An integrated-type transformer according to an embodiment includes a linear-type magnetic member; a power factor correction circuit disposed to a left of the linear-type magnetic member and including an inductor; and a transformer disposed to a right of the linear-type magnetic member and including a primary coil and a secondary coil.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2013/010362, filed Nov. 14, 2013, which claims priority to Korean Patent Application Nos. 10-2012-0131885, filed Nov. 20, 2012 and 10-2012-0133872, filed Nov. 23, 2012, whose entire disclosures are hereby incorporated by reference.

TECHNICAL FIELD

The embodiment relates to an integrated-type transformer.

BACKGROUND ART

In recent years, a power supply device employing a switching mode power supply (SMPS) has attracted attention. The SMPS provides stable power by using a switching device, such as a metal oxide semiconductor field effect transistor (MOS FET) or a bipolar junction transistor (BJT), and a transformer.

The SMPS includes a power factor correction (PFC) circuit for satisfying the harmonic regulation of commercial AC power and a transformer for satisfying safety standard.

In this case, the PFC circuit and the transformer include coils.

That is, the PFC circuit includes an inductor for improving a power factor and the transformer includes a primary coil and a secondary coil for voltage transformation.

In the related art, the PFC circuit is implemented by forming the inductor in one structure, and the transformer is implemented by forming a primary coil and a secondary coil in another structure, respectively.

In other words, the inductor constituting the PFC circuit and the primary and secondary coils constituting the transformer are formed in mutually different structures, such that the PFC circuit and the transformer are manufactured. Thus, according to the related art, an interaction between the PFC circuit and the transformer may be effectively reduced.

Meanwhile, as household appliances have tended to be developed in a light and slim structure with a small size, the SMPS has been requested to be implemented in a slim structure.

However, as described above, since the PFC circuit and the transformer are configured in mutually different structures, the PFC circuit and the transformer have greater volumes than other components constituting the SMPS.

DISCLOSURE

Technical Problem

The embodiment provides an integrated-type transformer including a PFC circuit and a transformer configured with one component.

In addition, the embodiment provides an integrated-type transformer which is capable of minimizing volumes filled with a PFC circuit and a transformer.

Technical Solution

According to one embodiment, there is provided an integrated-type transformer which includes: a linear-type magnetic member; a power factor correction circuit disposed to a left of the linear-type magnetic member and including an inductor; and a transformer disposed to a right of the linear-type magnetic member and including a primary coil and a secondary coil.

In addition, according to another embodiment, there is provided an integrated-type transformer which includes: a bobbin including a first winding part formed at a first side with respect to a center and a second winding part formed at a second side with respect to the center; a linear-type magnetic member received in a central region of the bobbin; a first bending-type magnetic member received at the first side of the bobbin; a second bending-type magnetic member received at the second side of the bobbin; an inductor wound around the first winding part of the bobbin and constituting a power factor correction circuit; and primary and secondary coils wound around the second winding part of the bobbin and constituting a transformer.

Advantageous Effects

According to the integrated-type transformer of the embodiment, the PFC circuit and the transformer are configured with one component, so that the volume of the power supply device including the PFC circuit and the transformer may be minimized.

In addition, according to the integrated-type transformer of the embodiment, the PFC circuit and the transformer are configured with one component, so that the productivity of the power supply device may be improved.

In addition, according to the integrated-type transformer of the embodiment, an oscillating phenomenon, which is generated at a time point when the operating frequency of the PFC circuit is approximate to that of the transformer, may be removed by determining the operating frequency of the transformer according to the operating frequency of the PFC circuit, so that the circuit reliability may be secured.

BEST MODE

Hereinafter, embodiments will be described in detail with reference to accompanying drawings so that those skilled in the art can easily work with the embodiments. However, the embodiments are not limited thereto and may be variously modified.

In the following description, when a predetermined part is referred as to “include” a predetermined component, the predetermined part does not exclude other components, but may further include other components unless indicated otherwise.

Hereinafter, an integrated-type transformer for a power supply device including a power factor correction (PFC) circuit, in which an inductor constituting the PFC circuit and primary and secondary coils constituting a transformer are integrally formed as a single component, will be described in detail.

FIG. 1is a block diagram showing a power supply device according to an embodiment.FIG. 2is a circuit diagram showing the power supply device ofFIG. 1.

Referring toFIG. 1, a power supply device for supplying power to an LED40includes an input power source, an input unit110, a rectifying unit120, a PFC voltage converting unit150and an output unit160.

In this case, the PFC voltage converting unit150includes a PFC circuit130and a voltage converting unit140, each of which includes at least one device constituting it.

That is, the PFC voltage converting unit150includes an inductor constituting the PFC circuit130and the voltage converting unit140includes primary and secondary coils.

The LED40may be a light emitting device. Preferably, the LED40may be a plurality of light emitting diodes. The power supply device converts AC power input from an outside into a DC voltage having a predetermined level and outputs the DC voltage to the LED40.

The input unit110includes an input filter for blocking an overcurrent of an AC voltage input from an outside.

The input filter may include at least one inductor.

The rectifying unit120rectifies an AC voltage applied from the input unit110. The rectifying unit120may include a bridge rectifier.

The PFC circuit130compensates the power factor of the voltage rectified by the rectifier and outputs the voltage having the compensated power factor to the voltage converting unit140.

That is, a plurality of diodes of a bridge rectifier constituting the rectifying unit120are tuned on only at a predetermined operating voltage or more to output the input voltage. Thus, the output voltage of the rectifying unit120is not a square wave. Therefore, a power non-input section in which power is not input to the voltage converting unit140may exist, so that the power factor may be lowered.

The PFC circuit130includes a first inductor L1for compensating the power factor. The PFC circuit130stores energy in the first inductor L1, so that the power stored in the first inductor L1is output to the voltage converting unit140during the power non-input section, thereby compensating the power factor.

To this end, the PFC circuit130includes a first inductor L1connected between first and second nodes n1and n2corresponding to an output line of the rectifying unit120, a first transistor Q1connected between the second node n2and the ground to be turned on or off according to a control signal, the first transistor Q1to allow energy to be stored in the first inductor L1and be output the stored energy, and a first diode D1provided between the second node n2and the voltage converting unit140.

The first diode D1prevents current from flowing in a reverse direction.

Meanwhile, the voltage converting unit140includes a transformer which receives power from the PFC circuit130, converts the input voltage into a voltage according to a switch operation and outputs the converted voltage.

The voltage converting unit140may include second and third transistors Q2and Q3connected in series to the input end, and a transformer L2and L3connected between the second and third transistors Q2and Q3as shown inFIG. 2. That is, the transformer includes first and second coils L2and L3.

The voltage converting unit140may include a capacitor C2provided between a node between the second and third transistors Q2and Q3and the transformer L2and L3to configure an LLC transformer, and a capacitor C1provided to an input end of the voltage converting unit140.

The second and third transistors Q2and Q3of the voltage converting unit140are alternately turned on or off to charge the capacitor C2and convert the charged voltage into an input voltage, so that the input voltage may be stably output.

The transformer L2and L3includes two inductors (primary coil and secondary coil) adjacent to each other. In detail, the transformer L2and L3includes a second inductor L2formed between a third node n3connecting with a capacitor C2, and a fourth node n4constituting the ground, and a third inductor L3induced by the second inductor L2.

Both terminals of the third inductor L3constitute fifth and sixth nodes n5and n6.

The output unit160is connected to the fifth and sixth nodes n5and n6.

The output unit160may include a plurality of output parts for receiving mutually different voltages according to connected points after being connected to a part of the coil constituting the third inductor L3when the output unit160provides mutually different voltages to plural loads.

That is, although the fifth node n5of the third inductor L3is depicted as a single node inFIG. 2, the fifth node n5may include mutually different nodes for the purpose of target voltages of the output end.

In this case, when two output ends exist, each output end includes second and third diodes D2and D3connected to the fifth node n5and output capacitors C3and C4connected between each of the diodes D2and D3and the sixth node n6.

The power supply device according to an embodiment provides an integrated-type transformer in which the first to third inductors L1to L3are configured as a single product.

Hereinafter, an integrated-type transformer according to an embodiment will be described with reference toFIGS. 3 to 6.

Referring toFIGS. 3 to 5, the integrated-type transformer200includes one bobbin270, the first to third coils240to260corresponding to the first to third inductors L1to L3wound around the bobbin270, and a plurality of magnetic members210to230.

As shown inFIG. 4, the bobbin270has a top surface of a rectangular shape, a first pin part276A is formed on a first side end, and a second pin part276B is formed on a second side end opposite to the first side end.

The first pin part276A may include a plurality of pins275A connected to the first inductor L1of the PFC circuit130, where the pins275A may include pins connected to the first and second nodes n1and n2and a sensing pin.

The second pin part276B may include a plurality of pins275B connected to the third inductor L3of the LLC transformer of the voltage converting unit140. For example, the second pin part276B may include six pins.

In addition, the bobbin270may further include two side pins274provided on a side surface thereof, and the side pins274may be connected to the third and fourth nodes n3and n4.

The bobbin270includes a first winding part271connected to the first pin part276A, a second winding part272connected to the second pin part and an inserting part273formed between the first and second winding parts271and272.

Each of the first and second winding parts271and272may have a cylindrical shape including a hole therein, where the hole is formed toward the pin part.

The inserting part273may cross an end side of the bobbin270and may be formed in a central region thereof. The inserting part273has a space A for receiving a linear-type magnetic member230among a plurality of magnetic members. The linear-type magnetic member230may be called an I-shaped magnetic member.

The bobbin270may further include a supporting part277formed at both sides of the first and second winding parts271and272to dispose bending-shaped magnetic members210and220, but it may be modified according to a design.

The first coil240constituting the first inductor L1of the PFC circuit130is wound around the first winding part271of the bobbin270and the second and third coils220and230of the second and third inductors L2and L3constituting the LLC transformer are wound around the second winding part272.

As shown inFIG. 3, the second and third coils220and230are wound while being spaced apart from each other, so that a part of the second winding part272is exposed.

That is, the second and third coils220and230signify the primary and secondary coils of the transformer, and thus, are wound around the second winding part272while being spaced apart from each other by a required insulating interval (for example, 3 mm).

In this case, as shown inFIG. 3, the second coil250is wound in a direction adjacent to the first coil240and the third coil260is wound while being spaced apart from the second coil250.

In the first to third coils240to260wound like the above, both ends of the first coil240are connected to the pin275A of the first pin part276A so that both ends of the first coil240are electrically connected to the first and second nodes n1and n2, both ends of the second coil250are connected to the side pin274so that both ends of the second coil250are electrically connected to the third and fourth nodes n3and n4, and both ends of the third coil260are connected to the pin275B of the second pin part276B so that both ends of the third coil260are electrically connected to the fifth and sixth nodes n5and n6.

The first and second winding parts271and272may include a plurality of slits spaced apart from each other by the same interval, and the coils are wound between the slits.

A plurality of magnetic members210to230are inserted into the bobbin270around which the coils240to260are wound.

That is, the magnetic members210to230include two bending-type magnetic members210and220, and a linear-type magnetic member230.

The two bending-type magnetic members210and220have the same shape.

In this case, as shown inFIG. 6A, the two bending-type magnetic members210and220may have an E-shape. To the contrary, the two bending-type magnetic members210and220may have a U-shape as shown inFIG. 6B.

As shown inFIG. 6A, a single linear-type magnetic member230may exist. To the contrary, two linear-type magnetic members230may exist as shown inFIG. 6C.

In this case, when one linear-type magnetic member230exists, it is preferable that the one magnetic member230is thickly formed to have an area equal to the sum of the areas of two linear-type magnetic members230.

In other words, the linear-type magnetic member230must hold the magnetic flux for the PFC circuit, and at the same time, must hold the magnetic flux for the transformer.

Thus, the linear-type magnetic member230is formed to have a cross-sectional area, such that the linear-type magnetic member230can hold all magnetic fluxes of the PFC circuit and the transformer.

In this case, the two bending-type magnetic members210and220have the same shape.

Thus, the cross-sectional area of the linear-type magnetic member230preferably is at least twice larger than that of one of the bending-type magnetic member210or220

Hereinafter, the details will be described in more detail.

FIGS. 3 and 5show the transformer employing two bending-type magnetic members210and220having an E-shape and one linear-type magnetic member230having an I-shape, where each of the E-shaped bending-type magnetic members210and220includes a body part disposed in parallel to the I-shaped linear-type magnetic member230and three leg parts extending perpendicularly to the body part.

The leg part interposed between the other leg parts is coupled to the bobbin270to be inserted into the holes of the first and second winding parts271and272, so that the magnetic flux may be transmitted to the magnetic members210to230.

An air gap is formed between the linear-type magnetic member230and the bending-type magnetic member210disposed at the inductor L1of the PFC circuit130such that the interference of magnetic flux may be reduced.

In this case, the linear-type magnetic member230and the bending-type magnetic member210may be spaced apart from each other by a predetermined gap. To the contrary, an insulating material such as resin may be formed between the linear-type magnetic member230and the bending-type magnetic member210.

The magnetic members210to230may be formed of Mn—Zn ferrite having high permeability, a low loss, high saturation magnetic flux density, stability and a low production cost, but the embodiment is not limited by a type or quality of a material of the magnetic member.

As described above, according to the embodiment, only one bobbin270is provided and the first inductor of the PFC circuit is disposed to the left of the bobbin270, and the second and third inductors (the primary and second coils) are disposed to the right of the bobbin270so that an integrated-type transformer having a slim configuration can be provided while reducing the interferences between the inductors.

In this case, the leg parts of each of the bending-type magnetic member210and220may have the same length or mutually different lengths. A film may be inserted into the leg part having a shorter length, so that the influence of the inductance may be minimized.

The film may be formed of an insulating material such as plastic or polyester, but the embodiment is not limited thereto.

In this case, a length d3of the first winding part271constituting the PFC circuit130may be shorter than a length d4of the second winding part272constituting the voltage converting unit140. The lengths d3and d4of the first and second winding parts271and272may be adjusted according to the winding numbers of coils.

In the bobbin270, the length d1of a long side of the body part except for the pins275A and275B may be in the range of 3.5 cm to 4 cm, and the length d2of a short side may be in the range of 3.0 cm to 3.3 cm.

As the integrated-type transformer200described above, the linear-type magnetic member230is interposed between the bending-type magnetic members210and220, so that the inductor L1of the PFC circuit130is disposed in parallel to the second and third inductors L2and L3of the transformer in a traversal direction.

FIGS. 6A to 6Dare views illustrating a shape of a magnetic member according to an embodiment.

As shown inFIG. 6A, the magnetic member according to an embodiment includes one linear-shaped magnetic member230and two E-shaped magnetic members210and220disposed at both sides of the linear-shaped magnetic member230.

In this case, if one linear-shaped magnetic member230is provided and the bending-type magnetic member is formed in an E-shape, a cross-sectional area of a bottom surface of the linear-shaped magnetic member is determined by the cross-sectional areas of leg parts of the E-shaped magnetic members210and220.

That is, the linear-shaped magnetic member230must hold all magnetic fluxes for the E-shaped magnetic members210and220.

In this case, each of the E-shaped magnetic members210and220includes an upper leg part, a lower leg part and a middle leg part.

The cross-sectional area a of the upper leg part may be equal to or different from that a′ of the lower leg part. However, the cross-sectional area a″ of the middle leg part must be at least larger than the sum of the areas a and a′ of the upper and lower leg parts.

Meanwhile, the magnetic fluxes through the E-shaped magnetic members210and220are branched upwardly and downwardly of the linear-shaped magnetic member230after flowing out through the middle leg part.

Thus, the cross-sectional area b of the bottom surface of the linear-shaped magnetic member230preferably is equal to or larger than those a″ of the middle leg parts of the E-shaped magnetic members210and220.

In addition, as shown inFIG. 6B, the magnetic member according to an embodiment includes one linear-shaped magnetic member230and two U-shaped magnetic members210and220disposed at both sides of the linear-shaped magnetic member230.

In this case, the linear-shaped magnetic member230is configured with a single linear-shaped magnetic member. When the bending-type magnetic member is formed in a U-shape, a cross-sectional area of a bottom surface of the linear-shaped magnetic member230is determined by the cross-sectional areas of leg parts of the U-shaped magnetic members210and220.

That is, the linear-shaped magnetic member230must hold all magnetic fluxes for the U-shaped magnetic members210and220.

Thus, it is preferable that the cross-sectional area B of the bottom surface of the linear-shaped magnetic member230is at least twice larger than those B of the middle leg parts of the E-shaped magnetic members210and220.

That is, the U-shaped magnetic members210and220have the same size and shape. Each of the U-shaped magnetic members210and220is symmetrical in the longitudinal direction. That is, each of the U-shaped magnetic members210and220has upper and lower leg parts, the cross-sectional areas A of which are equal to each other.

Thus, the cross-sectional area of the linear-shaped magnetic member230is at least twice larger than those A of the U-shaped magnetic members210and220.

As shown inFIG. 6C, the magnetic member according to an embodiment includes two linear-shaped magnetic members231and232, and two E-shaped magnetic members210and220disposed at both sides of the linear-shaped magnetic members231and232.

In this case, the two linear-shaped magnetic members231and232have the same size and area.

Thus, preferably, as described inFIG. 6A, the cross-sectional area b′ of the bottom surface of each of the two linear-shaped magnetic members231and232is a half of or larger than the cross sectional area a″ of the middle leg part of each E-shaped magnetic member210and220.

As shown inFIG. 6D, the magnetic member according to an embodiment includes two linear-shaped magnetic members231and232, a U-shaped magnetic member210disposed to the left of the linear-shaped magnetic members231and232, and an E-shaped magnetic member220disposed to the right of the linear-shaped magnetic members231and232.

In this case, it is preferable that an area B of each of the two linear-shaped magnetic members231and232is equal to or larger than that of the U-shaped magnetic member210.

Hereinafter, an integrated-type transformer according to another embodiment will be described in detail with reference toFIGS. 7 to 10.

FIG. 7is a schematic perspective view showing an integrated-type transformer according to another embodiment.FIG. 8is a view showing a first modification example of the integrated-type transformer ofFIG. 7.FIG. 9is a view showing a second modification example of the integrated-type transformer ofFIG. 7.FIG. 10is a view showing a third modification example of the integrated-type transformer ofFIG. 7.FIGS. 11A and 11Bare concept views illustrating magnetic flux flows according to current directions.

Referring toFIGS. 7 and 4, the integrated-type transformer200A includes one bobbin270, the first to third coils240,251and261corresponding to the first to third inductors L1to L3wound around the bobbin270, and a plurality of magnetic members210to230.

The bobbin270has a shape substantially equal to that ofFIG. 4.

However, a first pin part276A may include a plurality of pins275A connected to the first inductor L1of the PFC circuit130, where the pins275A may include pins connected to the first and second nodes n1and n2and a sensing pin.

The second pin part276B may include a plurality of pins275B connected to the second inductor L2of the LLC transformer of the voltage converting unit140, and may be connected to third and fourth nodes n3and n4.

In addition, the bobbin270may further include six side pins274provided on a side surface thereof, and the side pins274may be connected to the fifth and sixth nodes n5and n6connected to the second inductor L2.

The bobbin270includes a first winding part271connected to the first pin part276A, a second winding part272connected to the second pin part and an inserting part273formed between the first and second winding parts271and272.

Each of the first and second winding parts271and272may have a cylindrical shape including a hole therein, where the hole is formed toward the pin part276A and276B.

A linear-type magnetic member230is received in the inserting part273.

The first coil240constituting the first inductor L1of the PFC circuit130is wound around the first winding part271of the bobbin270and the second and third coils251and261of the second and third inductors L2and L3constituting the LLC transformer are wound around the second winding part272.

As shown inFIG. 7, the second and third coils220and230are wound while being spaced apart from each other, so that the second winding part272is exposed to an outside.

In this case, as shown inFIG. 7, the third coil261is wound in a direction adjacent to the first coil240and the second coil251is wound while being spaced apart from the third coil261.

In the first to third coils240,251and261wound like the above, both ends of the first coil240are connected to the pin275A of the first pin part276A so that both ends of the first coil240are electrically connected to the first and second nodes n1and n2, both ends of the third coil261are connected to the side pin274so that both ends of the third coil261are electrically connected to the fifth and sixth nodes n5and n6, and both ends of the second coil251are connected to the pin275B of the second pin part276B so that both ends of the second coil251are electrically connected to the third and fourth nodes n3and n4.

Meanwhile, differently from that ofFIG. 7, any side pins274are not formed in the integrated-type transformer200B ofFIG. 8, but pins connected to the fifth and sixth nodes n5and n6are further formed in the second pin part276B ofFIG. 4, so that the circuit connections may be implemented with only both pin parts276A and276B. As shown inFIG. 9, the integrated-type transformer200C may further include pins which are formed in the first pin part276A to be connected to the fifth and sixth nodes n5and n6. As shown inFIG. 10, the pin connected to the fifth node n5may be formed in the first pin part276A and the pin connected to the sixth node n6may be formed in the second pin part276B.

As shown inFIG. 9, the pins connected to the fifth and sixth nodes n5and n6are further formed in the first pin part276A, such that the pins are formed at both sides of the bobbin. Thus, the design freedom may be secured so that the process complexity may be reduced.

As shown inFIGS. 8 to 10, when the pins connected to the fifth and sixth nodes n5and n6are further formed in the first and second pin parts276A and276B of the primary or secondary side, the fifth and sixth nodes n5and n6are too closed to each other so that they may be short-circuited with each other. To prevent the short circuit describe above from occurring, the pins may be covered with tubes, respectively.

Differently from the PFC transformer200ofFIG. 3, according to the integrated-type transformer (200A-D), the third coil261of the secondary side is disposed to be adjacent closely to the first coil240constituting the inductor L1of the PFC circuit.

The integrated-type transformer200A may have magnetic flux flows offset against each other in the linear-type magnetic member as shown inFIG. 8a, or have magnetic flux flows superimposed onto each other according to current polarities in the linear-type magnetic member as shown inFIG. 8b.

When the magnetic fluxes are superimposed onto each other, the superimposed magnetic flux may be concentrated on one side according to the air gap and the number of wound coils of the coil wound leg part of the bending-type magnetic member210.

For example, when the magnetic flux of the PFC circuit130exerts an influence on the voltage converting unit140, the magnetic flux exerts an influence on an output ripple so that the entire system may be unstable.

Thus, according to the integrated-type transformer200A ofFIG. 7, an air gap is formed between the linear-type magnetic member230and the bending-type magnetic member210disposed at the inductor L1of the PFC circuit130, such that the interference of magnetic flux may be reduced.

That is, differently from the integrated-type transformer200ofFIG. 3, in case ofFIG. 7, the third coil262of the secondary side is disposed to be adjacent closely to the first coil240constituting the inductor L1of the PFC circuit.

As shown inFIG. 7, a degree of interference may be confirmed by measuring a coupling constant after winding coils as shown inFIG. 7as following table 1.

Referring to table 1, it is observed that the coupling constant becomes lowered if the winding is implemented as shown inFIG. 7.

That is, the mutual coupling of the integrated-type transformer ofFIG. 7is small so that the resonance current may be not oscillated, thereby stabilizing the operating characteristics.

Hereinafter, the scheme of forming an air gap will be described.

FIG. 12Ais a view illustrating an integrated-type transformer having a side air gap.FIG. 12Bis a view illustrating the variation of a magnetic flux of an integrated-type transformer having a side air gap.

Referring toFIG. 12A, a plurality of magnetic members210to230constituting an integrated-type transformer includes two bending-type magnetic members210and220, and a linear-type magnetic member230.

The two bending-type magnetic members210and220have the same shape.

In this case, the two bending-type magnetic members210and220may have an E-shape.

The E-shaped bending-type magnetic members210and220each includes an I-shaped body part, an upper leg part extending from an upper portion of the body part in a direction perpendicular to the body part, a lower leg part extending from a lower portion of the body part in a direction perpendicular to the body part, and a central leg part extending from a central portion of the body part in a direction perpendicular to the body part.

In this case, the air gap S may be formed between the upper and lower leg parts of the E-shaped bending-type magnetic member210(which corresponds to a magnetic member constituting the PFC circuit) and the linear-type magnetic member230. The air gap formed like the above will be called a side air gap.

The air gap may be formed by grinding the ends of the upper and lower leg parts of the bending-type magnetic member210. Differently from the above, the air gap may be formed by inserting an insulating material between the upper and lower leg parts and the linear-type magnetic member.

When a variation of magnetic flux of the integrated-type transformer to which the side air gap described above is examined, as shown inFIG. 12B, it may be confirmed that the magnetic flux flows to an outside of the magnetic member.

That is, when the side air gap described above is applied, the magnetic flux flow is strong, so that interference may be generated between the PFC circuit and the transformer to exert an influence on the device reliability.

FIG. 13Ais a view illustrating an integrated-type transformer having a central air gap.FIG. 13Bis a view showing the variation of a magnetic flux in an integrated-type transformer having a central air gap.

Referring toFIG. 13A, a plurality of magnetic members210to230constituting the integrated-type transformer includes two bending-type magnetic members210and220, and a linear-type magnetic member230.

The two bending-type magnetic members210and220have the same shape.

In this case, the two bending-type magnetic members210and220may have an E-shape.

The E-shaped bending-type magnetic members210and220each includes an I-shaped body part, an upper leg part extending from an upper portion of the body part in a direction perpendicular to the body part, a lower leg part extending from a lower portion of the body part in a direction perpendicular to the body part, and a central leg part extending from a central portion of the body part in a direction perpendicular to the body part.

In this case, the air gap S may be formed between the central leg part of the E-shaped bending-type magnetic member210(which corresponds to a magnetic member constituting the PFC circuit) and the linear-type magnetic member230. The air gap formed like the above will be called a central air gap.

The air gap may be formed by grinding the end of the central leg part of the bending-type magnetic member210. Differently from the above, the air gap may be formed by inserting an insulating material between the central leg part and the linear-type magnetic member.

When a variation of magnetic flux of the integrated-type transformer to which the central air gap described above is examined, as shown inFIG. 13B, it may be confirmed that the magnetic flux flow occurs only in the magnetic members.

That is, it is known that the magnetic flux flow of the integrated-type transformer having the central air gap is more stable than that of the integrated-type transformer having the side air gap. Therefore, it is preferable to form the air gap in a form similar to that of the central air gap.

Hereinafter, the interference control according to an embodiment will be described with reference toFIGS. 14 to 17.

FIG. 14is a graph showing the voltage gain characteristic of a transformer according to the related art.FIGS. 15 and 16are graphs showing the operating frequency (switching frequency) of a PFC circuit.FIG. 17is a graph showing the voltage gain characteristic of the transformer compensated according to an embodiment.

The operating frequency (resonance frequency) of the LLC transformer may be set to be varied according to a power capacity.

In this case, as shown inFIG. 14, when a resonance point (slant line region) of the LLC transformer is determined in the band of 100 kHz to 130 kHz, the operating frequency of the PFC circuit is shown inFIGS. 15 and 16.

In this case, a rated load PFC switching frequency overlaps an LLC resonant frequency at several voltages.

When the frequencies overlap each other, the resonance current may be oscillated so that an error may occur.

To this end, as shown inFIG. 15, an inductor and a capacitor are designed to allow the LLC resonant frequency to be about ⅓ to about ⅔, preferably ½ of the operating frequency of the PFC circuit, that is, to be in the range of 50 kHz to 70 kHz, so that the overlap may be prevented from occurring. When the operating frequency of the transformer is designed to be greater than half of the maximum operating frequency of the PFC circuit, the overlap may be most effectively prevented from occurring.

Hereinafter, the above will be described in more detail.

FIG. 18is a view showing waveforms of each part when an operating frequency is set according to the related art.FIG. 19is a view showing waveforms of each part when an operating frequency is set according to an embodiment.

First, a main specification of a power supply related toFIG. 18is as follows.

InFIG. 18, VQ1represents the voltage between both terminals of a switching device constituting the PFC circuit, and IT1represents the current passing through both terminals of the switch device constituting the PFC circuit.

In addition, VQ2represents the voltage between both terminals of a switching device constituting the transformer, and IT2represents the current passing through both terminals of the switch device constituting the transformer.

As described above, according to the related art, the operating frequency of the PFC circuit was set at a minimum of 95 kHz and at a maximum of 360.5 kHz.

The operating frequency of the transformer was set at 120 kHz without regard to any operating frequencies of the PFC circuit.

Thus, as shown in the lower drawing ofFIG. 18, the operating frequency of the transformer is set to be too lowered, and it may be confirmed that an oscillation is observed at a time point when the operating frequency of the PFC circuit is approximate to that of the transformer, that is, the operating frequency of the PFC circuit is equal to 104.1 kHz and the operating frequency of the transformer is equal to 114.5 kHz.

Next, a main specification of a power supply related toFIG. 19is as follows.

InFIG. 19, VQ1represents the voltage between both terminals of a switching device constituting the PFC circuit, IT1represents the current passing through both terminals of the switch device constituting the PFC circuit

In addition, VQ2represents the voltage between both terminals of a switching device constituting the transformer, and IT2represents the current passing through both terminals of the switch device constituting the transformer.

As described above, the operating frequency of the PFC circuit according to the related art was set at a minimum of 95 kHz and a maximum of 360.5 kHz.

In addition, the operating frequency of the transformer was set at 251.9 kHz which is greater than half of 360.5 kHz, the maximum operating frequency of the PFC circuit.

Thus, it may be confirmed that the circuit is stably operated without any oscillating phenomena by setting the operating frequency of the transformer into a value greater than half of the maximum operating frequency of the PFC circuit.