Abstract:
A method may include causing a first test current to be delivered for a period of time from a phase of a voltage regulator to a load coupled to the voltage regulator, the phase configured to deliver electrical energy to the load. The method may also include measuring a first measured output current associated with the first test current. The method may further include causing a second test current to be delivered from the phase to the load for the period of time, the second test current differing from the first test current by a known offset. The method may additionally include measuring a second measured output current associated with the second test current. The method may also include calculating the respective gain and the respective offset of the phase based on the first measured output current, the second measured output current, the period of time, and the known offset.

Description:
TECHNICAL FIELD 
     The present disclosure relates in general to information handling systems, and more particularly to sensing a current associated with a voltage regulator in an information handling system. 
     BACKGROUND 
     As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems. 
     An information handling system may include a voltage regulator to provide a constant voltage level and a current to power the system. For example, a voltage regulator may receive an input voltage and produce an output current at a predetermined output voltage required by a load, i.e., the circuit element(s) for which it is providing power. Moreover, modern information handling systems may include components that maintain current requirements across a broad range from relatively high peak currents to very low stable currents. More particularly, voltage regulators may be required to maintain a high efficiency, or low power loss, over such ranges. In particular, a direct current to direct current (DC-DC) voltage regulator may include a controller, one or more drivers, and one or more power stages. Furthermore, a power stage may include one or more metal-oxide-semiconductor-field-effect-transistors (MOSFETs), which may be driven by the drivers. 
     Additionally, some voltage regulators may be capable of operating in multiple phases. To this end, the concept of a phase for a voltage regulator may typically refer to combining a driver and a power stage to form one phase. Thus, a multi-phase voltage regulator may include multiple instances of such combinations. Alternatively, a multi-phase voltage regulator may be thought of as a combination of single phase voltage regulators. For example, a multi-phase voltage regulator may include a plurality of single phase voltage regulators coupled in parallel to provide varying ranges of output current. During periods of high loads, the multi-phase voltage regulator may function with all phases in operation. In contrast, for lower loads, it may employ phase-shedding and operate with a reduced number of phases. 
     To manage power delivery and consumption by voltage regulators, power control systems in information handling systems often execute power management algorithms. For such power management algorithms to effectively manage power, accurate power, current, voltage, and/or other measurements must be obtained. An inherent conflict in obtaining power measurements is that measurement circuitry itself may add power losses to a system. 
     Existing approaches to measuring current associated with a voltage regulator include sensing a current in a component of a voltage regulator, such as an output inductor of a power stage of a voltage regulator phase, which may have a parasitic impedance. Current flowing through such an inductor is linearly proportional to a voltage drop across such parasitic impedance. Thus by measuring a voltage across such components, a current associated with a voltage regulator may be obtained. 
     An advantage of using an output inductor to obtain a current is that such parasitic impedance and its power losses are inherent to a voltage regulator, and thus such measurement approaches add little or no appreciable power consumption themselves. However, the parasitic impedance may have a large range of variation, and thus may result in unacceptable measurement error. 
     SUMMARY 
     In accordance with the teachings of the present disclosure, the disadvantages and problems associated with current sensing in a voltage regulator have been reduced or eliminated. 
     In accordance with embodiments of the present disclosure, an information handling system may include an information handling resource, a voltage regulator, and a controller. The voltage regulator may be coupled to the information handling resource, the voltage regulator comprising one or more voltage regulator phases, each of the one or more voltage regulator phases configured to deliver electrical energy to the information handling resource. The controller may be coupled to the voltage regulator and configured to perform a calibration operation for each of the one or more voltage regulator phases in order to calculate a respective gain and a respective offset for each particular phase of the one or more voltage regulator phases, wherein the respective gain and the respective offset define a linear relationship between a measured output current of the particular phase and an actual output current of the particular phase, and further wherein calculating the respective gain and the respective offset for each particular phase of the one or more voltage regulator phases comprises: (i) causing a first test current to be delivered from the particular phase to the information handling resource for a period of time; (ii) measuring a first measured output current associated with the first test current; (iii) causing a second test current to be delivered from the particular phase to the information handling resource for the period of time, the second test current differing from the first test current by a known offset; (iv) measuring a second measured output current associated with the second test current; and (v) calculating the respective gain and the respective offset of the particular phase based on the first measured output current, the second measured output current, the period of time, and the known offset. 
     In accordance with these and other embodiments of the present disclosure, a method may include causing a first test current to be delivered for a period of time from a phase of a voltage regulator to a load coupled to the voltage regulator, the phase configured to deliver electrical energy to the load. The method may also include measuring a first measured output current associated with the first test current. The method may further include causing a second test current to be delivered from the phase to the load for the period of time, the second test current differing from the first test current by a known offset. The method may additionally include measuring a second measured output current associated with the second test current. The method may also include calculating the respective gain and the respective offset of the phase based on the first measured output current, the second measured output current, the period of time, and the known offset. 
     In accordance with these and other embodiments of the present disclosure, a power system may include a voltage regulator coupled to a load and a controller. The voltage regulator may comprise one or more voltage regulator phases, each of the one or more voltage regulator phases configured to deliver electrical energy to the load. The controller may be coupled to the voltage regulator and configured to perform a calibration operation for each of the one or more voltage regulator phases in order to calculate a respective gain and a respective offset for each particular phase of the one or more voltage regulator phases, wherein the respective gain and the respective offset define a linear relationship between a measured output current of the particular phase and an actual output current of the particular phase, and further wherein calculating the respective gain and the respective offset for each particular phase of the one or more voltage regulator phases comprises: {i) causing a first test current to be delivered from the particular phase to the load for a period of time; (ii) measuring a first measured output current associated with the first test current; (iii) causing a second test current to be delivered from the particular phase to the load for the period of time, the second test current differing from the first test current by a known offset; (iv) measuring a second measured output current associated with the second test current; and (v) calculating the respective gain and the respective offset of the particular phase based on the first measured output current, the second measured output current, the period of time, and the known offset. 
     Technical advantages of the present disclosure may be readily apparent to one skilled in the art from the figures, description and claims included herein. The objects and advantages of the embodiments will be realized and achieved at least by the elements, features, and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are examples and explanatory and are not restrictive of the claims set forth in this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: 
         FIG. 1  illustrates a block diagram of an example of an information handling system, in accordance with embodiments of the present disclosure; 
         FIG. 2  illustrates example contents of a gain/offset table for use by the voltage regulator controller depicted in  FIG. 1 , in accordance with embodiments of the present disclosure; and 
         FIG. 3  illustrates a flow chart of an example method for self-calibration of a voltage regulator, in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments and their advantages are best understood by reference to  FIGS. 1-3 , wherein like numbers are used to indicate like and corresponding parts. 
     For the purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, entertainment, or other purposes. For example, an information handling system may be a personal computer, a personal data assistant (PDA), a consumer electronic device, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include memory, one or more processing resources such as a central processing unit (CPU) or hardware or software control logic. Additional components of the information handling system may include one or more storage devices, one or more communications ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communication between the various hardware components. 
     For the purposes of this disclosure, computer-readable media may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Computer-readable media may include, without limitation, storage media such as a direct access storage device (e.g., a hard disk drive or floppy disk), a sequential access storage device (e.g., a tape disk drive), compact disk, CD-ROM, DVD, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), and/or flash memory; as well as communications media such as wires, optical fibers, microwaves, radio waves, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing. 
     For the purposes of this disclosure, information handling resources may broadly refer to any component system, device or apparatus of an information handling system, including without limitation processors, service processors, basic input/output systems (BIOSs), buses, memories, I/O devices and/or interfaces, storage resources, network interfaces, motherboards, power supplies, air movers (e.g., fans and blowers) and/or any other components and/or elements of an information handling system. 
       FIG. 1  illustrates a block diagram of an example of an information handling system  100  incorporating a power system  110  in accordance with an embodiment of the present disclosure. As depicted, information handling system  100  may include a power system  110 , and one or more other information handling resources  116 . 
     Generally speaking, power system  110  may include any system, device, or apparatus configured to supply electrical current to one or more information handling resources  116 . 
     In some embodiments, power system  110  may include a multi-phase voltage regulator. 
     Power system  110  may include a voltage regulator controller  112  and a plurality of voltage regulator phases wherein each voltage regulator phase comprises a driver stage  104  and a power stage  106 . Voltage regulator controller  112  may include any system, device, or apparatus configured to control the output of power system  110  and/or selectively enable and disable voltage regulator phases. Although  FIG. 1  depicts voltage regulator controller  112  as being integral to power system  110 , in some embodiments, some or all of the structure and/or functionality of voltage regulator controller  112  may be integral to another information handling resource  116  of information handling system  100 . For example, in some embodiments, some of the structure and/or functionality of voltage regulator controller  112  may be integral to a remote access controller, such as a Dell Remote Access Controller (DRAC) or Integrated Dell Remote Access Controller (iDRAC). 
     As stated above, each voltage regulator phase may include a driver stage  104  and a power stage  106 . A voltage regulator phase may include any system, device, or apparatus configured to supply a portion of the total current output of power system  110 . In embodiments in which power system  110  is a multi-phase voltage regulator, a voltage regulator phase may comprise a phase of the voltage regulator. 
     A driver stage  104  may include a high-side driver and a low-side driver LDRV. A power stage  106  may comprise a high-side switch  108 , low-side switch  109 , and output inductor  111 . High-side switch  108  may comprise any suitable switching device (e.g., a metal-oxide-semiconductor field-effect transistor or “MOSFET”) located between a positive terminal of a power supply V IN  and a load, while low-side switch  109  may comprise any suitable switching device (e.g., a MOSFET) located between the load and a negative terminal of the power supply or ground. A phase node voltage LX may be generated based on the supply voltage V IN  and switching of switches  108  and  109  and may also indicate a junction point between high-side switch  108  and low-side switch  109 . Output inductor  111  may be coupled between phase node LX and the output of the voltage regulator phase, which may serve to boost or reduce supply voltage V IN  to generate output voltage V OUT  such that the voltage regulator phase functions as a direct-current to direct-current voltage converter. 
     In operation, driver  104  may activate and deactivate high-side switches  108  and low-side switches  109  in response to a switching signal from voltage regulator controller  112 . High-side switches  108  and low-side switches  109  may operate in a complementary mode, with one of the high-side switches  108  and low-side switches  109  of each phase activated and one deactivated during steady-state operating conditions. When a high-side switch  108  of a phase is activated and its corresponding low-side switch  109  is deactivated, the input power will charge the inductor  111  and supply a current to information handling resources  116 . Conversely, when the low-side switch  109  is activated and the high-side switch  108  is deactivated, the inductor current will be discharged by a freewheeling loop consisting of inductor  111 , an output capacitor coupled between V OUT  and a ground voltage, and low-side switch  109 . 
     Although  FIG. 1  depicts two voltage regulator phases each comprising a driver stage  104  and power stage  106 , power system  110  may include any suitable number of voltage regulator phases. 
     Generally speaking, information handling resources  116  may include any component system, device or apparatus of information handling system  100 , including without limitation processors, buses, computer-readable media, input-output devices and/or interfaces, storage resources, network interfaces, motherboards, electro-mechanical devices (e.g., fans), displays, and/or power supplies. 
     In operation, voltage regulator controller  112  may selectively enable and disable one or more voltage regulator phases in response to an electrical power requirement of information handling resources  116 , such that one or more phases may be shed to reduce power consumption of power system  110  in response to the reduced current requirement, and thus increase power efficiency of information handling system  100 . Accordingly, voltage regulator controller  112  may control driver stages  104  such that the appropriate power stages  106  provide the desired level of power to information handling resources  116 . 
     In addition, voltage regulator controller  112  may be configured to measure a measured output current for each respective voltage regulator phase. For example, voltage regulator  112  may measure a voltage across an output inductor  111  of a phase (e.g., the voltage difference between an output voltage VOUT and a voltage present at phase node voltage LX of such phase) and determine the measured output current of the phase to be equal to the measured voltage divided by a nominal parasitic impedance of output inductor  111 . 
     However, due to process and/or other variations, an actual impedance of an output inductor  111  may vary from its nominal parasitic impedance. Thus, an actual output current of a phase may differ significantly from its measured output current. Accordingly, voltage regulator controller  112  may also be configured to calibrate each phase of power system  110  in order to account for ranges of variation in parasitic impedances of output inductors  111  which may result in measurement error. An example of such a process for calibration is described in greater detail below in reference to  FIG. 3 . 
     As a result of calibration operations, voltage regulator controller  112  may maintain calibration information in a gain/offset table  114 . Gain/offset table  114  may comprise a table, map, list, array, and/or other suitable data structure stored on computer-readable media integral to or otherwise accessible to voltage regulator controller  112 . As shown in  FIG. 2 , gain/offset table  114  may comprise an entry for each voltage regulator phase of power system  110 , and each entry may set forth a gain m and an offset c for each respective voltage regulator phase. The gain m and offset c for each voltage regulator phase may define a linear relationship between an actual output current i act  for the voltage regulator phase and a measured output current i meas  for which may be given by the equation:
 
 i   act   =m·i   meas   +c    (eq. 1)
 
     The calculation of the various values of gain m and offset c for each voltage regulator phase may be made in accordance with the calibration operation described in greater detail with respect to  FIG. 3 .  FIG. 3  illustrates a flow chart of an example method  300  for self-calibration of a voltage regulator, in accordance with embodiments of the present disclosure. According to one or more embodiments, method  300  may begin at step  302 . As noted above, teachings of the present disclosure may be implemented in a variety of configurations of information handling system  100 . As such, the preferred initialization point for method  300  and the order of the steps comprising method  300  may depend on the implementation chosen. 
     At step  302 , voltage regulator controller  112  may enable components of power system  110 . At step  304 , voltage regulator controller  112  may determine if output voltage V OUT  has reached its regulated output voltage. If output voltage V OUT  has reached its regulated output voltage, method  300  may proceed to step  306 . Otherwise, method  300  may remain at step  304  until output voltage V OUT  reaches its regulated output voltage. 
     At step  306 , in response to output voltage V OUT  reaching its regulated output voltage, voltage regulator controller  112  may initialize one or more calibration variables. For example, voltage regulator controller  112  may initialize a counter variable n to an initial value (e.g., 1). It should be noted that, in some embodiments, voltage regulator controller  112  may initiate calibration prior to output voltage V OUT  reaching its regulated output voltage, or even before a phase is enabled, meaning calibration may take place when output voltage V OUT  is at zero. In such embodiments, method  300  may not include step  304 , and method  300  may proceed from step  302  to step  306 . 
     At step  308 , voltage regulator controller  112  may determine if all phases N of power system  110  have been calibrated by comparing the counter variable n to the value N. If n is less than or equal to N, method  300  may proceed to step  310 . Otherwise, method  300  may end. 
     At step  310 , voltage regulator controller  112  may enable phase n of power system  110  and disable all other phases. 
     At step  312 , voltage regulator controller  112  may cause a first test current through output inductor  111  of phase n for a period of time dT (e.g., 50-100 μs). The actual output current i act   _   1  of the first test current may not be known, but may be measured by voltage regulator controller  112  as an output measured current i meas   _   1 , which may be a current reported by measuring a voltage across a parasitic resistance of output indictor  111 . 
     At step  314 , voltage regulator controller  112  may measure a change in voltage dV 1  induced over the time period dT by the first test current, and record the change in voltage dV 1 , the time period dT, and the output measured current i meas   _   1 . 
     At step  316 , voltage regulator controller  112  may cause a second test current through output inductor  111  of phase n for the period of time dT. The actual output current i act   _   2  of the second test current may not be known, but may be different from actual output current i act   _   2  by a known offset K such that i act   _   2 =i act   _   1 +K, and may be measured by voltage regulator controller  112  as an output measured current i meas   _   2 , which may be a current reported by measuring a voltage across a parasitic resistance of output indictor  111 . 
     At step  318 , voltage regulator controller  112  may measure a change in voltage dV 2  induced over the time period dT by the second test current, and record the change in voltage dV 2  and the output measured current i meas   _   2 . In some embodiments, prior to application of the second test current, the output voltage V OUT  and the current through output inductor  111  may be set to the respective values they had prior to application of the first test current. 
     At step  320 , voltage regulator controller  112  may, based on the measurements of changes in voltages dV 1  and dV 2 , the period of time dT, and the offset K, determine an output load capacitance C of the output of power system  110 . To illustrate, the actual currents i act   _   a  and i act   _   2  may be given by the equations:
 
 i   act   _   1   =C·dV   1   /dT    (eq. 2)
 
 act   2   =i   act   _   1   +K=C·dV   2   /dT    (eq. 3)
 
Substituting eq. 2 into eq. 3:
 
 C·dV   1   /dT+K=C·dV   2   /dT  
 
and solving eq. 3 for output load capacitance C:
 
 C=K /( dV   2   /dT−dV   1   /dT )
 
Because values of K, dT, dV 1 , and dV 2  are known, output load capacitance C may be calculated. In some embodiments, instead of the period of time dT being the same for the application of each test current, in some embodiments, a first test current and second test current may be applied such that they induce the same voltage change dV, in which case capacitance C is determined based on the different period of time in which the two test currents induce a voltage change dV.
 
     At step  322 , voltage regulator controller  112  may, based on the calculated output load capacitance C, the measurements of changes in voltages dV 1  and dV 2 , and the period of time dT, determine the actual output load currents i act   _   1  and i act   _   2  using eqs. 2 and 3. 
     At step  324 , voltage regulator controller  112  may, based on the actual output load currents i act   1  and i act   _   2  and the measured output load currents i meas   _   1  and i meas   _   2  respectively associated with actual output load currents i act   _   1  and i act   _   2  calculate a gain m and offset c for phase n by solving for gain m and offset c the equations:
 
 i   act   _   1   =m·i   meas   _   1   +c  
 
 i   act   _   2   =m·i   meas   _   2   +c  
 
     At step  326 , voltage regulator controller  112  may store the calculated gain m and offset c for voltage regulator phase n in gain/offset table  114 . 
     At step  328 , voltage regulator controller  112  may increment the counter n by 1. After completion of step  328 , method  300  may return again to step  308 . 
     Although  FIG. 3  discloses a particular number of steps to be taken with respect to method  300 , method  300  may be executed with greater or fewer steps than those depicted in  FIG. 3 . In addition, although  FIG. 3  discloses a certain order of steps to be taken with respect to method  300 , the steps comprising method  300  may be completed in any suitable order. 
     Method  300  may be implemented using information handling system  100  or any other system operable to implement method  300 . In certain embodiments, method  300  may be implemented partially or fully in software and/or firmware embodied in computer-readable media and executable on a processor of information handling system  100 . 
     After calibration, and during regular operation of power system  110 , voltage regulator controller  112  may read a measured current i meas  associated with a phase, and determine an actual current i act  for the phase in accordance with the calibrated values gain m and offset c stored in an entry of gain/offset table  114  corresponding to the phase, in accordance with eq. 1. 
     As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected indirectly or directly, with or without intervening elements. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. 
     All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.