KR101254257B1 - Flat Transformer for high frequency. - Google Patents

Abstract

The present invention relates to a high frequency flat transformer, and more particularly, to apply a flat transformer as a high frequency transformer that occupies the largest proportion of the design of a switching mode power supply (SMPS). It relates to a high frequency flat transformer that can provide.
The high frequency flat transformer of the present invention,
In the high frequency flat transformer,
At least one magnetic core having a cross-sectional shape having a hollow portion and having an annular shape;
A primary winding coil continuously passing through the at least one magnetic core;
And at least one secondary winding coil passing through only one magnetic core of the at least one magnetic core, wherein each of the secondary winding coils is connected to each other.
Through the present invention, by applying a flat transformer as a high frequency transformer that occupies the largest proportion of the design of a switching mode power supply (SMPS), it is possible to provide a few primary windings, high frequency characteristics and low leakage inductance.

Description

Flat Transformer for high frequency.

The present invention relates to a high frequency flat transformer, and more particularly, to apply a flat transformer as a high frequency transformer that occupies the largest proportion of the design of a switching mode power supply (SMPS). It relates to a high frequency flat transformer that can provide.

Conventional high-power drivers typically include a constant voltage and constant current circuit by attaching a resistor to a general-purpose switching mode power supply (SMPS) or by adding a current regulator of a linear regulator type.

In particular, a transformer is used to provide a high output. The transformer is composed of a magnetic core 10 and a coil 20, as shown in FIG. 1A, and magnetic flux penetrates the magnetic core.

The transformer's coil is wound around the magnetic material in a copper wire to generate magnetic flux by the input power source and regenerates electrical energy for loading.

It is also a device that is expected to play a big role as a medium for advanced power energy state conversion in the future when designing LED drivers and when the capacity of SMPS becomes large and high.

In general, LED is a semiconductor light with energy conversion efficiency of 43%, which is high in visible light conversion efficiency. In comparison with luminous efficiency, mercury lamp used as a street light source is 35 ~ 65 [lm / W], and metal halide is 65 ~ 100. Considering the [lm / W], the luminous efficiency is high at 100 ~ 130 [lm / W] for the high output 3W LED.

The interest in energy saving is an essential requirement for all power equipments. Especially, support measures for LED lighting related to lighting systems are emerging, and related companies and R & D departments are rapidly responding to standardization and dissemination. .

There are many problems of the power supply of the conventional LED lighting device. Especially, the SMPS applied to the existing high power LED driver is caused by the voltage drop generated by connecting 3 to 6 or more LEDs per string in series. It is difficult to equalize the light source characteristics, and the longer the string, the more sensitive it is to be affected by the influence of the array structure, the operating conditions, and the lighting environment of the LED array. Even though it is limited to about 85 ~ 89%, the need for a new type of high efficiency SMPS structure is emerging to expect more than 90%.

In addition, in terms of current control, if a current larger than the allowable current flows, the linearity is lost due to heat loss, which may cause a decrease in lifespan, such as a decrease in luminous efficiency and burnout. The lack of countermeasures against temperature rise for the stability of the LEDs can lead to the shortage of LED lighting.

In addition, due to the bulky and heavy structure, problems with the design and installation of the LED lighting fixtures occur, resulting in an increase in the size of the entire fixture or difficulties in terms of design and design. Filled, waterproof SMPS is emerging for outdoor LED lighting, but it can be said to be quite large in terms of volume and weight.

Therefore, the necessity of a switch mode power supply (SMPS) having a high efficiency performance that can support the high performance of the LED is highlighted, and the efficiency of the SMPS applied to the LED lighting device is large in efficiency and performance of the entire lighting device As it affects the efficiency of the whole lighting system, the market needs for high-integration and miniaturization technology through the application of resonant circuit, soft switching circuit, and lossless snubber circuit has been increased. In case of LED drive using commercial AC power, AC-DC power supply is essential, and high efficiency control method using control method such as PFC function or resonant switching method is essential for performance.

In addition, the thermal performance, efficiency, volume, etc. of the power supply have a great effect on the actual system, and the LED lighting device has a higher efficiency than the conventional lighting source, but the lighting efficiency or performance is highly dependent on the driver's performance. Performance stabilization and high efficiency are regarded as essential elements, and various methods to reduce the leakage inductance of transformer by using high frequency characteristics to realize high efficiency SMPS have been introduced, but are limitedly used due to the number of primary and secondary windings. It is true.

For example, the description has been made of a half bridge converter in a lighting driving apparatus disclosed in Korean Patent Publication No. 2009-0128652, but still has to configure the primary and secondary windings in the same manner to provide high leakage inductance.

Korean Patent Publication No. 2009-0128652 (2009.12.16)

Therefore, the present invention has been proposed in view of the problems of the prior art as described above, and an object of the present invention is to apply a flat transformer as a high frequency transformer that occupies the largest proportion of the design of a switching mode power supply (SMPS). To provide high frequency and low leakage inductance with the bow.

In order to achieve the object of the present invention,

High frequency flat transformer according to an embodiment of the present invention,

In the high frequency flat transformer,

At least one magnetic core having a cross-sectional shape having a hollow portion and having an annular shape;

A primary winding coil continuously passing through the at least one magnetic core;

At least one secondary winding coil passing through only one of the magnetic cores of the at least one magnetic core; comprising, each of the secondary winding coils are characterized in that the connection to each other Will be able to solve.

High frequency flat transformer according to the present invention having the above configuration and action,

It can provide driver power circuit for LED lighting device with high efficiency and high stability, and it provides lighting power that can extend the number of strings compared to conventional LED lighting device by providing high power density LED driver which is the advantage of flat transformer. It will provide an effect to improve the.

This results in a better effect that enables the development of LED lighting devices with better color uniformity and stable lighting quality between strings than conventional LED lighting devices.

In addition, by providing a thermal design for the stabilization of the LED power supply and a high power supply for low stability LED lighting device, it provides an effect of improving performance and improving durability and stability.

In addition, by providing an instrument that can upgrade the control technology to one step further through high frequency PWM control of 200 KHz or more, it will lay the foundation for the development of other application devices by analyzing and using the electromagnetic characteristics of the flat transformer's ferrite core. Could be.

On the other hand, by providing power supply of high output LED lighting device in terms of economic and industrial aspects, it is possible to achieve high added value through the reduction of production cost, and in the case of various SMPS products, the PC is the mainstream in the medium-sized SMPS. As it is applied to various applications in reality, it can be an opportunity to increase the diversity and stability of functions.

In addition, to solve the problem of high efficiency and price, which is one of the difficulties of the widespread use of LED lighting device can provide a better effect that can be extended to the power supply of various applications such as medical, communication.

In addition, by applying a flat transformer as a high frequency transformer that occupies the largest portion of the design of the switching mode power supply (SMPS), it is possible to provide a few primary windings, high frequency characteristics and low leakage inductance.

Figure 1a is an exemplary view showing a conventional transformer.
Figure 1b is an exemplary view showing a flat transformer applied to the present invention.
1C is an exemplary view showing the shaping of a matrix structure.
FIG. 1D is an exemplary view illustrating a power conversion in which two unit parts are connected in a matrix structure.
Figure 2 is a transformer basic structure of the half bridge converter of the SMPS for the LED lighting device to which the flat transformer according to an embodiment of the present invention.
Figure 3 is an exemplary view showing the shape of the flat transformer of the converter 9: 1 of the SMPS for the LED lighting device to which the flat transformer according to an embodiment of the present invention.
4 is an electric circuit diagram of a flat transformer module of the SMPS for the LED lighting device to which the flat transformer according to an embodiment of the present invention.
5 is a graph showing the core loss versus the magnetic flux density in the Gauss of the flat transformer according to an embodiment of the present invention.
6 is a graph showing a hysteresis characteristic curve of a magnetic core applied to a flat transformer according to an embodiment of the present invention.
7 is a conceptual diagram illustrating a connection state of a magnetic core applied to a flat transformer according to an embodiment of the present invention according to the shape of an actual magnetic core.
8 illustrates a magnetic core applied to a flat transformer according to an embodiment of the present invention.

High frequency flat transformer according to an embodiment of the present invention for achieving the above object,

In the high frequency flat transformer,

A magnetic core having an annular shape while having a cross-sectional shape having a hollow portion therein;

A primary winding coil passing through the magnetic core;

And a secondary winding coil passing through the magnetic core. The winding ratio between the primary winding coil and the secondary winding coil is one to one.

At this time, the magnetic core,

At least one is configured, characterized in that to form a matrix structure.

On the other hand, the high frequency flat transformer according to another embodiment of the present invention,

In the high frequency flat transformer,

At least one magnetic core having a cross-sectional shape having a hollow portion and having an annular shape;

A primary winding coil continuously passing through the at least one magnetic core;

And at least one secondary winding coil passing through only one magnetic core of the at least one magnetic core, wherein each of the secondary winding coils is connected to each other.

At this time, of the primary winding coil,

It is characterized in that the winding is applied in three turns.

At this time, in accordance with the required voltage of the magnetic core,

The number and the number of turns of the winding of the primary winding coil are inversely proportional to the design.

At this time, of the high frequency flat transformer,

The secondary winding is characterized by having a center tap.

At this time, the magnetic core,

It is characterized by applying a high frequency ferrite core.

Hereinafter, the embodiment of the high frequency flat transformer according to the present invention will be described in detail.

Switching type DC-DC converter, which is a constant voltage power supply, is a device that converts a predetermined DC power source to a desired DC level power source, and converts DC into AC through a switching operation, and then boosts the voltage with a transformer. After stepping down, rectification is performed to transform the DC voltage.

There are various topologies such as a forward method, a flyback method, a half-bridge method, and a full-bridge method.

Among the various converters, the asymmetric PWM half-bridge converter and the resonant halfbridge converter derived from the half-bridge method reduce switching loss through zero voltage switching. It is widely used in applications requiring high efficiency.

Figure 1b is an exemplary view showing a high frequency flat transformer according to an embodiment of the present invention.

That is, since the plurality of cores 10 are designed in a matrix and manufactured by reducing the number of windings of the main winding, they have very low leakage inductance and exhibit excellent high frequency response characteristics.

The matrix structure refers to a structure consisting of a constant arrangement of several small parts, and the parts constituting the circuit of one independent structure form small parts and unit parts, and several of them are arranged in a predetermined pattern so that electrical conductors are coupled to each other. It means a structure that establishes the required performance.

That is, at least one magnetic core according to an embodiment of the present invention is configured, and forms a matrix structure.

For example, when three magnetic cores are used, the primary winding coils passing through each magnetic core pass continuously, and the secondary winding coils pass through each one of the magnetic cores as in the other embodiment. It means to make.

Therefore, the magnetic core can be reduced or widened according to the amount of current demanding current, thereby providing a better effect of elastic current operation.

In particular, in the structure of the flat transformer, the winding number is reduced to reduce the leakage inductance or to minimize the number of windings to reduce the heat generation and loss caused by the winding is formed by the arrangement of the unit parts.

1C shows the shaping of a matrix structure according to the present invention.

As shown in Figure 1c, the high frequency flat transformer according to the present invention,

Magnetic core 110 having an annular shape while having a cross-sectional shape having a hollow portion therein;

A primary winding coil 200 passing through the magnetic core;

And a secondary winding coil 300 passing through the magnetic core. The winding ratio between the primary winding coil and the secondary winding coil is one-to-one.

The above configuration is the structure of the unit part, the unit part is Vp = Vs, Ip = Is, and the winding ratio of the primary (primary side) and secondary (secondary side) sides is 1: 1 and provides only electrical insulation. It does not convert power into a form that is normally combined.

The number of turns of the high frequency transformer is summarized using Equation 1 below using Faraday's law.

(수식1)

(Equation 1)

Here, Kf = 4.44 constant, Bac = magnetic flux density according to the operation, f means the operating frequency, Ac = the area of iron.

Therefore, as the frequency increases, the magnetic flux density increases, or the iron area increases, the number of turns decreases.

Matrix transformers with high frequency power conversion should have a low number of turns and a simple structure.

The transformer for the actual power conversion has a stacked structure of such unit components.

As a result, in the conventional winding type high frequency transformer, it is difficult to widen the winding area due to the structure in which the windings are laminated, but the present invention can provide a high frequency because the flat surface can be used, and the high current density is increased, and the number of turns is significant. This will provide a better effect that can be reduced.

FIG. 1D is an exemplary view illustrating a power conversion in which two unit parts are connected in a matrix structure.

That is, as shown in Figure 1d, the high frequency flat transformer according to another embodiment of the present invention,

At least one magnetic core (110a, 110b) having an annular shape while having a cross-sectional shape having a hollow portion therein;

A primary winding coil 200 continuously passing through the at least one magnetic core;

At least one or more secondary winding coils 300a and 300b passing through only one of the at least one magnetic cores, wherein each of the secondary winding coils is connected to each other. do.

That is, as shown in the figure, in the present invention, two magnetic cores are configured, but three, four, five, etc. may be continuously configured as necessary.

For example, if two annular magnetic cores are configured, the primary winding coil 200 passes through the two magnetic cores continuously, but the secondary winding coils 300a and 300b are the same as the primary winding coils. It does not pass at once, but passes one by one.

For example, the secondary winding coil of 300a passes through the magnetic core of 110a, and the secondary winding coil of 300b passes through the magnetic core of 110b.

Then, each secondary winding coil is to be connected (connected) to each other.

In addition, it is a structure that minimizes the number of turns of the winding so that magnetic saturation is not made.

In addition, two unit parts are connected in series and parallel in a matrix structure to represent a form in which power conversion is performed.

As shown in FIG. 1D, the conversion ratio has a structure of 1: 2.

In the structure of SMPS including the flat transformer, the structure of the flat transformer is the most important key.

In particular, in the high frequency SMPS, the conventional transformer is a constraint on the generation of higher high frequency due to the large volume and heat dissipation.

In the winding structure of the flat transformer according to the present invention, the conventional transformer is wound around the primary winding and the secondary winding to one core, so that the number of windings increases, so that the primary and secondary leakage inductance becomes very large.

In addition, when one transformer is applied, a hot spot phenomenon occurs in which the volume becomes large and heat concentrates on one part.

At this time, the leakage magnetic flux of the inductance is equal to Equation (2).

수식(2)

Equation (2)

Where N is the number of turns, A _e [Cm 2] is the cross-sectional area of the core, μ is the permeability of the core in air, and l [cm] is the average length of the magnetic flux.

In Equation (2), the leakage inductance of the transformer is proportional to the square of the number of turns, so a method for reducing the number of turns should be considered.

Item Existing high frequency method Flat transformer method Number of cores One many 1st round player many little Leakage Inductance many little High frequency low Big Heat concentration Big little Etc Difficulty of Package Low profile

Table 1 compares the characteristics of the conventional winding type high frequency transformer and the flat transformer.

As described above, the flat transformer has a small number of primary windings, which inevitably leads to a small leakage inductance, thereby providing an advantage of low heat concentration.

As shown in FIG. When the secondary winding consists of a single winding and the primary winding passes through the core module, the coupling between the primary winding and the secondary winding is greatly improved, resulting in a very small leakage inductance value.

One flat transformer consists of a ferrite core with two quadrilateral secondary windings and a secondary winding through each core consisting of a pair of copper plates with opposite ends of the core having the same winding ends. Has a structure.

The secondary winding has a structure in which when the two cores are connected, the secondary winding passes through the two cores in succession and attaches to the inner surface of the ferrite core.

In the conventional flat transformer, only one turn is wound around the primary winding, so that a large number of elements are required to drop the voltage on the secondary side.

Therefore, the amount of power delivered to the secondary side can be lowered by increasing the voltage on the primary side.

That is, the ratio between the primary side and the secondary side can be adjusted by adjusting the ratio of the number of turns of the transformer.

In the conventional winding type high frequency transformer, the primary side is fixed and the secondary side is connected in parallel to secure the power conversion ratio.

In addition, the heat emitted by the secondary winding can generate heat to the outside through the thin wall of the rectangular ferrite core, eliminating the hot spot phenomenon occurring in the conventional transformer, and it is possible to operate at a high current density even at a high frequency.

The most preferred embodiment of the present invention is a half-bridge method using a flat transformer, and the SMPS to which the second transformer is applied has a center tap, and thus may be applicable to a full bridge, push-pull converter topology, and the like.

Figure 2 shows the shape of the ideal transformer.

The magnetizing inductance is given by equation (3) according to the actual inductor.

수식(3)

Equation (3)

Integrating this is the same as Equation (4).

수식(4)

Formula (4)

The magnetization current is determined by the integration of the winding voltage.

The magnetization current and the winding current are independent quantities.

Volt-second equilibrium condition is i _M at steady state (T _s ) = i _M Since it becomes (0), it is the same as Formula (5).

수식(5)

Formula (5)

On the other hand, in the basic arrangement of the conventional flat transformer, a method in which the number of turns on the primary side and the secondary side has one turn number each is mainly applied.

On the other hand, in the present invention, when the primary winding is 3 turns to increase the conversion ratio of the flat transformer, the conversion ratio is the number of modules N _e. Multiply the number of turns of the primary winding to make the conversion ratio V / 9.

In this way, the conversion ratio of the flat transformer can be varied, providing a better effect of producing a more precise SMPS.

FIG. 3 shows the structure of a flat transformer with a conversion ratio of 9: 1 having three turns as described above.

The circuit design method according to the present invention is applicable to a full bridge, half bridge, push-pull converter topology and the like because the SMPS in the case of applying a flat transformer has a structure in which the secondary winding always has a center tap.

That is, in accordance with the required voltage of the magnetic core,

The number and turns of the windings of the primary winding coil are inversely proportional to the design.

For example, in the case of the conventional transformer can only be converted to 400V to 200V, in the case of the flat transformer of the present invention can be converted to 380V to 40V.

In other words, when designing by applying flat transformer, efficiency can be increased by reducing margin width according to voltage detection. Also, unlike conventional winding transformer, it is possible to apply several modules. It is possible to provide advantages that are easy to calculate.

4 is an electrical circuit diagram of a flat transformer module.

Based on this arrangement, modularization and unit modules according to the modularization may be established to establish various types of center tap transformers.

In particular, SMPS applied to LED lighting load has low voltage and high current characteristics, so the turns ratio should be high and current loss should be low.

If the LEDs are connected in parallel, the lighting quality of the LEDs will be higher, but the current can be larger, which can lead to a thicker wire.

SMPSs for LED lighting must be suitable for these low voltage, high current load characteristics.

5 is a graph showing the core loss versus the magnetic flux density in the Gauss of the flat transformer according to an embodiment of the present invention.

That is, the magnetic core applied to the present invention is a ferrite-based core, Figure 5 shows the core loss versus magnetic flux density in the Gauss.

Experiments showed that the operating characteristics were excellent in the high frequency band of 300 KHz.

6 is a graph showing a hysteresis characteristic curve of a magnetic core applied to a flat transformer according to an embodiment of the present invention.

As shown in FIG. 6, the loss region of the magnetic core is shown in the hysteresis characteristics, and it can be seen that the characteristics of the ferrite system have a structure that minimizes the loss at a high current density.

7 is a conceptual diagram illustrating a connection state of a magnetic core applied to a flat transformer according to an embodiment of the present invention according to the shape of an actual magnetic core.

8 illustrates a magnetic core applied to a flat transformer according to an embodiment of the present invention.

7 to 8 are conceptual views and actual pictures showing the connection state of the magnetic core applied to the flat transformer according to the shape of the actual magnetic core, and implements the shape according to the circuit diagram of FIG.

Therefore, the magnetic core in the present invention is characterized by applying a high frequency ferrite core, for example, because it is used in the 300khz ~ 1mhz high frequency band is to apply a high frequency ferrite core.

Through the above configuration, it is possible to provide a driver power circuit for a high efficiency and high stability LED lighting device, and to provide a high power density LED driver, which is an advantage of a flat transformer, to extend the number of strings compared to a conventional LED lighting device. The lighting device can provide the effect of improving the lighting characteristics.

This results in a better effect that enables the development of LED lighting devices with better color uniformity and stable lighting quality between strings than conventional LED lighting devices.

It will be appreciated by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not restrictive.

The scope of the invention is indicated by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the invention. do.

110, 110a, 110b: magnetic core
200: primary winding coil
300, 300a, 300b: secondary winding coil

Claims (7)

delete In the high frequency flat transformer,
At least one magnetic core having a cross-sectional shape having a hollow portion and having an annular shape;
A primary winding coil continuously passing through the at least one magnetic core;
And at least one secondary winding coil passing through only one magnetic core of the at least one magnetic core, wherein each of the secondary winding coils is connected to each other.
Of the primary winding coil,
It is characterized in that the winding is applied in three turns,
Of the magnetic core in accordance with the required voltage,
The number and the number of turns of the winding of the primary winding coil is inversely proportional to the design,
Of the high frequency flat transformer,
The secondary winding is characterized by having a center tap,
The magnetic core,
A high frequency flat transformer applying a high frequency ferrite core and having at least one core to form a matrix structure.
delete delete delete delete delete

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