Core assembly for magnetic saturation detectors that do not require bias current

Abstract

A magnetic core assembly including a skewed feature that introduces a transverse component into a power flux density vector is disclosed herein. The magnetic core assembly includes a lower core having a center section and an upper core having a center section. The center sections are aligned to form a center column. A power winding that receives current is wound around the center column. The core assembly also includes a power flux density vector having a transverse component and a non-transverse component. The transverse component has a higher magnetic resistance than the non-transverse component. When the assembly is used with a transverse winding, the transverse component from the magnetic core assembly produces a transverse voltage waveform on the transverse winding. The transverse voltage waveform can be observed to detect a change in the sign of the slope of the transverse voltage waveform. The change in the sign of the slope indicates magnetic saturation.

Description

[0001] Application for US patent certificate

[0002] Core assembly for magnetic saturation detectors that do not require bias current

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 888,194, filed on August 16, 2019, which is incorporated herein by reference in its entirety.

[0004] Related Applications

[0005] This patent application is related to patent application 62 / 887,810 entitled "Magnetic Saturation Detector with Single and Multiple Transverse Windings" and patent application 62 / 888,089 entitled "Energy Transfer Element Including A Communication Element", each of which was filed on the same date as this application, each of which is assigned to a common assignee, and each of which has a common inventor. Each of the related applications is incorporated herein by reference in its entirety. Background of the Invention

[0006] 1. Field of the Invention

[0007] The present disclosure describes embodiments of a magnetic core assembly for an inductive element useful for providing a voltage across a transverse winding of the inductive element. The voltage can be monitored to produce a signal directly indicating the onset of magnetic saturation in the inductive element without requiring a bias current in the transverse winding.

[0008] 2. Discussion of related technologies

[0009] Efforts have been made to enable a flyback power supply or other power product including an inductive energy transfer element to deliver maximum output power under a variety of electrical and thermal conditions by extending the available flux density of its coupled inductor to include a saturation flux density.

[0010] Known applications use a transverse winding of an inductive element to detect impending magnetic saturation by processing a voltage signal appearing between the terminals of the transverse winding. A control circuit may be responsive to the voltage signal on the transverse winding to operate the power supply safely near the maximum available flux density of the magnetic material.

[0011] A disadvantage of previous implementations of transverse windings that detect impending magnetic saturation is that they require a current in the transverse winding. This current generates a transverse magnetic field that varies in response to the saturation characteristics of the magnetic material. The varying transverse magnetic field is accompanied by a varying electric field that is observed as a voltage between the terminals of the transverse winding. The need to provide a bias current in the transverse winding increases the complexity of the circuit, reduces the efficiency of the power supply, and generally adds to the cost of the product. Therefore, there is a need for an innovation that produces a signal that directly indicates magnetic saturation without the disadvantages described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0013] Figure 1 is a schematic diagram of an example power supply including a switch-mode power converter with a magnetic saturation detector according to an embodiment of the present disclosure.

[0014] 2 is a perspective view of an example energy transfer element using an example magnetic core assembly with a transverse winding that requires a bias current to detect magnetic saturation.

[0015] 3 is an annotated perspective view of the example magnetic core assembly of FIG. 2 illustrating the path of flux density resulting from current in the power windings and the path of flux density resulting from current in the lateral windings.

[0016] Figure 4 is an annotated perspective view of an example magnetic core assembly including a representation of a transverse winding that does not require a bias current in the transverse winding to detect magnetic saturation.

[0017] Figure 5A is a graph of magnetic flux density in an example magnetic energy transfer element versus current in a power winding of the energy transfer element according to an embodiment of the present disclosure.

[0018] Figure 5B is a graph of magnetic flux density in an example magnetic energy transfer element versus current in a power winding of the energy transfer element when the energy transfer element includes permanent magnets to provide an offset flux density according to an embodiment of the present disclosure.

[0019] Figure 6 is a graph showing a waveform of a current in a power winding of an energy transfer element and a waveform of a voltage across a lateral winding of the energy transfer element according to an embodiment of the present disclosure.

[0020] Figure 7 is a diagram showing more details of an embodiment according to the present disclosure Figure 6 An enlarged portion of a graph of .

[0021] Figure 8 is a planar model of a magnetic core assembly for a magnetic saturation detector that does not require bias current in the transverse windings according to an embodiment of the present disclosure.

[0022] Fig. 9 is a perspective view of another example magnetic core assembly having a transverse winding that does not require a bias current in the transverse winding to detect magnetic saturation according to an embodiment of the present disclosure.

[0023] Fig.10 According to the embodiments of the present disclosure Fig. 9 Annotated perspective view of an example magnetic core assembly showing the path of the flux density originating from the current in the power winding.

[0024] Fig.11 is a perspective view of yet another example magnetic core assembly having a lateral winding that does not require a bias current in the lateral winding to detect magnetic saturation according to an embodiment of the present disclosure.

[0025] Fig.12 According to the embodiments of the present disclosure Fig.11 Annotated perspective view of an example magnetic core assembly showing the path of the flux density originating from the current in the power winding.

[0026] Fig.13 is an annotated perspective view of a portion of a magnetic core assembly emphasizing a center post showing the path of flux density originating from current in a power winding according to an embodiment of the present disclosure.

[0027] Fig.14 is an annotated perspective view of a portion of another magnetic core assembly emphasizing the center post showing the path of flux density originating from current in a power winding according to an embodiment of the present disclosure.

[0028] Fig.15 is an annotated perspective view of a portion of yet another magnetic core assembly emphasizing the center post showing the path of flux density originating from current in a power winding according to an embodiment of the present disclosure.

[0029] In all several views of the accompanying drawings, corresponding reference characters indicate corresponding parts. It will be appreciated by the skilled person that the elements in the accompanying drawings are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the sizes of some elements in the accompanying drawings may be exaggerated relative to other elements to help improve the understanding of various embodiments of the present invention. In addition, common but easily understood elements that are useful or necessary in commercially feasible embodiments are generally not depicted so as to less hinder the viewing of these various embodiments of the present invention. DETAILED DESCRIPTION

[0030] In the following description, many specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that it is not necessary to adopt the specific details to practice the present invention. In other cases, well-known materials or methods are not described in detail to avoid obscuring the present invention.

[0031] Reference throughout this specification to "one embodiment", "anembodiment", "one example" or "an example" means that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment", "in an embodiment", "one example" or "an example" appearing in various places throughout this specification do not necessarily all refer to the same embodiment or example. In addition, specific features, structures or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Specific features, structures or characteristics may be included in integrated circuits, electronic circuits, combinational logic circuits, or other suitable components that provide the described functions. In addition, it should be understood that the drawings provided herewith are used for the purpose of explanation to those of ordinary skill in the art, and the drawings are not necessarily drawn to scale.

[0032] Figure 1 is a schematic diagram 100 of an example power supply configured to operate with a magnetic saturation detector using a single lateral winding that does not require bias current in the lateral winding. Figure 1 The example power supply receives an input voltage V relative to the input return line 104 IN 102 and provides a regulated output to a load 148. The regulated output may be a voltage V relative to the output return line 144. O 154. Current I O 146 or a combination of both.

[0033] Figure 1The example power supply of uses a flyback power converter to produce an output that is isolated from the input current. In other words, a voltage applied between the input return 104 and the output return 144 will produce negligible current. Figure 1 The flyback power converter in the example power supply of 1000 includes an energy transfer element L1 120 having an input power winding P1 118, an output power winding P2 122, and a single lateral winding T1 128. The power windings P1 118 and P2 122 are primarily involved in energy transfer between input and output, while the lateral winding T1 128 is involved in magnetic saturation detection. The clamp circuit 106 is coupled in parallel to the input power winding P1 118. The input switch S1 110 is coupled between the input power winding P1 118 and the input return line 104.

[0034] In operation, the input-referenced controller 132 receives a signal from the output-referenced controller 152 through the galvanic isolator 134 to generate a drive signal 112 that opens and closes the input switch S1 110. An open switch cannot conduct current, while a closed switch can conduct current. The input-referenced controller 132 generates a current I S1 108 is sensed as a current sensing signal 114. In one operating mode, when the current I S1 108 reaches a threshold, the reference input controller 132 may open the input switch S1 110. In another mode of operation, the reference input controller 132 may open the input switch S1 110 when the energy transfer element L1 120 reaches a state of impending magnetic saturation.

[0035] The switching of switch S1 110 generates a pulsating current I in the respective power windings P1 118 and P2 122 of energy transfer element L1 120. P1 116 and I P2 124, and the ripple voltages V1 and V2 across those corresponding windings. The clamp circuit 106 prevents excess voltage on the input power switch S1 110 when the switch is open. The output winding current I P2 124 is rectified by diode 136 and output capacitor C O 138 is filtered to generate an output voltage V at the load 148 O 154 and output current I O 146. Output voltage V O 154. Output current I O146 or a combination of the two can be sensed by the reference output controller 152 as an output sense signal 150. The reference output controller compares the sensed output quantity with the reference value and can communicate with the reference input controller 132 through the current isolator circuit 134 to appropriately switch the input switch S1 110 to obtain the desired output value. The current isolator circuit 134 can include any of many known ways to couple signals between galvanically isolated circuits using optical, magnetic, and capacitive techniques.

[0036] exist Figure 1 In the example power supply of FIG. 1 , the transverse winding T1 128 can respond to the transverse magnetic flux density within the energy transfer element L1 120 to generate a transverse voltage V on the transverse winding T1 128. T1 130 to indicate magnetic saturation.

[0037] FIG. 2 is an example of a Figure 1 200. The example energy transfer element of FIG. 2 is constructed of two RM-type ferrite core-pieces. An upper core member, such as upper core half 207, is assembled on a lower core member, such as lower core half 227. Each magnetic core half has a central column 225 surrounded by a winding 218, which represents one or more power windings, such as Figure 1118 and P2 122 in the power winding. In actual components, the turns of the power winding are usually placed on a separate spool, sometimes called a bobbin or coilformer, which will be assembled on the center column for ease of assembly. FIG. 2 shows a gap 257 in the center column of the assembled half core. The size of the gap is usually selected together with the number of turns on the power winding to set the electrical parameters desired for the specific application. In some applications, the gap contains a permanent magnet to provide a flux density offset to the flux density generated by the current in the power winding. The gap can be implemented using the same top half and bottom half core with a center column of the same length, or using one half core with a center column shorter than the center column of the other half core. Alternatively, a spacer (spacer) composed of an electrically insulating material with a relatively low magnetic permeability can be inserted between the same half cores to distribute the gap between the three vertical structural features. The gap in the center column is insignificant for magnetic saturation detection. As such, illustrations in the present disclosure may show structures with and without a gap in the center post to emphasize that a gap in the center post is not required to practice the invention.

[0038] FIG. 2 also shows a transverse winding 228 that passes through an aperture 247 in the center column 237 of each half core so that the transverse winding is perpendicular to the power winding 218. The aperture 247 in the center of the center column of each half core is a ready-made option in some offerings of RM cores that are equipped with a center hole that accommodates a ferrite slug to adjust the inductance of the power winding after assembly. According to the teachings of the present invention, the transverse winding 228 can replace the ferrite block to cross the adjustment hole to provide a magnetic saturation detector. Other types of ferrite cores can have apertures for other purposes, such as, for example, assembly hardware that can be applied to transverse windings. In cores that are not equipped with suitable apertures, holes can be drilled through the center column. It should be understood that the transverse winding does not have to be geometrically perpendicular to the power winding. Any conductor that completely passes through a turn of the power winding in one direction at any angle can be a transverse winding.

[0039] The lateral winding is usually a single turn, although it can include more than one turn to amplify the voltage V across the winding. Tl 230, the voltage V Tl 230 is generated by the changing transverse flux density when the magnetic material of the core begins to saturate. The embodiment of FIG. 2 shows the transverse current I introduced to detect magnetic saturation. T 255. The alternative core assembly described in the present disclosure does not require a transverse current IT 255 to detect magnetic saturation.

[0040] Those skilled in the art will appreciate that magnetic assemblies and parts of magnetic assemblies can be described by various terms that are not necessarily technically accurate and precise. For example, almost any piece of magnetic material can be referred to as a magnetic core. A complete assembly of several magnetic components that do not include windings can also be generally referred to as a magnetic core. The assembly of a magnetic core generally includes two core pieces. In many assemblies of magnetic cores, such as in the embodiment of FIG. 2, the two core pieces may be almost identical. Therefore, each piece can generally be referred to as a core member or a half core. In fact, a gap in a central column, such as the gap 257 in the assembly of FIG. 2, can be formed by removing material from the central column of only one of the two identical half cores. Even if the piece forming the gap is no longer the same as the piece from which the material is not removed, each piece is still referred to as a half core. The assembly can also be referred to as a core pair. In the present disclosure, the term half core can be used to refer to one of two almost identical pieces in an assembly to distinguish the assembly from an alternative assembly that includes significantly different pieces. For example, an assembly of two E-shaped pieces can have the same geometric features and magnetic properties as an assembly using an E-shaped piece and an I-shaped piece. Although each assembly includes two core members, the EE assembly includes two core halves, while the EI assembly does not. It should be noted that in the practice of this field, each of the core pieces, core members, core elements, core halves, and core assemblies may be referred to as a core.

[0041] FIG. 3 is a perspective view 300 of the structure of FIG. 2 showing the upper core half 307 and the lower core half 327 without the windings. Reference numerals 377 and 387 highlight identical features on the upper core half 307 and the lower core half 327, respectively, which are useful in discussing the relative positions of the two core halves. The windings are removed in FIG. 3 to avoid obscuring the annotation of the flux density vector. A power winding that surrounds the center column and conducts current, such as, for example, winding 218 in FIG. 2 and current I P1 216, will generate power flux density B in the component P , as indicated by the vector B in Figure 3 P The current I in the transverse winding schematically represented by path 328 is T 355 will be generated by vector B T 365 represents the transverse flux density, the vector B T 365 perpendicular to the power flux density vector B in the central column and in the majority of the assembly outside the central column P In addition, the power flux density B from the upper core 307 P The contribution of the lateral component is the power flux density B in the lower core 327 PThe contribution of the transverse component of 328 is canceled, so that the net contribution relative to path 328 is zero. In other words, the geometry of the assembly is such that the vector B of the power flux density relative to the path of the transverse winding P The vector B of the transverse flux density T 355 orthogonal. Thus, the power flux density B P The change of the transverse current I T 355 is usually constant to introduce the transverse flux density B T When the magnetic material begins to saturate, the transverse flux density B T Forced to change. When the power flux density B P and the transverse flux density B T When the vector sum increases to reach the saturation flux density of the magnetic core, the power flux density B P A further increase in forces a transverse voltage V between the terminals of the conductor in path 328. T 330 transverse flux density B T The change of the transverse voltage V T 330 may be processed and interpreted to detect the onset of magnetic saturation.

[0042] Figure 4 is an annotated perspective view 400 illustrating an example magnetic core assembly that does not require bias current in the lateral windings to detect magnetic saturation. Figure 4 The embodiment shown does not show the power windings nor the gap in the center column to avoid distracting from the essential features of the invention. Figure 4 The embodiments in the present invention all use RM type ferrite half core. Figure 4 In the embodiment of FIG. 4 , when viewed from the top, the upper core half 407 is rotated approximately 30 degrees clockwise about its center relative to the lower core half 427. Figure 4 The rotational offset is in contrast to the conventional assembly depicted in FIG. 3 , which aligns the vertical edges of the top and bottom core halves so that the vertical edges are co-linear and the flat vertical surfaces are co-planar. Figure 4 The displacement in can also be gauged by the position of reference marks 477 and 487 corresponding to the respective features highlighted by reference marks 377 and 387 in FIG. 3. Reference marks 477 and 487 are Figure 4 3, reference numerals 377 and 387 are vertically aligned. The rotational displacement between the two core halves can be considered a skewing feature in the assembly of the magnetic core that allows a magnetic saturation detector to determine the onset of magnetic saturation by monitoring the voltage across the lateral windings in the absence of current in the lateral windings.

[0043] Figure 4 A flux density vector B is shown having both horizontal and vertical components in the vertical side of the structure, despite the absence of transverse currents to introduce transverse magnetic fields into the assembly. The rotational offset between the upper core half 407 and the identical lower core half 427 introduces a transverse component in the flux density vector B. Figure 4 The geometry of the assembly ensures that for any orientation of the transverse winding in the path 428 through the opening in the center column, there will be a net magnetic flux density through the surface defined by the conductor that is the transverse winding. That is, when the transverse winding does not have current, there will be a net magnetic flux density through the loop formed by the transverse winding. Changes in the transverse component of the flux density will produce a voltage between the terminals of the transverse winding. In other words, changes in the transverse component of the flux density induce a non-zero transverse voltage V on the transverse winding. T 430, the non-zero transverse voltage V T 430 can be processed to indicate impending magnetic saturation. The saturation characteristics of the magnetic material of the energy transfer element are determined by the transverse voltage V T A feature is produced in the waveform of 430 that allows detection of magnetic saturation during operation of the power supply.

[0044] Figure 5A and Figure 5B The relationship between the magnetic flux density in the energy transfer element and the current in the power winding of the energy transfer element is graphically illustrated. Figure 5A is a graph 500A showing the power winding current relative to the horizontal axis—such as e.g. Figure 1 The power supply I P1 116 - The magnetic flux density is plotted on the vertical axis. More accurately, the horizontal axis represents the sum of the ampere-turns of all power windings, not just the current in a single power winding. Figure 5A The example energy transfer element of has no flux density offset from the permanent magnet, so when the current is at zero, the flux density is at zero.

[0045] Figure 5A The magnetic flux density curve 505 in FIG. 5 highlights several distinguishing features. Curve 505 takes positive and negative values ​​symmetrically about the origin on two axes. For positive current, there is a positive flux density, and for negative current, there is a negative flux density. The characteristics of positive values ​​of current are emphasized in the graph because Figure 1 The current in the example circuit is in one direction only. P1 When increasing from zero, the energy transfer element is in the quasi-linear region B QL 535 until the current reaches a maximum value I corresponding to the upper boundary 525 of the quasi-linear region. MAXIn the quasi-linear region 535, the slope of the curve 505 is positive and relatively constant. In other words, the flux density increases at a nearly constant rate as the current increases. MAX , the slope of the flux density curve 505 decreases, so that for a value greater than the value corresponding to the saturation flux density B SAT 515 saturation current I SAT The current reaches a relatively low constant value. It is important to detect the saturation flux density B SAT 515, because operation at higher flux density values ​​may generate currents that can damage switching devices and other components in the power supply. MAX The quasi-linear region B QL 535 becomes almost constant at currents greater than I SAT Where its slope is much lower and almost constant, there is a region where the slope changes rapidly between two relatively constant values. Where the slope of the flux density changes most rapidly I MAX and I SAT The current between is identified as I KNEE , because it corresponds to a relatively sharp bend in the flux density curve 505. The magnetic saturation detector can indicate that the current corresponding to the current I KNEE Operation at a flux density greater than I SAT Operation at current of .

[0046] Figure 5B is a graph 500B showing the power winding current relative to the horizontal axis—such as e.g. Figure 1 The power supply I P1 116——The magnetic flux density is plotted on the vertical axis. Figure 5A Compared with the curve graph, Figure 5B An example of a graph of an energy transfer element having a flux density offset from a permanent magnet.

[0047] The flux density offset from the permanent magnet causes Figure 5A The curve 505 of FIG. 5 is shifted to the right on the horizontal axis, as shown by Figure 5B As shown by the curve 555 in FIG. QL 535 and saturation flux density B SAT The values ​​of 515 on the vertical axis are unchanged because they are intrinsic properties of the magnetic material of the core. A flux density offset can change the relationship between flux density and external excitation, but it cannot change the intrinsic properties of the magnetic material. A flux density offset from a permanent magnet, such as, for example, a permanent magnet that may be placed in gap 257 of the assembly illustrated in FIG. 2 , is Figure 5B is shown as B OFFSET, the B OFFSET The current I on the horizontal axis P1 A value of zero produces a negative flux density 545 in the energy transfer element.

[0048] The flux density offset increases to reach the quasi-linear region B QL 535 upper boundary 525, saturation value B SAT 515 and the current I required for the flux density where the slope of the curve changes most rapidly P1 In other words, Figure 5A The current I MAX ,I SAT and I KNEE exist Figure 5B were added to I MAXBIAS ,I SATBIAS and I KNEEBIAS Thus, in an energy transfer element using a permanent magnet to provide a flux density offset, a magnetic saturation detector may indicate a current corresponding to I KNEEBIAS Operation at a flux density greater than I SATBIAS Operation at current of .

[0049] Figure 6 is a graph 600 showing the Figure 1 The waveform of the current in the power winding and the waveform of the voltage on the lateral winding of the example energy transfer element operating in the example power supply of FIG. P1 116 is plotted on the vertical axis 610, and the lateral voltage V T1 130 is plotted on the vertical axis 620, both relative to time on the horizontal axis.

[0050] This current is the input voltage V across the power winding P1 118 of the energy transfer element L1 120 when the switch S1 110 is closed and opened. IN 102. The lateral voltage V on the lateral winding T1 128 T1 130 is derived from a mechanism that utilizes the magnetic saturation characteristics of magnetic materials to generate voltage across the transverse windings.

[0051] The saturation characteristic describes the behavior of the total flux density generated by the current in the power winding. The flux density is usually not uniform throughout the magnetic core assembly. The flux density in some parts of the assembly can be greater than the flux density in other parts of the assembly. Therefore, some parts of the assembly can reach the saturation flux density before other parts of the assembly reach the saturation flux density.

[0052] In a conventional core assembly having an opening in the center leg, such as opening 247 in the embodiment of FIG. 3 , the vector of the flux density from the current in the power winding is substantially perpendicular to the vector of the flux density from the current in the lateral windings.

[0053] If Figure 4 As shown in the embodiment of the present invention, the geometry of the magnetic core component can be configured to rotate the vector of the total flux density so that the magnetic flux density vector can contain two components even when the flux density is in the quasi-linear region. The vectors of the two components of the flux density are perpendicular to each other in the magnetic material. One of the components can be a transverse component of the voltage induced in the transverse winding.

[0054] The flux density vector must follow a closed path. The geometry of the core assembly forces the transverse component of the flux density vector to take a path with a higher reluctance than the path of the flux density vector perpendicular to it. An increase in current in the power winding forces the magnitude of the sum of the two components of the flux density to increase, even when the total flux density approaches a saturation value. When a material is saturated, its reluctance to the flux density increases. The flux density in the material along the lower reluctance path is higher than the flux density in the material along the higher reluctance path. Because the saturation characteristic imposes a limit on the increase in the sum of the two vectors, the vector with a higher magnitude on the lower reluctance path will increase at a slower rate than the vector with a lower magnitude along the higher reluctance path. The result is an effective additional rotation of the flux density vector that increases the component of the flux density in the transverse direction, thereby generating a voltage V between the terminals of the transverse winding. T1 rapid increase.

[0055] When the total flux density is in the quasi-linear region ( Figure 5A and Figure 5B B QL 555), the transverse flux density is approximately proportional to the principal flux density, and the voltage on the power winding produces a voltage on the transverse winding that is approximately proportional to the voltage on the power winding - in Figure 6 It is represented as voltage V PP ——At the same time, the power winding conducts current. Due to the voltage V PP is roughly proportional to the voltage on the power winding, so it is when dealing with the transverse voltage V T1 to a known value that can be taken into account when detecting magnetic saturation. Alternatively, V PP There are ways to determine the magnetic saturation, such as, for example, the current I P1 By detecting V T1 Therefore, the signature of the time-varying voltage on the transverse winding can be interpreted to detect magnetic saturation in the energy transfer element.

[0056] To produce Figure 6 An example waveform of Figure 1 The switch S1 110 in the example power supply is closed at time t1. Between time t1 and time t2, the current I P1 Increments from zero to value I MAX 630, and when the controller 132 of the reference input opens the switch, the flux density increases from zero to Figure 5A The quasi-linear region B of the flux density characteristic shown in QL When switch S1 110 is turned off at time t2, the current in power winding P1 118 changes from I MAX changes to zero, while the current in the power winding P2122 increases from zero to maintain the current I corresponding to the current in the power winding P118 MAX The required value of the flux density. The transverse voltage V T1 The polarity changes at time t2 because the flux density that produces the change in voltage across the winding decreases after the switch is opened, while when the switch is closed, the flux density increases. Figure 6 In the embodiment of FIG. 1 , the current in power winding P2 122 decreases to zero at time t3 between time t2 and time t4. The voltage remains at zero between time t3 and time t4 because the flux density does not change during this interval.

[0057] When the switch S1 110 is closed again at time t4, the current I P1 Increase again from zero to above I MAX 630 and I KNEE 640 Both, before the controller 132 of the reference input opens the switch, I SAT 650. When the current I increases P1 More than I MAX At 630, the flux density leaves the quasi-linear range B QL 535, and the lateral voltage V T1 It quickly becomes more positive with a fairly large positive slope 660. The lateral voltage V T1 The maximum positive value 680 is reached at time t5, which corresponds to the maximum positive value 680 at I KNEE The current I at 640 P1 When the current I P1 Passing through I KNEE And at time t6, it is close to I SAT When the final value of 650, the lateral voltage V T1Becoming less positive with a substantially negative slope 670, the controller 132 referenced to the input opens the switch at time t6. When the current in the power winding decreases to zero at time t7 between time t6 and time t8, the transverse voltage V T1 becomes more negative and reaches a maximum negative value.

[0058] Figure 7 yes Figure 6 700, which shows more detail around times t5 and t6. The zoom-in emphasizes the nature of the lateral voltage waveform that allows the circuit to detect magnetic saturation by observing the voltage on the lateral winding.

[0059] Figure 7 It shows that when the current I P1 In the value I KNEE At 640°, the lateral voltage V T1 The extreme value 680 in the waveform. Figure 7 In the embodiment shown, the polarity of the voltage on the lateral winding can be reversed simply by interchanging the two ends of the winding at the voltage sensing terminals, or by reversing the direction of the angular displacement between the upper and lower core halves in the assembly by turning the upper core half counterclockwise rather than clockwise relative to the lower core half when viewed from the top so that the extreme value becomes a valley rather than a peak.

[0060] A polarity-independent characteristic of the extrema is the change in sign of the slope of the waveform from before time t5 to after time t5. Figure 7 A positive slope on the portion 660 before t5 and a negative slope on the portion 670 after t5 are shown. The change in the sign of the slope of the voltage on the transverse winding is an indication of magnetic saturation. If the polarity of the transverse winding is reversed, the slope will be negative before t5 and positive after t5. The change in the sign of the slope is also independent of the magnitude of the extreme value. Since the slope of the transverse voltage waveform changes sign - from positive to negative or from negative to positive, the slope of the transverse voltage waveform must pass through zero. Therefore, a zero-crossing detector that observes the slope of the voltage on the transverse winding can detect magnetic saturation. A controller that disconnects the switch in the power winding in response to the zero-crossing detector sensing the voltage on the transverse winding can control the power supply to operate at its maximum power capability without damage. In practice, to avoid false indications of magnetic saturation, a zero-crossing detector can be selected to observe the voltage on the transverse winding only after the switch has been closed for a threshold time or only when the current in the switch is greater than a threshold current.

[0061] The foregoing embodiments have illustrated the application of a magnetic saturation detector in a power supply having a power converter operating in a discontinuous conduction mode (DCM). That is, within each switching cycle, the current in the power winding and the flux density in the energy transfer element (without a flux density offset) start with a zero value and end with a zero value. In contrast, under different conditions of input voltage, output voltage and load, the power supply can operate its power converter in a continuous conduction mode (CCM). That is, under CCM, the current in the power winding and the flux density (still without a flux density offset in the energy transfer element) do not start and end with a zero value within each switching cycle. When the flux density is in the quasi-linear region B within each CCM switching cycle, the current in the power winding and the flux density in the energy transfer element (without a flux density offset) do not start and end with a zero value. QL At the beginning and end of 535, the operation of the magnetic saturation detector in CCM is the same as the operation in DCM.

[0062] Consider that a flux density with a transverse component takes a path of greater distance and therefore higher reluctance than a path without a transverse component. Therefore, before saturation, the magnitude of the flux density with a transverse component will be lower than the flux density without a transverse component. The portion of the core assembly with the lower reluctance path and higher flux density begins to saturate first. Saturation increases reluctance. The growing reluctance shifts the additional increase in flux density to the transverse paths that have not yet saturated, thereby increasing the voltage V T When saturation exists in both paths, the lateral component of the flux density increases at a lower rate, resulting in V T Reduce.

[0063] Figure 8 is a planar model 800 of a magnetic core assembly for a magnetic saturation detector that does not require a bias current in the transverse winding. This model is useful for explaining Figure 6 and Figure 7 The waveform of is useful. One part of the model shows a center column 843 with a gap 857, which is wound with a power winding 813, which is driven by a time-varying current I(t) from a current source 833. The magnetic field from the current in the power winding produces a flux density B in the center column. The second part of the model shows the flux density B LR The lower reluctance path 853. The third part of the model represents the transverse flux density B HR The higher magnetic resistance transverse path 863, the transverse flux density B HR A transverse voltage V may be induced in the transverse winding 828 T 830. The flux density B from the magnetic field in the center column 843 is divided into flux density B LR and B HR If the core material is in its quasi-linear region, the flux density B in the lower reluctance path LRwill be greater than the flux density B in the higher reluctance transverse path HR The portion of the core with a higher flux density will saturate before the portion of the core with a lower flux density. As the lower reluctance path 853 begins to saturate, its reluctance increases, thereby shifting more of the total flux density B to the higher reluctance path 863 and increasing the voltage V on the transverse winding 828. T 830.

[0064] Fig. 9 is a perspective view 900 of another example magnetic core assembly having a transverse winding 928 that does not require a bias current in the transverse winding to detect magnetic saturation. Figure 4 The gap in the center column and the power windings around the center column are not shown in Fig. 9 to avoid obscuring the features of the present invention. Figure 4 Compared with the embodiment of Fig. 9 The embodiment of has no rotational offset between the upper core half 907 and the lower core half 927: the vertical edges of the upper and lower core halves are aligned so that the vertical edges are co-linear and the flat vertical faces are co-planar. Fig. 9 The two half cores are based on Figure 4 The standard RM type shown in is modified by removing material from each core half. Fig. 9 An area 937 is shown in the upper core half 907 where material that forms features in the standard configuration has been removed. These standard features still exist in area 947. The lower core half is identical to the upper core half. The removal of material also removes a degree of symmetry in the geometry of the assembly to introduce a component of the transverse flux density that produces a transverse voltage V across the transverse winding 928 when a voltage is present across the power windings around the center post. T 930. Removing material from a standard core half can be considered a skew feature in the assembly of the magnetic core that allows a magnetic saturation detector to determine the onset of magnetic saturation by monitoring the voltage across the transverse winding in the absence of current in the transverse winding.

[0065] Fig.10 yes Fig. 9 FIG. 1 is an annotated perspective view 1000 of an example magnetic core assembly showing the path of flux density originating from current in a power winding. Fig. 9 The gap in the center column and the power windings around the center column are not shown in Fig.10 to avoid obscuring the features of the present invention.

[0066] Fig.10A flux density vector B is shown with horizontal and vertical components in the vertical side of the structure, despite the absence of transverse currents to introduce transverse magnetic fields into the assembly. The asymmetry in the assembly introduced by removing material from the upper and lower core halves introduces a transverse component in the flux density vector B, similar to Figure 4 The rotational offset shown in the embodiment of Figure 4 In the example configuration of Fig.10 The geometry of the assembly ensures that for any orientation of the transverse winding 928 passing through the opening in the center column, there will be a net magnetic flux density passing through the surface defined by the conductor that is the transverse winding. That is, when the transverse winding has no current, there will be a net magnetic flux density passing through the loop formed by the transverse winding. Changes in the transverse component of the flux density will produce a voltage between the terminals of the transverse winding. Fig.10 The geometry of the example assembly also creates a path of higher magnetic resistance for the transverse component of the flux density relative to the non-transverse component of the flux density. In other words, changes in the transverse component of the flux density induce a non-zero transverse voltage V on the transverse winding. T 930, the non-zero transverse voltage V T 930 can be processed to indicate impending magnetic saturation. The saturation characteristics of the magnetic material of the energy transfer element are determined by the transverse voltage V T A feature is produced in the waveform of 930 that allows detection of magnetic saturation during operation of the power supply.

[0067] Fig.11 is a perspective view 1100 of yet another example magnetic core assembly having a transverse winding 1128 that does not require a bias current in the transverse winding to detect magnetic saturation. Fig.11 An upper core half 1107 and a lower core half 1127 are shown with modifications to the standard EE type geometry. Fig.11 1128, the half cores are separated and the windings are not shown to give better visibility of the features of the geometry. In practice, the upper and lower half cores will be in contact and the center post may include a gap. There are also holes drilled through the center post to form an opening to accommodate the lateral windings 1128.

[0068] Fig.11 In an embodiment of the present invention, a corner is removed from each outer leg of each half core. The two corners that are farthest apart in a top view of the standard half core geometry are removed. The two half cores are assembled in an orientation so that the leg with the full corner mates with the leg with the corner removed.

[0069] Fig.12 yes Fig.11 FIG. 12 is an annotated perspective view 1200 of an example magnetic core assembly showing the path of flux density originating from current in a power winding. Fig.10 middle, Fig.12 A flux density vector B is shown with horizontal and vertical components in the vertical side of the structure, despite the absence of transverse currents to introduce transverse magnetic fields into the assembly. The asymmetry in the assembly introduced by removing material from the upper and lower core halves introduces a transverse component in the flux density vector B, similar to Figure 4 As in the previous embodiments, the lateral component of the flux density produces a lateral V T 1130, the lateral V T 1130 can be processed to detect magnetic saturation. It will be appreciated that variations of the standard EE type, such as the common EI type, can be obtained by Fig.11 The modifications shown are made by removing material from the E piece and the I piece, where the I piece is similar to a plate common to the center and outer legs of each half core.

[0070] Modification of the central column of the standard assembly can introduce a lateral component of the flux density to produce voltages on the lateral windings occupying the openings in the central column. An example of such a modification is shown in Fig.13 , Fig.14 and Fig.15 The modification may be considered a skew feature that allows the magnetic saturation detector to determine the onset of magnetic saturation by monitoring the voltage across the transverse winding in the absence of current in the transverse winding.

[0071] Fig.13 is an annotated perspective view 1300 of a portion of a magnetic core assembly emphasizing the center post, showing the path of flux density originating from current in the power windings. Fig.13 Also included is a diagram illustrating the relationship between a Cartesian coordinate system using X, Y, Z coordinates and a cylindrical coordinate system using r, θ, Z coordinates. A cylindrical coordinate system can be more useful than a Cartesian coordinate system to describe Fig.13 The salient features of the configuration shown in .

[0072] Fig.13 The central column of the structure in has a rectangular cross-section that is rotated 180 degrees from the lower plate to the upper plate of the structure. Such a structure will have a spiral reluctance path in the central section. The transverse winding 1328 passes through an aperture - a hole through the center of the column parallel to the Z axis - to generate a transverse voltage V between the ends of the winding. T 1130. Coils of input power windings and output power windings, which may form a transformer or energy transfer element, may be wrapped around a central column.

[0073] Fig.13 An example flux density vector is shown that may be caused by the excitation of a winding around a central post. The flux density vector may form a Fig.13The closed path of the other parts not shown in the figure - passing from the end of the top plate to the end of the bottom plate and back through the center column.

[0074] Fig.13 The embodiment of FIG. 1 shows two flux density vectors in the central column. The linear flux density vector B L 1339 adopts a vertical path, which is the shortest distance and lowest magnetic resistance path between the bottom plate and the top plate. Spiral flux density vector B H 1349 has a component in the θ direction and a component in the Z direction because it follows the ratio B between the bottom plate and the top plate. L The path of 1339 has a greater magnetic resistance.

[0075] Expected linear flux density vector B L 1339 has a spiral flux density vector B H 1349 is a larger value because the magnetic resistance of the spiral path is greater than that of the linear path.

[0076] The change in the magnitude of the θ component of the spiral flux density vector in the central column produces a transverse voltage V at the end of the transverse winding 1328 passing through the opening in the central column. T 1330. Linear flux density vector B L 1339 Variation of the lateral voltage V T 1330 does not make a significant contribution because the linear flux density vector B L 1339 is parallel to the transverse winding 1328 in the center column. Spiral flux density vector B H 1349 changes in voltage V T Contributes because it wraps around the transverse winding 1328.

[0077] Transverse voltage V T 1330 may indicate magnetic saturation in the center column. For increasing flux in the center column, the material in the lower reluctance linear path saturates before the material in the spiral path. When saturation causes the reluctance of the linear path to increase, the flux density along the spiral path increases, generating a transverse voltage V T 1330 increases. When the spiral path is saturated, the lateral voltage V T 1330 decreases, thus generating a lateral voltage V T 1330 In the reversal of the slope, the lateral voltage V T 1330 can be interpreted to detect magnetic saturation.

[0078] In a practical structure, the central column will have approximately twice the cross-sectional area of ​​the top and bottom plates so that the flux density through the structure is nearly the same. Fig.14 yes Fig.13A variation of the structure in which the central column has a square cross-section with approximately twice the cross-sectional area of ​​each plate. The flux density vectors B in the top and bottom plates are summed in the central column to form a spiral flux density vector B H 1449 and linear flux density vector B L 1439. Spiral Flux Density Vector B H The change of the transverse component of 1449 generates a transverse voltage V at the end of the transverse winding 1428 T 1430, the lateral voltage V T 1430 can be processed and interpreted to detect magnetic saturation.

[0079] Fig.15 is an annotated perspective view 1500 of a portion of yet another magnetic core assembly emphasizing the center post, showing the path of flux density originating from current in a power winding. Fig.15 The structure illustrated in has a cylindrical central post with grooves defining a spiral reluctance path. The cylindrical central post with grooves may be a preferred feature in an assembly for a magnetic saturation detector that does not require bias current in the transverse windings.

[0080] The flux density vectors B in the top and bottom plates are summed in the central column to form a spiral flux density vector B H 1549 and linear flux density vector B L 1539. Spiral Flux Density Vector B H The change of the transverse component of 1549 generates a transverse voltage V at the end of the transverse winding 1528 T 1530, the lateral voltage V T 1530 can be processed and interpreted to detect magnetic saturation. The spiral path need not be as Fig.15 Partial rotation of the spiral path around the central column can be sufficient to generate a lateral voltage V T 1530 to detect magnetic saturation.

[0081] Embodiments of the present disclosure include a configuration of a magnetic core for an energy transfer element, the configuration including features for a magnetic saturation detector, wherein the magnetic energy transfer element includes at least one transverse winding and at least one power winding. Current in the power winding generates a magnetic flux density in the assembly. The geometry of the assembly of the magnetic core of the energy transfer element provides a path of lower magnetic resistance for a principal component of the flux density, and provides a path of higher magnetic resistance for a transverse component of the flux density that is substantially perpendicular to the principal component of the flux density. The saturation detector circuit senses a voltage between the terminals of the transverse winding to indicate a magnetic saturation condition at an extreme value of a time-varying voltage on the transverse winding. The transverse component of the flux density generates a voltage between the terminals of the transverse winding without requiring a bias current in the transverse winding. In other words, the configuration of the magnetic core can introduce a transverse component of the flux density in the absence of a current in the transverse winding, so that the voltage on the transverse winding can indicate a magnetic saturation condition.

[0082] The above description of the illustrated embodiments of the present invention, including the content described in the summary, is not intended to be exhaustive or to limit the exact form disclosed. Although specific embodiments and embodiments for the present invention are described herein for illustrative purposes, various equivalent modifications are possible without departing from the broader spirit and scope of the present invention. In fact, it should be understood that providing specific example voltages, currents, frequencies, power range values, times, etc. is for the purpose of explanation, and other values ​​may also be adopted in other embodiments and embodiments according to the teachings of the present invention.

[0083] Although the invention is defined in the claims, it will be appreciated that the invention may alternatively be defined according to the following embodiments:

[0084] Embodiment 1: A magnetic core assembly comprises: a core assembly, the core assembly comprising a lower core member, the lower core member having a central section, and an upper core member, the upper core member having a central section, the central section of the upper core member being aligned with the central section of the lower core member so as to form a central column of the core assembly; and a power winding, the power winding being wound around the central column, wherein when current is passed through the power winding, a power flux density vector is generated, wherein the power flux density vector has a transverse component and a non-transverse component, and wherein the transverse component has a higher magnetic resistance than the non-transverse component.

[0085] Embodiment 2: The magnetic core assembly of Embodiment 1, wherein the lower core piece comprises a lower core member, and the upper core piece comprises an upper core member.

[0086] Embodiment 3: The magnetic core assembly of Embodiment 2, wherein each core member has a reference mark, the reference mark being rotationally offset within the core assembly, and the rotational offset introducing the transverse component to the power flux density vector.

[0087] Embodiment 4: The magnetic core assembly of Embodiment 2, wherein the lower core member and the upper core member each include a skew feature and a reference mark.

[0088] Embodiment 5: The magnetic core assembly of Embodiment 4, wherein for each core member, the skew features are positioned at a core member perimeter and the reference marks are aligned within the core assembly.

[0089] Embodiment 6: The magnetic core assembly of Embodiment 1, wherein at least one of the lower core member and the upper core member has a skew feature, and wherein the skew feature introduces the transverse component to the power flux density vector.

[0090] Embodiment 7: The magnetic core assembly of embodiment 6, wherein the skew feature is a truncated corner.

[0091] Embodiment 8: The magnetic core assembly of Embodiment 6, wherein the center post comprises the skew feature.

[0092] Embodiment 9: The magnetic core assembly of Embodiment 8, wherein the skew feature comprises a helix.

[0093] Embodiment 10: The magnetic core assembly of Embodiment 8, wherein the skew feature comprises a groove on a surface of the center post.

[0094] Embodiment 11: A magnetic saturation detector, comprising a magnetic core assembly according to Embodiment 1, the magnetic saturation detector further comprising: a transverse winding, perpendicular to the power winding, wherein a transverse component from the magnetic core assembly generates a transverse voltage waveform on the transverse winding; and a voltage detection circuit, configured to receive the transverse voltage waveform and detect a change in the sign of the slope of the transverse voltage waveform, wherein the change in the sign of the slope indicates magnetic saturation.

[0095] Embodiment 12: The magnetic saturation detector of Embodiment 11, wherein the central post has an opening and the transverse winding is positioned within the opening.

[0096] Embodiment 13: A magnetic saturation detector according to embodiment 12, wherein each of the lower core member and the upper core member each includes a core member having a reference mark, wherein the reference mark is rotationally offset within the core assembly, and wherein the rotational offset introduces a transverse component to the power flux density vector.

[0097] Embodiment 14: A magnetic saturation detector according to embodiment 12, wherein the lower core member and the upper core member each include a core member having a skew feature and a reference mark, wherein the reference mark is aligned within the core assembly and the skew feature introduces a lateral component to the power flux density vector.

[0098] Embodiment 15: The magnetic saturation detector of Embodiment 14, wherein the skew feature is positioned at the central post and is selected from the group consisting of a helical portion and a surface groove.

[0099] Embodiment 16: The magnetic saturation detector of Embodiment 14, wherein for each core member, the skew features are positioned at the perimeter of the core member.

[0100] Embodiment 17: The magnetic saturation detector of Embodiment 16, wherein the skew feature is a truncated corner.

[0101] Embodiment 18: A power supply, comprising a magnetic saturation detector according to embodiment 12, the power supply comprising: a controller with a reference output, coupled to the magnetic core component and configured to sense an output sensing signal, compare the output sensing signal with a reference value, and generate a switching signal; and a controller with a reference input, coupled to the magnetic core component and configured to generate a drive signal.

Claims

1. A magnetic core assembly, comprising: A core component, the core component comprising a lower core having a central section, and an upper core having a central section, the central section of the upper core being aligned with the central section of the lower core so as to form a central column of the core assembly; and a power winding wound around the central column, wherein when current is passed through the power winding, a power flux density vector is generated, wherein the power flux-density vector has a transverse component and a non-transverse component, and The transverse component has a higher magnetic resistance than the non-transverse component. 2 . The magnetic core assembly of claim 1 , wherein the lower core piece comprises a lower core member, and the upper core piece comprises an upper core member.

3. The magnetic core assembly of claim 2, wherein each core member has a reference mark, the reference mark being rotationally offset within the core assembly, and the rotational offset introducing the transverse component to the power flux density vector. 4 . The magnetic core assembly of claim 2 , wherein the lower core member and the upper core member each include a skew feature and a reference mark.

5. The magnetic core assembly of claim 4, wherein for each core member, the skew features are positioned at a core member perimeter and the reference marks are aligned within the core assembly.

6. The magnetic core assembly of claim 2, wherein at least one of the lower core member and the upper core member has a skew feature, and wherein the skew feature introduces the lateral component to the power flux density vector. The magnetic core assembly of claim 6 , wherein the skew feature is a truncated corner. The magnetic core assembly of claim 6 , wherein the center post includes the skew feature.

9. The magnetic core assembly of claim 8, wherein the skew feature comprises a helical portion.

10. The magnetic core assembly of claim 8, wherein the skew feature comprises a groove on a surface of the center post.

11. A magnetic saturation detector, comprising the magnetic core assembly according to claim 1, and further comprising: Transverse windings, perpendicular to the power windings, wherein a transverse component from the magnetic core assembly generates a transverse voltage waveform on the transverse winding; as well as a voltage detection circuit configured to receive the transverse voltage waveform and detect a change in a sign of a slope of the transverse voltage waveform, A change in the sign of the slope indicates magnetic saturation.

12. The magnetic saturation detector of claim 11, wherein the central column has an opening and the transverse winding is positioned within the opening.

13. The magnetic saturation detector according to claim 12, wherein the lower core comprises a lower core member, and the upper core comprises an upper core member, wherein each of the lower core member and the upper core member each comprises a core member having a reference numeral, wherein the reference marker is rotationally offset within the core assembly, and The rotational offset introduces a transverse component to the power flux density vector.

14. The magnetic saturation detector according to claim 12, wherein the lower core comprises a lower core member, and the upper core comprises an upper core member, The lower core member and the upper core member each include a core member having a skew feature and a reference mark, wherein the reference mark is aligned within the core assembly and the skew feature introduces a lateral component to the power flux density vector.

15. The magnetic saturation detector of claim 14, wherein the skew feature is located at the central post and is selected from the group consisting of a helical portion and a surface groove.

16. The magnetic saturation detector of claim 14, wherein for each core member, the skew features are positioned at a perimeter of the core member.

17. The magnetic saturation detector of claim 16, wherein the skew feature is a truncated corner.

18. A power supply, comprising the magnetic saturation detector according to claim 12, the power supply comprising: a reference output controller coupled to the magnetic core assembly and configured to sense an output sense signal, compare the output sense signal with a reference value, and generate a switch signal; as well as A controller, referenced to an input, is coupled to the magnetic core assembly and is configured to generate a drive signal.

Images