[introduction]In the article, magnetism core chooses the standard ferrite that my general introduces DC-DC converter to you or uses in the application such as inductor of wave of power source filter guideline and design process. This flow involves a series of step, need uses list of much share data, and if inductor of ferrite magnetism core is designed,need clearance, need to carry out the iteration of certain level.

In the article, magnetism core chooses the standard ferrite that my general introduces DC-DC converter to you or uses in the application such as inductor of wave of power source filter guideline and design process. This flow involves a series of step, need uses list of much share data, and if inductor of ferrite magnetism core is designed,need clearance, need to carry out the iteration of certain level. Each phase is as follows:

Before continue, the decision uses ferrite magnetism core and we need a consideration is not the effect that any other data place cause. Ensure this is the stuff that fits you to use requirement most please.

Size of affirmatory magnetism core (the 1st phase)

The design that article place uses aims to be the circumstance of 1mH about in the light of inductance, the ferrite data that considers is the plane that Ferroxcube makes ferrite. Number of its spare parts is E38/8/25, need forms a whole magnetism core group twice partly partly:

The effective length that those who show is magnetism core is highlighted in red circle; This is the fundamental value of density of magnetic flux of computational peak value. Transmit a distance on average it is the flux when constituting core of two valve magnetism. The blue line place in pursueing as follows shows:

The compose that what right reveals is magnetism core group and PCB proposes way; PCB copper course will form coil link, we may need pile to count a small-sized PCB ability to get true v/LIT all over the ground number. Another purpose of this kind of design is to may reduce integral appearance height. Accordingly, we selected group of planar magnetism core.

Consider and choose ferrite material (the 2nd phase and the 3rd phase)

E38/8/25 magnetism core has a variety of different ferrite material to be able to offer an alternative. Common material type is 3C90 and 3F3. It is to study kind of these two kinds of stuff next, in order to determine which kind of likelihoods more accept favour. The first is compared it is frequency is answered, namely the frequency that ferrite material suits has many tall:

The magnetism conductance that solid line represents material (ferrite ” high grade ” coefficient) . Below 100kHz, their value is in 2000 the left and right sides. This tells us, compare with air look, they are in (A) concentration flux and (B) it is good that tie flux respect has many. Both is 2000 times better than air, this are very important. But both too big distinction is done not have below 100kHz, and they have reasonable property below the frequency that is as high as 1MHz.

Dotted line shows loss of magnetism core material, below 1MHz, 3F3 material summary excel 3C90.

Below one shows magnetism conductance follows the metabolic rate of magnetism core temperature quite:

Work to the model of 100 ° C in 0 ° C inside limits, 3F3 material will be first selection. Another when did not show is level of magnetism core saturation quite. Nevertheless, I did not include my, because the saturated level of two kinds of material is very adjacent, and won’t affect the decision of choice 3F3 material.

Overview

We chose a name to be E38/8/25 (Ferroxcube is made) magnetism core type, investigate its to make material. Material 3C90 and 3F3 are very common, when studying its material norms, we decide to use 3F3, because its performance is better.

To get these verdict, we need to study the data with different triplet is expressed; The data table of E38/8/25 shows magnetism core group its make material, still told us a crucial parameter, namely effective length. Next, we studied the data of these two kinds of material is expressed, undertook side by side the technology is compared.

Computational v/LIT all over the ground number (the 4th phase)

We return table of data of E38/8/25 magnetism core, search the name is AL (inductance coefficient) number:

Relevant numerical value is left 7250 of next horn. The meaning of this number is, the inductance of winding of one v/LIT all over the ground copper will be 7250nH (7.25) . This is the value when using two identical planar magnetism core to be combined together. You still should notice conductance of magnetism core magnetism () associated value is 1570. It is at first in material norms, this value is 2000; Nevertheless, after moulding becomes magnetism core, this value can decrease a little. Medium ” E ” represent ” effective ” , namelyBe called effective magnetism conductance.

Center flux as a result of ferrite material and (haply) ensure all winding circle a mutual coupling, because this circles the relation between number and inductance is:

What computation needs electricity (the 5th phase)

We have group of core of a magnetism (and magnetism core material) , already calculated now a wants v/LIT all over the ground number, but is need connected on what electric current? Can you pose a problem? Electric current too congress brings about magnetism core saturation, because this should prevent this kind of situation, but we need thorough knowledge to use ability computation electricity. In this give typical examples, we assume application is an use ferrite guideline of magnetism core choice and winding stimulate type transformer ferrite instead as DCM the DC-DC converter of magnetism core.

Because it is to stimulate type circuit instead, so we need not analyse any sub circuit respects in order to calculate primary electric current; We need to know to offer load only most high-power and working frequency. Accordingly, assume working frequency is 100 kilohertz, the power that laden place needs is 40 tile.

Will laden power is divided with frequency, the energy that can get primary circuit must store and transmit sub circuit in every switch cycle (the unit is joule) . Must meet suppose have a few losses, accordingly we can raise energy 10% , in order to settle these losses. If we are used ” well-known ” inductor energy is formulary, the peak value electricity that can use computation of the following equation to give circuit place to need:

Of course, if you want to use different applied circuit for winding component, so what voltaic computation shows above likelihood comparing is simpler. No matter which are planted circumstance, you still need electric current of computational peak value to whether be put in order to examine in problem of potential magnetism core saturation.

Computation gives the electric current of target application to be 0.918, magnetism core magnetizes the transformer ferrite that we know to this electric current is to stimulate type converter instead electric current. Accordingly, it makes very easily magnetism core supersaturation.

Density of computational magnetic flux (the 6th phase)

For density of computational magnetic flux, electric current of our need use peak value, v/LIT all over the ground number and the effective length of the 1st phase are worth () (valve of core of two E38/8/25 magnetism is 52.4 millimeter) . Do you still retain this numerical value?

Peak value electric current, v/LIT all over the ground number andMetropolis influence calls magnetic field strength (H) value:

Accordingly, multiply H with magnetism conductance, can get B of magnetic flux density. Foregone, compare with air look, magnetism conductance () for 1570; We still know (from all sorts of origin) , absolutely magnetism conductance is airy every meters 1.257. Accordingly, we can calculate as follows B:

Tesla of × 10-6 = 0.4148 of 1.257 of × of 1570 of × of B = 210.2

This is the density of peak value magnetic flux that forecast, be informed from inside document, to ferrite magnetism core, this cost is too high. Ferrite controls can serious saturation in 0.4 tesla, accordingly we must reconsider plan a little.

Whether to need clearance certainly (the 7th phase)

The answer is very simple: Yes, we need to reduce the density of peak value magnetic flux that forecast. Good news is, we can buy the group of E38/8/25 magnetism core that already implemented clearance beforehand. Does the data that still retains the 4th phase express cento?

We can choose the magnetism core with a magnetism core that has space and an unoccupied place very close to each other, is not the magnetism core that the choice does not have clearance twice. This will produce construction of core of the following magnetism:

If we choose a clearance to be 0.25mm (250) magnetism core, criterion AL value can be reduced 1000, this means us to need more to circle several ability produce 1mH inductance.

• Begin from the 4th phase, we should be used now 32 v/LIT all over the ground in order to get 1.024mH.
• Begin from the 5th phase, peak value electric current should be 0.927 (before it is 0.918) .
• Begin from the 6th phase, h is every meters of 566.1 ampere turns now (before for 210.2At/m)

Tesla of × 10-6 = 0.153 of 1.257 of × of 216 of × of B = 566.1

Next, we can use the magnetism conductance that takes spaceValue 216, density of magnetic flux of recount peak value.

This showed the effect that adds a space only. Our apt stimulates type converter set to turn over a value under 0.2 tesla, this value is accordingly more appropriate. It is to emulate offerred conclusion below (check as a kind of integrality) :

These numbers consider be identical. Group of clearance magnetism core (H field is 566.1) density of emulation magnetic flux is 129mT, and the value that the hand changes computation to reach is 153mT. In the light of very close to each other unoccupied place group of core of 12 v/LIT all over the ground magnetism (H field is 210.2) , the density of emulation magnetic flux that we get is 413mT (be close to a hand to move calculative 414.8mT very much) .

Wraparound

Above all, designing transformer ferrite magnetism core or use ferrite when magnetism core inductor, use proper design the process is crucial. Next, the ultimate test of real world cannot be replaced. Any handiwork are made (or self-restrained) winding component needs this course. Nevertheless, the article can bona fide reveals a process, hope you can narrate executive operation according to article place in order to get outstanding result. If you are OK,know design of inductor of ferrite magnetism core and clearance design deep more in this process, that will be an additional results.

(article origin: Altium, Rich traveler writer: Mark Harris)

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