Turn-back overcurrent protection circuit and linear voltage regulator

Abstract

The invention provides a turn-back overcurrent protection circuit and a linear voltage regulator, and the turn-back overcurrent protection circuit comprises a turn-back switch module which compares an output voltage with a preset voltage, and outputs a turn-back current when the output voltage is smaller than or equal to the preset voltage; and the overcurrent protection module is connected with the turn-back switch module, performs overcurrent protection on the linear voltage regulator based on the first current limiting point when the turn-back switch module does not output the turn-back current, and reduces the current limiting point from the first current limiting point to a second current limiting point based on the turn-back current when the turn-back switch module outputs the turn-back current, and over-current protection is carried out on the linear voltage regulator based on the second current limiting point. According to the invention, the problem of circuit damage caused by overlarge output current due to short circuit or overload in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of linear voltage stabilizers, and in particular to a foldback overcurrent protection circuit and a linear voltage stabilizer. Background Art

[0002] Linear regulators are widely used in various electronic devices. However, due to various factors, linear regulators often short-circuit or overload, resulting in increased output current and thus circuit damage. Therefore, how to prevent the high current from damaging the circuit when a linear regulator short-circuits or overloads is a technical problem that technicians in this field urgently want to solve.

[0003] It should be noted that the above technical background is merely provided to provide a clear and complete description of the technical solutions of the present invention and to facilitate understanding by those skilled in the art. Simply because these solutions are described in the technical background section of the present invention, it should not be assumed that the above technical solutions are well known to those skilled in the art. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a foldback overcurrent protection circuit and a linear regulator to solve the problem in the prior art that the output current is too large due to short circuit or overload, causing circuit damage.

[0005] To achieve the above and other related objectives, the present invention provides a foldback overcurrent protection circuit suitable for a linear voltage regulator, comprising:

[0006] a foldback switch module, which compares an output voltage with a preset voltage and outputs a foldback current when the output voltage is less than or equal to the preset voltage, wherein the output voltage is the voltage output by the linear regulator;

[0007] an overcurrent protection module connected to the foldback switch module, and performing overcurrent protection on the linear regulator based on a first current limiting point when the foldback switch module does not output the foldback current; and reducing the current limiting point from the first current limiting point to a second current limiting point based on the foldback current when the foldback switch module outputs the foldback current, and performing overcurrent protection on the linear regulator based on the second current limiting point.

[0008] Optionally, the foldback switch module includes a first transistor, a second transistor, a first current source and a second current source, the control end of the first transistor receives the output voltage, the first end of the first transistor is connected to the reference ground, the second end of the first transistor is connected to the control end of the second transistor and connected to the operating voltage via the first current source, the first end of the second transistor is connected to the reference ground via the second current source, and the second end of the second transistor serves as the output end of the foldback switch module.

[0009] Optionally, the foldback switch module includes a first comparator, a third transistor and a third current source, the non-inverting input terminal of the first comparator receives the preset voltage, the inverting input terminal of the first comparator receives the output voltage, the output terminal of the first comparator is connected to the control terminal of the third transistor, the first terminal of the third transistor is connected to the reference ground via the third current source, and the second terminal of the third transistor serves as the output terminal of the foldback switch module.

[0010] Optionally, the return switch module further includes a signal shaping unit connected between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor, performing signal shaping without changing the phase.

[0011] Optionally, the signal shaping unit includes a first in-phase Schmitt trigger; or, the signal shaping unit also includes a first inverter and a second inverter, which are sequentially connected in series between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor.

[0012] Optionally, the signal shaping unit includes a first inverting Schmitt trigger and a third inverter, which are sequentially connected in series between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor.

[0013] Optionally, the foldback switch module includes a second comparator, a fourth transistor, a fourth current source and a fourth inverter, the non-inverting input of the second comparator receives the output voltage, the inverting input of the second comparator receives the preset voltage, the output of the second comparator is connected to the input of the fourth inverter, the output of the fourth inverter is connected to the control end of the fourth transistor, the first end of the fourth transistor is connected to the reference ground via the fourth current source, and the second end of the fourth transistor serves as the output end of the foldback switch module.

[0014] Optionally, the foldback switch module further includes a signal shaping unit, which replaces the fourth inverter and performs signal shaping with phase inversion.

[0015] Optionally, the signal shaping unit includes a second inverting Schmitt trigger; or, the signal shaping unit further includes a fifth inverter and a sixth inverter, which are sequentially connected in series between the output end of the second comparator and the control end of the fourth transistor.

[0016] Optionally, the signal shaping unit includes a second in-phase Schmitt trigger and a seventh inverter, which are sequentially connected in series between the output terminal of the second comparator and the control terminal of the fourth transistor.

[0017] Optionally, the overcurrent protection module includes a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a fifth current source, a sixth current source and a first resistor, the control end of the fifth transistor is connected to the control end of the power tube in the linear regulator, the first end of the fifth transistor is connected to the first end of the power tube via the first resistor, the second end of the fifth transistor is connected to the second end of the power tube, the control end of the sixth transistor is connected to the control end of the seventh transistor, the first end of the sixth transistor is connected to the power supply voltage, the second end of the sixth transistor is connected to its control end and connected to the reference ground via the fifth current source, the first end of the seventh transistor is connected to the first end of the fifth transistor, the second end of the seventh transistor is connected to the control end of the eighth transistor and connected to the reference ground via the sixth current source, the second end of the seventh transistor is also connected to the output end of the foldback switch module, the first end of the eighth transistor is connected to the power supply voltage, and the second end of the eighth transistor serves as the output end of the foldback overcurrent protection circuit to be connected to the control end of the power tube.

[0018] The present invention also provides a linear voltage regulator, comprising:

[0019] A foldback overcurrent protection circuit as described in any one of the above;

[0020] A voltage stabilization adjustment circuit is connected to the foldback overcurrent protection circuit, converts the power supply voltage into an output voltage, and stabilizes the output based on the comparison between the feedback voltage and the reference voltage, wherein the feedback voltage is positively correlated with the output voltage.

[0021] Optionally, the voltage regulation circuit includes a power tube, a feedback module and an error amplifier, wherein:

[0022] The first end of the power tube is connected to the power supply voltage, the second end of the power tube is connected to the reference ground via the feedback module and generates the output voltage, and the control end of the power tube is connected to the error amplifier and the output end of the foldback overcurrent protection circuit;

[0023] The feedback module generates the feedback voltage based on the output voltage;

[0024] The first input terminal of the error amplifier receives the feedback voltage, the second input terminal of the error amplifier receives the reference voltage, and generates a control signal for the power transistor based on a difference between the feedback voltage and the reference voltage;

[0025] Alternatively, the voltage stabilizing and adjusting circuit further includes a buffer connected between the output end of the error amplifier and the control end of the power tube.

[0026] Optionally, the feedback module includes a second resistor and a third resistor, the first end of the second resistor is connected to the second end of the power tube, and the second end of the second resistor is connected to the reference ground via the third resistor to generate the feedback voltage.

[0027] As described above, the foldback overcurrent protection circuit and linear voltage regulator of the present invention establish an overcurrent foldback protection mechanism by switching the current limiting point, and perform overcurrent protection on the linear voltage regulator based on different current limiting points, so that the output current decreases as the output voltage decreases, thereby being able to quickly reduce power consumption in the event of a short circuit or overload, and avoiding damage to the circuit caused by large current. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shown is a structural schematic diagram of a linear regulator including a foldback overcurrent protection circuit according to an embodiment of the present invention.

[0029] Figure 2 Shown is a structural schematic diagram of a foldback switch module in an embodiment of the present invention.

[0030] Figure 3 Shown as Figure 2 A structural diagram of adding a signal shaping unit to the return switch module shown.

[0031] Figure 4 Shown as Figure 2 Another structural schematic diagram of adding a signal shaping unit to the return switch module shown.

[0032] Figure 5 Shown is another structural schematic diagram of the return switch module in an embodiment of the present invention.

[0033] Figure 6 Shown as Figure 5 A structural diagram of adding a signal shaping unit to the return switch module shown.

[0034] Figure 7 Shown as Figure 5 Another structural schematic diagram of adding a signal shaping unit to the return switch module shown.

[0035] Figure 8 Shown is another structural schematic diagram of the return switch module in an embodiment of the present invention.

[0036] Figure 9 Shown as Figure 8 A structural diagram of adding a signal shaping unit to the return switch module shown.

[0037] Figure 10 Shown as Figure 8 Another structural schematic diagram of adding a signal shaping unit to the return switch module shown.

[0038] Figure 11 Display as Figure 1 The waveform diagram shows that when the linear regulator is short-circuited or overloaded, the output current follows the output voltage change.

[0039] Component number description

[0040] 10 Linear Regulator

[0041] 100 Ω Foldback overcurrent protection circuit

[0042] 110 Foldback Switch Module

[0043] 111 Signal Shaping Unit

[0044] 120 Overcurrent protection module

[0045] 200 Voltage Regulating Circuit

[0046] 210 Feedback Module DETAILED DESCRIPTION

[0047] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] See also Figures 1 to 11 It should be noted that the illustrations provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the form, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0049] Example 1

[0050] like Figures 1 to 10 As shown, this embodiment provides a foldback overcurrent protection circuit 100, including a foldback switch module 110 and an overcurrent protection module 120; wherein, the foldback overcurrent protection circuit 100 of this embodiment is suitable for a linear regulator 10, especially a low voltage difference linear regulator.

[0051] The foldback switch module 110 compares the output voltage VOUT with a preset voltage VREF1 and outputs a foldback current Ihyst when the output voltage VOUT is less than or equal to the preset voltage VREF1 ; wherein the output voltage VOUT is the voltage output by the linear regulator 10 .

[0052] In one example, Figure 2 As shown, the foldback switch module 110 includes a first transistor M1, a second transistor M2, a first current source I1, and a second current source I2; the control terminal of the first transistor M1 receives the output voltage VOUT, the first terminal of the first transistor M1 is connected to the reference ground, the second terminal of the first transistor M1 is connected to the control terminal of the second transistor M2, and the second terminal of the first transistor M1 is also connected to the operating voltage AVDD via the first current source I1, that is, the second terminal of the first transistor M1 is connected to the output terminal of the first current source I1, and the input terminal of the first current source I1 is connected to the operating voltage AVDD. The first terminal of the second transistor M2 is connected to the reference ground via the second current source I2, that is, the first terminal of the second transistor M2 is connected to the input terminal of the second current source I2, and the output terminal of the second current source I2 is connected to the reference ground. The second terminal of the second transistor M2 serves as the output terminal of the foldback switch module 110 to output the foldback current Ihyst; wherein the first transistor M1 and the second transistor M2 are NMOS transistors, and the control terminal refers to the gate terminal, the first terminal refers to the source terminal, and the second terminal refers to the drain terminal.

[0053] In this example, the first transistor M1 is used as a detection tube to detect the output voltage VOUT, and when VOUT*gm1≤I1, that is, VOUT≤I1 / gm1=VREF1, point A flips from a low potential to a high potential, wherein gm1 is the transconductance of the first transistor, and I1 is the current of the first current source; the second transistor M2 is used as a switching tube to determine whether to output the return current Ihyst based on the detection result, and when point A is a high potential, the second transistor M2 is turned on, and the return current Ihyst is output, wherein Ihyst=I2, and I2 is the current of the second current source.

[0054] Further, such as Figure 3 and Figure 4 As shown, the foldback switch module 110 of this example further includes a signal shaping unit 111, which is connected between the second terminal of the first transistor M1 and the control terminal of the second transistor M2, and performs signal shaping without changing the phase. It should be noted that when the foldback switch module 110 includes the signal shaping unit 111, the second terminal of the first transistor M1 and the control terminal of the second transistor M2 are no longer directly connected, but are indirectly connected through the signal shaping unit 111.

[0055] In one embodiment, Figure 3As shown, the signal shaping unit 111 includes a first non-inverting Schmitt trigger SMIT1+, wherein the input terminal of the first non-inverting Schmitt trigger SMIT1+ is connected to the second terminal of the first transistor M1, and the output terminal of the first non-inverting Schmitt trigger SMIT1+ is connected to the control terminal of the second transistor M2. In practical applications, in order to achieve a better signal shaping effect, the Schmitt trigger is usually used in conjunction with an inverter. In this case, in addition to the first non-inverting Schmitt trigger SMIT1+, the signal shaping unit 111 also includes a first inverter INV1 and a second inverter INV2. The three are connected in series between the second terminal of the first transistor M1 and the control terminal of the second transistor M2. That is, the input terminal of the first non-inverting Schmitt trigger SMIT1+ is connected to the second terminal of the first transistor M1, the output terminal of the first non-inverting Schmitt trigger SMIT1+ is connected to the input terminal of the first inverter INV1, the output terminal of the first inverter INV1 is connected to the input terminal of the second inverter INV2, and the output terminal of the second inverter INV2 is connected to the control terminal of the second transistor M2.

[0056] In another embodiment, Figure 4 As shown, the signal shaping unit 111 includes a first inverting Schmitt trigger SMIT1- and a third inverter INV3, which are sequentially connected in series between the second end of the first transistor M1 and the control end of the second transistor M2, that is, the input end of the first inverting Schmitt trigger SMIT1- is connected to the second end of the first transistor M1, the output end of the first inverting Schmitt trigger SMIT1- is connected to the input end of the third inverter INV3, and the output end of the third inverter INV3 is connected to the control end of the second transistor M2.

[0057] In another example, Figure 5 As shown, the foldback switch module 110 includes a first comparator CMP1, a third transistor M3 and a third current source I3; the non-inverting input terminal of the first comparator CMP1 receives a preset voltage VREF1, the inverting input terminal of the first comparator CMP1 receives an output voltage VOUT, the output terminal of the first comparator CMP1 is connected to the control terminal of the third transistor M3, the first terminal of the third transistor M3 is connected to the reference ground via the third current source I3, that is, the first terminal of the third transistor M3 is connected to the input terminal of the third current source I3, the output terminal of the third current source I3 is connected to the reference ground, and the second terminal of the third transistor M3 serves as the output terminal of the foldback switch module 110 to output the foldback current Ihyst; wherein the third transistor M3 is an NMOS tube, and the control terminal refers to the gate terminal, the first terminal refers to the source terminal, and the second terminal refers to the drain terminal.

[0058] In this example, the connection node between the control terminal of the third transistor M3 and the output terminal of the first comparator CMP1 is denoted as point A. The first comparator CMP1 is used to detect the output voltage VOUT. When VOUT ≤ VREF1, point A flips from a low potential to a high potential. The third transistor M3 serves as a switch tube, and is used to determine whether to output the return current Ihyst based on the detection result. When the potential at point A is high, the third transistor M3 is turned on, and the return current Ihyst is output, where Ihyst = I3, and I3 is the current of the third current source.

[0059] Further, such as Figure 6 and Figure 7 As shown, the foldback switch module 110 of this example further includes a signal shaping unit 111, which is connected between the output terminal of the first comparator CMP1 and the control terminal of the third transistor M3, and performs signal shaping without changing the phase. It should be noted that when the foldback switch module 110 includes the signal shaping unit 111, the output terminal of the first comparator CMP1 and the control terminal of the third transistor M3 are no longer directly connected, but are indirectly connected through the signal shaping unit 111.

[0060] In one embodiment, Figure 6 As shown, the signal shaping unit 111 includes a first in-phase Schmitt trigger SMIT1+, wherein the input end of the first in-phase Schmitt trigger SMIT1+ is connected to the output end of the first comparator CMP1, and the output end of the first in-phase Schmitt trigger SMIT1+ is connected to the control end of the third transistor M3. In practical applications, in order to achieve a better signal shaping effect, a Schmitt trigger is usually used in conjunction with an inverter. At this time, in addition to the first in-phase Schmitt trigger SMIT1+, the signal shaping unit 111 also includes a first inverter INV1 and a second inverter INV2. The three are connected in series between the output end of the first comparator CMP1 and the control end of the third transistor M3, that is, the input end of the first in-phase Schmitt trigger SMIT1+ is connected to the output end of the first comparator CMP1, the output end of the first in-phase Schmitt trigger SMIT1+ is connected to the input end of the first inverter INV1, the output end of the first inverter INV1 is connected to the input end of the second inverter INV2, and the output end of the second inverter INV2 is connected to the control end of the third transistor M3.

[0061] In another embodiment, Figure 7As shown in the figure, the signal shaping unit 111 includes a first inverting Schmitt trigger SMIT1- and a third inverter INV3, which are connected in series between the output of the first comparator CMP1 and the control terminal of the third transistor M3, i.e., the input of the first inverting Schmitt trigger SMIT1- is connected to the output of the first comparator CMP1, the output of the first inverting Schmitt trigger SMIT1- is connected to the input of the third inverter INV3, and the output of the third inverter INV3 is connected to the control terminal of the third transistor M3.

[0062] In another example, as shown in the figure, Figure 8 As shown in the figure, the turn-back switch module 110 includes a second comparator CMP2, a fourth transistor M4, a fourth current source I4, and a fourth inverter INV4; the non-inverting input of the second comparator CMP2 receives the output voltage VOUT, the inverting input of the second comparator CMP2 receives the preset voltage VREF1, the output of the second comparator CMP2 is connected to the input of the fourth inverter INV4, the output of the fourth inverter INV4 is connected to the control terminal of the fourth transistor M4, the first terminal of the fourth transistor M4 is connected to the reference ground through the fourth current source I4, i.e., the first terminal of the fourth transistor M4 is connected to the input of the fourth current source I4, the output of the fourth current source I4 is connected to the reference ground, and the second terminal of the fourth transistor M4 serves as the output of the turn-back switch module 110 to output the turn-back current Ihyst; wherein the fourth transistor M4 is an NMOS transistor, and the control terminal refers to the gate terminal, the first terminal refers to the source terminal, and the second terminal refers to the drain terminal.

[0063] In this example, the connection node between the control terminal of the fourth transistor M4 and the output of the fourth inverter INV4 is marked as point A, the second comparator CMP2 is used to detect the output voltage VOUT, and when VOUT≤VREF1, point A is flipped from a low potential to a high potential; the fourth transistor M4 serves as a switch tube to determine whether to output the turn-back current Ihyst according to the detection result, and when point A is at a high potential, the fourth transistor M4 is turned on to output the turn-back current Ihyst, wherein Ihyst=I4, and I4 is the current of the fourth current source.

[0064] Further, as shown in the figures, Figure 9 and Figure 10 As shown in the figures, the turn-back switch module 110 of this example further includes a signal shaping unit 111 to replace the fourth inverter INV4 and perform signal shaping in the case of phase inversion. It should be noted that when the turn-back switch module 110 includes the signal shaping unit 111, the turn-back switch module 110 will no longer include the fourth inverter INV4, and the output of the second comparator CMP2 and the control terminal of the fourth transistor M4 are indirectly connected through the signal shaping unit 111.

[0065] In an embodiment, as Figure 9 As shown, the signal shaping unit 111 includes a second inverting Schmitt trigger SMIT2-, wherein the input end of the second inverting Schmitt trigger SMIT2- is connected to the output end of the second comparator CMP2, and the output end of the second inverting Schmitt trigger SMIT2- is connected to the control end of the fourth transistor M4. In practical applications, in order to achieve a better signal shaping effect, a Schmitt trigger is usually used in conjunction with an inverter. At this time, in addition to the second inverting Schmitt trigger SMIT2-, the signal shaping unit 111 also includes a fifth inverter INV5 and a sixth inverter INV6. The three are connected in series between the output end of the second comparator CMP2 and the control end of the fourth transistor M4, that is, the input end of the second inverting Schmitt trigger SMIT2- is connected to the output end of the second comparator CMP2, the output end of the second inverting Schmitt trigger SMIT2- is connected to the input end of the fifth inverter INV5, the output end of the fifth inverter INV5 is connected to the input end of the sixth inverter INV6, and the output end of the sixth inverter INV6 is connected to the control end of the fourth transistor M4.

[0066] In another embodiment, Figure 10 As shown, the signal shaping unit 111 includes a second in-phase Schmitt trigger SMIT2+ and a seventh inverter INV7, which are sequentially connected between the output terminal of the second comparator CMP2 and the control terminal of the fourth transistor M4, that is, the input terminal of the second in-phase Schmitt trigger SMIT2+ is connected to the output terminal of the second comparator CMP2, the output terminal of the second in-phase Schmitt trigger SMIT2+ is connected to the input terminal of the seventh inverter INV7, and the output terminal of the seventh inverter INV7 is connected to the control terminal of the fourth transistor M4.

[0067] The overcurrent protection module 120 is connected to the foldback switch module 110. When the foldback switch module 110 does not output the foldback current Ihyst, the linear regulator 10 is protected from overcurrent based on the first current limiting point Ioc1. When the foldback switch module 110 outputs the foldback current Ihyst, the current limiting point is reduced from the first current limiting point Ioc1 to the second current limiting point Ioc2 based on the foldback current Ihyst, and the linear regulator 10 is protected from overcurrent based on the second current limiting point Ioc2 to reduce power consumption.

[0068] In one example, Figure 1As shown, the overcurrent protection module 120 comprises a fifth transistor M5, a sixth transistor M6, a seventh transistor M7, an eighth transistor M8, a fifth current source I5, a sixth current source I6 and a first resistor R1; a control terminal of the fifth transistor M5 is connected to a control terminal of the power transistor M0, a first terminal of the fifth transistor M5 is connected to a first terminal of the power transistor M0 through the first resistor R1, that is, the first terminal of the fifth transistor M5 is connected to a first terminal of the first resistor R1, a second terminal of the first resistor R1 is connected to the first terminal of the power transistor M0, a second terminal of the fifth transistor M5 is connected to a second terminal of the power transistor M0, a control terminal of the sixth transistor M6 is connected to a control terminal of the seventh transistor M7, a first terminal of the sixth transistor M6 is connected to a power supply voltage VBAT, a second terminal of the sixth transistor M6 is connected to the control terminal thereof, the second terminal of the sixth transistor M6 is also connected to a reference ground through the fifth current source I5, that is, the second terminal of the sixth transistor M6 is connected to an input terminal of the fifth current source I5, an output terminal of the fifth current source I5 is connected to the reference ground, a first terminal of the seventh transistor M7 is connected to the first terminal of the fifth transistor M5, a second terminal of the seventh transistor M7 is connected to a control terminal of the eighth transistor M8, the second terminal of the seventh transistor M7 is also connected to the reference ground through the sixth current source I6, that is, the second terminal of the seventh transistor M7 is connected to an input terminal of the sixth current source I6, an output terminal of the sixth current source I6 is connected to the reference ground, the second terminal of the seventh transistor M7 is also connected to an output terminal of the foldback switch module 110 to access the foldback current Ihyst, a first terminal of the eighth transistor M8 is connected to the power supply voltage VBAT, a second terminal of the eighth transistor M8 is connected to the output of the foldback overcurrent protection circuit 100 to be connected to the control terminal of the power transistor M0; wherein the fifth transistor M5, the sixth transistor M6, the seventh transistor M7 and the eighth transistor M8 are PMOS transistors, in addition, the power transistor M0 is also a PMOS transistor, and the control terminal refers to a gate terminal, the first terminal refers to a source terminal, and the second terminal refers to a drain terminal.

[0069] In this example, the fifth transistor M5 acts as a mirror transistor, and a sampling current Is is obtained by mirroring the output current Iout flowing through the power transistor M0 in the mirror linear voltage regulator, so as to generate a voltage Vs on the first resistor R1; the sixth transistor M6, the seventh transistor M7, the eighth transistor M8, the fifth current source I5 and the sixth current source I6 constitute a common-gate operational amplifier, wherein the size ratio of the sixth transistor M6 and the seventh transistor M7 is 1:m (m is a natural number greater than 1), and the currents of the fifth current source I5 and the sixth current source I6 are equal. When there is no foldback current Ihyst, the mismatch voltage of the sixth transistor M6 and the seventh transistor M7 is a first mismatch voltage, denoted as Vos1, and the corresponding current limiting point is a first current limiting point, denoted as Ioc1; when there is the foldback current Ihyst, the mismatch voltage of the sixth transistor M6 and the seventh transistor M7 is a second mismatch voltage, denoted as Vos2, and the corresponding current limiting point is a second current limiting point, denoted as Ioc2. Then:

[0070] When the output current Iout is small, the sampling current Is is also small, at this time, Vs=Is*R1<Vos1, the control terminal voltage of the eighth transistor M8 is high, the eighth transistor M8 remains off, and the overcurrent protection is not triggered;

[0071] When the output current Iout gradually increases, the sampling current Is also gradually increases, when Vs≥Vos1, the control terminal voltage of the eighth transistor M8 starts to decrease, the eighth transistor M8 gradually opens to trigger the overcurrent protection, and the control terminal voltage of the power transistor M0 is clamped at a fixed value (i.e., clamped at VBAT-VDS_M8), thereby limiting the size of the output current Iout, at this time, the corresponding current limiting point is Ioc1;

[0072] When the output current Iout further increases, VOUT≤VREF1, the hysteresis current Ihyst is output to the overcurrent protection module 120; the addition of the hysteresis current Ihyst increases the bias current of the seventh transistor M7 to (I6+Ihyst), thereby reducing the mismatch voltage of the sixth transistor M6 and the seventh transistor M7 from Vos1 to Vos2, and further reducing the current limiting point from Ioc1 to Ioc2; at this time, the current flowing through the first resistor R1 is approximately (Is+Ihyst), wherein I6 is ignored, Vs=(Is+Ihyst)*R1≥Vos2, and the overcurrent protection remains on; in this way, the overcurrent hysteresis protection can be realized to reduce power consumption.

[0073] The hysteresis overcurrent protection circuit 100 of the embodiment detects the output voltage VOUT; when the output voltage VOUT is greater than the preset voltage VREF1, no hysteresis current Ihyst is output, and the linear voltage regulator 10 is overcurrent protected based on the first current limiting point Ioc1; when the output voltage VOUT is less than or equal to the preset voltage VREF1, the hysteresis current Ihyst is output, the current limiting point is reduced from the first current limiting point Ioc1 to the second current limiting point Ioc2, and the linear voltage regulator 10 is overcurrent protected based on the second current limiting point Ioc2; wherein, when the linear voltage regulator 10 is short-circuited or overloaded, the hysteresis overcurrent protection circuit 100 of the embodiment is used for overcurrent protection, and the waveform of the output current Iout following the change of the output voltage VOUT is as shown in Figure 11 .

[0074] Embodiment Two

[0075] As shown in Figure 1 , the embodiment provides a linear voltage regulator 10, which includes a hysteresis overcurrent protection circuit 100 and a voltage regulation adjustment circuit 200; as an optional solution, the linear voltage regulator 10 is a low-dropout linear voltage regulator, which can be applied in a high-voltage (for example, 10≤VBAT≤120) scenario.

[0076] The foldback overcurrent protection circuit 100 performs overcurrent foldback protection on the linear regulator 10 (especially the power tube M0 in the voltage regulation circuit 200) based on different current limiting points, so that in the event of a short circuit or overload, the power consumption of the power tube M0 can be quickly reduced based on a smaller current limiting point, thereby avoiding damage to the circuit caused by large current; wherein, the foldback overcurrent protection circuit 100 is implemented by the circuit structure recorded in Example 1, and the relevant content can be found in the above and will not be repeated here.

[0077] The voltage regulation circuit 200 is connected to the foldback overcurrent protection circuit 100, converts the power supply voltage VBAT into the output voltage VOUT, and stabilizes the output based on the comparison between the feedback voltage VFB and the reference voltage VREF2, wherein the feedback voltage VFB is positively correlated with the output voltage VOUT.

[0078] In one example, Figure 1 As shown, the voltage regulating circuit 200 includes a power transistor M0, a feedback module 210 and an error amplifier EA.

[0079] A first end of the power tube M0 is connected to the power supply voltage VBAT, a second end of the power tube M0 is connected to the reference ground via the feedback module 210 and generates an output voltage VOUT, and a control end of the power tube M0 is connected to the output end of the error amplifier EA and the output end of the foldback overcurrent protection circuit 100; wherein, the power tube M0 is a PMOS tube, and the control end refers to the gate end, the first end refers to the source end, and the second end refers to the drain end.

[0080] The feedback module 210 generates a feedback voltage VFB based on the output voltage VOUT. In one embodiment, the feedback module 210 includes a second resistor R2 and a third resistor R3. The first end of the second resistor R2 is connected to the second end of the power transistor M0, and the second end of the second resistor R2 is connected to the reference ground via the third resistor R3. That is, the second end of the second resistor R2 is connected to the first end of the third resistor R3, and the second end of the third resistor R3 is connected to the reference ground. The second end of the second resistor R2 also generates the feedback voltage VFB.

[0081] The first input terminal of the error amplifier EA receives the feedback voltage VFB, the second input terminal of the error amplifier EA receives the reference voltage VREF2, and generates a control signal of the power tube M0 based on the difference between the feedback voltage VFB and the reference voltage VREF2, so as to control the gate voltage of the power tube M0 through feedback adjustment to stabilize the output; wherein, the first input terminal of the error amplifier EA refers to the non-inverting input terminal, and the second input terminal of the error amplifier EA refers to the inverting input terminal.

[0082] Further, such as Figure 1As shown, the voltage regulating circuit 200 further includes a buffer BUF, wherein the buffer BUF is connected between the output terminal of the error amplifier EA and the control terminal of the power tube M0, for reducing the output impedance of the error amplifier EA and improving the driving capability of the power tube M0.

[0083] In summary, the foldback overcurrent protection circuit and linear voltage regulator of the present invention establish an overcurrent foldback protection mechanism by switching the current limit point. This provides overcurrent protection for the linear voltage regulator based on different current limit points, reducing the output current as the output voltage decreases. This allows for rapid power consumption reduction during short circuits or overloads, preventing damage to the circuit caused by high currents. Therefore, the present invention effectively overcomes the shortcomings of the prior art and possesses high industrial value.

[0084] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A foldback overcurrent protection circuit, suitable for a linear voltage regulator, characterized in that: include: a foldback switch module, which compares an output voltage with a preset voltage and outputs a foldback current when the output voltage is less than or equal to the preset voltage, wherein the output voltage is the voltage output by the linear regulator; an overcurrent protection module connected to the foldback switch module, and performing overcurrent protection on the linear regulator based on a first current limiting point when the foldback switch module does not output the foldback current; and reducing the current limiting point from the first current limiting point to a second current limiting point based on the foldback current when the foldback switch module outputs the foldback current, and performing overcurrent protection on the linear regulator based on the second current limiting point.

2. The foldback overcurrent protection circuit according to claim 1, wherein: The foldback switch module includes a first transistor, a second transistor, a first current source, and a second current source. The control end of the first transistor receives the output voltage, the first end of the first transistor is connected to the reference ground, the second end of the first transistor is connected to the control end of the second transistor and connected to the operating voltage via the first current source, the first end of the second transistor is connected to the reference ground via the second current source, and the second end of the second transistor serves as the output end of the foldback switch module.

3. The foldback overcurrent protection circuit according to claim 1, wherein: The foldback switch module includes a first comparator, a third transistor and a third current source, the non-inverting input terminal of the first comparator receives the preset voltage, the inverting input terminal of the first comparator receives the output voltage, the output terminal of the first comparator is connected to the control terminal of the third transistor, the first terminal of the third transistor is connected to the reference ground via the third current source, and the second terminal of the third transistor serves as the output terminal of the foldback switch module.

4. The foldback overcurrent protection circuit according to claim 2 or 3, characterized in that: The foldback switch module further includes a signal shaping unit connected between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor, for performing signal shaping without changing the phase.

5. The foldback overcurrent protection circuit according to claim 4, wherein: The signal shaping unit includes a first in-phase Schmitt trigger; or, the signal shaping unit also includes a first inverter and a second inverter, which are sequentially connected in series between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor.

6. The foldback overcurrent protection circuit according to claim 4, wherein: The signal shaping unit includes a first inverting Schmitt trigger and a third inverter, which are sequentially connected in series between the second end of the first transistor and the control end of the second transistor or between the output end of the first comparator and the control end of the third transistor.

7. The foldback overcurrent protection circuit according to claim 1, wherein: The foldback switch module includes a second comparator, a fourth transistor, a fourth current source and a fourth inverter. The non-inverting input of the second comparator receives the output voltage, the inverting input of the second comparator receives the preset voltage, the output of the second comparator is connected to the input of the fourth inverter, the output of the fourth inverter is connected to the control end of the fourth transistor, the first end of the fourth transistor is connected to the reference ground via the fourth current source, and the second end of the fourth transistor serves as the output end of the foldback switch module.

8. The foldback overcurrent protection circuit according to claim 7, wherein: The foldback switch module further includes a signal shaping unit that replaces the fourth inverter and performs signal shaping with a phase inversion.

9. The foldback overcurrent protection circuit according to claim 8, wherein: The signal shaping unit includes a second inverting Schmitt trigger; or, the signal shaping unit also includes a fifth inverter and a sixth inverter, which are sequentially connected in series between the output end of the second comparator and the control end of the fourth transistor.

10. The foldback overcurrent protection circuit according to claim 8, wherein: The signal shaping unit includes a second in-phase Schmitt trigger and a seventh inverter, which are sequentially connected in series between the output terminal of the second comparator and the control terminal of the fourth transistor.

11. The foldback overcurrent protection circuit according to claim 1, wherein: The overcurrent protection module includes a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a fifth current source, a sixth current source and a first resistor. The control end of the fifth transistor is connected to the control end of the power tube in the linear regulator, the first end of the fifth transistor is connected to the first end of the power tube via the first resistor, the second end of the fifth transistor is connected to the second end of the power tube, the control end of the sixth transistor is connected to the control end of the seventh transistor, the first end of the sixth transistor is connected to the power supply voltage, the second end of the sixth transistor is connected to its control end and to the reference ground via the fifth current source, the first end of the seventh transistor is connected to the first end of the fifth transistor, the second end of the seventh transistor is connected to the control end of the eighth transistor and to the reference ground via the sixth current source, the second end of the seventh transistor is also connected to the output end of the foldback switch module, the first end of the eighth transistor is connected to the power supply voltage, and the second end of the eighth transistor serves as the output end of the foldback overcurrent protection circuit to be connected to the control end of the power tube.

12. A linear voltage regulator, characterized in that: include: The foldback overcurrent protection circuit according to any one of claims 1 to 11; A voltage stabilization adjustment circuit is connected to the foldback overcurrent protection circuit, converts the power supply voltage into an output voltage, and stabilizes the output based on the comparison between the feedback voltage and the reference voltage, wherein the feedback voltage is positively correlated with the output voltage.

13. The linear regulator according to claim 12, wherein: The voltage regulation circuit includes a power tube, a feedback module and an error amplifier, wherein: The first end of the power tube is connected to the power supply voltage, the second end of the power tube is connected to the reference ground via the feedback module and generates the output voltage, and the control end of the power tube is connected to the error amplifier and the output end of the foldback overcurrent protection circuit; The feedback module generates the feedback voltage based on the output voltage; The first input terminal of the error amplifier receives the feedback voltage, the second input terminal of the error amplifier receives the reference voltage, and generates a control signal for the power transistor based on a difference between the feedback voltage and the reference voltage; Alternatively, the voltage stabilizing and adjusting circuit further includes a buffer connected between the output end of the error amplifier and the control end of the power tube.

14. The linear regulator according to claim 13, wherein: The feedback module includes a second resistor and a third resistor, wherein a first end of the second resistor is connected to the second end of the power tube, and a second end of the second resistor is connected to a reference ground via the third resistor to generate the feedback voltage.

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