Patent Publication Number: US-11038413-B2

Title: Power converter with overshoot compensation for a switching device

Description:
BACKGROUND 
     Technical Field 
     Embodiments described herein relate to integrated circuits, and more particularly, to techniques for generating regulated power supply voltages. 
     Description of the Related Art 
     Modern computer systems may include multiple circuits blocks designed to perform various functions. For example, such circuit blocks may include processors, processor cores configured to execute software or program instructions. Additionally, the circuit blocks may include memory circuits, mixed-signal or analog circuits, and the like. 
     In some computer systems, the circuit blocks may be designed to operate at different power supply voltage levels. Power management circuits may be included in such computer systems to generate and monitor varying power supply voltage levels for the different circuit blocks. 
     Power management circuits often include one or more power converter circuits configured to generated regulator voltage levels on respective power supply signals using a voltage level of an input power supply signal. Such regulator circuits may employ multiple passive circuit elements, such as inductors, capacitors, and the like. 
     SUMMARY OF THE EMBODIMENTS 
     Various embodiments of a power converter circuit are disclosed. Broadly speaking, a power converter circuit is contemplated, in which a switch node is coupled to a regulated power supply node via an inductor. The power converter circuit may be configured to source a charge current to the switch node, in response to an assertion of a control signal. A control circuit may be configured to, in response to an initiation of charge cycle, assert the control signal. The control circuit may be further configured to adjust, during an assertion of the control signal, a slope of a transition of the control signal using a voltage level of the switch node. In another non-limiting embodiments, the control circuit may be further configured to adjust the slope of the transition of the control signal using a plurality of control bits. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description makes reference to the accompanying drawings, which are now briefly described. 
         FIG. 1  illustrates a block diagram of an embodiment of a power converter circuit. 
         FIG. 2  illustrates schematic diagram of an embodiment of a regulator circuit. 
         FIG. 3  illustrates a block diagram of an embodiment of a control circuit for a power converter circuit. 
         FIG. 4  illustrates a block diagram of an embodiment of a driver circuit. 
         FIG. 5  illustrates a block diagram of an embodiment of a trigger circuit. 
         FIG. 6A  illustrates a block diagram of an embodiment of a pull-up driver circuit. 
         FIG. 6B  illustrates a block diagram of an embodiment of a pull-down driver circuit. 
         FIG. 7  illustrates example waveforms associated with the operation of a power converter circuit. 
         FIG. 8  illustrates a flow diagram depicting an embodiment of a method for operating a power converter circuit. 
         FIG. 9  depicts a block diagram of a computer system. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form illustrated, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to. 
     Various units, circuits, or other components may be described as “configured to” perform a task or tasks. In such contexts, “configured to” is a broad recitation of structure generally meaning “having circuitry that” performs the task or tasks during operation. As such, the unit/circuit/component can be configured to perform the task even when the unit/circuit/component is not currently on. In general, the circuitry that forms the structure corresponding to “configured to” may include hardware circuits. Similarly, various units/circuits/components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase “configured to.” Reciting a unit/circuit/component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112, paragraph (f) interpretation for that unit/circuit/component. More generally, the recitation of any element is expressly intended not to invoke 35 U.S.C. § 112, paragraph (f) interpretation for that element unless the language “means for” or “step for” is specifically recited. 
     As used herein, the term “based on” is used to describe one or more factors that affect a determination. This term does not foreclose the possibility that additional factors may affect the determination. That is, a determination may be solely based on specified factors or based on the specified factors as well as other, unspecified factors. Consider the phrase “determine A based on B.” This phrase specifies that B is a factor that is used to determine A or that affects the determination of A. This phrase does not foreclose that the determination of A may also be based on some other factor, such as C. This phrase is also intended to cover an embodiment in which A is determined based solely on B. The phrase “based on” is thus synonymous with the phrase “based at least in part on.” 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Computer systems may include multiple circuit blocks configured to perform specific functions. Such circuit blocks may be fabricated on a common substrate and may employ different power supply voltage levels. Power management units (commonly referred to as “PMUs”) may include multiple power converter circuits configured to generate regulated voltage levels for various power supply signals. Such power converter circuits may employ regulator circuit that includes both passive circuit elements (e.g., inductors, capacitors, etc.) as well as active circuit elements (e.g., transistors, diodes, etc.). 
     Different types of voltage regulator circuits may be employed based on power requirements of load circuits, available circuit area, and the like. One type of commonly used voltage regulator circuit is a buck converter circuit. Such buck converter circuits include multiple devices (also referred to as “switching device”) and a switch node that is coupled to a regulated power supply node via an inductor. Particular ones of the multiple devices are then activated to periodically charge and discharge the switch node in order to maintain a desired voltage level on power supply node. 
     Such switching devices may include power field-effect transistors (FETs) which are used to couple load circuits to input power supplies during the regulation process. In some cases, the load circuits may be located on a different integrated circuit and parasitic circuit elements, e.g., parasitic inductance, can result in voltage overshoots across terminals of the switching devices. Such voltage overshoots may result in the switching device exceeding their respective safe operating areas (SOAs), which can degrade the switching devices or cause the switching devices to fail. 
     To reduce voltage overshoots across the switching devices, some computer systems may slow down a speed with which a driver circuit drives a switching device. Such an approach, however, may increase power consumption (referred to as “switching losses”) during the extended transition by allowing multiple switching devices to be active at the same time. Other computer systems may employ clamp circuits to prevent voltage overshoot across the switching devices. Still other computer systems may employ analog control loops to regulate a slew rate of the switching devices activation. Such solutions may also increase power consumption of the power converter circuit. 
     The embodiments illustrated in the drawings and described below may provide techniques for operating a power converter circuit using a voltage level of the switch node to adjust the strength of a driver circuit coupled to a switching device during the switching process. By using the voltage level of the switch node to the strength of the driver circuit during the switching process, voltage overshot across the switching devices may be reduced without a large increase in power consumption. 
     A block diagram depicting an embodiment of a power converter circuit is illustrated in  FIG. 1 . As illustrated, power converter circuit  100  includes control circuit  101  and voltage regulator circuit  102 . 
     Voltage regulator circuit  102  includes switch node  105  coupled to regulated power supply node  110  via inductor  104 . In various embodiments, voltage regulator circuit  102  is configured, in response to an initiation of an assertion of control signal  106 , to source charge current  103  to switch node  105 . It is noted that although a single voltage regulator circuit is depicted in the embodiment of  FIG. 1 , in other embodiments, multiple voltage regulator circuits (collectively “phase units” or “phase circuits”) may be coupled to regulated power supply node  110 , in parallel, and operated with different timings (or “phases”). 
     As noted above, the transition of control signal  106  as it is asserted may be adjusted to reduce voltage overshoot across switching devices in voltage regulator circuit  102 . As illustrated in  FIG. 1 , control circuit  101  is configured, in response to an initiation of charge cycle  107 , assert control signal  106 . 
     Control circuit  101  is further configured to adjust, during an assertion of control signal  106 , a slope of a transition of control signal  106  using a voltage level of switch node  105 . As described below in more detail, control circuit  101  may be also be configured to adjust the slope of the transition of control signal  106  using a plurality of control bits. By adjusting the slope of the transition of control signal  106 , voltage overshoots across switching devices included in voltage regulator circuit  102  may be reduced, thereby by preventing failure or degradation of the switching devices. 
     In various embodiments, control circuit  101  senses when the voltage level of switch node  105  begins to increase, and after a programmable delay, control circuit  101  changes the slope of control signal  106 . The programmable delay may be determined by combining multiple currents. To sense the change in the voltage level of switch node  105 , control circuit  101  may be further configured to generate a first current using the voltage level of switch node  105 . As described below in more detail, control circuit  101  may be also configured to generate a second current using a plurality of devices that is a replica of the plurality of devices coupled to control signal  106  as well as replicas of devices included in voltage regulator circuit  102 . In some embodiments, control circuit  101  may adjust the slope of the transition of the control signal using a combination of the first current and the second current. 
     As used herein, a replica device (or “a replica of a device”) refers to a device that is a copy of a particular device, but that is not connected to the same load circuit as the particular device. In some cases, the physical design of the replica device may be the same as the physical design of the particular device by employing similar mask design used in conjunction with a semiconductor manufacturing process. 
     Voltage regulator circuits, such as voltage regulator circuit  102 , may be designed according to one of various design styles. A schematic diagram of a particular embodiment of voltage regulator circuit  102  is depicted in  FIG. 2 . As illustrated, voltage regulator circuit  102  includes devices  201  and  202 , which are both coupled to switch node  105 , and controlled by control signal  106 . 
     In various embodiments, control circuit  101  may generate control signal  106 , which used to activate one of devices  201  and  202  during charge and discharge cycles. During a charge cycle, current is sourced from input power supply node  203  to switch node  105 , and during a discharge cycle, current is sunk from switch node  105  into ground supply node  204 . Alternating between charge and discharge cycles, and adjusting the duration of either of the charge or discharge cycles may maintain a desired voltage level maintained on regulated power supply node  110 . 
     Device  201  is coupled between input power supply node  203  and switch node  105 , and is controlled by control signal  106 . During a charge cycle, control signal  106  is asserted, which activates device  201  and couples input power supply node  203  to switch node  105 , thereby charging switch node  105  by allowing a current to flow from input power supply node  203  to switch node  105 , and then onto regulated power supply node  110 . 
     As used herein, asserting, or an assertion of, a signal refers to setting the signal to a particular voltage level that activates a circuit or device coupled to the signal. The particular voltage level may be any suitable value. For example, in the case where device  201  is p-channel MOSFET, control signal  106  may be set to a voltage at or near ground potential when activated. 
     Device  202  is coupled between switch node  105  and ground supply node  204 , and is also controlled by control signal  106 . During a discharge cycle, control signal  106  is set to a voltage level, which activates device  202  and couples switch node  105  to ground supply node  204 , thereby providing a conduction path from regulated power supply node  110  through inductor  104  into ground supply node  204 . While device  202  is active, current flows from regulated power supply node  110  into ground supply node  204 , decreasing the voltage level of regulated power supply node  110 . 
     Device  201  and device  202  may be particular embodiments of MOSFETs. In particular, device  201  may be a particular embodiment of a p-channel MOSFET and device  202  may be a particular embodiment of an n-channel MOSFET. Although only two devices are depicted in the embodiment of  FIG. 2 , in other embodiments, any suitable number of devices, coupled in series or parallel, may be employed to achieve particular electrical characteristics (e.g., on-resistance of the devices). 
     A block diagram of an embodiment of control circuit  101  is depicted in  FIG. 3 . As illustrated, control circuit  101  includes trigger circuit  301 , driver circuit  302 , and register circuit  307 . 
     Trigger circuit  301  is configured to generate slope control signal  304  using cycle signal  303  and a voltage level of switch node  105 . As described below in more detail, trigger circuit  301  may generate and combine multiple currents to determine at which point to trigger (or activate) slope control signal  304 . In various embodiments, cycle signal  303  may be a clock or other timing signal, and may be generated by a control loop circuit (not shown) that govern the duration of a charge or discharge cycle of power converter circuit  100 . 
     Driver circuit  302  is configured to generate control signal  106  using slope control signal  304  and cycle signal  303 . In various embodiments, driver circuit  302  may be configured to assert control signal  106  using cycle signal  303 . Driver circuit  302  may be further configured to, during an assertion of control signal  106 , to modify a slope of control signal  106  using slope control signal  304  and control bits  305  and  306 . In some cases, to modify the slope of the control signal  106 , driver circuit  302  may be further configured to increase a transition time of the assertion of control signal  106 . In various embodiments, the increase in transition time may be a result of a decrease in a slope of the transition of control signal  106 . As used herein, a transition time of a signal refers to a time for the signal to change from one logic state to another logic state. For example, in the illustrated embodiment, driver circuit  302  may be configured to increase an amount of time for control signal  106  to transition for a logical-1 value to a logical-0 value. A magnitude of the change in the transition time (or slope) of control signal  106  may be based, at least in part, on control bits  305  and  306 . 
     Register circuit  307  is configured to store control bits  305  and control bits  306 . As described below in more detail, control bits  306  may be used to adjust the strength of a pull-up driver circuit, and control bits  305  may be used to adjust the strength of a pull-down circuit. In various embodiments, register circuit  307  may include multiple storage circuits, e.g., latch circuit or flip-flop circuits, each configured to store a single bit of control bits  305  and  306 . It is noted that any suitable number of storage circuits may be employed. 
     Structures such as those shown in  FIGS. 2 and 3  for generating a voltage level on a regulated power supply node may be referred to using functional language. In some embodiments, these structures may be described as including “a means for sourcing a charge current to the switch node in response to an assertion of a control signal,” “a means for, in response to an initiation of a charge cycle, asserting the control signal,” and “a means for adjusting, during an assertion of the control signal, a slope of a transition of the control signal using a voltage level of the switch node.” 
     The corresponding structure for “means for sourcing a charge current to the switch node during a charge cycle” is voltage regulator circuit  102  as well as equivalents of this circuit. The corresponding structure of “a means for sourcing a charge current to the switch node in response to an assertion of a control signal” is driver circuit  302  and its equivalents. The corresponding structure for “a means for adjusting, during an assertion of the control signal, a slope of a transition of the control signal using a voltage level of the switch node” is trigger circuit  301  and driver circuit  302  and their equivalents. 
     A block diagram of an embodiment of driver circuit  302  is depicted in  FIG. 4 . As illustrated, driver circuit  302  includes pull-up driver circuit  411 , pull-down driver circuit  412 , inverters  405 ,  407 ,  408 , and  418 , NOR gate  404 , and NAND gate  406 . Pull-up driver circuit  411  includes OR gate  403  and device  401 . Pull-down driver circuit  412  includes NOR gates  410  and  409 , variable resistor  419 , and device  402 . 
     As described below in more detail, device  401  and OR gate  403 , which are included in pull-up driver circuit  411 , may include multiple devices and gates, respectively, connected in parallel. In such cases, different ones of control bits  306  may be coupled to respective ones of the multiple OR gates that are included in OR gate  403 . 
     In a similar fashion, and as described below in more detail, device  402 , NOR gate  409 , and NOR gate  410  may include multiple devices and gates, respectively, coupled in parallel. Each of control bits  305  may be coupled to a respective one of the multiple NOR gates included in NOR gate  410 . Additionally, each output of the multiple NOR gates included in NOR gate  410  may be coupled to an input of a respective on of the multiple NOR gates included in NOR gate  409 . Lastly, each output of the multiple NOR gates included in NOR gate  409  may be coupled to a control terminal of a respective one of the multiple devices included in device  402 . Device  402  is coupled to a ground supply node and is also coupled to control signal  106  via variable resistor  419 . Variable resistor  419  may be a metal resistor, polysilicon resistors, or any other suitable type of resistor available on a semiconductor manufacturing process. In various embodiments, the value of variable resistor  419  is selected post-manufacture to fine tune the performance of pull-down driver circuit  412 . 
     Cycle signal  303  is coupled to inputs of NOR gate  404  and NAND gate  406 . The output of NOR gate  404  is coupled to the input of inverter  405 , whose output is coupled to node  413 , which is also coupled to the input of NAND gate  406 . The output of NAND gate  406  is coupled to the input of inverter  407 , whose output is coupled to NODE  416 , which is also coupled to an input of NOR gate  404  and the input of inverter  408 . The output of inverter  408  is coupled to node  414 . It is noted that the combination of NOR gate  404 , inverter  405 , NAND gate  406  and inverter  407  may, in various embodiments, function as a set-reset (SR) latch. 
     Slope control signal  304  is coupled to the input of inverter  418 , whose output is coupled to node  417 . In response to a transition of slope control signal  304  to a high logic value, inverter  418  generates a low logic value on node  417 . As described below in more detail, a low logic value on node  417  enables NOR gate  410 , allowing control bits  305  to selectively activate particular lines of bus  415 , thereby adjusting a number of devices  402  that are active. 
     As used and described herein, a logical-0, logic 0 value or low logic level, describes a voltage sufficient to activate a p-channel metal-oxide semiconductor field effect transistor (MOSFET), and a logical-1, logic 1 value, or high logic level describes a voltage level sufficient to activate an n-channel MOSFET. It is noted that, in various other embodiments, any suitable voltage levels for logical-0 and logical-1 may be employed. 
     During a discharge cycle, cycle signal  303  is at a high logic level, which results in node  413  being at a low logic level. Values of the respective outputs of the multiple OR gates included in OR gate  403  may be based, at least in part, on the values of corresponding ones of control bits  306 . By adjusting the values of control bits  306 , different numbers of the multiple devices included in device  401  may be activated in order to change an amount of current that device  401  is capable of sourcing to node through which cycle signal  206  propagates. 
     When the discharge cycle ends, and a charge cycle commences, cycle signal  303  transitions to a low logic level. This results in node  413  transitioning to a high logic level, disabling device  401 . Additionally, node  416  transitions to a high logic level, which results in a low logic level on each input of the multiple NOR gates included in NOR gate  409 . 
     At the beginning of the charge cycle, slope control signal  304  is at a low logic level, which prevents control bits  305  from propagating past NOR gate  410 , thereby allowing all lines of bus  415  to transition to a high logic level. The high logic levels on the lines of bus  415  activates each device included in the multiple devices of device  402 . As described below in more detail, as the voltage level of switch node  105  increases to a threshold value, slope control signal  304  transitions to a high logic level, which allows controls bits  305  to propagate, via respective ones of the NOR gates included in NOR gate  410 , to NOR gate  409 , which may de-assert particular lines of bus  415 . The de-asserted lines of bus  415 , in turn, deactivate corresponding ones of the multiple devices included in device  402 , thereby reducing the amount of current that device  402  can discharge from the node through which control signal  106  propagates. By reducing the amount of current being discharged, the slope of signal increases, and the time for control signal  106  to transition from a high logic level to a low logic level decreases. 
     Turning to  FIG. 5 , a block diagram of an embodiment of trigger circuit  301  is depicted. As illustrated, trigger circuit  301  includes devices  501 ,  503 ,  504 , and  506 , detection circuit  502 , variable resistor  508 , and inverter  507 . 
     Device  501  is coupled between switch node  105  and node  511  and controlled by bias signal  512 . In various embodiments, device  501  may be a particular embodiment of a high-voltage device, i.e., device  501  may be manufactured such that it may have larger voltages across its terminals without damaging the device. In some cases, device  501  may be similar to device  202  of voltage regulator circuit  102 . A value of current  509  may be determined based, at least in part on, a value of bias signal  512  and the respective voltage levels of switch node  105  and node  511 . In various embodiments, the value of current  509  may be adjusted using bias signal  512  to adjust an amount of time from when the voltage level of switch node  105  begins to change to when slope control signal  304  is activated. 
     Device  503  is coupled between node  511  and ground supply node  204 . A control terminal of device  503  is coupled to replica control signal  513 , which is coupled to device  504  and variable resistor  508 . Device  503  sinks current  510  from node  511  based, at least in part, on a voltage level on its control terminal. In various embodiments, device  503  may be a replica of device  202  as depicted in voltage regulator circuit  102 . 
     In various embodiments, detection circuit  502  may be a particular embodiment of a Schmitt trigger or other suitable circuit configured to assert slope control signal  304  in response to a voltage level on node  511  reaching a threshold value. In various embodiments, detection circuit  502  may be configured to employ positive feedback by combining slope control signal  304  with the voltage level on node  511 , and using the composite signal to generate the value of slope control signal  304 . It is noted that in some embodiments, the threshold value at which detection circuit  502  asserts slope control signal  304  may be programmable based, at least in part, on values of parasitic circuit elements coupled to power converter circuit  100 , power consumption of power converter circuit  100 , and the like. 
     Device  504  is coupled between input power supply signal and variable resistor  508 . Device  506  is coupled between variable resistor  508  and ground supply node  204 . Control terminals of both device  504  and  506  are coupled to the output of inverter  507 . In various embodiments, device  504  may be a particular embodiment of a p-channel MOSFET and device  506  may be a particular embodiment of an n-channel MOSFET. In some cases, device  506  may be a replica of device  402  as illustrated in  FIG. 4 . Variable resistor  508  may be a metal resistor, polysilicon resistors, or any other suitable type of resistor available on a semiconductor manufacturing process. In various embodiments, the value of variable resistor  508  is selected post-manufacture to fine tune the performance of trigger circuit  301 . 
     Inverter  507  may be a particular embodiment of a CMOS inverting amplifier and is configured to invert the logical sense of cycle signal  303 . In response to cycle signal  303  transitioning to a low logic level, the output of inverter  507  transitions to a high logic level, deactivating device  504  and activating device  506 . As device  506  is activated, a voltage level of the control terminal of device  503  is discharged to ground, deactivating device  503 . 
     During a discharge cycle, the voltage level of switch node  105  is decreasing, which, in turn, contributes to the voltage level of node  511  decreasing. Also, during a discharge cycle, cycle signal  303  is high, which results in a low value on the output of inverter  507 . The low value on the output of inverter  507  deactivates device  506  and activates device  504 , thereby pulling the control terminal of device  503  to a voltage level at or near that of input power supply node  203 . Such a voltage level on the control terminal of device  503  activates device  503 , which, in turn, sinks current  510  from node  511 . 
     When the discharge cycle ends and a charge cycle beings, cycle signal  303  transitions to a low, thereby deactivating device  504  and activating device  506 . The activation of device  506  discharges the control terminal of device  503 , turning the device off. With device  503  no longer sinking current, the voltage level of node  511  increases in response to an increase in the voltage level of switch node  105 . 
     Turning to  FIG. 6A , a block diagram of an embodiment of pull-up driver circuit  411  is depicted. As illustrated, pull-up driver circuit  411  includes device  601 - 603 , and OR gates  604 - 606 . 
     Device  601 - 603  correspond to device  401  as illustrated in  FIG. 1 . Each of devices  601 - 603  are coupled between control signal  106  and a power supply signal, e.g., input power supply node  203 . The control terminals of devices  601 - 603  are coupled to the outputs of OR gates  604 - 606 , respectively. In various embodiments, each of devices  601 - 603  may be particular embodiments of p-channel MOSFETs or other suitable transconductance devices. 
     OR gates  604 - 606  correspond to OR gate  403  as illustrated in  FIG. 4 . Inputs of each of OR gates  604 - 606  are coupled to node  413  as well as respective ones of control bits  306 . For example, one input of OR gate  604  is coupled to node  413 , and the other input is coupled to bit &lt; 2 &gt; of control bits  306 . OR gates  604 - 606  may be particular embodiments of a logic gate configured to generate an output that is the Boolean OR of its input logic levels. In various embodiments, OR gates  604 - 606  may be implemented using NOR gates and inverters, or any other suitable combination of logic gates. 
     In response to node  413  being set to a low logic level, individual ones of devices  601 - 603  may be activated based, at least in part, on the state of a corresponding one of control bits  306 . For example, when both node  413  and bit &lt; 2 &gt; of control bits  306  are at low logic levels, OR gate  604  generates a low logic level on its output, thereby activating device  601 , which, in turn, sources current to control signal  106 , increasing its voltage level. By selecting which of control bits  306  are set to low logic levels, the amount of current sourced to control signal  106  may be adjusted in order to fine tune the operation of driver circuit  302 . 
     A block diagram of an embodiment of pull-down driver circuit  412  is depicted in  FIG. 6B . As illustrated, pull-down driver circuit  412  includes devices  607 - 609 , variable resistor  616 , and NOR gates  610 - 615 . In various embodiments, devices  607 - 609  correspond to device  402  of  FIG. 4 , NOR gates  610 - 612  correspond to NOR gate  409  of  FIG. 4 , and NOR gates  613 - 615  correspond to NOR gate  410  of  FIG. 4 . 
     Each of devices  607 - 609  is coupled to control signal  106  via variable resistor  419  and a ground supply signal, e.g., ground supply node  204 . The control terminals of devices  607 - 609  are coupled to respective outputs of NOR gates  610 - 612 , respectively. Each of devices  607 - 609  may be particular embodiments of n-channel MOSFETs or other suitable transconductance devices. As described above, different ones of devices  607 - 609  may be selectively deactivated during a charge cycle to change the transition time of control signal  106 . 
     NOR gates  613 - 615  correspond to NOTE gate  410  as illustrated in  FIG. 4 . Inputs of each of NOR gates  613 - 615  are coupled node  417  as well as respective ones of control bits  305 . For example, one input of NOR gate  613  is coupled to node  417 , and the other input of NOR gate  613  is coupled to bit &lt; 0 &gt; of control bits  305 . Each of the outputs of NOR gates  613 - 615  is connected to an input of a corresponding on of NOR gates  610 - 612 . 
     NOR gates  610 - 612  correspond to NOR gate  409  as illustrated in  FIG. 4 . Inputs of each of NOR gates  610 - 612  are coupled to node  414  as well as outputs of respective ones of NOR gates  613 - 615 . For example, one input of NOR gate  610  is coupled to node  414 , and the other input is coupled to the output of NOR gate  613 . 
     NOR gates  610 - 615  may be particular embodiments of a logic circuit configured to generate an output that is the Boolean NOT-OR of the logic values at its inputs. In various embodiments, NOR gates  610 - 615  may be designed using any suitable combination of p-channel and n-channel MOSFETs, or other suitable transconductance devices. 
     Waveforms illustrating the operation of power converter circuit  100  are depicted in  FIG. 7 . It is noted that the waveforms of  FIG. 7  are merely examples, and that in other embodiments, the waveforms may appear different and the relative timings between waveforms may be different. 
     At time t 1 , cycle signal  303  transitions to a low logic level. In various embodiments, the change in logic value of cycle signal  303  may be a result of a determination that a discharge cycle of power converter circuit  100  has ended and a charge cycle has begun. The end of the discharge cycle may be determined using a clock signal or other timing signal, or as a result of a detection of an endpoint condition, e.g., a voltage level of switch node  105  reaching a particular voltage threshold. 
     In response to cycle signal  303  transitioning to a low logic level, node  416  transitions to a high logic level, which, in turn, transitions the lines of bus  415  to a high logic level. The high logic levels of the lines of bus  415  activates device  402 , which includes devices  607609 , discharging control signal  106 , thereby activating device  201  in voltage regulator circuit  102 . 
     At time t 2 , slope control signal  304  is asserted. As described above, the assertion of slope control signal  304  may be a result of trigger circuit  301  detecting that the voltage level of switch node  105  is beginning to increase. In response to the assertion of slope control signal  304 , one or more lines of bus  415  in pull-down driver circuit  412  may transition to a low logic level based upon corresponding ones of control bits  305  (as indicated by updated value of at least one line of bus  415  in  FIG. 7 ). As the one or more lines of bus  415  transition to a low logic level, corresponding ones of devices  607609  may deactivate, thereby decreasing a rate of increase, i.e., decreasing the slope, of control signal  106 . 
     At time t 3 , cycle signal  303  transitions back to a high logic level. In response to cycle signal  303  transitioning to a high logic level, node  416  transitions to a low logic level, which, in turn, transitions the lines of bus  415  to low logic levels, thereby deactivating device  402 . In various embodiments, the transition of cycle signal  303  may be a result of a detection of an end of a charge cycle of power converter circuit  100 . In various embodiments, the end of the charge cycle may be based on a clock signal or other timing signal, or on a detection of a particular condition, such as the voltage level of the switch node reaching a different threshold value. 
     Turning to  FIG. 8 , a flow diagram depicting an embodiment of a method for operating a power converter circuit is illustrated. The method, which may be applied to power converter circuit  100  as depicted in  FIG. 1 , begins in block  801 . 
     The method includes initiating a charge cycle of a voltage regulator circuit that includes a switch node coupled to a regulated power supply node via an inductor (block  802 ). 
     The method further includes, in response to initiating the charge cycle, activating a control signal (block  803 ). As noted above, initiating the charge cycle may be in response to the assertion of a clock signal or other timing reference signal. 
     In response to initiating the charge cycle, the method also includes sourcing a charge current to the switch node using the control signal (block  804 ). In various embodiments, sourcing the charge current to the switch node may include activating one or more of a first plurality of devices coupled to the control signal. 
     The method further includes, in response to initiating the charge cycle, while activating the control signal, modifying a transition time of the control signal using a voltage level of the switch node (block  805 ). In some embodiments, in modifying the transition time of the control signal, the method may also include decreasing a slope of the control signal. 
     The method may also include, in some embodiments, modifying the transition time using the voltage level of the switch node and a plurality of control bits. In various embodiments, the method may also include deactivating one or more devices of the first plurality of devices coupled to the control signal using respective ones of the plurality of control bits. 
     The method may, in some embodiments, include generating a first current using the voltage level of the switch node. In some cases, the method may further include generating a second current using a second plurality of devices that is a replica of the first plurality of devices. In various embodiments, the method also includes generating a slope control signal using a combination of the first current and the second current, and modifying the transition time of the control signal using the slope control signal. The method concludes in block  806 . 
     A block diagram of computer system is illustrated in  FIG. 9 . In the illustrated embodiment, the computer system  900  includes power management circuit  901 , processor circuit  902 , memory circuit  903 , and input/output circuits  904 , each of which is coupled to power supply signal  905 . In various embodiments, computer system  900  may be a system-on-a-chip (SoC) and/or be configured for use in a desktop computer, server, or in a mobile computing application such as, e.g., a tablet, laptop computer, or wearable computing device. 
     Power management circuit  901  includes power converter circuit  100 , which is configured to generate a regulated voltage level on power supply signal  905  in order to provide power to processor circuit  902 , memory circuit  903 , and input/output circuits  904 . Although power management circuit  901  is depicted as including a single power converter circuit, in other embodiments, any suitable number of power converter circuits may be included in power management circuit  901 , each configured to generate a regulated voltage level on a respective one of multiple internal power supply signals included in computer system  900 . In cases where multiple power converter circuits are employed, two or more of the multiple power converter circuits may be connected to a common set of power terminals that connections to power supply signals and ground supply signals of computer system  900 . 
     Processor circuit  902  may, in various embodiments, be representative of a general-purpose processor that performs computational operations. For example, processor circuit  902  may be a central processing unit (CPU) such as a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). 
     Memory circuit  903  may in various embodiments, include any suitable type of memory such as a Dynamic Random-Access Memory (DRAM), a Static Random-Access Memory (SRAM), a Read-Only Memory (ROM), Electrically Erasable Programmable Read-only Memory (EEPROM), or a non-volatile memory, for example. It is noted that although in a single memory circuit is illustrated in  FIG. 9 , in other embodiments, any suitable number of memory circuits may be employed. 
     Input/output circuits  904  may be configured to coordinate data transfer between computer system  900  and one or more peripheral devices. Such peripheral devices may include, without limitation, storage devices (e.g., magnetic or optical media-based storage devices including hard drives, tape drives, CD drives, DVD drives, etc.), audio processing subsystems, or any other suitable type of peripheral devices. In some embodiments, input/output circuits  904  may be configured to implement a version of Universal Serial Bus (USB) protocol or IEEE 1394 (Firewire®) protocol. 
     Input/output circuits  904  may also be configured to coordinate data transfer between computer system  900  and one or more devices (e.g., other computing systems or integrated circuits) coupled to computer system  900  via a network. In one embodiment, input/output circuits  904  may be configured to perform the data processing necessary to implement an Ethernet (IEEE 802.3) networking standard such as Gigabit Ethernet or 10-Gigabit Ethernet, for example, although it is contemplated that any suitable networking standard may be implemented. In some embodiments, input/output circuits  904  may be configured to implement multiple discrete network interface ports. 
     Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where only a single embodiment is described with respect to a particular feature. Examples of features provided in the disclosure are intended to be illustrative rather than restrictive unless stated otherwise. The above description is intended to cover such alternatives, modifications, and equivalents as would be apparent to a person skilled in the art having the benefit of this disclosure. 
     The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims.