t) × S (1) ΔB in the formula (1) is the change in magnetic induction intensity, Wb/m2; S is the area, m2.

If it is an electromagnetic field, when its electric field value is known, its induced voltage is:

Vcm = (L×h×F×E/48) (2)

እኩልታ (2) በአጠቃላይ L=150/F ወይም ከዚያ በታች ይተገበራል፣ F በ MHz ውስጥ ያለው የኤሌክትሮማግኔቲክ ሞገድ ድግግሞሽ ነው።

If this limit is exceeded, the calculation of the maximum induced voltage can be simplified to:

Vcm = 2×h×E (3) 3) Differential mode field interference. Refers to the interference between the power supply and the input and output power lines. In the actual PCB design, the author found that its proportion in the power supply noise is very small, so it is not necessary to discuss it here.

4) የኢንተር መስመር ጣልቃገብነት. በኤሌክትሪክ መስመሮች መካከል ጣልቃ መግባትን ያመለክታል. በሁለት የተለያዩ ትይዩ ዑደቶች መካከል የጋራ አቅም ሲ እና የጋራ ኢንዳክሽን M1-2 ሲኖሩ ፣ በጣልቃ ገብነት ምንጭ ወረዳ ውስጥ የቮልቴጅ VC እና የአሁኑ IC ካሉ ፣ የተጠላለፈው ወረዳ ይታያል ።

a. The voltage coupled through the capacitive impedance is

Vcm = Rv*C1-2*△Vc/△t (4)

In formula (4), Rv is the parallel value of the near-end resistance and the far-end resistance of the interfered circuit.

b. Series resistance through inductive coupling

V = M1-2*△Ic/△t (5)

በጣልቃ ገብነት ምንጭ ውስጥ የጋራ ሁነታ ጫጫታ ካለ የመስመር-ወደ-መስመር ጣልቃገብነት በአጠቃላይ የጋራ ሞድ እና ልዩነት ሁነታን ይይዛል።

የኃይል አቅርቦትን የድምፅ ጣልቃገብነት ለማስወገድ የመከላከያ እርምጃዎች

In view of the different manifestations and causes of power supply noise interference analyzed above, the conditions under which they occur can be destroyed in a targeted manner, and the interference of power supply noise can be effectively suppressed. The solutions are:

1) Pay attention to the through holes on the board. The through hole requires an opening on the power layer to be etched to leave space for the through hole to pass through. If the opening of the power layer is too large, it will inevitably affect the signal loop, the signal will be forced to bypass, the loop area will increase, and the noise will increase. At the same time, if some signal lines are concentrated near the opening and share this loop, the common impedance will cause crosstalk.

2) የኃይል አቅርቦት ድምጽ ማጣሪያ ያስቀምጡ. በኃይል አቅርቦቱ ውስጥ ያለውን ጩኸት በተሳካ ሁኔታ ማጥፋት እና የስርዓቱን ፀረ-ጣልቃ ገብነት እና ደህንነት ማሻሻል ይችላል። እና ባለ ሁለት መንገድ የሬዲዮ ፍሪኩዌንሲ ማጣሪያ ሲሆን ከኤሌክትሪክ መስመሩ የሚመጣውን የድምፅ ጣልቃገብነት (ከሌሎች መሳሪያዎች ጣልቃገብነት ለመከላከል) ብቻ ሳይሆን በራሱ የሚፈጠረውን ድምጽ በማጣራት (በሌሎች መሳሪያዎች ላይ ጣልቃ መግባትን ለማስወገድ) ), እና በተከታታይ ሁነታ የጋራ ሁነታ ላይ ጣልቃ መግባት. ሁለቱም የማገገሚያ ውጤት አላቸው.

3) የኃይል ማግለል ትራንስፎርመር. የሲግናል ገመዱን የኃይል ምልልሱን ወይም የጋራ ሞድ የመሬት ዑደትን ይለያዩት ፣ በከፍተኛ ድግግሞሽ ውስጥ የተፈጠረውን የጋራ ሞድ loop አሁኑን በብቃት መለየት ይችላል።

4) የኃይል አቅርቦት መቆጣጠሪያ. ንጹህ የኃይል አቅርቦትን መልሶ ማግኘት የኃይል አቅርቦቱን የድምፅ መጠን በእጅጉ ይቀንሳል.

5) ሽቦ. የኃይል አቅርቦቱ የግብአት እና የውጤት መስመሮች በዲኤሌክትሪክ ቦርዱ ጠርዝ ላይ መቀመጥ የለባቸውም, አለበለዚያ ግን ጨረሮችን ለማመንጨት እና ከሌሎች ወረዳዎች ወይም መሳሪያዎች ጋር ጣልቃ መግባት ቀላል ነው.

6) Separate analog and digital power supplies. High-frequency devices are generally very sensitive to digital noise, so the two should be separated and connected together at the entrance of the power supply. If the signal needs to span both analog and digital parts, a loop can be placed at the signal span to reduce the loop area.

7) በተለያዩ የንብርብሮች መካከል የተለያየ የኃይል አቅርቦቶች መደራረብን ያስወግዱ. በተቻለ መጠን ያደናቅፏቸው, አለበለዚያ የኃይል አቅርቦቱ ጫጫታ በቀላሉ በተንሰራፋው አቅም በኩል ይጣመራል.

8) ስሜታዊ የሆኑ ክፍሎችን ለይ. እንደ ደረጃ-የተቆለፉ loops (PLL) ያሉ አንዳንድ ክፍሎች ለኃይል አቅርቦት ጫጫታ በጣም ስሜታዊ ናቸው። ከኃይል አቅርቦቱ በተቻለ መጠን ያርቁዋቸው.

9) Sufficient ground wires are required for the connecting wires. Each signal needs to have its own dedicated signal loop, and the loop area of ​​the signal and loop is as small as possible, that is to say, the signal and loop must be parallel.

10) Place the power cord. In order to reduce the signal loop, the noise can be reduced by placing the power line on the edge of the signal line.

11) የኃይል አቅርቦት ጫጫታ በወረዳ ሰሌዳው ላይ ጣልቃ እንዳይገባ እና በኃይል አቅርቦቱ ላይ በውጫዊ ጣልቃገብነት ምክንያት የሚፈጠረውን የተከማቸ ድምጽ ለመከላከል ፣ ማለፊያ capacitor በጣልቃ መንገዱ (ከጨረር በስተቀር) ከመሬት ጋር ሊገናኝ ይችላል ። በሌሎች መሳሪያዎች እና መሳሪያዎች ላይ ጣልቃ እንዳይገባ ጩኸቱ ወደ መሬት ማለፍ ይቻላል.

በማጠቃለል

የኃይል አቅርቦት ጫጫታ በቀጥታም ሆነ በተዘዋዋሪ የሚመነጨው ከኃይል አቅርቦት ሲሆን በወረዳው ውስጥ ጣልቃ ይገባል. በወረዳው ላይ ያለውን ተጽእኖ ሲገታ አጠቃላይ መርህ መከተል አለበት. በአንድ በኩል የኃይል አቅርቦቱ ድምጽ በተቻለ መጠን መከላከል አለበት. በሌላ በኩል የወረዳው ተጽእኖ የኃይል አቅርቦቱን ድምጽ እንዳያባብስ የውጪው ዓለም ወይም የወረዳው በኃይል አቅርቦት ላይ ያለውን ተጽእኖ መቀነስ አለበት።