Adjust the method of damp of filter wave system

 

This section introduction adjusts a few kinds the method of damp, can use at reducing syntonic aiguille n. JeffersonEco offerred 3 kinds of meanses in its article:

 

Graph the frequency of method of 22 different damp is answered

 

Methodological A is to adding resistance of a series connection, but suppression system is syntonic, but can reduce effectiveness of high frequency bypass. Methodological B is in ferrite two end add magnetism bead a fraction is worth shunt resistance, also meet so suppression system is syntonic. But, in high frequency when the attenuation character of filter can drop. Next graphs showed MPZ1608S101A is used and do not use 10ΩThe circumstance of shunt resistance leaves the relation curve of impedance and frequency. Reseda dotted line states magnetism bead is used 10ΩThe total impedance of shunt resistance. Magnetism bead impedance and resistor combination drop considerably, main by 10ΩResistor decision. But, use 10ΩThe 3.8 MHz when shunt resistance is handed in more frequency is far under magnetism bead oneself when 40.3 MHz hand in jump over frequency. In low the magnetism inside much frequency scope bead show block sex, can reduce Q cost, improve damp performance.

 

Curve of graph 23 (a) MPZ1608S101A ZRX (curve of B) MPZ1608S101A ZRX

 

In the switch power source that uses the method of the description in document in 3.2 when the author, before discovery two kinds of methods can not reduce the noise amplitude of 0.6MHz, the 3rd kind of method can reduce noise of all and high frequency harmonic effectively.

 

 

Graph the result that 3 kinds of 24 means apply in 3.2 switch power source

 

relatively at Jefferson Eco, if where manage owes damp,Ken Kundert introduced in detail not only in its article, and gave out the computational means of every kinds of circumstance.

 

Graph a few kinds of methods of network of Ou of 25 damp solution and the cost that critical damp requires resistor

 

From go up in 4 kinds of methods that the author in the graph gives out, see the drawback with all exist certain not hard, filter wave sacrificed to insert caustic on certain level or energy of signal power source. For this, the author complemented one kind satisfies RCL paralell connection namely, the damp of contented also series connection adjusts method. Following plan institute are shown, the method that can see this method and Jefferson Eco are described exactly like, different is Ken Kundert gave out further Rdamp, cdamp, cbyp3 person the relation between, namely

 

 

Graph the first selection means that network of the 26 Ou that it is solution provides damp

 

Because existing in actual circuit a lot of the distributinging parameter that we can not measure accurately, so the method above always is not effective, will tell to most engineer, do not be willing to try too. Here author offers a simple and crude means, the similar problem that encounters to respect of frequency of low frequency switch namely, can divide through increasing the means filter of inductance. Feeling value should not be less than 50uH, of course the setting of this target parameter is not invariable. Next graphs increase an inductance to be on magnetism bead foundation, inductance feeling is worth the result that increases 50uH from 10uH, can see, after should increasing 50uH, the noise amplitude of all harmonic heft all is compared initiative want when circuit of the wave that do not have filter low.

 

 

Graph 27 inductance increases to adjust on circuit damp

 

Because occupy sky comparing 50% for a special situation, when load by 10 initiativeΩReduce 2ΩWhen (imitate circuit is fully loaded with a circumstance) , occupy sky comparing to be about right now 64% . Right now occasionally second harmonic fills fission to come out now, increase inductance to be in be fully loaded with a circumstance to fall as before applicable. And above the situation that the method that alludes in document can encounter low frequency to exceed initiative value as before.

 

After load of 28 power source increases, the graph adjusts the effect of feeling value as before

 

Graph 3 kinds of 29 methods that use document to allude conduct noise in what measure below burden circumstance

 

Magnetism bead slants in dc the influence below buy

 

For the ferrite with right choice of power source application magnetism bead needs to consider filter bandwidth not only, still need to consider magnetism bead photograph to slant to dc the impedance of buy electric current is characteristic. Below major case, manufacturer appoints magnetism bead to announce 0 dc to slant in the impedance of 100 MHz only the frequency when buy electric current answers curvilinear data manual. However, ferrite magnetism bead uses as when wave of power source filter, the load current that carries magnetism bead is from beginning to end 0, and slant as dc buy electric current from 0 begin to grow, these parameter also can be changed quickly subsequently. Slant as dc of buy electric current increase, magnetism core material begins saturation, bring about ferrite magnetism bead inductance drops considerably. The data that inductance degree of saturation uses according to place of package magnetism core and differ somewhat. Next graphs showed two ferrite the typical dc of magnetism bead slants buy depends on a circumstance. Rated electric current is 50% when, inductance drops at most 90% .

 

Graph 30 (A) dc slants place is right the influence of magnetism bead inductance and slant at dc relatively the curve of buy electric current (B) use TDKMPZ1608S101A magnetism bead (C) use magnetism of Wurth Elektronik742 792 510 bead

 

If need efficient filter power source noise, design a principle for, 20% place should be made an appointment with to use ferrite magnetism in rated dc electric current bead. If place of these two give typical examples is shown, in rated electric current 20% place, inductance drops to about 30% (6 A magnetism bead) and about 15% (3 A magnetism bead) . Ferrite magnetism bead voltaic rating is parts of an apparatus in appoint litre of lukewarm circumstance to fall but the biggest electric current is worth susceptive, be not the real work place that uses for filter wave.

 

In addition, dc slants the effect of buy electric current can be worth through the impedance inside frequency limits decrease and observe, reduce ferrite then the effectiveness of magnetism bead and the ability that eliminate EMI. Graph 30b and graph 30c showed ferrite how does magnetism bead impedance slant along with dc of buy electric current change and change. Need to bring to bear on only 50% of rated electric current, the effective impedance when 100 MHz can drop considerably from 100Ω to 10Ω (TDKMPZ1608S101A, 100Ω , a, 0603) , and drop from 70Ω to 15Ω (WürthElektronik742 792 510, 70 Ω , 6 A, 1812) .

 

Bibliographical reference

 

[1] Jefferson Eco&Magnetism bead uncovers Aldrick Limjoco- ferrite secret.

 

[2] Arthur B. Williams- imitate filter and circuit design manual.

 

[3] Ken Kundert-Power Supply Noise Reduction.

 

[4] Murata-Application Manual For Power Supply Noise Suppression And Decoupling For Digital Ics.