[introduction] long-term since, transformer is the pain spot of personnel of DC/DC converter design and difficulty all the time. Because of their bulk big, price is expensive and make hard. Through reading chrestomathy piece article, you can understand planar transformer is how to raise quality to reduce converter of low power DC/DC to design cost.

What do planar transformer and annular transformer have to distinguish?

Transformer is the main core that any DC/DC converter design, it is the crucial component that decides integral function.

Traditional transformer and inductance are the component that wind a string. Major amount produces converter of low power DC/DC to use handiwork to circle the annular transformer that make; Independent to needing to amount to 6 winding and core diameter is small for the transformer that is 3 Mm to 6 Mm, aperture, it is extremely difficult to develop automatic workmanship. The miniature that the manufacturer such as RECOM developed automatic coil winding machine to make this kind is annular transformer, but this kind of solution is very difficult.

Planar magnet already existed from 80 time, but inchoate production process is very costly, because this is planar,transformer applies the market permeability besides in major finite. However the progress as production technology, the cost of planar transformer has been reduced, because this can develop new applied market.

The design of planar transformer reachs a structure

Graph 1: The ferrite magnetism core of converter of RPA100E-W series DC/DC is surrounding winding forms planar transformer

Planar transformer or inductance are used multilayer printed circuit board (the cupreous layer of PCB) forms winding; Ferrite magnetism core is surrounding winding, if pursue,1 is shown. To form wants v/LIT all over the ground number, use had concealed aperture to join PCB layer. Shunt-wound join many cross aperture to be able to bear the weight of enough electricity will make transformer of Cheng Wei power source.

Graph 2: Had concealed the 6 v/LIT all over the ground winding that aperture place forms with by two pile layer

Graph 2 showed how had concealed Kong Lai to form 6 v/LIT all over the ground winding through pile layer join. Observation is decorated this kind is how to set the two end of winding in ferrite magnetism core outside. Primary normally with sub winding crisscross is placed feel in order to reduce leakage. Printed circuit board can provide mechanical stability and consistent winding structure, suit automation production. In addition, multilayer the evolution of PCB structure makes the epoxy resin insulation between winding OK bear primary with the tall segregation voltage between sub circuit.

Planar design brought a few challenges with production group to the design really. Because be in multilayer many are being decorated to take a line on PCB have difficulty, because this plane transformer suits not to need to use the DC/DC converter of complex transformer most,develop attacks, and half bridge develop attacks is common choice.

Even if is such, number of plies still has the restriction that goes up with cost on solid Wu, because this plane magnet uses modulator of high frequency PWM and drive circuit,will reduce wants v/LIT all over the ground number and number of plies. The hasten skin effect that these taller frequency cause is the main problem that they create. As the addition of frequency, electric load flows child more and more mobile to conductor surface, reduce significant cross section and increase I2R loss. conductor design Cheng Bian makes the same score (rectangular) can prevent effect of skin of this kind of hasten.

Multilayer the structure has tall coupling electric capacity and to high frequency PWM control causes an effect. Must manage the coupling between planar transformer and traditional circuit carefully in order to avoid termination loss. Magnetism core air gap and statified winding is stood by can cause remarkable eddy current loss, and because circle number comparing differs, because this must be every input / the PCB with output combination design and separate test.

Once these problems get settlement, planar technology is OK compose builds extremely compressed transformer in order to transmit high-power, let DC/DC converter become thinner then: Graph of the 15W converter of 1 enclose height only 9.9 Mm (0.4 inches) !

The other good point of planar design is better winding medicinal powder feeling of design of hot, high density, low leakage and high power density.

Planar transformer faces towards lower power strides

The benefit that describes in front makes planar transformer makes the indispensable one part in technology of high-power DC/DC converter, and RECOM is in now conformity of will planar technology arrives power in the converter with lower, smaller size.

Graph 3: The converter of RS12-Z 12W DC/DC of RECOM uses planar transformer

Graph 3 those who showed set of DC/DC of RS12-Z stabilized voltage is exterior with internal composition. This product is used contain those who bury aperture and blind aperture is via, multilayer PCB, in very compact SIP the 12W part that an industry makes precede in enclosing, rose than power density with photograph of SIP8 competition product 150% .

Design of this stabilized voltage is mixed in the primary side of transformer sub side is compositive integrated circuit. Primary side IC is driver of transformer of type of a wide input, push-pull. Output (sub side) step-down class uses synchronism to adjust accurately laden.

Even the DC/DC converter of 1W and 2W also is planning in, begin from two range of products. Converter of RKK series DC/DC has the extremely tall segregation of 4kVDC/1s to apply to industrial market. Mark deserves to include range of wide job temperature – 40 ° C comes + 105 ° C, need not fall the forehead. Converter passed IEC/EN/UL62368-1 attestation, apply to IGBT driver application.

Converter of RYK series DC/DC is a low cost, general segregation type converter, inside buy linear manostat, can offer the stable output that does not suffer laden effect.

Convert planar transformer can come true more the production process of automation decreases to assemble working procedure artificially, promote a design quality thereby. Need not change the voltage that transformer winding differs with suiting, because this develops custom-built design,also become easier. The turnaround time that is custom-built design as a result is shorter, because the test of need is fewer.

The times of planar transformer already came, will planar transformer applies RECOM to be done in DC/DC converter product line the most effective use.

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