Patent Publication Number: US-11651889-B2

Title: Reinforced insulation transformer and design method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2019-0026117, filed on Mar. 7, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present disclosure relates to a reinforced insulation transformer and a design method thereof, and more particularly, to a transformer capable of implementing a reinforced insulation structure between a primary power source and a secondary power source with a minimum volume, and a design method thereof. 
     2. Discussion of Related Art 
     Various electronic devices or apparatuses require various types of power. Accordingly, each of the electronic devices or apparatuses is provided with a power supply that converts alternating current (AC) power supplied from the outside into power required by the corresponding electronic device or apparatus. 
     Examples of such a power supply include a series regulator method and a switching mode method. 
     The series regulator method is a method of converting AC power using a transformer and is mainly used for a TV receiver, a cathode ray tube (CRT) monitor, and the like. Such a series regulator method has a simple peripheral circuit and is inexpensive but has a disadvantage in that a great deal of heat is generated, power efficiency is low, and a volume thereof is large. 
     The switching mode method is a method of converting AC power using a switching element and has an advantage in that little heat is generated, power efficiency is high, and a volume thereof is small in comparison to the series regulator method. A power supply of such a switching mode method is typically referred to as a switching mode power supply (SMPS). In particular, the SMPS is high in efficiency, durable, and advantageous in miniaturization and being light weight, and thus used as a power supply for most electronic devices, equipment, and systems for communication, industrial purposes, personal computers (PCs), office automation (OA) equipment, and home appliances. 
     The SMPS is basically provided with a transformer. Here, the transformer for an SMPS includes a core that is a magnetic body, a bobbin that is a frame for insulating and winding, and primary and secondary windings that are wound on the bobbin and transfer primary power and secondary power, respectively. Accordingly, the SMPS may convert power using the phenomenon of electromagnetic induction that is generated in the primary and secondary windings. 
     Meanwhile, an inverter is a device for converting direct current (DC) into AC and generates an AC voltage by switching a DC voltage using a switching element, which is turned on/off according to a pulse width modulation (PWM) signal, and outputs the generated AC voltage to loads. The SMPS is provided to supply power to a controller and other peripheral devices of the inverter. That is, in the inverter, low voltage power generated by the SMPS is processed and used for the purpose of operation, protection, and control. 
     In the SMPS of the inverter, each power source (or each winding) is electrically insulated from each other (hereinafter referred to as “insulation”). Here, between power sources (for example, between primary power sources, between the secondary power sources, or between the primary power source and the secondary power source), an insulation class of the power source is determined according to the usage position of each power source. Here, the insulation class is an insulation criterion for safety and may be classified into three types of functional insulation, basic insulation, and reinforced insulation. 
     In particular, when the secondary power source is an externally located power source (for example, an I/O power source) that may be in direct contact with a user, the reinforced insulation should be necessarily implemented. However, the conventional method for implementing the reinforced insulation merely proposes to simply increase an insulation distance between a primary power source and a secondary power source. Accordingly, when the conventional method is applied, there is a problem that the volume of a transformer for an inverter SMPS increases due to an increase in the insulation distance. 
     SUMMARY 
     The present disclosure is directed to providing a transformer capable of implementing a reinforced insulation structure between a primary power source and a secondary power source with a minimum volume, and a design method thereof. 
     However, objectives to be achieved by embodiments of the present disclosure are not limited to the above-described objective, and other objectives, which are not described above, may be clearly understood by those skilled in the art through the following specification. 
     According to an aspect of the present disclosure, there is provided a reinforced insulation transformer, in which a secondary winding is wound on a primary winding so that the primary winding and the secondary winding have a stacked structure and satisfy a reinforced insulation criterion, wherein each of the primary winding and the secondary winding includes a conducting wire and an insulation outer layer that surrounds the conducting wire, and the insulation outer layer of the secondary winding has more layers or a greater thickness than the insulation outer layer of the primary winding. 
     The secondary winding may include the insulation outer layer that is composed of a plurality of layers to satisfy a withstand voltage of a basic insulation criterion. 
     The insulation outer layer of the secondary winding may have a triple layer. 
     A lead-out portion of each of the primary winding and the secondary winding may be surrounded by an insulating tube, and the lead-out portion may be adjacent to a pin. 
     The insulating tube may include a Teflon tube. 
     A total barrier distance of each of the primary winding and the secondary winding may be smaller than a separation distance of the reinforced insulation criterion. 
     The total barrier distance of each of the primary winding and the secondary winding may be within a range of separation distances that satisfy the basic insulation criterion. 
     The reinforced insulation transformer according to an embodiment of the present disclosure may be included as a configuration of a power supply for an inverter. 
     According to another aspect of the present disclosure, there is provided a design method of a reinforced insulation transformer in which a primary winding and a secondary winding form a stacked structure and a reinforced insulation criterion is satisfied between the primary winding and the secondary winding, the design method including forming the primary winding by winding, and forming the secondary winding by winding on the primary winding, wherein each of the primary winding and the secondary winding includes a conducting wire and an insulation outer layer that surrounds the conducting wire, and the insulation outer layer of the secondary winding has more layers or a greater thickness than the insulation outer layer of the primary winding. 
     The design method of the reinforced insulation transformer according to the embodiment of the present disclosure may further include surrounding a lead-out portion of each of the primary winding and the secondary winding by an insulating tube, wherein the lead-out portion is adjacent to a pin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, and advantages of the present disclosure will become more apparent to those of ordinary skill in the art by describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which: 
         FIG.  1    illustrates a block configuration diagram of a general switching mode power supply (SMPS); 
         FIG.  2    illustrates a front photograph of a reinforced insulation transformer according to an embodiment of the present disclosure; 
         FIG.  3    illustrates a photograph in a case in which an insulating layer is removed in  FIG.  2   ; 
         FIG.  4    illustrates a perspective photograph of the reinforced insulation transformer according to an embodiment of the present disclosure; 
         FIG.  5    illustrates a configuration of the reinforced insulation transformer according to an embodiment of the present disclosure, which is illustrated with reference to  FIG.  4   ; 
         FIG.  6    illustrates an example of a core ( 100 ), a primary winding ( 310 ), a secondary winding ( 320 ), and an insulating layer ( 400 ); 
         FIG.  7    illustrates a part of a cross-section of  FIG.  5   ; 
         FIG.  8    illustrates a state in which lead-out portions ( 311  and  321 ) are connected to pins ( 500 ) in a conventional transformer; 
         FIG.  9    illustrates a state in which lead-out portions ( 311  and  321 ) are connected to pins ( 500 ) in the reinforced insulation transformer according to an embodiment of the present disclosure; and 
         FIG.  10    illustrates a flowchart of a design method of the reinforced insulation transformer according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The above-described objects and means of the present disclosure and the effects associated therewith will become more apparent through the following detailed description in conjunction with the accompanying drawings. Accordingly, those skilled in the art to which the present disclosure pertains can readily implement the technical spirit of the present disclosure. In addition, when it is determined that detailed descriptions of related well-known functions unnecessarily obscure the gist of the present disclosure during the description of the present disclosure, the detailed descriptions will be omitted. 
     Terms used herein are for the purpose of describing embodiments only and are not intended to limit the present disclosure. In the present specification, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well in some cases, unless the context clearly indicates otherwise. In the present specification, terms such as “comprises,” “comprising,” “includes,” “including,” “has,” and/or “having,” do not preclude the presence or addition of one or more other components other than the components mentioned. 
     In the present specification, terms such as “or,”, “at least one,” and the like may represent one of the words listed together or may represent a combination of two or more. For example, “A or B” and “at least one of A and B” may include only one of A or B, and may include both A and B. 
     In the present specification, descriptions following “for example” may not exactly match the information presented, such as cited characteristics, variables, or values, and embodiments of the disclosure according to various embodiments of the present disclosure should not be limited by effects such as modifications including limits of tolerances, measurement errors, and measurement accuracy, and other commonly known factors. 
     In the present specification, when it is described that one component is “connected” or “joined” to another component, it should be understood that the one component may be directly connected or joined to another component but an additional component may be present therebetween. However, when one component is described as being “directly connected,” or “directly coupled” to another component, it should be understood that the additional component may be absent between the one component and another component. 
     In the present specification, when one component is described as being “on” or “facing” another component, it should be understood that the one component may be directly in contact with or connected to another component, but additional component may be present between the one component and another component. However, when one component is described as being “directly on” or “in direct contact with” another component, it should be understood that there is no additional component between the one component and another component. Other expressions describing the relationship between components, such as “between ˜,” “directly between ˜,” and the like should be interpreted in the same way 
     In the present specification, terms such as “first” and “second” may be used to describe various components, but the components should not be limited by the above terms. In addition, the above terms should not be interpreted as limiting the order of each component but may be used for the purpose of distinguishing one component from another. For example, a “first element” could be termed a “second element”, and similarly, a “second element” could also be termed a “first element”. 
     Unless defined otherwise, all terms used herein may be used in a sense commonly understood by those skilled in the art to which the present disclosure pertains. In addition, it should be understood that terms, such as those defined in commonly used dictionaries, will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the attached drawings. 
       FIG.  1    illustrates a block configuration diagram of a general switching mode power supply (SMPS). 
     The SMPS is a device that converts alternating current (AC) power using a switching element, and as shown in  FIG.  1   , may include a noise filter  10 , an input rectification smoothing circuit  20 , a converter  30 , a control circuit  40 , and an output rectification smoothing circuit  50 . However,  FIG.  1    is an example of a configuration of an SMPS and is not limited to an SMPS for an inverter. 
     The noise filter  10  is a component that removes the noise of an AC power P 1  that is input through an input terminal. That is, the noise filter  10  may prevent the noise in the input terminal from damaging internal circuit elements and may minimize a phenomenon in which a current has irregularly fluctuated. However, the noise filter  10  is a component for an auxiliary function such as preventing power noise generated in the SMPS from flowing into an input system and thus may not be an essential component of the SMPS for an inverter. 
     The input rectification smoothing circuit  20  is a component that performs rectification and smoothing functions on input power and may include an input rectification circuit and an input smoothing circuit. Here, the input rectification circuit may generate a rectified power P 2  by converting the AC power that has passed through the noise filter  10  or the like. For example, the input rectification circuit may include a bridge diode circuit or the like, but the present disclosure is not limited thereto. In addition, the input smoothing circuit may generate a smoothed power P 3  by converting the rectified power P 2  having a ripple current which has passed through the input rectification circuit. That is, the input smoothing circuit may cause some constant voltage to be output by lowering a high voltage and raising a low voltage. For example, the input smoothing circuit may include a capacitor or an inductor, but the present disclosure is not limited thereto. 
     The converter  30  is a component that converts the smoothed power P 3  into a power P 4  of a desired magnitude. That is, the converter  30  may adjust the magnitude of the final output direct current (DC) power according to an on/off time of the switching element. For example, the switching element may be formed of transistors such as a gate turn-off thyristor (GTO), a bipolar junction transistor (BJT), an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or the like, but the present disclosure is not limited thereto. 
     In particular, the converter  30  is the main part responsible for power conversion and may be classified into many types of converters according to the magnitude of an input/output change ratio and a circuit configuration. For example, the converter  30  may be mainly divided into a non-insulated type and an insulated type depending on the presence or absence of a high-frequency transformer. Here, the non-insulated type may include a buck type, a boost type, a buck-boost type, a C&#39;uk type, and the like, and the insulated type may include a flyback type, a forward type, a full-bridge type, a half-bridge type, and the like, but the present disclosure is not limited thereto. 
     The control circuit  40  is a component that controls the converter  30 . That is, the control circuit  40  may control the on/off time of the switching element. For example, a pulse width modulation (PWM) method or a pulse frequency modulation (PFM) method may be used as the control method, but the present disclosure is not limited thereto. In addition, the control circuit  40  may be a feedback control circuit for stabilizing the final output DC voltage or may further include the feedback control circuit. 
     The output rectification smoothing circuit  50  is a component that performs the rectification and smoothing functions on the power P 4 , which is converted by the converter  30 , to generate the final power and may include an output rectification circuit and an output smoothing circuit. That is, the output rectification circuit may additionally perform a rectification function on the power that is converted by the converter  30 . For example, the output rectification circuit may include a diode or the like, but the present disclosure is not limited thereto. In addition, the output smoothing circuit may generate a smoothed final power P 5  by converting the power that has passed through the output rectification circuit. That is, the output smoothing circuit may cause some constant voltage to be output by lowering a high voltage and raising a low voltage. For example, the output smoothing circuit may include a capacitor or an inductor, but the present disclosure is not limited thereto. 
       FIGS.  2  and  4    illustrate a front photograph and a perspective photograph of a reinforced insulation transformer according to an embodiment of the present disclosure, respectively, and  FIG.  3    illustrates a photograph in a case in which an insulating layer is removed in  FIG.  2   . 
     The reinforced insulation transformer according to the embodiment of the present disclosure uses an electromagnetic induction phenomenon to output secondary power in which the magnitude of primary power is lowered. For example, the reinforced insulation transformer according to the embodiment of the present disclosure is a component that is included in an SMPS, especially an SMPS for an inverter, and may be provided between the input rectification smoothing circuit  20  and the converter  30 , or between the converter  30  and the output rectification smoothing circuit  50 . 
     That is, the reinforced insulation transformer according to the embodiment of the present disclosure receives a smoothed power P 3  as primary power and outputs secondary power, in which the magnitude of the primary power is lowered according to an electromagnetic induction phenomenon, to transmit the secondary power to the converter  30 . Further, the reinforced insulation transformer according to the embodiment of the present disclosure receives a power P 4 , which is converted by the converter  30 , as primary power, and outputs secondary power, in which the magnitude of the primary power is lowered according to an electromagnetic induction phenomenon, to transmit the secondary power to the output rectification smoothing circuit  50 . However, the present disclosure is not limited to being used only as a power conversion configuration of the above-described SMPS and may also be used as a power conversion configuration of various other electronic devices and apparatuses. 
       FIG.  5    illustrates a configuration of the reinforced insulation transformer according to the embodiment of the present disclosure, which is illustrated with reference to  FIG.  4   , and  FIG.  6    illustrates an example of a core  100 , a primary winding  310 , a secondary winding  320 , and an insulating layer  400 . Further,  FIG.  7    illustrates a part of a cross-section of  FIG.  5   . That is,  FIG.  7    illustrates a part of a cut surface between A and A′ viewed from B direction in  FIG.  5   . 
     Referring to  FIGS.  5  to  7   , the reinforced insulation transformer according to the embodiment of the present disclosure may include a core  100 , a bobbin  200 , a winding  300 , an insulating layer  400 , pins  500 , and barriers  600 . 
     The core  100  is a component that includes a magnetic material and may be centered when the winding  300  is wound. That is, the core  100  may be a component for smoothing energy transfer from a primary side to a secondary side. 
     The bobbin  200  is a component for supporting or housing the remaining components of the present disclosure, such as the core  100 , the winding  300 , the insulating layer  400 , and the pin  500 . Here, the bobbin  200  may include a pin portion  210 , a central portion  220 , and a top portion  230 . That is, the pin portion  210  is a portion that supports the pin  500 . The central portion  220  is a portion that supports the core  100 , the winding  300 , the insulating layer  400 , the barriers  600 , and the like, and corresponds to a portion of a hollow part in which the core  100 , the winding  300 , the insulating layer  400 , the barrier  600 , and the like are seated. In addition, the top portion  230  is a portion that is provided on the opposite side of the pin portion  210  with respect to the central portion  220 . 
     The winding  300  is a component which is wound and in which an electromagnetic induction phenomenon is generated. Here, the winding  300  may include a primary winding  310  to which primary power is transmitted and a secondary winding  320  to which secondary power is transmitted. That is, the primary power may include high voltage power such as 200 V and 400 V. In addition, the secondary power may include low voltage power such as 12 V and may be a power source with which a user may come into direct contact. 
     A power conversion principle by the primary winding  310  and the secondary winding  320  is as described below. That is, when AC power is applied to the primary winding  310 , magnetic flux is generated by the current of the corresponding power. Here, electromotive force may be induced in the secondary winding  320  in a direction in which a change in the generated magnetic flux is disturbed. 
     The primary winding  310  and the secondary winding  320  are composed of conducting wires  310   a  and  320   a , which are made of a conductive material, and coated portions that surround the conducting wires  310   a  and  320   a , respectively. That is, the primary winding  310  and the secondary winding  320  may include insulation outer layers  310   b  and  320   b , respectively, which are made of an insulating material such as enamel. 
     Referring to  FIG.  6   , the primary winding  310  and the secondary winding  320  may have a structure stacked on each other and separated (hereinafter, a distance separated in such a manner is referred to as a “vertical separation distance”) from each other, and the insulating layer  400  may be provided therebetween. That is, after the primary winding  310  is wound on the core  100 , the insulating layer  400  covers the primary winding  310 . Thereafter, the secondary winding  320  is wound again on the insulating layer  400 , and the insulating layer  400  may cover the secondary winding  320  again. However, unlike the above, the insulating layer  400  may be omitted, which is provided in the space of the vertical separation distance between the primary winding  310  and the secondary winding  320 . 
     Meanwhile, although  FIGS.  6  and  7    illustrate that one primary winding  310  and one secondary winding  320  are provided, the present disclosure is not limited thereto. That is, a plurality of primary windings  310  and a plurality of secondary windings  320  may be further stacked. In particular, the plurality of primary windings  310  may be connected to each other, or the plurality of secondary windings  320  may be connected to each other, and in this case, the effect of increasing the number of turns of the primary winding  310  or the secondary winding  320  may occur. 
     As the primary winding  310  and the secondary winding  320  are stacked on each other, an electromagnetic induction phenomenon occurs in the primary winding  310  and the secondary winding  320 . As a result, the high voltage primary power, which is transmitted to the primary winding  310 , may be induced to the low voltage secondary power on the secondary winding  320  by the electromagnetic induction phenomenon. Here, the magnitude of the secondary power that is induced on the secondary winding  320  may be affected by the magnitude of the primary power, the number of turns of each of the windings  310  and  320 , and the separation distance between the windings  310  and  320 . 
     In particular, the primary winding  310  and the secondary winding  320  each have two ends, and each end of the primary winding  310  and the secondary winding  320  may be connected to the pin  500 . Here, the pin  500  is a component that is connected to each of the windings  310  and  320  to transfer an input/output of a power source and may be connected to other terminals, elements, or devices. 
     Specific portions of the primary winding  310  and the secondary winding  320  may be exposed to the outside of the bobbin  200 , which are referred to as “lead-out portions  311  and  321 ”. That is, among the windings  310  and  320 , the lead-out portions  311  and  321  are portions adjacent to the pins  500  and may correspond to portions between ends of the windings  310  and  320  and winding portions of the windings  310  and  320 , respectively, and may be exposed on the pin portion  210  of the bobbin  200 . 
     Meanwhile, the winding portions of the primary winding  310  and the secondary winding  320  and the insulating layer  400  that covers the winding portions may be located at the central portion  220  of the bobbin  200 . Here, the primary winding  310  and the secondary winding  320  may be wound in a space between the barriers  600 . 
     The barriers  600  are walls that are formed on both sides of the winding portion of each of the windings  310  and  320  and secure the separation distance (that is, an insulation distance) between the primary winding  310  and the secondary winding  320 . That is, the primary winding  310  includes a winding portion in a space between the barriers  600  (hereinafter referred to as a “first barrier”) provided on both sides of the layer thereof, and the secondary winding  320  includes a winding portion in a space between the barriers  600  (hereinafter referred to as a “second barrier”) provided on both sides of the layer thereof. Accordingly, the winding portion end of the primary winding  310  and the winding portion end of the secondary winding  320  have an effect of being separated from each other by the space that is occupied by the first barrier and the second barrier. In particular, the barrier  600  is higher than the region of the winding portion of each of the windings  310  and  320 . That is, each of the windings  310  and  320  is wound only in a space (hereinafter referred to as a “winding space”) that is at a height lower than and between two barriers  600  provided on both sides of the winding portion of the primary winding  310  or the secondary winding  320 . Accordingly, the greater the space occupied by the barrier  600  (the length of an arrow on a reference numeral ‘600’ in  FIG.  7   ) (hereinafter referred to as a “barrier distance”), the narrower the winding space for each of the windings  310  and  320 . However, in each of the barriers  600 , the barrier distances may not be the same. 
     Hereinafter, a design method according to the present disclosure to satisfy reinforced insulation in an insulation class will be described. 
     Each power source (or each winding) is insulated from each other, and here, an insulation criterion for safety, that is the ‘insulation class’, is determined between each power source (for example, between primary power sources, between secondary power sources, or between a primary power source and a secondary power source) depending on where each power source is used (internal or external). 
     Here, the terms “internal” and “external” refer to positions where the corresponding power source is used and are related to whether the user is in direct contact with the corresponding power source. That is, an internal power source is a primary power source or a secondary power source that is not in direct contact with the user and means a power source that is used only inside the device or apparatus. On the contrary, an external power source is a secondary power source that can directly contact the user and means a power source that may be exposed to the outside of the device or apparatus. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 (Primary power 
                 (Primary power 
               
               
                   
                   
                 source for 
                 source for 
               
               
                   
                   
                 inverter) 
                 inverter) 
               
               
                   
                   
                 Minimum 
                 Minimum 
               
               
                   
                   
                 separation 
                 separation 
               
               
                 Insulation 
                   
                 distance 
                 distance 
               
               
                 class 
                 Target power source 
                 at 200 V 
                 at 400 V 
               
               
                   
               
             
            
               
                 Functional 
                 Between primary power 
                 1.5 mm 
                 3 mm 
               
               
                 insulation 
                 sources 
               
               
                   
                 Between internal 
               
               
                   
                 secondary power sources 
               
               
                   
                 Between external 
               
               
                   
                 secondary power sources 
               
               
                 Basic 
                 Between primary power 
                   3 mm 
                 5.5 mm   
               
               
                 insulation 
                 source and internal 
               
               
                   
                 secondary power source 
               
               
                 Reinforced 
                 Between primary power 
                 5.5 mm 
                 8 mm 
               
               
                 insulation 
                 source and external 
               
               
                   
                 secondary power source 
               
               
                   
                 Between internal 
               
               
                   
                 secondary power source 
               
               
                   
                 and external secondary 
               
               
                   
                 power source 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, the insulation class may be classified into three types, which are functional insulation, basic insulation, and reinforced insulation, and the reinforced insulation is the highest insulation criterion among them. That is, it may be seen that the degree of insulation criterion increases from the functional insulation to the reinforced insulation. 
     The functional insulation is a criterion between primary power sources, between internal secondary power sources, or between external secondary power sources. For example, for an inverter, when the primary power source is 200 V, in order to satisfy the functional insulation, the corresponding power sources must be separated at least 1.5 mm from each other. In addition, for an inverter, when the primary power source is 400 V, in order to satisfy the functional insulation, the corresponding power sources must be separated at least 3 mm from each other. 
     The basic insulation is a criterion between a primary power source and an internal secondary power source. For example, for an inverter, when the primary power source is 200 V, in order to satisfy the basic insulation, the corresponding power sources must be separated at least 3 mm from each other. In addition, for an inverter, when the primary power source is 400 V, in order to satisfy the basic insulation, the corresponding power sources must be separated at least 5.5 mm from each other. 
     The reinforced insulation is a criterion between a primary power source and an external secondary power source, or between an internal secondary power source and an external secondary power source. For example, for an inverter, when the primary power source is 200 V, in order to satisfy the reinforced insulation, the corresponding power sources must be separated at least 5.5 mm from each other. In addition, for an inverter, when the primary power source is 400 V, in order to satisfy the reinforced insulation, the corresponding power sources must be separated at least 8 mm from each other. 
     The present disclosure proposes a design method of the transformer that satisfies reinforced insulation. That is, according to the embodiment of the present disclosure, there is provided a transformer in which the insulation class between the primary power source and the secondary power source or between the secondary power sources (that is, between the primary winding  310  and the secondary windings  320  or between the secondary windings  320 ) satisfies the criterion of reinforced insulation. 
     Meanwhile, in the transformer, the separation distance between the primary winding  310  and the secondary winding  320  should satisfy the minimum separation distance that is presented by the corresponding insulation criterion. To this end, the vertical separation distance in the stacked portion of the primary winding  310  and the secondary winding  320  is designed to satisfy the corresponding minimum separation distance. In addition, the total barrier distance of the primary winding  310  and the secondary winding  320  is also designed to satisfy the corresponding minimum separation distance criterion. 
     Here, the total barrier distance means a sum between the barrier distance of the first barrier, which is provided at one side of the winding portion of the primary winding  310 , and the barrier distance of the second barrier that is provided at one side of the winding portion of the secondary winding  320  adjacent to the primary winding  310 . That is, the total barrier distance is the sum of the barrier distances of the first barrier that is located on a lower side and the second barrier that is located on an upper side. 
     However, in a conventional transformer, in order to satisfy the reinforced insulation criterion, the above-described separation distance must be increased such that a problem arises in that the volume of the transformer becomes large. 
     Meanwhile, even when it does not satisfy the criteria for the minimum separation distance, the corresponding insulation class may also be applied when a power line (first winding or second winding), which transmits the corresponding power, satisfies the criteria for withstand voltage. Here, the withstand voltage is affected by the degree of overlaps of an insulation outer layer of the winding or the thickness of the insulation outer layer. That is, as the insulation outer layer is composed of a plurality of layers and the number of overlapping layers increases, or the thickness of the insulation outer layer becomes thicker, the withstand voltage increases, and the insulation class may also be increased. 
     However, even in this case, the volume of the transformer should be minimized, and thus it may be more desirable that the insulation outer layer  320   b  of the secondary winding  320 , rather than the primary winding  310 , satisfies the above-described condition. This is because the number of turns of the secondary winding  320  is smaller than that of the primary winding  310  such that even when the above-described conditions are adopted, an increase in volume due to the adoption may be small. Accordingly, the present disclosure proposes an insulation class improvement that is obtained by an increase in withstand voltage (hereinafter referred to as a “first proposal”) by designing the insulation outer layer  320   b  of the secondary winding  320  to have a greater number of overlaps or thicker than the insulation outer layer  310   a  of the primary winding  310 . 
     When the secondary winding  320  is designed with a power line that satisfies the withstand voltage of a predetermined insulation class or more according to the first proposal, the minimum separation distance for the corresponding insulation class does not have to be satisfied. As a result, the total barrier distance for each of the primary winding  310  and the secondary winding  320  may be smaller than before. 
       FIG.  8    illustrates a state in which the lead-out portions  311  and  321  are connected to pins  500  in the conventional transformer, and  FIG.  9    illustrates a state in which the lead-out portions  311  and  321  are connected to pins  500  in the reinforced insulation transformer according to the embodiment of the present disclosure. 
     Meanwhile, the lead-out portions  311  and  321  are portions that are exposed to the outside among the primary winding  310  and the secondary winding  320 . Here, when the periphery of the lead-out portions  311  and  321  is additionally surrounded by an insulating tube  700 , the withstand voltage or the minimum separation distance in the corresponding region may be increased, and as a result, the insulation class may be increased. Accordingly, the present disclosure further proposes an insulation class improvement that is obtained by designing the lead-out portions  311  and  321  to be additionally surrounded by the insulating tube  700  (hereinafter referred to as a “second proposal”). 
     Here, the insulating tube  700  is a tube made of an insulating material. For example, the insulating tube  700  may include a Teflon tube that easily adheres to the periphery of the lead-out portions  311  and  321  by heating, but the present disclosure is not limited thereto. 
     Referring to  FIG.  8   , in the conventional transformer, the lead-out portions  311  and  321  are not additionally surrounded by the insulating tube  700 . However, in the conventional transformer, there may be a case in which the lead-out portion  311  of the primary winding  310  is surrounded by the insulating tube  700 , but the corresponding processing was not performed for the lead-out portion  321  of the secondary winding  320 . 
     Meanwhile, in the transformer, when there are more than two cases that satisfy the basic insulation (hereinafter referred to as an “additional reinforced insulation condition”), it may be appreciated that between the corresponding power sources the reinforced insulation is satisfied according to the standard of the insulation class. That is, when each of the first proposal and the second proposal satisfies the basic insulation criterion for the additional reinforced insulation condition, the power sources of the transformer may satisfy the reinforced insulation. 
     Accordingly, when the secondary winding  320  is designed with a power line that satisfies the withstand voltage or more of the basic insulation according to the first proposal, and when it is designed such that the lead-out portion  321  of the secondary winding  320 , in addition to the lead-out portion  311  of the primary winding  310 , is also surrounded by the insulating tube  700  according to the second proposal to satisfy the basic insulation or more, the corresponding transformer may satisfy the basic insulation criterion twice or more. As a result, it is possible to implement the reinforced insulation for the corresponding transformer. In this case, in the corresponding transformer, the total barrier distance of each of the primary winding  310  and the secondary winding  320  may become smaller than the minimum separation distance for the reinforced insulation. 
     That is, by implementing the reinforced insulation through satisfying the basic insulation criterion twice as described above, the present disclosure may reduce the insulation distance (that is, the total barrier distance) between the primary power source and the secondary power source, which has been increased in the conventional implementation of the reinforced insulation, so that the size of the barrier  600  may be reduced. As a result, the present disclosure may increase the winding portion of each of the primary winding  310  and the secondary winding  320 , that is, a winding window area. 
     The total barrier distance of each of the primary winding  310  and the secondary winding  320  needs to satisfy only the minimum separation distance of the basic insulation criterion (for example, 3 mm when the primary power source is 200 V, 5.5 mm when the primary power source is 400 V). Accordingly, each total barrier distance may be smaller than the minimum separation distance of the reinforced insulation criterion (for example, 5.5 mm when the primary power source is 200 V, 8 mm when the primary power source is 400 V). As a result, the present disclosure may minimize an increase in volume that has occurred conventionally, that is, an increase in volume to satisfy the total barrier distance in the reinforced insulation. 
     However, in relation to the first proposal, designing and manufacturing the power line directly for changing the withstand voltage to satisfy a specific insulation class in transformer design may increase manufacturing costs, and thus may not be easy in manufacturing conditions. On the other hand, the withstand voltage for each insulation class may be provided as a specification of the power line itself. Accordingly, the present disclosure proposes to use, as the secondary winding  320 , a specific type of power line that satisfies the withstand voltage of the basic insulation among the various power lines on the market that are designed, manufactured and provided. 
     That is, such a specific type of power line may satisfy the withstand voltage of the basic insulation criterion by forming the insulation outer layer of the power line into a plurality of overlapping numbers. In particular, as shown in  FIG.  7   , in the specific type of power line, the insulation outer layer of the power line may have a triple layer. This is because when the number of overlapping layers of the insulation outer layer of the power line is less than 3, the withstand voltage of the basic insulation criterion may not be satisfied, and when the number of overlapping layers of the insulation outer layer of the power line is greater than 3, the secondary winding  320  may become too thick such that the volume occupied by the winding portion of the secondary winding  320  may be increased. 
       FIG.  10    illustrates a flowchart of a design method of a reinforced insulation transformer according to an embodiment of the present disclosure. 
     In summary, as shown in  FIG.  10   , the design method of the reinforced insulation transformer according to the embodiment of the present disclosure may include forming a primary winding (S 100 ), forming a secondary winding (S 200 ), and processing a lead-out portion (S 300 ). 
     In S 100 , a primary winding  310  is formed by winding. Here, the primary winding  310  may be wound around a core  100 , but the present disclosure is not limited thereto 
     In S 200 , a secondary winding  320  is formed by winding on the primary winding  310  with a vertical separation distance therebetween. Here, an insulating layer  400  may be formed in a region of the vertical separation distance between the primary winding  310  and the secondary winding  320 , but the present disclosure is not limited thereto. In particular, in S 200 , the primary winding  310  and the secondary winding  320  may satisfy the contents of the first proposal, the additional reinforced insulation condition, and the like. 
     In S 300 , the primary winding  310  and the secondary winding  320  are surrounded by an insulating tube  700  for each of lead-out portions  311  and  321  of the primary winding  310  and the secondary winding  320 . That is, in S 300 , the primary winding  310  and the secondary winding  320  may satisfy the contents of the second proposal, the additional reinforced insulation condition, and the like. 
     However, in S 100  to S 300 , each component of the transformer, in particular, the primary winding  310  and the secondary winding  320  may include contents described above with reference to  FIGS.  1  to  9   . 
     The present disclosure configured as described above has an advantage that a reinforced insulation structure between a primary power source and a secondary power source can be implemented with a minimum volume. 
     In particular, the present disclosure can reduce an insulation distance between a primary power source and a secondary power source, which has been increased in a conventional implementation of reinforced insulation, by implementing the reinforced insulation through the satisfaction of a basic insulation criterion twice so that the size of a barrier can be reduced, and as a result, a winding portion of each of a primary winding and a secondary winding, that is, a winding window area, can be increased. 
     However, effects to be achieved by embodiments of the present disclosure are not limited to the above-described effects, and other effects, which are not described above, may be clearly understood by those skilled in the art through the following specification. 
     While specific embodiments have been described in the detailed description of the present disclosure, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure is defined not by the described embodiment but by the appended claims and encompasses equivalents that fall within the scope of the appended claims.