Multilayer transformer structure comprising a plurality of rectifying elements

Abstract

A power conversion circuit has a multi-layer transformer and a plurality of rectification transistors coupled to secondary winding of the multi-layer transformer. The multi-layer transformer is formed as a plurality of layers within a PCB stack, where primary winding conductors and secondary winding conductors are vertically aligned and stacked. The secondary winding conductors are configured to have one or more secondary winding arms that provide areas to which the plurality of rectification transistors are physically connected. The primary winding conductors are configured to have primary winding arms. The footprint of each primary winding conductor is configured to substantially overlap the entire footprint of each secondary winding conductor. In this way, the entire secondary current flowing through the secondary winding conductors is vertically aligned with the primary winding conductors and thus with the primary current flowing through the secondary winding conductors.

Description

Technical Field

[0001] This invention generally relates to the field of multilayer transformers. More specifically, this invention relates to a multilayer transformer structure comprising multiple rectifier elements. Background Technology

[0002] The growth of major data centers has led to an exponential increase in the power density of power converters. This is primarily due to the rapid advancements in MOSFET performance, enabling extremely high output power in a very small size. To accommodate this development and further improve power density, the transformers in transformer-based designs used in power converters must be further optimized.

[0003] By representing each "coil" in a transformer as a coil-like conductor patterned on a different layer of a PCB, the transformer structure can be integrated as part of a multilayer printed circuit board, with each coil-like conductor corresponding to a winding or turn of the transformer's primary or secondary winding. The coil-like conductors corresponding to the primary winding are interconnected via a first set of vias, and the coil-like conductors corresponding to the secondary winding are interconnected via a second set of vias. The coil-like conductors are located on each layer of the PCB stack so that they are vertically aligned with each other within the stack. The resulting structure is called a multilayer transformer.

[0004] In some applications, the circuit board is configured as a power converter, and the secondary winding is selected to be connected to different voltage rails in the power converter circuit via rectifier transistors, such as MOSFETs. Rectifier transistors are essential for providing DC power to the attached load. In many applications, a large number of rectifier transistors are required to handle the demanding current. The higher the current, the more rectifier transistors are needed. The number of rectifier transistors also depends on several other factors, including the output voltage, MOSFET design and package, and the target application load profile.

[0005] When operating at high frequencies, such as 200 kHz or higher, significant skin and eddy current effects exist associated with the conductor windings in multilayer transformers. In this case, the skin effect is that alternating current (AC) tends to distribute within the conductor, resulting in the current density being maximized near the outer periphery of the conductor forming the winding in any layer of the multilayer transformer, and decreasing the current flow inward from the outer periphery. These effects cause current to concentrate in certain portions of the winding conductor, while less current flows through other portions.

[0006] Typically, these effects are minimized by configuring the power converter circuit to have a primary current flowing in one direction and a secondary current flowing in the opposite direction, as can be seen in a typical transformer configuration. Figure 1A schematic diagram of an exemplary conventional power converter circuit is shown. This diagram outputs four groups of rectifier transistors on the output side of the power converter circuit, each group comprising four individual transistors. Specifically, the power converter circuit includes rectifier transistors T400, T414, T420, T424, T401, T417, T421, and T427 coupled to the secondary winding terminal TRMSA of transformer M300, and rectifier transistors T402, T415, T422, T425, T403, T416, T423, and T426 coupled to the secondary winding terminal TRMSB of transformer M300. Rectifier transistors T400, T414, T420, and T424 are grouped together as a first group and configured in parallel between the secondary winding terminal TRMSA and the high-voltage rail +OUTB. Rectifier transistors T402, T415, T422, and T425 are grouped together as the second group and connected in parallel between the secondary winding terminal TRMSB and the high-voltage rail +OUTB. Rectifier transistors T401, T417, T421, and T427 are grouped together as the third group and connected in parallel between the secondary winding terminal TRMSA and the ground rail. Rectifier transistors T403, T416, T423, and T426 are grouped together as the fourth group and connected in parallel between the secondary winding terminal TRMSB and the ground rail.

[0007] The output side of the power converter also includes capacitors C489, C473, C490, C472, C474, C491, C475, C463-470, C476-478, resistors R470 and R471, inductor M400, and rectifier transistor drivers N419 and N409. The rectifier transistor drivers N419 and N409 buffer and amplify the drive capability of the drive signal provided to the rectifier transistor from the slave controller (not shown). The output voltage is provided at terminal +OUT.

[0008] Input DC power is provided at terminals +IN and -IN on the input side of the power converter circuit. The input side includes capacitors C1-C9, C12, C13, C48, and C49, inductor M1, transistors T1-T4, and transistor drivers N420 and N421. Transistors T1-T4 can be MOSFETs or other conventional switching devices. Transistor drivers N420 and N421 buffer and amplify the drive capability of the drive signals provided from a controller (not shown) for transistors T1-T4.

[0009] In operation, the power converter circuit receives an input DC voltage. Transistors T1-T4 are pulse-width modulated, causing a quasi-square voltage waveform to be input to the primary winding of transformer M300. The quasi-square voltage waveform alternates between positive and negative voltage pulses and is considered an AC voltage. Different modulation schemes can be applied. In one scheme, transistors T1 and T4 are turned on while transistors T2 and T3 are turned off to drive current in one direction, such as a negative primary current and a positive secondary current, and when driving current in the other direction, such as a positive primary current and a negative secondary current (collectively referred to as AC current), transistors T2 and T3 are turned on while transistors T1 and T4 are turned off. When transistors T1 and T4 are turned on and transistors T2 and T3 are turned off, the primary current flows from the positive rail +PWR through transistor T1, the primary winding of transformer M300, transistor T4, to the negative rail -IN, as shown in primary current path 1. During the same time period, rectifier transistors T400, T4l4, T420, T424, T403, T4l6, T423, and T426 are turned on while rectifier transistors T402, T415, T422, T425, T40l, T417, T421, and T427 are turned off. This causes the secondary current induced at the secondary winding of transformer M300 to flow through rectifier transistors T400, T4l4, T420, and T424, inductor M400, capacitors C463, C464, C465, C466, C467, C468, C469, C470, C476, C477, and C478, and any connected loads, rectifier transistors T403, T416, T423, and T426, and back to the secondary winding, as shown in secondary current path 2.

[0010] When transistors T1 and T4 are off and transistors T2 and T3 are on, the primary current flows from the positive rail +PWR through transistor T3, the primary winding of transformer M300, transistor T2 to the negative rail -IN, as shown in primary current path 3. During this same time period, rectifier transistors T400, T4l4, T420, T424, T403, T4l6, T423, and T426 are off, while rectifier transistors T402, T4l5, T422, T425, T401, T417, T42l, and T427 are on. This causes the secondary current induced at the secondary winding of transformer M300 to flow through rectifier transistors T401, T417, T421, and T427, capacitors C463, C464, C465, C466, C467, C468, C469, C470, C476, C477, and C478, and any connected loads, inductor M400, rectifier transistors T402, T415, T422, and T425, and back to the secondary winding, as shown in secondary current path 4.

[0011] The physical structure of the power converter circuit is implemented as a multilayer PCB. Capacitors, resistors, and controller chips are mounted to the top and / or bottom sides of the PCB, and the multilayer transformer is implemented as interleaved primary and secondary winding conductor layers in a PCB stack. The PCB includes patterned conductive interconnects and interconnect vias for properly interconnecting the various components and layers. Losses in the multilayer transformer can be further reduced by minimizing the interconnect conductor length between the secondary winding conductors and the rectifier transistors. This problem can be solved by moving the connection between each rectifier transistor and the secondary winding conductor to the winding conductor itself. In particular, the physical positioning of each rectifier transistor is such that the rectifier transistor is aligned on the outer peripheral edge of the secondary winding conductor in the PCB stack. Figure 2 This shows a top view of one of the layers in a conventional PCB that includes the primary winding conductor. Figure 3 This shows a top view of one layer in a conventional PCB that includes the secondary winding conductor. The actual number of layers in a PCB that include the secondary winding conductor and the number of layers that include the primary winding conductor depend on the turns ratio of the multilayer transformer. Figure 2 As shown, the primary winding conductor 2 is circular. The primary winding conductor 2 is discontinuous at break 4, which essentially forms the two ends of the primary winding conductor 2. Each end connects to the other end of another primary winding conductor on another layer of the PCB. The ends of the two primary winding conductors on different layers are interconnected via interconnect vias. For example, one end of the primary winding conductor 2 can be connected to the next higher primary winding conductor in the PCB stack via interconnect via 6, while the other end of the primary winding conductor 2 can be connected to the next lower primary winding conductor in the PCB stack via interconnect via 8.

[0012] like Figure 3 As shown, the secondary winding conductor 12 includes secondary winding conductor arms 14 and 16 extending from a circular base. Similar to the primary winding conductor, the secondary winding conductor 12 is discontinuous at the break, essentially forming the two ends of the secondary winding conductor, which are connected via interconnect vias to other secondary winding conductors on other layers of the PCB stack. The circular base of the secondary winding conductor 12 substantially matches the circular shape of the primary winding conductor 2. In the PCB stack, Figure 2 The primary winding conductor 2 shown is... Figure 3 The secondary winding conductors 12 are aligned and stacked. Figure 3 The dashed arc 18 shown represents Figure 2 The relative positions of the outer peripheral edges of the primary winding conductor 2. The secondary winding conductor arms 14 and 16 expand the physical area where multiple rectifier transistors can be connected, extending to the secondary winding conductors. The relative physical positions of the rectifier transistors are selected in... Figure 3 The output is an overlay box. Overlayed on... Figure 3The rectifier transistors T422, T425, T414, T420, T416, T423, T427, and T421 are mounted on one side of the PCB, such as the top side, and the rectifier transistors T400, T424, T402, T415, T401, T417, T403, and T426 are mounted on the top side of the PCB. Figure 1 The remaining portion is mounted to the other side of the PCB, such as the bottom side. Superimposed on... Figure 3 Each rectifier transistor T422, T425, T414, T420, T416, T423, T427, and T421 is vertically aligned with a corresponding one of the other rectifier transistors T400, T424, T402, T415, T401, T417, T403, and T426. Rectifier transistors T422, T425, T414, and T420 are connected to inductor M400, and rectifier transistors T416, T423, T427, and T421 are grounded. Similarly, rectifier transistors T400, T414, T402, and T415 (… Figure 1 ) is connected to inductor M400, and rectifier transistors T401, T417, T403, T426 ( Figure 1 Grounding.

[0013] like Figure 3 As shown, each rectifier transistor is physically positioned relative to the secondary winding conductor such that a first portion of the rectifier transistor (e.g., portion A of rectifier transistors T416 and T423) overlaps the outer periphery of the secondary winding conductor, and a second portion (e.g., portion B) overlaps adjacent conductor elements (e.g., ground nodes). The location of each rectifier transistor connected to the secondary winding conductor is outside the coverage area of ​​the primary winding conductor, as shown... Figure 3 As shown, rectifier transistors T422, T425, T414, T420, T416, T423, T427, and T421 are located to the right of the outer peripheral edge of the primary winding conductor 2, for example, the right side of the dashed arc 18. In this configuration, the rectifier transistors are considered to be located outside the primary current path within the primary winding conductor. In other words, the rectifier transistors are not aligned on the primary current path that serves as the AC current loop.

[0014] Depending on the states of primary-side transistors T1-T4, the primary current flows clockwise (e.g., ...). Figure 2 (As shown) the current flows, either directly or counterclockwise around the primary winding conductor. The width of the primary winding conductor is a measure of the distance between its inner and outer edges. The primary current flow is distributed across the width of the primary winding conductor but is concentrated according to the magnetic field lines formed by the flow path of the secondary current through the secondary winding conductor. To minimize proximity effects and eddy current losses, it is desirable to vertically align the secondary current path with the primary current path. However, since the rectifier transistor is physically located at the edge of the secondary winding conductor arm, as shown... Figure 3 As shown, the actual secondary current path, such as secondary current path 20, extends into the secondary winding conductor arm, and is thus conducted through rectifier transistors, such as rectifier transistors T421, T423, and T427. The distance between this extended secondary current path and the primary current path results in significant losses. Figure 3 In the exemplary configuration shown, the portion of the secondary winding conductor outside (to the right) of the primary winding conductor accounts for approximately 50% of the total secondary current path. Additionally, the magnetic field lines generated by the secondary current flow in the secondary winding conductor arm cause concentrated primary current flow and a proximity effect at the outer periphery of the primary winding conductor. Summary of the Invention

[0015] This embodiment relates to a power conversion circuit having a multilayer transformer and a plurality of rectifier transistors coupled to the secondary windings of the multilayer transformer. The multilayer transformer is formed as multiple layers within a PCB stack, wherein the primary winding conductors and secondary winding conductors forming the multilayer transformer are vertically aligned and stacked. The secondary winding conductors are configured to have one or more secondary winding arms, providing areas for physical connection of the plurality of rectifier transistors. The primary winding conductors are configured to have primary winding arms. The coverage area of ​​each primary winding conductor is configured to substantially overlap the entire coverage area of ​​each secondary winding conductor. Thus, the entire secondary current flowing through the secondary winding conductor is vertically aligned with and therefore with the primary current flowing through the primary winding conductor. Vertical alignment of the secondary and primary currents within the multilayer transformer maximizes the proximity of the secondary and primary currents and reduces proximity effects and associated eddy current losses.

[0016] According to one aspect of this disclosure, a power conversion circuit is provided, comprising: a. a printed circuit board stack including a plurality of layers stacked together; b. a multilayer transformer formed within the printed circuit board stack, wherein the multilayer transformer includes a plurality of primary winding conductors and a plurality of secondary winding conductors, each primary winding conductor being formed as a corresponding layer of the printed circuit board stack, and each secondary winding conductor being formed as a corresponding one in the printed circuit board stack, further wherein the coverage area of ​​each primary winding conductor is configured to substantially vertically overlap the entire coverage area of ​​each secondary winding conductor; and c. a plurality of rectifier transistors, each rectifier transistor being connected to one of the plurality of secondary winding conductors.

[0017] The plurality of rectifier transistors are physically positioned relative to the plurality of primary winding conductors to be vertically aligned with the AC current path through the multilayer transformer.

[0018] The AC current path includes the primary current path through each primary winding conductor.

[0019] The structure of the multilayer transformer enables the injection and removal of DC current into and out of the transformer block, which is defined as a vertical space formed by a plurality of vertically aligned and stacked primary winding conductors and a plurality of secondary winding conductors.

[0020] Each of the plurality of rectifier transistors is vertically aligned with the coverage area of ​​each primary winding conductor.

[0021] Each secondary winding conductor includes multiple secondary winding conductor arms.

[0022] Each secondary winding conductor includes a primary winding conductor arm and a secondary winding conductor arm separated by a discontinuity break in the secondary winding conductor.

[0023] Each layer in the printed circuit board stack, including the secondary winding conductors connected to the rectifier transistor, also includes a DC node conductor, further wherein the DC node conductor includes a DC node protrusion extending into a discontinuous break between the first and second secondary winding conductor arms.

[0024] The DC node protrusion is vertically aligned with each primary winding conductor.

[0025] One or more connection points on each rectifier transistor are connected to one of the secondary winding conductors, and one or more other connection points on each rectifier transistor are connected to a DC node conductor on the same layer as the connected secondary winding conductor.

[0026] One or more other connection points on each rectifier transistor, connected to the DC node conductor on the same layer as the connected secondary winding conductor, are connected to the DC node protrusion.

[0027] Each rectifier transistor physically spans the discontinuity between the DC node protrusion and one of the primary winding conductor arms and the secondary winding conductor arm.

[0028] According to another aspect of this disclosure, a power conversion circuit is provided, comprising: a. a printed circuit board stack including a plurality of layers stacked together; b. a multilayer transformer formed within the printed circuit board stack, wherein the multilayer transformer includes a plurality of primary winding conductors and a plurality of secondary winding conductors vertically aligned with the plurality of primary winding conductors; and c. a plurality of rectifier transistors, each rectifier transistor being connected to one of the plurality of secondary winding conductors, wherein the multilayer transformer is configured to allow DC current to be injected into and removed from a transformer block, the transformer block being defined as a vertical space formed by a plurality of vertically aligned and stacked primary winding conductors and a plurality of secondary winding conductors. Attached Figure Description

[0029] Several exemplary embodiments are described with reference to the accompanying drawings, in which similar components are given similar reference numerals. These exemplary embodiments are intended to illustrate, not limit, the invention. The drawings include the following figures:

[0030] Figure 1 A schematic diagram of an exemplary conventional power converter circuit is shown.

[0031] Figure 2 This shows a top view of one of the layers in a conventional PCB that includes the primary winding conductor.

[0032] Figure 3 This shows a top view of one of the layers in a conventional PCB that includes secondary winding conductors.

[0033] Figure 4 A schematic diagram of an exemplary power converter circuit according to some embodiments is shown.

[0034] Figure 5 A top view is shown of one layer of a PCB stack including primary winding conductors according to some embodiments.

[0035] Figure 6 A top view is shown of one layer of a PCB stack including secondary winding conductors according to some embodiments.

[0036] Figure 7 Showing from Figure 6 The PCB stack layer includes secondary winding conductors 112 of a first set of rectifier transistors mounted to the top side layer of the PCB stack.

[0037] Figure 8 Showing from Figure 6 The PCB stack layer includes secondary winding conductors 112 of a second set of rectifier transistors superimposed on the bottom side layer of the PCB stack.

[0038] Figure 9 Showing from Figure 5 The PCB stack layer includes a primary winding conductor 100 on which rectifier transistors are stacked.

[0039] Figure 10 Showing from Figure 7 The PCB stack-up layer shows the cross-section line A-A'.

[0040] Figure 11 It shows along Figure 10 A cross-sectional view of a portion of the PCB stack along line A-A' shown.

[0041] Figure 12 It shows something similar to Figure 11A cross-sectional view of a portion of the PCB stack, which also includes embedded die-level rectifier transistors.

[0042] Figure 13 The graph shown represents the AC resistance versus frequency.

[0043] Figure 14 A graph showing efficiency versus power is shown. Detailed Implementation

[0044] Embodiments of this application relate to a multilayer transformer structure. Those skilled in the art will recognize that the following detailed description of the multilayer transformer structure is merely illustrative and not intended to be limiting. Other embodiments of the multilayer transformer structure will readily conceive of those skilled in the art upon receiving this disclosure.

[0045] Embodiments of the multilayer transformer structure shown in the accompanying drawings will now be described in detail. The same reference numerals will be used throughout the drawings and in the following detailed description to refer to the same or similar components. For clarity, not all conventional features of the embodiments described herein are shown or described. It should be understood, of course, that in developing any such practical embodiment, many implementation-specific decisions must be made to achieve the developer's specific objectives, such as compliance with application and business-related constraints, and these specific objectives will vary for each embodiment and for each developer. Furthermore, it should be understood that such development work can be complex and time-consuming, but will still be routine engineering work for those skilled in the art who benefit from this disclosure.

[0046] The power converter circuit of this application includes an enhanced multilayer transformer structure. Although the schematic layout of the entire power converter circuit is similar to that of similar conventional power converter circuits, the physical structure layout on the PCB is different, resulting in significant enhancements and performance improvements. In particular, the structural configuration of the primary and secondary winding conductors of the multilayer transformer is changed, as are the positions of the rectifier transistors relative to the primary and secondary winding conductors.

[0047] Figure 4 A schematic diagram of an exemplary power converter circuit according to some embodiments is shown. To distinguish the physical structure when comparing similar illustrative layouts, the exemplary power converter circuit is schematically configured to... Figure 1 The power converter circuit shown is similar, as will be explained in more detail below. It should be understood that the enhanced multilayer transformer structure and corresponding rectifier transistors can be alternatively applied to [other applications]. Figure 4 Other power converter circuits besides the exemplary schematic diagram shown. Besides differing in structure from comparable conventional schematic power converter circuits, Figure 4The power converter circuit schematically illustrated includes additional conductor elements, such as copper clips, which can be used to interconnect the secondary winding conductors to the inductor. This additional conductor element... Figure 4 The component shown is TEB1.

[0048] Figure 4 The power converter circuit includes rectifier transistors T400, T414, T420, T424, T401, T417, T421, and T427, configured as two groups of four transistors. Transformer M300' is an improved multilayer transformer, structurally similar to the multilayer transformer M300 (…). Figure 1The rectifier transistors T400, T414, T420, T424, T401, T417, T421, and T427 are coupled to the secondary winding terminal TRMSA of transformer M300'. The power converter circuit also includes rectifier transistors T402, T415, T422, T425, T403, T416, T423, and T426, configured as two groups of four transistors. Rectifier transistors T402, T415, T422, T425, T403, T416, T423, and T426 are coupled to the secondary winding terminal TRMSB of transformer M300'. Rectifier transistors T400, T414, T420, and T424 are grouped together as the first group and connected in parallel between the secondary winding terminal TRMSA and the high-voltage rail +OUT_C. Rectifier transistors T402, T415, T422, and T425 are grouped together as a second group and connected in parallel between the secondary winding terminal TRMSB and the high-voltage rail +OUT_C. Rectifier transistors T401, T417, T421, and T427 are grouped together as a third group and connected in parallel between the secondary winding terminal TRMSA and the ground rail. Rectifier transistors T403, T416, T423, and T426 are grouped together as a fourth group and connected in parallel between the secondary winding terminal TRMSB and the ground rail. The output side of the power converter also includes capacitors C489, C473, C490, C472, C474, C491, C475, C463-470, and C476-478, resistors R470 and R471, inductor M400, and rectifier transistor drivers N419 and N409. Rectifier transistor drivers N419 and N409 buffer and amplify the drive capability of the drive signal provided from the controller (not shown) for the rectifier transistors. The output voltage is provided at terminal +OUT. Input DC power is supplied at terminals +IN and -IN on the input side of the power converter circuit. The input side includes capacitors C1-C9, C12, C13, C48, and C49, inductor M1, transistors T1-T4, and transistor drivers N420 and N421. Transistors T1-T4 can be MOSFETs or other conventional switching devices. Transistor drivers N420 and N421 buffer and amplify the drive capability of the drive signal provided from the controller (not shown) for transistors T1-T4.

[0049] The AC current has two different polarities, which requires rectification using a rectifier transistor. Current paths 103 and 107 correspond to one phase (polarity, direction), and current paths 101 and 105 correspond to the other phase. The output of the rectifier transistor (at DC node 118) is a rectified pulse voltage waveform (which is a unipolar AC voltage), which is input to inductor M400. Although the voltage output from the rectifier transistor is a pulsed AC voltage, the current output from the rectifier transistor is a DC current. Inductor M400 and capacitors C463-C470 and C476-C478 form an LC filter, which averages the pulse waveform to a substantially constant DC voltage value.

[0050] In operation, the power converter circuit receives an input DC voltage. Transistors T1-T4 are pulse-width modulated, causing a quasi-square voltage waveform to be input to the primary winding of transformer M300. The quasi-square voltage waveform alternates between positive and negative voltage pulses and is considered an AC voltage. Different modulation schemes can be applied. In one scheme, transistors T1 and T4 are turned on while transistors T2 and T3 are turned off to drive current in one direction, such as a negative primary current and a positive secondary current, and when driving current in the other direction, such as a positive primary current and a negative secondary current (collectively referred to as AC current), transistors T2 and T3 are turned on while transistors T1 and T4 are turned off. When transistors T1 and T4 are turned on and transistors T2 and T3 are turned off, the primary current flows from the positive rail +PWR through transistor T1, the primary winding of transformer M300', transistor T4 to the negative rail -IN, as shown in primary current path 101. During the same time period, rectifier transistors T400, T414, T420, T424, T403, T416, T423, and T426 are turned on, while rectifier transistors T402, T415, T422, T425, T401, T417, T421, and T427 are turned off. This causes a secondary current induced at the secondary winding of transformer M300' to flow through rectifier transistor T400. 0, T4l4, T420, T424, inductor M400, capacitors C463, C464, C465, C466, C467, C468, C469, C470, C476, C477, C478 and any connected load, rectifier transistors T403, T416, T423, T426 and back to the secondary winding, as shown in secondary current path 105.

[0051] When transistors T1 and T4 are off and transistors T2 and T3 are on, the primary current flows from the positive rail +PWR through transistor T3, the primary winding of transformer M300', transistor T2, to the negative rail -IN, as shown in primary current path 103. During the same time period, rectifier transistors T400, T414, T420, T424, T403, T416, T423, and T426 are off, while rectifier transistors T402, T415, T422, T425, T401, T417, T421, and T427 are on. This causes a secondary current induced at the secondary winding of transformer M300' to flow through rectifier transistor T400. 1. T417, T421, T427, capacitors C463, C464, C465, C466, C467, C468, C469, C470, C476, C477, C478 and any connected loads, inductor M400, rectifier transistors T402, T415, T422, T425 and back to the secondary winding, as shown in secondary current path 107. Although current paths 101, 103, 105, 107 are schematically similar to Figure 1 The current paths in the transformer M300 are 1, 2, 3, and 4, but they are not the same. Instead, due to the modified shapes of the primary and secondary winding conductors and the different relative positions of the rectifier transistors, the current paths through the multilayer transformer M300' are different, as explained in more detail below.

[0052] Although schematically similar to Figure 1 The multilayer transformer M300 has different physical shapes for its primary and secondary winding conductors, and each rectifier transistor T400, T414, T420, T424, T401, T417, T421, T427, T402, T415, T422, T425, T403, T416, T423, and T426 has a different physical position relative to the primary and secondary winding conductors.

[0053] The physical structure of the power converter circuit is implemented as a multilayer PCB. In some embodiments, capacitors, resistors, and controller chips are mounted to the top and / or bottom sides of the PCB, and the multilayer transformer is implemented as interleaved primary and secondary winding conductor layers in a PCB stack. The PCB includes patterned conductive interconnects and interconnect vias for appropriately interconnecting various components and layers. The actual number of layers including secondary winding conductors and the number of layers including primary winding conductors in the PCB depend on the turns ratio of the multilayer transformer.

[0054] Figure 5A top view is shown of one layer within a PCB stack including a primary winding conductor according to some embodiments. The primary winding conductor 100 includes a primary winding conductor arm 102 extending from a generally circular base portion. The primary winding conductor 100 is discontinuous at a break 104, which... Figure 5 Primary winding current path endpoints are formed in specific layers of the primary winding conductors shown. These endpoints can interconnect to other adjacent primary winding conductors in other layers of the PCB stack. For example, interconnect via 106 can be used to interconnect primary winding conductor 100 to the next higher-positioned primary winding conductor in the PCB stack, and interconnect via 108 can be used to interconnect primary winding conductor 100 to the next lower-positioned primary winding conductor in the PCB stack. Primary winding conductor 100 includes other discontinuities through which other interconnect vias can be formed to provide interconnection to secondary winding conductors that intersect with the primary winding conductors in the PCB stack. Similar discontinuities and interconnect vias can also be formed to provide interconnection to rectifier transistors connected to the secondary winding conductors. For example, interconnect vias 110, 122, 124, and 126 are formed in discontinuities of primary winding conductor 100. Such interconnect vias are disconnected from the primary winding conductor.

[0055] Figure 6 A top view is shown of one layer of a PCB stack including secondary winding conductors according to some embodiments. The secondary winding conductor 112 includes a first secondary winding conductor arm 114 and a second secondary winding conductor arm 116 extending from a circular base portion. The secondary conductor arms 114, 116 are separated by a DC node protrusion 120, which is an extension of a DC node 118. The DC node 118 is a conductor formed as part of the PCB stack layer. Each secondary winding conductor arm 114, 116... Figure 6 Secondary winding current path endpoints are formed in specific layers of the secondary winding conductors shown. These endpoints can be interconnected to other adjacently positioned secondary winding conductors in other layers of the PCB stack. For example, interconnect via 110 can be used to interconnect secondary winding conductor arm 114 to the next higher positioned secondary winding conductor in the PCB stack, and interconnect via 126 can be used to interconnect secondary winding conductor arm 116 to the next lower positioned secondary winding conductor in the PCB stack. Interconnect vias 110 and 126 can also be formed to provide interconnections with rectifier transistors connected to the secondary winding conductors. Interconnect vias can be coupled to DC node protrusions to provide interconnections between rectifier transistors and DC nodes. For example, interconnect vias 122 and 124 are coupled to DC node protrusion 120.

[0056] Figure 7 Showing from Figure 6The PCB stack layer includes secondary winding conductors 112 of a first set of rectifier transistors mounted to the top side layer of the PCB stack. Figure 8 Showing from Figure 6 The PCB stack includes a secondary winding conductor 112 of a second set of rectifier transistors mounted to the bottom layer of the PCB stack. In some embodiments, the first set of rectifier transistors is mounted to the top layer of the PCB stack, while the second set of rectifier transistors is mounted to the bottom layer of the PCB stack, such as... Figure 11 As shown. Figure 11 It shows along Figure 10 The image shows a cross-sectional view of a portion of the PCB stack along line A-A'. In an alternative embodiment, some rectifier transistors may be embedded within the PCB stack, such as... Figure 12 An exemplary cross-sectional view of a portion of the PCB stack shown. Figure 12 The alternative embodiments shown are with Figure 11 The view shown is similar to the view shown, but one or more other rectifier transistors or additional rectifier transistors are embedded within the PCB stack and connected to the corresponding secondary winding conductors.

[0057] Refer again Figure 7 and 8The first set of rectifier transistors may include first set of rectifier transistors T400, T414, T420, and T424 connected to the secondary winding terminal TRMSA and the high-voltage rail +OUT_C, and a second set of rectifier transistors T402, T415, T422, and T425 connected between the secondary winding terminal TRMSB and the high-voltage rail +OUT_C. The first set of rectifier transistors is positioned across a break between a DC node protrusion and one of the secondary winding conductor arms, such that a first portion of each rectifier transistor overlaps one of the secondary winding conductor arms and a second portion of each rectifier transistor overlaps the DC node protrusion. In an exemplary configuration, each of the first set of rectifier transistors is electrically connected to the top layer of a PCB stack including the secondary winding conductor. This top layer may be the top outer layer of the PCB stack, or it may be an inner layer of the PCB stack. The first set of rectifier transistors may include rectifier transistors T424, T400, T414, T420, T402, T415, T422, and T425. Rectifier transistors T402, T422, T425, and T415 respectively cross the break between the secondary winding conductor arm 116 and the DC node protrusion 120, and are connected to the secondary winding conductor arm 116 and the DC node protrusion 120 through corresponding interconnects and / or interconnect vias. For example, rectifier transistor T425 is connected to the secondary winding conductor arm 116 through a secondary interconnect via 126 and to the DC node protrusion 120 through a DC node interconnect via 124. Rectifier transistors T424, T400, T414, and T420 respectively cross the break between the secondary winding conductor arm 114 and the DC node protrusion 120, and are connected to the secondary winding conductor arm 114 and the DC node protrusion 120 through corresponding interconnects and / or interconnect vias. For example, rectifier transistor T414 is connected to the secondary winding conductor arm 114 through a secondary interconnect via 110 and to the DC node protrusion 120 through a DC node interconnect via 122.

[0058] In some embodiments, a second set of rectifier transistors is mounted to the bottom layer of a PCB stack, and each is electrically connected to the bottom layer of the PCB stack that includes the secondary winding conductor. The second set of rectifier transistors may include a third set of rectifier transistors T401, T417, T421, and T427 connected to the secondary winding terminal TRMSA and the ground rail, and a fourth set of rectifier transistors T403, T416, T423, and T426 connected between the secondary winding terminal TRMSB and the ground rail. The second set of rectifier transistors is positioned to cross a break between a DC node protrusion and one of the secondary winding conductor arms, such that a first portion of each rectifier transistor overlaps one of the secondary winding conductor arms, and a second portion of each rectifier transistor overlaps the DC node protrusion. In an exemplary configuration, each of the second set of rectifier transistors is electrically connected to the bottom layer of the PCB stack that includes the secondary winding conductor. This bottom layer may be the bottom outer layer of the PCB stack, or it may be an inner layer of the PCB stack. The second group of rectifier transistors may include rectifier transistors T401, T421, T427, T417, T426, T403, T416, and T423. Rectifier transistors T426, T403, T416, and T423 respectively cross the break between the secondary winding conductor arm 116 and the DC node protrusion 120, and are connected to the secondary winding conductor arm 116 and the DC node protrusion 120 through corresponding interconnects and / or interconnect vias. Rectifier transistors T401, T421, T427, and T417 respectively cross the break 10 between the secondary winding conductor arm 114 and the DC node protrusion 120, and are connected to the secondary winding conductor arm 114 and the DC node protrusion 120 through corresponding interconnects and / or interconnect vias.

[0059] In some embodiments, superimposed on Figure 8 Each of the rectifier transistors T401, T421, T427, T417, T426, T403, T416, and T423 in the series is associated with other rectifier transistors T422, T425, T414, T420, T402, T415, T422, and T425. Figure 7The corresponding vertical alignment is as follows. For example, rectifier transistor T414 is located on the top side surface of the PCB, while rectifier transistor 427 is located on the bottom side surface of the PCB and aligned with rectifier transistor T414. Typically, each group of parallel-connected rectifier transistors connected to each transformer secondary winding is symmetrically aligned. For example, the first group of rectifier transistors is symmetrically aligned with the third group of rectifier transistors, and the second group of rectifier transistors is symmetrically aligned with the fourth group of rectifier transistors, where the first and second groups are on the same side of the PCB stack, while the third and fourth groups are on the other side of the PCB stack. Rectifier transistors T422, T425, T414, T420, T402, T415, T422, and T425 are connected to the topmost DC node 118 of the PCB stack with secondary winding conductors. In the case where the topmost layer of the PCB stack with secondary winding conductors is also the top outer layer of the PCB stack, the DC node protrusion 120 of the DC node 118 of this layer is connected to the inductor M400 via conductor interconnects, such as conductive clips, which interconnects are... Figure 7 Box 128 and Figure 4 Taking the illustrative TEB1 as an example, the DC current output from rectifier transistors T422, T425, T414, T420, T402, T415, T422, and T425 is input to inductor M400 through conductive clip 128. Although this configuration requires a longer DC current path, compared to... Figure 3 In contrast, the rectifier transistor is connected directly from the secondary winding conductor to the inductor. Figure 7 The configuration provides sensing Figure 9 The secondary current path of the primary current path is explained in detail below. The bottom-side rectifier transistors T401, T421, T427, T417, T426, T403, T416, and T423 are connected to a DC node protrusion 120 on another layer, such as the bottom layer with secondary winding conductors (a different layer from the layer with DC node protrusions connected to inductors using copper clips), where the DC node protrusion is grounded.

[0060] Figure 9 Showing from Figure 5 The PCB stack-up includes a primary winding conductor 100 on which rectifier transistors are stacked. For example... Figure 9 As shown, only the first group of rectifier transistors is marked, but it should be understood that the superimposed rectifier transistors also correspond to the second group of rectifier transistors.

[0061] In the PCB stack, the primary winding conductor 100 and secondary winding conductor 112 in corresponding layers are vertically aligned. The primary winding conductor 100 extends (primary winding conductor arm 102) in a shape more similar to the secondary winding conductor 112 (and secondary winding conductor arms 114, 116). In particular, the primary winding conductor 100 extends such that each rectifier transistor is completely vertically aligned on the primary winding conductor 100, as... Figure 9 As shown.

[0062] Depending on the phase of the input AC signal, the primary current flows in a clockwise direction, for example... Figure 9 The primary current 101 shown flows, or counterclockwise, around the primary winding conductor 100. The width of the primary winding conductor 100 is a measure of the distance between its inner and outer edges. The primary current is distributed across the width of the primary winding conductor, but is concentrated according to the magnetic field lines formed by the flow path of the secondary current through the secondary winding conductor. Depending on the direction of the primary current, the secondary current flows counterclockwise, for example... Figure 7 The secondary current 105 shown, or flowing clockwise around the secondary winding conductor 112, for example... Figure 8 The secondary current shown is 107. The secondary current flows in the opposite direction to the primary current.

[0063] Although the secondary current is distributed across the secondary winding conductors, it is not uniformly distributed. Because multiple rectifier transistors are located at different positions on the secondary winding conductors, the secondary current path is divided into multiple concentrated paths, each terminating at one of the rectifier transistors, for example... Figure 7 The four secondary current paths 105 or shown Figure 8 The four secondary current paths 107 are shown. The secondary current flowing through the secondary winding conductors generates a corresponding magnetic field. Magnetic field lines are formed based on the multiple concentrated paths of the secondary current. This magnetic field then affects the primary current path, which is also divided into multiple concentrated paths based on the magnetic field. (For example, in applications...) Figure 5-9 The structure shown flows to, as Figure 7 and 8 The concentrated paths of the secondary current in each secondary winding conductor of each rectifier transistor, as shown, generate magnetic fields that affect the primary current, thus forming complementary concentrated paths in the primary winding conductor, such as... Figure 9 As shown. Thus, the primary current path (such as...) Figure 9 As shown, it flows as a concentrated path distributed on the extended primary winding conductor, below the top side and above the bottom side of the rectifier transistor. The secondary current path distribution is as a concentrated secondary current path, where each passes through a corresponding rectifier transistor, such as... Figure 8 and 9 As shown. Figure 4As shown, the primary current path through the primary winding conductor is divided into multiple lumped paths. Figure 7 and 8 The secondary current path shown and Figure 9 The primary current path shown is for illustrative purposes only. The actual secondary current path depends on the shape and configuration of the secondary winding conductors, the physical unit of each rectifier transistor, and the associated interconnections with the secondary winding conductors. The primary current path is distributed and concentrated across the entire primary winding conductor according to the local magnetic field generated by the secondary winding path.

[0064] All connections between the secondary winding conductor and the rectifier transistor occur within the coverage area of ​​the primary current path. In other words, the primary and secondary winding conductors are formed in the PCB stack and aligned relative to each other, such that the rectifier transistor is located at a position connected to the secondary winding conductor that is vertically aligned with a portion of the primary winding conductor. This makes the primary current path, which includes all the concentrated paths constituting the primary current path, vertically aligned with the corresponding concentrated paths of the rectifier transistor and the secondary current flowing through the secondary winding conductor.

[0065] In applications requiring the connection of multiple rectifier transistors to both the high-side and low-side voltage rails, the multilayer transformer structure described herein offers significant advantages. The configuration of the primary and secondary winding conductors, as shown and described, and the positioning of the rectifier transistors, result in greater current balance through the rectifier transistors because the primary current is no longer concentrated near the outer periphery of the primary winding conductors, such as... Figure 2 and 3 As shown in the structure. Furthermore, vertically aligning the rectifier transistors on the primary winding conductors allows the concentrated paths of the secondary and primary current paths to also be vertically aligned, thereby reducing proximity effects and associated eddy current losses.

[0066] In the exemplary application, aligning the primary and secondary current paths in the manner described reduces the transformer's AC resistance by approximately 50%, such as... Figure 13 As shown. AC resistance is a function of skin effect and proximity effect. The bottom curve shows resistance similar to... Figure 2 and 3 The AC resistance versus frequency of a conventional multilayer transformer with the structure shown is illustrated. The top curve shows a structure similar to... Figure 5-9 The diagram shows the relationship between the AC resistance and frequency of a multilayer transformer with the shown structure. The gap between the two curves represents the amount of loss eliminated by replacing the conventional structure with a multilayer transformer.

[0067] Figure 14A graph showing efficiency versus power is presented. Curves 510 and 512 show power dissipation curves, which are input power minus output power. In particular, curve 502 shows a conventional power converter circuit, such as... Figure 1-3 The power dissipation curve of the power converter circuit is shown, and curve 500 shows the power converter circuit of this application, for example. Figure 4-9 The power dissipation curves of the power converter circuit are shown. Curves 500 and 502 express the ratio of output power to input power as a percentage. In particular, curve 510 shows a conventional power converter circuit, such as... Figure 1-3 The ratio of the output power to the input power of the power converter circuit is given by curve 512, which illustrates, for example, the power converter circuit of this application. Figure 4-9 The ratio of the output power to the input power of the power converter circuit.

[0068] Compared to conventional power converter circuits, the circuit diagram of the power converter circuit is similar, but the layout of the transformer windings and the relative positioning of the rectifier transistors are changed. The multilayer transformer structure allows for the injection and removal of DC current from the transformer block. This is achieved by configuring the DC node protrusion 120 connected to the rectifier transistors to be vertically aligned with the extension of the primary winding conductor (primary winding conductor arm 102). Since the DC node protrusion 120 carries DC current, DC current exists within the transformer block, which is a vertical stack of primary and secondary winding conductors. This multilayer transformer structure is the opposite of the usual practice of placing rectifier components outside the vertical coverage area of ​​a multilayer transformer within a PCB stack. In this conventional configuration, AC current is injected and removed from the transformer block, keeping the DC current outside the transformer block.

[0069] The location of the DC bump enables the interconnection path for the rectifier transistor outputs, while also providing a structural configuration that positions all rectifier transistors within the AC current path, such as vertical alignment of the rectifier transistors with the primary winding conductors in the PCB stack. Since secondary current flows through the rectifier transistors, the distribution of secondary current through the secondary winding conductors is determined by the physical positioning of the rectifier transistors. Subsequently, through, for example... Figure 7 and 8 The distribution of secondary current in the secondary winding conductors, as shown, generates magnetic field lines based on this secondary current distribution. The primary winding conductors are configured to extend at least to be vertically aligned with the rectifier transistor to ensure that the magnetic field lines induce a distribution of the primary current path through the primary winding conductors to match the distribution of the secondary current path, for example... Figure 6 As shown, this maximizes the proximity of the secondary and primary currents and reduces proximity effects and associated eddy current losses.

[0070] This application has been described with reference to specific embodiments in conjunction with details to facilitate an understanding of the construction and operating principles of multilayer transformer structures. Many components shown and described in the various figures can be interchanged to achieve the desired results, and this description should also be construed as including such interchanges. Therefore, references to specific embodiments and their details herein are not intended to limit the scope of the appended claims. It will be apparent to those skilled in the art that modifications can be made to the embodiments chosen for illustration without departing from the spirit and scope of this application.

Claims

1. A power conversion circuit, comprising: a. A printed circuit board stack comprising multiple layers stacked together; b. A multilayer transformer formed within a printed circuit board stack, wherein the multilayer transformer includes a plurality of primary winding conductors and a plurality of secondary winding conductors, each primary winding conductor forming a corresponding layer of the printed circuit board stack, and each secondary winding conductor forming a corresponding layer of the printed circuit board stack, further wherein the coverage area of ​​each primary winding conductor is configured to substantially vertically overlap the entire coverage area of ​​each secondary winding conductor; and c. Multiple rectifier transistors, each connected to one of multiple secondary winding conductors; Each of the plurality of rectifier transistors is vertically aligned with the coverage area of ​​each primary winding conductor.

2. The power conversion circuit according to claim 1, wherein, The plurality of rectifier transistors are physically positioned relative to the plurality of primary winding conductors to be vertically aligned with the AC current path through the multilayer transformer.

3. The power conversion circuit according to claim 2, wherein, The AC current path includes the primary current path through each primary winding conductor.

4. The power conversion circuit according to claim 1, wherein, The structure of the multilayer transformer enables the injection and removal of DC current into and out of the transformer block, which is defined as a vertical space formed by a plurality of vertically aligned and stacked primary winding conductors and a plurality of secondary winding conductors.

5. The power conversion circuit according to claim 1, wherein, Each secondary winding conductor includes multiple secondary winding conductor arms.

6. The power conversion circuit according to claim 5, wherein, Each secondary winding conductor includes a primary winding conductor arm and a secondary winding conductor arm separated by a discontinuity break in the secondary winding conductor.

7. The power conversion circuit according to claim 6, wherein, Each layer in the printed circuit board stack, including the secondary winding conductors connected to the rectifier transistor, also includes a DC node conductor, further wherein the DC node conductor includes a DC node protrusion extending into a discontinuous break between the first and second secondary winding conductor arms.

8. The power conversion circuit according to claim 7, wherein, The DC node protrusion is vertically aligned with each primary winding conductor.

9. The power conversion circuit according to claim 7, wherein, One or more connection points on each rectifier transistor are connected to one of the secondary winding conductors, and one or more other connection points on each rectifier transistor are connected to a DC node conductor on the same layer as the connected secondary winding conductor.

10. The power conversion circuit according to claim 9, wherein, One or more other connection points on each rectifier transistor, connected to the DC node conductor on the same layer as the connected secondary winding conductor, are connected to the DC node protrusion.

11. The power conversion circuit according to claim 7, wherein, Each rectifier transistor physically spans the discontinuity between the DC node protrusion and one of the primary winding conductor arms and the secondary winding conductor arm.

12. A power conversion circuit, comprising: a. A printed circuit board stack comprising multiple layers stacked together; b. A multilayer transformer formed within a printed circuit board stack, wherein the multilayer transformer includes a plurality of primary winding conductors and a plurality of secondary winding conductors vertically aligned with the plurality of primary winding conductors, further wherein the coverage area of ​​each primary winding conductor is configured to substantially vertically overlap the entire coverage area of ​​each secondary winding conductor; and c. Multiple rectifier transistors, each connected to one of multiple secondary winding conductors. The structure of the multilayer transformer enables the injection and removal of DC current into and out of the transformer block, which is defined as a vertical space formed by a plurality of vertically aligned and stacked primary winding conductors and a plurality of secondary winding conductors. Each of the plurality of rectifier transistors is vertically aligned with the coverage area of ​​each primary winding conductor.

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