Patent Publication Number: US-2021194371-A1

Title: Discontinuous conduction mode (dcm) voltage regulator circuit with reduced output voltage ripple

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/378,412, entitled “DISCONTINUOUS CONDUCTION MODE (DCM) VOLTAGE REGULATOR CIRCUIT WITH REDUCED OUTPUT VOLTAGE RIPPLE” filed on Apr. 8, 2019, and claims priority to the Ser. No. 16/378,412 application. The entire contents of the Ser. No. 16/378,412 application is incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the present invention relate generally to the technical field of electronic circuits, and more particularly to a discontinuous conduction mode (DCM) voltage regulator circuit. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in the present disclosure and are not admitted to be prior art by inclusion in this section. 
     Discontinuous conduction mode (DCM) voltage regulators (e.g., direct current (DC)-DC converters) have high efficiency at low output currents. It is desirable to have low ripple of the output voltage generated by the DCM voltage regulator. Existing techniques to mitigate voltage ripple in DCM voltage regulators include having two DCM phases with a 180 degree phase shift, and increasing the capacitance at the output. Having two DCM phases with a 180 degree phase shift requires increased complexity in the controller and lower efficiency. Additionally, increasing the output capacitance requires significant area overhead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings. 
         FIG. 1  illustrates a voltage regulator circuit including two or more discontinuous mode (DCM) phases, in accordance with various embodiments. 
         FIG. 2A  illustrates a graph of the inductor currents in a first DCM phase and a second DCM phase, in accordance with various embodiments. 
         FIG. 2B  illustrates a graph of the total inductor current at the output of the voltage regulator circuit, in accordance with various embodiments. 
         FIG. 2C  illustrates a graph of the output voltage of the voltage regulator circuit, in accordance with various embodiments. 
         FIG. 3  illustrates control circuitry that may be included in the voltage regulator circuit of  FIG. 1 , in accordance with various embodiments. 
         FIG. 4  illustrates an example system configured to employ the apparatuses and methods described herein, in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents. 
     Various operations may be described as multiple discrete actions or operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations may not be performed in the order of presentation. Operations described may be performed in a different order than the described embodiment. Various additional operations may be performed and/or described operations may be omitted in additional embodiments. 
     The terms “substantially,” “close,” “approximately,” “near,” and “about,” generally refer to being within +/−10% of a target value. Unless otherwise specified the use of the ordinal adjectives “first,” “second,” and “third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner. 
     For the purposes of the present disclosure, the phrases “A and/or B” and “A or B” mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C). 
     The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous. 
     As used herein, the term “circuitry” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), a combinational logic circuit, and/or other suitable hardware components that provide the described functionality. As used herein, “computer-implemented method” may refer to any method executed by one or more processors, a computer system having one or more processors, a mobile device such as a smartphone (which may include one or more processors), a tablet, a laptop computer, a set-top box, a gaming console, and so forth. 
     Various embodiments provide a voltage regulator circuit including two or more discontinuous conduction mode (DCM) phases coupled to an output node and coupled in parallel with one another. A control circuit may detect a trigger and switch all of the two or more DCM phases to a first state (charge state) responsive to the detection. The control circuit may switch a first DCM phase, of the two or more DCM phases, to a second state (discharge state) after a first predetermined time period in the first state and may switch a second DCM phase, of the two or more DCM phases, to the second state after a second predetermined time period in the first state, wherein the second predetermined time period is different than the first predetermined time period. 
     The control circuit may switch the two or more DCM phases to the first state responsive to any suitable trigger, such as a detection that the output voltage is below a threshold voltage, the output of an error amplifier coupled to the output node, and/or the expiration of a timer (e.g., indicating a time period has elapsed since the last cycle of the DCM phases). 
     One benefit of techniques described herein is load management. During the initial phase when the first and second DCM phases are in the first state (e.g., the respective pull-up transistors are building current through the inductors), the resulting current delivered to the load will have a slope twice as fast as it would be if a single inductor were driving the load. Then, when the first DCM phase switches to the second state while the second DCM phase remains in the first state, the discharging of the second DCM phase may cancel out the charging of the first DCM phase, and the resulting current delivered to the load may be a DC-like current (e.g., substantially constant). When the second DCM phase switches to the second state, the first DCM phase may have already switched to a third state (e.g., tri-state mode, with both the pull-up transistor and pull-down transistor off). Accordingly, only one inductor is left to discharge and it will do so at a slower rate than if multiple inductors were discharging at the same time. This will, in turn, help avoid ripple at the output node and manage the charge and discharge of the output capacitor. 
       FIG. 1  illustrates a voltage regulator circuit  100  (hereinafter “circuit  100 ”), in accordance with various embodiments. The circuit  100  may include two or more discontinuous conduction mode (DCM) phases  102   a - b  coupled in parallel with one another to generate a regulated output voltage at an output node  104 . The regulated output voltage may be provided to a load  106 . The load  106  may be, for example, a circuit block that uses the regulated output voltage as a power supply. The circuit  100  may further include a control circuit  108  coupled to the DCM phases  102  to control operation of the DCM phases. For example, in some embodiments, the control circuit  108  may control operation of the DCM phases based on the output voltage and/or based on one or more timers, as further discussed herein. 
     Individual DCM phases  102   a - b  may include a driver circuit  110   a - b  (also referred to as a bridge circuit) coupled to an inductor  112   a - b . In some embodiments, the inductor  112   a - b  of the respective DCM phase  102   a - b  may be coupled between the output node  104  and an internal node  114   a - b  of the driver circuit  110   a - b . The driver circuit  110   a - b  may include a pull-up transistor  116   a - b  (also referred to as a high side transistor) coupled between the internal node  114   a - b  and a supply rail  118   a - b . The supply rail  118   a - b  may receive a supply voltage (e.g., Vin), which may be a DC voltage. The driver circuit  110   a - b  may further include a pull-down transistor  120   a - b  (also referred to as a low side transistor) coupled between the internal node  114   a - b  and a ground terminal  122   a - b . The supply rails  118   a - b  and/or ground terminals  122   a - b  of the respective driver circuits  110   a - b  may be the same and/or coupled to one another. 
     Additionally, other embodiments of the DCM phases  102   a - b  may include a different design, additional components, and/or a different configuration of the driver circuit  110   a - b  and/or inductor  112   a - b , such as one or more additional transistors coupled between the supply rail  118   a - b  and the internal node  114   a - b  (e.g., in a cascode arrangement) and/or one or more additional transistors coupled between the internal node  114   a - b  and the ground terminal  122   a - b.    
     In various embodiments, the control circuit  108  may provide respective control signals to the gate terminals of the pull-up transistors  116   a - b  and/or pull-down transistors  120   a - b  to control a state of the respective DCM phases  102   a - b . For example, when the DCM phase  102   a - b  is in a first state (e.g., charge state), the control circuit  108  may turn on the respective pull-up transistor  116   a - b  and turn off the respective pull-down transistor  120   a - b . Accordingly, the output node  104  may be coupled to the supply rail  118   a - b  via the inductor  112   a - b  and pull-up transistor  116   a - b  of the respective DCM phase  102   a - b , thereby causing the current supplied from the DCM phase  102   a - b  to the output node  104  via the inductor  112   a - b  to increase. 
     When the DCM phase  102   a - b  is in a second state (e.g., discharge state), the control circuit  108  may turn off the respective pull-up transistor  116   a - b  and turn on the respective pull-down transistor  120   a - b . Accordingly, the output node  104  may be coupled to the ground terminal  122   a - b  via the inductor  112   a - b  and pull-down transistor  120   a - b  of the respective DCM phase  102   a - b , thereby causing the current supplied from the DCM phase  102   a - b  to the output node  104  via the inductor  112   a - b  to decrease. When the DCM phase  102   a - b  is in a third state (e.g., tri-state mode or standby mode), both the respective pull-up transistor  116   a - b  and pull-down transistor  120   a - b  may be off. Accordingly, the output node  104  may be uncoupled from both the supply rail  118   a - b  and the ground terminal  122   a - b.    
     Operation of the circuit  100  will be described with reference to the graph  200   a  of  FIG. 2A , graph  200   b  of  FIG. 2B , and graph  200   c  of  FIG. 2C . Graph  200   a  illustrates a first inductor current  202  that corresponds to the current through inductor  114   a  of DCM phase  102   a , and a second inductor current  204  that corresponds to the current through inductor  114   b  of DCM phase  102   b . Graph  200   b  illustrates a total output current  206  generated by the combination of the DCM phases  102   a - b . Graph  200   b  also illustrates an equivalent DC current  208 . Graph  200   c  illustrates an output voltage  210  generated by the combination of DCM phases  102   a - b  (e.g., the output voltage at the output node  104 ). 
     In various embodiments, when the control circuit  108  detects a trigger, the control circuit  108  may place all (e.g., both) the DCM phases  102   a - b  in the first state (charge state). The trigger may include one or more parameters. For example, the trigger may include that the output voltage has decreased below a threshold voltage. Alternatively, or additionally, the trigger may include a more complex feedback based on the output voltage, such as based on the output of an error amplifier (e.g., using a compensator and/or pulse width modulator). Other embodiments may alternatively or additionally use a timer to trigger the control circuit to switch all the DCM phases  102   a - b  to the first state after a certain time period has passed since the last cycle of the DCM phases  102   a - b . Although embodiments herein are described mainly with reference to triggering the DCM phases  102   a - b  to switch to the first state based on the output voltage falling below a threshold, it will be apparent that many different suitable criteria or combinations of criteria may be used to determine when to switch the DCM phases  102   a - b  to the first state. 
     When the DCM phases  102   a - b  are switched to the first state, the pull-up transistors  116   a - b  may be turned on and the pull-down transistors  120   a - b  may be off. This is shown at time t 0  in graphs  200   a - c . The first inductor current  202  and second inductor current  204  both increase while the respective DCM phases  102   a - b  are in the first state. The total output current  206  may be the sum of the inductor currents  202  and  204 . Accordingly, the total output current  206  may increase faster than the inductor current of a single phase (e.g., twice as fast for embodiments with two phases  102   a - b ). This may cause the output voltage  210 , which is dropping in value, to more quickly recover and lead to less voltage droop than if a single phase were charging the output node  104 . As shown in  FIG. 2C , the output voltage may reach its lowest voltage level at time t 1 . 
     In various embodiments, the first DCM phase  102   a  may be in the first state (e.g., with the pull-up transistor  116   a  on) for a first time period. The time period β may be a set (e.g., programmed and/or pre-defined) time period. The second DCM phase  102  may be in the first state (e.g., with the pull-up transistor  116   b  on) for a second time period that is less than the first time period. For example, the first time period may be β, and the second time period may be α*β, where α is less than 1. In some embodiments, a may be any suitable value, such as 0.75 or less, or 0.5 or less. Graphs  200   a - c  illustrate an embodiment in which a is 0.5 (with the second time period being half as long as the first time period). 
     Accordingly, at time t 2 , which may be α*β (e.g., in nanoseconds) after time t 0 , the control circuit  108  may switch the second DCM phase  102   b  from the first state to the second state (e.g., with the pull-up transistor  116   b  off and the pull-down transistor  120   b  on), while the first DCM phase  102   a  remains in the first state. Accordingly, the second inductor current  204  may decrease, while the first inductor current  202  may continue to increase. In some embodiments, the decreasing slope of the second inductor current  204  may be substantially the opposite of the increasing slope of the first inductor current  202 . Accordingly, the total output current  206  may be substantially constant for a time period after time t 2  (e.g., the time period during which the first DCM phase  102   a  is in the first state and the second DCM phase  102   b  is in the second state). 
     At time t 3 , which may be β (e.g., in nanoseconds) after time t 0 , the control circuit  108  may switch the first DCM phase  102   a  from the first state to the second state (e.g., with the pull-up transistor  116   a  off and the pull-down transistor  120   a  on). Accordingly, the first inductor current  202  may begin to decrease. In some embodiments, the control circuit  108  may determine that the first DCM phase  102   a  should stay in the first state beyond the first predetermined time period under some circumstances, for example, based on the output voltage when the first predetermined time period expires. 
     In various embodiments, when the second inductor current  204  reaches zero, the control circuit  108  may switch the second DCM phase  102   b  from the second state to the third state (e.g., the pull-down transistor  120   b  may be turned off while the pull-up transistor  116   b  remains off). This transition is shown at time t 3  in  FIG. 2A . However, the second DCM phase  102   b  may not necessarily be switched to the third state at the same time that the first DCM phase  102   a  is switched to the second state. For example, the second time period for which the second DCM phase  102   b  is in the first state may not be half of the first time period for which the first DCM phase  102   a  is in the first state. Additionally, or alternatively, the time it takes for the second inductor current  204  to reach zero after switching from the first state to the second state may not be the same as the amount of time that the second DCM phase  102   b  is in the first state. 
     With the second inductor current  204  at zero and the first DCM phase  102   a  in the second state, the total output current  206  may decrease at a slower rate than the rate at which the total output current  206  increased between t 0  and t 2  (e.g., with both the first and second DCM phases  102   a - b  in the first state). The output voltage  210  may continue increasing until time t 4 , at which the output voltage  210  peaks and begins to decrease. 
     At time t 5 , the first inductor current  202  may reach zero. In response, the control circuit  108  may switch the first DCM phase  102   b  from the second state to the third state (e.g., the pull-down transistor  120   a  may be turned off while the pull-up transistor  116   a  remains off). 
     The first and second DCM phases  102   a - b  may remain in the third state until the next instance of the trigger (e.g., when the output voltage  210  again drops below the threshold), which is shown at time t 6 ). Then the first and second DCM phases  102   a - b  may again be placed in the first state at the same time, and the process described above may be repeated. 
     In some embodiments, the control circuit  108  may switch the DCM phase  102   a  and/or  102   b  from the second state to the first state (without entering the third state in between) under some circumstances, such as if another trigger (which may be the same or different from the prior trigger) occurs while the DCM phase  102   a  and/or  102   b  is in the second state. 
     As can be seen in graph  200   c , the voltage undershoots of the output voltage  208  may be quickly mitigated by both of the DCM phases  102   a - b  being switched on (e.g., in the first state) when the output voltage  208  drops below the threshold. Additionally, a large voltage overshoot of the output voltage  208  may be avoided by having the second DCM phase  102   b  switch to the second state (discharge state) before the first DCM phase  102   a  (e.g., causing the negative slope of the second inductor current  204  to at least partially cancel out the positive slope of the first inductor current  202 . 
       FIG. 3  illustrates a control circuit  300  that may be one example implementation of the control circuit  108 , in accordance with various embodiments. The control circuit  300  triggers the associated DCM phases to switch to the first state based on the output voltage provided by the DCM phases dropping below a threshold. It will be apparent that other embodiments may use other designs and/or modifications of the control circuit  108 , whether based on the same trigger and/or based on one or more other triggers. 
     Control circuit  300  may include a PFM controller  302  and a phase controller  304 . The PFM controller  302  may generate control signals to control the respective pull-up transistors  116   a - b  and pull-down transistors  120   a - b  of the DCM phases  102   a - b . The phase controller  304  may level-shift and/or otherwise adapt the control signals to properly control the pull-up transistors  116   a - b  and pull-down transistors  120   a - b.    
     In various embodiments, the PFM controller  302  may include a comparator  306  to compare the output voltage Vout (e.g., fed back from the output node  104 ) to a reference voltage Vref. The output of the comparator  306  may be coupled to a set (S) input of a set/reset (SR) latch  308 . The SR latch  308  may catch the rising edge of the comparator  306  when the output voltage Vout falls below the reference voltage Vref, causing the output of the SR latch  308  to switch from logic 0 to logic 1. The SR latch  308  may isolate the rest of the PFM controller  302  from noise at the comparator output. 
     The output of the SR latch  308  may be coupled to the input of flip-flops  310   a - b . The output of flip-flop  310   a  may be passed to the phase controller as control signal HSS 0  to control the pull-up transistor  116   a  of the DCM phase  102   a , while the output of flip-flop  310   b  may be passed to the phase controller as control signal HSS 1  to control the pull-up transistor  116   b  of the DCM phase  102   b . Accordingly, the transition in the output of the SR latch  308  responsive to the output of the comparator  306  will cause both of the flip-flops  310   a - b  to generate respective control signals HSS 0  and HSS 1  that will turn on both of the pull-up transistors  116   a - b.    
     Each of the flip-flops  310   a - b  includes a feedback path with a respective delay cell  312   a - b  coupled between the output and the reset terminal of the respective flip-flop  310   a - b . The delay provided by the delay cells  312   a - b  may correspond to the length of time that the respective DCM phases  102   a - b  will be in the first state. Accordingly, the delay cell  312   a  may provide a longer delay than the delay cell  312   b . The flip-flops  310   a - b  may reset after the delay provided by the respective delay cell  312   a - b , thereby causing the respective control signal HSS 0  and HSS 1  to turn off the respective pull-up transistor  116   a - b.    
     Additionally, the PFM controller  302  may include low-side logic  314   a - b  to generate respective control signals LSS 0  and LSS 1  to control the respective pull-down transistors  120   a - b  of DCM phases  102   a - b . Low side logic  314   a - b  may include an inverter  316   a - b  to receive the output of the respective flip-flop  310   a - b  and pass its inverted output to the input terminal of a flip-flop  318   a - b . The output of the flip-flops  318   a - b  may be passed to the phase controller  304  as the respective control signals LSS 0  and LSS 1 . Accordingly, the reset of the flip-flops  310   a - b  may also cause the respective flip-flop  318   a - b  to turn on the respective pull-down transistor  120   a - b , thereby switching the respective DCM phase from the first state to the second state. 
     The flip-flops  318   a - b  may include a feedback path with a respective delay cell  320   a - b  coupled between the output and the reset terminal of the flip-flop  318   a - b , thereby causing the flip-flop  318   a - b  to reset after a period of time. The corresponding change in the respective control signal LSS 0  or LSS 1  may trigger the phase controller  304  to monitor the inductor current of the respective DCM phase  102   a - b  and switch the DCM phase  102   a - b  to the third state (e.g., turn off the pull-down transistor  120   a - b ) when the inductor current reaches zero. In other embodiments, the phase controller  304  may monitor the inductor current and switch the DCM phase  102   a - b  to the third state independently of the reset of the flip-flops  318   a - b.    
     The feedback path of the flip-flop  318   a  via delay cell  320   a  may also be fed back to the reset terminal of the SR latch  306 . Accordingly, the feedback may reset the SR latch  306 , thereby enabling the SR latch  308  to again respond to a change in the output of the comparator  306  (e.g., at the next time that the output voltage drops below the reference voltage). 
       FIG. 4  illustrates an example computing device  400  that may employ the apparatuses and/or methods described herein (e.g., circuit  100 , the signals of  FIGS. 2A-C , and/or control circuit  300 , etc.), in accordance with various embodiments. As shown, computing device  400  may include a number of components, such as one or more processor(s)  404  (one shown) and at least one communication chip  406 . In various embodiments, the one or more processor(s)  404  each may include one or more processor cores. In various embodiments, the at least one communication chip  406  may be physically and electrically coupled to the one or more processor(s)  404 . In further implementations, the communication chip  406  may be part of the one or more processor(s)  404 . In various embodiments, computing device  400  may include printed circuit board (PCB)  402 . For these embodiments, the one or more processor(s)  404  and communication chip  406  may be disposed thereon. In alternate embodiments, the various components may be coupled without the employment of PCB  402 . 
     Depending on its applications, computing device  400  may include other components that may or may not be physically and electrically coupled to the PCB  402 . These other components include, but are not limited to, memory controller  405 , volatile memory (e.g., dynamic random access memory (DRAM)  408 ), non-volatile memory such as read only memory (ROM)  410 , flash memory  412 , storage device  411  (e.g., a hard-disk drive (HDD)), an I/O controller  414 , a digital signal processor (not shown), a crypto processor (not shown), a graphics processor  416 , one or more antenna  418 , a display (not shown), a touch screen display  420 , a touch screen controller  422 , a battery  424 , an audio codec (not shown), a video codec (not shown), a global positioning system (GPS) device  428 , a compass  430 , an accelerometer (not shown), a gyroscope (not shown), a speaker  432 , a camera  434 , and a mass storage device (such as hard disk drive, a solid state drive, compact disk (CD), digital versatile disk (DVD)) (not shown), and so forth. In various embodiments, the processor  404  may be integrated on the same die with other components to form a System on Chip (SoC). 
     In some embodiments, the one or more processor(s)  404 , flash memory  412 , and/or storage device  411  may include associated firmware (not shown) storing programming instructions configured to enable computing device  400 , in response to execution of the programming instructions by one or more processor(s)  404 , to practice all or selected aspects of the methods described herein. In various embodiments, these aspects may additionally or alternatively be implemented using hardware separate from the one or more processor(s)  404 , flash memory  412 , or storage device  411 . 
     In various embodiments, one or more components of the computing device  400  may include circuit  100  and/or control circuit  300 , use the signals of  FIGS. 2A-C , and/or otherwise employ techniques described herein. For example, the processor  404 , communication chip  406 , I/O controller  414 , memory controller  405 , and/or another component of computing device  400  may include circuit  100  and/or control circuit  300 , use the signals of  FIGS. 2A-C , and/or otherwise employ techniques described herein. 
     The communication chips  406  may enable wired and/or wireless communications for the transfer of data to and from the computing device  400 . The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip  406  may implement any of a number of wireless standards or protocols, including but not limited to IEEE 702.20, Long Term Evolution (LTE), LTE Advanced (LTE-A), 5G, General Packet Radio Service (GPRS), Evolution Data Optimized (Ev-DO), Evolved High Speed Packet Access (HSPA+), Evolved High Speed Downlink Packet Access (HSDPA+), Evolved High Speed Uplink Packet Access (HSUPA+), Global System for Mobile Communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless Telecommunications (DECT), Worldwide Interoperability for Microwave Access (WiMAX), Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device  400  may include a plurality of communication chips  406 . For instance, a first communication chip  406  may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth, and a second communication chip  406  may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others. 
     In various implementations, the computing device  400  may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a computing tablet, a personal digital assistant (PDA), an ultra-mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit (e.g., a gaming console or automotive entertainment unit), a digital camera, an automobile, a medical device, an appliance, a portable music player, a digital video recorder, an electronic sensor, a smart home device, an internet of things (IoT) device, etc. In further implementations, the computing device  400  may be any other electronic device that processes data. 
     Some non-limiting Examples of various embodiments are provided below. 
     Example 1 is a circuit comprising: a first discontinuous conduction mode (DCM) phase coupled with an output node; a second DCM phase coupled with the output node and coupled in parallel with the first DCM phase, wherein the first and second DCM phases are operable in a first state in which the output node is coupled to a supply rail via an inductor of the respective first or second DCM phase and a second state in which the output node is coupled to a ground terminal via the inductor of the respective first or second DCM phase; and a control circuit coupled with the first and second DCM phases. The control circuit is to: control, in response to a trigger, the first DCM phase and the second DCM phase to be in the first state concurrently; and switch the first DCM phase to the second state upon expiration of the first period of time from the trigger; and switch the second DCM phase to the second state upon expiration of the second period of time from the trigger, wherein the second period of time is less than the first period of time. 
     Example 2 is the circuit of Example 1, wherein the trigger includes: a detection that the output voltage is below a threshold; an output of an error amplifier coupled to the output node; or expiration of a timer. 
     Example 3 is the circuit of Example 1, wherein the first and second DCM phases are further operable in a third state in which the output node is uncoupled from the supply rail and the ground terminal via the inductor of the respective first or second DCM phase, wherein the control circuit is further to: switch the first DCM phase to the third state when a first current through the inductor of the first DCM phase reaches zero; and switch the second DCM phase to the third state when a second current through the inductor of the second DCM phase reaches zero. 
     Example 4 is the circuit of Example 3, wherein the first and second DCM phases each include: the inductor coupled between the output node and an internal node; a pull-up transistor coupled between the internal node and the supply rail; and a pull-down transistor coupled between the internal node and the ground terminal; wherein: when the respective DCM phase is in the first state, the pull-up transistor is on and the pull-down transistor is off; when the respective DCM phase is in the second state, the pull-up transistor is off and the pull-down transistor is on; and when the respective DCM phase is in the third state, the pull-up transistor is off and the pull-down transistor is off. 
     Example 5 is the circuit of Example 1, wherein the trigger is a first trigger, and wherein the control circuit is further to: switch, responsive to a second trigger after expiration of the first period of time, the first and second DCM phases from the second state to the first state. 
     Example 6 is the circuit of Example 1, wherein the output voltage is substantially constant between an end of the first period of time and an end of the second period of time. 
     Example 7 is the circuit of Example 1, wherein the second period of time is equal to or less than half the first period of time. 
     Example 8 is the circuit of Example 1, wherein the first and second periods of time have predetermined lengths. 
     Example 9 is the circuit of Example 1, further comprising one or more additional DCM phases coupled with the output node and in parallel with the first and second DCM phases, wherein the control circuit is to, in response to the detection, control the one or more additional DCM phases to be in the first state, concurrently with the first and second DCM phases, for respective time periods that are different than the first and second periods of time. 
     Example 10 is the circuit of Example 1, further comprising a circuit block coupled to the output node, wherein the circuit block is to use the output voltage as a power supply. 
     Example 11 is a voltage regulator comprising: multiple discontinuous conduction mode (DCM) phases coupled in parallel with one another to generate an output voltage at an output node, wherein individual DCM phases of the multiple DCM phases include: an inductor coupled between the output node and an intermediate node; a pull-up transistor coupled between the intermediate node and a supply rail that is to receive a supply voltage; and a pull-down transistor coupled between the intermediate node and a ground terminal. The voltage regulator of Example 11 further comprises a control circuit to: turn on the pull-up transistors of all of the multiple DCM phases when the output voltage drops below a threshold; upon expiration of a first predetermined time period, turn off the pull-up transistor and turn on the pull-down transistor of a first DCM phase of the multiple DCM phases; and upon expiration of a second predetermined time period that is different than the first predetermined time period, turn off the pull-up transistor and turn on the pull-down transistor of a second DCM phase of the multiple DCM phases. 
     Example 12 is the voltage regulator of Example 11, wherein the control circuit is further to: detect when a current through the inductor of the first DCM phase reaches zero after the pull-down transistor is turned on; and turn off the pull-down transistor responsive to the detection. 
     Example 13 is the voltage regulator of Example 11, wherein the output voltage is substantially constant between the expiration of the first predetermined time period and the expiration of the second predetermined time period. 
     Example 14 is the voltage regulator of Example 11, wherein the second predetermined time period is equal to or less than half the first predetermined time period. 
     Example 15 is the voltage regulator of Example 11, wherein the control circuit is to, upon expiration of one or more additional predetermined time periods that are different than the first and second predetermined time periods, turn off the pull-up transistor and turn on the pull-down transistor of one or more respective additional DCM phases of the multiple DCM phases. 
     Example 16 is the voltage regulator of Example 11, wherein the voltage regulator is on a same integrated circuit die as a load that is to use the output voltage as a power supply. 
     Example 17 is a computing system comprising: a motherboard; and an integrated circuit die mounted to the motherboard. The integrated circuit die comprises: a circuit block; a voltage regulator to provide a regulated output voltage to the circuit block at an output node, and a control circuit coupled with the voltage regulator. The voltage regulator includes: two or more discontinuous conduction mode (DCM) phases coupled with the output node and coupled in parallel with one another, wherein individual DCM phases of the two or more DCM phases are operable in a first state in which a current supplied to the output node via the respective DCM phase is to increase and a second state in which the current supplied to the output node via the respective DCM phase is to decrease. The control circuit is to: detect a trigger; switch all of the two or more DCM phases to the first state in response to the detection; upon expiration of a first predetermined time period, switch a first DCM phase of the two or more DCM phases from the first state to the second state; and upon expiration of a second predetermined time period that is shorter than the first predetermined time period, switch a second DCM phase of the two or more DCM phases from the first state to the second state. 
     Example 18 is the computing system of Example 17, wherein the individual DCM phases include: an inductor coupled between the output node and an internal node; a pull-up transistor coupled between the internal node and the supply rail; and a pull-down transistor coupled between the internal node and the ground terminal; wherein when the respective DCM phase is in the first state, the pull-up transistor is on and the pull-down transistor is off; and wherein when the respective DCM phase is in the second state, the pull-up transistor is off and the pull-down transistor is on. 
     Example 19 is the computing system of Example 18, wherein the individual DCM phases are further operable in a third state in which no current is to flow through the inductor of the respective DCM phase, wherein the control circuit is further to: switch the first DCM phase from the second state to the third state when a first current through the inductor of the first DCM phase reaches zero; and switch the second DCM phase from the second state to the third state when a second current through the inductor of the second DCM phase reaches zero. 
     Example 20 is the computing system of Example 17, wherein the output voltage is substantially constant between the expiration of the first predetermined time period and the expiration of the second predetermined time period. 
     Example 21 is the computing system of Example 17, wherein the second predetermined time period is equal to or less than half the first predetermined time period. 
     Example 22 is the computing system of Example 17, wherein the control circuit is to, upon expiration of one or more additional predetermined time periods that are different than the first and second predetermined time periods, switch one or more respective additional DCM phases of the two or more DCM phases from the first state to the second state. 
     Example 23 is the computing system of Example 17, wherein the trigger includes that the output voltage is below a threshold. 
     Example 24 is the computing system of Example 17, further comprising one or more of a memory circuit, a display, or an antenna coupled to the integrated circuit die. 
     Although certain embodiments have been illustrated and described herein for purposes of description, this application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments described herein be limited only by the claims. 
     Where the disclosure recites “a” or “a first” element or the equivalent thereof, such disclosure includes one or more such elements, neither requiring nor excluding two or more such elements. Further, ordinal indicators (e.g., first, second, or third) for identified elements are used to distinguish between the elements, and do not indicate or imply a required or limited number of such elements, nor do they indicate a particular position or order of such elements unless otherwise specifically stated.