Voltage regulator bypass mode control circuit

Abstract

The invention 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 a method of operating the same. Background Art

[0002] A linear voltage regulator (such as a low dropout regulator, or LDO) 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 below the nominal regulation level. In dropout mode, the pass element (e.g., power transistor) operates in the linear region (i.e., fully turned on), and the output voltage is close to the input voltage.

[0003] In some specific applications, even in normal regulation mode, it may be desirable to "manually" activate dropout mode by the user. When this happens, the output voltage rises from the regulation level and approaches the input voltage in order to achieve the minimum voltage difference between the input and output voltages.

[0004] In order 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 voltage drop mode is activated, a bypass element can be connected in parallel with the pass element. When the bypass element is open (so-called bypass mode), the additional current path causes the voltage difference to be reduced.

[0005] Switching to bypass mode also introduces undesirable inrush current. Moreover, when dropout mode is activated, no over-current protection (OCP) is available. Therefore, a linear voltage regulator that reduces these undesirable characteristics when dropout mode is manually activated is desired. Summary of the invention

[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 generate 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 voltage drop transition control circuit coupled to the feedback voltage divider. The feedback voltage divider is configured to generate a feedback signal indicating the regulated output voltage. The error amplifier circuit is configured to minimize a voltage difference between a reference voltage and the feedback signal. The voltage drop transition control circuit is configured to activate a voltage drop mode of the voltage regulator circuit to limit inrush current by controlling a voltage drop transition at the output node from the regulated output voltage to a voltage drop voltage level.

[0007] According to another embodiment of the present invention, a method for activating a bypass mode of a voltage regulator includes: generating a regulated output voltage at an output node of the voltage regulator; activating the voltage drop mode of the voltage regulator circuit to limit inrush current by controlling a voltage drop transition from the regulated output voltage to a voltage drop voltage level using a voltage drop 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 the 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.

[0008] According to yet another embodiment of the present invention, a voltage regulator circuit includes: an input node configured to receive an input voltage; an output node configured to generate a regulated output voltage; a pass element and a bypass element coupled in parallel between the input node and the output node; an OCP pass element and an OCP bypass element coupled in parallel to the input node; a bypass transition control circuit including a soft gate connection switch; and an OCP control circuit including a delayed hard gate connection switch. The control node of the OCP pass element is coupled to the control node of the pass element. The control node of the OCP bypass element is coupled to the control node of the bypass element. The soft gate connection 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 connection switch is 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. The delayed hard gate connection switch of the OCP control circuit is coupled between the control node of the pass element and the control node of the bypass element. The delayed hard gate connection switch is configured to provide a low resistance connection between the control nodes immediately during an overcurrent event or after a delay triggered by activation of the bypass mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more complete understanding of the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0010] Figure 1 An example voltage regulator circuit is illustrated having a pass element coupled in parallel with a bypass element and including 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;

[0011] Figure 2 illustrates an example qualitative graph showing the output voltage of a voltage regulator during a controlled transition of the voltage regulator to a dropout mode and a bypass mode according to an embodiment of the present invention;

[0012] Figure 3illustrates an example voltage regulator circuit including a voltage drop transition control circuit coupled to a feedback voltage divider according to an embodiment of the present invention, and a corresponding qualitative graph showing an output voltage of the voltage regulator circuit during a controlled voltage drop transition;

[0013] Figure 4 An example voltage drop transition control circuit including a ramp generator circuit coupled to a ramp control element according to an embodiment of the present invention is illustrated;

[0014] Figure 5 Another example voltage drop transition control circuit is illustrated according to an embodiment of the present invention including a ramp generator circuit coupled to a ramp control element, the ramp generator circuit including a current source;

[0015] Figure 6 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, and a corresponding qualitative graph showing an output voltage of the voltage regulator circuit during a controlled bypass transition, according to an embodiment of the present invention;

[0016] Figure 7 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 is illustrated in accordance with an embodiment of the present invention;

[0017] Figure 8 Another example voltage regulator circuit including a voltage drop transition control circuit, a bypass transition control circuit, and an overcurrent protection control circuit according to an embodiment of the present invention is illustrated;

[0018] Fig. 9 illustrates example qualitative graphs 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 in accordance with an embodiment of the present invention;

[0019] Fig.10 illustrates example qualitative graphs showing various voltages and output currents of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode in accordance with an embodiment of the present invention;

[0020] Fig.11 illustrates another example qualitative graph showing various voltages and output currents of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode when the bypass mode is enabled before the voltage regulator is enabled in accordance with an embodiment of the present invention; and

[0021] Fig.12An example method of activating a bypass mode of a voltage regulator according to an embodiment of the present invention is illustrated.

[0022] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. These figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate the end of the range of the features. DETAILED DESCRIPTION

[0023] The making and using of various embodiments are discussed in detail below. However, it should be appreciated that the various embodiments described herein are applicable to various specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments, and should not be construed as limited in scope. Unless otherwise specified, the expressions "approximately," "approximately," and "substantially" mean within 10% of a given value, and preferably within 5%, or (such as in the case of substantially zero) less than 10% and preferably less than 5% of a comparable amount.

[0024] When activating or deactivating the bypass mode of a voltage regulator (e.g., a linear voltage regulator such as an LDO), it is important that the entire sequence is under control. Conventional methods of switching to and from bypass mode employ a "hard" switching solution. That is, connections are made in a binary manner so that the voltage level changes quickly without concern for the details of the transition. This results in large inrush currents that may be potentially dangerous to both the voltage regulator (and surrounding circuitry, such as a power management integrated circuit (IC), etc.) and to the system powered by the voltage regulator. Therefore, a solution for controlling the transition between the normal regulation mode and the bypass mode may be desired so that the inrush current is reduced and / or minimized.

[0025] Furthermore, conventional solutions do not provide any OCP functionality. It may be desirable to have an OCP functionality to ensure that the components remain protected from overcurrent events when activating and deactivating bypass mode and when in bypass mode. However, if the solution is too complex, then the OCP functionality in bypass mode may be made impractical, thereby disabling the functionality altogether. Therefore, it may be desirable to have a simple solution that controls the use of the OCP functionality already available in the voltage regulator itself.

[0026] There is an option to reduce the minimum voltage difference between VIN and VOUT when dropout mode is enabled. The voltage difference can be reduced by simply increasing the size of the pass and bypass elements, but this has many disadvantages, such as large changes in regulation parameters, reduced stability, and worse transient response of the voltage regulator. Bypass elements can also be connected in parallel when appropriate, but this cannot be done in normal regulation mode (e.g., due to high open-loop gain that would cause possible oscillations).

[0027] In various embodiments, the present invention provides a method for implementing a bypass mode in a voltage regulator, which bypass mode can be activated even 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 against overcurrent events (OCP functionality).

[0028] 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 with 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 indicating a voltage at the regulated output node.

[0029] A dropout transition control circuit coupled to the feedback voltage divider may be included in the voltage regulator circuit. The dropout transition control circuit is configured to activate a dropout mode of the voltage regulator circuit by controlling a dropout transition voltage at an output node of the voltage regulator circuit (i.e., a "soft" transition as opposed to an uncontrolled "hard" transition). For example, the controlled dropout transition voltage may transition more gradually between the regulated voltage and the dropout voltage level than an uncontrolled transition. The controlled dropout transition voltage may thereby advantageously limit inrush current during the transition to the dropout mode.

[0030] A bypass transition control circuit may also be included in the voltage regulator circuit. The bypass transition control circuit may include a switch coupled between a control node of the pass element and a control node of the bypass element. The switch may be configured to activate a bypass mode (i.e., a "soft" transition as opposed to a "hard" transition) of the voltage regulator circuit by controlling a bypass transition voltage at an output node of the voltage regulator circuit. Similar to the controlled dropout transition voltage, the controlled bypass transition voltage may have a smoother transition than an uncontrolled transition. In this way, the controlled bypass transition voltage may advantageously limit the inrush current during the transition to the bypass mode.

[0031] The OCP control circuit includes an additional switch coupled between a control node of the pass element and a control node of the bypass element. For example, the switch of the bypass transition circuit may be a "soft" switch, while the additional switch of the OCP control circuit may be a "hard" switch. The additional switch may be configured to provide a low resistance connection between the control nodes immediately during an overcurrent event or after a delay triggered by activation of the bypass mode. For example, during the bypass mode transition, the control nodes may be connected through a resistor, while after the bypass mode transition, the control nodes may be shorted.

[0032] Embodiment voltage regulation circuits described herein may advantageously enable activation of a bypass mode without introducing risk conditions associated with so-called "hard" start solutions. For example, high inrush currents that occur when switching to and from the bypass mode may advantageously be reduced or eliminated. That is, so-called "soft" activation / deactivation of the bypass mode may advantageously be provided. This may have the advantage of an activation / deactivation sequence that is completely under control (e.g., as opposed to conventional solutions that completely ignore the details of transitions between modes).

[0033] Furthermore, embodiment voltage regulation circuits can beneficially alleviate the need to simply increase the size of components 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 bypass mode. This can advantageously avoid changing some or all of the voltage regulation parameters. Moreover, stability issues caused by larger components can also be avoided. As another benefit, transient response degradation caused by larger components can also be prevented.

[0034] Another potential advantage of the embodiment voltage regulation circuit described herein is that it enables protection of the voltage regulator (e.g., LDO) from overcurrent events (OCP functionality), even when bypass mode is activated. In addition, the existing OCP circuitry of the voltage regulator can be used, thereby advantageously removing any need for additional OCP circuits or controllers.

[0035] The embodiments provided below describe various voltage regulating circuits, and in particular, voltage regulating circuits including one or more control circuits configured to control a transition to or from a bypass mode of the voltage regulating circuit.The following description describes embodiments. Figure 1 is used to describe an example voltage regulation circuit. Figure 2 Example graphs of the transition voltage when bypass mode is enabled are provided in . Figure 3 Another example voltage regulation circuit is described. Figure 4 and Figure 5 Two example voltage drop transition control circuits are described. Figure 6-8Three additional example voltage regulation circuits are described. Figure 9-11 The qualitative diagram in describes three example transitions, and Fig.12 An example method for describing activation of a bypass mode of a voltage regulator.

[0036] Figure 1 An example voltage regulator circuit is illustrated having a pass element coupled in parallel with a bypass element and including 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.

[0037] refer 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 voltage 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 shown) 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 voltage divider 17, as shown. For example, the feedback voltage divider 17 may include resistors 15 (e.g., at least two) configured to output a voltage that is a predefined fraction of the input voltage.

[0038] During operation, the voltage regulator circuit 100 receives an input voltage VIN at an input node 10 and regulates the input voltage VIN to produce a regulated output voltage VOUT at an output node 12 by minimizing the voltage difference between a reference voltage Vref and a feedback signal 119 from a feedback voltage divider 17 using a 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 may 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).

[0039] 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 a 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).

[0040] By including a bypass element 16 in the voltage regulator circuit 100 that is coupled in parallel with the pass element 14 between the input node 10 and the output node 12, 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 the voltage drop mode, when the open loop gain is small or there is no open loop gain), 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 voltage drop mode is manually activated.

[0041] Switches may be included to control the voltages received at the control nodes of pass element 14 and / or bypass element 16. For example, as shown, switch A may control the connection of the output of comparator circuit 18 to the control gate of pass element 14 and the connection of VIN to the control gate of bypass element 16. Similarly, switch B may control the connection of the control gates of pass element 14 and bypass element 16 to ground node 11.

[0042] Pass element 14 and bypass element 16 may be switch-like components configured to control the flow of current using corresponding control nodes. For example, pass element 14 and bypass element 16 may be implemented as transistors, such as power transistors. In various embodiments, pass element 14 is a FET, and in one embodiment, pass element 14 is a MOSFET. Bypass element 16 may be similar to pass element 14, but may have different device parameters. For example, bypass element 16 may also be a power MOSFET, but may have different areas, channel lengths, doping, etc. Of course, pass element 14 and bypass element 16 may also be implemented using other component types (such as BJTs, insulated gate bipolar transistors (IGBTs), thyristors, etc.).

[0043] Figure 2 An example qualitative graph of the output voltage of a voltage regulator during controlled transitions to a dropout mode and a bypass mode of the voltage regulator according to an embodiment of the present invention is illustrated. Figure 2 The qualitative diagram of may be a qualitative representation of the behavior of the various voltage regulators (ie, voltage regulating circuits) described herein. Like labeled elements may be as previously described.

[0044] refer to Figure 2, qualitative graph 202 shows the change of input voltage VIN and corresponding output voltage VOUT of the voltage regulator over time. During the regulation mode 20 of the voltage regulator, VOUT is at a regulated voltage level 21. Also shown below the graph 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 a low state during the regulation mode 20, indicating that the bypass mode of the voltage regulator has not been enabled.

[0045] When BYPASS_ON changes to a high state, the voltage regulator enters a dropout transition 222 characterized by a dropout transition voltage 232 of VOUT. Once the dropout transition voltage 232 (VOUT) reaches the dropout voltage level 23, the voltage regulator is in the dropout mode 24. As shown, the dropout transition voltage 232 is a so-called "soft" dropout transition that smoothly transitions from the regulated voltage level 21 to the dropout 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 time scale shown). In contrast, the soft dropout transition shown by the dropout transition voltage 232 is a controlled, smooth transition from the regulation mode 20 to the dropout mode 24 (i.e., relative to an uncontrolled voltage transition).

[0046] In one embodiment, the shape of the dropout 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 dropout transition 222 after the dropout mode 24 is activated. However, other shapes for the dropout transition voltage 232 may be used. The rate of the voltage transition during the dropout transition 222 (e.g., the slope of the substantially linear voltage curve) may be controlled by a control circuit system (e.g., a dropout transition control circuit system) included in the voltage regulator. For example, the rate of the dropout transition 222 may be selected to limit the inrush current to a desired range, the details of which may be determined by the specific capabilities of components in the voltage regulator, such as pass elements (e.g., power transistors).

[0047] After the voltage regulator is in the dropout 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 dropout voltage level 23 to the bypass voltage level 27 and the voltage regulator is in the bypass mode 26. Similar to the soft dropout transition in the dropout 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 close to the bypass voltage level 27, but other shapes are of course possible.

[0048] The soft bypass transition, shown by the bypass transition voltage 235, is a controlled, gentle transition (i.e., relative to an uncontrolled voltage transition) from the voltage drop mode 24 to the bypass voltage level 27. It should be noted that the uncontrolled voltage transition may resemble a step function on the time scale shown, but may appear to be a substantially exponential voltage curve on a much smaller time scale. That is, the soft transition described herein may have a different shape and a different rate than a hard (i.e., uncontrolled) transition, or may 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) may be controlled by a control circuit system (e.g., bypass transition control circuit system) including resistive and capacitive elements in the voltage regulator to change the RC constant to a desired value. Similar to the rate of the voltage drop transition 222, the rate of the bypass transition 225 may be selected to limit the inrush current to a desired range, which may be specific to the details of a particular voltage regulator implementation.

[0049] Figure 3 An example voltage regulator circuit including a dropout transition control circuit coupled to a feedback voltage divider and a corresponding qualitative graph showing the output voltage of the voltage regulator circuit during a controlled dropout transition are illustrated in accordance with an embodiment of the present invention. Figure 3 The voltage regulator circuit of can be a specific implementation of other voltage regulator circuits, or can be combined with other voltage regulator circuits described herein. Like-labeled elements can be as described above.

[0050] See also Figure 3 , the voltage regulator circuit 300 includes a pass element 14 coupled between an input node 10 and an output node 12. As before, a feedback voltage 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 voltage divider 17, which is used together with a reference voltage Vref to regulate the output voltage VOUT at the output node 12. However, unlike Figure 1In contrast to the voltage regulator circuit 100 of FIG. 1 , the voltage regulator circuit 300 includes a voltage drop transition control circuit 330 coupled between the feedback voltage divider 17 and the comparison circuit 18 .

[0051] The voltage drop transition control circuit 330 is configured to manually transition the voltage regulator circuit 300 from the regulation mode 20 to the voltage drop mode 24 by providing a controllable alternative path to the ground node 11, thereby changing the resistance of the feedback voltage divider 17 in a controlled manner. Specifically, the voltage drop transition control circuit 330 is configured to implement a voltage drop transition 322 (soft voltage drop transition), as shown in the corresponding qualitative diagram 302. To this end, the voltage drop transition control circuit 330 can be regarded as a voltage ramp circuit or include a voltage ramp circuit. For example, the voltage drop 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 a momentary switch).

[0052] It should be noted that for the sake of brevity and clarity, a convention is used here and below where elements following the pattern [x22] (where "x" is the figure number) can be related implementations of pressure drop transitions in various embodiments. For example, unless otherwise specified, pressure drop transition 322 can be similar to pressure drop transition 222. Similar conventions are used for other elements, which can be made clear by using similar terminology in conjunction with the numbering system mentioned above.

[0053] 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 may not be possible in practice, as the complementary differential pair of the voltage regulators may be important for the operation of the voltage regulator circuit 300. Therefore, the dropout transition control circuit 330 has the advantage of enabling manual activation of the dropout mode 24, while still maintaining the desired functionality of the voltage regulator circuit 300.

[0054] Qualitative diagram 302 shows a voltage drop transition 322 activated using the BYPASS_ON signal. For example, this can be to turn on the bypass mode of the voltage regulator circuit 300 during normal operation (i.e., regulation mode 20). However, the details of the voltage drop transition 322 of the voltage regulator circuit 300 do not preclude the case where the voltage drop mode 24 is enabled in order to subsequently enter the bypass mode (e.g., such as the case in qualitative diagram 202). For example, as shown in qualitative diagram 302, the voltage drop transition control circuit 330 is only used to limit the inrush current during the voltage drop transition 322, and the bypass mode is not required at all.

[0055] Figure 4 An example voltage drop transition control circuit including a ramp generator circuit coupled to a ramp control element according to an embodiment of the present invention is illustrated. Figure 4The voltage drop transition circuit may be a specific implementation of other voltage drop transition circuits described herein, such as Figure 3 The voltage drop transition circuit of FIG. 1 is shown in FIG. 1 . Similar labeled components are as described above.

[0056] refer to Figure 4 , the voltage drop transition control circuit 430 includes a feedback voltage divider 17 coupled between the output node 12 and the ground node 11. In addition to the resistors R1 and R2 of the feedback voltage divider 17, the feedback network is also extended to include additional resistors. For example, the ramp control element 42 is coupled between the feedback voltage divider 17 and the ground node 11, surrounded by resistors R3 and R4. A ramp generator circuit 440 is also included, which is configured to generate a ramp voltage at the output terminal OUT coupled to the ramp control element 42. The ramp voltage can correspond to a signal received at the input terminal of the ramp generator circuit 440 (such as a ramp suppression signal (ramp_inh) as shown).

[0057] Another resistor R5 may also be included between resistor R3 and feedback voltage divider 17. A ramp bypass element 44 may be coupled in parallel with resistor R5. Ramp bypass element 44 may be controlled by the same signal (e.g., ramp_inh) as ramp generator circuit 440. However, if the resistance of resistor R1 is high enough, resistor R5 may not be included, and the connection between R3 and feedback voltage divider 17 may be shorted instead.

[0058] The voltage drop transition control circuit 430 is configured to slowly turn on the ramp control element 42 using the OUT generated by the ramp generator circuit 440. As VOUT increases, the output capacitor can be charged by a current (eg, at a maximum rate of dV / dT=I LIM / C OUT , where I LIM is the maximum allowable load current (OCP limit current), and C OUT is the output capacitance of the voltage regulator). The voltage drop transition control circuit 430 can advantageously be easily implemented while still achieving the desired limitation of the inrush current.

[0059] Figure 5 Another example voltage drop transition control circuit is illustrated in accordance with an embodiment of the present invention including a ramp generator circuit coupled to a ramp control element, the ramp generator circuit including a current source. Figure 5 The voltage drop transition circuit may be a specific implementation of other voltage drop transition circuits described herein, such as Figure 3 The voltage drop transition circuit of FIG. 1 is shown in FIG. 1 . Similar labeled components are as described above.

[0060] refer to Figure 5, the voltage drop transition control circuit 530 includes a feedback voltage divider 17 coupled between the output node 12 and the ground node 11. As previously discussed, the feedback voltage divider 17 is expanded to include a feedback network including 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.

[0061] The ramp generator circuit 540 includes an input terminal INH receiving a signal ramp_inh. An inverter 61 may be included to invert the ramp enable signal (ramp_en) to provide a ramp inhibit signal (ramp_inh) at the input terminal INH. The ramp generator circuit 540 also includes a current source 52 and a capacitor 63 coupled in series between the power supply and the ground node 11.

[0062] The first inhibit switch 54 is coupled in parallel with the current source 52, while the second inhibit switch 56 is coupled in parallel with the capacitor 63. Both the first inhibit switch 54 and the second inhibit switch 56 include a control node coupled to INH (and therefore, in this case controlled by the ramp_inh signal).

[0063] Optionally, to allow the ramp generator circuit 540 to use the normal startup mode of the voltage regulator when the bypass mode is enabled before the voltage regulator is enabled, the regulator enable switch 58 can be optionally coupled in parallel with the current source 52 and include a control node coupled to the 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 the D input terminal, the regulator enable signal (EN_REG) at the clock input terminal (CLK), and the bypass mode activation signal bp_act at the enable input terminal (EN). At the same time, the gated flip-flop 50 can output (at the Q output terminal) a bypass first signal bp_before_en_act indicating whether the bypass mode has been enabled before the regulator itself is enabled.

[0064] As shown, when ramp_inh is low and bp_before_en_act is low (e.g., indicating that the 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, the current source 52 charges the capacitor 63, and the capacitor 63 then generates a ramp voltage at OUT. Of course, other arrangements including alternative signaling arrangements are also possible, as may be apparent to those of ordinary skill in the art.

[0065] Figure 6An example voltage regulator circuit including a bypass transition control circuit according to an embodiment of the present invention is illustrated, the 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 a corresponding qualitative graph showing the output voltage of the voltage regulator circuit during a controlled bypass transition. Figure 3 The voltage regulator circuit of may be a specific implementation of other voltage regulator circuits or may be combined with other voltage regulator circuits described herein. Like-labeled elements may be as described above.

[0066] refer to Figure 6 , the voltage regulator circuit 600 includes a pass element 14 coupled between an input node 10 and an output node 12. Similar to the voltage regulator circuits 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 control nodes of the pass element 14 and the bypass element 16 and the input node 10.

[0067] The bypass transition control circuit 60 is configured to manually transition the voltage regulator circuit 600 to the 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 the dropout voltage level 23. For example, before transitioning to the bypass mode 26, the voltage regulator circuit 600 may need to have no open loop gain (as shown in the dropout voltage level 23). The details of how the voltage regulator circuit 600 enters the dropout mode 24 may not be important (as shown by the dashed line of BYPASS_ON before the bypass transition 625).

[0068] In various embodiments, a signal to enable bypass mode (e.g., BYPASS_ON) occurs before bypass transition 625. In one embodiment, bypass transition 625 is triggered by voltage regulator circuit 600 detecting that dropout mode 24 has been reached. Alternatively, another signal may be used to directly trigger bypass transition 625 (e.g., if the voltage regulator is already in dropout mode).

[0069] Bypass transition control circuit 60 may include a bypass switch 62 (e.g., a soft gate connection switch) coupled between input node 10 and control nodes of pass element 14 and bypass element 16. For example, as shown, bypass switch 62 may include a pair of switch elements (shown here as a p-type MOSFET and an n-type MOSFET) coupled in parallel between control nodes of pass element 14 and bypass element 16. Opposite transistor types may be combined with one or more inverters to facilitate bidirectional switching of bypass switch 62.

[0070] The pair of switch 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 a control node (e.g., a gate in an array (cast) of FETs) through a resistor R6. The connection can be a soft connection controlled by the 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 so as to provide the desired characteristics of the bypass transition voltage 635. Another switch element coupled between the control node of the bypass element 16 and VIN can be used to control the connection of the gate to VIN. Another resistor R7 can be optionally included in series.

[0071] The control node connecting the pass element 14 and the bypass element 16 may transition the voltage regulator circuit 600 to the bypass mode 26. For example, before connecting the control node, VOUT may be at the dropout voltage level 23, and after connecting the control node, VOUT transitions to the bypass voltage level 27. The control node connection may begin immediately once the voltage regulator circuit 600 is in the dropout mode 24. Alternatively, the control node connection may be delayed for a predetermined length of time after the voltage regulator circuit 600 enters the dropout mode 24.

[0072] Figure 7 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 is illustrated in accordance with an embodiment of the present invention. Figure 7 The voltage regulator circuit may be other voltage regulator circuits (such as Figure 6 The present invention may be used in conjunction with a specific embodiment of a voltage regulator circuit of the present invention, or in combination with other voltage regulator circuits described herein. Like-labeled elements may be as described above.

[0073] In a conventional voltage regulator circuit that allows manual activation of the bypass mode, protection from overcurrent events may not be provided. That is, during activation and deactivation of the bypass mode, if an overcurrent event occurs, the conventional voltage regulator circuit is not protected. Figure 7 The voltage regulator circuit 700 is similar to the voltage regulator circuit 700 except that it also includes an OCP control circuit 770 (not to be confused with the OCP circuitry of the voltage regulator circuit 700 that may already be present). Figure 6 In contrast to conventional circuits, the bypass transition control circuit 60 of the voltage regulator circuit 700 allows manual activation and deactivation of the bypass mode, while the OCP control circuit 770 is configured to provide OCP functionality throughout the bypass transition process (eg, using existing OCP circuitry).

[0074] The voltage regulator circuit 700 also includes an OCP pass element 74 and an OCP bypass element 75 coupled in parallel. The control node of the OCP pass element 74 is coupled to the control node of the pass element 14, while the 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, and the OCP control circuit 770 extends this functionality to also include transitions to and from the bypass mode.

[0075] The maximum allowed load current is the limiting current (ILIM). When an additional pass element (i.e., bypass element 16) is connected, ILIM increases and an additional replica pass element (OCP bypass element 75) should also be connected. The OCP bypass element 75 is appropriately sized to provide OCP functionality when the bypass element 16 is turned on. However, this only provides OCP functionality during regulation mode and bypass mode, not during the transition between the two.

[0076] 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 that 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 node with little or no lag time. For example, the bidirectional switch can be connected to the OCP activation signal ocp_act. When ocp_act is "1", the bidirectional switch can be turned on. Similarly, the OCP control circuit 770 can include a switch coupled between the input node 10 and the control node. When ocp_act is "1", this switch can also be turned on.

[0077] The OCP control circuit 770 is configured to provide protection when an overcurrent event (ocp_act) occurs during the period when the control nodes of the pass element 14 and the bypass element 16 are connected to activate the bypass mode (gate_con_act). An AND gate 78 and appropriate inverters are included to open the switch between the input node 10 and the control node when ocp_act is "1" and gate_con_act = 1". This happens immediately once the conditions are met.

[0078] However, the bidirectional switch connecting the control node itself is configured to turn on after the transition to the bypass mode is completed. Specifically, a rising edge delay 76 is included, which delays the rising edge of gate_con_act, thereby generating a delayed signal 77 (e.g., a delay triggered by the activation of the bypass mode). The delayed signal 77 and ocp_act are inputs to an XOR gate 79, which has an output coupled to an AND gate 78 coupled to gate_con_act.

[0079] It may be advantageous to introduce a low resistance between control nodes (e.g., gates). For example, OCP control circuit 770 controls the control node of pass element 14 (e.g., a power MOSFET of voltage regulator circuit 700). It may be important that the control node of OCP pass element 74 (e.g., an additional power MOSFET) does not "lag" due to high resistance. Therefore, a "hard" connection (e.g., a hard gate connection) is used. That is, hard switching occurs after receiving an overcurrent event signal. immediately is activated.

[0080] However, if the overcurrent event occurs during a soft connection of the control node (e.g., gate), it may be better to introduce a low resistance when the soft connection of the gate ends. Therefore, a "hard" connection (e.g., hard gate connection) can be made based on a timer (e.g., using a rising edge delay 76). In other words, the hard switch is also activated after a specified delay time that is at least as long as the soft connection of the gates of the pass and bypass elements. In this case, the OCP switch 72 can be considered a delayed hard gate connection switch. In the opposite case, if the overcurrent event occurs during a soft disconnection of the control node (e.g., gate), the control node of the OCP bypass element 75 should be coupled to VIN immediately.

[0081] Figure 8 Another example voltage regulator circuit including a voltage drop transition control circuit, a bypass transition control circuit and an overcurrent protection control circuit according to an embodiment of the present invention is illustrated. Figure 8 The voltage regulator circuit may be other voltage regulator circuits (such as Figure 7 The present invention may be used in conjunction with a specific embodiment of a voltage regulator circuit of the present invention, or in combination with other voltage regulator circuits described herein. Like-labeled elements may be as described above.

[0082] refer to Figure 8 , except that the additional components constituting the OCP control circuit 870 are included to illustrate 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 is similar to Figure 7The voltage regulator circuit 700 of FIG. includes asynchronous logic 88 to facilitate soft connection of the control node (using bypass transition control circuit 60) when the voltage drop detector 82 detects the voltage drop mode. That is, the voltage drop detector 82 is configured to detect that the voltage regulator circuit 800 is in the voltage drop mode and generate a corresponding signal.

[0083] Buck mode is manually activated using the BP_ON and EN_REG signals as inputs to an AND gate that outputs to both falling edge delay 86 (which generates ramp_enh as output) and asynchronous logic 88. The ramp_enh signal is inverted to generate the ramp_inh signal and provided to ramp generator circuit 540.

[0084] After an overcurrent event, the resistance of the feedback network can be set back to a normal value. After the bypass mode has been activated (e.g., by connecting the gates of the pass elements together), the bypass mode can also be manually turned off by setting the signal BP_EN = "0". In this case, the sequence is reversed compared to the activation sequence: first, the gates of the pass element and the bypass element are disconnected again in a soft manner, and then after a defined time delay (falling edge delay 86) covering the time required for the gate soft disconnection, the resistance of the feedback network can be set back to a normal value. This can be performed in a "hard" switching manner (i.e., without taking into account potential surge currents). The voltage regulator circuit 800 will then return to normal regulation mode and (assuming that the voltage regulator is not a push-pull type) VOUT can be discharged through the load resistor (e.g., over a period of time).

[0085] The voltage regulator circuit 800 illustrates one example of how several control circuits (e.g., the voltage drop transition control circuit 830, the bypass transition control circuit 60, and the OCP control circuit 870) may be implemented in a single voltage regulator circuit. However, it will be apparent to one skilled in the art that various aspects of the control circuit may be modified to suit a particular application. For example, while generally advantageous, the OCP functionality may be omitted while still retaining both the voltage drop transition control and the bypass transition control (e.g., still generating a voltage drop control circuit such as Figure 2 and VOUT transition voltage curves shown in other figures, but without OCP function).

[0086] Fig. 9 An example qualitative diagram illustrating 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 invention is illustrated. For example, Fig. 9 A qualitative diagram of various voltage regulators (ie, voltage regulation circuits) described herein (such as Figure 8 A qualitative representation of the behavior of a voltage regulator circuit). Like labeled components may be as previously described.

[0087] refer to Fig. 9 , qualitative graph 902 shows the input voltage VIN and output voltage VOUT of the voltage regulator after the bypass mode is 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 circuit system (e.g., the voltage drop transition control circuit system including the ramp generator circuit) facilitates the controlled transition of VOUT from the regulated output voltage to the voltage drop voltage level (voltage drop mode). The output current IOUT is shown to illustrate the surge current 90 during the transition. Here, the surge current 90 rises, but is limited during the transition.

[0088] After the voltage regulator is in the dropout mode, the control circuitry (e.g., a bypass transition control circuit including a soft gate connection switch) causes VOUT to transition from the dropout voltage level to the bypass voltage level (e.g., close to VIN) in a controlled manner and the voltage regulator is in the bypass mode. Again, the inrush current 90 rises briefly but is limited during the transition.

[0089] The bypass mode can also be manually turned off to return the voltage regulator to normal regulation mode operation. Fig.10 An example qualitative diagram illustrating various voltages and output currents of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode according to an embodiment of the present invention is illustrated. For example, Fig.10 A qualitative diagram of various voltage regulators (ie, voltage regulation circuits) described herein (such as Figure 8 A qualitative representation of the behavior of a voltage regulator circuit). Like labeled components may be as previously described.

[0090] refer to Fig.10 , qualitative graph 1002 shows that VOUT is at the bypass voltage level while the BP_ON signal is high, indicating that the voltage regulator is in bypass mode. Once BP_ON goes low, the control circuit system (e.g., a bypass transition control circuit including a soft gate connection switch) facilitates a controlled transition to the dropout voltage level (e.g., by performing a soft disconnection of the gates of the pass transistor and the bypass transistor). As shown, this transition has little effect on the surge current 90.

[0091] Once in the voltage drop mode, the control circuit system (e.g., a voltage drop transition control circuit including a 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 the regulation mode. Again, the inrush current 90 is limited by the controlled transition.

[0092] It is also possible to set the bypass mode before enabling the voltage regulator. Fig.11 Another example qualitative diagram illustrating various voltages and output currents of a voltage regulator during a controlled transition of the voltage regulator from a bypass mode to a regulation mode when the bypass mode is enabled before the voltage regulator is enabled according to an embodiment of the present invention is illustrated. For example, Fig.11 A qualitative diagram of various voltage regulators (ie, voltage regulation circuits) described herein (such as Figure 8 A qualitative representation of the behavior of a voltage regulator circuit). Like labeled components may be as previously described.

[0093] refer to Fig.11 , qualitative graph 1102 shows that BP_ON is initially high and EN_REG is low, indicating that the bypass mode of the voltage regulator is enabled, but the voltage regulator itself is not enabled. Therefore, the voltage regulator receives an 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 voltage drop transition control circuit coupled to a feedback voltage divider) so that the soft start is provided by the soft start implementation of the voltage regulator itself. The soft start ramp can be adjusted to have the desired characteristics.

[0094] As shown, once the voltage regulator is enabled, VOUT ramps up from zero to the dropout voltage level in a controlled transition manner and then performs a controlled transition to bypass mode. As before, the inrush current 90 has two peaks, corresponding to the transition to dropout mode and the transition to bypass mode, but the inrush current 90 is limited by the controlled transition. Compared to the transition from regulation mode to dropout mode shown in qualitative graph 902, the transition from zero to dropout mode here widens the peak of the inrush current 90, but the behavior of the output current IOUT is similar in other respects.

[0095] Fig.12 An example method of activating a bypass mode of a voltage regulator according to an embodiment of the present invention is illustrated. Fig.12 The method can be combined with other methods and performed using the systems and devices described herein. For example, Fig.12 The method can be used with Figure 1-Figure 11 Although shown in a logical order, Fig.12 The arrangement and numbering of the steps are not intended to be limiting. Fig.12 The method steps may be performed in any suitable order, or concurrently with each other, as will be apparent to those skilled in the art.

[0096] refer to Fig.12, a 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, the voltage drop mode of the voltage regulator is activated by controlling a voltage drop transition from the regulated output voltage to a voltage drop voltage level using a voltage drop transition control circuit coupled to a feedback voltage divider to limit inrush current, wherein the feedback voltage divider is coupled between the output node and a ground node. In step 1203, the 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.

[0097] Example embodiments of the invention are summarized herein. Other embodiments may be understood from the entire specification and claims filed herein.

[0098] Example 1. A voltage regulator circuit comprising: an input node configured to receive an input voltage; an output node configured to generate 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 divider coupled between the output node and a ground node, the feedback divider configured to generate 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 divider, the error amplifier circuit configured to minimize a voltage difference between a reference voltage and the feedback signal; and a dropout transition control circuit coupled to the feedback divider and configured to activate a dropout mode of the voltage regulator circuit to limit inrush current by controlling a dropout transition at the output node from the regulated output voltage to a dropout voltage level.

[0099] Example 2. The voltage regulator circuit of Example 1, wherein the voltage drop transition control circuit is further configured to activate the voltage drop mode to limit the inrush current by making the voltage drop transition a substantially linear voltage curve.

[0100] Example 3. A voltage regulator circuit as in one of Examples 1 and 2, further comprising: a bypass transition control circuit, comprising a bypass switch coupled between a control node of a pass element and a control node of a bypass element, the bypass switch being configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition from a dropout voltage level to a bypass voltage level at an output node to further limit surge current.

[0101] 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 causing the bypass transition to be a substantially exponential voltage curve approaching the bypass voltage level.

[0102] Example 5. A voltage regulator circuit as in Example 4, wherein the bypass transition control circuit further comprises a resistor coupled between a control node of the pass element and a 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.

[0103] 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.

[0104] Example 7. The voltage regulator circuit of any 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 a voltage drop mode.

[0105] Example 8. A voltage regulator circuit as in one of Examples 3 to 7, further comprising an overcurrent protection (OCP) control circuit, the OCP control circuit comprising an OCP switch coupled between a control node of the pass element and a control node of the bypass element, the OCP switch being configured to provide a low resistance connection between the control nodes immediately during an overcurrent event or after a delay triggered by activation of a bypass mode.

[0106] Example 9. A method for 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 the voltage drop mode of the voltage regulator circuit to limit surge current by controlling a voltage drop transition from the regulated output voltage to a voltage drop voltage level using a voltage drop 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 the 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.

[0107] Example 10. The method of Example 9, wherein activating the voltage drop mode includes transitioning the voltage drop to a substantially linear voltage curve to limit inrush current.

[0108] Example 11. A method as in one of Examples 9 and 10, wherein activating the bypass mode includes connecting a control node of the pass element and a control node of the bypass element, while controlling a bypass transition from a dropout voltage level to a bypass voltage level using a bypass transition control circuit coupled between the control nodes to limit surge current.

[0109] Example 12. The method of Example 11 further includes: deactivating the bypass mode by disconnecting the control node of the pass element and the control node of the bypass element, and using the bypass transition control circuit to control the bypass transition from the bypass voltage level to the voltage drop voltage level to further limit the surge current; and activating the regulation mode of the voltage regulator by using the voltage drop transition control circuit to control the voltage drop transition from the voltage drop voltage level to the regulated output voltage to further limit the surge current.

[0110] Example 13. The method of one of Examples 11 and 12, wherein activating the bypass mode further comprises transitioning the voltage drop into a substantially exponential voltage curve close to the bypass voltage level to further limit the inrush current.

[0111] Example 14. The method of Example 13, wherein the substantially exponential voltage curve is controlled according to a predetermined RC constant.

[0112] Example 15. The method of one of Examples 9 to 14, further comprising: providing a low resistance connection between a control node of the pass element and a control node of the bypass element during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0113] Example 16. A method as in one of Examples 9 to 15, further comprising: providing a bypass mode activation signal before activating the voltage drop mode, the bypass mode activation signal initiating activation of the voltage drop 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 voltage drop mode.

[0114] Example 17. The method of Example 16, further comprising: enabling a bypass mode of the voltage regulator before enabling a regulation mode of the voltage regulator.

[0115] Example 18. The method of one of Examples 9 to 17, further comprising: providing a low resistance connection between a control node of the pass element and a control node of the bypass element during an overcurrent event or immediately after a delay triggered by activation of the bypass mode.

[0116] Example 19. A voltage regulator circuit comprising: an input node configured to receive an input voltage; an output node configured to generate 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 the control node of the pass element, and a control node of the OCP bypass element coupled to the 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.

[0117] Example 20. The voltage regulator circuit of Example 19 further includes: a feedback divider coupled between the output node and the ground node, the feedback divider being configured to generate a feedback signal indicative of a regulated output voltage; an error amplifier circuit coupled between a control node of the pass element and the feedback divider, the error amplifier circuit being configured to compare a reference voltage with the feedback signal; and a dropout transition control circuit coupled to the feedback divider and 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 further limit inrush current.

[0118] Example 21. The voltage regulator circuit of Example 20, wherein the voltage drop transition control circuit is further configured to activate the voltage drop mode by making the voltage drop transition a substantially linear voltage curve to further limit the inrush current.

[0119] 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 close to the bypass voltage level.

[0120] Example 23. The voltage regulator circuit of Example 22, wherein the bypass transition is from a dropout voltage level to a bypass voltage level.

[0121] Example 24. The voltage regulator circuit of any 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 a dropout mode.

[0122] Although the present invention has been described with reference to illustrative embodiments, this description is not intended to be interpreted in a limiting sense. Various modifications and combinations of the illustrative embodiments and other embodiments of the present invention will be apparent to those skilled in the art upon reference to this description. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A voltage regulator circuit, comprising: an input node configured to receive an input voltage; an output node configured to generate a regulated output voltage; a path 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 generate a feedback signal indicative of a 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 being configured to minimize a voltage difference between a reference voltage and a feedback signal; as well as A dropout transition control circuit is coupled to the feedback voltage divider and is configured to activate a dropout mode of the voltage regulator circuit to limit inrush current by controlling a dropout transition at the output node from a regulated output voltage to a dropout voltage level.

2. The voltage regulator circuit of claim 1, wherein the voltage drop transition control circuit is further configured to activate the voltage drop mode to limit the inrush current by making the voltage drop transition a substantially linear voltage curve.

3. The voltage regulator circuit of claim 1 , further comprising: A bypass transition control circuit includes a bypass switch coupled between a control node of a pass element and a control node of a bypass element, the bypass switch being configured to activate a bypass mode of the voltage regulator circuit by controlling a bypass transition at an output node from a dropout voltage level to a bypass voltage level to further limit inrush current.

4. The voltage regulator circuit of claim 3, wherein the bypass switch is further configured to activate the bypass mode to further limit the inrush current by causing the bypass transition to be a substantially exponential voltage curve approaching the bypass voltage level.

5. The voltage regulator circuit as claimed in claim 4, The bypass transition control circuit further includes a resistor coupled between a control node of the pass element and a control node of the bypass element, and Therein the substantially exponential voltage curve is controlled according to an RC constant determined by a resistor and a capacitance between the control node and the input node. 6 . The voltage regulator circuit of claim 3 , wherein the bypass transition control circuit is configured to trigger the bypass switch in response to detecting that the voltage regulator circuit is in a dropout mode.

7. The voltage regulator circuit of claim 3, further comprising an over-current protection (OCP) control circuit, the OCP control circuit comprising an OCP switch coupled between a control node of the pass element and a control node of the bypass element, the OCP switch configured to provide a low resistance connection between the control nodes immediately during an over-current event or after a delay triggered by activation of the bypass mode.

8. 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 dropout mode of the voltage regulator circuit to limit inrush current by controlling a dropout transition from a regulated output voltage to a dropout voltage level using a dropout transition control circuit coupled to a feedback voltage divider, wherein the feedback voltage divider is coupled between an output node and a ground node; as well as The bypass mode of the voltage regulator is activated 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.

9. The method of claim 8, wherein activating the voltage drop mode includes transitioning the voltage drop into a substantially linear voltage curve to limit inrush current.

10. The method of claim 8, 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 a dropout voltage level to a bypass voltage level to limit inrush current using a bypass transition control circuit coupled between the control nodes.

11. The method of claim 10, further comprising: deactivating the bypass mode by disconnecting a control node of the pass element and a control node of the bypass element while controlling a bypass transition from a bypass voltage level to a dropout voltage level using a bypass transition control circuit to further limit the inrush current; and The regulation mode of the voltage regulator is activated to further limit the inrush current by controlling the dropout transition from the dropout voltage level to the regulated output voltage using a dropout transition control circuit.

12. The method of claim 8, further comprising: A low resistance connection is provided between the control node of the pass element and the control node of the bypass element immediately during an overcurrent event or after a delay triggered by activation of the bypass mode.

13. The method of claim 8, further comprising: providing a bypass mode activation signal before activating the voltage drop mode, the bypass mode activation signal initiating activation of the voltage drop mode; as well as Activating the bypass mode is initiated in response to the bypass mode activation signal and detecting that the voltage regulator is in the dropout mode.

14. The method of claim 8, further comprising: A low resistance connection is provided between the control node of the pass element and the control node of the bypass element immediately during an overcurrent event or after a delay triggered by activation of the bypass mode.

15. A voltage regulator circuit comprising: an input node configured to receive an input voltage; an output node configured to generate a regulated output voltage; A pass element and a bypass element are 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 including a soft gate connection switch coupled between a control node of the pass element and a 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; as well as An OCP control circuit includes a delayed hard gate connection switch coupled between a control node of a pass element and a control node of a bypass element, the delayed hard gate connection switch being configured to provide a low resistance connection between the control nodes immediately during an overcurrent event or after a delay triggered by activation of a bypass mode.

16. The voltage regulator circuit of claim 15, further comprising: a feedback voltage divider coupled between the output node and a ground node, the feedback voltage divider configured to generate a feedback signal indicative of a 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 being configured to compare a reference voltage with a feedback signal; as well as A dropout transition control circuit is coupled to the feedback voltage divider and is configured to activate a dropout mode of the voltage regulator circuit by controlling a dropout transition at the output node from a regulated output voltage to a dropout voltage level to further limit the inrush current. 17 . The voltage regulator circuit of claim 16 , wherein the voltage drop transition control circuit is further configured to activate the voltage drop mode by making the voltage drop transition a substantially linear voltage curve to further limit the inrush current.

18. The voltage regulator circuit of claim 15, wherein the soft gate connect 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 approaching a bypass voltage level.

19. The voltage regulator circuit of claim 18, wherein the bypass transition is from a dropout voltage level to a bypass voltage level.

20. The voltage regulator circuit of claim 15, 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 a dropout mode.

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