Low dropout linear regulators and electronic products

Abstract

This invention provides a low-dropout linear regulator and electronic product, comprising: a voltage regulator module and a soft-start current-limiting protection module; the voltage regulator module includes a power transistor connected between the power supply terminal and the output terminal, and drives the power transistor based on the difference between the feedback voltage of the output voltage at the output terminal and a first reference voltage, so that the output voltage is stabilized at a set value; the soft-start current-limiting protection module receives the output voltage and a second reference voltage, and its output terminal is connected to the control terminal of the power transistor, and clamps the gate-source voltage of the power transistor during the startup phase or when the voltage regulator module is short-circuited based on the comparison result of the output voltage and the second reference voltage, thereby limiting the maximum current flowing through the power transistor. The low-dropout linear regulator of this invention has a simple structure, low cost, fast startup speed, and high safety.

Description

Technical Field

[0001] This utility model relates to the field of integrated circuit technology, and in particular to a low dropout linear regulator and electronic product. Background Technology

[0002] An LDO (Low Dropout Regulator) is a linear voltage regulator circuit whose core function is to convert an unstable input voltage (typically higher than the output voltage) into a stable, low-noise output voltage, requiring only a very small input-output voltage difference to operate normally. It is one of the most commonly used power management chips in electronic devices, especially suitable for noise-sensitive applications with low power requirements.

[0003] To ensure the normal operation of an LDO, current limiting protection is required. Traditional current limiting protection schemes introduce current or voltage sampling, adjusting the current magnitude through the amplified feedback signal to achieve current limiting control. These schemes generally suffer from problems such as complex feedback loop structures, high power consumption, and slow response speeds. One LDO circuit with soft-start and foldback current limiting protection functions dynamically adjusts the current limiting value based on the output voltage, solving the problem of startup failure with constant current loads through a soft-start circuit. However, it still requires an additional soft-start circuit to ensure normal startup; both the current limiting circuit and the soft-start circuit are relatively complex, and the startup time is relatively long.

[0004] Therefore, how to shorten startup time, simplify circuit structure, and reduce cost while ensuring the normal and stable operation of LDO has become one of the problems that urgently need to be solved by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this utility model and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this utility model. Utility Model Content

[0006] In view of the shortcomings of the prior art described above, the purpose of this utility model is to provide a low dropout linear regulator and electronic product to solve the problems of long start-up time and complex current limiting protection circuit structure of the existing technology.

[0007] To achieve the above and other related objectives, this utility model provides a low dropout linear regulator, which includes at least:

[0008] Voltage regulator module and soft-start current limiting protection module;

[0009] The voltage regulator module includes a power transistor connected between the power supply terminal and the output terminal. The voltage regulator module drives the power transistor based on the difference between the feedback voltage of the output voltage at the output terminal and the first reference voltage, so that the output voltage is stabilized at a set value.

[0010] The soft-start current limiting protection module receives the output voltage and the second reference voltage. Its output terminal is connected to the control terminal of the power transistor. Based on the comparison result between the output voltage and the second reference voltage, the module clamps the gate-source voltage of the power transistor during the startup phase or when the voltage regulator module is short-circuited, thereby limiting the maximum current flowing through the power transistor.

[0011] Optionally, the soft-start current limiting protection module includes a comparator, a switching transistor, and a diode;

[0012] The first input terminal of the comparator is connected to the output voltage, and the second input terminal is connected to the second reference voltage, for comparing the output voltage with the second reference voltage and outputting the comparison result;

[0013] The anode of the diode is connected to the power supply terminal, and the cathode is connected to the control terminal of the power transistor via the switching transistor.

[0014] The control terminal of the switching transistor is connected to the output terminal of the comparator, and the switching transistor is turned on or off based on the comparison result.

[0015] Alternatively, the switching transistor is a PMOS switching transistor.

[0016] Alternatively, the diode may be implemented using a diode-connected PMOS transistor.

[0017] Optionally, the first reference voltage is equal to the second reference voltage.

[0018] Optionally, the voltage regulator module further includes an error amplifier and a feedback unit;

[0019] The feedback unit is connected between the output terminal and the ground terminal, and generates the feedback voltage based on the output voltage.

[0020] The first input terminal of the error amplifier is connected to the feedback voltage, and the second input terminal is connected to the first reference voltage. The difference between the feedback voltage and the first reference voltage is amplified and output to control the control terminal of the power transistor.

[0021] Alternatively, the voltage regulator module may further include a filter capacitor, one end of which is connected to the output terminal and the other end is grounded.

[0022] Alternatively, the feedback unit includes a first resistor and a second resistor connected in series, and the connection node between the first resistor and the second resistor outputs the feedback voltage.

[0023] Alternatively, the power transistor is a PMOS transistor.

[0024] To achieve the above and other related objectives, this utility model also provides an electronic product, which includes at least the aforementioned low-dropout linear regulator.

[0025] As described above, the low-dropout linear regulator and electronic product of this invention have the following beneficial effects:

[0026] 1. This invention relates to a low-dropout linear regulator and electronic products that directly sample the output voltage. A comparator compares the sampled voltage with a reference voltage, and the comparison result is used to control the current-limiting protection switch. After the comparison result triggers the current-limiting protection, a diode clamps the gate voltage of the power transistor. Therefore, this invention achieves current-limiting protection while simplifying the circuit structure and avoiding the introduction of additional feedback loops, thus reducing costs.

[0027] 2. The low-dropout linear regulator and electronic products of this utility model directly apply current limiting protection to the soft-start process, avoiding large overshoot currents during power-on and further improving the safety of the low-dropout linear regulator.

[0028] 3. The low dropout linear regulator and electronic products of this utility model adopt a soft start current limiting protection module to solve the problems of surge and voltage overshoot during startup and overcurrent after short circuit, further simplifying the circuit structure.

[0029] 4. The low-dropout linear regulator and electronic products of this utility model do not need to be slowly charged through a large capacitor during soft start, but instead start with the maximum current limit, which greatly speeds up the start-up speed. Attached Figure Description

[0030] Figure 1 The diagram shown is a structural schematic of the low-dropout linear regulator of this utility model.

[0031] Figure 2 The diagram shown illustrates the working principle of the low-dropout linear regulator of this invention.

[0032] Component designation explanation

[0033] 1. Low dropout linear regulator

[0034] 11 Voltage Regulator Module

[0035] 111 Error Amplifier

[0036] 112 Feedback Unit

[0037] 12 Soft Start Current Limiting Protection Module

[0038] 121 comparator Detailed Implementation

[0039] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model.

[0040] Please see Figures 1-2 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of this utility model. Therefore, the drawings only show the components related to this utility model and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0041] like Figure 1 As shown, this utility model provides a low dropout linear regulator 1, which includes:

[0042] Voltage regulator module 11 and soft start current limiting protection module 12.

[0043] like Figure 1 As shown, the voltage regulator module 11 includes a power transistor MP connected between the power supply terminal and the output terminal. The voltage regulator module 11 drives the power transistor MP based on the difference between the feedback voltage VFB of the output voltage VOUT at the output terminal and the first reference voltage VBG1, so that the output voltage VOUT is stabilized at the set value.

[0044] Specifically, as an example, the voltage regulator module 11 includes a power transistor MP, an error amplifier 111, and a feedback unit 112.

[0045] In this embodiment, one end of the power transistor MP is connected to the power supply terminal, the other end is connected to the output terminal, and the control terminal is connected to the output terminal of the error amplifier 111. In this example, the power transistor MP is implemented using a PMOS transistor; in practical applications, any type of device that can adjust the current based on the control of the error amplifier 111 is applicable to the power transistor MP of this invention, and is not limited to this embodiment.

[0046] Feedback unit 112 is connected between the output terminal and the ground terminal, generating a feedback voltage VFB based on the output voltage VOUT. In this example, feedback unit 112 includes a first resistor R1 and a second resistor R2 connected in series; that is, the first end of the first resistor R1 is connected to the output terminal, the second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is grounded, and the connection node of the first resistor R1 and the second resistor R2 outputs the feedback voltage VFB; the output voltage VOUT is divided by the first resistor R1 and the second resistor R2 to obtain the corresponding feedback voltage VFB. In practical use, any circuit structure that can generate a feedback voltage VFB is applicable to the feedback unit 112 of this invention, and will not be described in detail here.

[0047] Error amplifier 111 connects its first input terminal to the feedback voltage VFB and its second input terminal to the first reference voltage VBG1. It amplifies and outputs the difference between the feedback voltage VFB and the first reference voltage VBG1 to control the control terminal of the power transistor MP. In this example, the first input terminal of error amplifier 111 is a non-inverting input terminal, and the second input terminal is an inverting input terminal. In practical applications, the correspondence between the input signals and the polarities of the input terminals of error amplifier 111 can be adjusted according to the control logic; this will not be elaborated upon here.

[0048] Furthermore, in one example, the voltage regulator module 11 also includes a filter capacitor C, one end of which is connected to the output terminal and the other end is grounded.

[0049] It should be noted that the voltage regulator module 11 adjusts the current flowing through the power transistor MP by the difference between the feedback voltage VFG and the first reference voltage VBG1, so that the feedback voltage VFG is close to or equal to the first reference voltage VBG1, thereby obtaining a stable output voltage VOUT with a set value. In practical use, any circuit structure that can achieve low dropout linear voltage regulation is applicable to the voltage regulator module 11 of this utility model, and is not limited to this embodiment.

[0050] like Figure 1 As shown, the soft-start current limiting protection module 12 receives the output voltage VOUT and the second reference voltage VBG2. The output terminal is connected to the control terminal of the power transistor MP. Based on the comparison result between the output voltage VOUT and the second reference voltage VBG2, the gate-source voltage of the power transistor MP is clamped during the startup phase or when the voltage regulator module 11 is short-circuited, thereby limiting the maximum current flowing through the power transistor MP.

[0051] Specifically, in this embodiment, the soft-start current limiting protection module 12 includes a comparator 121, a switching transistor MS, and a diode MD.

[0052] In this embodiment, the first input terminal of comparator 121 is connected to the output voltage VOUT, and the second input terminal is connected to the second reference voltage VBG2. This comparator compares the output voltage VOUT with the second reference voltage VBG2 and outputs the comparison result VCOMP. In this example, the first input terminal of comparator 121 is a non-inverting input terminal, and the second input terminal is an inverting input terminal. In practical applications, the correspondence between the input signals and the polarities of the input terminals of comparator 121 can be adjusted according to the control logic, and this embodiment is not the only limitation.

[0053] It should be noted that the first reference voltage VBG1 is determined based on the set value of the output voltage VOUT, and the second reference voltage VBG2 is used to determine whether the voltage regulator module 11 is in the startup phase or whether a short circuit has occurred. Therefore, the first reference voltage VBG1 and the second reference voltage VBG2 can be set separately as needed. In this embodiment, to simplify the circuit, the first reference voltage VBG1 and the second reference voltage VBG2 are set to be equal.

[0054] The anode of diode MD is connected to the power supply terminal, and the cathode is connected to the control terminal of power transistor MP via switching transistor MS, used to clamp the gate-source voltage of power transistor MP. As an example, diode MD is implemented using a diode-connected PMOS transistor, with the source of the PMOS transistor connected to the power supply terminal, and the gate and drain connected to switching transistor MS. In practical applications, other diodes with clamping functions can also be used, which will not be elaborated here.

[0055] The control terminal of the switching transistor MS is connected to the output terminal of comparator 121, and the switching transistor MS is turned on or off based on the comparison result VCOMP. In this example, the switching transistor MS is a PMOS switch, with its source connected to the cathode of diode MD and its drain connected to the gate of power transistor MP. The control terminal receives the comparison result VCOMP. When the comparison result VCOMP is high, the switching transistor MS is off and diode MD is not working; when the comparison result VCOMP is low, the switching transistor MS is on and diode MD is working. In practical applications, other switching devices can also be used for the switching transistor MS, which will not be elaborated here.

[0056] like Figure 2 As shown, the power supply voltage VIN is input at the power supply terminal, and then the first reference voltage VBG1 and the second reference voltage VBG2 are established at time t0 (which can be generated by a bandgap reference circuit). In this embodiment, VBG1 and VBG2 are set to 1.2V.

[0057] like Figure 2As shown, at time t1, when the low-dropout linear regulator 1 starts up, the first reference voltage VBG1 and the second reference voltage VBG2 have been established, while the regulator module 11 has not yet been established, and the output voltage VOUT = 0V (and increases slowly). The gate voltage VG of the power transistor MP is at a logic low level. Therefore, it can be concluded that: the comparison result VCOMP is at a logic low level, the switching transistor MS is turned on, and the diode MD is turned on, clamping the gate potential of the power transistor MP to near VIN-VTH (VTH is the threshold voltage of the diode-connected transistor), causing the current flowing through the power transistor MP to rise rapidly and be established at time t2 (limited to the maximum allowable load current I in the design). MAX This prevents potential voltage overshoot and inrush current. Furthermore, the soft-start time meets the following requirements: (where T) SS For soft start time, I MP (This refers to the charging current flowing through the power transistor during soft start); in traditional applications, I... MP The smaller size results in a longer soft-start time and slower startup speed; however, in this invention, I... MP =I MAX This means that the LDO is always started at its maximum operating current, resulting in a short soft-start time and fast startup speed.

[0058] With I MP As the circuit continues to charge, the output voltage VOUT gradually increases. At time t3, comparator 121 detects that the output voltage VOUT > the second reference voltage VBG2, indicating that the voltage regulator module 11 has completed startup (LDO setup is complete). The comparison result VCOMP's potential jumps to logic high, and the operating mode switches from current limiting mode to normal operating mode. The switching transistor MS is turned off, and the diode MD is open-circuited, having no impact on the normal operation of the circuit. At time t4, the output voltage VOUT reaches and stabilizes at the set value.

[0059] At time t5, when a short circuit occurs in the voltage regulator module 11, a short-circuit current I will appear in the power transistor MP. SHORT Meanwhile, the output voltage VOUT begins to decrease. At time t6, comparator 121 detects an overcurrent in the voltage regulator module 11, and the comparison result VCOMP's potential jumps to logic low. Switch MS turns on, and diode MD turns on, clamping the gate potential (VG) of power transistor MP to near VIN-VTH, thus limiting the current flowing through power transistor MP to I. MAX That is, short-circuit current I SHORT Restricted to I MAX This prevents damage to the power transistor MP. At time t7, the voltage regulator module 11 is short-circuited, and the output voltage VOUT is pulled down to near 0V.

[0060] The soft-start current limiting protection module 12 in the low-dropout linear regulator 1 of this invention has a simple structure, does not require additional circuitry to ensure the normal startup of the low-dropout linear regulator, and has a fast startup speed. This invention uses a single soft-start current limiting protection module to simultaneously solve the problems of surge and voltage overshoot during startup as well as the overcurrent problem after a short circuit.

[0061] This invention also provides an electronic product, which includes at least: the low dropout linear regulator 1 of this invention; used to power other modules in the electronic product.

[0062] In summary, this utility model provides a low-dropout linear regulator and electronic product, including: a voltage regulator module and a soft-start current-limiting protection module; the voltage regulator module includes a power transistor connected between the power supply terminal and the output terminal, and drives the power transistor based on the difference between the feedback voltage of the output voltage at the output terminal and a first reference voltage, so that the output voltage is stabilized at a set value; the soft-start current-limiting protection module receives the output voltage and a second reference voltage, and its output terminal is connected to the control terminal of the power transistor. Based on the comparison result between the output voltage and the second reference voltage, it clamps the gate-source voltage of the power transistor during the startup phase or when the voltage regulator module is short-circuited, thereby limiting the maximum current flowing through the power transistor. The low-dropout linear regulator of this utility model has a simple structure, low cost, fast startup speed, and high safety. Therefore, this utility model effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0063] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A low-dropout linear regulator, characterized in that, The low-dropout linear regulator includes at least: Voltage regulator module and soft-start current limiting protection module; The voltage regulator module includes a power transistor connected between the power supply terminal and the output terminal. The voltage regulator module drives the power transistor based on the difference between the feedback voltage of the output voltage at the output terminal and the first reference voltage, so that the output voltage is stabilized at a set value. The soft-start current limiting protection module receives the output voltage and the second reference voltage. Its output terminal is connected to the control terminal of the power transistor. Based on the comparison result between the output voltage and the second reference voltage, the module clamps the gate-source voltage of the power transistor during the startup phase or when the voltage regulator module is short-circuited, thereby limiting the maximum current flowing through the power transistor.

2. The low-dropout linear regulator according to claim 1, characterized in that: The soft-start current limiting protection module includes a comparator, a switching transistor, and a diode; The first input terminal of the comparator is connected to the output voltage, and the second input terminal is connected to the second reference voltage, for comparing the output voltage with the second reference voltage and outputting the comparison result; The anode of the diode is connected to the power supply terminal, and the cathode is connected to the control terminal of the power transistor via the switching transistor. The control terminal of the switching transistor is connected to the output terminal of the comparator, and the switching transistor is turned on or off based on the comparison result.

3. The low-dropout linear regulator according to claim 2, characterized in that: The switching transistor is a PMOS switching transistor.

4. The low-dropout linear regulator according to claim 2, characterized in that: The diode is implemented using a PMOS transistor connected in diode configuration.

5. The low-dropout linear regulator according to claim 1, characterized in that: The first reference voltage is equal to the second reference voltage.

6. The low-dropout linear regulator according to claim 1, characterized in that: The voltage regulator module also includes an error amplifier and a feedback unit; The feedback unit is connected between the output terminal and the ground terminal, and generates the feedback voltage based on the output voltage. The first input terminal of the error amplifier is connected to the feedback voltage, and the second input terminal is connected to the first reference voltage. The difference between the feedback voltage and the first reference voltage is amplified and output to control the control terminal of the power transistor.

7. The low-dropout linear regulator according to claim 6, characterized in that: The voltage regulator module also includes a filter capacitor, one end of which is connected to the output terminal and the other end is grounded.

8. The low-dropout linear regulator according to claim 6, characterized in that: The feedback unit includes a first resistor and a second resistor connected in series, and the connection node between the first resistor and the second resistor outputs the feedback voltage.

9. The low-dropout linear regulator according to any one of claims 1, 6-8, characterized in that: The power transistor is a PMOS transistor.

10. An electronic product, characterized in that, The electronic product includes at least: a low-dropout linear regulator as described in any one of claims 1-9.

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