Overcurrent protection circuit and operational amplifier

Abstract

This application is applicable to the field of operational amplifier technology, and provides an overcurrent protection circuit and an operational amplifier. The overcurrent protection circuit includes a sampling module, a comparison module, and a clamping module. The sampling module is electrically connected to the comparison module and the clamping module respectively, the comparison module is electrically connected to the clamping module, and both the sampling module and the clamping module are used to be electrically connected to the operational amplifier module. When the current flowing through the output power transistor in the operational amplifier module is greater than or equal to the preset current, the sampling module outputs a sampling voltage to the comparison module and the clamping module according to the current flowing through the output power transistor. When the sampling voltage is less than the first voltage, the comparison module outputs a first level signal to the clamping module. The clamping module is used to output a clamping voltage signal to the operational amplifier module according to the first level signal and the sampling voltage, so as to reduce the current flowing through the output power transistor, avoid the operational amplifier module from being in an overcurrent state, and ensure that the output power transistor will not be burned out due to overcurrent.

Description

Technical Field

[0001] This application belongs to the technical field of operational amplifiers, and particularly relates to an overcurrent protection circuit and an operational amplifier. Background Art

[0002] For an operational amplifier, due to its output short-circuit problem, if there is no overcurrent protection, the internal power transistor may be burned out. Therefore, an overcurrent protection circuit needs to be set up. However, in the existing overcurrent protection circuit, once the output current is greater than the current set in the overcurrent protection circuit, the overcurrent protection circuit starts to work. Since there is a trade-off between the set current and the load-carrying capacity and the maximum current that the output power transistor in the operational amplifier module can withstand, in order to drive a heavy load or a full load, the value of the set current is usually relatively large. However, if the set current is set too large, it may cause the output power transistor in the operational amplifier module to be burned out due to overcurrent. Summary of the Invention

[0003] An embodiment of this application provides an overcurrent protection circuit and an operational amplifier, which can solve the problem that the existing overcurrent protection circuit may cause the output power transistor in the operational amplifier module to be burned out due to overcurrent.

[0004] In a first aspect, an embodiment of this application provides an overcurrent protection circuit, including a sampling module, a comparison module, and a clamping module. The sampling module is electrically connected to the comparison module and the clamping module respectively, the comparison module is electrically connected to the clamping module, and both the sampling module and the clamping module are used to be electrically connected to an operational amplifier module;

[0005] When the current flowing through the output power transistor in the operational amplifier module is greater than or equal to a preset current, the sampling module is used to output a sampling voltage to the comparison module and the clamping module according to the current flowing through the output power transistor. The comparison module is used to output a first level signal to the clamping module when the sampling voltage is less than a first voltage. The clamping module is used to output a clamping voltage signal to the operational amplifier module according to the first level signal and the sampling voltage, so as to reduce the current flowing through the output power transistor.

[0006] In a possible implementation manner of the first aspect, the sampling module includes a first resistor and a first switching transistor. The first end of the first resistor is used to be electrically connected to a first power supply. The second end of the first resistor is electrically connected to the source of the first switching transistor, the comparison module, and the clamping module respectively. The gate and the drain of the first switching transistor are both used to be electrically connected to the operational amplifier module.

[0007] In a possible implementation of the first aspect, the comparison module includes a first voltage generation unit and a comparison unit. The first voltage generation unit is electrically connected to the comparison unit and the clamping module respectively. The comparison unit is electrically connected to the sampling module and the clamping module respectively. The first voltage generation unit is used to be electrically connected to a first power supply;

[0008] The first voltage generation unit is configured to output the first voltage to the comparison unit according to the power supply voltage output by the first power supply. The comparison unit is configured to output the first level signal to the clamping module when the sampling voltage is less than the first voltage.

[0009] In a possible implementation of the first aspect, the first voltage generation unit includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first current source, and a second switching transistor. The first end of the second resistor and the source electrode of the second switching transistor are both used to be electrically connected to the first power supply. The second end of the second resistor is electrically connected to the first end of the third resistor. The first end of the fourth resistor is electrically connected to the second end of the third resistor and the drain electrode of the second switching transistor respectively. The second end of the fourth resistor is electrically connected to the first end of the fifth resistor and the comparison unit respectively. The first end of the first current source is electrically connected to the second end of the fifth resistor. The second end of the first current source is grounded. The gate electrode of the second switching transistor is electrically connected to the comparison unit and the clamping module respectively.

[0010] In a possible implementation of the first aspect, the comparison unit includes a comparator. The first input terminal of the comparator is electrically connected to the first voltage generation unit. The second input terminal of the comparator is electrically connected to the sampling module. The output terminal of the comparator is electrically connected to the first voltage generation unit and the clamping module respectively.

[0011] In a possible implementation of the first aspect, the clamping module includes a second voltage generation unit and a clamping unit. The second voltage generation unit is electrically connected to the clamping unit and the comparison module respectively. The clamping unit is electrically connected to the sampling module and the operational amplifier module respectively. Both the second voltage generation unit and the clamping unit are used to be electrically connected to a first power supply;

[0012] The second voltage generation unit is configured to output a second voltage to the clamping unit according to the first level signal and the power supply voltage output by the first power supply. The clamping unit is configured to output the clamping voltage signal to the operational amplifier module when the sampling voltage is less than the second voltage, so as to reduce the current flowing through the output power transistor.

[0013] In a possible implementation of the first aspect, the second voltage generating unit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a second current source, and a third switching transistor. The first end of the sixth resistor and the source electrode of the third switching transistor are both configured to be electrically connected to the first power supply. The second end of the sixth resistor is electrically connected to the first end of the seventh resistor and the drain electrode of the third switching transistor respectively. The first end of the eighth resistor is electrically connected to the second end of the seventh resistor. The second end of the eighth resistor is electrically connected to the first end of the ninth resistor and the clamping unit respectively. The first end of the second current source is electrically connected to the second end of the ninth resistor. The second end of the second current source is grounded. The gate electrode of the third switching transistor is electrically connected to the comparison module.

[0014] In a possible implementation of the first aspect, the clamping unit includes an amplifier, a fourth switching transistor, a fifth switching transistor, and a third current source. The first input terminal of the amplifier is electrically connected to the second voltage generating unit. The second input terminal of the amplifier is electrically connected to the sampling module. The output terminal of the amplifier is electrically connected to the gate electrodes of the fourth switching transistor and the fifth switching transistor respectively. The source electrodes of the fourth switching transistor and the fifth switching transistor are both configured to be electrically connected to the first power supply. The drain electrode of the fourth switching transistor is electrically connected to the first end of the third current source. The drain electrode of the fifth switching transistor is configured to be electrically connected to the operational amplifier module. The second end of the third current source is grounded.

[0015] In a possible implementation of the first aspect, the overcurrent protection circuit further includes a first switching module and a second switching module. The first switching module is electrically connected to the clamping module. The second switching module is electrically connected to the comparison module and the clamping module respectively.

[0016] Both the first switching module and the second switching module are configured to be turned on according to the second level signal output by the clamping module.

[0017] In a second aspect, an embodiment of the present application provides an operational amplifier, which includes an operational amplifier module and the overcurrent protection circuit according to any one of the first aspect. The operational amplifier module is electrically connected to the sampling module and the clamping module in the overcurrent protection circuit respectively.

[0018] The beneficial effects of the embodiments of the present application compared with the prior art are as follows:

[0019] The overcurrent protection circuit provided by the embodiment of the present application includes a sampling module, a comparison module, and a clamping module. When the current flowing through the output power transistor is greater than or equal to the preset current, it can be characterized that the operational amplifier module is in an overcurrent state, and at the same time, it is characterized that the output of the operational amplifier module is short-circuited or in a heavy-load working state. At this time, the sampling module samples the current flowing through the output power transistor and outputs a sampling voltage to the comparison module and the clamping module according to this current. The comparison module receives the sampling voltage and outputs a first level signal to the clamping module when the sampling voltage is less than the first voltage. The clamping module outputs a clamping voltage signal to the operational amplifier module according to the first level signal and the sampling voltage, so as to reduce the current flowing through the output power transistor. It can be seen from this that in the overcurrent protection circuit provided by the embodiment of the present application, when the current flowing through the output power transistor is greater than or equal to the preset current, the comparison module can output a first level signal, so that the clamping module starts to work, clamping the current flowing through the output power transistor to a smaller value, thereby avoiding the operational amplifier module from being in an overcurrent state and ensuring that the output power transistor in the operational amplifier module will not be burned out due to overcurrent. Therefore, even when the operational amplifier module is working under heavy load or full load, the output current will not reach the current value that burns out the power transistor, thereby improving the safety and reliability of the operational amplifier.

[0020] It can be understood that the beneficial effects of the second aspect above can be referred to the relevant descriptions in the first aspect above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 is a schematic block diagram of the overcurrent protection circuit provided by an embodiment of the present application;

[0023] Figure 2 is a schematic circuit connection diagram of the overcurrent protection circuit provided by an embodiment of the present application;

[0024] Figure 3 is a working waveform diagram of the first case of the overcurrent protection circuit provided by an embodiment of the present application;

[0025] Figure 4 is a working waveform diagram of the second case of the overcurrent protection circuit provided by an embodiment of the present application;

[0026] Figure 5 is a working waveform diagram of the third case of the overcurrent protection circuit provided by an embodiment of the present application;

[0027] Figure 6 It is the working waveform diagram of the fourth case of the overcurrent protection circuit provided by an embodiment of the present application.

[0028] In the figure, 10 is the overcurrent protection circuit; 101 is the sampling module; 102 is the comparison module; 1021 is the first voltage generation unit; 1022 is the comparison unit; 103 is the clamping module; 1031 is the second voltage generation unit; 1032 is the clamping unit; 104 is the first switch module; 105 is the second switch module; 20 is the operational amplifier module. Detailed implementation manners

[0029] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system architectures and technologies are presented in order to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from obstructing the description of the present application.

[0030] It should be understood that when used in the specification and appended claims of the present application, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0031] It should also be understood that the term "and / or" as used in the specification and appended claims of the present application refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] As used in the specification and appended claims of the present application, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" according to the context. Similarly, the phrase "if determined" or "if detecting [the described condition or event]" can be interpreted as meaning "once determined", "in response to determining", "once detecting [the described condition or event]", or "in response to detecting [the described condition or event]" according to the context.

[0033] In addition, in the description of the specification and appended claims of the present application, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0034] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of this application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized.

[0035] For an operational amplifier, due to the problem of output short - circuit, if there is no over - current protection, the power transistor inside it may be burned out. Therefore, an over - current protection circuit needs to be set up. However, in the existing over - current protection circuits, once the output current is greater than the set current in the over - current protection circuit, the over - current protection circuit starts to work. Since there is a trade - off between the set current, the load - carrying capacity, and the maximum current that the output power transistor in the operational amplifier module can withstand, in order to drive a heavy load or a full load, the value of the set current is usually relatively large. However, if the set current is set too large, it may cause the output power transistor in the operational amplifier module to be burned out due to over - current.

[0036] Based on the problems existing in the above - mentioned over - current protection circuit, the over - current protection circuit provided by the embodiments of this application includes a sampling module, a comparison module, and a clamping module. When the current flowing through the output power transistor is greater than or equal to the preset current, it can be characterized that the operational amplifier module is in an over - current state, and at the same time, it is characterized that the operational amplifier module has an output short - circuit or is in a heavy - load working state. At this time, the sampling module samples the current flowing through the output power transistor and outputs a sampling voltage to the comparison module and the clamping module according to this current. The comparison module receives the sampling voltage and outputs a first - level signal to the clamping module when the sampling voltage is less than the first voltage. The clamping module outputs a clamping voltage signal to the operational amplifier module according to the first - level signal and the sampling voltage, so as to reduce the current flowing through the output power transistor. It can be seen that for the over - current protection circuit provided by the embodiments of this application, when the current flowing through the output power transistor is greater than or equal to the preset current, the comparison module can output a first - level signal, so that the clamping module starts to work, clamping the current flowing through the output power transistor to a smaller value, thereby avoiding the operational amplifier module from being in an over - current state and ensuring that the output power transistor in the operational amplifier module will not be burned out due to over - current. Therefore, even when the operational amplifier module is working under heavy - load or full - load conditions, the output current will not reach the current value that can burn out the power transistor, thereby improving the safety and reliability of the operational amplifier.

[0037] In order to illustrate the technical solutions described in this application, the following will be described through specific embodiments.

[0038] Figure 1The principle block diagram of an overcurrent protection circuit 10 provided by an embodiment of the present application is shown. Refer to Figure 1 As shown, the overcurrent protection circuit 10 includes a sampling module 101, a comparison module 102, and a clamping module 103. The sampling module 101 is electrically connected to the comparison module 102 and the clamping module 103 respectively. The comparison module 102 is electrically connected to the clamping module 103. Both the sampling module 101 and the clamping module 103 are used to be electrically connected to the operational amplifier module 20. The sampling module 101, the comparison module 102, and the clamping module 103 are all used to be electrically connected to the first power supply.

[0039] Specifically, when the current flowing through the output power transistor (output current Iout) is greater than or equal to the preset current, it can be characterized that the operational amplifier module 20 is in an overcurrent state at this time, and at the same time, it is characterized that the output of the operational amplifier module 20 is short-circuited or in a heavy-load working state. At this time, the sampling module 101 samples the output current Iout and outputs a sampling voltage VS to the comparison module 102 and the clamping module 103 according to the output current Iout. The comparison module 102 receives the sampling voltage VS and outputs a first level signal (for example, the first level signal is a low-level signal) to the clamping module 103 when the sampling voltage VS is less than the first voltage VD. The clamping module 103 outputs a clamping voltage signal to the operational amplifier module 20 according to the first level signal and the sampling voltage VS, so that the output current Iout is reduced. It can be seen from this that in the overcurrent protection circuit 10 provided by the embodiment of the present application, when the output current Iout is greater than or equal to the preset current, the comparison module 102 can output a first level signal, so that the clamping module 103 starts to work, clamps the output current Iout to a smaller value, thereby avoiding the operational amplifier module 20 from being in an overcurrent state, and ensuring that the output power transistor in the operational amplifier module 20 will not be burned out due to overcurrent. Therefore, even when the operational amplifier module 20 is working under heavy load or full load, the output current Iout will not reach the current value that burns out the power transistor, thereby improving the safety and reliability of the operational amplifier.

[0040] It should be noted that when the output current Iout is less than the preset current, it can be characterized that the operational amplifier module 20 is in a non-overcurrent state at this time, and at the same time, it is characterized that the operational amplifier module 20 is in a normal working state. At this time, the comparison module 102 outputs a high-level signal, and the clamping module 103 does not clamp the output current Iout and does not affect the load carrying of the operational amplifier module 20. Therefore, the overcurrent protection circuit 10 provided by the embodiment of the present application can ensure the strong load-carrying ability of the operational amplifier module 20 while ensuring that the output power transistor will not be burned out, thereby improving the reliability of the operational amplifier.

[0041] It should be noted that the operational amplifier module 20 includes PM0, PM1, PM2, PM3, PM4, NM0, NM1, NM2, NM3, Ibias0, R0, R10, and R20. Among them, the gate of PM0 is used to receive inn, that is, the feedback signal FB, and the gate of PM1 is used to receive the reference signal VREF. The sources of PM0 and PM1 are both electrically connected to the second terminal of Ibias0. The drain of PM0 is electrically connected to the drains of PM1, the gates and drains of NM0, the gates and drains of NM1, and the gates of NM2 and NM3 respectively; the sources of NM0, NM1, NM2, NM3, and the second terminal of R0 are all grounded; the first terminal of Ibias0, the sources of PM2, PM3, and PM4 are all used to be electrically connected to the first power supply VCC; the gate of PM2 is electrically connected to the gates of PM3, the drain of PM2, and the drain of NM2 respectively. The drain of PM3 is electrically connected to the drains of NM3, the gate of PM4, the sampling module 101, and the clamping module 103 respectively; the drain of PM4 is electrically connected to the first terminal of R20 and the sampling module 101 respectively. The first terminal of R10 is electrically connected to the second terminal of R20, and the second terminal of R10 is electrically connected to the first terminal of R0.

[0042] It should be noted that NM0, NM1, NM2, and NM3 form a current mirror, and the mirror ratio between any two of them can be set to 1:1. PM2 and PM3 form a current mirror, and the mirror ratio between them can be set to 1:1. Therefore, the current ip0 flowing through PM0 is equal to the current in3 flowing through NM3, and the current ip1 flowing through PM1 is equal to the current ip2 flowing through PM2 and equal to the current ip3 flowing through PM3.

[0043] In an embodiment of the present application, as Figure 2 shown, the sampling module 101 includes a first resistor R1 and a first switching transistor M1. The first terminal of the first resistor R1 is used to be electrically connected to the first power supply. The second terminal of the first resistor R1 is electrically connected to the source of the first switching transistor M1, the comparison module 102, and the clamping module 103 respectively. The gate and the drain of the first switching transistor M1 are both used to be electrically connected to the operational amplifier module 20.

[0044] Specifically, the mirror ratio between the output power transistor PM4 and the first switching transistor M1 in the operational amplifier module 20 is K:1, that is, the current flowing through PM4 is K times the current flowing through the first switching transistor M1. Therefore, the first switching transistor M1 can be used to sample the output current Iout of the operational amplifier module 20 and obtain a sampled current. The sampled current flows through the first resistor R1 to generate a voltage drop, thereby obtaining a sampled voltage VS. Since the obtained sampled voltage VS is the voltage at the second end of the first resistor R1, the sampled voltage VS is VCC - I1*R1, where I1 is the sampled current. Since the sampled current is in a direct proportional relationship with the output current Iout, the larger the output current Iout, the smaller the sampled voltage VS.

[0045] Exemplarily, the designer can select the type of the first switching transistor M1 according to the actual situation, that is, a fully controlled power device such as a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor can be used. For example, the first switching transistor M1 can be selected as a PMOS transistor.

[0046] In an embodiment of the present application, as Figure 2 shown, the comparison module 102 includes a first voltage generation unit 1021 and a comparison unit 1022. The first voltage generation unit 1021 is electrically connected to the comparison unit 1022 and the clamping module 103 respectively. The comparison unit 1022 is electrically connected to the sampling module 101 and the clamping module 103 respectively. The first voltage generation unit 1021 is used to be electrically connected to the first power supply.

[0047] Specifically, the first voltage generation unit 1021 is configured to output a first voltage VD to the comparison unit 1022 according to the power supply voltage VCC output by the first power supply. The comparison unit 1022 receives the first voltage VD and the sampled voltage VS, and compares the first voltage VD and the sampled voltage VS. When the sampled voltage VS is less than the first voltage VD, it indicates that the output current Iout has reached a preset current. At this time, the comparison module 102 outputs a first level signal to enable the clamping module 103 to operate, so as to clamp the output current Iout.

[0048] In an embodiment of the present application, as Figure 2As shown, the first voltage generation unit 1021 includes a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first current source Ibias1, and a second switching transistor M2. The first end of the second resistor R2 and the source of the second switching transistor M2 are both used to be electrically connected to the first power supply. The second end of the second resistor R2 is electrically connected to the first end of the third resistor R3. The first end of the fourth resistor R4 is electrically connected to the second end of the third resistor R3 and the drain of the second switching transistor M2 respectively. The second end of the fourth resistor R4 is electrically connected to the first end of the fifth resistor R5 and the comparison unit 1022 respectively. The first end of the first current source Ibias1 is electrically connected to the second end of the fifth resistor R5. The second end of the first current source Ibias1 is grounded. The gate of the second switching transistor M2 is electrically connected to the comparison unit 1022 and the clamping module 103 respectively.

[0049] Specifically, the first current source Ibias1 is used to provide a stable first current. The second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are used to convert the first current into a first voltage VD. The second switching transistor M2, as a switching device, can be turned on according to the first-level signal output by the comparison unit 1022. When the second switching transistor M2 is in the on state, the second resistor R2 and the third resistor R3 can be short-circuited, so that the first voltage VD transmitted to the comparison unit 1022 is on the high side, and further the comparison unit 1022 is more likely to output the first-level signal according to the first voltage VD and the sampling voltage VS, ensuring that the clamping module 103 can start to work.

[0050] Exemplarily, the preset current can be set according to the values of the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the first current source Ibias1, that is, it can be set as K*Ibias1*(R2 + R3 + R4 + R5) / R1.

[0051] Exemplarily, the designer can select the type of the second switching transistor M2 according to the actual situation, that is, a fully controlled power device such as a metal-oxide field-effect transistor or an insulated-gate bipolar transistor can be used. For example, the second switching transistor M2 can be selected as a PMOS transistor.

[0052] In an embodiment of the present application, as Figure 2 shown, the comparison unit 1022 includes a comparator COMP. The first input terminal of the comparator COMP is electrically connected to the first voltage generation unit 1021. The second input terminal of the comparator COMP is electrically connected to the sampling module 101. The output terminal of the comparator COMP is electrically connected to the first voltage generation unit 1021 and the clamping module 103 respectively.

[0053] Specifically, the negative input terminal of the comparator COMP serves as the first input terminal of the comparator COMP and is used to receive the first voltage VD. The positive input terminal of the comparator COMP serves as the second input terminal of the comparator COMP and is used to receive the sampled voltage VS. The comparator COMP compares the received first voltage VD and the sampled voltage VS. When the sampled voltage VS is greater than the first voltage VD, it indicates that the output current Iout has not reached the preset current, and the OUT0 output by the comparator COMP is a high-level signal. When the first voltage VD is greater than the sampled voltage VS, it indicates that the output current Iout has reached the preset current, and the OUT0 output by the comparator COMP flips to a low-level signal, thereby controlling the clamping module 103 to start working and clamping the output current Iout.

[0054] It should be noted that the comparator COMP can be a hysteretic current-limiting comparator COMP, which has a hysteresis characteristic, that is, when the output state switches, the input signal needs to cross the hysteresis value. Due to the existence of the hysteresis value in the hysteretic comparator COMP, the comparator COMP will not frequently switch states near the threshold value, avoiding the oscillation of the output signal OUT0. At the same time, the hysteresis characteristic makes the comparator COMP more stable under noise interference and reduces the possibility of false triggering.

[0055] It should be noted that only one component composition of the first voltage generation unit 1021 and the comparison unit 1022 is shown in this application, which does not mean that only this one component composition can realize the functions of the first voltage generation unit 1021 and the comparison unit 1022. Other components that can realize this function can also be replaced, and are not limited thereto.

[0056] In an embodiment of the present application, as Figure 2 shown, the clamping module 103 includes a second voltage generation unit 1031 and a clamping unit 1032. The second voltage generation unit 1031 is electrically connected to the clamping unit 1032 and the comparison module 102 respectively. The clamping unit 1032 is electrically connected to the sampling module 101 and the operational amplifier module 20 respectively. Both the second voltage generation unit 1031 and the clamping unit 1032 are used to be electrically connected to the first power supply.

[0057] Specifically, the second voltage generation unit 1031 is used to output a second voltage VE to the clamping unit 1032 according to the first-level signal and the power supply voltage VCC output by the first power supply. The clamping unit 1032 receives the second voltage VE and the sampled voltage VS, and outputs a clamping voltage signal to the operational amplifier module 20 when the sampled voltage VS is less than the second voltage VE, so as to raise the voltage of the PG terminal and reduce the output current Iout flowing through the PM4.

[0058] In an embodiment of the present application, as Figure 2As shown, the second voltage generating unit 1031 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a second current source Ibias2, and a third switching transistor M3. The first end of the sixth resistor R6 and the source of the third switching transistor M3 are both used to be electrically connected to the first power supply. The second end of the sixth resistor R6 is electrically connected to the first end of the seventh resistor R7 and the drain of the third switching transistor M3 respectively. The first end of the eighth resistor R8 is electrically connected to the second end of the seventh resistor R7. The second end of the eighth resistor R8 is electrically connected to the first end of the ninth resistor R9 and the clamping unit 1032 respectively. The first end of the second current source Ibias2 is electrically connected to the second end of the ninth resistor R9. The second end of the second current source Ibias2 is grounded. The gate of the third switching transistor M3 is electrically connected to the comparison module 102.

[0059] Specifically, the second current source Ibias2 is used to provide a stable second current. The sixth resistor R6, the seventh resistor R7, the eighth resistor R8, and the ninth resistor R9 are used to convert the second current into a second voltage VE. The third switching transistor M3 serves as a switching device and can be turned on according to the first-level signal output by the comparator COMP. When the third switching transistor M3 is in the on state, the sixth resistor R6 can be short-circuited, so that the second voltage VE transmitted to the clamping unit 1032 is relatively high, and then the clamping unit 1032 clamps the sampling voltage VS higher, ensuring that the output current Iout is smaller.

[0060] It should be noted that when the third switching transistor M3 is turned on, the second voltage VE is VCC - Ibias2 * (R7 + R8).

[0061] It should be noted that R2 = R6, R3 = R7, R4 = R8, R5 = R9, and Ibias1 = Ibias2. When the OUT0 output by the comparator COMP is at a low level, both the second switching transistor M2 and the third switching transistor M3 are turned on. At this time, the first voltage VD is greater than the second voltage VE.

[0062] Exemplarily, the designer can select the type of the third switching transistor M3 according to the actual situation, that is, a fully controlled power device such as a metal oxide field effect transistor or an insulated gate bipolar transistor can be used. For example, the third switching transistor M3 can be selected as a PMOS transistor.

[0063] In an embodiment of the present application, as Figure 2As shown, the clamping unit 1032 includes an amplifier AMP, a fourth switching transistor M4, a fifth switching transistor M5, and a third current source Ibias3. The first input terminal of the amplifier AMP is electrically connected to the second voltage generating unit 1031, the second input terminal of the amplifier AMP is electrically connected to the sampling module 101, the output terminal of the amplifier AMP is electrically connected to the gates of both the fourth switching transistor M4 and the fifth switching transistor M5. The sources of both the fourth switching transistor M4 and the fifth switching transistor M5 are used to be electrically connected to the first power supply. The drain of the fourth switching transistor M4 is electrically connected to the first terminal of the third current source Ibias3. The drain of the fifth switching transistor M5 is used to be electrically connected to the operational amplifier module 20. The second terminal of the third current source Ibias3 is grounded.

[0064] Specifically, the third current source Ibias3 is used to provide a stable third current. Both the fourth switching transistor M4 and the fifth switching transistor M5 serve as switching devices and are turned on or off according to the amplified signal output by the amplifier AMP. The negative input terminal of the amplifier AMP serves as the first input terminal of the amplifier AMP and is used to receive the second voltage VE. The positive input terminal of the amplifier AMP serves as the second input terminal of the amplifier AMP and is used to receive the sampling voltage VS. The amplifier AMP compares the received second voltage VE and sampling voltage VS. When the sampling voltage VS is greater than the second voltage VE, it indicates that the output current Iout has not yet reached the preset current, and the amplifier AMP outputs a high-level signal to control both the fourth switching transistor M4 and the fifth switching transistor M5 to turn off. When the second voltage VE is greater than the sampling voltage VS, it indicates that the output current Iout has reached the preset current, and the amplifier AMP outputs a flipped low-level signal to control both the fourth switching transistor M4 and the fifth switching transistor M5 to turn on, so as to raise the voltage of the PG terminal and reduce the current flowing through PM4.

[0065] Exemplarily, designers can select the types of the fourth switching transistor M4 and the fifth switching transistor M5 according to the actual situation, that is, all-controlled power devices such as metal-oxide field-effect transistors or insulated-gate bipolar transistors can be used. For example, it can be selected that both the fourth switching transistor M4 and the fifth switching transistor M5 are PMOS transistors.

[0066] It should be noted that since the purpose of the clamping unit 1032 is to clamp the sampling voltage VS to be equal to the second voltage VE, that is, VS = VE. When the second voltage VE becomes higher, the clamping unit 1032 will clamp the sampling voltage VS higher, thereby clamping the output current Iout smaller. Among them, VE = VCC - Ibias2 * (R7 + R8), VS = VCC - I M1 *R1, I M1 is the current flowing through the first switching transistor M1. Combining with K * I M1 = I PM4= Iout. Thus, it can be obtained that the output current Iout can ultimately be clamped to K * Ibias2 * (R7 + R8) / R1.

[0067] It should be noted that only one component composition of the second voltage generation unit 1031 and the clamping unit 1032 is shown in this application, which does not mean that only this one component composition can achieve the functions of the second voltage generation unit 1031 and the clamping unit 1032. Other components that can achieve this function can also be substituted, and are not limited thereto.

[0068] It should be noted that the clamping unit 1032 further includes a first inverter inv1 and a second inverter inv2. The first end of the first inverter inv1 is electrically connected to the drain of the fourth switch tube M4 and the first end of the third current source Ibias3 respectively. The second end of the first inverter inv1 is electrically connected to the first end of the second inverter inv2. The second end of the second inverter inv2 is used to output a second level signal (for example, the second level signal is a low level signal). Both the first inverter inv1 and the second inverter inv2 are used for inverting and filtering to ensure the accuracy of the second level signal output by the clamping unit 1032.

[0069] It should be noted that if the VDS of both the fourth switch tube M4 and the fifth switch tube M5 is not considered, it can be considered that the current ip4 flowing through the fourth switch tube M4 is equal to the current ip5 flowing through the fifth switch tube M5. If ip4 = ip5 < Ibias3, at this time, OUT1 flips to a low level.

[0070] From Figure 2 it can be known that ip5 + ip3 = in3, ip0 = in3 > ip1 = ip2 = ip3, that is, ip5 = in3 - ip3 = ip0 - ip1 = gm * [VREF - VOUT * R0 / (R0 + R1 + R2)] = gm * Δv, where gm is the gain of the operational amplifier module 20, and Δv determines the under-voltage amount of the output voltage due to too heavy a load. Therefore, Ibias3 can be taken as gm * Δv, and an appropriate Δv can be selected according to the size of PM4 and the process. When the output of the operational amplifier module 20 has a short circuit or drives a very heavy load, at this time, ip4 = ip5 > Ibias3 = gm * Δv, and the clamping module 103 operates normally for clamping.

[0071] In an embodiment of the present application, as Figure 2 shown, the overcurrent protection circuit 10 further includes a first switch module 104 and a second switch module 105. The first switch module 104 is electrically connected to the clamping module 103, and the second switch module 105 is electrically connected to the comparison module 102 and the clamping module 103 respectively. Both the first switch module 104 and the second switch module 105 are used to be electrically connected to the first power supply.

[0072] Specifically, both the first switch module 104 and the second switch module 105 receive the second-level signal output by the clamping unit 1032 and conduct according to the second-level signal, so that the comparison module 102 and the clamping module 103 exit the working state and resume the normal working state. Specifically, the first switch module 104 includes a sixth switching transistor M6. The gate of the sixth switching transistor M6 is used to receive the second-level signal. The source of the sixth switching transistor M6 is used to be electrically connected to the first power supply. The drain of the sixth switching transistor M6 is electrically connected to the gates of the fourth switching transistor M4 and the fifth switching transistor M5 respectively. When the sixth switching transistor M6 conducts according to the second-level signal, the gate voltages of the fourth switching transistor M4 and the fifth switching transistor M5 can be pulled up to the power supply voltage VCC, turning off the fourth switching transistor M4 and the fifth switching transistor M5, so that the clamping module 103 exits the working state. The second switch module 105 includes a seventh switching transistor M7. The gate of the seventh switching transistor M7 is used to receive the second-level signal. The source of the seventh switching transistor M7 is used to be electrically connected to the first power supply. The drain of the seventh switching transistor M7 is electrically connected to the gates of the second switching transistor M2 and the third switching transistor M3 respectively. When the seventh switching transistor M7 conducts according to the second-level signal, the gate voltages of the second switching transistor M2 and the third switching transistor M3 can be pulled up to the power supply voltage VCC, turning off the second switching transistor M2 and the third switching transistor M3, so that the comparison module 102 exits the working state.

[0073] Exemplarily, the designer can select the types of the sixth switching transistor M6 and the seventh switching transistor M7 according to the actual situation, that is, all-controllable power devices such as metal-oxide field-effect transistors or insulated-gate bipolar transistors can be used. For example, it can be selected that both the sixth switching transistor M6 and the seventh switching transistor M7 are PMOS transistors.

[0074] It should be noted that according to the above analysis of the circuit, the situations of the operational amplifier module 20 exiting the short circuit after the output is shorted are divided into the following four types:

[0075] (1) The operational amplifier module 20 exits the short circuit, and the output is still very heavily loaded. At this time, both the comparison module 102 and the clamping module 103 in the overcurrent protection circuit 10 are in the working state to clamp the output current Iout. The waveform schematic diagram in this process can be seen in Figure 3 As shown, where the peak value of the output current Iout is K * Ibias1 * (R2 + R3 + R4 + R5) / R1, the clamped value is K * Ibias2 * (R7 + R8 + R9) / R1, and the hysteresis value is K * Ibias1 * (R4 + R5) / R1. Figure 5 The dotted lines from left to right in

[0076] (2) The operational amplifier module 20 exits the short circuit state, and the output is slightly loaded, but this load is less than the current limiting value at which the comparator COMP jumps to a low level and greater than the clamping current ip5 of the clamping module 103. At this time, the clamping current ip5 = ip4 decreases, resulting in the OUT1 output being at a low level. The clamping module 103 does not work, and the threshold of the comparator COMP is pulled back to the maximum. At this time, since the clamping module 103 does not work, the output current Iout (load current) also returns to the normal value. At this time, because the comparator COMP is pulled back to the maximum comparison value, it is not in the overcurrent state, and the overall circuit is in the normal working state. The waveform diagram in this process can be seen in Figure 4 as shown.

[0077] (3) The operational amplifier module 20 exits the short circuit state, and the output is lightly loaded, but this load is less than the clamped current and greater than the low threshold current of the comparator COMP. At this time, ip5 = ip4 < Ibias3, pulling the threshold of the comparator COMP back to the maximum value, and the clamping module 103 itself does not work either. The overall circuit is in the normal working state. The waveform diagram in this process can be seen in Figure 5 as shown.

[0078] (4) The operational amplifier module 20 exits the short circuit state, and the output is very lightly loaded. This load is less than the low threshold current of the comparator COMP. At this time, the clamping module 103 does not work, and the comparator COMP also switches back to the maximum value. The overall circuit is in the normal working state. The waveform diagram in this process can be seen in Figure 6 as shown.

[0079] As can be seen from the above, compared with the existing overcurrent protection circuit, once the current limiting protection is triggered, the circuit stops working. Even if it exits the short circuit state, it still does not work, resulting in the power supply containing the operational amplifier having no load-carrying capacity at all. The overcurrent protection circuit 10 provided in the embodiment of the present application can ensure that after exiting the short circuit, the overall circuit returns to the normal working state, avoiding the problem that once the current limiting protection is triggered, the circuit stops working and still does not work even after exiting the short circuit, improving the performance of the operational amplifier.

[0080] The present application also discloses an operational amplifier, including an operational amplifier module 20 and the above-mentioned overcurrent protection circuit 10. The operational amplifier module 20 is electrically connected to the sampling module 101 and the clamping module 103 in the overcurrent protection circuit 10 respectively. By adopting the above-mentioned overcurrent protection circuit 10, the operational amplifier can clamp the output current within a safe range when the output current is greater than or equal to the preset current, avoid the operational amplifier module 20 being in the overcurrent state, and ensure that the output power transistor in the operational amplifier module 20 will not be burned out due to overcurrent, improving the safety and reliability of the operational amplifier.

[0081] Since the processing and functions implemented by the operational amplifier in this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned overcurrent protection circuit, for the details not described in the description of this embodiment, reference can be made to the relevant descriptions in the aforementioned embodiments and will not be elaborated herein.

[0082] The above-described embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application and should all be included within the protection scope of the present application.

Claims

1. An overcurrent protection circuit, characterized in that, It includes a sampling module, a comparison module and a clamping module. The sampling module is electrically connected to the comparison module and the clamping module respectively. The comparison module is electrically connected to the clamping module. Both the sampling module and the clamping module are used to be electrically connected to an operational amplifier module; When the current flowing through the output power transistor in the operational amplifier module is greater than or equal to a preset current, the sampling module is used to output a sampling voltage to the comparison module and the clamping module according to the current flowing through the output power transistor. The comparison module is used to output a first level signal to the clamping module when the sampling voltage is less than a first voltage. The clamping module is used to output a clamping voltage signal to the operational amplifier module according to the first level signal and the sampling voltage, so as to reduce the current flowing through the output power transistor; The clamping module includes a second voltage generating unit and a clamping unit. The second voltage generating unit is electrically connected to the clamping unit and the comparison module respectively. The clamping unit is electrically connected to the sampling module and the operational amplifier module respectively. Both the second voltage generating unit and the clamping unit are used to be electrically connected to a first power supply; The second voltage generating unit is used to output a second voltage to the clamping unit according to the first level signal and the power supply voltage output by the first power supply. The clamping unit is used to output the clamping voltage signal to the operational amplifier module when the sampling voltage is less than the second voltage, so as to reduce the current flowing through the output power transistor.

2. The overcurrent protection circuit according to claim 1, wherein The sampling module includes a first resistor and a first switching transistor. The first end of the first resistor is used to be electrically connected to a first power supply. The second end of the first resistor is electrically connected to the source of the first switching transistor, the comparison module and the clamping module respectively. The gate and the drain of the first switching transistor are both used to be electrically connected to the operational amplifier module.

3. The overcurrent protection circuit according to claim 1, characterized in that, The comparison module includes a first voltage generating unit and a comparison unit. The first voltage generating unit is electrically connected to the comparison unit and the clamping module respectively. The comparison unit is electrically connected to the sampling module and the clamping module respectively. The first voltage generating unit is used to be electrically connected to a first power supply; The first voltage generating unit is used to output the first voltage to the comparison unit according to the power supply voltage output by the first power supply. The comparison unit is used to output the first level signal to the clamping module when the sampling voltage is less than the first voltage.

4. The overcurrent protection circuit according to claim 3, wherein The first voltage generating unit includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first current source, and a second switching transistor. The first end of the second resistor and the source electrode of the second switching transistor are both used for electrically connecting to the first power supply. The second end of the second resistor is electrically connected to the first end of the third resistor. The first end of the fourth resistor is respectively electrically connected to the second end of the third resistor and the drain electrode of the second switching transistor. The second end of the fourth resistor is respectively electrically connected to the first end of the fifth resistor and the comparison unit. The first end of the first current source is electrically connected to the second end of the fifth resistor. The second end of the first current source is grounded. The gate electrode of the second switching transistor is respectively electrically connected to the comparison unit and the clamping module.

5. The overcurrent protection circuit according to claim 3, characterized in that, The comparison unit includes a comparator. The first input terminal of the comparator is electrically connected to the first voltage generating unit. The second input terminal of the comparator is electrically connected to the sampling module. The output terminal of the comparator is respectively electrically connected to the first voltage generating unit and the clamping module.

6. The overcurrent protection circuit according to claim 1, characterized in that, The second voltage generating unit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a second current source, and a third switching transistor. The first end of the sixth resistor and the source electrode of the third switching transistor are both used for electrically connecting to the first power supply. The second end of the sixth resistor is respectively electrically connected to the first end of the seventh resistor and the drain electrode of the third switching transistor. The first end of the eighth resistor is electrically connected to the second end of the seventh resistor. The second end of the eighth resistor is respectively electrically connected to the first end of the ninth resistor and the clamping unit. The first end of the second current source is electrically connected to the second end of the ninth resistor. The second end of the second current source is grounded. The gate electrode of the third switching transistor is electrically connected to the comparison module.

7. The overcurrent protection circuit according to claim 1, wherein The clamping unit includes an amplifier, a fourth switching transistor, a fifth switching transistor, and a third current source. The first input terminal of the amplifier is electrically connected to the second voltage generating unit. The second input terminal of the amplifier is electrically connected to the sampling module. The output terminal of the amplifier is respectively electrically connected to the gate electrode of the fourth switching transistor and the gate electrode of the fifth switching transistor. The source electrodes of the fourth switching transistor and the fifth switching transistor are both used for electrically connecting to the first power supply. The drain electrode of the fourth switching transistor is electrically connected to the first end of the third current source. The drain electrode of the fifth switching transistor is used for electrically connecting to the operational amplifier module. The second end of the third current source is grounded.

8. The overcurrent protection circuit according to any one of claims 1-7, characterized in that, The overcurrent protection circuit further includes a first switching module and a second switching module. The first switching module is electrically connected to the clamping module. The second switching module is respectively electrically connected to the comparison module and the clamping module. Both the first switching module and the second switching module are used for conducting according to the second level signal output by the clamping module.

9. An operational amplifier, characterized in that, It includes an operational amplifier module and the overcurrent protection circuit according to any one of claims 1-8. The operational amplifier module is respectively electrically connected to the sampling module and the clamping module in the overcurrent protection circuit.

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