PATENT DOCUMENT

Publication Number: US-10063149-B2
Application Number: US-201715631811-A
Country: US
Kind Code: B2

Title: Multi-phase switching power converter module stack

Abstract:
A module stack includes a lower module, a middle module above the lower module, and an upper module above the middle module. The lower module has power stage control circuitry configured to convert a PWM input signal into phase driver control signals, and power stages to be controlled by the phase driver control signals, respectively. The middle module has phase inductors each having a respective winding and a respective magnetic core. The respective winding has one end joined to a respective one of the power stages in the lower module and another end joined to a common node in the middle module. The upper module has a current sense resistor that has one end joined to the common node in the middle module and another end joined to an output node in the upper module. Other embodiments are also described and claimed.

Claims:
What is claimed is: 
     
       1. A multi-phase switching power converter, comprising:
 a module stack including a lower module, a middle module above the lower module, and an upper module above the middle module, 
 the lower module having power stage control circuitry configured to convert a pulse width modulated (PWM) input signal into a plurality of phase driver control signals and a plurality of power stages to be controlled by each of the plurality of phase driver control signals, respectively, 
 the middle module having a plurality of phase inductors each having a respective winding and a respective magnetic core, wherein the respective winding of each of the plurality of phase inductors has one end joined to a respective one of the power stages in the lower module and another end joined to a common node in the middle module, and 
 the upper module having a current sense resistor that has one end joined to the common node in the middle module and another end joined to an output node in the upper module. 
 
     
     
       2. The multi-phase switching power converter of  claim 1 , wherein the power stage control circuitry is configured to generate the plurality of phase driver input signals based on a plurality of feedback voltage signals to balance currents in the phase inductors. 
     
     
       3. The multi-phase switching power converter of  claim 2 , wherein each of the plurality of feedback voltage signals is routed through each of a plurality of conductive paths, respectively, that are joined to the common node in the middle module and to the output node in the upper module and that extend downward through the middle module and into the lower module, where they join the power stage control circuitry. 
     
     
       4. The multi-phase switching power converter of  claim 1 , wherein the middle module comprises a printed circuit board in which the respective magnetic core of each of the plurality of phase inductors is formed as embedded magnetics. 
     
     
       5. The multi-phase switching power converter of  claim 1 , wherein the respective magnetic core of each of the plurality of phase inductors is a laminated magnetic core, and the respective winding is formed as metal laminations. 
     
     
       6. The multi-phase switching power converter of  claim 1 , wherein the respective magnetic core of each of the plurality of phase inductors is formed of nano-magnetic material. 
     
     
       7. The multi-phase switching power converter of  claim 1 , wherein the lower module comprises an integrated circuit surface mount package or chip carrier selected from the group consisting of a ball grid array, a line grid array, and a flat package, and whose external connections are exposed on a bottom surface of the lower module and are to be soldered to a printed circuit board. 
     
     
       8. The multi-phase switching power converter of  claim 1 , wherein the upper module has a single metal layer in which the current sense resistor is formed and above which there is no electronic circuitry. 
     
     
       9. The multi-phase switching power converter of  claim 1 , wherein the upper module and the middle module are joined to each other along an upper planar, patterned metal layer, and wherein the middle module and the lower module are joined to each other along a lower planar, patterned metal layer. 
     
     
       10. The multi-phase switching power converter of  claim 1 , wherein each of the lower module, the middle module, and the upper module comprises a metal laminate structure, wherein a metal path is defined in the laminate structures that joins and extends from the output node in the upper module, through the middle module, to an output portion formed in the lower module. 
     
     
       11. The multi-phase switching power converter of  claim 10 , wherein the lower module comprises an integrated circuit surface mount package, a chip carrier, or a printed circuit board (PCB) having a plurality of external electrical connections formed on the bottom surface of the lower module. 
     
     
       12. The multi-phase switching power converter of  claim 11 , in combination with:
 a further PCB having a plurality of pads to which the external electrical connections of the lower module are soldered, and 
 an output filter capacitor having a terminal that is soldered to a pad in the further PCB, wherein a metal trace in the further PCB joins the pad to one of the plurality of pads to which an external electrical connection of the lower module is soldered that is joined to the output portion in the lower module. 
 
     
     
       13. A multi-phase switching power converter, comprising:
 a module stack that includes a lower module and an upper module, wherein the upper module is above the lower module and integrated therewith in the module stack, 
 wherein the lower module has power stage control circuitry configured to convert a pulse width modulated (PWM) input signal into a plurality of phase driver signals and a plurality of power stages, coupled to a high side supply input and a low side return or ground, to be controlled by each of the plurality of phase driver signals, respectively, 
 wherein the upper module has a plurality of phase inductors each having a respective winding and a respective magnetic core, wherein the respective winding of each of the phase inductors has one end joined to a respective one of the power stages in the lower module and another end joined to a common node in the upper module, and 
 wherein the lower module comprises an integrated circuit surface mount package, chip carrier, or printed circuit board (PCB) having formed on a bottom surface of the lower module a plurality of external electrical connections that include:
 a first group of external electrical connections that are joined to the high side supply input to deliver input power to the converter, 
 a second group of external electrical connections that are joined to the low side return or ground in the lower module, and 
 a third group of external electrical connections that are joined to the common node in the upper module to deliver output power from the converter. 
 
 
     
     
       14. The multi-phase switching power converter of  claim 13 , further comprising:
 a further PCB having a plurality of pads to which the first, second, and third groups of the external electrical connections of the lower module are soldered; and 
 an output filter capacitor having a terminal that is soldered to a pad in the further PCB that is joined, via a metal trace in the further PCB, to one of the plurality of pads to which an external electrical connection of the third group is soldered that is joined to the common node. 
 
     
     
       15. The multi-phase switching power converter of  claim 14 , further comprising:
 a switch mode power supply (SMPS) controller mounted on the further PCB and configured to produce the PWM input signal, wherein the further PCB has a further metal trace therein to conduct the PWM input signal and join one of the plurality of external electrical connections of the lower module. 
 
     
     
       16. The multi-phase switching power converter of  claim 13 , wherein each of the lower module and the upper module comprises a multi-layer metal laminate structure, wherein a metal path is formed in the laminate structures that joins the common node in the upper module and extends downward to an output portion that is patterned in a metal layer at a bottom surface of the lower module. 
     
     
       17. The multi-phase switching power converter of  claim 13 , wherein the power stage control circuitry is configured to control the plurality of phase driver signals based on a plurality of feedback voltage signals, to balance currents in the plurality of phase inductors, wherein each of the plurality of feedback voltage signals is routed through each of a plurality of conductive paths, respectively, formed solely in the lower module and that join the power stages without extending into the upper module. 
     
     
       18. The multi-phase switching power converter of  claim 13 , wherein the upper module and the lower module are joined to each other along a planar, patterned metal layer, wherein the upper module is defined as being above the planar, patterned metal layer, and wherein the lower module is defined as being below the planar, patterned metal layer. 
     
     
       19. The multi-phase switching power converter of  claim 13 , wherein the power stage control circuitry is configured to convert the PWM input signal is into two phase driver signals, and wherein the plurality of power stages consists of first and second power stages controlled by each of the two phase driver signals, respectively. 
     
     
       20. A multi-phase switching power converter comprising:
 a module stack including a lower module, a middle module above the lower module, and an upper module above the middle module, 
 the lower module having power stage control circuitry configured to convert a pulse width modulated (PWM) input signal into a plurality of phase driver control signals and a plurality of power stages to be controlled by each of the plurality of phase driver control signals, respectively, 
 the middle module having a plurality of phase inductors each having a respective winding and a respective magnetic core, wherein the respective winding of each of the phase inductors has one end joined to a respective one of the power stages in the lower module and another end joined to a respective one of a plurality of inductor nodes in the middle module, and 
 the upper module having a plurality of current sense resistors, each having one end joined to the respective one of the plurality of inductor nodes in the upper module and another end joined to an output node in the upper module. 
 
     
     
       21. The multi-phase switching power converter of  claim 20 , wherein the power stage control circuitry is configured to generate the plurality of phase driver input signals based on a plurality of feedback voltage signals to balance currents in the phase inductors. 
     
     
       22. The multi-phase switching power converter of  claim 21 , wherein each of the plurality of feedback voltage signals is routed through each of a plurality of conductive paths, respectively, that include:
 a first path that joins a first one of a plurality of inductor node upper portions in the upper module and extends downward through the middle module and into the lower module, where it joins a feedback input of the power stage control circuitry; 
 a second path that joins a second one of the plurality of inductor node upper portions in the upper module and extends downward through the middle module and into the lower module, where it joins another feedback input of the power stage control circuitry; and 
 a third path that joins the output node in the upper module and extends downward through the middle module and into the lower module, where it joins a further feedback input of the power stage control circuitry. 
 
     
     
       23. The multi-phase switching power converter of  claim 22 , wherein, in the upper module, each of the plurality of current sense resistors comprises a respective phase current sense resistor body that, at one end, is joined to and extends from a respective one of a plurality of inductor node upper portions in the upper module to another end that is joined to the output node in the upper module.

Description:
This application claims the benefits of the earlier filing date of U.S. Provisional Patent Application No. 62/426,120, filed Nov. 23, 2016. 
    
    
     FIELD 
     An embodiment of the invention is a module stack for a multi-phase, dc-dc switching power converter in which power stage control circuitry, power stages, phase inductors and a current sense resistor are arranged into three, stacked modules. Other embodiments are also described and claimed. 
     BACKGROUND 
     A multi-phase, switch mode power supply (SMPS) power converter is particularly suitable as a voltage regulating power supply for space-constrained applications in which greater power density and conversion efficiency are desired. These desirable output characteristics invoke the use of high permeability magnetic materials in the phase inductors as well as techniques for miniaturization of the inductors and the overall packaging of the power converter. A typical dc-dc power converter includes the following components: an SMPS controller that implements for example a buck conversion topology to also achieve voltage regulation at an output node, power stage control circuitry that converts a pulse width modulation (PWM) signal from the SMPS controller into two or more phase driver control signals each of which is input to a respective phase driver circuit, a number of power stages each to be controlled by the outputs of a respective phase driver circuit, a number of phase inductors, an output filter capacitor, a current sense resistor to measure load current of the converter, and voltage feedback paths from the sense resistor back to the power stage control circuitry. It is a difficult problem to design such a power converter to have a certain output power rating and to also fit within a specified volume of space. 
     SUMMARY 
     A first embodiment of the invention is a module stack that may become a part of a multi-phase switching power converter, e.g., a dc voltage regulator, which exhibits a compact profile from various directions, making it particularly suitable for space-constrained applications. The module stack includes a lower module, a middle module above the lower module, and an upper module above the middle module. The lower module has power stage control circuitry configured to convert a pulse width modulated (PWM) input signal into a number of phase driver input signals. The lower module also has therein a number of power stages to be controlled by the phase driver input signals, respectively. The middle module has a number of phase inductors each having a respective winding and a respective magnetic core, wherein the respective winding has one end joined to a respective one of the power stages in the lower module and another end joined to a common node in the middle module. The upper module has a current sense resistor that has one end joined to the common node in the middle module and another end joined to an output node in the upper module. Such an arrangement yields a desirable side profile and a desirable printed circuit board (PCB) footprint at the lower module, with a further benefit of forming the current sense resistor in a metal layer of the upper module that may also effectively act as a heat sink for the phase inductors and power stages that are below it. 
     In a second embodiment, the current sense resistor that is in the upper module of the first embodiment (and is used to sense the load current) is absent, while the lower module may be as in the first embodiment. The middle module (also referred to now as the upper module) still has the phase inductors therein wherein the respective winding of each of the phase inductors has one end joined to a respective one of the power stages in the lower module. However, the other end of the respective winding (of each of the phase inductors) is now joined to a converter output that is in the same module as the phase inductors. In such an embodiment, current sensing (for use by the driver control circuitry when controlling the phase driver input signals to balance the currents in the phase inductors) may be achieved on a per-phase basis, by using the “on-resistance” of the switches that make up the power stages. To sense these on-resistances, a number of feedback voltage signals are routed through respective conductive paths that are formed solely in the lower module and that join the power stages to the driver control circuitry (without extending into the upper module). Such an arrangement yields a shorter side profile for the overall structure (due to the absence of an upper layer in which a current sense resistance is formed), as well a desirable PCB footprint at the lower module. 
     The lower module may include an integrated circuit surface mount package, a chip carrier or a printed circuit board (PCB), in which the power stage control circuitry may be realized, that has a number of external electrical connections formed on a bottom surface of the lower module and that are joined to i) a high side supply input and a low side return or ground in the lower module, and ii) the converter output in the upper module. 
     In a third embodiment, output power is combined after, or “downstream” of, individual phase current sense resistors that are formed in the upper module. Here, the lower module may be as in the first embodiment, and the middle module still has the phase inductors therein, wherein the respective winding of each of the phase inductors has one end joined to a respective one of the power stages in the lower module. However, the other end of the respective winding is now joined to a respective inductor lower portion that is in the same module as the phase inductors. In the case of a two-phase module stack, there is an inductor  1  lower portion that is joined to an inductor  1  upper portion in the upper module, and an inductor  2  lower portion that is joined to an inductor  2  upper portion in the upper module. Also, multiple (e.g., two) phase current sense resistors are formed in the upper module each having i) one end joined to the respective one of the inductor lower portions in the middle module (through the respective one of the inductor upper portions in the upper module) and ii) another end joined to an output node in the upper module. In this way, the output power from multiple phases may be combined in the upper module, downstream of the phase current sense resistors. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. Also, in the interest of conciseness and reducing the total number of figures, a given figure may be used to illustrate the features of more than one embodiment of the invention, and not all elements in the figure may be required for a given embodiment. 
         FIG. 1A  is a circuit schematic illustrating part of a multi-phase switching power converter that can be arranged into a module stack having the lower, middle and upper modules, and wherein output power is combined before, or “upstream” of, an output current sense element. 
         FIG. 1B  is a side view of the module stack. 
         FIG. 2  depicts an example layout of some of the conductive nodes in the upper module of a module stack having the output current sense arrangement of  FIG. 1A . 
         FIG. 3  depicts an example layout of some of the conductive portions at a top surface of the middle module, in the case of a module stack having only two phases and the output current sense arrangement of  FIG. 1A . 
         FIG. 4  depicts an example layout for the magnetic cores and windings of phase inductors in the two-phase middle module of  FIG. 3 . 
         FIG. 5  depicts a cross-section of the magnetic cores and windings of  FIG. 4 . 
         FIG. 6  shows a top view of the top surface of the lower module that joins the middle module of  FIG. 3  and  FIG. 4 . 
         FIG. 7  depicts a view of the bottom surface the lower module, in which an example layout of some of the conductive nodes can be seen. 
         FIG. 8  is a circuit schematic illustrating part of a multi-phase switching power converter that is similar to  FIG. 1A  except that output power is combined after, or “downstream” of, individual phase current sense elements. 
         FIG. 9  depicts an example layout of some of the conductive nodes in the upper module of a module stack having the individual phase current sense arrangement of  FIG. 8 . 
         FIG. 10  depicts an example layout of some of the conductive portions at a top surface of the middle module, in the case of a module stack having only two phases and the individual phase current sense arrangement of  FIG. 8 . 
         FIG. 11  depicts an example layout for the magnetic cores and windings of phase inductors in the two-phase middle module of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Several embodiments of the invention with reference to the appended drawings are now explained. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not explicitly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 
       FIG. 1A  is a circuit schematic illustrating part of a multi-phase, switch mode power supply (SMPS) or switching, power converter. The converter has an output node as shown that is coupled to a filter capacitor (now shown) and to a load (not shown). Driver control circuitry  12  (as part of power stage control circuitry  16 ) is configured to convert a single pulse width modulated (PWM) input signal into at least two phase driver control signals (in this example only two, namely phase  1  control and phase  2  control). In addition, the driver control circuitry  12  has inputs fb+ and fb− through which it may process current sensing signals through terminals a, b, c, d as described below, into current information (current feedback) and then communicates this information back to the SMPS controller as shown. In one embodiment, the converter has at least two phases, and the driver control circuitry  12  can convert the single PWM input signal into identical or 180 degree phase shifted PWM waveforms (of the two phase driver control signals, phase  1  control and phase  2  control) that can be at the same frequency as the PWM input or one half of it. In other embodiments, the converter has more than two phases, such that the single PWM signal is converted into a corresponding number (more than two) in-phase or out of phase PWM signals. Also, the term “PWM” is used broadly here to also encompass other SMPS modulation modes or time ratio control, including pulse frequency modulation, pulse density modulation, and mixed or hybrid modulation. 
     A phase  1  inductor  10  and a phase  2  inductor  11  are coupled to a “common” node at their far ends, while the near ends are coupled to node sw 1  of a phase  1  power stage  15  and node sw 2  of a phase  2  power stage  17 , respectively, as shown. In other words, in such an embodiment, all of the phase inductors (there may be more than two) are tied to a common node or common terminal. The phase  1  power stage  15  has a high side 1 switch  6  and a low side 1 switch  7  coupled as shown to a high side supply input and a low side return or ground, respectively. The phase  2  power stage  17  has a similar arrangement, where a high side 2 switch  8  and a low side 2 switch  9  are coupled as shown to the high side supply input and the low side return or ground, respectively. The phase driver control signals produced by the driver control circuitry  12  are translated by phase  1  driver  4  and phase  2  driver  5 , respectively, into signals that can be applied directly to the control electrodes of transistors, e.g., field effect transistors, FETs, that constitute the high side and low side switches. In this example, the phase driver control signals are translated by the phase  1  driver  4  and the phase  2  driver  5  into pairs of high side switch and low side switch control signals that in turn directly open and close their respective switches  6 - 9 . The phase  1  driver  4  and the phase  2  driver  5  may also be configured to protect the power FETs, that make up the high side and low side switches, against any desired combination of overload, short circuit, over temperature, input over-voltage, and input under-voltage conditions. 
     The PWM-based switching of the phase  1  power stage  15  and the phase  2  power stage  17  results in a controlled transfer of power (current) from the supply input, through the two phases, to the “output” node. In the example shown, the converter has a step down or buck-type conversion topology that may be configured to regulate the output node voltage, while delivering power to the load from the supply input that is at a different voltage (higher than the output node voltage). A SMPS controller (not shown) produces the PWM input signal to achieve the controlled power transfer, based on voltage feedback from the output node of the converter that represents a load voltage, and optionally current feedback obtained directly from the output node and that represents load current, or indirectly from the driver control circuitry  12  as the latter senses either the total output (or load) current or individual phase currents, for example as described below. 
     Note that the phase driver control signals (phase  1  control and phase  2  control) may be adjusted by the driver control circuitry  12 , based on feedback voltage signals fb+ and fb−, to balance the currents in the two phases (phase  1  inductor  10  and the phase  2  inductor  11 ), respectively. A combined or sum current of all of the phase inductors (also referred to as total output current here) may be sensed at the driver control circuitry  12  through the use of a current sense resistor  13 , described as follow. In one embodiment (as shown), the feedback voltage signals fb+ and fb− are taken from the two terminals of the current sense resistor  13  that has one end or terminal joined to the common node and another end or terminal joined to the output node as shown. Based on a stored resistance value representing the resistance of the current sense resistor  13 , a difference between fb+ and fb− is sensed by the driver control circuitry  12  to determine a measure of the load current through the resistor  13 . Additional information may be available to the driver control circuitry  12 , e.g., stored inductance values representing the inductance of the phase  1  inductor and that of the phase  2  inductor, and knowledge of which phase is presently “firing” at the moment the current is being sensed, and other individual phase information that is communicated from each of the phase  1  driver  4  and phase  2  driver  5 , to the driver control circuitry  12 , that enables the latter to adjust duty cycle or pulse width of the phase  1  control and phase  2  control driver signals, to force a balance between the two phase currents. For example, the driver control circuitry  12  may use the sensed total output current and any individual current information, to achieve current balancing amongst the phases. 
     Another approach to balancing the phase currents may be to route the feedback voltage signals fb+ and fb− from the phase  1  power stage  15 , providing a measure of the voltage across the high side 1 switch  6  or across the low side 1 switch  7 , which can be used together with a stored resistance value representing the on-resistance of the switch to compute the inductor current of the phase  1  inductor  10 . A similar arrangement, using an additional pair of fb+, fb− inputs that are routed to the high side or low side switch in the phase  2  power stage  17 , enables the computation of the inductor current of the phase  2  inductor  11 . 
     Still referring to  FIG. 1A , in accordance with an embodiment of the invention, this portion of the power converter is manufactured as a single module stack. The vertical dashed lines in  FIG. 1A  may translate to the horizontal planes that mark the boundaries of at least three modules including a lower module  3 , a middle module  2  that is above the lower module  3 , and an upper module  1  that is above the middle module—see the side view of the module stack in  FIG. 1B . The modules are joined to each other to form a single stack as shown. The lower module  3  has external connections as shown that are exposed on a bottom surface thereof and that are to be soldered to a printed circuit board (PCB)—not shown. The external connections may conduct the following: the PWM input signal, processed load current information (sourced from or to the SMPS controller); the low side return or ground; the high side supply input; and the output. In one embodiment, to complete the power converter, the module stack is assembled in combination with the PCB, where the latter has pads to which the external electrical connections of the lower module  3  are soldered. There is also an output filter capacitor (not shown) having a terminal that is soldered to a pad in the PCB, wherein a metal trace in the PCB joins the pad to one of the pads to which an external electrical connection of the lower module  3  is soldered that is joined to the output node through the lower module  3 . This provides a particularly desirable packaging solution for the power converter, in space-constrained applications. 
     To ease understanding of the written description here in relation to the drawings, the following should be noted. The terms “upper” and “lower” or “above” and “below” are used to describe portions of a node or element in a vertical direction or along the z-axis. For example and referring to  FIG. 1B  to illustrate this, a node or element may have a height or thickness defined by the combination of its upper portion joined to its lower portion; the upper portion may be part of the upper module  1 , while the lower portion may be part of the middle module  2 ; in another instance, the upper portion may be at the top surface of the middle module  2 , while the lower portion is also in the middle module  2  but of course below the upper portion). 
     The terms “front” and “rear”, or “ahead” and “behind”, refer to horizontal positions that are along the y-axis, and the terms “left” and “right” refer to horizontal positions that are along the x-axis—again, see  FIG. 1B  to illustrate this using an example. A conductive path or node or other element may have a lateral or sideways “spread” that may be defined by its front portion joined to its rear portion, and/or by its left portion joined to its right portion. In most instances here, the front, rear, left and right portions of an element are said to be in the same module. 
     Referring now to  FIG. 2 , this figure depicts an example layout of the conductive paths in the upper module  1 . The conductive paths shown may be within the same horizontal or x-y plane (e.g., part of a single horizontal metal layer) in the upper module  1 , where they form the current sense resistor  13  and parts of the common and output nodes—see  FIG. 1A . The current sense resistor  13  may be formed in a metal layer that has been patterned to have a sense resistor body portion  23  having a front side boundary  20  and a rear side boundary  21 . These are joined to a common node upper portion  24  that is at the front boundary of the upper module  1 , and to an output node upper portion  25  that is at the rear boundary of the upper module  1 , as shown. The conductivity, thickness, shape and size of the sense resistor body portion  23  and its interface with portions  24 ,  25  may be designed to yield a known resistance between sense terminals a, b at one end and sense terminals c, d at another end, for the purpose of current sensing. For example, as depicted in the drawing, the sense resistor body portion  23  may be of a different material than the common node upper portion  24  and the output node upper portion  25 ; alternatively, the sense resistor body portion  23  may be formed in the same metal layer and of the same material as the common node upper portion  24  and the output node upper portion  25 . In one embodiment, the upper module  1  has a single metal layer in which the current sense resistor  13  is formed as shown, and above which there is no electronic circuitry that can reduce the heat sink abilities of the top metal layer in the upper module  1 —see  FIG. 1B . This helps the upper module  1  perform as a heat sink for the entire module stack. 
     As seen in  FIG. 1A , the common node extends across the boundary between the middle module  2  and the upper module  1 , as follows. As shown in  FIG. 2 , it has a common node upper portion  24  that lies in the upper module  1 , and, as seen in  FIG. 3 , it also has a common node lower portion  34  that is at the top surface of the middle module  2 . The common node also has a common node further lower portion  44  that is in the middle module  2  (below its top surface)—see  FIG. 4 . 
     As seen in  FIG. 1A , the output node extends across the boundary of modules  1 ,  2  and across the boundary of modules  2 ,  3 , all the way to the bottom surface of module  3 . It has an output node upper portion  25  that lies in the upper module  1 , as seen in  FIG. 2 , and an output node middle portion  35  that is in the top surface of the middle module  2  as shown in  FIG. 3 . The output node also has an output node further middle portion  45  that is in the middle module  2  (below the top surface)—see  FIG. 4 . The output node also has an output node lower portion  65  that is in top surface of the lower module  3 —see  FIG. 6 —and that is joined to an output node further lower portion  75  that may be exposed at the bottom surface of the lower module  3 —see  FIG. 7 . 
     Referring briefly to  FIG. 1A , the current sensing in this embodiment may be performed by the driver control circuitry  12  through a voltage sensed at fb+, fb− which nodes are coupled as shown across the resistor  13 , at sense terminals a, b and c, d, respectively. The sense terminals a, b have upper portions that as shown in  FIG. 2  that are joined to the common node upper portion  24 , while the sense terminals c, d have their upper portions joined to the output node upper portion  25 , as shown. It should be noted that while a pair of sense terminals are shown at each end of the resistor  13  in  FIG. 2 , corresponding to a pair of paths coupling each end of the resistor  13  to its respective fb+, fb− input (see  FIG. 1A ), an alternative is to have a single path coupling each end of the resistor  13  to the fb+ or fb− input, provided it has sufficiently low resistance for current sensing purposes. In these instances, it can be seen that the feedback voltage signals are being routed through several conductive paths, respectively, that are joined to the common node and to the output node in the upper module, and that extend downward through the middle module and into the lower module where they join the power stage control circuitry  16 . 
       FIGS. 3-5  illustrate different views of an example of the middle module  2 . In one embodiment, the middle module  2  is a printed circuit board in which the respective magnetic core of each of the phase inductors are formed as described below, as embedded magnetics. In another embodiment, the respective magnetic core of each of the phase inductors is a laminated magnetic core, and the respective winding is formed as metal laminations. In yet another embodiment, the respective magnetic core of each of the phase inductors is formed of Nano-magnetic material. 
       FIG. 3  shows a top metal layer (a top surface) of the middle module  2  that has been patterned, as follows. Referring also to  FIG. 2 , the common node upper portion  24  that forms part of the common node in  FIG. 2  joins a common node lower portion  34  that is formed in the middle module  2  and that aligns directly below the upper portion  24 , as seen in  FIG. 3 . Similarly, the output node upper portion  25  that forms part of the output node in the upper module  1  joins the output node middle portion  35  in the middle module  2 . 
       FIG. 3  also shows four middle portions at the four corners of the middle module  2 , respectively, that align directly below and join their corresponding upper portions in the upper module  1 —see  FIG. 2 . These define in part the sense terminals a, b and c, d—see  FIG. 1A . 
     Still referring to  FIG. 3 , also formed in the middle module  2  are core 1  upper portion  36  and core 2  upper portion  37 , of the two magnetic cores, core 1  and core 2 , respectively, which are parts of the phase  1  inductor  10  and phase  2  inductor  11 , respectively—see  FIG. 1A . This is for the case of a module stack having only two phases (thus two magnetic cores and two windings), which is the example depicted in  FIG. 1A . As seen in that figure, the middle module  2  contains the phase inductors  10 ,  11  each being formed of a respective winding and a respective magnetic core. A winding 1  of the phase  1  inductor  10  has one end that is joined to node sw 1  of the phase  1  power stage  15  (in the lower module  3 ), and another end joined to the common node in the middle module  2 . Similarly, the phase  2  inductor  10  has a winding 2  that has one end joined to node sw 2  of the phase  2  power stage  17 , and another end joined to the common node in the middle module  2 .  FIG. 4  shows a layout for elements of the two inductors, in a horizontal plane that may be cut through the middle (height-wise) of the middle module  2 , below the top surface depicted in  FIG. 3 . This layout exhibits left-right symmetry across a vertical axis that lies in between a node sw 1  upper portion  48  and a node sw 2  upper portion  49 . 
     The following elements are visible in  FIG. 4 : 
     an output node further middle portion  45  is at the rear boundary, while the common node further lower portion  44  is at the front; 
     winding 1  has one end which joins the common node further lower portion  44  of the common node, and then extends rearward and then sideways to the right along the output node further middle portion  45  and around a core 1  lower inner portion  46   b , where it joins the node sw 1  upper portion  48 ;
 
winding 2  has an arrangement that mirrors that of winding 1 —it has one end which also joins the common node further lower portion  44 , and then extends rearward and then sideways to the left along the output node further middle portion  45  and around a core  2  lower inner portion  47   b , where it joins the node sw 2  upper portion  49 ;
 
a core 1  lower outer portion  46   a  of core 1  is at the left boundary of the middle module  2 , and a core 2  lower outer portion  47   a  is at the right boundary (of the middle module  2 );
 
the core 1  lower inner portion  46   b  is immediately surrounded by the winding 1  on the left side, the node sw 1  upper portion  48  on the right side, and the common node further middle portion  44  in front; and
 
the core 2  lower inner portion  47   b  is immediately surrounded by the winding 2  on the right side, the node sw 2  upper portion  49  on the left side, and the common node further middle portion  44  in front.
 
     Also visible in  FIG. 4  are middle portions of the four sense terminals a, b, c, d at the four corners of the middle module  2 , respectively, which continue the downward paths that define in part the sense terminals a, b and c, d—see  FIG. 1A . 
       FIG. 5  is a section taken along line  5 - 5 ′ in  FIG. 4 , showing how in this view, the winding 1  is immediately surrounded by core 1 , and in particular by its upper portion  36  above, its lower outer portion  46   a  on the left and its lower inner portion  46   b  on the right. Similarly, winding 2  is immediately surrounded by core 2 , and in particular by its upper portion  37  above, its lower outer portion  47   a  to the right and its lower inner portion  47   b  to the left. 
     Also in  FIG. 5 , note how the node sw 1  upper portion  48  and the node sw 2  upper portion  49  extend downward to the bottom surface of the middle module  2  as shown. The left-right symmetry mentioned above in relation to  FIG. 4  is also apparent here in  FIG. 5 , across the vertical axis that runs in between the node sw 1  upper portion  48  and the node sw 2  upper portion  49 . 
       FIG. 6  shows a top view of the top surface of the lower module  3  that joins the middle module  2  (in  FIG. 4  and  FIG. 5 ). Note how the node sw 1  upper portion  48  ( FIG. 4 ) is joined to and is aligned directly above a node sw 1  lower portion  68 ; similarly, the node sw 2  upper portion  49  ( FIG. 4 ) is joined to and is aligned directly above a node sw 2  lower portion  69 . Also, the output node further middle portion  45  ( FIG. 4 ) is joined to and is aligned directly above an output node lower portion  65 . The latter is at the rear boundary of the lower module  3 , behind the node sw 1  portions  68 ,  69 . The “empty” regions to the left, right and front of the node sw 1  lower portion  68  and the node sw 2  lower portion  69  may be used to contain the power stages  15 ,  17 , the drivers  4 ,  5 , and the driver control circuitry  12  (see  FIG. 1A ). Also visible in  FIG. 6  are the lower portions of the sense terminals a, b, c, d, at the four corners of the lower module  3 , respectively, that align directly below their respective upper portions in the middle module  2  (as seen in  FIG. 3  and  FIG. 4 ) and in the upper module  1  (as seen in  FIG. 2 ), as part of the paths that define the sense terminals a, b and c, d. 
       FIG. 7  depicts a view of the bottom surface the lower module  3 , in which an example layout of some of the conductive regions (nodes) can be seen. The nodes may be the external connections depicted in  FIG. 1A , exposed on the bottom surface of the lower module  3 , e.g., to enable solder joints to be made between the external connections and corresponding pads in a printed circuit board (PCB)—not shown. In particular, the layout has several larger conductive regions, e.g., each consisting of a group of numerous smaller connections, to support high currents. These larger regions include: an input portion  72  that serves as the high side supply input (see  FIG. 1A ) to the power converter; a ground, GND, portion  71  that serves as the low side return or ground (see  FIG. 1A ); and an output node further lower portion  75  that serves as the output of the power converter. The layout also has several smaller conductive regions, e.g., a handful of external connections, to support low current signals. These may include: the PWM input for the module stack (see  FIG. 1A ); an enable control signal (e.g., that is input to the driver control circuitry  12 , to enable and disable the phase  1  driver and phase  2  driver signals); a fault signal produced by the driver control circuitry  12  that is asserted in the event the latter detects a fault; hand-shaking signals that may be routed to the SMPS controller to establish a digital communications link with the driver control circuitry  12 ; and any other data or control signals. 
     In one embodiment, the lower module  3  is an integrated circuit surface mount package or chip carrier selected from the group consisting of a ball grid array, a line grid array, and a flat package (whose external connections are exposed on a bottom surface thereof and that are to be soldered to a printed circuit board). 
     In one embodiment, the upper module  1  and the middle module  2  are joined to each other along an upper planar, patterned metal layer, and wherein the middle module  2  and the lower module  3  are joined to each other along a lower planar, patterned metal layer. 
     In another embodiment, each of the lower module  3 , the middle module  2 , and the upper module  1  comprises a metal laminate structure, wherein a metal path is defined for the output node in the laminate structures, that joins and extends from a portion formed in the upper module  1 , through the middle module  2 , to a portion formed in the lower module  3 . 
     Some additional variations to the above-described aspects of the module stack are possible. For instance, in the example of  FIG. 1A , the feedback voltage signals at the fb+, fb− inputs of the driver control circuitry  12  are routed through sense terminals a, b, c, d from the lower module  3  upward through the middle module  2  and into the upper module  1  where they join the current sense resistor  13 . An alternative to that approach of using a separate current sense resistor is to use the “on-resistance” of the switches that make up the power stages  15 ,  17 . In that case, the feedback voltage signals at the fb+fb− inputs may be routed through conductive paths, respectively, that are formed solely in the lower module  3  and that join the transistor switches of the power stages  15 ,  17  to the fb+, fb− inputs. The upper module  1  including the current sense resistor  13  therein may in that case be omitted, such as in the embodiment described next. 
     In accordance with another embodiment of the invention, the module stack includes a lower module and an upper module, wherein the upper module is directly above the lower module and integrated therewith in the module stack. This would be similar to  FIG. 1A  except the upper module  1  is absent, such that the middle module  2  is now the “upper module” of the stack. The lower module  3  has the power stage control circuitry  16  as described above, configured to convert the PWM input signal into two or more phase driver signals, and at least the two power stages  15 ,  17  that are coupled to the high side supply input and the low side return or ground. The power stages are controlled by the phase driver signals, respectively, as described above. In this embodiment, the upper module has the phase inductors  10 ,  11  each having a respective winding and a respective magnetic core, wherein the respective winding of each of the phase inductors has one end joined to a respective one of the power stages in the lower module and another end joined to a common node in the upper module. The lower module  3  may include an integrated circuit surface mount package, chip carrier or PCB having formed on a bottom surface of the lower module a number of external electrical connections. These external connections include a first group of external electrical connections that are joined to the high side supply input to deliver input power to the converter, a second group of external electrical connections that are joined to the low side return or ground in the lower module  3 , and a third group of external electrical connections that are joined to the common node in the upper module to deliver output power from the converter. This embodiment, referred to here as a two-module stack, has a shorter height (z-axis) than the ones described above in connection with  FIG. 1A  where a current sense resistor  13  is present in the upper “top” module  1  (resulting in a three-module stack). 
     Similar to the three module stack, the two module stack (having modules  2 ,  3  and not module  1 ) may be assembled onto a further PCB having pads to which the first, second and third groups of the external electrical connections of the lower module are soldered. There may also be an output filter capacitor having a terminal that is soldered to a pad in the further PCB that is joined, via a metal trace in the further PCB, to one of the pads to which an external electrical connection of the third group is soldered that is joined to the common node of the module stack. 
     Additionally, to complete the power converter, the SMPS controller may be mounted on the further PCB. The SMPS controller may be configured to produce the PWM input signal, wherein the further PCB has a further metal trace therein that is to conduct the PWM input signal and that joins one of the external electrical connections of the lower module of the two-module stack. 
     In the two module stack, each of the lower module and the upper module may be a multi-layer metal laminate structure, wherein a metal path is formed in the laminate structures as the common node, extending from a portion in the upper module downward to a portion that is patterned in a metal layer at a bottom surface of the lower module, similar to how the output node portions  45 ,  65 ,  75  are joined to form a metal path in  FIGS. 4, 6, 7 . 
     As was suggested above, in the two-module stack of  FIG. 1A  where the current sense resistor  13  therein is omitted, the power stage control circuitry is configured to control the phase driver signals based on the feedback voltage signals, to balance currents in the phase inductors, wherein the feedback voltage signals are routed through conductive paths, respectively, formed solely in the lower module  3  and that join the power stages without extending into the upper module. 
     Similar to the three-module stack described above, the two-module stack may also be implemented such that its upper module and its lower module are joined to each other along a planar, patterned metal layer, wherein the upper module is defined as being above the planar patterned metal layer and the lower module is defined as being below the planar patterned metal layer. 
     The two-module stack and the three-module stack as described above may be considered to be phase doublers, because they can each convert a single PWM input signal into two, phase driver signals. Either module stack may be replicated to support a power converter that has more than two phases. For example, a six-phase power converter would use three of the phase-doubler module stacks. 
       FIG. 8  is a circuit schematic illustrating part of a multi-phase switching power converter that is similar to  FIG. 1A  except that output power from the multiple phases (here, phase  1  inductor  10  and phase  2  inductor  11 ) is combined at the output node, after or “downstream” of individual phase current sense elements  13   a ,  13   b  through which inductor current of the phase inductors  10 ,  11  flows, respectively. The circuit elements shown may be assembled into a single, module stack similar to the embodiments described above, including the lower module  3 , the middle module  2  above the lower module  3 , and the upper module  1  above the middle module  2 . The lower module  3  has the same power stage control circuitry  16  that is configured to convert the PWM input signal into multiple phase driver control signals (here, two), and that has power stages  15 ,  17  that are to be controlled by the phase driver control signals, respectively, through their respective phase drivers  4 ,  5  (as described above in connection with  FIG. 1A ). 
     The upper module  1  of  FIG. 8  is different than the one of  FIG. 1A  in that it contains multiple current sense resistors  13   a ,  13   b , one in series with each phase inductor.  FIG. 9  depicts an example layout of some of the conductive nodes in the upper module  1  of  FIG. 8 , where it can be seen that the current sense resistor  13   a  has a phase  1  current sense resistor body  85  whose one end is joined to an inductor  1  node upper portion  83 , and another end joined to the output node upper portion  25  in the upper module  1 . Similarly, the current sense resistor  13   b  has a phase  2  current sense resistor body  86  joined at one end to an inductor  2  node upper portion  82 , and another end joined to the output node upper portion  25 . The current sense resistors  13   a ,  13   b  may be designed to be identical as shown, so that the resistance across sense terminals a-c is intended to be the same as the resistance across sense terminals b-d. 
       FIG. 10  depicts an example layout of some of the conductive portions at a top surface of the middle module  2 , in the case of a module stack having only two phases and the individual phase current sense arrangement of  FIG. 8 . The embodiment of  FIG. 10  is similar to the one in  FIG. 3  except as follows: instead of the common node lower portion  34  (which is joined to the common node further lower portion  44  and both of the winding 1  and winding 2  below it—see  FIG. 4 ), there is an inductor  1  node lower portion  87  and a separate (electrically isolated), inductor  2  node lower portion  88 . These lower portions  87 ,  88  are joined to the upper portions  83 ,  84 , respectively, in the upper module  1  (see  FIG. 9 ), through vertical conductive paths formed for example in a multi-layer laminate structure. 
       FIG. 11  depicts an example layout for the magnetic cores and windings of the phase inductors in the two-phase, middle module  2  of  FIG. 10 . The layout is similar to what is shown in  FIG. 4  except as follows: the common node further middle portion  44  is replaced with inductor  1  node further lower portion  89  and inductor  2  node further lower portion  90 , wherein winding 1  has one end joined to the node sw 1  portion  48  (which joins the power stage  15  in the lower module), and another end joined to the inductor  1  node further lower portion  89 . Similarly, winding 2  has one end joined to the node sw 2  portion  49 , which joins the power stage  17  in the lower module  3 , and another end joined to the inductor  2  node further lower portion  90 . 
     The embodiment of  FIGS. 8-11  is similar in layout and functionality to that of  FIGS. 1A-7  except for the individual phase current sensing (through the phase current sense resistors  13   a ,  13   b ) being made available to the driver control circuitry  12 . Here, the phase driver input signals are produced based on at least three, feedback voltage signals at the three inputs, fb−, phase  2  fb+ and phase  1  fb+, to balance currents in the phase inductors. These feedback voltage signals are routed through a number of conductive paths, respectively, that include: a first path (labeled a in  FIGS. 9-11 ) that joins the inductor  1  node upper portion  83  in the upper module  1  and extends downward through the middle module  2  and into the lower module  3  where it joins the power stage control circuitry  16  (see  FIG. 8 ); a second path (labeled b in  FIGS. 9-11 ) that joins the inductor  2  node upper portion  84  in the upper module and extends downward through the middle module  2  and into the lower module  3  where it joins the power stage control circuitry  16 ; and a third path (labeled c in  FIGS. 9-11 ) that joins the output node upper portion  25  in the upper module and extends downward through the middle module  2  and into the lower module  3  where it joins the power stage control circuitry  16 . 
     While certain embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, while a single high side supply input may be shared by the two phases as shown in  FIG. 1A , the two phases may alternatively be coupled to different high side supply inputs (having different voltages). Also, the phase  1  inductor  10  and the phase  2  inductor  11  may be designed or specified to have the same inductance, or they may be designed to have different inductances. The description is thus to be regarded as illustrative instead of limiting.

Metadata:
Filing Date: 20170623
Publication Date: 20180828
Grant Date: 20180828
Priority Date: 20161123
Inventors: AKRE, SUNIL M.
KARIYADAN, SURESH B.
TRIMELONI, VINCENT W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H03K7/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/1584", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03K7/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/1584", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M1/084", "inventive": true, "first": false, "tree": "[]"}, {"code": "H03K7/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/084", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/1584", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M2003/1586", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/003", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M3/1586", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 62147359