CN113765353A

CN113765353A - Control circuit for facilitating inrush current reduction for a voltage regulator and voltage regulating device with inrush current reduction

Info

Publication number: CN113765353A
Application number: CN202010488948.1A
Authority: CN
Inventors: 张耀仁
Original assignee: Elite Semiconductor Memory Technology Inc
Current assignee: Elite Semiconductor Memory Technology Inc
Priority date: 2020-06-02
Filing date: 2020-06-02
Publication date: 2021-12-07
Anticipated expiration: 2040-06-02
Also published as: CN113765353B

Abstract

A control circuit for facilitating inrush current reduction for a voltage regulator that variably provides an output voltage in response to an input voltage selection. The control circuit comprises a soft start circuit, a soft start tracking circuit and a controller. The soft start circuit is used for providing a soft start signal. The soft start tracking circuit includes a first input terminal for receiving a feedback signal from the voltage regulator, a second input terminal coupled to the soft start circuit, and an output terminal coupled to the soft start circuit. The controller is coupled to the soft start tracking circuit and is configured to selectively output an enable signal to the soft start tracking circuit according to the selection of the output voltage. The soft-start tracking circuit is operable in response to the enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator.

Description

Control circuit for facilitating inrush current reduction for a voltage regulator and voltage regulating device with inrush current reduction

Technical Field

The present invention relates to a voltage regulator, and more particularly, to a control circuit for facilitating inrush current reduction of a voltage regulator and a voltage regulating apparatus having the same.

Background

In the power supply circuit, a non-isolated switching regulator having an inductor is used because of high efficiency. Therefore, it is suitable for many applications such as portable equipment or large electronic devices.

However, in order to design a switching regulator having a desired performance, many technical considerations need to be addressed. One such consideration is how to activate the switching regulator. Without a proper start-up method, the output voltage will have a large overshoot and the inrush current used to charge the output capacitor will be very large. Such conditions can damage the IC or external components. A common countermeasure to address this problem is by adding a soft start circuit during initial start-up. The soft start circuit can generate a slowly rising voltage to slowly increase the output voltage to a desired value. The slowly rising voltage may be connected to the input of the PWM comparator or the reference voltage for the error amplifier. This avoids large overshoots and limits inrush currents.

In some implementations, some switching regulators have a variable output voltage. Some of the problems associated with such switching regulators are that overshoot and large inrush currents may occur when the output voltage changes from a low voltage to a high voltage. The existing soft start circuit can not be operated after the switching regulator is started. Therefore, the conventional soft start circuit cannot provide protection when the output voltage changes after the initial start.

Disclosure of Invention

It is an object of the invention to propose a control circuit for facilitating inrush current reduction for a voltage regulator.

To achieve the above object, the present invention proposes a control circuit for facilitating inrush current reduction for a voltage regulator for variably providing an output voltage in response to an output voltage selection. The control circuit comprises a soft start circuit, a soft start tracking circuit and a controller. The soft start circuit is used for providing a soft start signal. The soft start tracking circuit includes a first input terminal for receiving a feedback signal from the voltage regulator, a second input terminal coupled to the soft start circuit, and an output terminal coupled to the soft start circuit. The controller is coupled to the soft start tracking circuit and is configured to selectively output an enable signal to the soft start tracking circuit according to the selection of the output voltage. The soft-start tracking circuit is operable in response to an enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator.

Optionally, the controller is configured to output the enable signal to operate the soft-start tracking circuit when the output voltage selection satisfies a determination criterion for generating the enable signal.

Optionally, the controller determines that the output voltage selection meets the criterion when the output voltage selection represents a selection from a present output voltage to a target output voltage higher than the present output voltage.

Optionally, the controller is further configured to output an output selection signal in response to the output voltage selection for informing the voltage regulator of the output voltage selection.

Optionally, when the controller outputs the output selection signal, the controller outputs an enable signal that is active for a period of time to cause the soft start tracking circuit to operate.

It is another object of the present invention to provide a voltage regulation device with inrush current reduction.

In order to achieve the above object, the present invention provides a voltage regulating apparatus including a voltage regulator and a control circuit. The voltage regulator is used for responding to the output voltage selection to variably provide the output voltage, and comprises a soft start terminal, an output voltage terminal and a feedback terminal. The control circuit is coupled to the voltage regulator and comprises a soft start circuit, a soft start tracking circuit and a controller. The soft start circuit is coupled to the soft start terminal and is used for providing a soft start signal to the voltage regulator. The soft start tracking circuit comprises a first input terminal for receiving a feedback signal output from a feedback terminal of the voltage regulator, a second input terminal coupled to the soft start circuit, and an output terminal coupled to the soft start circuit. The controller is coupled to the soft start tracking circuit and is configured to selectively output an enable signal to the soft start tracking circuit according to the selection of the output voltage. The soft-start tracking circuit is operable in response to an enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator.

Alternatively, the voltage regulator may be implemented by using a linear voltage regulator or a switching voltage regulator.

Optionally, the voltage regulator comprises: an error amplifier, an output circuit stage and a switchable voltage divider. The error amplifier is coupled to the feedback terminal, the soft start terminal and the reference voltage terminal. The output circuit stage is coupled between the output terminal of the error amplifier and the output voltage terminal. The switchable voltage divider is coupled between the output voltage terminal and the feedback terminal, and is used for providing a feedback signal in response to the output voltage selection so as to enable the output voltage to change.

Optionally, the controller is further configured to output an output selection signal in response to the output voltage selection for informing the voltage regulator of the transmission voltage selection.

Optionally, the voltage regulating device is a single chip.

To achieve the above object, the present invention further provides a control circuit for facilitating inrush current reduction for a voltage regulator for variably providing an output voltage in response to an output voltage selection. The control circuit comprises a soft start tracking circuit and a controller. The soft-start tracking circuit includes a first input terminal for receiving a feedback signal from the voltage regulator, a second input terminal, and an output terminal, wherein the second input terminal and the output terminal are coupled to the soft-start circuit for providing a soft-start signal. The controller is coupled to the soft start tracking circuit and is configured to selectively output an enable signal to the soft start tracking circuit according to the selection of the output voltage. The soft-start tracking circuit is operable in response to an enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator.

Optionally, the control circuit comprises a detection circuit configured to output the enable signal to operate the soft start tracking circuit when the output voltage selection satisfies a criterion of generating the enable signal.

Optionally, the detection circuit determines that the output voltage selection meets the criterion when the output voltage selection represents a selection from a present output voltage to a target output voltage higher than the present output voltage.

Optionally, the detection circuit outputs an enable signal that is active for a period of time to cause the soft start tracking circuit to operate.

Accordingly, various embodiments of a control circuit for facilitating inrush current reduction for a voltage regulator and a voltage regulating apparatus having inrush current reduction are provided, wherein the control circuit has a soft-start tracking circuit operable in response to an enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator. In this way, whenever a level transition of the output voltage of the voltage regulator will cause an inrush current to be generated along with the output voltage, the control circuit outputs the enable signal to provide a soft start signal following the feedback signal to the voltage regulator to restart the soft start function of the voltage regulator during the level transition, thereby effectively and proactively reducing the inrush current.

For a better understanding of the nature and technical content of the present invention, reference should be made to the following detailed description of the invention and the accompanying drawings, which are provided for illustration purposes only and are not intended to limit the scope of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.

FIG. 1 is a schematic diagram illustrating a voltage regulating device using a control circuit that facilitates surge current reduction in accordance with various embodiments of the present invention;

FIG. 2 is a schematic diagram of an embodiment of a voltage regulator of the voltage regulating device of FIG. 1;

FIG. 3 is a schematic diagram of an embodiment of a switchable voltage divider of the voltage regulator of FIG. 2;

FIG. 4 is a schematic diagram of an embodiment of a control circuit for the voltage regulator of FIG. 1;

FIG. 5A is a schematic diagram of an embodiment of a controller of the control circuit of FIG. 4;

FIG. 5B is a schematic diagram of another embodiment of a controller of the control circuit of FIG. 4;

FIG. 6 is a diagram showing the variation of the soft start signal, the feedback signal and the enable signal;

FIG. 7 is a schematic diagram illustrating another embodiment of a control circuit for facilitating inrush current reduction for a voltage regulator.

Description of reference numerals:

1 Voltage regulating device

10 voltage regulator

20 control circuit

30 control circuit

110 error amplifier

120 output circuit stage

121 output circuit control circuit

122 switching circuit

123 induction circuit

124 capacitance circuit

130 switchable voltage divider

210 soft start circuit

211 capacitor circuit

220 soft start tracking circuit

221 operational amplifier

230 controller

231 decoder

232 detection circuit

300 programmable circuit

310 controller

311 detection circuit

Curve 600

601 curve

Curve 602

Curve 603

10A voltage regulator

230A controller

I_REFCurrent source

N_STSoft start terminal

N_IN1First input terminal

N_IN2Second input terminal

N_OUTOutput terminal

N_OVOutput voltage terminal

N_REFReference voltage terminal

N_SCSoft start control terminal

N_FBFeedback terminal

R1 resistor

R2 resistor

R3 resistor

R4 resistor

S0 digital signal

S1 digital signal

S_BPControl signal

S_COMPComparisonSignal

S_ENEnable signal

S_FBFeedback signal

S_OCOutputting a selection signal

S_OSOutputting a selection signal

S_SRSelection request signal

S_STSoft start signal

S_V1Control signal

S_V2Control signal

S_V3Control signal

SW1 switch

SW2 switch

SW3 switch

V_INInput voltage

V_OUTOutput voltage

V_REFReference voltage

V_STSoft start signal

Detailed Description

For the purpose of promoting an understanding of the objects, features and effects of the invention, embodiments and drawings are provided for a detailed description of the present disclosure.

Referring to fig. 4, a voltage regulating device 1 with inrush current reduction according to an embodiment of the present invention is shown in schematic form. As shown in fig. 1, the voltage regulating apparatus 1 includes a voltage regulator 10 and a control circuit 20. A control circuit 20 is coupled to the voltage regulator 10, the control circuit 20 being used to facilitate inrush current reduction for the voltage regulator 10.

Voltage regulator 10 provides a variable output voltage V in response to an output voltage selection_OUTAnd includes a soft start terminal N_STAn output voltage terminal N_OVAnd a feedback terminal N_FB. For example, the voltage regulator 10 is coupled to an input voltage V_INAnd ground and outputs a regulated voltage signal, i.e., an output voltage V_OUTMay be selected according to the output voltage, for example by a voltage divider, to change to one of different predetermined voltage levels. During the transition of the output voltage level, surge current may occur at the output voltage terminal N_OVE.g., from a current voltage level to a target voltage level higher than the current voltage level.

The control circuit 20 is used to reduce the inrush current of the voltage regulator 10, and includes a soft-start circuit 210, a soft-start tracking circuit 220, and a controller 230. The soft start circuit 210 has a soft start control terminal N_SCFor controlling terminal N in soft start_SCProviding a soft start signal S_ST. The soft start tracking circuit 220 includes a first input terminal N_IN1For receiving a feedback signal S from the voltage regulator 10_FBA second input terminal N_IN2For coupling to a soft start circuit 210, such as a soft start control terminal N_SCAnd an output terminal N_OUTFor coupling to the soft start circuit 20. The controller 230 is coupled to the soft-start tracking circuit 220 and is configured to selectively output an enable signal S according to the selection of the output voltage_ENTo the soft start tracking circuit 220.

In this manner, soft-start tracking circuit 220 is responsive to enable signal S_ENBut is operable such that the soft start signal S provided by the soft start circuit 210_STSubstantially following a feedback signal S from the voltage regulator 10_FB。

Thus, each time the output voltage V of the voltage regulator 10 is exceeded_OUTMay cause inrush currents and overshoot, the control circuit 20 may facilitate inrush current reduction for the voltage regulator 10. For example, in the event that the soft-start function cannot be performed after the voltage regulator 10 is started, the output voltage V that may accompany it is reduced whenever necessary_OUTUpon occurrence of an inrush current and an overshoot, the control circuit 20 may be configured to restart the soft start function of the voltage regulator 10. The control circuit 20 can follow the feedback signal S_FBSoft start signal S output to voltage regulator_STThis is achieved whenever the control circuit 20 receives the voltage regulator 10When selected, the voltage regulator 10 indicates that it is to be at its output voltage V_OUTA voltage level transition of the inrush current occurs, effectively and proactively reducing the inrush current.

In the above embodiments, the output voltage selection can be performed by a selection request signal S_SRThe representation is generated, for example, by a processing unit (not shown) of an operating system employing the voltage regulating device 1, output from another component or internally initiated.

In an embodiment, the controller 230 is optionally configured to respond to a selection request signal S_SRAnd outputs an output selection signal S_OSFor informing the voltage regulator 10 of the output voltage selection. In another embodiment, the selection signal S is output_OSMay be realized by a processing unit (not shown) of an operating system in which the voltage regulating device 1 is employed. In one embodiment, the voltage regulator 10 may be implemented to receive the selection request signal S_SRThen internally generating an output selection signal S_OS. Of course, the implementation of the present invention is not limited to the above examples.

In some embodiments, the output regulator 10 may be implemented using a linear voltage regulator or a switching voltage regulator. May provide a variable output voltage V in response to an output voltage selection_OUTIs considered to be the voltage regulator 10 of fig. 1. The voltage regulator 10 may be implemented to include a linear or switching voltage regulator and a switchable voltage divider for selecting one of a predetermined plurality of output levels.

For ease of understanding, referring to fig. 2, an embodiment of the voltage regulator 10 of the voltage regulating device 1 of fig. 1 is shown in schematic form. The voltage regulator 10 includes an error amplifier 110, an output circuit stage 120, and a switchable voltage divider 130.

The error amplifier 110 includes a first input terminal coupled to the feedback terminal N_FBA second input terminal coupled to receive a reference voltage V_REFA reference voltage terminal N_REFA third input terminal coupled to the soft start terminal N_STTo do so byAnd an output terminal coupled to a comparison signal S_COMP. For example, the error amplifier 110 has a soft start function that can be performed by applying a soft start signal V_STApplied to a soft start terminal N_STBut is activated to reduce the inrush current. Of course, the implementation of the invention is not limited to the above examples.

The output circuit stage 120 is coupled to an output terminal of the error amplifier 110 and the output voltage terminal N_OVIn the meantime. For example, the output circuit stage 120 is coupled to the input voltage V_INAnd ground, the output circuit stage 120 includes an output circuit control circuit 121, a switch circuit 122, and a sensing circuit 123. The output circuit control circuit 121 may be for responding to the comparison signal S of the error amplifier 110_COMPAnd any other suitable control circuit that modulates the control signal for the switching circuit 122, such as a Pulse Width Modulation (PWM) control circuit or a Pulse Frequency Modulation (PFM) control circuit. The switch circuit 122 may be coupled to the input voltage V_INAnd between ground, such as a pull-up transistor or a pull-down transistor, to be controlled by control signals from output circuit control circuitry 121. An inductive circuit 123, such as an inductor, is connected between the output of the switching circuit 122 and the output voltage terminal N_OVIn the meantime. Output voltage terminal N as appropriate_OVMay be further coupled to other circuit components such as capacitive circuit 124 or otherwise. Of course, the implementation of the present invention is not limited to the above examples.

A switchable voltage divider 130 is coupled at an output voltage terminal N_OVAnd a feedback terminal N_FBIn between, the switchable voltage divider 130 is adapted to respond to an output selection signal S indicative of an output voltage selection_OSTo provide the feedback signal S_FBSo that the output voltage V is_OUTThe voltage level of (2) is changed.

Referring to fig. 3, an embodiment of the switchable voltage divider 130 of the voltage regulator 10 of fig. 2 is shown in schematic form. As shown in FIG. 3, the switchable voltage divider 130 includes a plurality of resistors, such as resistors R1, R2, R3, R4, toAnd a plurality of switches, such as switches SW1, SW2, SW3 (e.g., switches implemented by transistors, such as NMOS, PMOS, or any suitable transistors). For example, each of the switches SW1-SW3 is connected to the feedback terminal N_FBAnd one end of a corresponding one of the resistors. The switches SW1-SW3 may be composed of S_V1、S_V2、S_V3The control signals indicated control. Referring to fig. 1 to 3, the output selection signal S from the control circuit 20_OSIndicating an output voltage selection which controls the signal S_V1-S_V3Is implemented to turn on one of the switches SW1-SW3 so that the output voltage V is_OUTThe voltage level of (2) is changed.

The feedback signal S provided by the switchable voltage divider 130 is used to select the output voltage_FBAnd an output voltage V_OUTWill vary. For example, when the switch SW1 is turned on and the switches SW2-SW3 are turned off, the output voltage V is_OUTWill be at a first voltage level; when the switch SW2 (or SW3) is turned on and the remaining switches are turned off, the output voltage V is_OUTWill be at a second voltage level (or third voltage level), where the third voltage level is greater than the second voltage level and the first voltage level is less than the second voltage level. It is noted that the output voltage V is during the transition from a current voltage level to a target voltage level_OUTMay be unstable because surge current and overshoot may occur due to characteristics of components such as the sensing circuit 123 in the output circuit stage 120, and the feedback signal S_FBWill change due to the switches SW1-SW3 being switched on or off. In the case illustrated in FIG. 3, feedback signal S is provided when a current output voltage selection indicates a voltage level transition from a lower voltage level (such as a first voltage level) to a higher voltage level (such as a second or third voltage level) than a previous output voltage selection_FBWill drop as shown by a curve 602 shown in fig. 6. If it is assumed that the voltage regulator 10 is configured to operate without the aid of the control circuit 20, the soft-start signal S is shown by a curve 601 shown in fig. 6_STWill remain unchanged after start-up of the voltage regulator 10. Phase (C)Referring to fig. 1-4, as mentioned above, the control circuit 20 is utilized to enable the signal S during the voltage level shifting period_ENWhen generated or announced (asserted), a soft start signal S_STWill vary (as illustrated by a curve 603 shown in fig. 6) and follow the feedback signal S_FB. Specifically, the feedback signal S is_FBIn the above exemplary case with a drop during the voltage level transition, the soft start signal S_STCan be controlled by a soft start tracking circuit 220, which is enabled by a controller 230 so as to substantially follow the feedback signal S_FBCausing the soft-start function of the voltage regulator 10 to be restarted, such as provided by the error amplifier 110. Of course, the implementation of the present invention is not limited to the above examples.

In an embodiment, the voltage regulating device 1 may be implemented as a single chip.

In one embodiment, the control circuit 20 may be implemented as a single chip.

Various embodiments of a control circuit 20 for facilitating inrush current reduction for a voltage regulator are provided below.

In one embodiment, the controller 230 is configured to select the request signal S when the request signal S is asserted_SRThe output voltage represented is selected to satisfy the generation of the enable signal S_ENA judgment criterion of the output of the enable signal S_ENTo enable the soft start tracking circuit 220 to operate.

In one embodiment, when the output voltage selection indicates a current output voltage V_OUTTo a voltage higher than the present output voltage V_OUTA target output voltage V of_OUTIn the selection of (2), the controller 230 determines the selection request signal S_SRIndicating that the output voltage selection meets the decision criteria. For example, when receiving an updated selection request signal S_SRWhen and when outputting the latest output selection signal S_OCBefore, the controller 230 will select the request signal S through the update_SRComparing the output voltage selection with the currently selected output voltage selection, and determining the updated selection request signal S_SRWhether the represented output voltage selection satisfies the judgmentA criterion. If so, the controller 230 outputs an enable signal S_ENAnd outputting the selection signal S_OC。

In one embodiment, the controller 230 may be implemented such that when the controller 230 outputs the output selection signal S_OSThen, the enable signal S effective in a period is output_ENCausing the soft-start tracking circuit 220 to operate. For example, the time period may be set to 50ms, 100ms, 200ms, 300ms, and any suitable time period suitable for effectively and actively reducing inrush current during voltage level shifting. Of course, the implementation of the present invention is not limited to the above examples.

Referring to fig. 4, an embodiment of the control circuit 20 for the voltage regulator 10 of fig. 1 is shown in schematic diagram form. As shown in fig. 4, the soft-start tracking circuit 220 may be implemented to include an operational amplifier 221. In this example, the operational amplifier 221, when enabled, may be configured to output at the output terminal N_OUTIs following the first input terminal N_IN1Such that the soft-start signal provided by the soft-start circuit substantially follows the feedback signal from the voltage regulator 10. The operational amplifier 221 may provide a soft start signal S sufficient for the soft start signal S_STFollows the feedback signal S_FBWhile from the first input terminal N_IN1Drawing little current.

In FIG. 4, soft-start circuit 210 may be implemented using a current source I coupled to it_REFSuch as a capacitor.

Referring to fig. 5A, one embodiment of the controller 230 of the control circuit 20 of fig. 4 is shown in schematic diagram form. As shown in fig. 5A, the controller 230A includes a decoder 231 and a detection circuit 232, which may be implemented by using any logic circuit, such as a latch, a flip-flop, a logic gate, a register, or any other suitable circuit component.

For example, as shown in FIG. 5A, if the selection request signal S is implemented in the form of two digital signals denoted by S0 and S1_SRThen the decoder 231 may convert the two digital signals to be used as the output control signal S according to table 1 below_OCA plurality of output digital signals. Referring to fig. 4, the control signal S is output_OCFor example, may be implemented as or further converted to control signals S for controlling switches SW1-SW3_V1、S_V2And S_V3Such that the voltage regulator 10 is capable of providing the output voltage V at one of the desired voltage levels_OUT. In addition, the control signal S_BPFor example for bypass mode. Of course, the implementation of the present invention is not limited to the above examples.

S1	S0	Output voltage level
			0	0	Bypass mode (e.g., 4.2V)
0	1	A first voltage level (e.g., 6.2V)
			1	0	A second voltage level (e.g., 7.5V)
1	1	A third voltage level (e.g., 9.05V)

Table 1

The detection circuit 232 may be implemented to determine the selection request signal S_SRIndicating whether the output voltage selection satisfies a decision criterion, e.g. one of the above-mentioned embodiments, for selectively outputting the enable signal S_EN. The detection circuit 232 can select the request signal S by an update_SRAn output voltage selection represented (e.g., by SEL 1) and by a current one of the select request signals S_SRThe output voltage selections represented (e.g., by SEL0) are compared, where one or both of the output voltage selections (e.g., SEL1 or SEL0) may be stored for comparison. Further, detection circuitry 232 may be implemented to determine whether any transitions from SEL0 to SEL1 satisfy the determination criteria by operations such as calculations, look-up tables, state machines, conditional logic, or any suitable operation. Of course, the implementation of the present invention is not limited to the above examples.

In another embodiment, as shown in FIG. 5B, the controller 230 may be implemented using a programmable circuit 300, such as a microprocessor, a microcontroller, or the like.

In the above embodiments as shown in fig. 1, 4, 5A or 5B, the controller (such as 230, 231 or 300) may optionally be configured to output said output selection signal S_OS. However, the implementation of the present invention is not limited to the above examples. For example, the selection signal S is output_OSMay be implemented in an external controller (such as 230, 231 or 300) or an internal voltage regulator 10.

Referring to fig. 7, another embodiment of a control circuit for facilitating inrush current reduction for a voltage regulator is shown in schematic form. As shown in fig. 7, a control circuit 30 is used to facilitate inrush current reduction for a voltage regulator 10A. The voltage regulator 10A is implemented based on the voltage regulator 10 of fig. 1, or further integrated with a decoding or generation selection request signal S_SRSuch as the function of the decoder 231 illustrated in fig. 5A or in other related ways. In this embodiment, soft-start circuit 210 is considered an environmental component, such that control circuit 30 can be used in a voltage regulator to which control circuit 30 can be appliedSuch as voltage regulator 10A shown in fig. 7 having a soft start circuit 210 coupled to voltage regulator 10A.

As shown in fig. 7, the control circuit 30 includes a soft-start tracking circuit 200 and a controller 310. The soft start tracking circuit 200 includes a first input terminal N_IN1For receiving a feedback signal S from the voltage regulator 10A_FBA second input terminal N_IN2And an output terminal N_OUTWherein the second input terminal N_IN2And an output terminal N_OUTIs used to couple to a soft start circuit 210 to provide a soft start control terminal N_SCProviding a soft start signal S_ST. A controller 310 coupled to the soft start tracking circuit 220 and configured to respond to the selection request signal S_SRTo selectively output an enable signal S_ENTo the soft start tracking circuit 220. Soft start tracking circuit 220 is responsive to enable signal S_ENBut is operable such that the soft start signal S provided by the soft start circuit 210_STSubstantially following the feedback signal S from the voltage regulator 10A_FB。

In one embodiment, the controller 220 may be implemented to include a detection circuit 311, the detection circuit 311 being configured to detect when, for example, the selection request signal S_SRThe output voltage represented is selected to satisfy the generation of the enable signal S_ENA judgment criterion of the output of the enable signal S_ENTo enable the soft start tracking circuit to operate. The detection circuit 311 may be implemented based on the detection circuit 232 or any other suitable circuit, or a programmable circuit such as the examples described above.

In one embodiment, the detection circuit 311 determines that the output voltage selection satisfies the decision criterion when the output voltage selection indicates a selection from a current output voltage to a target output voltage higher than the current output voltage.

In one embodiment, the detection circuit 311 outputs the enable signal S that is asserted for a period of time_ENTo enable the soft start tracking circuit 220.

Further, in some embodiments for practical applications, the voltage regulating device1, the

control unit

20 or 30 can be used in an electronic device, such as a computing device, e.g., a smart phone or a tablet computer, a notebook computer, etc. In some cases, the voltage regulating device 1 may be used to drive a microphone or an earphone for playing sound, wherein a user of the computing means may adjust the volume of the sound, and a selection request signal S_SRMay be generated directly or indirectly by a processing unit of the computing device. Since the voltage regulating device 1 can cause a reduced inrush current and an overshoot voltage, the voltage regulating device 1 or the

control unit

20 or 30 can also prevent component damage in the electronic apparatus caused by the inrush current.

In summary, embodiments of a control circuit and a voltage regulating device having inrush current reduction for facilitating inrush current reduction for a voltage regulator are provided, where the control circuit has a soft-start tracking circuit operable in response to an enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator. In this way, whenever a level transition of the output voltage of the voltage regulator will cause an inrush current to be generated along with the output voltage, the control circuit outputs the enable signal to provide a soft start signal following the feedback signal to the voltage regulator to restart the soft start function of the voltage regulator during the level transition, thereby effectively and proactively reducing the inrush current.

Although the present invention has been described in terms of specific embodiments only, various modifications, combinations, and alterations can be made thereto by those of ordinary skill in the art without departing from the scope and spirit of the invention as set forth in the claims.

The above description is only an example of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. A control circuit for facilitating inrush current reduction for a voltage regulator, the voltage regulator for variably providing an output voltage in response to an output voltage selection, the control circuit comprising:

a soft start circuit for providing a soft start signal;

a soft-start tracking circuit including a first input terminal for receiving a feedback signal from the voltage regulator, a second input terminal coupled to the soft-start circuit, and an output terminal coupled to the soft-start circuit;

a controller coupled to the soft start circuit, the controller configured to selectively output an enable signal to the soft start tracking circuit according to the output voltage selection,

wherein the soft-start tracking circuit is operable in response to the enable signal such that a soft-start signal provided by the soft-start circuit substantially follows a feedback signal from the voltage regulator.

2. The control circuit of claim 1, wherein the controller is configured to output the enable signal to cause the soft-start tracking circuit to operate when the output voltage selection satisfies a criterion for generating the enable signal.

3. The control circuit of claim 2, wherein the controller determines that the output voltage selection satisfies the decision criterion when the output voltage selection represents a selection from a present output voltage to a target output voltage higher than the present output voltage.

4. The control circuit of claim 1, wherein the controller is further configured to output an output selection signal in response to the output voltage selection for notifying the voltage regulator of the output voltage selection.

5. The control circuit of claim 4, wherein when the controller outputs the output select signal, the controller outputs an enable signal that is active for a period of time to cause the soft start tracking circuit to operate.

6. A voltage regulation device with inrush current reduction, comprising:

a voltage regulator responsive to an output voltage selection to variably provide an output voltage, the voltage regulator including a soft start terminal, an output voltage terminal, and a feedback terminal; and

a control circuit coupled to the voltage regulator, the control circuit comprising:

a soft start circuit coupled to the soft start terminal for providing a soft start signal to the voltage regulator;

a soft-start tracking circuit including a first input terminal for receiving a feedback signal output from a feedback terminal of the voltage regulator, a second input terminal coupled to the soft-start circuit, and an output terminal coupled to the soft-start circuit; and

a controller coupled to the soft start tracking circuit, the controller configured to selectively output an enable signal to the soft start circuit according to the output voltage selection,

7. The voltage regulation device of claim 6, wherein the voltage regulator is a linear voltage regulator or a switching voltage regulator.

8. The voltage regulation device of claim 6, wherein the voltage regulator comprises:

an error amplifier coupled to the feedback terminal, the soft start terminal, and a reference voltage terminal;

an output circuit stage coupled between an output terminal of the error amplifier and the output voltage terminal; and

a switchable voltage divider coupled between the output voltage terminal and the feedback terminal for providing the feedback signal in response to the output voltage selection to vary the output voltage.

9. The voltage regulation device of claim 6, wherein the controller is configured to output the enable signal to cause the soft-start tracking circuit to operate when the output voltage selection satisfies a criterion for generating the enable signal.

10. The voltage regulating device according to claim 9, wherein the controller determines that the output voltage selection satisfies the judgment criterion when the output voltage selection represents a selection from a present output voltage to a target output voltage higher than the present output voltage.

11. The voltage regulation device of claim 6, wherein the controller is further configured to output an output selection signal in response to the output voltage selection for notifying the voltage regulator of the transmission voltage selection.

12. The voltage regulation device of claim 11, wherein when the controller outputs the output selection signal, the controller outputs an enable signal that is active for a period of time to cause the soft-start tracking circuit to operate.

13. The voltage regulation device of claim 6, wherein the voltage regulation device is a single chip.

14. A control circuit for facilitating inrush current reduction for a voltage regulator, the voltage regulator for variably providing an output voltage in response to an output voltage selection, the control circuit comprising:

a soft-start tracking circuit comprising a first input terminal for receiving a feedback signal from the voltage regulator, a second input terminal, and an output terminal, wherein the second input terminal and the output terminal are for coupling to a soft-start circuit for providing a soft-start signal;

a controller coupled to the soft start tracking circuit, the controller configured to selectively output an enable signal to the soft start tracking circuit according to the output voltage selection,

15. The control circuit of claim 14, wherein the control circuit comprises a detection circuit configured to output the enable signal to cause the soft-start tracking circuit to operate when the output voltage selection satisfies a criterion for generating the enable signal.

16. The control circuit of claim 15 wherein the detection circuit determines that the output voltage selection satisfies the decision criterion when the output voltage selection represents a selection from a present output voltage to a target output voltage higher than the present output voltage.

17. The control circuit of claim 14, wherein the detection circuit outputs an enable signal that is active for a period of time to cause the soft start tracking circuit to operate.