Voltage regulator circuit

Abstract

The utility model relates to a voltage regulator bypass mode control circuit. A voltage regulator circuit includes: an input configured to receive an input voltage; an output configured to generate a regulated output voltage; a pass element coupled between the input terminal and the output terminal; a bypass element coupled in parallel with the pass element; a feedback voltage divider coupled between the output terminal and a ground node; an error amplifier coupled between the control node of the pass element and the feedback voltage divider; and a voltage drop transition control circuit, coupled to the feedback voltage divider, configured to activate a voltage drop mode of the voltage regulator circuit to limit the inrush current by controlling a voltage drop transition at the output from the regulated output voltage to a voltage drop voltage level. The feedback voltage divider is configured to generate a feedback signal indicative of the output voltage. The error amplifier is configured to minimize a difference between the reference and the feedback signal.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to analog power electronic circuits, and in particular embodiments, to the structure of a voltage regulator circuit including a bypass mode and methods of operating the same. BACKGROUND

[0002] Linear voltage regulators, such as low-dropout regulators, or LDOs, can operate in two different modes: a normal regulation mode, during which the LDO ideally maintains a constant output voltage; and a so-called dropout mode, in which the output voltage is lower than the nominal regulated level. In dropout mode, the pass element (e.g., a power transistor) operates in the linear region (i.e., fully on), and the output voltage approaches the input voltage.

[0003] In some particular applications, it can be desirable to activate the dropout mode "manually" by the user, even in the normal regulation mode. When this happens, the output voltage rises from the regulated level and approaches the input voltage, so as to reach a minimum voltage difference between the input voltage and the output voltage.

[0004] To reduce the minimum voltage difference between the input voltage (VIN) of the voltage regulator and the output voltage (VOUT) of the voltage regulator when the dropout mode is activated, a bypass element can be connected in parallel with the pass element. When the bypass element is on (so-called bypass mode), the additional current path causes the voltage difference to be reduced.

[0005] Switching to bypass mode also introduces an undesirable inrush current. Also, when the dropout mode is activated, there is no overcurrent protection (OCP) available. Therefore, it is desirable to have a linear voltage regulator that reduces these undesirable features in case the dropout mode is activated manually. SUMMARY

[0006] According to an embodiment of the present invention, a voltage regulator circuit includes an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element coupled between the input node and the output node; a bypass element coupled in parallel with the pass element; a feedback voltage divider coupled between the output node and a ground node; an error amplifier circuit coupled between a control node of the pass element and the feedback voltage divider; and a dropout transition control circuit coupled to the feedback voltage divider. The feedback voltage divider is configured to produce a feedback signal indicative of the regulated output voltage. The error amplifier circuit is configured to minimize a voltage difference between a reference voltage and the feedback signal. The dropout transition control circuit is configured to activate a dropout mode of the voltage regulator circuit by controlling a dropout transition at the output node from the regulated output voltage to a dropout voltage level to limit an inrush current.

[0007] In one embodiment, the voltage regulator circuit further comprises a bypass transition control circuit including a bypass switch coupled between the control node of the pass element and the control node of the bypass element, the bypass switch configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition from the voltage droop level to a bypass voltage level at the output node to further limit the inrush current.

[0008] In one embodiment, the voltage regulator circuit further comprises a bypass transition control circuit including a bypass switch coupled between the control node of the pass element and the control node of the bypass element, the bypass switch configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition from the voltage droop level to a bypass voltage level at the output node to further limit the inrush current.

[0009] In one embodiment, the bypass switch is further configured to activate the bypass mode by making the bypass transition a substantially exponential voltage curve near the bypass voltage level to further limit the inrush current.

[0010] In one embodiment, wherein the bypass transition control circuit further comprises a resistor coupled between the control node of the pass element and the control node of the bypass element, and wherein the substantially exponential voltage curve is controlled according to an RC constant determined by the capacitor between the control node and the input node and the resistor.

[0011] In one embodiment, the bypass transition control circuit is configured to trigger the bypass switch in response to detecting that the voltage regulator circuit is in the voltage droop mode.

[0012] In one embodiment, the voltage regulator circuit further comprises an overcurrent protection control circuit including an overcurrent protection switch coupled between the control node of the pass element and the control node of the bypass element, the overcurrent protection switch configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0013] According to another embodiment of the present invention, a method of activating a bypass mode of a voltage regulator includes generating a regulated output voltage at an output node of the voltage regulator; activating a voltage droop mode of the voltage regulator circuit by controlling a voltage droop transition from the regulated output voltage to a voltage droop level using a voltage droop transition control circuit coupled to a feedback voltage divider, wherein the feedback voltage divider is coupled between the output node and a ground node; and activating a bypass mode of the voltage regulator by turning on a bypass element coupled in parallel with a pass element coupled between the output node and an input node of the voltage regulator.

[0014] In at least one embodiment of the method, activating the voltage droop mode includes making the voltage droop transition a substantially linear voltage curve to limit the inrush current.

[0015] In at least one embodiment of the method, activating the bypass mode includes connecting the control node of the pass element and the control node of the bypass element while using the bypass transition control circuit coupled between the control nodes to control a bypass transition from the pressure drop voltage level to the bypass voltage level to limit the inrush current.

[0016] In at least one embodiment of the method, the method further includes deactivating the bypass mode by disconnecting the control node of the pass element and the control node of the bypass element while using the bypass transition control circuit to control a bypass transition from the bypass voltage level to the pressure drop voltage level to further limit the inrush current and activating a regulation mode of the voltage regulator by using the pressure drop transition control circuit to control a pressure drop transition from the pressure drop voltage level to the regulated output voltage to further limit the inrush current.

[0017] In at least one embodiment of the method, the method further includes providing a low resistance connection between the control node of the pass element and the control node of the bypass element during the overcurrent event or immediately after a delay triggered by the activation of the bypass mode.

[0018] In at least one embodiment of the method, the method further includes providing a bypass mode activation signal prior to activating the pressure drop mode, the bypass mode activation signal initiating the activation of the pressure drop mode, and initiating the activation of the bypass mode in response to the bypass mode activation signal and detecting that the voltage regulator is in the pressure drop mode.

[0019] In at least one embodiment of the method, the method further includes providing a low resistance connection between the control node of the pass element and the control node of the bypass element during the overcurrent event or immediately after a delay triggered by the activation of the bypass mode.

[0020] According to yet another embodiment of the present application, a voltage regulator circuit includes: an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element and a bypass element coupled in parallel between the input node and the output node; an overcurrent protection pass element and an overcurrent protection bypass element coupled in parallel to the input node; a bypass transition control circuit including a soft gate tie switch; and an overcurrent protection control circuit including a delayed hard gate tie switch. A control node of the overcurrent protection pass element is coupled to a control node of the pass element. A control node of the overcurrent protection bypass element is coupled to a control node of the bypass element. The soft gate tie switch of the bypass transition control circuit is coupled between the control node of the pass element and the control node of the bypass element. The soft gate tie switch is configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition at the output node to limit an inrush current while turning on the bypass element. The delayed hard gate tie switch of the overcurrent protection control circuit is coupled between the control node of the pass element and the control node of the bypass element. The delayed hard gate tie switch is configured to provide a low resistance connection between the control nodes immediately after a delay during an overcurrent event or triggered by the activation of the bypass mode.

[0021] In one embodiment, the voltage regulator circuit further includes: a feedback voltage divider coupled between the output node and a ground node, the feedback voltage divider configured to produce a feedback signal indicative of the regulated output voltage; an error amplifier circuit coupled between the control node of the pass element and the feedback voltage divider, the error amplifier circuit configured to compare a reference voltage to the feedback signal; and a droop transition control circuit coupled to the feedback voltage divider and configured to activate a droop mode of the voltage regulator circuit by controlling a droop transition at the output node from the regulated output voltage to a droop voltage level to further limit the inrush current.

[0022] In one embodiment, the droop transition control circuit is further configured to activate the droop mode by making the droop transition a substantially linear voltage curve to further limit the inrush current.

[0023] In one embodiment, the soft gate tie switch is further configured to activate the bypass mode by making the bypass transition a substantially exponential voltage curve near the bypass voltage level to further limit the inrush current.

[0024] In one embodiment, the bypass transition is from the droop voltage level to the bypass voltage level.

[0025] In one embodiment, the bypass transition control circuit is configured to trigger the soft gate tie switch in response to detecting that the voltage regulator circuit is in the droop mode. BRIEF DESCRIPTION OF DRAWINGS

[0026] For a more complete understanding of the present application, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings in which:

[0027] Figure 1 illustrates an example voltage regulator circuit having a pass element coupled in parallel with a bypass element and including a control node coupled to the pass element and a comparison circuit (such as an error amplifier circuit) configured to compare a reference voltage to a feedback signal;

[0028] Figure 2 illustrates an example qualitative plot showing the output voltage of a voltage regulator during a controlled transition to a dropout mode and a bypass mode in accordance with an embodiment of the present application;

[0029] Figure 3A illustrates an example voltage regulator circuit including a dropout transition control circuit coupled to a feedback divider in accordance with an embodiment of the present application, and Figure 3B illustrates a corresponding qualitative plot showing the output voltage of a voltage regulator circuit during a controlled dropout transition in accordance with an embodiment of the present application;

[0030] Figure 4 illustrates an example dropout transition control circuit including a ramp generator circuit coupled to a ramp control element in accordance with an embodiment of the present application;

[0031] Figure 5 illustrates another example dropout transition control circuit including a ramp generator circuit coupled to a ramp control element including a current source in accordance with an embodiment of the present application;

[0032] Figure 6A illustrates an example voltage regulator circuit including a bypass transition control circuit including a bypass switch configured to provide a "soft" connection to activate a bypass mode of the voltage regulator circuit in accordance with an embodiment of the present application, and Figure 6B illustrates a corresponding qualitative plot showing the output voltage of a voltage regulator circuit during a controlled bypass transition in accordance with an embodiment of the present application;

[0033] Figure 7 illustrates an example voltage regulator circuit including a bypass transition control circuit and an overcurrent protection control circuit including an overcurrent protection switch configured to provide a "hard" connection during an overcurrent event in accordance with an embodiment of the present application;

[0034] Figure 8 illustrates another example voltage regulator circuit including a dropout transition control circuit, a bypass transition control circuit, and an overcurrent protection control circuit in accordance with an embodiment of the present application;

[0035] Figure 9 FIG. 1 illustrates an example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a regulation mode to a bypass mode, according to an embodiment of the application;

[0036] Figure 10 FIG. 1 illustrates an example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a regulation mode to a bypass mode, according to an embodiment of the application;

[0037] Figure 11 FIG. 1 illustrates an example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a regulation mode to a bypass mode, according to an embodiment of the application;

[0038] Figure 12 FIG. 1 illustrates an example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a regulation mode to a bypass mode, according to an embodiment of the application;

[0039] Unless otherwise indicated, corresponding reference numbers and designations in different figures generally refer to corresponding parts. The figures are drawn to clearly illustrate relevant aspects of the embodiments, and are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate termination of a feature's extent. DETAILED DESCRIPTION

[0040] The making and using of various embodiments are discussed in detail below. It should be appreciated, however, that the various embodiments described herein are applicable in a variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments, and should not be interpreted as limiting the scope. Unless otherwise specified, the expressions "about," "approximately," and "substantially" mean within 10% of a given value, and preferably within 5%, or less than 10% of a comparable amount and preferably less than 5%, such as in the case of substantially zero.

[0041] When activating or deactivating the bypass mode of a voltage regulator (e.g., a linear voltage regulator, such as an LDO), the entire sequence is important under control. Conventional methods of switching to and from the bypass mode employ a "hard" switching solution. That is, connections are made in a binary fashion, such that voltage levels change rapidly without regard to the details of the transition. This results in potentially dangerous inrush currents that can cause harm to the voltage regulator (and surrounding circuitry, such as a power management integrated circuit (IC), etc.) as well as to the system being powered by the voltage regulator. Thus, a solution that controls the transition between normal regulation mode and bypass mode such that inrush currents are reduced and / or minimized can be desirable.

[0042] Furthermore, conventional solutions do not provide any OCP functionality. It can be desirable to have OCP functionality to ensure that the component is still protected from overcurrent events when the bypass mode is activated and deactivated and while in bypass mode. However, if the solution is too complex, it can make the OCP functionality in bypass mode impractical, thereby disabling the functionality altogether. Thus, it can be desirable to have a simple solution that controls the use of OCP functionality already available with the voltage regulator itself.

[0043] There are options to reduce the minimum voltage difference between VIN and VOUT when the dropout mode is enabled. The voltage difference can be reduced simply by increasing the size of the pass element and the bypass element, but this has many drawbacks such as large changes in regulation parameters, reduced stability, and a worsened transient response of the voltage regulator. The bypass element can also be connected in parallel at the appropriate time, but this cannot be done in normal regulation mode (e.g., because of the high open loop gain that would cause possible oscillation).

[0044] In various embodiments, the present invention provides a method of implementing a bypass mode in a voltage regulator that can even be activated during normal operation (regulation mode) of the voltage regulator, while reducing, minimizing, or eliminating undesirable effects associated with conventional solutions such as high inrush current and lack of protection from overcurrent events (OCP functionality).

[0045] In various embodiments, a voltage regulator circuit includes a voltage input node and a regulated voltage output node. A pass element is coupled between the input node and the output node. A bypass element is coupled in parallel with the pass element. The voltage regulator circuit also includes a feedback voltage divider coupled between the output node and a ground node. A comparison circuit is coupled to a control node of the pass element. The comparison circuit is configured to compare a reference voltage to a feedback signal generated by the feedback circuit. An error amplifier controls the pass element so as to maintain a minimum voltage difference between the reference voltage and the feedback signal indicative of the voltage at the regulated output node.

[0046] A dropout transition control circuit can be included in the voltage regulator circuit that is coupled with the feedback voltage divider. The dropout transition control circuit is configured to activate a dropout mode of the voltage regulator circuit by controlling a dropout transition voltage at the output node of the voltage regulator circuit (i.e., a "soft" transition as opposed to an uncontrolled "hard" transition). For example, the transition of the controlled dropout transition voltage between the regulated voltage and the dropout voltage level can be more gradual than an uncontrolled transition. The controlled dropout transition voltage can thereby advantageously limit the inrush current during the transition to the dropout mode.

[0047] A bypass transition control circuit can also be included in the voltage regulator circuit. The bypass transition control circuit can include a switch coupled between the control node of the pass element and the control node of the bypass element. The switch can be configured to activate a bypass mode of the voltage regulator circuit (i.e., a "soft" transition as opposed to a "hard" transition) by controlling a bypass transition voltage at the output node of the voltage regulator circuit. Like the controlled pressure drop transition voltage, the controlled bypass transition voltage can have a more gradual transition than an uncontrolled transition. In this way, the controlled bypass transition voltage can advantageously limit inrush current during the transition to the bypass mode.

[0048] The OCP control circuit includes an additional switch coupled between the control node of the pass element and the control node of the bypass element. For example, the switch of the bypass transition circuit can be a "soft" switch, while the additional switch of the OCP control circuit can be a "hard" switch. The additional switch can be configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of the bypass mode. For example, during the bypass mode transition, the control nodes can be connected through a resistor, while after the bypass mode transition, the control nodes can be shorted.

[0049] The embodiment voltage regulation circuits described herein can advantageously enable activation of a bypass mode without introducing the risk conditions associated with so-called "hard" start solutions. For example, high inrush currents that occur when switching to and from the bypass mode can be advantageously reduced or eliminated. That is, so-called "soft" activation / deactivation of the bypass mode can be advantageously provided. This can have the advantage of a fully under control activation / deactivation sequence (e.g., as opposed to conventional solutions that completely ignore the details of the transition between modes).

[0050] Furthermore, the embodiment voltage regulation circuits can advantageously obviate the need to simply increase the size of elements such as power transistors (e.g., power metal oxide conductor field effect transistors or MOSFETs) to reduce the voltage difference between VIN and VOUT of the voltage regulator during the bypass mode. This can advantageously avoid altering some or all of the voltage regulation parameters. Moreover, stability issues caused by larger components can also be avoided. As another benefit, the deterioration of transient response caused by larger components can also be prevented.

[0051] Another potential advantage of the embodiment voltage regulation circuits described herein is enabling protection of a voltage regulator (e.g., an LDO) from overcurrent events (OCP functionality) that can be used even when the bypass mode is activated. In addition, existing OCP circuitry of the voltage regulator can be used, thereby advantageously eliminating any need for additional OCP circuitry or controllers.

[0052] The examples provided below describe various voltage regulation circuits, particularly voltage regulation circuits that include one or more control circuits configured to control a transition to or from a bypass mode of the voltage regulation circuit. The description below describes embodiments. Figure 1 An example voltage regulation circuit is described. In Figure 2 An example illustration of a transition voltage when a bypass mode is enabled is provided. Using Figure 3A And Figure 3B Another example voltage regulation circuit is described. Using Figure 4 And Figure 5 Two example voltage drop transition control circuits are described. Using Figures 6A-8 Three more example voltage regulation circuits are described. Using Figures 9-11 Three example transitions are described using qualitative illustrations in Figure 12 An example method for activating a bypass mode of a voltage regulator is described.

[0053] Figure 1 An example voltage regulator circuit is illustrated that has a pass element coupled in parallel with a bypass element and includes a comparison circuit (such as an error amplifier circuit) coupled to a control node of the pass element and configured to compare a reference voltage to a feedback signal.

[0054] Referring to Figure 1 , the voltage regulator circuit 100 includes an input node 10 and an output node 12 with a pass element 14 (e.g., a transistor) coupled therebetween. A feedback divider 17 is coupled between the output node 12 and a ground node 11. A comparison circuit 18 (e.g., including an error amplifier as illustrated) is coupled between a control node 13 (e.g., a gate of a FET, a base of a bipolar junction transistor (BJT), etc.) of the pass element 14 and the feedback divider 17 as illustrated. For example, the feedback divider 17 can include resistors 15 (e.g., at least two) configured to output a voltage that is a predefined fraction of an input voltage.

[0055] During operation, the voltage regulator circuit 100 receives an input voltage VIN at the input node 10 and regulates the input voltage VIN to produce a regulated output voltage VOUT at the output node 12 by minimizing a voltage difference between a reference voltage Vref and a feedback signal 119 from the feedback divider 17 using the comparison circuit 18. That is, the comparison circuit 18 is configured to maintain a low voltage (ideally zero voltage) between the reference voltage Vref and the feedback signal 119. This can be referred to as a regulation mode of the voltage regulator circuit 100. In various embodiments, the voltage regulator circuit 100 is a linear regulator (such as a series configuration or a shunt configuration) and, in one embodiment, is a low-dropout regulator (LDO).

[0056] In addition to the regulation mode, the voltage regulator circuit 100 can also operate in a dropout mode (e.g., when the difference between VIN and VOUT decreases below the minimum voltage required to maintain regulation). When the voltage regulator circuit 100 is in dropout mode, the voltage drop across the pass element 14 (e.g., a power transistor) is determined by its resistance (e.g., the drain-source resistance (RDSon value) of a power MOSFET when operating in the linear region).

[0057] By including a bypass element 16 coupled in parallel with the pass element 14 between the input node 10 and the output node 12 in the voltage regulator circuit 100, the resistance of the path between the input node 10 and the output node 12 (including the pass element 14) can be further reduced. For example, when turned on (e.g., during dropout mode, when the open loop gain is small or non-existent), the bypass element 16 is configured to provide an additional current path from the input node 10 to the output node 12, thereby reducing the voltage difference between VIN and VOUT. This can be referred to as a bypass mode of the voltage regulator circuit 100. The bypass mode can be activated after the dropout mode is manually activated.

[0058] Switches can be included to control the voltage received at the control nodes of the pass element 14 and / or the bypass element 16. For example, as shown, switch A can control the connection of the output of the comparison circuit 18 to the control gate of the pass element 14 and the connection of VIN to the control gate of the bypass element 16. Similarly, switch B can control the connection of the control gates of the pass element 14 and the bypass element 16 to the ground node 11.

[0059] The pass element 14 and the bypass element 16 can be switch-like components configured to control the flow of current using the respective control nodes. For example, the pass element 14 and the bypass element 16 can be implemented as transistors, such as power transistors. In various embodiments, the pass element 14 is a FET, and in one embodiment, the pass element 14 is a MOSFET. The bypass element 16 can be similar to the pass element 14, but can have different device parameters. For example, the bypass element 16 can also be a power MOSFET, but can have a different area, channel length, doping, etc. Of course, the pass element 14 and the bypass element 16 can also be implemented using other component types (such as BJTs, insulated gate bipolar transistors (IGBTs), thyristors, etc.).

[0060] Figure 2 An example qualitative plot of the output voltage of a voltage regulator during controlled transitions to dropout and bypass modes of the voltage regulator is illustrated. Figure 2The qualitative illustration can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein. Like numbered elements can be as previously described.

[0061] Referring to Figure 2 The qualitative illustration 202 shows the input voltage VIN and the corresponding output voltage VOUT of a voltage regulator over time. During a regulation mode 20 of the voltage regulator, VOUT is at a regulated voltage level 21. Also shown below the illustration of VOUT is a bypass enable signal BYPASS ON, which can be in either a low state (e.g., logic “0”) or a high state (e.g., logic “1”). For example, BYPASS ON is in the low state during the regulation mode 20, indicating that the bypass mode of the voltage regulator has not been enabled.

[0062] When BYPASS ON changes to the high state, the voltage regulator enters a droop transition 222 characterized by a droop transition voltage 232 of VOUT. Once the droop transition voltage 232 (VOUT) reaches a droop voltage level 23, the voltage regulator is in a droop mode 24. As shown, the droop transition voltage 232 is a so-called “soft” droop transition that transitions smoothly from the regulated voltage level 21 to the droop voltage level 23. That is, a so-called “hard” transition can be a substantially instantaneous voltage transition (e.g., similar to a step function on the illustrated time scale). In contrast, the soft droop transition shown by the droop transition voltage 232 is a controlled, smooth transition from the regulation mode 20 to the droop mode 24 (i.e., as opposed to an uncontrolled voltage transition).

[0063] In one embodiment, the shape of the droop transition voltage 232 is a substantially linear voltage curve (e.g., a “linearization” of an uncontrolled voltage curve). The substantially linear voltage curve can advantageously limit (i.e., reduce and / or eliminate) undesirable inrush current during the droop transition 222 after the droop mode 24 is activated. However, other shapes can be used for the droop transition voltage 232. The rate of the voltage transition (e.g., the slope of the substantially linear voltage curve) during the droop transition 222 can be controlled by control circuitry (e.g., droop transition control circuitry) included in the voltage regulator. For example, the rate of the droop transition 222 can be selected to limit inrush current to a desired range, the details of which can be determined by the particular capabilities of components in the voltage regulator, such as pass elements (e.g., power transistors).

[0064] After the voltage regulator is in the droop mode 24, the voltage regulator enters a bypass transition 225 characterized by a bypass transition voltage 235. During the bypass transition 225, the bypass transition voltage 235 (VOUT) transitions from the droop voltage level 23 to the bypass voltage level 27 and the voltage regulator is in the bypass mode 26. Similar to the soft droop transition in the droop transition 222, the bypass transition voltage 235 is a so-called "soft" bypass transition. In one embodiment, the shape of the bypass transition voltage 235 is a substantially exponential voltage curve approaching the bypass voltage level 27, although other shapes are certainly possible.

[0065] The soft bypass transition illustrated by the bypass transition voltage 235 is a controlled, gradual transition from the droop mode 24 to the bypass voltage level 27 (i.e., relative to an uncontrolled voltage transition). It should be noted that an uncontrolled voltage transition can resemble a step function on the time scale illustrated, but can appear as a substantially exponential voltage curve on a much smaller time scale. That is, the soft transitions described herein can have a different shape and different rate than a hard (i.e., uncontrolled) transition, or can have the same shape but a different (i.e., slower) rate. For example, the rate of the bypass transition 225 (e.g., the time constant of the substantially exponential voltage curve) can be controlled by control circuitry (e.g., bypass transition control circuitry) including resistive and capacitive elements in the voltage regulator to vary the RC constant to a desired value. Similar to the rate of the droop transition 222, the rate of the bypass transition 225 can be selected to limit inrush current to a desired range, which can be specific to details of a particular voltage regulator implementation.

[0066] Figure 3A FIGURE 1 illustrates an example voltage regulator circuit including a droop transition control circuit coupled to a feedback divider, according to an embodiment of the application, and Figure 3B FIGURE 2 illustrates a corresponding qualitative plot showing the output voltage of the voltage regulator circuit during a controlled droop transition, according to an embodiment of the application. Figure 3A The voltage regulator circuit of FIGURE 1 can be a specific implementation of other voltage regulator circuits, or combined with other voltage regulator circuits described herein. Like numbered elements can be as previously described.

[0067] Referring to Figure 3A and Figure 3BThe voltage regulator circuit 300 includes a pass element 14 coupled between the input node 10 and the output node 12. As before, a feedback divider 17 is coupled to the output node 12, and a comparison circuit 18 (e.g., including an error amplifier, as shown) receives a feedback signal 319 from the feedback divider 17, which is used in conjunction with a reference voltage Vref to regulate an output voltage VOUT at the output node 12. However, in contrast to the voltage regulator circuit 100 of Figure 1 In contrast to the voltage regulator circuit 100, the voltage regulator circuit 300 includes a voltage droop transition control circuit 330 coupled between the feedback divider 17 and the comparison circuit 18.

[0068] The voltage droop transition control circuit 330 is configured to manually transition the voltage regulator circuit 300 from the regulation mode 20 to the droop mode 24 by altering the resistance of the feedback divider 17 in a controlled manner by providing a controllable alternative path to the ground node 11. In particular, the voltage droop transition control circuit 330 is configured to implement a voltage droop transition 322 (soft voltage droop transition), as shown in the corresponding qualitative illustration 302. To this end, the voltage droop transition control circuit 330 can be considered or include a voltage ramp circuit. For example, the voltage droop transition control circuit 330 can include a switching element (such as a transistor) that can be turned on in a controlled manner (e.g., slowly turned on relative to an instantaneous switch).

[0069] It should be noted that, for brevity and clarity, a convention is adopted herein and hereafter in which elements following the pattern [x22] (where "x" is a figure number) can be relevant implementations of voltage droop transitions in various embodiments. For example, unless otherwise noted, the voltage droop transition 322 can be similar to the voltage droop transition 222. A similar convention is adopted for other elements, as can be made explicit by the use of similar terminology in conjunction with the numbering system mentioned above.

[0070] In theory, instead of reducing the resistance of the feedback divider 17, Vref could also be slowly increased to provide a similar effect. However, this can not be possible in practice, as the complementary differential pair of the voltage regulator can be important for the operation of the voltage regulator circuit 300. Thus, the voltage droop transition control circuit 330 has the advantage of enabling manual activation of the droop mode 24, while still maintaining the desired functionality of the voltage regulator circuit 300.

[0071] Qualitative illustration 302 shows a droop transition 322 activated using the BYPASS_ON signal. For example, this can be a bypass mode turning on the voltage regulator circuit 300 during normal operation (i.e., regulation mode 20). However, the details of the droop transition 322 of the voltage regulator circuit 300 do not preclude the case where the droop mode 24 is enabled in order to subsequently enter the bypass mode (e.g., such as in the case of the qualitative illustration 202). For example, as shown in the qualitative illustration 302, the droop transition control circuit 330 is only used to limit the inrush current during the droop transition 322, and does not at all require the bypass mode.

[0072] Figure 4 illustrates an example droop transition control circuit including a ramp generator circuit coupled to a ramp control element according to an embodiment of the application. Figure 4 The droop transition circuit of Figure 3A The droop transition circuit of Like numbered elements are as described before.

[0073] Reference is made to Figure 4 The droop transition control circuit 430 includes a feedback divider 17 coupled between the output node 12 and the ground node 11. In addition to the resistor R1 and the resistor R2 of the feedback divider 17, the feedback network is extended to include an additional resistor. For example, a ramp control element 42 is coupled between the feedback divider 17 and the ground node 11, enclosed by a resistor R3 and a resistor R4. Also included is a ramp generator circuit 440 configured to generate a ramp voltage at an output OUT coupled to the ramp control element 42. The ramp voltage can correspond to a signal received at an input of the ramp generator circuit 440, such as a ramp inhibit signal (ramp_inh) as shown.

[0074] Another resistor R5 can also be included between the resistor R3 and the feedback divider 17. A ramp bypass element 44 can be coupled in parallel with the resistor R5. The ramp bypass element 44 can be controlled by the same signal as the ramp generator circuit 440 (e.g., ramp_inh). However, if the resistance of the resistor R1 is high enough, then the resistor R5 can not be included and the connection between R3 and the feedback divider 17 can instead be shorted.

[0075] The droop transition control circuit 430 is configured to slowly turn on the ramp control element 42 using OUT generated by the ramp generator circuit 440. As VOUT increases, the output capacitor can be charged by the current (e.g., at a maximum rate of dV / dT = I LIM / C OUT where I LIM is the maximum allowed load current (OCP limit current), and COUT is an output capacitor of the voltage regulator). The voltage droop transition control circuit 430 can advantageously be easy to implement while still achieving the desired limitation of inrush current.

[0076] Figure 5 Fig. 1 1 illustrates another example voltage droop transition control circuit comprising a ramp generator circuit coupled to a ramp control element, the ramp generator circuit comprising a current source, according to an embodiment of the application. For example, Figure 5 The voltage droop transition circuit of Fig. 1 1 can be a specific implementation of other voltage droop transition circuits described herein, such as Figure 3A The voltage droop transition circuit of Fig. 1 1. Like-numbered elements are as previously described.

[0077] With reference to Figure 5 The voltage droop transition control circuit 530 comprises a feedback divider 17 coupled between the output node 12 and the ground node 1 1. As previously discussed, the feedback divider 17 is extended to comprise a feedback network comprising a ramp control element 42, an additional resistor and a ramp bypass element 44. A ramp generator circuit 540 is coupled to the control node 13 of the ramp control element 42.

[0078] The ramp generator circuit 540 comprises an input INH receiving a signal ramp_inh. An inverter 61 can be included to invert a ramp enable signal (ramp_en) to provide the ramp inhibit signal (ramp_inh) at the input INH. The ramp generator circuit 540 further comprises a current source 52 and a capacitor 63 coupled in series between the supply and the ground node 1 1.

[0079] A first inhibit switch 54 is coupled in parallel with the current source 52, while a second inhibit switch 56 is coupled in parallel with the capacitor 63. Both the first inhibit switch 54 and the second inhibit switch 56 comprise a control node coupled to INH (and thus, in this case, controlled by the ramp_inh signal).

[0080] Optionally, to allow the ramp generator circuit 540 to use the normal start-up mode of the voltage regulator when enabling the bypass mode before the voltage regulator is enabled, a regulator enable switch 58 can optionally be coupled in parallel with the current source 52 and comprise a control node coupled to a gated flip-flop 50 through an inverter. For example, the gated flip-flop 50 can receive the input voltage VIN of the voltage regulator at a D input, the regulator enable signal (EN_REG) at a clock input (CLK), and the bypass mode activation signal bp_act at an enable input (EN). At the same time, the gated flip-flop 50 can output (at a Q output) a bypass first signal bp_before_en_act indicating whether the bypass mode has been enabled before the regulator itself is enabled.

[0081] As shown in the figure, when ramp_inh is low and bp_before_en_act is low (e.g., indicating ramp is enabled, ramp_en = high), the voltage drop transition control circuit 530 is configured to generate a ramp voltage at OUT to slowly turn on the ramp control element 42. That is, current source 52 charges capacitor 63, and then capacitor 63 generates a ramp voltage at OUT. Of course, other arrangements, including alternative signaling arrangements, are also possible, as will be apparent to those skilled in the art.

[0082] Figure 6A An example voltage regulator circuit according to an embodiment of the present invention is illustrated, comprising a bypass transition control circuit including a bypass switch configured to provide a "soft" connection to activate a bypass mode of the voltage regulator circuit, and... Figure 6B The illustration shows a qualitative diagram of the output voltage of a voltage regulator circuit during a controlled bypass transition, according to an embodiment of the present invention. Figure 3A The voltage regulator circuit may be a specific implementation of other voltage regulator circuits or a combination thereof with other voltage regulator circuits described herein. Components marked similarly may be as previously described.

[0083] refer to Figure 6A and Figure 6B The voltage regulator circuit 600 includes a pass element 14 coupled between the input node 10 and the output node 12. Similar to the voltage regulator circuit described above, the voltage regulator circuit 600 also includes a bypass element 16 coupled in parallel with the pass element 14. The voltage regulator circuit 600 also includes a bypass transition control circuit 60 coupled between the control node of the pass element 14 and the bypass element 16 and the input node 10.

[0084] The bypass transition control circuit 60 is configured to manually transition the voltage regulator circuit 600 to bypass mode 26, as shown in the corresponding qualitative diagram 602. The bypass transition 625 may not be feasible before the voltage regulator circuit 600 is at dropout voltage level 23. For example, the voltage regulator circuit 600 may need no open-loop gain (as shown in dropout voltage level 23) before transitioning to bypass mode 26. The details of how the voltage regulator circuit 600 enters dropout mode 24 may be unimportant (as shown by the dashed line of BYPASS_ON before bypass transition 625).

[0085] In various embodiments, a signal to enable the bypass mode (e.g., BYPASS_ON) occurs prior to the bypass transition 625. In one embodiment, the bypass transition 625 is triggered by the voltage regulator circuit 600 detecting that the dropout mode 24 has been reached. Alternatively, another signal can be used to directly trigger the bypass transition 625 (e.g., if the voltage regulator is already in dropout mode).

[0086] The bypass transition control circuit 60 can include a bypass switch 62 (e.g., a soft gate connection switch) coupled between the input node 10 and the control nodes of the pass element 14 and the bypass element 16. For example, as shown, the bypass switch 62 can include a pair of switching elements (here shown as a p-type MOSFET and an n-type MOSFET) coupled in parallel between the control nodes of the pass element 14 and the bypass element 16. The opposite transistor types can be combined with one or more inverters to facilitate a bidirectional switch for the bypass switch 62.

[0087] The pair of switching elements can be controlled by a connection activation gate_con_act signal (e.g., a gate connection activation signal) and can be configured to connect the control nodes (e.g., gates in a cast of FETs) through a resistor R6. The connection can be a soft connection controlled by an RC constant of the circuit. For example, the RC constant can depend at least on the resistance of R6 and the gate capacitance CGS of the pass element 14 and / or the bypass element 16. In this way, the RC constant can be predetermined in order to provide a desired characteristic of the bypass transition voltage 635. The connection of the gates to VIN can be controlled using another switching element coupled between the control node of the bypass element 16 and VIN. Another resistor R7 can optionally be included in series.

[0088] The connection of the control nodes of the pass element 14 and the bypass element 16 can transition the voltage regulator circuit 600 to the bypass mode 26. For example, prior to the connection of the control nodes, VOUT can be at the dropout voltage level 23, while after the connection of the control nodes, VOUT transitions to the bypass voltage level 27. The control node connection can begin immediately upon the voltage regulator circuit 600 being in the dropout mode 24. Alternatively, the control node connection can be delayed for a predetermined length of time after the voltage regulator circuit 600 enters the dropout mode 24.

[0089] Figure 7 FIG. 1 illustrates an example voltage regulator circuit including a bypass transition control circuit and an overcurrent protection control circuit configured to provide a "hard" connection during an overcurrent event, according to an embodiment of the application. For example, the voltage regulator circuit can be the voltage regulator circuit of FIG. 1. Figure 7 The voltage regulator circuit of FIG. 1 can be other voltage regulator circuits (such as the voltage regulator circuit of FIG. 1) that include a bypass transition control circuit and an overcurrent protection control circuit configured to provide a "hard" connection during an overcurrent event. Figure 6Athe specific embodiments of the voltage regulator circuit of FIG. 1, or in combination with other voltage regulator circuits described herein. Like numbered elements can be as previously described.

[0090] In conventional voltage regulation circuits that allow for manual activation of the bypass mode, protection from overcurrent events can not be provided. That is, during activation and deactivation of the bypass mode, if an overcurrent event occurs, then conventional voltage regulator circuits are not protected. Referring to Figure 7 , the voltage regulator circuit 700 is similar to the voltage regulator circuit 600 of FIG. 1, except that it further includes an OCP control circuit 770 (not to be confused with the OCP circuitry of the voltage regulator circuit 700 that can already be present). Figure 6A In contrast to conventional circuits, the bypass transition control circuit 60 of the voltage regulator circuit 700 allows for manual activation and deactivation of the bypass mode, while the OCP control circuit 770 is configured to provide OCP functionality throughout the bypass transition (e.g., using existing OCP circuitry).

[0091] The voltage regulator circuit 700 further includes an OCP pass element 74 and an OCP bypass element 75 coupled in parallel. A control node of the OCP pass element 74 is coupled to the control node of the pass element 14, while a control node of the OCP bypass element 75 is coupled to the control node of the bypass element 16. In various embodiments, the OCP pass element 74 and the OCP bypass element 75 are replica transistors corresponding to the pass element 14 and the bypass element 16, also implemented as transistors. The OCP pass element 74 and the OCP bypass element 75 can be configured to provide protection for components of the voltage regulator circuit 700 during overcurrent events during the regulation mode, while the OCP control circuit 770 extends this functionality to also include transitions to and from the bypass mode.

[0092] The maximum allowed load current is the limit current (ILIM). When an additional pass element (i.e., the bypass element 16) is connected, ILIM is increased and an additional replica pass element (the OCP bypass element 75) should also be connected. The OCP bypass element 75 is sized appropriately to provide OCP functionality when the bypass element 16 is on. However, this only provides OCP functionality during the regulation mode and the bypass mode, and not during the transition between the two.

[0093] The OCP control circuit 770 includes an OCP switch 72 configured to provide a low resistance connection 73 between the control nodes of the pass element 14 and the bypass element 16. Unlike the bypass switch 62, which uses a resistor to create a soft control node connection (e.g., a soft gate connection), the low resistance connection 73 is a hard control node connection (e.g., a hard gate connection) configured to fully connect the control nodes with little or no hysteresis. For example, a bidirectional switch can be connected to the OCP activation signal ocp act. When ocp act is “1,” the bidirectional switch can turn on. Similarly, a switch can be included in the OCP control circuit 770 that is coupled between the input node 10 and the control node. This switch can also turn on when ocp act is “1.”

[0094] The OCP control circuit 770 is configured to provide protection when an overcurrent event (ocp act) occurs during the connection of the control nodes of the pass element 14 and the bypass element 16 to gate the bypass mode (gate_con_act). An AND gate 78 and appropriate inverters are included to turn on the switch between the input node 10 and the control node when ocp act is “1” and gate_con_act = “1.” This occurs immediately once the conditions are met.

[0095] However, the bidirectional switch connecting the control nodes itself is configured to turn on after the transition to the bypass mode is complete. Specifically, a rising edge delay 76 is included that delays the rising edge of gate_con_act, resulting in a delayed signal 77 (e.g., delayed by the activation of the bypass mode). The delayed signal 77 and ocp act are inputs to an XOR gate 79 that has an output coupled to the AND gate 78 that is coupled to gate_con_act.

[0096] It can be advantageous to introduce a low resistance between the control nodes (e.g., gates). For example, the OCP control circuit 770 controls the control node of the pass element 14 (e.g., a power MOSFET of the voltage regulator circuit 700). It can be important that the control node of the OCP pass element 74 (e.g., an additional power MOSFET) is not “lagged” by a high resistance. Thus, a “hard” connection (e.g., a hard gate connection) is used. That is, the hard switch is activated immediately upon receiving the overcurrent event signal.

[0097] However, if the overcurrent event occurs during a soft connection of the control node (e.g., the gate), it may be better to introduce low resistance when the soft connection of the gate ends. Therefore, a "hard" connection (e.g., a hard gate connection) can be made based on a timer (e.g., using a rising edge delay of 76). In other words, the hard switch is also activated after a specified delay time, which is at least as long as the soft connection of the gates of the path and bypass element. In this case, the OCP switch 72 can be considered a delayed hard gate connection switch. Conversely, if the overcurrent event occurs during a soft disconnect of the control node (e.g., the gate), then the control node of the OCP bypass element 75 should be immediately coupled to VIN.

[0098] Figure 8 The illustration shows another example voltage regulator circuit according to an embodiment of the present invention, including a voltage drop transition control circuit, a bypass transition control circuit, and an overcurrent protection control circuit. For example, Figure 8 The voltage regulator circuit can be other voltage regulator circuits (such as...) Figure 7 The specific implementation of the voltage regulator circuit, or its combination with other voltage regulator circuits described herein. Components with similar markings may be as previously described.

[0099] refer to Figure 8 In addition to including additional components constituting the OCP control circuit 870 to demonstrate an example configuration of a voltage regulator circuit including both the bypass transition control circuit 60 and the voltage drop transition control circuit 830, the voltage regulator circuit 800 and Figure 7 The voltage regulator circuit 700 is similar. It includes asynchronous logic 88 to facilitate a soft connection of the control node (using bypass transition control circuit 60) when the voltage drop detector 82 detects a voltage drop mode. That is, the voltage drop detector 82 is configured to detect that the voltage regulator circuit 800 is in a voltage drop mode and generate a corresponding signal.

[0100] The BP_ON and EN_REG signals are used as inputs to an AND gate to manually activate the dropout mode. The output of this AND gate is fed to both a falling edge delay 86 (which generates ramp_enh as the output) and asynchronous logic 88. The ramp_enh signal is inverted to generate the ramp_inh signal, which is then provided to the ramp generator circuit 540.

[0101] After the overcurrent event, the resistance of the feedback network can be set back to the normal value. After the bypass mode has been activated (e.g., the gates of the pass elements are connected together), the bypass mode can also be manually turned off by setting the signal BP EN = "0." In this case, the order is reversed compared to the activation sequence: first, the gates of the pass elements and the bypass elements are again disconnected in a soft manner, and then, after a defined time delay (falling edge delay 86) covering the time needed for the gate soft disconnection, the resistance of the feedback network can be set back to the normal value. This can be performed in a "hard" switching manner (i.e., without considering potential inrush currents). Then, the voltage regulator circuit 800 will return to the normal regulation mode, and (assuming the voltage regulator is not push-pull) VOUT can be discharged through the load resistance (e.g., over a period of time).

[0102] The voltage regulator circuit 800 illustrates one example of how several control circuits (e.g., the droop transition control circuit 830, the bypass transition control circuit 60, and the OCP control circuit 870) can be implemented in a single voltage regulator circuit. However, it can be apparent to those skilled in the art that various aspects of the control circuits can be altered to suit a particular application. For example, while generally advantageous, the OCP functionality can be omitted while still retaining both droop transition control and bypass transition control (e.g., still generating VOUT transition voltage curves such as those shown in the other figures, but without the OCP functionality). Figure 2

[0103] Figure 9 FIG. 1 illustrates an example qualitative plot showing various voltages and output currents of a voltage regulator during a controlled transition of the voltage regulator from a regulation mode to a bypass mode, according to an embodiment of the present application. For example, Figure 9 The qualitative plot of FIG. 1 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIG. 8. Figure 8 The qualitative plot of FIG. 1 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIG. 8.

[0104] Referring to Figure 9 The qualitative plot 902 shows the input voltage VIN and the output voltage VOUT of the voltage regulator after the bypass mode has been manually enabled using the BP ON signal. Initially, the voltage regulator is in the regulation mode and VOUT is at the regulated output voltage. After BP ON goes high, the control circuitry (e.g., the droop transition control circuitry including the ramp generator circuit) facilitates a controlled transition of VOUT from the regulated output voltage to a droop voltage level (droop mode). The output current IOUT is shown to illustrate the inrush current 90 during the transition. Here, the inrush current 90 rises but is limited during the transition.

[0105] ​After the voltage regulator is in the buck mode, the control circuitry (e.g., bypass transition control circuit including soft gate connection switches) causes VOUT to be controlled to transition from the buck voltage level to a bypass voltage level (e.g., near VIN) and the voltage regulator is in the bypass mode. Again, the inrush current 90 is briefly elevated, but limited during the transition.

[0106] The bypass mode can also be manually turned off to return the voltage regulator to normal regulation mode operation. Figure 10 FIGURE 1 illustrates an example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode, according to embodiments of the application. For example, Figure 10 The qualitative plot of FIGURE 1 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIGURE 1. Figure 8 The qualitative plot of FIGURE 1 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIGURE 1.

[0107] Referring to FIGURE 1, Figure 10 The qualitative plot 1002 shows VOUT at a bypass voltage level while the BP ON signal is high, indicating the voltage regulator is in the bypass mode. Once BP ON goes low, the control circuitry (e.g., bypass transition control circuit including soft gate connection switches) facilitates a controlled transition to a buck voltage level (e.g., by performing a soft turn-off of the gates of the pass and bypass transistors). As shown, this transition has little effect on the inrush current 90.

[0108] Once in the buck mode, the control circuitry (e.g., buck transition control circuit including ramp generator circuit) facilitates a controlled transition of VOUT to a regulated voltage level. The output current IOUT drops to zero during the voltage ramp, and then the inrush current 90 increases as the voltage regulator re-enters regulation mode. Again, the inrush current 90 is limited by the controlled transition.

[0109] The bypass mode can also be manually turned off to return the voltage regulator to normal regulation mode operation. Figure 11 FIGURE 2 illustrates another example qualitative plot showing various voltages and output current of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode when the voltage regulator is enabled prior to being enabled, according to embodiments of the application. For example, Figure 11 The qualitative plot of FIGURE 2 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIGURE 1. Figure 8 The qualitative plot of FIGURE 2 can be a qualitative representation of the behavior of various voltage regulators (i.e., voltage regulation circuits) described herein, such as the voltage regulator circuit of FIGURE 1.

[0110] Referring to FIGURE 2, Figure 11qualitative diagram 1102 shows BP ON initially high and EN REG low, indicating that the bypass mode of the voltage regulator has been enabled, but the voltage regulator itself has not been enabled. Thus, the voltage regulator receives the input voltage VIN and has no output voltage VOUT. In this scenario, it is possible to barely turn on the ramp control element (e.g., a transistor acting as a switch in a feedback network of a dropout transition control circuit coupled to a feedback divider) to provide soft start by the voltage regulator's soft start implementation itself. The soft start ramp can be adjusted to have the desired characteristics.

[0111] As shown, once the voltage regulator is enabled, VOUT ramps up from zero to the dropout voltage level in a controlled transition, and then performs a controlled transition to bypass mode. As before, there are two peaks of inrush current 90, corresponding to the transition to dropout mode and the transition to bypass mode, but the inrush current 90 is limited by the controlled transitions. Compared to the transition from regulation mode to dropout mode shown in qualitative diagram 902, the transition from zero to dropout mode here widens the peaks of inrush current 90, but the behavior of output current IOUT is otherwise similar.

[0112] Figure 12 An example method of activating a bypass mode of a voltage regulator is illustrated, in accordance with an embodiment of the application. Figure 12 The method of Figure 12 The method of Figures 1-11 may be combined with any of the embodiments in Figure 12 The arrangement and numbering of steps of Figure 12 The method steps of

[0113] Reference is made to Figure 12 The method 1209 of activating a bypass mode of a voltage regulator includes a step 1201 of generating a regulated output voltage at an output node of the voltage regulator. Then, in step 1202, a dropout mode of the voltage regulator is activated by controlling a dropout transition from the regulated output voltage to a dropout voltage level using a dropout transition control circuit coupled to a feedback divider, wherein the feedback divider is coupled between the output node and a ground node, to limit an inrush current. In step 1203, a bypass mode of the voltage regulator is activated by turning on a bypass element coupled in parallel with a pass element coupled between the output node and an input node of the voltage regulator.

[0114] Example embodiments of the application are summarized here. Other embodiments can be understood from the entire specification and claims submitted herewith.

[0115] Example 1. A voltage regulator circuit comprising: an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element coupled between the input node and the output node; a bypass element coupled in parallel with the pass element; a feedback voltage divider coupled between the output node and a ground node, the feedback voltage divider configured to produce a feedback signal indicative of the regulated output voltage; an error amplifier circuit coupled between a control node of the pass element and the feedback voltage divider, the error amplifier circuit configured to minimize a voltage difference between a reference voltage and the feedback signal; and a brown-out transition control circuit coupled to the feedback voltage divider and configured to activate a brown-out mode of the voltage regulator circuit to limit an inrush current by controlling a brown-out transition at the output node from the regulated output voltage to a brown-out voltage level.

[0116] Example 2. The voltage regulator circuit of example 1, wherein the brown-out transition control circuit is further configured to activate the brown-out mode to limit the inrush current by making the brown-out transition a substantially linear voltage curve.

[0117] Example 3. The voltage regulator circuit of one of examples 1 and 2, further comprising: a bypass transition control circuit comprising a bypass switch coupled between the control node of the pass element and a control node of the bypass element, the bypass switch configured to activate a bypass mode of the voltage regulator circuit to further limit the inrush current by controlling a bypass transition at the output node from the brown-out voltage level to a bypass voltage level.

[0118] Example 4. The voltage regulator circuit of example 3, wherein the bypass switch is further configured to activate the bypass mode to further limit the inrush current by making the bypass transition a substantially exponential voltage curve proximate the bypass voltage level.

[0119] Example 5. The voltage regulator circuit of example 4, wherein the bypass transition control circuit further comprises a resistor coupled between the control node of the pass element and the control node of the bypass element, and wherein the substantially exponential voltage curve is controlled according to an RC constant determined by the resistor and a capacitance between the control node and the input node.

[0120] Example 6. The voltage regulator circuit of example 5, wherein the pass element and the bypass element are field effect transistors, the control node of the pass element and the control node of the bypass element are gates, and wherein the capacitance is a gate capacitance.

[0121] Example 7. The voltage regulator circuit of one of examples 3 to 6, wherein the bypass transition control circuit is configured to trigger the bypass switch in response to detecting that the voltage regulator circuit is in the brown-out mode.

[0122] Example 8. The voltage regulator circuit of one of Examples 3 to 7, further comprising an overcurrent protection (OCP) control circuit including an OCP switch coupled between the control node of the pass element and the control node of the bypass element, the OCP switch configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0123] Example 9. A method of activating a bypass mode of a voltage regulator, the method comprising: generating a regulated output voltage at an output node of the voltage regulator; activating a droop mode of the voltage regulator circuit to limit an inrush current by controlling a droop transition from the regulated output voltage to a droop voltage level using a droop transition control circuit coupled to a feedback voltage divider, wherein the feedback voltage divider is coupled between the output node and a ground node; and activating a bypass mode of the voltage regulator by turning on a bypass element coupled in parallel with a pass element coupled between an output node and an input node of the voltage regulator.

[0124] Example 10. The method of Example 9, wherein activating the droop mode comprises making the droop transition a substantially linear voltage curve to limit the inrush current.

[0125] Example 11. The method of one of Examples 9 and 10, wherein activating the bypass mode comprises connecting a control node of the pass element and a control node of the bypass element while controlling a bypass transition from the droop voltage level to a bypass voltage level using a bypass transition control circuit coupled between the control nodes to limit the inrush current.

[0126] Example 12. The method of Example 11, further comprising: deactivating the bypass mode by disconnecting the control node of the pass element and the control node of the bypass element while controlling a bypass transition from the bypass voltage level to the droop voltage level using the bypass transition control circuit to further limit the inrush current; and activating a regulation mode of the voltage regulator by controlling a droop transition from the droop voltage level to the regulated output voltage using the droop transition control circuit to further limit the inrush current.

[0127] Example 13. The method of one of Examples 11 and 12, wherein activating the bypass mode further comprises making the droop transition a substantially exponential voltage curve approaching the bypass voltage level to further limit the inrush current.

[0128] Example 14. The method of Example 13, wherein the substantially exponential voltage curve is controlled according to a predetermined RC constant.

[0129] Example 15. The method of one of Examples 9 to 14, further comprising providing a low resistance connection between the control node of the pass element and the control node of the bypass element during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0130] Example 16. The method of one of Examples 9 to 15, further comprising providing a bypass mode activation signal prior to activating the drop-out mode, the bypass mode activation signal initiating activation of the drop-out mode; and initiating activation of the bypass mode in response to the bypass mode activation signal and detecting that the voltage regulator is in the drop-out mode.

[0131] Example 17. The method of Example 16, further comprising enabling the bypass mode of the voltage regulator prior to enabling the regulation mode of the voltage regulator.

[0132] Example 18. The method of one of Examples 9 to 17, further comprising providing a low resistance connection between the control node of the pass element and the control node of the bypass element during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0133] Example 19. A voltage regulator circuit, comprising: an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element and a bypass element coupled in parallel between the input node and the output node; an overcurrent protection (OCP) pass element and an OCP bypass element coupled in parallel to the input node, a control node of the OCP pass element coupled to a control node of the pass element and a control node of the OCP bypass element coupled to a control node of the bypass element; a bypass transition control circuit comprising a soft gate connection switch coupled between the control node of the pass element and the control node of the bypass element, the soft gate connection switch configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition at the output node to limit inrush current while turning on the bypass element; and an OCP control circuit comprising a delayed hard gate connection switch coupled between the control node of the pass element and the control node of the bypass element, the delayed hard gate connection switch configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0134] Example 20. The voltage regulator circuit of example 19, further comprising: a feedback voltage divider coupled between the output node and a ground node, the feedback voltage divider configured to produce a feedback signal indicative of the regulated output voltage; an error amplifier circuit coupled between the control node of the pass element and the feedback voltage divider, the error amplifier circuit configured to compare the reference voltage to the feedback signal; and a voltage droop transition control circuit coupled to the feedback voltage divider and configured to activate the voltage droop mode of the voltage regulator circuit by controlling a voltage droop transition at the output node from the regulated output voltage to the voltage droop level to further limit the inrush current.

[0135] Example 21. The voltage regulator circuit of example 20, wherein the voltage droop transition control circuit is further configured to activate the voltage droop mode to further limit the inrush current by making the voltage droop transition a substantially linear voltage curve.

[0136] Example 22. The voltage regulator circuit of one of examples 19 to 21, wherein the soft gate connection switch is further configured to activate the bypass mode to further limit the inrush current by making the bypass transition a substantially exponential voltage curve that approaches the bypass voltage level.

[0137] Example 23. The voltage regulator circuit of example 22, wherein the bypass transition is from the voltage droop level to the bypass voltage level.

[0138] Example 24. The voltage regulator circuit of one of examples 19 to 23, wherein the bypass transition control circuit is configured to trigger the soft gate connection switch in response to detecting that the voltage regulator circuit is in the voltage droop mode.

[0139] While the application has been described with reference to illustrative embodiments, the description is not intended to be limiting. Various modifications and combinations of the illustrative embodiments as well as additional embodiments of the application will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims shall cover any such modifications or embodiments.

Claims

1. A voltage regulator circuit, characterized by, includes: an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element coupled between the input node and the output node; a bypass element coupled in parallel with the pass element; a feedback voltage divider coupled between the output node and a ground node, the feedback voltage divider configured to produce a feedback signal indicative of the regulated output voltage; an error amplifier circuit coupled between a control node of the pass element and the feedback voltage divider, the error amplifier circuit configured to minimize a voltage difference between a reference voltage and the feedback signal; and a drop transition control circuit coupled to the feedback voltage divider and configured to activate a drop mode of the voltage regulator circuit by controlling a drop transition at the output node from the regulated output voltage to a drop voltage level to limit an inrush current. wherein the drop transition control circuit is further configured to activate the drop mode to limit the inrush current by making the drop transition a substantially linear voltage curve.

2. The voltage regulator circuit of claim 1, wherein, further includes:

3. The voltage regulator circuit of claim 1, wherein, a bypass transition control circuit including a bypass switch coupled between the control node of the pass element and a control node of the bypass element, the bypass switch configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition at the output node from the drop voltage level to a bypass voltage level to further limit the inrush current. wherein the bypass switch is further configured to activate the bypass mode to further limit the inrush current by making the bypass transition a substantially exponential voltage curve near the bypass voltage level.

4. The voltage regulator circuit of claim 3, wherein, 5. The voltage regulator circuit of claim 4, wherein: the bypass transition control circuit further includes a resistor coupled between the control node of the pass element and the control node of the bypass element, and the substantially exponential voltage curve is controlled according to an RC constant determined by a capacitance between the control node and the input node and the resistor. wherein the bypass transition control circuit is configured to trigger the bypass switch in response to detecting that the voltage regulator circuit is in the drop mode.

6. The voltage regulator circuit of claim 3, wherein, further includes an overcurrent protection control circuit including an overcurrent protection switch coupled between the control node of the pass element and the control node of the bypass element, the overcurrent protection switch configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

7. The voltage regulator circuit of claim 3, wherein, includes:

8. A voltage regulator circuit, characterized by an input node configured to receive an input voltage; an output node configured to produce a regulated output voltage; a pass element and a bypass element coupled in parallel between the input node and the output node; an overcurrent protection pass element and an overcurrent protection bypass element coupled in parallel to the input node, a control node of the overcurrent protection pass element coupled to a control node of the pass element, and a control node of the overcurrent protection bypass element coupled to a control node of the bypass element; a bypass transition control circuit including a soft gate connection switch coupled between the control node of the pass element and the control node of the bypass element, the soft gate connection switch configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition at the output node to limit an inrush current while turning on the bypass element; and a drop transition control circuit coupled to the feedback voltage divider and configured to activate a drop mode of the voltage regulator circuit by controlling a drop transition at the output node from the regulated output voltage to a drop voltage level to limit an inrush current. ​ An overcurrent protection control circuit includes a delayed hard gate connect switch coupled between a control node of a pass element and a control node of a bypass element, the delayed hard gate connect switch configured to provide a low resistance connection between the control nodes during an overcurrent event or immediately after a delay triggered by activation of a bypass mode.

9. The voltage regulator circuit of claim 8, wherein, Also included are: a feedback voltage divider coupled between an output node and a ground node, the feedback voltage divider configured to produce a feedback signal indicative of a regulated output voltage; an error amplifier circuit coupled between the control node of the pass element and the feedback voltage divider, the error amplifier circuit configured to compare a reference voltage to the feedback signal; and a droop transition control circuit coupled to the feedback voltage divider and configured to activate a droop mode of the voltage regulator circuit by controlling a droop transition at the output node from the regulated output voltage to a droop voltage level to further limit an inrush current.

10. The voltage regulator circuit of claim 9, wherein, wherein the droop transition control circuit is further configured to activate the droop mode by making the droop transition a substantially linear voltage curve to further limit the inrush current.

11. The voltage regulator circuit of claim 8, wherein, wherein the soft gate connect switch is further configured to activate the bypass mode by making the bypass transition a substantially exponential voltage curve proximate to the bypass voltage level to further limit the inrush current.

12. The voltage regulator circuit of claim 11, wherein, wherein the bypass transition is from the droop voltage level to the bypass voltage level.

13. The voltage regulator circuit of claim 8, wherein, wherein the bypass transition control circuit is configured to trigger the soft gate connect switch in response to detecting that the voltage regulator circuit is in the droop mode.

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