Overcurrent protection circuit and operational amplifier

Abstract

The invention is suitable for the technical field of operational amplifiers, and provides an overcurrent protection circuit and an operational amplifier. The overcurrent protection circuit comprises a sampling module, a comparison module and a clamping module, the sampling module is electrically connected with the comparison module and the clamping module, the comparison module is electrically connected with the clamping module, and the sampling module and the clamping module are both used for being electrically connected with the operational amplifier module. When current flowing through an output power tube in the operational amplifier module is larger than or equal to preset current, the sampling module outputs sampling voltage to the comparison module and the clamping module according to the current flowing through the output power tube, and the comparison module outputs a first level signal to the clamping module when the sampling voltage is smaller than first voltage. And the clamping module is used for outputting a clamping voltage signal to the operational amplifier module according to the first level signal and the sampling voltage, so that the current flowing through the output power tube is reduced, the operational amplifier module is prevented from being in an overcurrent state, and the output power tube is ensured not to be burnt out due to overcurrent.

Description

Technical Field

[0001] The present application belongs to the technical field of operational amplifiers, and in particular, relates to an overcurrent protection circuit and an operational amplifier. Background Art

[0002] For operational amplifiers, due to the output short circuit problem, if there is no overcurrent protection, the internal power tube may be burned out, so an overcurrent protection circuit needs to be set. 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 compromise between the set current and the load capacity and the maximum current that the output power tube in the operational amplifier module can withstand, in order to carry heavy loads or full loads, the set current value is usually larger. However, if the set current is set too large, the output power tube in the operational amplifier module may burn out due to overcurrent. Summary of the invention

[0003] The embodiments of the present application provide an overcurrent protection circuit and an operational amplifier, which can solve the problem that the existing overcurrent protection circuit may cause the output power tube in the operational amplifier module to burn out due to overcurrent.

[0004] In a first aspect, an embodiment of the present application provides an overcurrent protection circuit, comprising a sampling module, a comparison module and a clamping module, wherein 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 the sampling module and the clamping module are both used to be electrically connected to an operational amplifier module; When the current flowing through the output power tube 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 tube, 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, and 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 that the current flowing through the output power tube is reduced.

[0005] In a possible implementation of the first aspect, the sampling module includes a first resistor and a first switching tube, 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 respectively electrically connected to a source of the first switching tube, the comparison module and the clamping module, and the gate of the first switching tube and the drain of the first switching tube are both used to be electrically connected to the operational amplifier module. In a possible implementation manner of the first aspect, 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, and 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 comparing unit according to the power supply voltage output by the first power supply, and the comparing unit is used to output the first level signal to the clamping module when the sampling voltage is less than the first voltage. In a possible implementation of the first aspect, 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 switch tube, the first end of the second resistor and the source of the second switch tube 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 respectively electrically connected to the second end of the third resistor and the drain of the second switch tube, 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, and the gate of the second switch tube is respectively electrically connected to the comparison unit and the clamping module. In a possible implementation of the first aspect, the comparison unit includes a comparator, a first input end of the comparator is electrically connected to the first voltage generating unit, a second input end of the comparator is electrically connected to the sampling module, and an output end of the comparator is electrically connected to the first voltage generating unit and the clamping module, respectively. In a possible implementation manner of the first aspect, 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, and the second voltage generating unit and the clamping unit are both 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 tube. 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 switch tube, the first end of the sixth resistor and the source of the third switch tube are both used to be electrically connected 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 of the third switch tube, 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, and the gate of the third switch tube is electrically connected to the comparison module. In a possible implementation of the first aspect, the clamping unit includes an amplifier, a fourth switch tube, a fifth switch tube and a third current source, the first input end of the amplifier is electrically connected to the second voltage generating unit, the second input end of the amplifier is electrically connected to the sampling module, the output end of the amplifier is electrically connected to the gate of the fourth switch tube and the gate of the fifth switch tube respectively, the source of the fourth switch tube and the source of the fifth switch tube are both used to be electrically connected to the first power supply, the drain of the fourth switch tube is electrically connected to the first end of the third current source, the drain of the fifth switch tube is used to be electrically connected to the operational amplifier module, and the second end of the third current source is grounded. In a possible implementation manner of the first aspect, the overcurrent protection circuit further includes a first switch module and a second switch module, the first switch module is electrically connected to the clamp module, and the second switch module is electrically connected to the comparison module and the clamp module respectively; The first switch module and the second switch module are both used for being turned on according to the second level signal output by the clamp module. In a second aspect, an embodiment of the present application provides an operational amplifier, comprising an operational amplifier module and the overcurrent protection circuit described in any one of the first aspects, wherein the operational amplifier module is electrically connected to a sampling module and a clamping module in the overcurrent protection circuit, respectively.

[0006] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: 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 tube 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 can be characterized that the output of the operational amplifier module is short-circuited or in an overloaded working state. At this time, the sampling module samples the current flowing through the output power tube, and outputs a sampling voltage to the comparison module and the clamping module according to the 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 that the current flowing through the output power tube is reduced. It can be seen from this that the overcurrent protection circuit provided by the embodiment of the present application, when the current flowing through the output power tube 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, and the current flowing through the output power tube is clamped to be smaller, thereby avoiding the operational amplifier module from being in an overcurrent state, and ensuring that the output power tube in the operational amplifier module will not burn out due to overcurrent. Therefore, even if the operational amplifier module is under heavy load or full load, the output current will not reach the current value that burns the power tube, thereby improving the safety and reliability of the operational amplifier.

[0007] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0009] Figure 1 is a principle block diagram of an overcurrent protection circuit provided in an embodiment of the present application; Figure 2 is a circuit connection diagram of an overcurrent protection circuit provided in an embodiment of the present application; Figure 3 This is a working waveform diagram of the first case of the overcurrent protection circuit provided by an embodiment of the present application; Figure 4 is a working waveform diagram of the second situation of the overcurrent protection circuit provided by an embodiment of the present application; Figure 5 is a working waveform diagram of the third situation of the overcurrent protection circuit provided by an embodiment of the present application; Figure 6 This is a working waveform diagram of the fourth case of the overcurrent protection circuit provided in one embodiment of the present application.

[0010] In the figure, 10, overcurrent protection circuit; 101, sampling module; 102, comparison module; 1021, first voltage generating unit; 1022, comparison unit; 103, clamping module; 1031, second voltage generating unit; 1032, clamping unit; 104, first switch module; 105, second switch module; 20, operational amplifier module. DETAILED DESCRIPTION

[0011] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may 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 prevent unnecessary details from obstructing the description of the present application.

[0012] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0013] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0014] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0015] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0016] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0017] For operational amplifiers, due to the output short circuit problem, if there is no overcurrent protection, the internal power tube may be burned out, so an overcurrent protection circuit needs to be set. 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 compromise between the set current and the load capacity and the maximum current that the output power tube in the operational amplifier module can withstand, in order to carry heavy loads or full loads, the set current value is usually larger. However, if the set current is set too large, the output power tube in the operational amplifier module may burn out due to overcurrent.

[0018] Based on the problems existing in the above-mentioned overcurrent protection circuit, the overcurrent protection circuit provided in 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 tube 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 can be characterized that the output of the operational amplifier module is short-circuited or in an overloaded working state. At this time, the sampling module samples the current flowing through the output power tube, and outputs a sampling voltage to the comparison module and the clamping module according to the 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 that the current flowing through the output power tube is reduced. It can be seen from this that the overcurrent protection circuit provided in the embodiment of the present application, when the current flowing through the output power tube 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, and the current flowing through the output power tube is clamped to be smaller, thereby avoiding the operational amplifier module from being in an overcurrent state, and ensuring that the output power tube in the operational amplifier module will not be burned due to overcurrent. Therefore, even if the operational amplifier module is under heavy load or full load, the output current will not reach the current value that burns the power tube, thereby improving the safety and reliability of the operational amplifier.

[0019] In order to illustrate the technical solution described in this application, a specific embodiment is provided below for illustration.

[0020] Figure 1FIG. 1 shows a principle block diagram of an overcurrent protection circuit 10 provided in an embodiment of the present application. 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, and the comparison module 102 is electrically connected to the clamping module 103. The sampling module 101 and the clamping module 103 are both 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.

[0021] Specifically, when the current (output current Iout) flowing through the output power tube is greater than or equal to the preset current, it can be characterized that the operational amplifier module 20 is in an overcurrent state, and at the same time, it can be 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 that, in the overcurrent protection circuit 10 provided in 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, and the output current Iout is clamped to a smaller level, thereby preventing the operational amplifier module 20 from being in an overcurrent state, and ensuring that the output power tube in the operational amplifier module 20 will not be burned due to overcurrent. Therefore, even if the operational amplifier module 20 is under heavy load or full load, the output current Iout will not reach the current value that burns the power tube, thereby improving the safety and reliability of the operational amplifier.

[0022] It should be noted that when the output current Iout is less than the preset current, it can be indicated that the operational amplifier module 20 is in a non-overcurrent state, and at the same time, it can be indicated 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, which does not affect the load of the operational amplifier module 20. Therefore, the overcurrent protection circuit 10 provided in the embodiment of the present application can ensure that the output power tube will not be burned while ensuring that the operational amplifier module 20 has a strong load capacity, thereby improving the reliability of the operational amplifier.

[0023] 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, the gate of PM1 is used to receive the reference signal VREF, the source of PM0 and the source of PM1 are both electrically connected to the second end of Ibias0, the drain of PM0 is respectively electrically connected to the drain of PM1, the gate and drain of NM0, the gate and drain of NM1, the gate of NM2 and the gate of NM3; the source of NM0, the source of NM1, the source of NM2, the source of NM3 and the second end of R0 are all grounded; the first end of Ibias0, The source of PM2, the source of PM3 and the source of PM4 are all used to be electrically connected to the first power supply VCC; the gate of PM2 is electrically connected to the gate of PM3, the drain of PM2 and the drain of NM2, respectively; the drain of PM3 is electrically connected to the drain 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 end of R20 and the sampling module 101, respectively, the first end of R10 is electrically connected to the second end of R20, and the second end of R10 is electrically connected to the first end of R0.

[0024] 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 the two can be set to 1:1. Therefore, the current ip0 flowing through PM0 is equal to the current in3 flowing through NM3, the current ip1 flowing through PM1 is equal to the current ip2 flowing through PM2, and the current ip3 flowing through PM3.

[0025] In one embodiment of the present application, Figure 2 As shown, the sampling module 101 includes a first resistor R1 and a first switch tube M1. The first end of the first resistor R1 is used to be electrically connected to the first power supply, and the second end of the first resistor R1 is electrically connected to the source of the first switch tube M1, the comparison module 102 and the clamping module 103 respectively. The gate of the first switch tube M1 and the drain of the first switch tube M1 are both used to be electrically connected to the operational amplifier module 20.

[0026] Specifically, the mirror ratio between the output power tube PM4 and the first switch tube 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 switch tube M1. Therefore, the first switch tube M1 can be used to sample the output current Iout of the operational amplifier module 20 and obtain the sampled current. The sampled current flows through the first resistor R1 to generate a voltage drop, thereby obtaining the 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 direct proportion to the output current Iout, the larger the output current Iout, the smaller the sampled voltage VS.

[0027] For example, designers can select the type of the first switch tube M1 according to actual conditions, that is, they can use fully controlled power devices such as metal oxide field effect transistors or insulated gate bipolar transistors. For example, the first switch tube M1 can be selected as a PMOS tube.

[0028] In one embodiment of the present application, Figure 2 As shown, the comparison module 102 includes a first voltage generating unit 1021 and a comparison unit 1022. The first voltage generating 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 generating unit 1021 is used to be electrically connected to the first power supply.

[0029] Specifically, the first voltage generating unit 1021 is used to output the 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 sampling voltage VS, and compares the first voltage VD with the sampling voltage VS. When the sampling voltage VS is less than the first voltage VD, it indicates that the output current Iout has reached the preset current. At this time, the comparison module 102 outputs a first level signal to enable the clamping module 103 to work, thereby clamping the output current Iout.

[0030] In one embodiment of the present application, Figure 2As shown, the first voltage generating 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 switch tube M2. The first end of the second resistor R2 and the source of the second switch tube 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 switch tube 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 switch tube M2 is electrically connected to the comparison unit 1022 and the clamping module 103, respectively.

[0031] Specifically, the first current source Ibias1 is used to provide a stable first current, and 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 switch tube M2, as a switch device, can be turned on according to the first level signal output by the comparison unit 1022. When the second switch tube 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 higher, and then the comparison unit 1022 is easier 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 working.

[0032] 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, can be set to K*Ibias1*(R2+R3+R4+R5) / R1.

[0033] For example, the designer can select the type of the second switch tube 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 switch tube M2 can be selected as a PMOS tube.

[0034] In one embodiment of the present application, Figure 2 As shown, the comparison unit 1022 includes a comparator COMP, a first input terminal of the comparator COMP is electrically connected to the first voltage generating unit 1021, a second input terminal of the comparator COMP is electrically connected to the sampling module 101, and an output terminal of the comparator COMP is electrically connected to the first voltage generating unit 1021 and the clamping module 103 respectively.

[0035] 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 sampling voltage VS. The comparator COMP compares the received first voltage VD with the sampling voltage VS. When the sampling voltage VS is greater than the first voltage VD, it indicates that the output current Iout has not reached the preset current, and OUT0 output by the comparator COMP is a high-level signal. When the first voltage VD is greater than the sampling voltage VS, it indicates that the output current Iout has reached the preset current, and OUT0 output by the comparator COMP is flipped to a low-level signal, thereby controlling the clamping module 103 to start working and clamp the output current Iout.

[0036] It should be noted that the comparator COMP can be a hysteresis current limiting comparator COMP with a hysteresis characteristic, that is, when the output state is switched, the input signal needs to cross the hysteresis value. Since the hysteresis comparator COMP has a hysteresis value, the comparator COMP will not switch states frequently near the threshold, thereby avoiding oscillation of the output signal OUT0. At the same time, the hysteresis characteristic makes the comparator COMP more stable under noise interference, reducing the possibility of false triggering.

[0037] It should be noted that, the present application only shows one component composition as the first voltage generating unit 1021 and the comparing unit 1022, which does not mean that only this component composition can realize the functions of the first voltage generating unit 1021 and the comparing unit 1022. Other components that can realize the functions can also be replaced, and are not limited to this.

[0038] In one embodiment of the present application, Figure 2 As shown, the clamping module 103 includes a second voltage generating unit 1031 and a clamping unit 1032. The second voltage generating 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. The second voltage generating unit 1031 and the clamping unit 1032 are both used to be electrically connected to the first power supply.

[0039] Specifically, the second voltage generating unit 1031 is used to output the 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 sampling voltage VS, and outputs a clamping voltage signal to the operational amplifier module 20 when the sampling voltage VS is less than the second voltage VE, so as to increase the voltage at the PG terminal and reduce the output current Iout flowing through PM4.

[0040] In one embodiment of the present application, 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 switch tube M3. The first end of the sixth resistor R6 and the source of the third switch tube M3 are both used to be electrically connected to the first power supply, the second end of the sixth resistor R6 is respectively electrically connected to the first end of the seventh resistor R7 and the drain of the third switch tube M3, 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 respectively electrically connected to the first end of the ninth resistor R9 and the clamping unit 1032, 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, and the gate of the third switch tube M3 is electrically connected to the comparison module 102.

[0041] Specifically, the second current source Ibias2 is used to provide a stable second current, and 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 switch tube M3, as a switch device, can be turned on according to the first level signal output by the comparator COMP. When the third switch tube 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 higher, and then the clamping unit 1032 clamps the sampling voltage VS higher, ensuring that the output current Iout is smaller.

[0042] It should be noted that when the third switch tube M3 is turned on, the second voltage VE is VCC-Ibias2*(R7+R8).

[0043] It should be noted that R2=R6, R3=R7, R4=R8, R5=R9, and Ibias1=Ibias2. When OUT0 output by the comparator COMP is at a low level, the second switch tube M2 and the third switch tube M3 are both turned on, and at this time the first voltage VD is greater than the second voltage VE.

[0044] For example, the designer can select the type of the third switch tube 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 switch tube M3 can be selected as a PMOS tube.

[0045] In one embodiment of the present application, Figure 2As shown, the clamping unit 1032 includes an amplifier AMP, a fourth switch tube M4, a fifth switch tube 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 gate of the fourth switch tube M4 and the gate of the fifth switch tube M5 respectively, the source of the fourth switch tube M4 and the source of the fifth switch tube M5 are both used to be electrically connected to the first power supply, the drain of the fourth switch tube M4 is electrically connected to the first end of the third current source Ibias3, the drain of the fifth switch tube M5 is used to be electrically connected to the operational amplifier module 20, and the second end of the third current source Ibias3 is grounded.

[0046] Specifically, the third current source Ibias3 is used to provide a stable third current, and the fourth switch tube M4 and the fifth switch tube M5 are both used as switch devices, and are both turned on or off according to the amplified signal output by the amplifier AMP. The negative input terminal of the amplifier AMP is used as the first input terminal of the amplifier AMP to receive the second voltage VE, and the positive input terminal of the amplifier AMP is used as the second input terminal of the amplifier AMP to receive the sampling voltage VS. The amplifier AMP compares the received second voltage VE with the sampling voltage VS. When the sampling voltage VS is greater than the second voltage VE, it indicates that the output current Iout has not reached the preset current. The amplifier AMP outputs a high-level signal to control the fourth switch tube M4 and the fifth switch tube M5 to be turned 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. The amplifier AMP outputs a flipped low-level signal to control the fourth switch tube M4 and the fifth switch tube M5 to be turned on, so as to pull up the voltage at the PG terminal and reduce the current flowing through PM4.

[0047] For example, the designer can select the type of the fourth switch tube M4 and the fifth switch tube M5 according to the actual situation, that is, both can use fully controlled power devices such as metal oxide field effect transistors or insulated gate bipolar transistors. For example, the fourth switch tube M4 and the fifth switch tube M5 can be selected as PMOS tubes.

[0048] 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 to be smaller. Wherein, VE=VCC- Ibias2* (R7+R8), VS=VCC-I M1 *R1,I M1 is the current flowing through the first switch tube M1. Combined with K*I M1 =I PM4=Iout. Therefore, the output current Iout can be clamped to K*Ibias2*(R7+R8) / R1.

[0049] It should be noted that, this application only shows one component composition as the second voltage generating unit 1031 and the clamping unit 1032, which does not mean that only this component composition can realize the functions of the second voltage generating unit 1031 and the clamping unit 1032. Other components that can realize the functions can also be replaced, without limitation.

[0050] 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, and 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). The first inverter inv1 and the second inverter inv2 are both used for inversion and filtering to ensure the accuracy of the second level signal output by the clamping unit 1032.

[0051] It should be noted that if the fourth switch tube M4 and the fifth switch tube M5 do not consider VDS, 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.

[0052] Depend on Figure 2 It can be seen 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 amount of undervoltage of the output voltage due to heavy load. Therefore, Ibias3 can be gm*Δv, and an appropriate Δv is selected according to the size of PM4 and the process. When the operational amplifier module 20 has an output short circuit or carries a heavy load, ip4=ip5>Ibias3=gm*Δv, and the clamping module 103 works normally.

[0053] In one embodiment of the present application, Figure 2 As shown, the overcurrent protection circuit 10 also includes a first switch module 104 and a second switch module 105. The first switch module 104 is electrically connected to the clamp module 103, and the second switch module 105 is electrically connected to the comparison module 102 and the clamp module 103 respectively. The first switch module 104 and the second switch module 105 are both used to be electrically connected to the first power supply.

[0054] Specifically, the first switch module 104 and the second switch module 105 both receive the second level signal output by the clamp unit 1032, and are turned on according to the second level signal, so that the comparison module 102 and the clamp module 103 exit the working state and resume the normal working state. Specifically, the first switch module 104 includes a sixth switch tube M6, the gate of the sixth switch tube M6 is used to receive the second level signal, the source of the sixth switch tube M6 is used to be electrically connected to the first power supply, and the drain of the sixth switch tube M6 is electrically connected to the gate of the fourth switch tube M4 and the gate of the fifth switch tube M5 respectively. When the sixth switch tube M6 is turned on according to the second level signal, the gate voltages of the fourth switch tube M4 and the fifth switch tube M5 can be pulled up to the power supply voltage VCC, so that the fourth switch tube M4 and the fifth switch tube M5 are turned off, so that the clamp module 103 exits the working state. The second switch module 105 includes a seventh switch tube M7, the gate of the seventh switch tube M7 is used to receive the second level signal, the source of the seventh switch tube M7 is used to be electrically connected to the first power supply, and the drain of the seventh switch tube M7 is electrically connected to the gate of the second switch tube M2 and the gate of the third switch tube M3 respectively. When the seventh switch tube M7 is turned on according to the second level signal, the gate voltages of the second switch tube M2 and the third switch tube M3 can be pulled up to the power supply voltage VCC, so that the second switch tube M2 and the third switch tube M3 are turned off, so that the comparison module 102 exits the working state.

[0055] For example, the designer can select the type of the sixth switch tube M6 and the seventh switch tube M7 according to the actual situation, that is, both can use fully controlled power devices such as metal oxide field effect transistors or insulated gate bipolar transistors. For example, the sixth switch tube M6 and the seventh switch tube M7 can be selected as PMOS tubes.

[0056] It should be noted that, according to the above analysis of the circuit, the situations in which the output of the operational amplifier module 20 is short-circuited and then exits the short-circuit are divided into the following four types: (1) The operational amplifier module 20 exits the short circuit, and the output is still heavily loaded. At this time, the comparison module 102 and the clamping module 103 in the overcurrent protection circuit 10 are both in working state, clamping the output current Iout. The waveform diagram of this process can be seen in Figure 3 As shown, the peak value of the output current Iout is K* Ibias1*(R2+R3+R4+R5) / R1, the value after clamping is K* Ibias2*(R7+R8+R9) / R1, and the hysteresis value is K* Ibias1*(R4+R5) / R1. Figure 5 The dashed lines from left to right in the figure represent short circuit, clamping and exiting short circuit respectively.

[0057] (2) The operational amplifier module 20 exits the short circuit, and the output is a slightly heavy load, 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 not working, and the threshold of the comparator COMP being 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 also not in an overcurrent state, and the overall circuit is in a normal working state. The waveform schematic diagram in this process can be seen in Figure 4 as shown.

[0058] (3) The operational amplifier module 20 exits the short circuit, and the output is a light load, 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 a normal working state. The waveform schematic diagram in this process can be seen in Figure 5 as shown.

[0059] (4) The operational amplifier module 20 exits the short circuit, and the output is a very light load, which 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 a normal working state. The waveform schematic diagram in this process can be seen in Figure 6 as shown.

[0060] 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, 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 if it exits the short circuit, and improving the performance of the operational amplifier.

[0061] 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 an 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.

[0062] Since the processing and functions implemented by the operational amplifier in this embodiment basically correspond to the embodiments, principles and examples of the aforementioned overcurrent protection circuit, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0063] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in 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, wherein 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 the sampling module and the clamping module are both used to be electrically connected to the operational amplifier module; When the current flowing through the output power tube 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 tube, 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, and 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 that the current flowing through the output power tube is reduced.

2. The overcurrent protection circuit according to claim 1, characterized in that: The sampling module includes a first resistor and a first switch tube, 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 respectively electrically connected to the source of the first switch tube, the comparison module and the clamping module, and the gate of the first switch tube and the drain of the first switch tube 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, and 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 comparing unit according to the power supply voltage output by the first power supply, and the comparing 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, characterized in that: 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 switch tube, the first end of the second resistor and the source of the second switch tube 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 respectively electrically connected to the second end of the third resistor and the drain of the second switch tube, 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, and the gate of the second switch tube 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, a first input end of the comparator is electrically connected to the first voltage generating unit, a second input end of the comparator is electrically connected to the sampling module, and an output end of the comparator is electrically connected to the first voltage generating unit and the clamping module respectively.

6. The overcurrent protection circuit according to claim 1, characterized in that: The clamping module comprises 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, and the second voltage generating unit and the clamping unit are both used to be electrically connected to the 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 tube.

7. The overcurrent protection circuit according to claim 6, 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 switch tube. The first end of the sixth resistor and the source of the third switch tube are both used to be electrically connected 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 of the third switch tube, 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, and the gate of the third switch tube is electrically connected to the comparison module.

8. The overcurrent protection circuit according to claim 6, characterized in that: The clamping unit includes an amplifier, a fourth switch tube, a fifth switch tube and a third current source. The first input end of the amplifier is electrically connected to the second voltage generating unit, the second input end of the amplifier is electrically connected to the sampling module, the output end of the amplifier is electrically connected to the gate of the fourth switch tube and the gate of the fifth switch tube respectively, the source of the fourth switch tube and the source of the fifth switch tube are both used to be electrically connected to the first power supply, the drain of the fourth switch tube is electrically connected to the first end of the third current source, the drain of the fifth switch tube is used to be electrically connected to the operational amplifier module, and the second end of the third current source is grounded.

9. The overcurrent protection circuit according to any one of claims 1 to 8, characterized in that: The overcurrent protection circuit further includes a first switch module and a second switch module, the first switch module is electrically connected to the clamp module, and the second switch module is electrically connected to the comparison module and the clamp module respectively; The first switch module and the second switch module are both used for being turned on according to the second level signal output by the clamp module.

10. An operational amplifier, characterized in that: It comprises an operational amplifier module and the overcurrent protection circuit according to any one of claims 1 to 9, wherein the operational amplifier module is electrically connected to a sampling module and a clamping module in the overcurrent protection circuit respectively.

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