Current protection circuit and power supply protection system

Abstract

The present application provides a current protection circuit and a power supply protection system, wherein the power supply protection circuit includes: a first power tube, a first current limiting loop, and a second current limiting loop, wherein the drain and source of the first power tube are respectively connected to the power supply input terminal and the load output terminal, the gate of the first power tube is connected to the bias voltage, and the first current limiting loop and the second current limiting loop are respectively connected to the gate of the first power tube. The second current limiting loop in the above scheme can accurately control the current, while the first current limiting loop can respond quickly. The combination of the first current limiting loop and the second current limiting loop enables the above current protection circuit to take into account both current protection speed and accuracy, thereby improving the current protection performance of the above current protection circuit.

Description

Technical Field

[0001] The present application relates to the field of current protection technology, and in particular to a current protection circuit and a power supply protection system. Background Art

[0002] Circuit protection is a technology that monitors current flow and cuts off or limits the power supply when the current exceeds a safe threshold. Its core goal is to prevent excessive current from causing damage to equipment, circuits, or personnel, such as component burnout, fire, or even electric shock accidents.

[0003] Traditional current-limiting solutions typically fall into two categories: one, like a conventional mirror current-limiting circuit, offers fast response, but the current-limiting accuracy is poor because the threshold of the MOS device is susceptible to temperature and process changes. The other, using a current-sense resistor in conjunction with an op amp, offers high precision, but the op amp's slow response leads to a sluggish response, and the current-sense resistor consumes additional power. These technical shortcomings limit the effectiveness of current protection circuits in high-performance applications, particularly those requiring high precision and fast response. Consequently, current protection solutions in related technologies struggle to achieve both fast response and high-precision current limiting. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a current protection circuit and a power protection system to solve the above-mentioned problems.

[0005] In a first aspect, an embodiment of the present application provides a current protection circuit, the current protection circuit comprising: a first power tube, a first current limiting loop, and a second current limiting loop, wherein the drain and source of the first power tube are respectively connected to a power input terminal and a load output terminal, the gate of the first power tube is connected to a bias voltage, and the first current limiting loop and the second current limiting loop are respectively connected to the gate of the first power tube, wherein:

[0006] The second current limiting loop is configured to start responding when the load current flowing through the first power tube exceeds a second current threshold, and after a loop response time, control the gate voltage of the first power tube to a second voltage value to limit the load current within the second current threshold;

[0007] The first current limiting loop is used to control the gate voltage of the first power tube to a first voltage value within the loop response time after the second current limiting loop starts to operate, when the load current exceeds a first current threshold, so as to limit the load current within the first current threshold; the first current threshold is greater than the second current threshold, and the first voltage value is greater than the second voltage value.

[0008] During the implementation of the above scheme, the second current limiting loop can be first started when the load current exceeds the lower second current threshold, and then within the loop response time from the start of the second current limiting loop to the formal effect, the first current limiting loop can be started when the load current exceeds the higher first current threshold, limiting the load current within the first current threshold, until the second current limiting loop is formally effective, and the second current limiting loop can further limit the load current within the second current threshold. On the one hand, the above scheme adopts a segmented current protection method, which is conducive to improving the current protection effect of the above current protection circuit; on the other hand, the segmented current protection method enables the above current protection circuit to operate stably under different load conditions, which is conducive to improving the stability of the above current protection circuit; on the other hand, the second current limiting loop can accurately control the current, while the first current limiting loop can respond quickly. The combination of the first current limiting loop and the second current limiting loop enables the above current protection circuit to take into account both current protection speed and accuracy, thereby improving the current protection performance of the above current protection circuit.

[0009] In an implementation of the first aspect, the first current limiting loop includes a first current replicating unit and a first current limiting executing unit, wherein:

[0010] The first current copy unit includes a second power tube, which is a mirror image power tube of the first power tube, a gate of the second power tube is connected to the bias voltage, a drain of the second power tube is connected to the power input terminal, and a source of the second power tube is connected to the load output terminal;

[0011] The first current limiting execution part is respectively connected to the gate and source of the second power tube.

[0012] During the implementation of the above solution, the first current limiting loop replicates the current through the mirror power tube, and there is no need to set a current sensing resistor on the first power tube, thus avoiding power loss and cost increase caused by the current sensing resistor; on the other hand, the mirror power tube can accurately replicate the current of the first power tube, thereby achieving high-precision detection of the load current, which is beneficial to improving the accuracy and reliability of current detection of the above current protection circuit; on the other hand, the current replication of the mirror power tube has the characteristic of fast response, and can quickly detect the current change and respond at the moment the load current changes, which is beneficial to improving the response rate of the above current protection circuit.

[0013] In an implementation of the first aspect, the first current limiting execution unit includes a third power tube and a first detection resistor, wherein:

[0014] The first detection resistor is installed between the source of the second power tube and the load output terminal, one end of the first detection resistor is connected to the source of the second power tube, and the other end of the first detection resistor is connected to the load output terminal;

[0015] The gate of the third power tube is connected to the source of the second power tube, the drain of the third power tube is connected to the gate of the second power tube, and the source of the third power tube is connected to the load output end; the threshold voltage value of the third power tube is the first voltage value.

[0016] During the implementation of the above solution, the third power tube and the first detection resistor can quickly respond to changes in the load current. When the load current exceeds the first current threshold, the voltage drop on the first detection resistor can increase rapidly, thereby triggering the third power tube to turn on, timely limiting the gate voltage of the first power tube, and realizing fast current limiting protection; on the other hand, the fast current limiting function can be achieved through the third power tube and the first detection resistor, reducing the number of required components, reducing the complexity of the circuit and the risk of failure; on the other hand, the circuit of the first current limiting execution unit is relatively simple, which is conducive to improving the stability of the above current protection circuit.

[0017] In an implementation of the first aspect, a width-to-length ratio of the first power tube is greater than a width-to-length ratio of the second power tube.

[0018] During the implementation of the above solution, the second power tube with a smaller width-to-length ratio can pass a relatively small current, which helps to reduce the power loss of the first current limiting loop, thereby improving the power loss of the above current protection circuit; on the other hand, the second power tube, as a mirror power tube of the first power tube, can accurately replicate the load current flowing through the first power tube according to a certain ratio, which is conducive to the above current protection circuit's precise control of the load current; on another hand, the second power tube with a smaller width-to-length ratio can pass a relatively small current, which can reduce the quality requirements for the first detection resistor, and is conducive to reducing the implementation cost of the above current protection circuit.

[0019] In an implementation of the first aspect, the second current limiting loop includes a second current replicating unit and a second current limiting executing unit, wherein:

[0020] The second current copying unit includes a fourth power tube, which is a mirror image power tube of the first power tube, a gate of the fourth power tube connected to the bias voltage, a drain of the fourth power tube connected to the power input terminal, and a source of the fourth power tube connected to the load output terminal;

[0021] The second current limiting execution part is respectively connected to the gate and source of the fourth power tube.

[0022] During the implementation of the above solution, the second current limiting loop replicates the current through the mirror power tube, and there is no need to set a current sensing resistor on the first power tube, thus avoiding power loss and cost increase caused by the current sensing resistor; on the other hand, the mirror power tube can accurately replicate the current of the first power tube, thereby achieving high-precision detection of the load current, which is beneficial to improving the accuracy and reliability of current detection of the above current protection circuit; on the other hand, the current replication of the mirror power tube has the characteristic of fast response, and can quickly detect the current change and respond at the moment the load current changes, which is beneficial to improving the response rate of the above current protection circuit.

[0023] In an implementation of the first aspect, the second current limiting execution unit includes a fifth power tube, a second detection resistor, and a transconductance amplifier, wherein:

[0024] The second detection resistor is installed between the source of the fourth power tube and the load output terminal, one end of the second detection resistor is connected to the source of the fourth power tube, and the other end of the second detection resistor is connected to the load output terminal;

[0025] The drain of the fifth power tube is connected to the gate of the fourth power tube, the source of the fifth power tube is connected to the load output terminal, and the gate of the fifth power tube is connected to the output terminal of the transconductance amplifier;

[0026] The positive input terminal of the transconductance amplifier is connected to the source of the fourth power tube, and the negative input terminal of the transconductance amplifier is connected to a reference voltage; the voltage value of the reference voltage is the second voltage value.

[0027] During the implementation of the above scheme, the second current limiting loop accurately compares the voltage across the second detection resistor with the reference voltage through a transconductance amplifier, converts the voltage difference into a control current, and achieves high-precision regulation of the load current, which is beneficial to improving the current limiting accuracy of the above current protection circuit; on the other hand, it can enable the above current protection circuit to be applied to more application scenarios, which is beneficial to improving the adaptability of the above current protection circuit.

[0028] In an implementation of the first aspect, the second current limiting execution unit includes: a fifth power tube, a sixth power tube, a second detection resistor, and a transconductance amplifier, wherein:

[0029] The sixth power tube is a mirror image power tube of the fifth power tube, the drain of the fifth power tube is connected to the gate of the fourth power tube, the source of the fifth power tube is connected to the load output end, and the gate of the fifth power tube is connected to the gate of the sixth power tube;

[0030] The drain of the sixth power tube is connected to the output end of the transconductance amplifier, and the source of the sixth power tube is connected to the load output end;

[0031] The positive input terminal of the transconductance amplifier is connected to the source of the fourth power tube, and the negative input terminal of the transconductance amplifier is connected to a reference voltage; the voltage value of the reference voltage is the second voltage value.

[0032] During the implementation of the above solution, the fifth power tube and the sixth power tube form a current mirror, thereby copying the output signal of the transconductance amplifier to the gate of the fifth power tube, thereby isolating the transconductance amplifier from the power tube, which is beneficial to improving the safety of the above current protection circuit; on the other hand, the current mirror can provide suitable load characteristics for subsequent circuits to meet the input requirements of the power tube.

[0033] In an implementation of the first aspect, the second detection resistor is an adjustable resistor.

[0034] In the implementation process of the above scheme, the second detection resistor is an adjustable resistor. By adjusting the resistance value of the second detection resistor, process deviations can be compensated, thereby improving the current limiting accuracy of the above current protection circuit; on the other hand, by adjusting the resistance value of the second detection resistor, the second current threshold of the second current limiting loop can be accurately set to ensure that the load current can be accurately detected and limited under different process conditions, which is conducive to improving the accuracy and stability of the above current protection circuit.

[0035] In an implementation of the first aspect, a width-to-length ratio of the first power tube is greater than a width-to-length ratio of the fourth power tube.

[0036] During the implementation of the above solution, the fourth power tube with a relatively small width-to-length ratio can pass a relatively small current, which helps to reduce the power loss of the second current limiting loop, thereby improving the power loss of the above current protection circuit; on the other hand, the fourth power tube, as a mirror power tube of the first power tube, can accurately replicate the load current flowing through the first power tube according to a certain ratio, which is beneficial to the above current protection circuit's precise control of the load current.

[0037] In a second aspect, an embodiment of the present application provides a power supply protection system, comprising: a power supply input terminal, a load output terminal, and a current protection circuit connected between the power supply input terminal and the load output terminal; the current protection circuit is a current protection circuit provided by the first aspect or any possible implementation method of the first aspect.

[0038] Other features and advantages of the present application will be described in the following description and, in part, will become apparent from the description or be understood by practicing the embodiments of the present application. The objectives and other advantages of the present application can be achieved and obtained through the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 A schematic diagram of the structure of the current protection circuit provided in an embodiment of the present application;

[0041] Figure 2 A schematic structural diagram of a first current limiting loop provided in an embodiment of the present application;

[0042] Figure 3 Another structural schematic diagram of the first current limiting loop provided in an embodiment of the present application;

[0043] Figure 4 A schematic structural diagram of a second current limiting loop provided in an embodiment of the present application;

[0044] Figure 5 Another structural schematic diagram of the second current limiting loop provided in an embodiment of the present application;

[0045] Figure 6 Another structural schematic diagram of the second current limiting loop provided in an embodiment of the present application;

[0046] Figure 7 A schematic diagram of the structure of a current protection circuit in a certain application scenario provided by an embodiment of the present application;

[0047] Figure 8 This is a schematic diagram of the change curves of the gate voltage of the power tube M1, the load current flowing through M1, the voltage at the resistor R1, and the voltage at the resistor R2 of the current protection circuit in a certain application scenario provided by an embodiment of the present application.

[0048] The numbers in the figure show:

[0049] 100, current protection circuit, 110, first power tube, 120, first current limiting loop, 121, second power tube, 122, first current limiting execution unit, 1221, third power tube, 1222, first detection resistor; 130, second current limiting loop, 131, fourth power tube, 132, second current limiting execution unit, 1321, fifth power tube, 1322, second detection resistor, 1323, transconductance amplifier, 1324, sixth power tube. DETAILED DESCRIPTION

[0050] The following will describe the technical solutions in the embodiments of the present application in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application and are therefore only examples and cannot be used to limit the scope of protection of the present application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0052] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0053] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] See Figure 1 The present embodiment provides a current protection circuit 100, including: a first power transistor 110, a first current limiting loop 120, and a second current limiting loop 130. The drain and source of the first power transistor 110 are connected to a power input terminal and a load output terminal, respectively. The gate of the first power transistor 110 is connected to a bias voltage. The first current limiting loop 120 and the second current limiting loop 130 are respectively connected to the gate of the first power transistor 110.

[0055] The second current limiting loop 130 is configured to start responding when the load current flowing through the first power transistor 110 exceeds a second current threshold, and after a loop response time, control the gate voltage of the first power transistor 110 to a second voltage value to limit the load current to within the second current threshold;

[0056] The first current limiting loop 120 is used to control the gate voltage of the first power tube 110 to a first voltage value within the loop response time after the second current limiting loop 130 starts operating, when the load current exceeds the first current threshold, so as to limit the load current to within the first current threshold; the first current threshold is greater than the second current threshold, and the first voltage value is greater than the second voltage value.

[0057] The power tube mentioned above refers to a power semiconductor device, which is a semiconductor switching device or a switching device. Its core function in the current protection circuit 100 is to quickly turn on and off the current in the circuit.

[0058] For example, the first power transistor 110 (also referred to as M1 in the accompanying drawings) can be installed between a power supply and a load, with its drain connected to the power supply input and its source connected to the load output. By controlling the conduction characteristics of the first power transistor 110, the on / off state of the first power transistor 110 and the load current flowing through the first power transistor 110 can be controlled. The first current limiting loop 120 and the second current limiting loop 130 primarily control the conduction characteristics of the first power transistor 110 by controlling the gate voltage of the first power transistor 110.

[0059] Exemplarily, the second current limiting loop 130 can be referred to as a high-precision current limiting loop. This loop can begin operating when the load current exceeds a second current threshold value having a smaller value, and requires a working loop response time to act on the gate voltage of the first power tube 110, thereby limiting the load current. From the time the second current limiting loop 130 begins operating until it acts on the gate voltage of the first power tube 110, the current protection circuit 100 can limit the load current through the first current limiting loop 120. The first current limiting loop 120 can be referred to as a fast current limiting loop. The time from the start of operation to the time it acts on the gate voltage of the first power tube 110 is extremely short, enabling the first current limiting loop 120 to quickly limit the load current. The combination of the first current limiting loop 120 and the second current limiting loop 130 enables the current protection circuit 100 to achieve both high speed and high precision.

[0060] In the above scheme, the second current limiting loop 130 can be first activated when the load current exceeds the lower second current threshold. Then, during the loop response time from the start of operation of the second current limiting loop 130 to the formal operation, the first current limiting loop 120 can be activated when the load current exceeds the higher first current threshold, limiting the load current to within the first current threshold until the second current limiting loop is formally activated. The second current limiting loop 130 can further limit the load current to within the second current threshold. On the one hand, the above scheme adopts a segmented current protection method, which is conducive to improving the current protection effect of the above current protection circuit 100. On the other hand, the segmented current protection method enables the above current protection circuit 100 to operate stably under different load conditions, which is conducive to improving the stability of the above current protection circuit 100. On the other hand, the second current limiting loop 130 can accurately control the current, while the first current limiting loop 120 can respond quickly. The combination of the first current limiting loop 120 and the second current limiting loop 130 enables the above current protection circuit 100 to achieve both current protection speed and accuracy, thereby improving the current protection performance of the above current protection circuit 100.

[0061] The structure of the first current limiting loop 120 is described below:

[0062] Optionally, the first current limiting loop 120 includes a first current replicating unit and a first current limiting executing unit 122, wherein: the first current replicating unit includes a second power tube 121, the second power tube 121 is a mirror power tube of the first power tube, the gate of the second power tube 121 is connected to the bias voltage, the drain of the second power tube 121 is connected to the power input terminal, and the source of the second power tube 121 is connected to the load output terminal; the first current limiting executing unit 122 is respectively connected to the gate and source of the second power tube 121. This embodiment is, for example:

[0063] See Figure 2 , M2 is the second power tube 121, the gate of M2 is connected to the bias voltage, the drain is connected to the power input terminal, the source is connected to the load output terminal, and the first current limiting execution unit 122 is connected to the gate and source of M2 respectively;

[0064] The first current limiting execution unit 122 can determine whether it is necessary to limit the load current through the mirror current copied by M2. When it is necessary to limit the load current, the first current limiting execution unit 122 can limit the load current flowing through M1 by controlling the gate voltage of the first power tube 110 (that is, the power tube M1).

[0065] The first current limiting loop 120 in the above-mentioned solution replicates the current through the mirror power tube, eliminating the need for a current-sense resistor on the first power tube 110, thereby avoiding power loss and cost increase caused by the current-sense resistor. On the other hand, the mirror power tube can accurately replicate the current of the first power tube 110, thereby achieving high-precision detection of the load current, which is beneficial to improving the accuracy and reliability of current detection performed by the above-mentioned current protection circuit 100. On the other hand, the current replication of the mirror power tube has a fast response characteristic, which can quickly detect and respond to the current change at the moment the load current changes, which is beneficial to improving the response rate of the above-mentioned current protection circuit 100.

[0066] The following describes the implementation of the first current limiting execution unit 122:

[0067] In the first embodiment, the first current limiting execution unit 122 uses at least one of a MOS tube, a transistor, and a detection resistor to achieve a fast response to the load current.

[0068] It can be understood that the technology of using MOS tubes, transistors and detection resistors to achieve rapid current protection is a relatively mature technology in this field. For its specific implementation scheme, please refer to the relevant technology, and the embodiments of this application will not be repeated.

[0069] The first implementation method: using a power tube in conjunction with a detection resistor to achieve a fast response to the load current;

[0070] Optionally, the first current limiting execution unit 122 includes a third power tube 1221 and a first detection resistor 1222, wherein: the first detection resistor 1222 is installed between the source of the second power tube 121 and the load output terminal, one end of the first detection resistor 1222 is connected to the source of the second power tube 121, and the other end of the first detection resistor 1222 is connected to the load output terminal; the gate of the third power tube 1221 is connected to the source of the second power tube 121, the drain of the third power tube 1221 is connected to the gate of the second power tube 121, and the source of the third power tube 1221 is connected to the load output terminal; the threshold voltage of the third power tube 1221 is a first voltage value. This embodiment is, for example:

[0071] See Figure 3 , Figure 3 The power tube M3 in the figure is the third power tube 1221. Figure 3 The resistor R1 in the circuit is the first detection resistor 1222. R1 is installed between the source of M2 and the load output terminal. One end of R1 is connected to the source of M2, and the other end of R1 is connected to the load output terminal. The gate of M3 is connected to the source of M2, the drain of M3 is connected to the gate of M2, and the source of M3 is connected to the load output terminal.

[0072] The third power tube 1221 and the first detection resistor 1222 in the above scheme can quickly respond to changes in the load current. When the load current exceeds the first current threshold, the voltage drop across the first detection resistor 1222 can increase rapidly, thereby triggering the third power tube 1221 to turn on, timely limiting the gate voltage of the first power tube 110, and realizing fast current limiting protection. On the other hand, the fast current limiting function can be achieved by the third power tube 1221 and the first detection resistor 1222, reducing the number of required components, reducing the complexity of the circuit and the risk of failure. On the other hand, the circuit of the first current limiting execution unit 122 is relatively simple, which is conducive to improving the stability of the above-mentioned current protection circuit 100.

[0073] Optionally, the width-to-length ratio of the first power tube 110 is greater than the width-to-length ratio of the second power tube 121 .

[0074] The aspect ratio (ALR) refers to the geometric dimensions of the channel region in a power transistor and is a key design parameter that influences the transistor's current drive capability and on-resistance. It's the ratio of the channel width to the channel length. Generally speaking, a larger ALR indicates a higher current per unit voltage and a lower on-resistance.

[0075] For example, the ratio of the width to length ratio of the power tube M2 (ie, the second power tube 121 ) to the width to length ratio of the power tube M1 (ie, the first power tube 110 ) can be set to 1:1000, that is, the current flowing through the power tube M2 is one thousandth of the load current flowing through M1.

[0076] In the above solution, the second power tube 121 with a smaller width-to-length ratio can pass a relatively small current, which helps to reduce the power loss of the first current limiting loop 120, thereby improving the power loss of the above current protection circuit 100; on the other hand, the second power tube 121, as a mirror power tube of the first power tube 110, can accurately replicate the load current flowing through the first power tube 110 according to a certain ratio, which is beneficial to the above current protection circuit 100 to accurately control the load current; on another hand, the second power tube 121 with a smaller width-to-length ratio can pass a relatively small current, which can reduce the quality requirements for the first detection resistor 1222, and is beneficial to reducing the implementation cost of the above current protection circuit 100.

[0077] The working principle of the first current limiting loop 120 is described below:

[0078] During normal operation, the load current flowing through M1 is within the normal range. M1's mirror tube M2 copies the load current flowing through M1. The copied mirror current of M2 flows through resistor R1 to generate a voltage. At this time, the voltage at R1 does not exceed the gate threshold voltage that can turn on M3. M3 remains in the off state and does not affect the normal conduction of M1. The current can flow smoothly from the drain to the source of M1.

[0079] When the load current flowing through M1 increases to the first current threshold due to load abnormality or other conditions, the mirror current copied by M2 also increases, causing the voltage at R1 to increase. Once the voltage at R1 exceeds the gate threshold voltage that can turn on M3, M3 will turn on, thereby pulling down the gate voltage of M1, limiting the conduction degree of M1, thereby limiting the further increase of the load current of M1 and realizing the current protection function.

[0080] For example, the first current threshold that can be limited by the first current limiting loop 120 can be calculated by the gate threshold voltage of M3. Specifically:

[0081] Assuming that the gate threshold voltage that can turn on M3 is Vth, and the ratio of the width-to-length ratio of the power tube M2 to the width-to-length ratio of the power tube M1 is 1:1000, then when the gate voltage of M3 is Vth, the current flowing through the resistor R1 is Vth / R1, that is, the mirror current flowing through M2 is Vth / R1. At this time, the load current flowing through M1 is 1000*Vth / R1. Therefore, the first current threshold can be set to: I M1_fast =1000*Vth / R1.

[0082] 1000*Vth / R1 is the first current threshold.

[0083] The structure of the second current limiting loop 130 is described below:

[0084] Optionally, the second current limiting loop 130 includes a second current replicating unit and a second current limiting executing unit 132, wherein: the second current replicating unit includes a fourth power tube 131, the fourth power tube 131 is a mirror power tube of the first power tube 110, the gate of the fourth power tube 131 is connected to the bias voltage, the drain of the fourth power tube 131 is connected to the power input terminal, and the source of the fourth power tube 131 is connected to the load output terminal; the second current limiting executing unit 132 is respectively connected to the gate and source of the fourth power tube 131. This embodiment is, for example:

[0085] See Figure 4 , M4 is the fourth power tube 131, the gate of M4 is connected to the bias voltage, the drain is connected to the power input terminal, the source is connected to the load output terminal, and the second current limiting execution unit 132 is connected to the gate and source of M4 respectively;

[0086] The second current limiting execution unit 132 can determine whether the load current needs to be limited by the mirror current copied by M4. When the load current needs to be limited, the second current limiting execution unit 132 can limit the load current flowing through M1 by controlling the gate voltage of the first power tube 110 (that is, the power tube M1).

[0087] The second current limiting loop 130 in the above-mentioned solution replicates the current through the mirror power tube, eliminating the need for a current-sense resistor on the first power tube 110, thereby avoiding power loss and cost increase caused by the current-sense resistor. On the other hand, the mirror power tube can accurately replicate the current of the first power tube 110, thereby achieving high-precision detection of the load current, which is beneficial to improving the accuracy and reliability of current detection performed by the above-mentioned current protection circuit 100. On the other hand, the current replication of the mirror power tube has a fast response characteristic, which can quickly detect and respond to the current change at the moment the load current changes, which is beneficial to improving the response rate of the above-mentioned current protection circuit 100.

[0088] The following describes the implementation of the second current limiting execution unit 132:

[0089] First embodiment: The second current limiting execution unit 132 uses a MOS tube, an operational amplifier and a detection resistor to achieve precise control of the load current;

[0090] It can be understood that the technology of using MOS tubes, operational amplifiers and detection resistors to achieve precise control of load current is a relatively mature technology in this field. For its specific implementation scheme, please refer to the relevant technology and will not be repeated in the embodiments of this application.

[0091] The second implementation method: using a transconductance amplifier, a power tube and a detection resistor to achieve precise control of the load current;

[0092] Optionally, the second current limiting execution unit 132 includes a fifth power tube 1321, a second detection resistor 1322, and a transconductance amplifier 1323, wherein: the second detection resistor 1322 is installed between the source of the fourth power tube 131 and the load output terminal, one end of the second detection resistor 1322 is connected to the source of the fourth power tube 131, and the other end of the second detection resistor 1322 is connected to the load output terminal; the drain of the fifth power tube 1321 is connected to the gate of the fourth power tube 131, the source of the fifth power tube 1321 is connected to the load output terminal, and the gate of the fifth power tube 1321 is connected to the output terminal of the transconductance amplifier 1323; the positive input terminal of the transconductance amplifier 1323 is connected to the source of the fourth power tube 131, and the negative input terminal of the transconductance amplifier 1323 is connected to the reference voltage Vref; the voltage value of the reference voltage Vref is the second voltage value. For example, this embodiment:

[0093] See Figure 5 , Figure 5 The power tube M5 is the fifth power tube 1321, the resistor R2 is the second detection resistor 1322, the gm amplifier is the transconductance amplifier 1323, R2 is installed between the source of M4 and the load output terminal, one end of R2 is connected to the source of M4, and the other end of R2 is connected to the load output terminal, the drain of M5 is connected to the gate of M4, the source of M5 is connected to the load output terminal, the gate of M5 is connected to the output terminal of the gm amplifier, the positive input terminal of the gm amplifier is connected to the source of M4, and the negative input terminal of the gm amplifier is connected to the reference voltage Vref. The voltage value of the reference voltage Vref is the second voltage value.

[0094] The transconductance amplifier 1323 is an amplifier that converts an input differential voltage into an output current. Its core function is to amplify and convert signals. gm, the symbol for transconductance, measures an amplifier's ability to convert input voltage into output current. It is defined as the ratio of the change in output current to the change in input voltage, and is typically measured in Siemens (S). For example, for an amplifier with gm = 1S, a 1V change in input voltage results in a 1A change in output current.

[0095] The second current limiting loop 130 in the above scheme accurately compares the voltage across the second detection resistor 1322 with the reference voltage through the transconductance amplifier 1323, converts the voltage difference into a control current, and achieves high-precision regulation of the load current, which is beneficial to improving the current limiting accuracy of the above-mentioned current protection circuit 100; on the other hand, it can enable the above-mentioned current protection circuit 100 to be applied to more application scenarios, which is beneficial to improving the adaptability of the above-mentioned current protection circuit 100.

[0096] For example, the output end of the transconductance amplifier 1323 may also control the gate voltage of the fifth power tube 1321 in a current mirror manner, which is implemented as follows:

[0097] Optionally, the second current limiting execution unit 132 includes: a fifth power tube 1321, a sixth power tube 1324, a second detection resistor 1322, and a transconductance amplifier 1323, wherein: the sixth power tube 1324 is a mirror power tube of the fifth power tube 1321, the drain of the fifth power tube 1321 is connected to the gate of the fourth power tube 131, the source of the fifth power tube 1321 is connected to the load output terminal, and the gate of the fifth power tube 1321 is connected to the gate of the sixth power tube 1324; the drain of the sixth power tube 1324 is connected to the output terminal of the transconductance amplifier 1323, and the source of the sixth power tube 1324 is connected to the load output terminal; the positive input terminal of the transconductance amplifier 1323 is connected to the source terminal of the fourth power tube 131, and the negative input terminal of the transconductance amplifier 1323 is connected to the reference voltage Vref; the voltage value of the reference voltage Vref is the second voltage value. For example, this embodiment:

[0098] See Figure 6 , Figure 6 The power tube M5 is the fifth power tube 1321, the resistor R2 is the second detection resistor 1322, the gm amplifier is the transconductance amplifier 1323, the power tube M6 is the sixth power tube 1324, M6 is a mirror power tube of M5, the drain of M5 is connected to the gate of M4, the source of M5 is connected to the load output end, the gate of M5 is connected to the gate of M6, the drain of M6 is connected to the output end of the gm amplifier, the source of M6 is connected to the load output end, the positive input end of the gm amplifier is connected to the source of M4, and the negative input end of the gm amplifier is connected to the reference voltage Vref. The voltage value of the reference voltage Vref is the second voltage value.

[0099] The fifth power tube 1321 and the sixth power tube 1324 in the above scheme form a current mirror, thereby copying the output signal of the transconductance amplifier 1323 to the gate of the fifth power tube 1321, thereby isolating the transconductance amplifier 1323 from the power tube, which is beneficial to improving the safety of the above current protection circuit 100; on the other hand, the current mirror can provide suitable load characteristics for subsequent circuits to meet the input requirements of the power tube.

[0100] Exemplarily, the above-mentioned reference voltage Vref can be a reference voltage generated by a bandgap reference. The bandgap reference is a circuit technology that uses the energy band characteristics of semiconductor devices to generate precise reference voltages. It uses the energy bandgap design of silicon to ensure that the output voltage remains highly stable under different temperatures and process conditions.

[0101] Optionally, the second detection resistor 1322 is an adjustable resistor.

[0102] The above-mentioned adjustable resistor is a special type of resistor that can be fine-tuned in the later stage of the manufacturing process or before use to achieve a precise target resistance value. The above-mentioned current protection circuit 100 can solve the problem of process drift by adjusting the resistance value of the second detection resistor 1322.

[0103] The second detection resistor 1322 in the above scheme is an adjustable resistor. By adjusting the resistance value of the second detection resistor 1322, process deviations can be compensated, thereby improving the current limiting accuracy of the above current protection circuit 100; on the other hand, by adjusting the resistance value of the second detection resistor 1322, the second current threshold of the second current limiting loop 130 can be accurately set to ensure that the load current can be accurately detected and limited under different process conditions, which is beneficial to improving the accuracy and stability of the above current protection circuit 100.

[0104] In addition, in a typical BCD (Bipolar-CMOS-DMOS) 180 nm process, a low-temperature drift resistor may be selected as the second detection resistor 1322 to compensate for temperature drift.

[0105] Optionally, the width-to-length ratio of the first power tube 110 is greater than the width-to-length ratio of the fourth power tube 131 .

[0106] For example, the ratio of the width to length ratio of the power tube M4 (ie, the fourth power tube 131 ) to the width to length ratio of the power tube M1 (ie, the first power tube 110 ) can be set to 1:1000, that is, the current flowing through the power tube M4 is one thousandth of the load current flowing through M1.

[0107] In the above solution, the fourth power tube 131 with a relatively small width-to-length ratio can pass a relatively small current, which helps to reduce the power loss of the second current limiting loop 130, thereby improving the power loss of the above current protection circuit 100. On the other hand, the fourth power tube 131, as a mirror power tube of the first power tube 110, can accurately replicate the load current flowing through the first power tube 110 according to a certain ratio, which is beneficial to the above current protection circuit 100 to accurately control the load current.

[0108] The working principle of the second current limiting loop 130 is described below:

[0109] During normal operation, the load current flowing through M1 is within the normal range. The mirror tube M4 of M1 copies the load current flowing through M1. The mirror current copied by M4 flows through R2 to generate a voltage. At this time, the voltage at R2 does not exceed the reference voltage Vref. M5 remains in the off state, which does not affect the normal conduction of M1. The current can flow normally from the drain to the source of M1.

[0110] When the load current flowing through M1 increases to the second current threshold due to load abnormality or other conditions, the mirror current copied by M4 also increases, causing the voltage at R2 to increase. Once the voltage at R2 exceeds the reference voltage Vref, the gm amplifier outputs current to M6, and M6's mirror tube M5 turns on, thereby pulling down the gate voltage of M1, limiting the conduction degree of M1, thereby limiting the further increase of M1's load current and realizing the current protection function.

[0111] For example, the second current threshold that can be limited by the second current limiting loop 130 can be calculated using the reference voltage Vref. Specifically:

[0112] Assuming that the ratio of the width to length of the power tube M4 to the width to length of the power tube M1 is 1:1000, when the second current limiting loop 130 is working, the current flowing through M5 is I M5 =gm*(V R2 -Vref), V R2 =R2*I M1 / 1000, the load current flowing through M1 is: I M1 =1000*(I M5 +Vref*gm) / (gm*R2);

[0113] Among them, I M5 ≪Vref*gm, therefore, the load current flowing through M1 can be simplified to: I M1 =1000* Vref / R2.

[0114] Therefore, the second current threshold can be set to: I M1_accu =1000*Vref / R2.

[0115] It is understandable that, due to the slew rate of the gm amplifier, the loop response time of the second current limiting loop 130 from the start of operation to the formal operation (i.e., the loop response time in the above content) is T=Cgate / gm, where Cgate is the main pole capacitance of the second current limiting loop 130.

[0116] The working principle of the above-mentioned current protection circuit 100 in a certain application scenario is introduced below:

[0117] See Figure 7 The current protection circuit 100 includes: a power tube M1, a first current limiting loop 120, and a second current limiting loop. The first current limiting loop 120 includes power tubes M2, M3, and a resistor R1. The second current limiting loop 130 includes power tubes M4, M5, M6, an adjustable resistor R2, and a gm amplifier. The connection relationship between the various components is described in the above description of the first current limiting loop 120 and the second current limiting loop 130, which will not be repeated here.

[0118] The working principle of the above current protection circuit 100 is:

[0119] See Figure 8 During normal operation, the gate voltage of M1 is greater than the gate threshold voltage Vth' of M1, M1 is normally turned on, and the load current flowing through M1 is within the normal range. The mirror tube M2 of M1 copies the load current flowing through M1, and the copied mirror current of M2 flows through the resistor R1 to generate a voltage. At this time, the voltage at R1 does not exceed the gate threshold voltage Vth that can turn on M3, and M3 remains in the off state, which does not affect the normal conduction of M1;

[0120] In addition, the load current flowing through M1 is within the normal range. The mirror tube M4 of M1 copies the load current flowing through M1. The mirror current copied by M4 flows through R2 to generate a voltage. At this time, the voltage at R2 fails to exceed the reference voltage Vref. M5 remains in the cut-off state, which does not affect the normal conduction of M1. The current can flow normally from the drain to the source of M1.

[0121] When the load current flowing through M1 (i.e. Figure 8 The M1 current in the circuit increases to the second current threshold I due to abnormal load conditions. M1_accu When the mirror current copied by M4 increases, the voltage at R2 (i.e. Figure 8 Once the voltage at R2 exceeds the reference voltage Vref, the second current limiting loop 130 starts to work.

[0122] The time from the start of the second current limiting loop 130 to its formal operation is the loop response time T = Cgate / gm. After the loop response time, the gm amplifier outputs current to M6, and the mirror tube M5 of M6 is turned on, thereby pulling down the gate voltage of M1, so that the conduction degree of M1 is limited, thereby limiting the load current flowing through M1 to the second current threshold I M1_accu Inside.

[0123] During the loop response time, the current protection function is provided by the first current limiting loop 120. Specifically:

[0124] When the load current flowing through M1 (i.e. Figure 8 The M1 current in the circuit increases to the first current threshold I due to abnormal load conditions. M1_fast When the mirror current copied by M2 (i.e. Figure 8 The voltage of M2 Vsense in the circuit also increases, causing the voltage at R1 to increase. Once the voltage at R1 exceeds the gate threshold voltage Vth that can turn on M3, M3 will turn on, thereby pulling down the gate voltage of M1, limiting the conduction degree of M1 and limiting the load current flowing through M1 to IM1_fast Inside.

[0125] Therefore, through the cooperation of the first current limiting loop 120 and the second current limiting loop 130, high-precision and fast current limiting of the load current is achieved, so that the above-mentioned current protection circuit 100 can take into account both current protection accuracy and speed.

[0126] In addition, the first current threshold I M1_fast Set as the second current threshold I M1_accu 1.5~2 times of that, on the one hand, for safety reasons, I M1_fast Set to I M1_accu 1.5~2 times of the I can ensure that when an abnormal situation occurs, the current will not exceed the maximum tolerance of the power tube and related circuit components, thereby protecting the circuit from damage; on the other hand, if I M1_fast Setting it too high may cause the circuit to waste too much power during the rapid current limiting stage, while setting it too low may not be able to effectively respond to sudden overcurrent conditions. Therefore, a range of 1.5 to 2 times is a relatively reasonable compromise. On the other hand, such a setting can ensure fast response while providing sufficient dynamic range, allowing the circuit to operate stably under different operating conditions.

[0127] Based on the same inventive concept, an embodiment of the present application also provides a power protection system, including a power input terminal, a load output terminal, and a current protection circuit connected between the power input terminal and the load output terminal, and the current protection circuit is the above-mentioned current protection circuit 100.

[0128] In the embodiments provided in this application, it should be understood that the disclosed devices and systems can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interface, the indirect coupling or communication connection of the device or unit can be electrical, mechanical or other forms.

[0129] In addition, the units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0130] The above are merely examples of the present application and are not intended to limit the scope of protection of the present application. Those skilled in the art will appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A current protection circuit, characterized in that: The current protection circuit includes: a first power tube, a first current limiting loop, and a second current limiting loop, wherein the drain and source of the first power tube are respectively connected to the power input terminal and the load output terminal, the gate of the first power tube is connected to the bias voltage, and the first current limiting loop and the second current limiting loop are respectively connected to the gate of the first power tube, wherein: The second current limiting loop is configured to start responding when the load current flowing through the first power tube exceeds a second current threshold, and after a loop response time, control the gate voltage of the first power tube to a second voltage value to limit the load current within the second current threshold; The first current limiting loop is used to control the gate voltage of the first power tube to a first voltage value within the loop response time after the second current limiting loop starts to operate, when the load current exceeds a first current threshold, so as to limit the load current within the first current threshold; the first current threshold is greater than the second current threshold, and the first voltage value is greater than the second voltage value.

2. The current protection circuit according to claim 1, characterized in that: The first current limiting loop includes a first current replicating unit and a first current limiting executing unit, wherein: The first current copy unit includes a second power tube, which is a mirror image power tube of the first power tube, a gate of the second power tube is connected to the bias voltage, a drain of the second power tube is connected to the power input terminal, and a source of the second power tube is connected to the load output terminal; The first current limiting execution part is respectively connected to the gate and source of the second power tube.

3. The current protection circuit according to claim 2, characterized in that: The first current limiting execution unit includes a third power tube and a first detection resistor, wherein: The first detection resistor is installed between the source of the second power tube and the load output terminal, one end of the first detection resistor is connected to the source of the second power tube, and the other end of the first detection resistor is connected to the load output terminal; The gate of the third power tube is connected to the source of the second power tube, the drain of the third power tube is connected to the gate of the second power tube, and the source of the third power tube is connected to the load output end; the threshold voltage value of the third power tube is the first voltage value.

4. The current protection circuit according to claim 2, characterized in that: The width-to-length ratio of the first power tube is greater than the width-to-length ratio of the second power tube.

5. The current protection circuit according to claim 1, characterized in that: The second current limiting loop includes a second current copying unit and a second current limiting execution unit, wherein: The second current copying unit includes a fourth power tube, which is a mirror image power tube of the first power tube, a gate of the fourth power tube connected to the bias voltage, a drain of the fourth power tube connected to the power input terminal, and a source of the fourth power tube connected to the load output terminal; The second current limiting execution part is respectively connected to the gate and source of the fourth power tube.

6. The current protection circuit according to claim 5, characterized in that: The second current limiting execution unit includes a fifth power tube, a second detection resistor and a transconductance amplifier, wherein: The second detection resistor is installed between the source of the fourth power tube and the load output terminal, one end of the second detection resistor is connected to the source of the fourth power tube, and the other end of the second detection resistor is connected to the load output terminal; The drain of the fifth power tube is connected to the gate of the fourth power tube, the source of the fifth power tube is connected to the load output terminal, and the gate of the fifth power tube is connected to the output terminal of the transconductance amplifier; The positive input terminal of the transconductance amplifier is connected to the source of the fourth power tube, and the negative input terminal of the transconductance amplifier is connected to a reference voltage; the voltage value of the reference voltage is the second voltage value.

7. The current protection circuit according to claim 5, characterized in that: The second current limiting execution unit includes: a fifth power tube, a sixth power tube, a second detection resistor and a transconductance amplifier, wherein: The sixth power tube is a mirror image power tube of the fifth power tube, the drain of the fifth power tube is connected to the gate of the fourth power tube, the source of the fifth power tube is connected to the load output end, and the gate of the fifth power tube is connected to the gate of the sixth power tube; The drain of the sixth power tube is connected to the output end of the transconductance amplifier, and the source of the sixth power tube is connected to the load output end; The positive input terminal of the transconductance amplifier is connected to the source of the fourth power tube, and the negative input terminal of the transconductance amplifier is connected to a reference voltage; the voltage value of the reference voltage is the second voltage value.

8. The current protection circuit according to claim 6 or 7, characterized in that: The second detection resistor is an adjustable resistor.

9. The current protection circuit according to claim 5, characterized in that: The width-to-length ratio of the first power tube is greater than the width-to-length ratio of the fourth power tube.

10. A power protection system, characterized in that: include: A power input terminal, a load output terminal, and a current protection circuit connected between the power input terminal and the load output terminal; The current protection circuit is the current protection circuit according to any one of claims 1 to 9.

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