Abstract:
Hybrid buck converters that incorporate switching converter and auxiliary linear regulators are described. The auxiliary linear regulators are automatically activated during load transients to source or sink large currents to the output to achieve fast transient responses and are automatically deactivated during steady states to maintain high power efficiencies. With the proposed control scheme of automatic loop transition between linear and switching regulation loops, the power management interface design is simplified while the transient response performances are improved without compromising the power efficiencies.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. provisional application No. 61/741,455, filed on Jul. 20, 2012 and entitled: “Hybrid buck converters with automatic loop transition.” The entirety of this provisional application is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to voltage regulation in a device, e.g., to hybrid buck converters with automatic loop transitions to regulated voltage and related embodiments. 
     BACKGROUND 
     Power management integrated circuits manage power requirements for larger systems, such as cell phones, tablets, and other devices. Power management integrated circuits perform various functions related to the power requirements. Some common functions include DC to DC conversion, battery charging, power source selection, voltage scaling, frequency scaling, and power sequencing. 
     Power management integrated circuits include converters for voltage step-up/step down and for power factor correction. A parallel chopper or “boost” converter, converts DC-to-DC power with an output voltage greater than its input voltage. Boost converters contain at least two semiconductor switches (a diode and a transistor) and at least one energy storage element, a capacitor, inductor, or the two in combination. A series chopper or “buck” converter is a step-down DC to DC converter that reduces an input voltage from a power supply to a lower output voltage for use by a load. Its design is similar to the step-up boost converter, and like the boost converter, it is a switched-mode power supply that uses two switches (a transistor and a diode), an inductor and a capacitor. 
     Switching converters are indispensable components in battery-powered portable devices for their high efficiency. With more and more complicated and highly-integrated system-on-chip (SoC) designs, fast transient responses are crucial for switching converters to fit the demands of SoC. Hysteretic control provides fast response; however, complicated delay compensation scheme is required in order to fix the switching frequency to achieve a predictable noise spectrum. 
     On the other hand, pulse-width-modulation control has been attractive for its well predictable and manageable noise spectrum due to the fixed switching frequency. However, pulse-width-modulation control has limited loop bandwidth and low slew-rate of the inductor current and hence the transient response is very slow. The hybrid supply module, which consists of a parallel operation of switching converter and linear regulator, has the potential to be a successful combination of good power efficiency and high loop bandwidth. However, the existing hybrid control schemes either have poor efficiency, cannot be directly applied in a DC-DC converter, or do not target at fast transient response, or need a third party to inform the happening of load transients and hence have limited applicability. 
     The above-described background is merely intended to provide an overview of contextual information regarding power management integrated circuit devices, and is not intended to be exhaustive. Additional context may become apparent upon review of one or more of the various non-limiting embodiments of the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Numerous aspects and embodiments are set forth in the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is an example functional high level block diagram of a system that facilitates voltage management, according to an aspect or embodiment of the subject disclosure; 
         FIG. 2  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter, according to an aspect or embodiment of the subject disclosure; 
         FIG. 3  is a timing diagram showing load transient responses in a load current step-up of a single-phase hybrid buck converter, according to an aspect or embodiment of the subject disclosure; 
         FIG. 4  is a timing diagram showing load transient responses in a load current step-down of a single-phase hybrid buck converter, according to an aspect or embodiment of the subject disclosure; 
         FIG. 5  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a linear regulator and controller, according to an aspect or embodiment of the subject disclosure; 
         FIG. 6  is an example non-limiting schematic diagram of a hysteretic load transient detector, according to an aspect or embodiment of the subject disclosure; 
         FIG. 7  is an example non-limiting schematic diagram of a hysteretic load transient detector, according to an aspect or embodiment of the subject disclosure; 
         FIG. 8  is an example non-limiting schematic diagram of an adaptive duty ratio compensator that selects a maximum and minimum duty ratio, according to an aspect or embodiment of the subject disclosure; 
         FIG. 9  is an example non-limiting schematic diagram of an adaptive duty ratio compensator, according to an aspect or embodiment of the subject disclosure; 
         FIG. 10  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter, linear regulators, and a controller used to achieve undershoot fast-recovery and overshoot prevention-only, according to an aspect or embodiment of the subject disclosure; 
         FIG. 11  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter and linear regulator used to achieve undershootfast-recovery and an over voltage protection logic, according to an aspect or embodiment of the subject disclosure; 
         FIG. 12  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter and a linear regulator used to achieve undershoot prevention-only and an over voltage protection logic, according to an aspect or embodiment of the subject disclosure; 
         FIG. 13  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter, linear regulators, and a controller used to achieve undershoot prevention-only and overshoot fast-recovery, according to an aspect or embodiment of the subject disclosure; 
         FIG. 14  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a single phase hybrid buck converter and linear regulators and controller used to achieve undershoot prevention —only and overshoot prevention —only, according to an aspect or embodiment of the subject disclosure; 
         FIG. 15  is an example non-limiting schematic diagram of a system that facilitates automatic loop transitions including a multi-phase hybrid buck converter, according to an aspect or embodiment of the subject disclosure; 
         FIG. 16  is an example non-limiting process flow diagram of a method that facilitates automatic loop transitions and voltage management of a semiconductor device, according to an aspect or embodiment of the subject disclosure; 
         FIG. 17  is an example non-limiting process flow diagram of a method that facilitates automatic loop transitions and voltage management of a semiconductor device, according to an aspect or embodiment of the subject disclosure; and 
         FIG. 18  is an example non-limiting process flow diagram of a method that facilitates automatic loop transitions and voltage management of a semiconductor device, according to an aspect or embodiment of the subject disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects or features of this disclosure are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In this specification, numerous specific details are set forth in order to provide a thorough understanding of this disclosure. It should be understood, however, that the certain aspects of disclosure may be practiced without these specific details, or with other methods, components, molecules, etc. In other instances, well-known structures and devices are shown in block diagram form to facilitate description and illustration of the various embodiments. Additionally, elements in the drawing figures are not necessarily drawn to scale; some areas or elements may be expanded to help improve understanding of certain aspects or embodiments. 
     The subject application is generally related to a DC to DC converter with automatic loop transitions in a semiconductor device to provide a power management. The systems and methods can regulate a voltage to a predefined voltage level during load transient periods and can deactivate regulators during steady states. 
     The device can include a hybrid-buck converter with automatic loop transition. A buck converter can receive an input voltage and output an output voltage that is lower than the input voltage. The buck converter can provide voltage regulation utilizing switches that can generate an output voltage to a predefined voltage level. The device can include one or more regulators, such as linear regulators. A linear regulator can detect output overshoot voltage and/or output undershoot voltage. A linear regulator can provide source current to an output load when the regulator detects an undershoot voltage. In another aspect, a linear regulator can sink current when the regulator detects overshoot voltage. 
     As an example, hybrid buck converters are described to facilitate the understanding of the voltage control and loop transitions described herein. It is noted, however, that other semiconductor device can achieve voltage regulation and automatic loop transitions through the systems and methods described herein. 
     Various implementations described herein provide automatic loop transitions and voltage regulation. The implementations can provide increased efficiency of power management in a semiconductor device. It is noted that implementations can simplify power management semiconductor devices, while decreasing overall size, decreasing power consumption, increasing reliability, decreasing load transient performance time, and the like. It is further noted that the terms “buck converter”, “single-phase buck converter”, “multi-phase buck converter”, “switching converter”, and the like can refer to various devices and/or systems configured to perform DC to DC voltage conversion (e.g., step down). Unless otherwise stated or contexts suggests otherwise, the terms can be used interchangeably. 
       FIG. 1  is an example functional high level block diagram of a system  100  that facilitates voltage management of a semiconductor device. As described herein, the system  100  can be considered a hybrid buck converter. It is noted that the system  100  can be various other types of semiconductor device. While the various components are illustrated as separate components, it is noted that the various components can be comprised in one or more other components. Further, it is noted that the system  100  can comprise additional components not shown for readability. Additionally, the various components may be contained on one integrated circuit, or on a number of individual circuits coupled together. It is further noted that system  100  can be within larger system such as smart phones, tablets, e-readers, digital video recorders, mobile music players, personal computers, servers, memory sticks, digital video recorders (DVRs), consumer electronics and the like. 
     In implementations, system  100  can comprise a power source  110 , a switching converter  120 , a voltage regulator  130 , and an output  140 . The power source  110  can supply voltage to various components. In an aspect, the power source  110  can comprise a battery and/or other power supply. 
     Switching converter  120  can comprise circuitry for voltage conversion, such as DC to DC voltage step down. In an aspect the switching converter  120  can comprise buck converts, single-phase buck converters, multi-phase buck converters, and the like. In another aspect, the switching converter can generate an output  140  comprising a voltage. 
     Voltage regulator  130  can be configured to adjust a voltage based on the output  140 . In an implementation, the voltage regulator  130  can determine whether or not the output  140  exceeds a predefined level above a reference voltage (e.g., overshoot voltage threshold). If the voltage regulator  130  determines that the output  140  exceeds a predefined level above a reference voltage the voltage regulator  130  can sink the output  140  to a predefined steady-state level. 
     In an aspect, the voltage regulator  130  can determine whether or not the output  140  has returned to a level satisfying a steady-state level, after being above a threshold level. If the voltage regulator  130  determines that the output  140  has returned to a level satisfying a steady-state level, the voltage regulator  130  can enter an off state thereby decreasing power consumption. 
     In various implementations, the voltage regulator  130  can determine whether or not the output  140  exceeds a predefined level below a reference voltage (e.g., undershoot voltage threshold). If the voltage regulator  130  determines that the output  140  exceeds a predefined level below a reference voltage, the voltage regulator  130  can source the output  140  to a predefined steady-state level. 
     In an another aspect, the voltage regulator  130  can determine whether or not the output  140  has returned to a level satisfying a steady-state level after being below a threshold level. If the voltage regulator  130  determines that the output  140  has returned to a level satisfying a steady-state level, the voltage regulator  130  can enter an off state thereby decreasing power consumption of system  100 . 
       FIG. 2  is an example non-limiting schematic diagram of a system  200  that facilitates automatic loop transitions and voltage regulation. As described herein, the system  200  can be considered a single phase hybrid buck converter. It is noted that the system  200  can be various other types of semiconductor device. While the various components are illustrated as separate components, it is noted that the various components can be comprised in one or more other components. Further, it is noted that the system  200  can comprise additional components not shown for readability. Additionally, the various components can be contained on one integrated circuit, or on a number of individual circuits coupled together. 
     It is further noted that system  200  can be within larger system such as smart phones, tablets, e-readers, digital video recorders, mobile music players, personal computers, servers, memory sticks, digital video recorders (DVRs), consumer electronics and the like. 
     The system  200  includes an input  210  (e.g., V g ), a first switch  220  between input  210  and vertex  222 , an inductor  230  coupled between vertex  222  (e.g., node) and an output terminal  252 , a second switch  240  between vertex  222  and a ground  242 , an output capacitor  250  coupled to the output terminal  252  or ground, a controller  260 , a reference  264 , a linear regulator(s)  268 , and an output  270 . Input  210  can comprise a voltage source providing a current to the system  200 . In an aspect, input  210  can comprise a battery or other power source. For example, input  210  can correspond to a voltage supplied by an internal battery of a larger device, a wall power supply, a universal serial port power supply, and the like. The first switch  220  and the second switch  240  can represent a component that can complete an electrical circuit, break an electrical circuit, interrupt current, or divert current. It is noted that the first switch  220  and the second switch  240  can be coupled in series with a source of electric potential. In an aspect, the electrical potential can be between a positive supply and a ground, positive supply and a negative supply, different supply voltages of like polarity, and the like. 
     In an implementation, the controller  260  can control states of switches (on/off). In another aspect, the controller  260  can control first switch  220  and second switch  240  to accumulate a charge on the inductor  230 . The controller  260  can deliver charge to the output  270  to regulate a predefined voltage (e.g., a DC voltage). 
     While depicted as switches with terminals that are either connected or disconnected from each other, it is noted that the first switch  220  and the second switch  240  can comprise single pole switches, bipolar transistors, metal-oxide-semiconductor field-effect transistor (MOSFET) transistors, diodes, and the like. 
     Linear regulator  268  can detect output overshoot voltage and/or output undershoot voltage. In another aspect, linear regulator  268  can provide source current to an output load when the linear regulator  268  detects an undershoot voltage. In another aspect, linear regulator  268  can sink current when the linear regulator  268  detects overshoot voltage. Linear regulator  268  can automatically deactivate at steady states and activate at transient states. It is noted that linear regulator  268  can comprise one or more auxiliary linear regulators, be constructed using bipolar transistors, MOSFET transistors, and/or the various other components. 
     In an implementation, linear regulator  268  can comprise two linear regulators. A first linear regulator of the linear regulator  268  can detect a predefined output undershoot voltage and sources current to the output  270  and/or the output capacitor  250 . For example, an undershoot voltage can be caused by a large load current step-up and the first linear regulator of the linear regulator  268  can regulate the voltage back up to a predefined output. A second linear regulator of the linear regulator  268  detects a predefined output overshoot voltage and sinks current from the output  270  and/or output capacitor  250 . For example, an overshoot voltage can be caused by a large load current step-down and the second linear regulator of the linear regulator  268  can regulate the voltage back down to a predefined output. 
     Reference  264  can comprise a voltage reference and/or a current reference. A voltage reference of reference  264  can comprise an electronic device that produces a fixed or constant voltage irrespective of a load on the reference  264 , power supply variations, temperature changes, and the passage of time. Similarly, a current reference of reference  264  can comprise an electronic device that produces a fixed or constant current irrespective of a load on the reference  264 , power supply variations, temperature changes, and the passage of time. Reference  264  can regulate parallel operation of switching and linear components of the system  200 . 
     In implementations, the linear regulator  268  can detect voltage undershoot/overshoot based on a predefined tolerance level. For example, the linear regulator  268  can determine whether or not a voltage is within a threshold variance from a voltage reference of the reference  264 . Likewise, linear regulator  268  can determine whether or not a current is within a threshold variance from a current reference of the reference  264 . In an aspect, a threshold can be a predefined value, percentage, and/or dynamically determined. 
       FIG. 3  is an example non-limiting timing diagram  300  of load transient responses of system  200  of  FIG. 2 . In an aspect, diagram  300  depicts timing of system  200  when the linear regulator  268  of  FIG. 2  detects that the output  270  undershoots a predefined value. 
     Linear regulator  268  can determine whether or not the output  270  undershoots a predefined value. Diagram  300  depicts the output  270  as V out    320  and depicts the predefined value as ΔV 1    322  which steps down between a period from A  360  to B  362 . In an aspect, the undershoot voltage can be caused by output current  272  of  FIG. 2  step-up. For example, output current, represented as I out    310  can step up by a value of ΔI 1    312 . 
     At or about B  362 , linear regulator  268  is activated to source a current of I LR    340  to the loading to prevent the output  270  from further decreasing. For example, linear regulator  268  can provide a current, in the direction indicated, to the output  270 . In an aspect, I LR    340  can represent a relatively large source current compared to a current I L    330  provided by the inductor  230 . Additionally, at or about B  362 , a duty ratio and hence current I L    330  generated by inductor  230  is increased to provide more charge to the loading. In an aspect, the output  270  can rise to a value defining a steady-state value. In an aspect, the value defining the steady-state value can be determined based on reference  264 . 
     In another aspect, as inductor  230  increases current I L    330 , the need for I LR    340  decreases as I L    330  and I LR    340  sum up to or approximately to the value of I out    310 . For example, at or about C  364 , I LR    340  begins to decrease as I L    330  begins to increase. After linear regulator  268  provides the initial large value of I LR    340 , the linear regulator  268  can decrease the value of I LR    340 . In another aspect, the linear regulator  268  can determine whether or not the value of I LR    340  is decreased to a predefined value (e.g., inductor  230  produces a large enough current to support the loading). When the linear regulator  268  can determine the value of I LR    340  is decreased to the predefined value, the linear regulator  268  can deactivate at or about D  366 . In an aspect, deactivating the linear regulator  268  can result in increased efficiency and decreased power consumption. 
     In another aspect, an internal signal EN 1   350  can be generated to indicate a beginning and ending of the load transient period D 1   368 . The linear regulator  268  can alter EN 1   350  (e.g., set to “1”) to instruct first switch  220  and second switch  240  to complete a linear regulation loop to reduce the undershoot voltage and reduce the recovery time. In another aspect, linear regulator  268  can return EN 1   350  to “0” such that the linear regulation loop is interrupted after D 1   368  ends (e.g., linear regulator  268  is deactivated). 
       FIG. 4  is an example non-limiting timing diagram  400  of load transient responses of system  200  of  FIG. 2 . In an aspect, diagram  400  depicts timing of system  200  when the linear regulator  268  of  FIG. 2  detects that the output  270  overshoots a predefined value. 
     Linear regulator  268  can determine whether or not the output  270  overshoots a predefined value. Diagram  400  depicts the output  270  as V out    420  and depicts the predefined value as ΔV 2    422  which steps up between a period from A  460  to B  462 . In an aspect, the overshoot voltage can be caused by output current  272  of  FIG. 2  step-down. For example, output current  272  can decrease as depicted by I  out    410  step down by a value of ΔI 2    412 . 
     At or about B  462 , linear regulator  268  is activated to sink a current of I LR    340  to the loading to prevent the output  270  from further increasing. In an aspect, the linear regulator  268  can sink a predefined amount of current. Additionally, at or about B  462 , a duty ratio, and hence current I L    430  generated by inductor  230 , is decreased to provide less charge to the loading. In an aspect, the output  270  can be decreased to a value defining a steady-state value. In an aspect, the value defining the steady-state value can be determined based on reference  264 . 
     In another aspect, as inductor  230  decreases current I L    430 , the need for I LR    440  decreases as I L    430  and I LR    440  sum up to or approximately to the value of I out    410 . For example, at or about C  464 , I LR    440  begins do increase as I L    430  begins to decrease. After linear regulator  268  provides the initial value of I LR    340 , the linear regulator  268  can decrease the value of I LR    440 . In another aspect, the linear regulator  268  can determine whether or not the value of I LR    440  is decreased to a predefined value (e.g., inductor  230  decreases current to support the loading). When the linear regulator  268  determines the value of I LR    440  is decreased to the predefined value, the linear regulator  268  can deactivate at or about D  466 . In an aspect, controller  260  can deactivate the linear regulator  268 . In an aspect, deactivating the linear regulator  268  can result in increased efficiency and decreased power consumption. 
     In another aspect, an internal signal EN 2   450  can be generated to indicate a beginning and ending of the load transient period D 2   468 . The controller  260  can set a value of EN 2   450  at “1” to instruct first switch  220  and second switch  240  to complete a linear regulation loop to reduce the overshoot voltage and reduce the recovery time. In an aspect, the controller  260  can set EN 2   450  to “0” such that the linear regulation loop is interrupted after the D 2   468  ends (e.g., when linear regulator  268  is deactivated). 
       FIG. 5  is an example non-limiting schematic diagram of a system  500  that facilitates automatic loop transitions including a linear regulator and controller. As described herein, the system  500  can be considered a single phase hybrid buck converter. It is noted that the system  500  can be various other types of semiconductor device. While the various components are illustrated as separate components, it is noted that the various components can be comprised in one or more other components. Further, it is noted that the system  500  can comprise additional components not shown for readability. Additionally, the various components may be contained on one integrated circuit, or on a number of individual circuits coupled together. 
     It is further noted system  500  can be within larger system such as smart phones, tablets, e-readers, digital video recorders, mobile media devices, personal computers, servers, memory sticks, digital video recorders (DVRs), solid state machines, consumer electronics and the like. 
     The system  500  includes power source  510  (e.g., V g ), a first switch  514  between power source  510  and vertex  518 , an inductor  522 , a second switch  526  between vertex  518  and a ground  528 , an output capacitor  532 , a ground  536 , a controller  540  that can control states of switches (on/off), an output voltage  550 , an output current  552 , a first linear regulator  560 , and a second linear regulator  580 . The controller  540  can comprise a logic and driver component  542  that can turn on/off switches, a ratio compensator  544  that can stabilizes a switching converter and can be adjusted to have faster response during load transients, and a clock and ramp generator  546 . It is noted that various components can comprise functionality similar to the components of  FIG. 2 . The first linear regulator  560  can detect a predefined output undershoot voltage and can source current to an output load. The second linear regulator  580  can detect a predefined output overshoot and can sink current from the output load. 
     The first linear regulator  560  can determine whether or not output  550  meets a predefined threshold defining an undershoot voltage. When the first linear regulator  560  determined the output  550  meets the predefined threshold defining the undershoot voltage, the first linear regulator  560  can provide a sourcing current (I LR ) to an output load. In an aspect, the provided source current can reduce a value of undershoot voltage during a load transient period. 
     The first linear regulator  560  can comprise a steady state reference voltage  562 , a transient reference voltage  564 , a switch  566 , a switch  568 , an amplifier  570 , a hysteretic load transient detector  572  that indicates a beginning and ending of a load transient period, a power source  574  (V G ′) that can be the same or a disparate power source as power source  510 , a cell  576 , and an error amplifier  578 . It is noted that steady state reference voltage  562 , transient reference voltage  564 , switch  566 , switch  568 , amplifier  570 , hysteretic load transient detector  572 , and/or power source  574  can represent a reference selection network that selects a lower reference voltage to detect a predefined output undershoot voltage and select a higher reference voltage to make the linear regulator source larger current to the output. 
     The second linear regulator  580  can determine whether or not output  550  meets a predefined threshold defining an overshoot voltage. When the second linear regulator  580  determined the output  550  meets the predefined threshold defining the overshoot voltage, the second linear regulator  580  can sink current (I LR ) from an output load. In an aspect, the sinking current can reduce overshoot voltage during a transient period. 
     The second linear regulator  580  can comprise a steady state reference voltage  582 , a transient reference voltage  584 , a switch  586 , a switch  588 , an amplifier  590 , a hysteretic load transient detector  592  that indicates a beginning and ending of a load transient period, a cell  594 , and an error amplifier  596 . It is noted that steady state reference voltage  582 , transient reference voltage  584 , switch  586 , switch  588 , amplifier  590 , hysteretic load transient detector  592 , and/or power source  594  can represent a reference selection network that selects a higher reference voltage to detect a predefined output overshoot voltage and select a lower reference voltage to make the linear regulator sink larger current from the output. 
     In a steady state, the first linear regulator  560  selects steady state reference voltage  562  as a reference voltage by turning switch  568  to an on state (switch  566  off). When the first linear regulator  560  determines to enter a transient state, the first linear regulator selects transient reference voltage  564  as the reference voltage by turning switch  566  to an on state (switch  568  off). In an aspect, when the first linear regulator  560  uses steady state reference voltage  562 , the error amplifier  578  acts as a comparator and the first linear regulator  560  is in a state defining an off state. 
     In an implementation, load variations or noise coupling can occur in system  500 . The first linear regulator  560  can monitor the load variations or noise coupling to determine if the output  552  has an undershoot larger than a predetermined value (ΔV 1 ). If the output  550  dips by the predetermined value, such as during a large and fast load current step-up, the hysteretic load transient detector  572  will force an output signal (EN 1 ) to jump from “0” to “1” based on a sensed current value input to the hysteretic load transient detector  572 . In another aspect, a reference voltage of first linear regulator  560  can be switched from steady state reference voltage  562  to transient reference voltage  566 . In an aspect, the signal output by hysteretic load transient detector  572  can control on and off states of the switches ( 564  and  568 ). 
     In an aspect, the steady state reference voltage  562  can be equal to the difference of a reference voltage (V R )  554  of the controller and the predetermined value ΔV 1  or V R −ΔV 1 . In another aspect, transient reference voltage  564  V R ′ can be larger than (VR−ΔV 1 ), equal to or about VR, or a predetermined value. In an implementation, a low-pass filter can be utilized to limit a ramp-up speed of the reference voltage of first linear regulator  560 . Limiting the ramp-up speed can result in a smoother transition. 
     In implementations, when switch  566  is on and the transient reference voltage  564  is utilized, the first linear regulator  560  is activated in system  500  (e.g., the first linear regulator  560  loop is involved in system  500 ). In an aspect, the first linear regulator  560  can then regulate or source the output  550 . The first linear regulator  560  can source the output until the output  550  returns to a steady state (e.g., within a predetermined value of reference voltage  554 ). 
     In implementations, the hysteretic load transient detector  572  can communicate a signal EN 1  set at “1” to the controller  540 . In an aspect, the ratio compensator  544  can increase a duty ratio, such that the current through inductor  522  (denoted I L ) is increased. In another aspect, the ratio compensator  544  can increase the duty ratio relatively quickly and hence the I L  can be increased relatively quickly. 
     In an aspect, the ratio compensator  544  can be an adaptive duty ratio compensator as described below. It is noted that the ratio compensator  544  can utilize various methods of control such as type-I voltage-mode control, type-II voltage-mode control, type-III voltage-mode control, or current-mode control. 
     As the output  550  regulates back to a level defining a steady state (e.g., within a predetermined value of a reference voltage), the current I L  of the inductor  522  approaches the output current (I out )  552 . The hysteretic load transient detector  572  can determine whether or not the output  550  is at a level defining a steady state. When the hysteretic load transient detector  572  determines the output is at a level defining a steady state, the hysteretic load transient detector  572  can change the output signal EN 1  to “0”. In an aspect, the hysteretic load transient detector  572  can then cause switch  568  to turn on and switch  566  to turn off. For example, the hysteretic load transient detector  572  can hand over the control loop from the first linear regulator  560  to a switching converter by selecting a normal duty ratio compensator. 
     In another implementation, the second linear regulator  580  can select steady state reference voltage  582  as a reference voltage by turning switch  588  to an on state (switch  586  off), while in state defining a steady state. In an aspect, when the second linear regulator  580  uses steady state reference voltage  582  the error amplifier  596  acts as a comparator and the second linear regulator  580  is in a state defining an off state, for example, circuitry of the second linear regulator  580  is interrupted. 
     In an implementation, the second linear regulator  580  can monitor the load variations or noise coupling, in system  500 , to determine whether or not the output  552  surpasses an overshoot larger than a predetermined value (ΔV 2 ). If the output  550  rises by the predetermined value ΔV 2 , such as during a large and fast load current step-down, the hysteretic load transient detector  592  will force an output signal (EN 2 ) to jump from “0” to “1” based on a sensed current value input to the hysteretic load transient detector  592 . In another aspect, a reference voltage of second linear regulator  580  can be switched from steady state reference voltage  582  to transient reference voltage  584 . In an aspect, the signal output by hysteretic load transient detector  592  can control on and off states of the switches ( 586  and  588 ). 
     In an aspect, the steady state reference voltage  582  can equal the sum of a reference voltage (V R )  554  of the controller and the predetermined value ΔV 2  or V R +ΔV 2 . In another aspect, transient reference voltage  584  V R ′ can be lower than (V R +ΔV 2 ), equal to or about VR, or a predetermined value. In an implementation, a low-pass filter can be utilized to limit a ramp-down speed of the reference voltage of second linear regulator  580 . Limiting the ramp-down speed can result in a smoother transition. 
     In implementations, when switch  586  is on and the transient reference voltage  584  is utilized, the second linear regulator  580  is activated in system  500  (e.g., the second linear regulator  580  loop is involved in system  500 ). In an aspect, the second linear regulator  580  can then regulate or sink the output  550 . The second linear regulator  580  can sink the output until the output  550  returns to a steady state (e.g., within a predetermined value of reference voltage  554 ). 
     In implementations, the hysteretic load transient detector  592  can communicate a signal EN 2  set at “1” to the controller  540 . In an aspect, the ratio compensator  544  can alter a duty ratio, such that the current through inductor  522  (denoted I L ) is decreased. In another aspect, the ratio compensator  544  can alter the duty ratio relatively quickly and hence I L  can be decreased relatively quickly. 
     As the output  550  regulates back to a level defining a steady state (e.g., within a predetermined value of a reference voltage), the current I L  of the inductor  522  approaches the output current (I out )  552 . The hysteretic load transient detector  592  can determine whether or not the output  550  is at a level defining a steady state. When the hysteretic load transient detector  592  determines the output is at a level defining a steady state, the hysteretic load transient detector  592  can change the output signal EN 2  to “0”. In an aspect, the hysteretic load transient detector  592  can then cause switch  588  to turn on and switch  586  to turn off. For example, the hysteretic load transient detector  592  can hand over the control loop from the second linear regulator  580  to a switching converter by selecting a normal duty ratio compensator. 
       FIG. 6  is an example non-limiting schematic of a system  600  that can function as a hysteretic load transient detector. In an aspect, the system  600  can be utilized by system  500 , system  200 , and/or system  100 . System  600  can be a hysteretic load transient detector such as for a linear regulator (e.g., hysteretic load transient detector  572  of  FIG. 5 ). In implementations, when large load transient occurs, the system  500  can indirectly detect an inductor current (e.g., I L  of systems  200  and  500 ) by sensing a linear regulators&#39; current (e.g., I LR  of systems  200  and  500 ). 
     System  600  can sense a current I S1  of cell  576 . In an aspect, I S1  can be a function of a current I LR1  across a linear regulator. For example, I S1  can be approximately equal to I LR1  divided by N 1 , where N 1  is a positive real number (e.g., 100, 1000, etc.). 
     Before large load transient happens, both I LR1  and I S1  are around 0, and EN 1  is “0”. When large load transient occurs, EN 1  will jump from “0” to “1” once I S1  rises to K 1 ×I R1  where K 1  is a positive real number such as 10 or 20. When V OUT  is being regulated back towards the steady state, I S1  decreases as I L  increases. When I S1  drops to a small reference current of I R1  meaning that I L  almost reaches I OUT , EN 1  will be changed from “1” to “0”. For I S1  in-between I R1  and K 1 ×I R1 , the EN 1  signal maintains its value. 
       FIG. 7  is an example non-limiting schematic of a system  700  that can function as a hysteretic load transient detector. In an aspect, the system  700  can be utilized by system  500 , system  200 , and/or system  100 . In an aspect, system  700  can comprise a hysteretic load transient detector of a linear regulator that sinks a load. For example, system  700  can function as hysteretic load transient detector  592  of  FIG. 5 . In implementations, when large load transient occurs, the system  700  can indirectly detect an inductor current (e.g., I L  of systems  200  and  500 ) by sensing a linear regulators&#39; current (e.g., I LR  of systems  200  and  500 ). 
     In an aspect, the system  700  can sense I S2  of cell  594 . In an aspect, I S2  is proportional to an internal current of a linear regulator (e.g., I LR2  of linear regulator  580 ) and is approximately equal to I LR2 /N 2  where N 2  is a positive real number such as 100 or 1000. Before large load transient happens, both I LR2  and I S2  are around 0, and EN 2  is “0”. When large load transient occurs, EN 2  will jump from “0” to “1” once I S2  rises to K 2 ×I R2  where K 2  is a positive real number such as 10 or 20. When V OUT  is being regulated back towards the steady state, I S2  decreases as I L  decreases. When I S2  drops to a small reference current of I R2  meaning that I L  almost or does reaches I out , EN 2  will be changed from “1” to “0”. For I S2  between I R2  and K 2 ×I R2 , the EN 2  signal maintains its value. 
       FIG. 8  is an example non-limiting schematic of a system  800  that can function as an adaptive duty ratio compensator. In an aspect, the system  800  can be utilized by system  500 , system  200 , and/or system  100 . The system  800  can comprise various components, such as resistors, capacitors, error amplifiers, multiplexers, amplifiers, and the like. For example, system  800  can comprise a resistor (R 1 )  810 , a switch  812 , a resistor  814 , a resistor  816 , a resistor (R 2 )  820 , a switch  822 , a resistor  824 , and a resistor  826 . In an aspect, the system  800  can determine a steady-state resistive division ratio, denoted as “b”, herein. In an implementation, system  800  can calculate b as b=R 2 /(R 1 +R 2 ). 
     Referring to system  500 , when in a steady state both the EN 1  and EN 2  are “0”. Thus both switch  812  and switch  822  are open and the full part of R 1    810  and R 2    820  are used such that the normal duty ratio is generated to regulate V OUT . During large load current step-up when EN 1  is forced to “1” by the hysteretic load transient detector  572  of linear regulator  560 , a portion of R 2    820  is shorted to give a smaller R 2  hence a smaller portion of V OUT  is fed to a negative input-terminal of the error amplifier  830 . As result, the differential input to the error amplifier  830  increases and the voltage at V EA  increases to give a faster increase of the duty ratio. 
     In another implementation, during large load current step-down when EN 2  is forced to “1” by the hysteretic load transient detector  592  of linear regulator  580 , a portion of R 1    810  is shorted to give a smaller R 1    810  hence a larger portion of V OUT  is fed to a negative input-terminal of error amplifier  830 . As result, a differential input to the error amplifier  830  decreases and a voltage at V EA  decreases to give a faster decrease of the duty ratio. 
     In various implementations, system  800  utilizes EN 1  and EN 2  signals to select a maximum and a minimum duty ratio during the load transient period of D 1  and D 2  as described in  FIGS. 3 and 4 , respectively. In another aspect, the inductor current IL during the transient periods can be increased or decreased more quickly, with the price of higher design complexity. Instead of shorting a portion of R 1  or R 2 , it is apparent that the reference voltage b×V R , i.e., the positive input-terminal of an error amplifier can be adjusted to achieve the similar effect of duty ratio changes. 
       FIG. 9  is an example non-limiting schematic of a system  900  that can function as an adaptive duty ratio compensator. In an aspect, the system  900  can be utilized by system  500 , system  200 , and/or system  100 . In an aspect, system  900  functions similarly to system  800 . However, system  900  does not utilize EN 1  and EN 2  signals to select a maximum and a minimum duty ratio during the load transient period of D 1  and D 2 . 
       FIG. 10  is an example non-limiting schematic of a system  1000  that comprises linear regulators and a controller with undershoot fast-recovery and overshoot protection-only applied to a single phase hybrid buck converter. In an aspect, system  1000  can comprise a controller  1020 , a linear regulator  1030 , a linear regulator  1040 , and various other components. It is noted that aspects of system  1000  can perform similar and/or identical to aspects of systems  100 ,  200 , and  500  as described above. For example, the linear regulator  1030  can function similarly and/or identically to the first linear regulator  260  of  FIG. 2 . 
     In an implementation, the linear regulator  1040  can utilize a single reference voltage (depicted as the sum of V R +ΔV 2 ). Accordingly, the linear regulator  1040  need not have a reference selection network, hysteretic load transient detector, and/or various other components. In an aspect, the linear regulator  1040  can determine whether or not an output is overshooting larger than a predefined value (e.g., ΔV 2 ). If the linear regulator  1040  determines that the output is overshooting larger than ΔV 2 , then the linear regulator  1040  can sink current from an output load to an output capacitor. 
     In another aspect, since the linear regulator  1040  does not contain a reference selection network, the linear regulator does not need to send a signal indicating a start and end of a transient period to the controller  1020 . Hence, the controller  1020  can be configured to receive only signal(s) indicating a start and end of a transient period, such as from the linear regulator  1030 . 
       FIG. 11  is an example non-limiting schematic of a system  1100  that comprises a linear regulator and a controller with undershoot fast-recovery and an over voltage protection logic applied to a single phase hybrid buck converter. In an aspect, system  1100  can comprise a controller  1120 , a linear regulator  1130 , an over voltage protection component  1140 , and various other components. It is noted that aspects of system  1100  can perform similar and/or identical to aspects of systems  100 ,  200 ,  500 , and  1000  as described above. For example, the linear regulator  1130  can function similarly and/or identically to the first linear regulator  260  of  FIG. 2 . 
     In an aspect, the over voltage protection component  1140  can be configured to detect a predefined output overshoot voltage using a comparator  1148  and an over voltage protection logic component  1144  to provide a control signal to the controller to make one or more inductors accumulate less charge to the output load. It is noted that the over voltage protection component  1140  can comprise a hysteretic comparator whose output is used to control a switching converter to accumulate less charge to an output. 
       FIG. 12  is an example non-limiting schematic of a system  1200  that comprises a linear regulator and a controller with undershoot prevention-only and an over voltage protection logic applied to a single phase hybrid buck converter. In an aspect, system  1200  can comprise a controller  1220 , a linear regulator  1230 , an over voltage protection component  1240 , and various other components. It is noted that aspects of system  1200  can perform similar and/or identical to aspects of systems  100 ,  200 ,  500 ,  1000 , and  1100  as described above. For example, the over voltage protection component  1240  can function similarly and/or identically to the over voltage protection component  1140  of  FIG. 11 . 
     In an implementation, the linear regulator  1230  can be configured to prevent an output from undershooting larger than a predetermined value (ΔV 1 ). The linear regulator  1230  can determine whether or not an output voltage is undershooting larger than ΔV 1 . In an aspect, the linear regulator  1230  can utilize a single reference voltage (depicted as the sum of V R −ΔV 1 ). Accordingly, the linear regulator  1230  need not have a reference selection network, hysteretic load transient detector, and/or various other components. In an aspect, if the linear regulator  1230  determines that the output is undershooting larger than ΔV 1 , then the linear regulator  1230  can source current to the output. 
       FIG. 13  is an example non-limiting schematic of a system  1300  that comprises linear regulators and a controller with undershoot prevention-only and overshoot fast-recovery applied to a single phase hybrid buck converter. In an aspect, system  1300  can comprise a controller  1320 , a linear regulator  1330 , a linear regulator  1340 , and various other components. It is noted that aspects of system  1300  can perform similar and/or identical to aspects of systems  100 ,  200 ,  500 ,  1000 ,  1100 , and  1200  as described above. For example, the linear regulator  1330  can function similarly and/or identically to the linear regulator  1230  of  FIG. 12 , and the linear regulator  1340  can function similarly and/or identically to the second linear regulator  580  of  FIG. 5 . 
     In an implementation, the controller  1320  can be configured to receive a signal from the linear regulator  1340  without receiving a signal from the linear regulator  1330 . Accordingly, a ratio compensator can be simplified to receive only one control signal form the linear regulator  1340 . 
       FIG. 14  is an example non-limiting schematic of a system  1400  that comprises linear regulators and a controller with undershoot prevention-only and overshoot prevention-only applied to a single phase hybrid buck converter. In an aspect, system  1400  can comprise a controller  1420 , a linear regulator  1430 , a linear regulator  1440 , and various other components. It is noted that aspects of system  1400  can perform similar and/or identical to aspects of systems  100 ,  200 ,  500 ,  1000 ,  1100 ,  1200 , and  1300  as described above. For example, the linear regulator  1330  can function similarly and/or identically to the linear regulator  1230  of  FIG. 12 , and the linear regulator  1440  can function similarly and/or identically to the linear regulator  1040  of  FIG. 10 . 
     In an aspect, the controller  1420  can be configured such that the linear regulators do not send a control signal. In an aspect, a ratio compensator of the controller  1420  can be simplified such that adjustment of a resistive division ratio or a reference voltage is based on a reference voltage and not a control signal from linear regulators. 
       FIG. 15  is an example non-limiting schematic of a system  1500  that comprises linear regulators applied to a multi-phase hybrid buck converter. In an aspect, system  1500  can comprise a controller  1510 , linear regulator(s)  1520 , voltage references  1530 , a multi-phase buck converter  1540 , and various other components. It is noted that aspects of system  1500  can perform similar and/or identical to aspects of systems  100 ,  200 ,  500 ,  1000 ,  1100 ,  1200 ,  1300 , and  1400  as described above. For example, linear regulators  1520  can comprise linear regulator  268  of system  200 , first linear regulator  560  and second linear regulator  580  of system  500 , and/or various linear regulators and voltage protection components. It is noted that system  1500  can comprise undershoot prevention-only and/or overshoot prevention-only as described herein. 
     In an aspect, multi-phase pure buck converter  1540  can apply various aspects disclosed herein to control transient responses arriving at multi-phase hybrid buck converter  1540 . In an aspect, the controller  1510  can be configured with additional drivers and clock signals to accommodate for the operation of different phases. In another aspect, the references  1530  can comprises various references described herein. It is noted that the controller  1510  and references  1530  can be configured based on the linear regulator(s)  1520  selected for utilization and/or the number of phases of the multi-phase buck converter  1540 . 
     In implementations, multiphase buck converter  1540  can comprise basic buck converters placed in parallel between an input and a load. In an aspect, the controller can turn on/off each n phases at intervals over a switching period. In an aspect, the multiphase buck converter  1540  can comprise one or more switches. In an example, the one or more switches can be configured in parallel with one or more inductors, diodes, resistors and the like. It is noted that the configuration of switches and/or various components can depend on a desired number of n phases. 
       FIGS. 16-18  illustrate methods  1600 ,  1700 , and  1800  that facilitate voltage regulating in a semiconductor device. For simplicity of explanation, the methods (or procedures) are depicted and described as a series of acts. It is noted that the various embodiments are not limited by the acts illustrated and/or by the order of acts. For example, acts can occur in various orders and/or concurrently, and with other acts not presented or described herein. 
       FIG. 16  illustrated is an example non-limiting process flow diagram of a method  1600  that facilitates voltage regulation and current sourcing. The voltage regulation can be performed by various implementations described herein. 
     At  1602 , a system can monitor an output load voltage by a switching converter. For example, a linear regulator and/or the like can monitor a voltage of an output. 
     At  1604 , a system can determine whether or not the output load voltage has a value a defined amount lower than a reference value. In an aspect, a reference value can be a predetermined value and a system, such as a linear regulator, can compare the output to the predetermined value. 
     At  1606 , a system can source current from a linear regulator to the output load. In implementations, a linear regulator can provide current to an output and/or output capacitor. In an aspect, the provided current can increase an output. 
     At  1608 , a system can accumulate charge at an inductor of a switching converter and deliver the charge to the output load. In implementations, a switching converter can charge an inductor and a controller can manage the switching converter to charge the inductor based on a signal from a linear regulator. 
     At  1610 , a system can monitor an output load voltage. For example, a linear regulator and/or the like can monitor a voltage of an output. 
     At  1612 , a system can determine whether or not the output load voltage has a value that defines a steady-state. For example, a linear regulator can determine whether or not the output load has a value meeting a predefined steady-state threshold. 
     At  1614 , a system can stop sourcing current from a linear regulator. For example, a linear regulator can be deactivated such that current is not communicated from a linear regulator to an output load. 
       FIG. 17  illustrates an example non-limiting process flow diagram of a method  1700  that facilitates voltage regulation and current sinking. The voltage regulation can be performed by various implementations described herein. 
     At  1702 , a system can monitor a voltage of an output load output by a switching converter. For example, a linear regulator, over voltage protection component, and/or the like can monitor a voltage of an output. 
     At  1704 , a system can determine whether or not the voltage of the output load has a value a defined amount higher than a reference value. In an aspect, a reference value can be a predetermined value and a system, such as a linear regulator, can compare the output to the predetermined value. 
     At  1706 , a system can sink current to a linear regulator from the output load (output capacitor and output). In implementations, a linear regulator can sink current from an output and/or output capacitor. In an aspect, the provided current can decrease an output. 
     At  1708 , a system can decrease a charge at an inductor of a switching converter and deliver the charge to the output load. In implementations, a switching converter can reduce charge supplied to an inductor and a controller can manage the switching converter to reduce the charge of the inductor based on a signal from a linear regulator and the like. 
     At  1710 , a system can monitor an output load voltage. For example, a linear regulator, over voltage protection component, and/or the like can monitor a voltage of an output. 
     At  1712 , a system can determine whether or not the output load voltage has a value that defines a steady-state. For example, a linear regulator can determine whether or not the output load has a value meeting a predefined steady-state threshold. 
     At  1714 , a system can stop sinking current to a linear regulator. 
       FIG. 18  illustrated is an example non-limiting process flow diagram of a method  1800  that facilitates voltage regulation in a system. The voltage regulation can be performed by various implementations described herein. 
     At  1802 , a system can coordinate states of a plurality of switches in a multi-phase switching converter to accumulate charge at a plurality of inductor. For example, a controller can instruct switches in a switching converter to alter states (e.g., on/off). 
     At  1804 , a system can regulate an output load to a defined output voltage by accumulating charge at the plurality of inductors based on the coordinated states of the plurality of switches. In an aspect, a controller can alter states of a plurality of switches to complete circuit paths that include an inductor. 
     At  1806 , a system can sense a voltage of the output load. For example, a linear regulator, over voltage protection component, switching converters, and the like can sense the voltage of the output load. 
     At  1808 , a system can determine whether or not the voltage of the output load has a value a first defined amount lower than a first reference value or a second defined amount higher than a second reference value. For example, the first defined amount lower than the first reference determining can define an output undershoot voltage threshold. As another example, the second defined amount higher than second reference value can define an output overshoot voltage threshold. In implementations, linear regulators, over voltage protection component, and the like can determine whether or not the voltage of the output load is at a level defining determining whether or not the voltage of the output load is at a level defining at least one of an output undershoot voltage threshold or an output overshoot voltage threshold. In an aspect, the output undershoot voltage threshold can be a defined voltage lower than a voltage reference. In another aspect, the output overshoot voltage threshold can be a defined voltage higher than a voltage reference. 
     The above description of illustrated aspects and embodiments, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed aspects and embodiments to the precise forms disclosed. While specific aspects and embodiments and examples are described herein for illustrative purposes, various modifications are possible that are considered within the scope of such aspects and embodiments and examples, as those skilled in the relevant art can recognize. 
     As used herein, the word “example” is used herein to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter described herein is not limited by such examples. In addition, any aspect or design described herein as an “example” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent structures. 
     It is noted that designs described herein can be applied to other hybrid buck converters. For clarity, the examples are based on single phase hybrid buck converter and multi-phase buck converters. It is noted that variations to modify the design to make other combinations and forms of designs. For example, various linear regulators, controllers, hysteretic load transient detectors, switches, converters, circuitry, and other components can be utilized in various implementations. 
     The terms “first,” “second,” “third,” “fourth,” and the like in the description and the claims, if any, may be used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable. 
     Furthermore, to the extent that the terms “includes,” “has,” “contains,” and other similar words are used in either the detailed description or the claims, such terms are intended to be inclusive—in a manner similar to the term “comprising” as an open transition word—without precluding any additional or other elements. 
     With respect to any numerical range for a given characteristic, a parameter from one range may be combined with a parameter from a different range from the same characteristic to generate a numerical range. Other than where otherwise indicated, all numbers, values, and/or expressions referring to quantities of ingredients, reaction conditions, etc., used in the specification and claims are to be understood as modified in all instances by the term “about.” 
     In this regard, while the described subject matter has been described in connection with various aspects and embodiments and corresponding Figures, where applicable, it is to be understood that other similar aspects and embodiments can be used or modifications and additions can be made to the described aspects and embodiments for performing the same, similar, alternative, or substitute function of the disclosed subject matter without deviating therefrom. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in breadth and scope in accordance with the appended claims.