POWER CONVERTER WITH A MULTI-TAP AUTOTRANSFORMER

Abstract

A power converter includes an autotransformer, first switches, and second switches. The autotransformer includes a plurality of windings. The first switches are coupled between an input node and an output node of the power converter. The second switches are coupled between a reference potential and the output node. Furthermore, the first switches are operable to control switching of circuit paths comprising the plurality of windings of the autotransformer. The second switches are operable to transfer currents from the plurality of windings of the autotransformer through the second switches to the output node.

Description

Data centers are necessary to provide many services. The energy consumption for all data centers worldwide is approximately 2% of the total energy consumption. Therefore, data center providers are constantly striving to improve efficiency of power conversion to conserve power or to be able to increase CPU / GPU / ASIC performance, etc., of servers in existing data centers. Machine learning and artificial intelligence require very powerful GPUs or custom designed ASICs to meet the required computational power.Nowadays, most digital loads are supplied directly from a 12 VDC bus with a single-stage polyphase buck topology, the so-called voltage regulator module (VRM). However, as the power demand on the digital load increases, conduction losses on the 12 VDC bus become an undesirable bottleneck. This has led to the suggestion of a 48 VDC architecture to provide power.Operation of a system having a 40V to 60 VDC input voltage bus rather than a 12 VDC bus offers practical advantages.For example, the first stage of a conventional power converter is typically configured to down-convert the high input voltage (48 volts DC) to an intermediate voltage. This first stage may be a high efficiency uncontrolled or controlled power converter that provides a downconversion of the input voltage to an intermediate voltage input into a so-called intermediate bus power converter (IBC). The second stage may be based on the common buck converter with very good transient response and high efficiency.This disclosure includes the observation that the power conversion efficiency of conventional switched-capacitor converters (switched-capacitor converters) can be improved. For example, the present examples include novel ways to provide improved switching capacitor converter performance and efficient generation of a corresponding output voltage for this purpose.In particular, according to an example, an apparatus such as a power converter or other suitable entity as discussed herein includes an auto-transformer, first switches, and second switches. The auto-transformer comprises a plurality of windings. The first switches are coupled between an input node and an output node of the device. The second switches are coupled between a reference potential and the output node. The first switches are operable to control switching of circuit paths including the plurality of windings of the auto-transformer; the second switches are operable to transfer currents from the plurality of windings of the auto-transformer through the second switches to the output node.In one example, the currents are first currents as discussed above. It is further noted that the first switches may be configured to transfer second currents from the auto-transformer through the first switches to the output node.According to further examples, the second switches include a first pair of switches arranged in series and a second pair of switches arranged in series; the first pair of switches may be arranged in series between the reference potential and the output node; the second pair of switches may be arranged in series between the reference potential and the output node.The currents discussed herein may include a first current and a second current. The first pair of switches may be configured to control transferring of the first current from the plurality of windings of the auto-transformer to the output node; the second pair of switches may be configured to control transferring of the second current from the plurality of windings of the auto-transformer to the output node.According to another example, the input node of the device may be configured to provide an input voltage to the first switches. The first switches may be configured to include a first switch and a second switch; the first switch may be disposed between the input node and a first circuit path, the first circuit path including a first primary winding of the auto-transformer; the second switch may be disposed between the input node and a second circuit path including a second primary winding of the auto-transformer, the second primary winding being magnetically coupled to the first primary winding. The auto-transformer may further include a secondary winding magnetically coupled to both the first primary winding and the second primary winding; the first circuit path may extend between the first switch and a first node of the secondary winding of the auto-transformer. The second circuit path extends between the second switch and a second node of the secondary winding of the auto-transformer. The second switches may include a third switch and a fourth switch. The third switch may be coupled between the first node of the secondary winding and the output node, wherein the third switch may be configured to control a transfer of a first current of the currents from the first node of the secondary winding to the output node. The fourth switch may be coupled between the second node of the secondary winding and the output node, wherein the fourth switch may be configured to control a transfer of a second current of the currents from the second node of the secondary winding to the output node.Additionally, the apparatus discussed herein may be configured to include a controller configured to, for a first portion of a respective control cycle of a plurality of control cycles, activate the first switch, wherein activation of the first switch causes the input voltage to be transmitted from the input node through the first switch to the first circuit path, and ii) deactivate the second switch, wherein deactivation of the second switch causes the input voltage to be prevented from being transmitted through the second switch to the second circuit path; and for a second portion of the respective control cycle of a plurality of control cycles, i) to deactivate the first switch, wherein deactivation of the first switch causes preventing transmission of the input voltage through the first switch to the first circuit path, and ii) to activate the second switch, wherein activation of the second switch causes transmission of the input voltage from the input node through the second switch to the second circuit path.Additionally, the first switches discussed herein may include a fifth switch and a sixth switch. The fifth switch may be coupled to the first circuit path and the first switch; the sixth switch may be coupled to the second circuit path and the second switch.The controller may be configured to deactivate the fifth switch and activate the sixth switch for the first portion of the control cycle, wherein activation of the sixth switch causes the second current to be transferred from the second circuit path through the sixth switch to the output node; and deactivate the sixth switch and activate the fifth switch for the second portion of the control cycle, wherein activation of the fifth switch causes the first current to be transferred from the first circuit path through the fifth switch to the output node.It is further noted that the plurality of windings of the auto-transformer may include a plurality of primary windings and a secondary winding. The second switches may include a first switch and a second switch. The first switch may be directly coupled to a first node of the secondary winding, the second switch may be directly coupled to a second node of the secondary winding. The currents discussed herein may include a first current and a second current. The apparatus may further include a controller configured to switch between, i) activation of the first switch in a first portion of a respective control cycle to transfer the first current from the first node of the secondary winding through the first switch to the output node, and ii) activation of the second switch in a second portion of the respective control cycle to transfer the second current from the second node of the secondary winding through the second switch to the output node.According to still further examples, the second switches may include a third switch and a fourth switch. The third switch may be directly coupled to the first node of the secondary winding, the third switch may be directly coupled to the first switch and arranged in series with the first switch. The fourth switch may be directly coupled to the second node of the secondary winding, the fourth switch may be directly coupled to the second switch and arranged in series with the second switch.In addition, the controller may be further configured to activate i) the fourth switch in the first portion of the respective control cycle, wherein activation of the fourth switch causes connection of the second node of the secondary winding to the reference potential; and ii) activate the third switch in the second portion of the respective control cycle, wherein activation of the third switch causes connection of the first node of the secondary winding to the reference potential.According to another example, the apparatus discussed herein may be configured to include multiple capacitors, such as a first capacitor and a second capacitor. The circuit paths may include a first resonant circuit path and a second resonant circuit path, the first resonant circuit path including the first capacitor and a first primary winding of the auto-transformer arranged in series, the second resonant circuit path including the second capacitor and a second primary winding of the auto-transformer arranged in series. The auto-transformer may further include a secondary winding, the secondary winding including a first node and a second node, the first node may couple the first primary winding directly to the secondary winding, the second node may be configured to couple the second primary winding directly to the secondary winding. The second switches may include a first switch and a second switch; wherein the first switch may be coupled between the first node of the secondary winding and the output node; wherein the second switch may be coupled between the second node of the secondary winding and the output node.The auto-transformer may be a matrix multi-tap auto-transformer.In addition, the auto-transformer may have a first primary winding connected between a first node and a second node of the auto-transformer. The auto-transformer may include a secondary winding connected between the second node and a third node of the auto-transformer. The auto-transformer may have a second primary winding connected between the third node and a fourth node of the auto-transformer. The second switches may include a first switch and a second switch. The currents described herein may include a first current and a second current. The first switch may be operable to control conduction of the first current from the second node of the auto-transformer through the first switch to the output node; the second switch may be operable to control conduction of the second current from the third node of the auto-transformer through the second switch to the output node.According to still further examples, the apparatus discussed herein may be configured to include a controller configured to, for a first portion of a control cycle, i) enable the first switch to an ON state, ii) disable the second switch to an OFF state, and iii) couple the third node of the auto-transformer directly to the reference potential; and for a second portion of the control cycle, i) enable the second switch to an ON state, ii) disable the first switch to an OFF state, and iii) couple the second node of the auto-transformer directly to the reference potential.According to another example, the apparatus may include: an auto-transformer including primary windings and a secondary winding; multiple switches including a first switch, a second switch, a third switch, and a fourth switch; multiple nodes including: i) a first node coupling the first switch and the second switch directly in series, and ii) a second node coupling the third switch and the fourth switch directly in series; wherein the secondary winding may be connected between the first node and the second node; and an output node configured to output an output current based on: i) a first output current supplied from the first node through the first switch and ii) a second output current supplied from the second node through the third switch.Additionally, the apparatus discussed herein may be configured to include: a fifth switch and a sixth switch; wherein the first switch may be arranged in series between the fifth switch and the second switch; and wherein the third switch may be arranged in series between the sixth switch and the fourth switch.Additionally, the apparatus discussed herein may be configured to include: a first circuit path extending between the fifth switch and the first node, the first circuit path including a first capacitor disposed in series with a first primary winding of the auto-transformer; and a second circuit path extending between the sixth switch and the second node, the second circuit path including a second capacitor disposed in series with a second primary winding of the auto-transformer.Additionally, the apparatus discussed herein may be configured to include a controller configured to, for a first portion of a control cycle, i) enable the first switch to an ON state, ii) disable the third switch to an OFF state, and iii) enable the fourth switch to directly couple the second node to a reference voltage; and for a second portion of a control cycle, i) enable the third switch to an ON state, ii) disable the first switch to an OFF state, and iii) enable the second switch to directly couple the first node to the reference voltage.According to another example, the controller may be configured to, for the first portion of the control cycle, i) enable the sixth switch to an ON state, ii) disable both the second switch and the fifth switch to an OFF state; and for the second portion of the control cycle, i) enable the fifth switch to an ON state, ii) disable both the fourth switch and the sixth switch to an OFF state.It is further noted that this disclosure also includes a method of manufacturing the power converter as discussed above. The method includes a manufacturer resource incorporating an auto-transformer having multiple windings. The producer resource manufactures the power converter to include the auto-transformer. In addition, the producer resource produces the power converter to have first switches and second switches. The first switches are operable to control switching of circuit paths including the plurality of windings; the second switches are operable to transfer an output current from the auto-transformer to an output node to power a load. It should be appreciated that other possible method operations are discussed herein.Accordingly, implementations as discussed herein are useful over conventional techniques. For example, unlike conventional techniques, the novel power converter provides efficient conversion of an input voltage to a corresponding output voltage. Such examples as discussed herein provide less energy loss during generation of a corresponding output voltage.These and other more specific examples are disclosed in more detail below.It should be appreciated that any of the resources as discussed herein may include one or more computerized devices, devices, hardware, etc., that perform and / or support any or all of the method operations disclosed herein. In other words, one or more computerized devices or processors may be programmed and / or configured to operate as discussed herein to perform the various examples as described herein.Still other examples herein include software programs to perform the steps and / or operations summarized above and disclosed in detail below. One such example includes a computer program product including a non-transitory computer readable storage medium (i.e., any computer readable hardware storage medium) having encoded thereon software instructions for subsequent execution. The instructions, when executed in a computer-based device (hardware) having a processor, program and / or cause the processor (hardware) to perform the operations disclosed herein. Such arrangements are typically provided as software, code, instructions, and / or other data (e.g., data structures) residing on or encoded on a non-transitory computer readable storage medium such as an optical medium (e.g., CD-ROM), a floppy disk, a hard disk, a memory stick, a storage device, etc., or other medium such as firmware in one or more ROM, RAM, PROM, etc., or as an application specific integrated circuit (ASIC), etc. The software or firmware, or other such configurations, may be installed on a computerized device to cause the computerized device to perform the techniques discussed herein.Accordingly, examples herein are directed to a method, system, computer program product, etc. that supports operations as discussed herein.An example includes a computer readable storage medium and / or system having instructions stored thereon to facilitate generation of an output voltage to power a load. The instructions, when executed by computer processor hardware, cause the computer processor hardware (such as one or more co-located or remote processor devices or hardware) to control operation of the power converter and corresponding switches to convert a corresponding input voltage to an output voltage power load.The order of the above steps has been added for clarity. It should be appreciated that any of the processing steps discussed herein may be performed in any suitable order.Other examples of the present disclosure include software programs and / or corresponding hardware to perform any of the example steps and operations of the method summarized above and disclosed in detail below.It should be understood that the system, method, apparatus, instructions on computer readable storage media, etc., discussed herein may also be embodied in strict terms as a software program, firmware, a hybrid of software, hardware, and / or firmware, or as hardware alone, such as within a processor (hardware or software), or within an operating system, or within a software application.It is further noted that although the examples discussed herein are applicable to controlling the operation of a switched capacitor converter, the concepts disclosed herein may be advantageously applied to any other suitable voltage converter topologies.Additionally, it should be appreciated that although each of the various features, techniques, configurations, etc. may be discussed herein at various locations of this disclosure, where appropriate, each of the concepts may optionally be carried out independently of each other or in combination with each other. Accordingly, the one or more present inventions as described herein may be embodied and considered in many different ways.It should also be noted that this preliminary discussion of the examples herein intentionally does not indicate every example and / or incrementally novel aspect of the present disclosure or claimed invention(s). Rather, this brief description is merely illustrative of general examples and corresponding points of novelty over conventional techniques. For additional details and / or possible perspectives (permutations) of the invention(s), the reader is directed to the Detailed Description section (which is a summary of examples) and corresponding figures of the present disclosure, as further discussed below. FIG. 1 is an exemplary diagram illustrating a power supply including a switched capacitor converter and an auto-transformer as discussed herein. FIG. 2 is an exemplary more detailed diagram illustrating a power converter as discussed herein. FIG. 3 is an example timing diagram for controlling the power converter as discussed herein. FIG. 4 is an exemplary diagram of an auto-transformer implemented in a power converter as described herein. FIG. 5 is an exemplary diagram of an auto-transformer implemented in a power converter as discussed herein. FIG. 6 is an example timing diagram illustrating a switching frequency and duty cycle of start-up pulse width modulation as discussed herein. FIG. 7 is an exemplary diagram illustrating a switched capacitor converter with a full bridge rectifier as discussed herein. FIG. 8 is an example timing diagram for controlling the power converter and corresponding signals as discussed herein. FIG. 9 is an example diagram illustrating operation of the power converter in a first time period as discussed herein. FIG. 10 is an example diagram illustrating operation of the power converter in a second period of time as discussed herein. FIG. 11 is an example diagram illustrating operation of the power converter in a third period of time as discussed herein. FIG. 12 is an example diagram illustrating a computer architecture operable to perform one or more operations according to examples herein. FIG. 13 is an example diagram illustrating a general method according to examples herein.The above and other objects, features and advantages of the present examples will become apparent from the following more particular description herein, as illustrated in the accompanying drawings, in which like reference numerals refer to the same parts throughout the several views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the examples, principles, concepts, etc.According to an example, as discussed further herein, an apparatus such as a power converter includes an auto-transformer, first switches, and second switches. The auto-transformer comprises a plurality of windings. The first switches control switching of circuit paths including the plurality of windings of the auto-transformer. The second switches control the transfer of the output current from the plurality of windings of the auto-transformer to an output node to supply a load.Turning now more specifically to FIG. 1, an example diagram illustrating a power supply including a switched capacitor converter as discussed herein is shown.As shown in this example, the power supply 100 (such as a device, an electronic device, etc.) includes a controller 140 and a power converter 135. The power converter 135 includes a primary stage 101, an auto-transformer 160, and a secondary stage 102.The primary stage 101 includes switches 125. The secondary stage 102 includes the second switches 126.The auto-transformer 160 includes a plurality of primary windings and at least one secondary winding. For example, the auto-transformer 160 includes the primary winding 161- 1 and the primary winding 161- 2. The auto-transformer 160 also includes the secondary winding 162.It should be appreciated that the multi-tap auto-transformer 160 is shown as a non-limiting example and may be instantiated as any suitable device, such as a transformer, a transformer device, a transformer device, etc.It is further noted that each of the resources as described herein may be instantiated in any suitable manner. For example, the controller 140, the power converter 135, the multi-tap auto-transformer 160, etc. may each be instantiated as or include hardware (such as a circuit), software (executable instructions), or a combination of hardware and software resources.Note that the controller 140 and corresponding operations may be implemented as controller software, controller hardware, or a combination of controller software and controller hardware.During operation, the controller 140 generates control signals 105 (such as one or more pulse width modulation signals) that control states of a respective control of switches 125 and switches 126 in the power converter 135.As further shown, power converter 135, such as a switched capacitor converter, receives input voltage 121 (Vin, such as a DC input voltage) provided by input voltage source 120. As discussed above, the multi-tap auto-transformer 160 includes a first primary winding 161- 1 and a second primary winding 161- 2. In one example, the primary windings 161 are at least inductively coupled to the secondary winding 162 and to each other. According to further examples, the primary windings 161 are connected in series with the secondary windings 162.As discussed further herein, the controller 140 of the power supply 100 controllably switches multiple capacitors and corresponding resonant circuit paths including the primary windings of the multi-tap auto-transformer 160 (such as a matrix multi-tap auto-transformer or other suitable type of component) to transfer energy from the input voltage (Vin) through the primary winding 161 to the secondary winding 162 to generate the output voltage 123 and a corresponding output current 122 to power the load 118.Accordingly, an apparatus such as a power converter 135 as described herein may be configured to include an auto-transformer 160, first switches 125, and second switches 126. The auto-transformer 160 includes multiple windings, such as the series connection of the primary winding 161- 1, the secondary winding 162, and the primary winding 161- 2. The first switches 125 may be configured to control switching of circuit paths including the plurality of windings such as the primary winding 161- 1 and the primary winding 161- 2 of the auto-transformer 160. The second switches 126 may be configured to control transmission of the output voltage 123 and the corresponding output current 122 from the one or more windings of the auto-transformer 160 to an output node N 23 to power a load 118.As discussed above, the plurality of windings of the auto-transformer 160 may be configured to include a first primary winding 161- 1, a second primary winding 161- 2, and a secondary winding 162. Each of the plurality of windings (such as primary winding 161- 1, secondary winding 162, and primary winding 161- 2) in the auto-transformer are magnetically (inductively) coupled together. As further shown in this example, the secondary winding 162 is arranged in series between the first primary winding 161- 1 and the second primary winding 161- 2. For example, primary winding 161- 1 is connected between node N 41 and node N 51; secondary winding 162 is connected between node N 51 and node N 52; primary winding 161- 2 is connected between node N 52 and node N 42.The secondary winding 162 may be a single secondary winding of the auto-transformer 162 arranged in series between the first primary winding 161- 1 and the second primary winding 161- 2. Each of the windings in the transformer 160 may be one or more windings arranged in parallel.FIG. 2 is an example diagram illustrating a switched capacitor converter according to examples included herein.As shown, in this example, the power supply 100 includes an input voltage source 120 that provides, for example, an input voltage 121 (Vin) to the node N 1 of the power converter 135.Power converter 135 (device such as hardware, circuitry, etc.) includes multiple switches Q 1, Q 2, Q 3, Q 4, Q 5, Q 6, Q 7, and Q 8 (such as field effect transistors or any other suitable type of switch) to control transmission of current. In addition, the power converter 135 includes a plurality of circuit components including a capacitor Cres 1 and a capacitor Cres 2.As further shown, power converter 135 includes a first resonant circuit path having a series connection of capacitor Cres 1 and primary winding 161- 1 connected in series between node N 11 and node N 51. In addition, the power converter 135 includes a second resonant circuit path having a series circuit of the capacitor Cres 2 and the primary winding 161- 2 connected in series between the node N 12 and the node N 52.Further, in this example, the windings in the multi-tap auto-transformer 160 may comprise any number of turns. For example, the auto-transformer 160 may be configured to include the primary winding 161- 1 (such as N1turns), the primary winding 161- 2 (such as N1turns), and the secondary winding 162 (such as N2turns). It should be noted that the number of windings (N 1, N 2, etc.) associated with the primary windings 161 and / or the secondary winding 162 may be any suitable value and may vary depending on the example.As further shown, switches Q 1, Q 2, Q 3, and Q 4 are connected in series between node N 1 (such as the node of power supply 120 that provides input voltage 121) and node N 2 (such as a ground reference potential).Further, in this example, the drain node (D) of the switch Q1 and the drain node (D) of the switch Q5 are connected to the input voltage source Vin for the node N1. Further, the source node (S) of the switch Q 1 is coupled to the drain node (D) of the switch Q 2 (node N 11). The source node (S) of switch Q2 is coupled to the drain node (D) of switch Q3 (at node N21). The source node (S) of the switch Q 3 is coupled to the drain node (D) of the switch Q 4 (at the node N 31 that is the same as the node PH 1). Finally, the source node of switch Q4 is connected to node N2.The capacitor Cres 1 is connected between the node N 11 and a respective node N 41 of the primary winding 161- 1. Capacitor Cres2 is connected between node N12 and a respective node N42 of primary winding 161-2.The settings of the capacitors Cres 1 and Cres 2 may be any suitable capacitance value. In one example, the power converter 135 as described herein provides better performance when the capacitance of Cres1=the capacitance of Cres2, where the power converter 135 also works well even when the capacitance of Cres1≠the capacitance of Cres2.It is further noted that the proposed hybrid switched capacitor converter (such as full bridge rectifier (FB-HSC) power converter 135) may be configured to include an interleaved (interleaved) flying capacitor (flying capacitor) structure connected to a multi-tap auto-transformer (MTA) for a full bridge rectifier, as shown in FIG. 2. Zero voltage switching (ZVS) for all switches Q1-Q8 may be enabled by the magnetizing inductance of the auto-transformer 160. Capacitor CRES1 is a first flying capacitor; capacitor CRES2 is a second flying capacitor.The switches Q 1-Q 8 may be divided into two switch groups: the first switch group is formed by Q 1, Q 3, Q 6, and Q 8 (control logic and control signal S 1), and the second switch group (Q 2, Q 4, Q 5, and Q 7) is controlled by 180° out-of-phase PWM (control logic and control signal S 2) with respect to the first group and has the same duty cycle. The power converter 135 may be configured to operate with a fixed duty cycle, such as about 50%, or any other suitable value, to obtain the minimum effective current.The magnitude of the output voltage 123 depends on the multi-tap auto-transformer turns ratio (N 1 / N 2). The value N 1 represents a number of windings around each of the primary winding 161- 1 in the primary winding 161- 2. The value N2represents a number of windings around the secondary winding 162. The relationship between input voltage V in(121) and output voltage V out(123) is given by the following equation:In one example, the proposed FB HSC, such as power converter 135, may itself be scalable to different conversion ratios by only shaping the ratio between N 1 and N 2 which actually results in a new family of uncontrolled hybrid DC-DC converters being claimed with different ratio (i.e., 3 to 1, 4 to 1, 5 to 1, 6 to 1,...).In one example, the main characteristic of the proposed solution, such as the power converter 135, is to use the leakage inductance of the multi-tap auto-transformer 160 to soft-charge the resonant capacitor CRES 1 and the resonant capacitor CRES 2, which actually function as flying capacitors, allowing the use of lower voltage switches (such as MOSFETs) on the primary side compared to, for example, a classical LLC (resonant power converter) topology. In this example of the power converter 135, the switches Q 1, Q 2, Q 5, and Q 6 disable a portion of the input voltage V in- V out.Due to the full bridge rectifier, the actual rectifier switches (Q 3, Q 4, Q 7 and Q 8) must block the output voltage V out. This is advantageous because "ultra" low voltage FETs (such as the maximum voltage across the drain and source) can already be used in a 6:1 implementation (i.e., 15V device).Another advantage of the power converter 135 as discussed herein is its symmetric behavior, resulting in a reduction in input voltage ripple.A high efficiency and high power density conditioner of the proposed FB-HSC (power converter 135) is the ability to use lower rated voltage MOSFETs (such as field effect transistor devices with a lower maximum rated voltage across the respective drain node of the source node) and the ability to implement class II ceramic capacitors, such as for CRES1 and CRES2, which inherently provide a high capacitance density. Moreover, the magnetizing inductance of the auto-transformer 160 provides the inductive energy to ensure a ZVS transition for all switches such as field effect transistors (MOSFETs).Thus, according to the circuit as shown in FIG. 2, the power converter 135 includes the switch Q 1 arranged between an input voltage source 120 and a first circuit path, such as the series circuit path including the capacitor Cres 1 and the primary winding 161- 1 of the auto-transformer 161. Power converter 135 further includes switch Q 5 disposed between an input voltage source 120 (node N 1) and a second circuit path, such as the series circuit path including capacitor Cres 2 and primary winding 161- 2 of auto-transformer 161.As discussed above, primary winding 161- 1, secondary winding 162, and primary winding 161- 2 are magnetically coupled together. In such a case, therefore, the secondary winding 162 is magnetically coupled to both the first primary winding 161- 1 and the second primary winding 161- 2.In addition, the first resonant circuit path, which includes approximately capacitor Cres 1 and primary winding 161- 1, extends between switch Q 1 (and corresponding node N 11) and node N 51 of secondary winding 162 associated with auto-transformer 160; the second resonant circuit path, which includes approximately capacitor Cres 2 and primary winding 161- 2, extends between switch Q 2 (and corresponding node N 12) and node N 52 of secondary winding 162 associated with auto-transformer 160.In this example, the first switches 125 include switches Q 1, Q 2, Q 5, and Q 6. The second switches 126 include switches Q 3, Q 4, Q 7, and Q 8.The combination of the switch Q 1, the first resonant circuit path (such as the capacitor Cres 1 and the primary winding 161- 1), and the switch Q 4 is disposed between the node N 1 and the input voltage source 120 and the ground reference node N 2. The combination of the switch Q 5, the second resonant circuit path (such as the capacitor Cres 2 and the primary winding 161- 2), and the switch Q 8 is disposed between the node N 1 and the input voltage source 120 and the ground reference node N 2.As further shown, the controller generates the control signal 105- 1. The control signal 105- 1 is given to respective gate nodes of the switch Q 1, the switch Q 3, the switch Q 6, and the switch Q 8. For example, the controller 140 supplies the control signal 105- 1 (S 1) to the gate node of the switch Q 1, the gate node of the switch Q 3, the gate node of the switch Q 6, and the gate node of the switch Q 8.The controller 140 generates the control signal 105- 2. The control signal 105- 2 is given to each of the gate nodes associated with the switch Q 2, the switch Q 4, the switch Q 5, and the switch Q 7. For example, the controller 140 supplies the control signal 105- 2 (S 2) to the gate node of the switch Q 2, the gate node of the switch Q 4, the gate node of the switch Q 5, and the gate node of the switch Q 7.FIG. 3 is an example timing diagram for controlling the power converter as discussed herein.Generally, as shown in diagram 300, controller 140 generates control signal 105- 2 (signal S 2) to be an inversion of control signal 105- 1 (signal S 1). A pulse width of each control signal is approximately 49% or another suitable pulse width modulation value.Between time T0 and time T1, when control signal 105-1 (at a logic high) controls set of switches Q1, Q3, Q6, and Q8 to an ON state (low impedance or short circuit between the respective drain and source nodes), control signal 105-2 (logic low) controls set of switches Q2, Q4, Q5, and Q7 to an OFF state (very high impedance or open circuit between the respective drain and source nodes).Conversely, between time T 2 and time T 3, when control signal 105- 2 (logic high) controls set of switches Q 2, Q 4, Q 5, and Q 7 to an ON state, control signal 105- 1 (logic low) controls set of switches Q 1, Q 3, Q 6, and Q 8 to an OFF state.Note that the duration between time T 1 and time T 2, the duration between time T 3 and time T 4, the duration between T 5 and T 6, etc., represent so-called dead times during which each of the switches (Q 1-Q 8) in the power converter 135 is deactivated to the OFF state.As further shown, the control signals 105 are cyclic. For example, the settings of the control signals 105 (control signal 105- 1 and control signal 105- 2) for subsequent cycles are the same as those for the cycle between time T 0 and time T 4. More specifically, the settings of the control signals 105 generated by the controller 140 between time T 3 and time T 7 are the same as the settings of the control signals 105 between time T 0 and time T 3, and so forth.In one example, the power converter 135 may be configured to operate in an uncontrolled manner.In another example, the controller 110 controls the frequency of the control signals (period is the time between T 0 and the time T 4) to be generated at any suitable frequency.Additionally, as previously mentioned, the controller 140 controls the pulse duration of the control signals 105 to be approximately 49% depending on the dead time duration, although the control signals 105 may be generated with any suitable pulse width modulation value.An amount of the output voltage 123 depends on the turns ratio (N 1 / N 2) of the multi-tap auto-transformer 160.Further, in this example, the controller 140 generates the respective control signals 105 in each of the plurality of control cycles to convert the input voltage to the output voltage. This includes, via the controller 140, for a first portion of a respective control cycle of multiple control cycles, such as between time T 0 and time T 1, i) to activate the switch Q 1, wherein activation of the switch Q 1 transfers an input voltage 121 obtained from the input voltage source 120 through the switch Q 1 to the first resonant circuit path including the capacitor Cres 1 and the primary winding 161- 1; and ii) to deactivate the switch Q 5, wherein deactivation of the switch Q 5 prevents transfer of the input voltage through the switch Q 2 to the second resonant circuit path including the capacitor Cres 2 and the primary winding 161- 2.Techniques herein further include, via the controller 140 (see also FIG. 9 ), for a second portion of the respective control cycle of multiple control cycles, such as between time T 2 and time T 3, i) disabling the switch Q 1, wherein disabling the switch Q 1 inhibits transmission of the input voltage 121 through the switch Q 1 to the first resonant circuit path, and ii) enabling the switch Q 5, wherein enabling the switch Q 5 transmits the input voltage 121 through the switch Q 5 of the second resonant circuit path.Additionally, for the first portion of the control cycle of FIG. 9, such as between time T 0 and time T 1, the controller 140 (see also FIGS. 9 and 11 ) may be configured to deactivate the switch Q 2 and activate the switch Q 6, wherein activation of the switch Q 6 transfers the output current iout 2 from the node N 42 of the transformer 160 (and the second resonant circuit path including the winding 161- 2 and the capacitor Cres 2) through the switch Q 6 to the output node N 23; ii) for the second portion of the control cycle of FIG. 11, such as between time T 2 and time T 3, to deactivate switch Q 6 and activate switch Q 2, wherein activation of switch Q 2 causes second output current iout 1 to be transmitted from node N 41 of transformer 160 (and the first resonant circuit path including winding 161- 1 and capacitor Cres 1) through switch Q 2 to output node N 23.FIG. 4 is an exemplary diagram of an auto-transformer implemented in a power converter as described herein.As shown in FIG. 4, the multi-tap auto-transformer 160 may be configured to include multiple windings such as the primary winding 161- 1, the primary winding 161- 2, and the secondary winding 162.In this example, the windings of the transformer 160 are wound on a magnetic core. The windings may be divided into two winding categories, such as a first category having primary winding 161- 1 and primary winding 161- 2, and the second category having secondary winding 162.Considering the known conventions of the transformer, the "input winding" is considered primary side windings while the "output winding" is considered secondary windings. Based on this assumption, and considering an ideal multi-tap auto-transformer for a full bridge rectifier, and considering that the magneto motif force (MMF) is generated by the current Isecthrough the secondary-side and corresponding secondary winding 162, it should be considered counted by an MMFin the primary winding generated by Iin1(such as the current through the primary winding 161- 1) and Iin2(such as the current through the secondary winding 161- 2). In this scenario, the following equation is valid: where N1 is equal to the number of turns of the primary windings 161, and N2 is the number of turns of the secondary winding 162.To further increase the performance of the proposed power converter described herein, an alternative instance of the auto-transformer 160 may be implemented via the matrix concept illustrated in FIG. 5. It should be noted that the matrix version shown in FIG. 5 represents the same equivalent electrical circuit shown in FIG. 4, except with different equivalent transformer ratios.FIG. 5 is an exemplary diagram of an auto-transformer implemented in any power converter as discussed herein.The auto-transformer shown in FIG. 5 is a drop-in substitute for the auto-transformer 160 in the power converter 135.Considering the actual conversion ratio of Equation 1 and the matrix MTA reported in FIG. 5 for full bridge rectifier version, the ratio between input and output voltage V_in (121) and output voltage V_out (123) is given by the following equation:In addition, when an array of matrix multi-tap auto-transformers is used for a full bridge rectifier, n1x windings may be arranged in series and n2x windings may be arranged in parallel. Taking M as the number of windings connected in series for the input windings n 1 x) and in parallel for the output windings n 2 x, the following equation provides the actual ratio between input voltage V_in and output voltage V_out:The matrix version of the transformer 160 helps take advantage of the horizontal direction of the substrate in which the windings are placed, rather than the vertical direction (i.e., increase in cost due to the layer amount).FIG. 6 is an example timing diagram illustrating a switching frequency and duty cycle of pulse width modulation at startup, as discussed herein.When a voltage is applied to the input of the power converter 135, the system is in a state of charge and the value of the actual inrush current into the converter 135 via the input voltage 121 depends on the impedance of the converter, which mainly has a capacitive behavior.As shown in the timing diagram of diagram 600, it is noted that inrush current, such as current applied to node N 1 at startup of power converter 135, may exceed the current capability of the components and the printed circuit board (PCB) traces of the power converter, resulting in damage to one or more of these components. This problem can be solved and avoided by reducing the voltage rise time at the input (such as the input voltage 121) of the power converter 135 during the startup operation thereof.Two different solutions can be adopted, such as: 1) voltage regulation at the input (with a buck converter) or 2) with a load switch. In either case, the amount of input voltage 121 provided to power converter 135 is ramped up at a desired speed.The two mentioned solutions may help manage the inrush current from the input voltage source 120 to the node N 1 of the power converter 135, however, managing the inrush current may result in an increase in the cost of the power supply, as additional components may be required to implement such input voltage ramping. One way to boost the amount of input voltage 121 provided to power converter 135 essentially includes that SR MOSFETs may be clamped by the output voltage value while TOP FETs (such as switches Q 1, Q 2, Q 5, Q 6) are exposed to some or all of the input voltage during rated operation (i.e., a similar TOP MOSFET class voltage with and without an e-fuse).The signal 610 in the diagram 600 indicates a respective switching frequency of controlling the switches in the power converter 135 during startup (such as between time T 61 and time T 66). The signal 620 in the diagram 600 indicates a respective duty cycle of controlling the switches in the power converter 135 during startup (such as between time T 61 and time T 66).FIG. 7 is an exemplary diagram illustrating a switched capacitor converter with a full bridge rectifier as discussed herein.In this exemplary configuration of the power converter 135, FIG. 7 illustrates the function of a respective zero voltage switching inductance Lzvs associated with the secondary winding 162.FIG. 8 is an example timing diagram for controlling the power converter as discussed herein.In this example, as shown in diagram 800 and as discussed above, controller 140 generates respective control signal S 1 ( 105- 1) as well as control signal S 2 ( 105- 2) to control the respective switches in power converter 135.The signal Icres 1 represents a current through the series connection of the capacitor Cres 1 and the primary winding 161- 1 (first resonant circuit path); Icres 2 represents a current through the series connection of the capacitor Cres 2 and the primary winding 161- 2 (second resonant circuit path).Izvsrepresents a current through the inductance Lzvsassociated with the secondary winding 162.Signal Iout1 (also referred to as Is1) represents a current supplied from node and 21 to output node 123; signal Iout2 (also referred to as Is2) represents a current supplied from node and 22 to output node 123.Iout (summation of current Ioutl and current Iout2) represents the total output current (Iout) provided from node N23 to load 118.Between time T 0 and time T 1, when the resonant circuit path including capacitor Cres 1 and primary winding 161- 1 is coupled to the input voltage via activation of switch Q 1, the corresponding activated switch Q 3 provides output current Iout 1 (a majority of output current Iout) to generate current Iout. Conversely, between time T 2 and time T 3, when the resonant circuit path including capacitor Cres 2 and primary winding 161- 2 is coupled to the input voltage via activation of switch Q 5, the corresponding activated switch Q 7 provides output current Iout 2 (a majority of output current Iout) to generate current Iout.FIG. 9 is an example diagram illustrating operation of the power converter in a first time duration (such as between time T 0 and time T 1) as discussed herein.As discussed above, the controller 140 activates the switches Q 1, Q 3, Q 6, Q 8 between time T 0 and time T 1. In one example, switches Q1, Q3, Q6, and Q8 are turned on with zero voltage switching (ZVS) and zero current switching (ZCS) during which one resonant current is present between capacitor CRES1 and the leakage inductance of the auto-transformer 160 while another resonant current is present between capacitor CRES2 and the leakage inductance of the auto-transformer 160. In this phase, such as between time T0 and time T1, capacitor CRES1 is charged soft by input voltage source V in( such as via voltage 121), while capacitor CRES2 is discharged soft.When the capacitance of the capacitor CRES 1 is equal to a capacitance of the capacitor CRES 2, the effective current (RMS current) through each of the capacitors is substantially equal. Considering a substantial balance of the amounts of current between the resonant currents flowing through the capacitor CRES 1 and the capacitor CRES 2, the following equation holds:Icres1(t)=-Icres2(t) and taking Icres1(t)=Ires(t) into account, the two output currents can be written:Therefore, the total output current is:This equation represents the current multiplication factor of the power converter 135 because the input current is always equal to i res the input current is multiplied by M, and the input voltage is stepped down by M:FIG. 10 is an example diagram illustrating operation of the power converter in the second time duration (such as between time T 1 and time T 2, and between time T 3 and T 4) corresponding to a dead time as discussed herein.For the period between time T 1 and time T 2, the controller 140 disables the switches Q 1, Q 3, Q 6, Q 8 in addition to disabling the switches Q 2, Q 4, Q 5, Q 7. During such time, the energy stored in the parasitic capacitances associated with switches Q2, Q4, Q5, and Q7 is discharged to zero using the inductive energy stored in the L zvs- inductance at t = t 1. When the energy stored in the capacitances associated with the switches Q 2, Q 4, Q 5, Q 7 is discharged to zero, the respective body diodes associated with the switches begin to conduct to thereafter enable ZVS turn-on. The topological state of the switches is shown in Fig. 10. The current i Lzvs( t 1), which enables ZVS operation, is referred to as i Lzvs,pk as shown in FIG. 8, which is given by the following equation:For the period between time T 3 and time T 4, the controller 140 deactivates the switches Q 2, Q 4, Q 5, and Q 7 in addition to deactivating the switches Q 1, Q 3, Q 6, and Q 8. During such time, the energy stored in the parasitic capacitances associated with switches Q1, Q3, Q6 and Q8 is discharged to zero using the inductive energy stored in the L zvs- inductance at t = t 3. When the energy stored in the capacitances associated with the switches Q 1, Q 3, Q 6, and Q 8 is discharged to zero, the respective body diodes start conducting to thereafter enable ZVS turn-on. The current i Lzvs( t 3), which enables ZVS operation, is - i Lzvs,pk.FIG. 11 is an example diagram illustrating operation of the power converter and a third time duration (such as between time T 2 and time T 3) as discussed herein.As discussed above, between time T 2 and time T 3, the controller activates switches Q 2, Q 4, Q 5, Q 7 to an ON state at ZVS and zero current switching (ZCS). One resonant current is present (flowing) between capacitor CRES1 and the leakage inductance of multi-tap auto-transformer 160 while another resonant current is present (flowing) between capacitor CRES2 and the leakage inductance of MTA 160. In this phase, the capacitor CRES2 is charged softly by the input voltage source 120, while the capacitor CRES1 is discharged softly. When the capacitance of the capacitor CRES1 is equal to the capacitance of the capacitor CRES2, the effective current through each of the capacitors is substantially equal. During this balanced current of the resonant currents in C res1 and C res2 it should be noted that:i Cres1( t) = i Cres2( t) t and taking into account i Cres1( t) = i res( t), the two output currents can be written:Therefore, the total output current is:Since the input current is now i Cres2= - i res, the same transformation ratio M previously found is valid.Thus, the second switches 126 associated with the power converter 135 (see FIG. 1 ) may be configured to include the switch Q 3 and the switch Q 7, as well as the switch Q 4 and the switch Q 8. The switch Q 3, such as the corresponding drain node, is coupled to a node N 51 of the secondary winding 162. The switch Q 7, such as the corresponding drain node, is coupled to node N 52 of the secondary winding 162. The second switches 126 discussed herein may further include the switch Q 4 and the switch Q 8. Recall that switch Q4, such as the corresponding drain node, is coupled to node N51 of secondary winding 162. Additionally, recall that switch Q8, such as the corresponding drain node, is coupled to node N52 of secondary winding 162.As discussed above, the output current Ioutfurther includes a summation of the output current Iout1and the output current Iout2. The controller is configured to switch between, i) activation of the switch Q 3 in a first portion of a respective control cycle for transferring the output current iout 1 from the node N 51 of the secondary winding 162 to the output node N 23, and ii) activation of the switch Q 7 in a second portion of the respective control cycle for transferring the output current iout 2 from the node N 52 of the secondary winding 162 to the output node N 23.The controller 140 may be configured to activate i) the first switch Q 8 in the first portion of the respective control cycle, such as between time T 0 and time T 1, with activation of the switch Q 8 connecting the node N 52 of the secondary winding 162 to the ground reference voltage node N 2; ii) activate the switch Q 4 in the second portion of the respective control cycle, such as between time T 2 and time T 3, with activation of the switch Q 4 connecting the node N 51 of the secondary winding 162 to the reference voltage node N 2.In further examples herein, as discussed above, the auto-transformer 160 includes a first primary winding 161- 1 disposed between the node N 41 and the node N 51. In addition, the auto-transformer 160 includes a secondary winding 162 connected between the node N 51 and the node N 52. The auto-transformer 160 includes a second primary winding 161- 2 connected between the node N 52 and the node N 42 of the auto-transformer 160.As discussed above, the combination of the first primary winding 161- 1, the secondary winding 162, and the second primary winding 161- 2 are inductively coupled together.Further, as discussed above, the second switches 126 include the switch Q 3 and the switch Q 4. Via the control signal S 1 applied to the switch Q 3, the controller 140 controls transmission of the first output current Iout 1 from the node N 51 of the auto-transformer 160 through the switch Q 3 to the output node N 23. Via the control signal S 2 applied to the switch Q 7, the controller 140 controls transmission of the second output current Iout 2 from the node N 52 of the auto-transformer 160 through the switch Q 7 to the output node N 23.Specifically, for a first portion of each control cycle, controller 140 activates switch Q 1 to an ON state, ii) switches Q 5 to an OFF state, and iii) switches Q 8 to couple node N 52 of auto-transformer 160 to a ground reference voltage node N 2. For a second portion of each control cycle, controller 140, i) activates switch Q 5 to an ON state, ii) activates switch Q 1 to an OFF state, and iii) activates switch Q 4 to couple node N 51 of auto-transformer 160 to a ground reference voltage node N 2.Accordingly, first switches (such as switch Q 2 and switch Q 6) may be configured to transfer currents Iout 1 and Iout 2 from transformer 160 to output node N 23. The second switches (such as switches Q 3 and Q 7) may be configured to transfer currents Iout 1 and Iout 2 from the transformer 162 to the node N 23.FIG. 12 is an example block diagram of a computer system for implementing any of the operations discussed above in accordance with embodiments herein.Any of the resources (such as controller 140, voltage converter 135, switched capacitor converter 131, etc.) discussed herein may be configured to include computer processor hardware and / or corresponding executable instructions to perform the various operations discussed herein.As shown, the computer system 1000 of the present example includes an interconnect 1011 that provides coupling of computer readable storage media 1012, such as a non-transitory type of media (which may be any suitable type of hardware storage medium in which digital information may be stored and retrieved), a processor 1013 (computer processor hardware), an I / O interface 1014, and a communication interface 1017. Computer readable storage media may be computer readable storage hardware.The computer readable storage medium 1012 may be any hardware storage device such as a memory, an optical memory, a hard disk, a floppy disk, etc. In one embodiment, the computer readable storage medium 1012 stores instructions and / or data.As shown, computer readable storage media 1012 may be encoded with controller application 140- 1 (e.g., including instructions) to perform any of the operations discussed herein.During operation of an embodiment, processor 1013 accesses computer readable storage media 1012 via use of connection 1011 to start, execute, execute, interpret, or otherwise perform the instructions in controller application 140- 1 stored on computer readable storage medium 1012. Execution of the controller application 140- 1 generates the controller process 140- 2 to perform any of the operations and / or processes discussed herein.Those skilled in the art will understand that computer system 1050 may include other processes and / or software and hardware components, such as an operating system that controls the allocation and use of hardware resources to execute controller application 140- 1.According to various embodiments, it is noted that the computer system may be located in any of various types of devices, including, but not limited to, a power supply, a switched capacitor converter, a power converter, a mobile computer, a personal computer system, a wireless device, a wireless access point, a base station, a telephone device, a desktop computer, a laptop computer, a notebook computer, a netbook computer, a mainframe computer system, a handheld computer, a workstation, a network computer, an application server, a storage device, an consumer electronic device such as a camera, a camcorder, a set-top box, a mobile device, a video game console, a handheld video game device, a peripheral device, Such as a switch, modem, router, set-top box, content management device, handheld remote control device, any type of computing or electronic device, etc. Computer system 1050 may be located at any location or may be included in any suitable resource in any networking environment to implement the functionality as discussed herein.The functionality supported by the various resources will now be discussed via a flow diagram in Figure 13. It should be noted that the steps in the flowcharts below may be performed in any suitable order.FIG. 13 is a flow diagram 1300 illustrating an example method according to embodiments herein. Note that there will be some overlap in terms of concepts as discussed above.In processing operation 1310, the controller 140 controls switching of circuit paths via generation of the control signals 105- 1 and 105- 2. The circuit path includes a plurality of windings of an auto-transformer 160.In processing operation 1320, the controller 140 controls second switches. The controller 140 controls the second switches to transfer an output current and a corresponding output voltage from the plurality of windings of the auto-transformer to an output node to power a load.It is again to be appreciated that techniques included herein are well suited for use in power supply applications. It should be appreciated, however, that embodiments herein are not limited to use in such applications, and that the techniques discussed herein are well suited for other applications as well.Although this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present application as defined by the appended claims. Such variations are intended to be covered by the scope of this present application. Thus, the foregoing description of embodiments of the present application is not intended to be limiting. Rather, any limitations on the invention are set forth in the following claims.

Claims

An apparatus comprising: an auto-transformer (160) comprising a plurality of windings (161-1, 161-2, 162); first switches (125) coupled between an input node (N1) and an output node (N23); second switches (126) coupled between a reference potential node (N2) and the output node (N23); wherein the first switches (125) are operable to control switching of circuit paths comprising the plurality of windings (161-1, 161-2, 162) of the auto-transformer (160); and wherein the second switches (126) are operable to transfer currents from the plurality of windings (161-1, 161-2, 162) of the auto-transformer (160) through the second switches (126) to the output node (N23).The apparatus of claim 1, wherein the second switches (126) comprise a first pair of series-arranged switches (Q3, Q4) and a second pair of series-arranged switches (Q7, Q8); wherein the first pair of switches (Q3, Q4) is arranged in series between the reference potential node (N2) and the output node (N23); and wherein the second pair of switches (Q7, Q8) is arranged in series between the reference potential (N2) and the output node (N23).The apparatus of claim 2, wherein the currents comprise a first current (iout1) and a second current (iout2); wherein the first pair of switches (Q3, Q4) is operable to control transferring of the first current (iout1) from the plurality of windings of the auto-transformer (160) to the output node (N23); and wherein the second pair of switches is operable to control transferring of the second current (iout2) from the plurality of windings of the auto-transformer (160) to the output node (123).The apparatus of claim 1, wherein the input node (N1) provides an input voltage (121) to the first switches (125); wherein the first switches (125) comprise a first switch (Q1) and a second switch (Q5); wherein the first switch (Q1) is disposed between the input node (N1) and a first circuit path, the first circuit path having a first primary winding (161-1) of the auto-transformer (160); wherein the second switch (Q5) is disposed between the input node (N1) and a second circuit path having a second primary winding (161-2) of the auto-transformer (160), the second primary winding (161-2) being magnetically coupled to the first primary winding (161-1); wherein the auto-transformer (160) has a secondary winding (162) magnetically coupled to both the first primary winding (161-1) and the second primary winding (161-2); wherein the first circuit path extends between the first switch (Q1) and a first node of the secondary winding (162) of the auto-transformer (160); wherein the second circuit path extends between the second switch (Q5) and a second node of the secondary winding (162) of the auto-transformer (160), wherein the second switches include a third switch (Q3) and a fourth switch (Q7); wherein the third switch (Q3) is coupled between the first node of the secondary winding (162) and the output node (N23), wherein the third switch is operable to control conduction of a first current (iout1) of the currents from the first node of the secondary winding (162) to the output node (N23); and wherein the fourth switch (Q7) is coupled between the second node of the secondary winding (162) and the output node (N23), wherein the fourth switch (Q7) is operable to control conduction of a second current (iout2) of the currents from the second node of the secondary winding (162) to the output node (N23).The apparatus of claim 4, further comprising: a controller operable to, for a first portion of a respective control cycle of a plurality of control cycles, i) activate the first switch (Q1), wherein activation of the first switch (Q1) causes the input voltage (121) to be transmitted from the input node (N1) through the first switch (Q1) to the first circuit path, and ii) deactivate the second switch (Q5), wherein deactivation of the second switch (Q5) causes the input voltage (121) to be prevented from being transmitted through the second switch (Q5) to the second circuit path; and for a second portion of the respective control cycle of a plurality of control cycles, i) to deactivate the first switch (Q1), wherein deactivation of the first switch causes preventing the input voltage (121) from being transmitted through the first switch (Q1) to the first circuit path, and ii) to activate the second switch (Q5), wherein activation of the second switch (Q5) causes the input voltage (121) to be transmitted from the input node (N1) through the second switch (Q5) to the second circuit path.The apparatus of claim 5, wherein the first switches (125) further comprise a fifth switch (Q2) and a sixth switch (Q6); wherein the fifth switch (Q2) is coupled to the first circuit path and the first switch (Q1); and wherein the sixth switch (Q6) is coupled to the second circuit path and the second switch (Q5).The apparatus of claim 6, wherein the controller (110, 140) is further operable to deactivate the fifth switch (Q2) and activate the sixth switch (Q6) for the first portion of the control cycle, wherein activation of the sixth switch (Q6) causes the second current (iout2) to be transferred from the second circuit path through the sixth switch (Q6) to the output node (N23); and deactivate the sixth switch (Q6) and activate the fifth switch (Q2) for the second portion of the control cycle, wherein activation of the fifth switch (Q2) causes the first current (iout1) to be transferred from the first circuit path through the fifth switch (Q2) to the output node (N23).The apparatus of claim 1, wherein the plurality of windings of the auto-transformer (160) include a plurality of primary windings (161-1, 161-2) and a secondary winding (162); wherein the second switches (126) include a first switch (Q3) and a second switch (Q7), the first switch (Q3) being directly coupled to a first node of the secondary winding (162), the second switch (Q7) being directly coupled to a second node of the secondary winding (162); wherein the currents comprise a first current (iout1) and a second current (iout2), the apparatus further comprising: a controller (140) operable to switch between i) in a first portion of a respective control cycle, activation of the first switch (Q3) for transferring the first current (iout1) from the first node of the secondary winding (162) through the first switch (Q3) to the output node (N23), and ii) in a second portion of the respective control cycle, activation of the second switch (Q7) for transferring the second current (iout2) from the second node of the secondary winding (162) through the second switch (Q7) to the output node (N23).The apparatus of claim 8, wherein the second switches (126) further comprise a third switch (Q4) and a fourth switch (Q8); wherein the third switch (Q4) is directly coupled to the first node of the secondary winding (162), wherein the third switch (Q4) is directly coupled to the first switch (Q3) and is disposed in series with the first switch (Q3); and wherein the fourth switch (Q8) is directly coupled to the second node of the secondary winding (162), wherein the fourth switch (Q8) is directly coupled to the second switch (Q7) and is disposed in series with the second switch (Q7).The apparatus of claim 9, wherein the controller (110, 140) is further operable to activate i) the fourth switch (Q8) in the first portion of the respective control cycle, wherein activation of the fourth switch (Q8) causes connection of the second node of the secondary winding (162) to the reference potential node (N2); and ii) activate the third switch (Q4) in the second portion of the respective control cycle, wherein activation of the third switch (Q4) causes connection of the first node of the secondary winding (162) to the reference potential node (N2).The apparatus of claim 1, further comprising: a plurality of capacitors including a first capacitor (CRES1) and a second capacitor (CRES2); wherein the circuit paths include a first resonant circuit path and a second resonant circuit path, wherein the first resonant circuit path includes the first capacitor (CRES1) and a first primary winding (161-1) of the auto-transformer (160) arranged in series, wherein the second resonant circuit path includes the second capacitor (CRES2) and a second primary winding (161-2) of the auto-transformer (160) arranged in series; wherein the auto-transformer (160) comprises a secondary winding (162), the secondary winding (162) comprising a first node and a second node, the first node coupling the first primary winding (161-1) directly to the secondary winding (162), the second node coupling the second primary winding (161-2) directly to the secondary winding (162); and wherein the second switches (126) comprise a first switch (Q3) and a second switch (Q7), the first switch (Q3) being coupled between the first node of the secondary winding (162) and the output node (N23), the second switch (Q7) being coupled between the second node of the secondary winding (162) and the output node (N23).The apparatus of claim 1, wherein the auto-transformer (160) is a matrix multi-tap auto-transformer (160).The apparatus of claim 1, wherein the auto-transformer (160) has a first primary winding (161-1) connected between a first node (N41) and a second node (N51) of the auto-transformer (160); wherein the auto-transformer (160) has a secondary winding (162) connected between the second node (N51) and a third node (N52) of the auto-transformer (160); wherein the auto-transformer (160) has a second primary winding (161-2) connected between the third node (N52) and a fourth node (N42) of the auto-transformer (160); wherein the second switches (126) have a first switch (Q3) and a second switch (Q7); wherein the currents comprise a first current (iout1) and a second current (iout2); wherein the first switch (Q3) is operable to control conduction of the first current (iout1) from the second node (51) of the auto-transformer (160) through the first switch (Q3) to the output node (N23); and wherein the second switch (Q7) is operable to control conduction of the second current (iout2) from the third node (N52) of the auto-transformer (160) through the second switch (Q7) to the output node (N23).The apparatus of claim 13, further comprising: a controller (140) configured to, for a first portion of a control cycle, i) activate the first switch (Q3) to an ON state, ii) deactivate the second switch (Q7) to an OFF state, and iii) directly couple the third node (N52) of the auto-transformer (160) to the reference potential; and for a second portion of the control cycle, i) activate the second switch (Q7) to an ON state, ii) deactivate the first switch (Q3) to an OFF state, and iii) directly couple the second node (N51) of the auto-transformer (160) to the reference potential node (N2).An apparatus comprising: an auto-transformer (160) comprising primary windings and a secondary winding (162); a plurality of switches comprising a first switch (Q3), a second switch (Q4), a third switch (Q7), and a fourth switch (Q8); a plurality of nodes comprising: i) a first node (N31) directly coupling the first switch (Q4) and the second switch (Q4) in series, and ii) a second node (N32) directly coupling the third switch (Q7) and the fourth switch (Q8) in series; wherein the secondary winding (162) is connected between the first node (N31) and the second node (N32); and an output node (N 23) configured to output an output current (iout) based on: i) a first output current (iout1) supplied from the first node (N 31) through the first switch (Q 3) and ii) a second output current (iout2) supplied from the second node (N 32) through the third switch (Q 7).The apparatus of claim 15, further comprising: a fifth switch (Q2) and a sixth switch (Q6); wherein the first switch (Q3) is disposed in series between the fifth switch (Q2) and the second switch (Q4); and wherein the third switch (Q7) is disposed in series between the sixth switch (Q6) and the fourth switch (Q8).The apparatus of claim 16, further comprising: a first circuit path extending between the fifth switch (Q2) and the first node (N31), the first circuit path comprising a first capacitor (CRES1) disposed in series with a first primary winding (161-1) of the auto-transformer (160); and a second circuit path extending between the sixth switch (Q6) and the second node (N32), the second circuit path comprising a second capacitor (CRES2) disposed in series with a second primary winding (161-2) of the auto-transformer (160).The apparatus of claim 17, further comprising: a controller (140) configured to, for a first portion of a control cycle, i) enable the first switch (Q3) to an ON state, ii) disable the third switch (Q7) to an OFF state, and iii) enable the fourth switch (Q8) to directly couple the second node (N32) to a reference voltage node (N2); and for a second portion of a control cycle, i) to enable the third switch (Q7) to an ON state, ii) to disable the first switch (Q3) to an OFF state, and iii) to enable the second switch (Q4) to directly couple the first node (N31) to the reference voltage node (N2).The apparatus of claim 18, wherein the controller (110, 140) is further configured to, for the first portion of the control cycle, i) activate the sixth switch (Q6) to an ON state, ii) deactivate both the second switch (Q4) and the fifth switch (Q3) to an OFF state, and for the second portion of the control cycle, i) activate the fifth switch (Q3) to an ON state, ii) deactivate both the fourth switch (Q8) and the sixth switch (Q6) to an OFF state.The apparatus of claim 1, wherein the currents are first currents; and wherein the first switches (125) are operable to transfer second currents from the auto-transformer (160) through the first switches (125) to the output node (123).

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