Abstract:
A voltage regulator may comprise a high-side switch and a low-side switch for delivering electrical current to the at least one information handling resource, a high-side driver configured to drive a high-side driving voltage for regulating a first electrical current of the high-side switch, a low-side driver configured to drive a low-side driving voltage for regulating a second electrical current of the low-side switch, and a control circuit configured to operate the at least one voltage regulator in both of a fixed dead time mode and an adaptive dead time mode.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates in general to information handling systems, and more particularly to managing a voltage regulator in an information handling system. 
       BACKGROUND 
       [0002]    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. 
         [0003]    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. 
         [0004]    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 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. 
         [0005]    Still, certain inefficiencies may arise due to the driver circuit designs of voltage regulators. For instance, the duration of dead time, which may refer to a time of inactivity between turning one MOSFET on and another off, between high-side and low-side MOSFETs may have an impact on efficiency. For example, using fixed dead time approaches, in which control circuit enforces a dead time of shortest possible fixed duration after a switching event are often efficient in normal steady-state operation of a voltage regulator, but may cause shoot through current when switching after a voltage regulator phase has been re-enabled following being disabled due to phase shedding. As another example, using adaptive dead time approaches (such as that set forth in U.S. Pat. No. 8,219,832, assigned to the same assignee as the present application, and incorporated by reference herein) may introduce unnecessarily long delays when a voltage regulator is operating in steady state, due to complex adaptive control logic and varying parasitic parameters of power state circuitry. 
       SUMMARY 
       [0006]    In accordance with the teachings of the present disclosure, the disadvantages and problems associated with power dissipation in a voltage regulator have been reduced or eliminated. 
         [0007]    In accordance with embodiments of the present disclosure, an information handling system may include at least one information handling resource and at least one voltage regulator coupled to the at least one information handling resource. The voltage regulator may comprise a high-side switch and a low-side switch for delivering electrical current to the at least one information handling resource, a high-side driver configured to drive a high-side driving voltage for regulating a first electrical current of the high-side switch, a low-side driver configured to drive a low-side driving voltage for regulating a second electrical current of the low-side switch, and a control circuit configured to operate the at least one voltage regulator in both of a fixed dead time mode and an adaptive dead time mode. In the fixed dead time mode, the control circuit delays by a fixed amount a propagation of a transition of a pulse-width modulated input signal to at least one of the high-side driver and the low-side driver. In the adaptive dead time mode, the control circuit transitions one of the high-side driving voltage and the low-side driving voltage in response to a determination that the other of the high-side driving voltage and the low-side driving voltage has decreased below a predetermined threshold voltage. 
         [0008]    In accordance with these and other embodiments of the present disclosure, a method may include selecting a mode of operation of a voltage regulator from a fixed dead time mode and an adaptive dead time mode. The method may also include in the fixed dead time mode, delaying by a fixed amount a propagation of a transition of a pulse-width modulated input signal to at least one of a high-side driver and a low-side driver of the voltage regulator, wherein the high-side driver is configured to drive a high-side driving voltage for regulating a first electrical current delivered by a high-side switch to a load and the low-side driver is configured to drive a low-side driving voltage for regulating a second electrical current delivered by a low-side switch to the load. The method may further comprise in the adaptive dead time mode, transitioning one of the high-side driving voltage and the low-side driving voltage in response to a determination that the other of the high-side driving voltage and the low-side driving voltage has decreased below a predetermined threshold voltage. 
         [0009]    In accordance with these and other embodiments of the present disclosure, a voltage regulator may comprise a high-side switch and a low-side switch for delivering electrical current to the at least one information handling resource, a high-side driver configured to drive a high-side driving voltage for regulating a first electrical current of the high-side switch, a low-side driver configured to drive a low-side driving voltage for regulating a second electrical current of the low-side switch, and a control circuit configured to operate the at least one voltage regulator in both of a fixed dead time mode and an adaptive dead time mode. In the fixed dead time mode, the control circuit delays by a fixed amount a propagation of a transition of a pulse-width modulated input signal to at least one of the high-side driver and the low-side driver. In the adaptive dead time mode, the control circuit transitions one of the high-side driving voltage and the low-side driving voltage in response to a determination that the other of the high-side driving voltage and the low-side driving voltage has decreased below a predetermined threshold voltage. 
         [0010]    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. 
         [0011]    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 
         [0012]    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: 
           [0013]      FIG. 1  illustrates a block diagram of an example of an information handling system, in accordance with embodiments of the present disclosure; and 
           [0014]      FIG. 2  illustrates a block diagram of an example voltage regulator, in accordance with embodiments of the present disclosure; and 
           [0015]      FIG. 3  illustrates a flow chart of an example method for managing a voltage regulator, in accordance with embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    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. 
         [0017]    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 or 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. 
         [0018]    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. 
         [0019]    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), busses, 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. 
         [0020]      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 . 
         [0021]    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. 
         [0022]    Power system  110  may include a power controller  112  and a plurality of voltage regulator phases  114 . Power 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  114 . The enabling and disabling of voltage regulator phases  114  is described in greater detail below. 
         [0023]    Each voltage regulator phase  114  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  114  may comprise a phase of the voltage regulator. 
         [0024]    Generally speaking, information handling resources  116  may include any component system, device or apparatus of information handling system  100 , including without limitation processors, busses, 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. 
         [0025]    In operation, power controller  112  may selectively enable and disable one or more voltage regulator phases  114  in response to an electrical current requirement of information handling resources, 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 . 
         [0026]      FIG. 2  illustrates a block diagram of an example voltage regulator  114 , in accordance with embodiments of the present disclosure. In a multi-phase voltage regulation system, voltage regulator  114  depicted in  FIG. 2  may represent a single phase of the multi-phase system. Voltage regulator  114  may comprise a control stage  202 , a driver stage  204 , and a power stage  206 . Control stage  202  may comprise any system, device, or apparatus for controlling a high-side driver HDRV and low-side driver LDRV of driver stage  204  based on input and monitoring signals received by control stage  202 . Such input signals may comprise an enabling signal ENABLE which indicates whether the phase represented by voltage regulator  114  is enabled or disabled and a pulse-width modulation input signal PWM indicating desired output parameters of a voltage regulator output voltage V OUT . Monitoring signals may include a high-side driver output voltage DH, a low-side driver voltage DL, a phase node voltage LX, and a boot capacitor voltage V B . Among the functionality of voltage regulator  114  is to, based on various received input and/or monitoring signals, generate output signals to control dead times of high-side driver HDRV and low-side driver LDRV, including determining whether to apply a fixed dead time or an adaptive dead time based on operational conditions of voltage regulator  114 . 
         [0027]    Driver stage  204  may include high-side driver HDRV and low-side driver LDRV. High-side driver HDRV may generate an output voltage DH that regulates current through high-side switch Q 1  of power stage  206 . Similarly, low-side driver LDRV may generate an output voltage DL that regulates current through low-side switch Q 2  of power stage  206 . 
         [0028]    Power stage  206  may comprise a high-side switch Q 1 , low-side switch Q 2 , and output inductor L 1 . High-side switch Q 1  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 Q 2  may comprise any suitable switching device (e.g., a MOSFET) located between the load and a negative terminal of the power supply or ground. The phase node voltage LX may be generated based on the supply voltage V IN  and switching of switches Q 1  and Q 2  and may also indicate a junction point between high-side switch Q 1  and low-side switch Q 2  and may be fed back into driver stage  204  to provide a reference voltage for high-side switch Q 1  (the low-side switch Q 2 , however, may be referenced to a ground voltage). To that end, a boot capacitor may be coupled between a power supply terminal of high-side driver HDRV and the phase node, and may provide a supply voltage to high-side driver HDRV referenced to the phase node voltage LX. Power stage  206  may also comprise an output inductor L 1  between the phase node and the output of the voltage regulator, which may serve to boost or reduce supply voltage V IN  to generate output voltage V OUT  such that voltage regulator  114  functions as a direct-current to direct-current voltage converter. 
         [0029]    In operation, control stage  202  may, based on various received control signals, control high-side driver HDRV and low-side driver LDRV, including imposition of dead times in accordance with either of a fixed dead-time or an adaptive dead-time, as described in greater detail below with respect to  FIG. 3 . 
         [0030]      FIG. 3  illustrates a flow chart of an example method  300  for managing a voltage regulator, in accordance with embodiments of the present disclosure. According to one embodiment, 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. 
         [0031]    At step  302 , control stage  202  may control high-side driver HDRV and low-side driver LDRV in accordance with a fixed dead time. When operating in fixed dead time mode, control stage  202  may, in response to a transition in signal PWM, delay by a fixed amount the propagation of the transition to either of high-side driver HDRV or low-side driver LDRV. 
         [0032]    At step  304 , control stage  202  may monitor the level of pulse-width modulation signal PWM. Signal PWM may have a full-scale maximum voltage corresponding to logic “1” and a full-scale minimum voltage corresponding to logic “0.” In addition, signal PWM may take on intermediate voltage corresponding to neither logic “0” not logic “1.” For example, signal PWM may have the intermediate voltage when the phase corresponding to voltage regulator  114  is disabled (e.g., has been shed). 
         [0033]    At step  306 , control stage  202  may determine if signal PWM has been at the intermediate voltage for a predetermined threshold period of time. If signal PWM has not been at the intermediate voltage for a predetermined threshold period of time, method  300  may proceed again to step  304 . Otherwise, if signal PWM has been at the intermediate voltage for at least the predetermined threshold period of time, method  300  may proceed to step  308 . 
         [0034]    At step  308 , in response to a determination that signal PWM has been at the intermediate voltage for at least the predetermined threshold period of time, control stage  202  may control high-side driver HDRV and low-side driver LDRV in accordance with an adaptive dead time that adapts to account for manufacturing variation of switches Q 1  and Q 2  that is not easily accounted for with fixed dead time control. Under the adaptive dead time control, control stage  202  may monitor driver output signals DL and DH. When signal PWM transitions high, driver output signal DL may transition low after a propagation delay of control stage  202  and driver stage  204  circuitry. At the same time, control stage  202  may monitor driver output signal DL and cause driver output signal DH to transition high responsive to driver output signal DL falling below a predetermined threshold voltage. On the other hand, when signal PWM transitions low, driver output signal DH may transition low after a propagation delay of control stage  202  and driver stage  204  circuitry. At the same time, control stage  202  may monitor driver output signal DH and cause driver output signal DL to transition high responsive to driver output signal DH falling below a predetermined threshold voltage. 
         [0035]    At step  310 , control stage  202  may determine whether the voltage V B  across boot capacitor C B  is above a predetermined threshold voltage. When a phase is shed and signal PWM remains at the intermediate voltage for a long period of time, voltage V B  may decay from its maximum value (e.g., supply voltage V CC ), making the fixed dead time of the fixed dead time mode insufficiently short to prevent shoot-through current. Once voltage V B  is again near supply voltage V CC , such problem may no longer be of concern. Accordingly, in response to determining that voltage V B  across boot capacitor C B  is above the predetermined threshold voltage, method  300  may proceed again to step  302 , wherein control logic  202  may re-enter the fixed dead time mode. Otherwise, if voltage V B  remains below the predetermined threshold voltage, method  300  may proceed to step  312 . 
         [0036]    At step  312 , responsive to voltage V B  remaining below the predetermined threshold voltage, control stage  202  may determine if signal PWM is at an active voltage level (e.g., not at the intermediate voltage level) and control stage  202  has been operating in the adaptive dead time mode for more than a predetermined minimum duration (e.g., adaptive dead time has been applied for more than a predetermined number of PWM switching cycles). If signal PWM is at an active voltage level and control stage  202  has been operating in the adaptive dead time mode for more than a predetermined minimum duration (which may ensure voltage V B  is charged to a sufficient level), method  300  may proceed again to step  302 , wherein control logic  202  may re-enter the fixed dead time mode. Otherwise, method  300  may proceed again to step  308 , and remain in the adaptive dead-time mode. 
         [0037]    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. 
         [0038]    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. 
         [0039]    By using hybrid fixed dead time and adaptive dead time approach, power conversion efficiency may be maximized due to the shorter dead times that may be implemented in steady-state operation of a voltage regulator, while also permitting adaptive dead time control when transitioning into steady-state operation. 
         [0040]    Although the present disclosure has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and the scope of the disclosure as defined by the appended claims.