An overcurrent protection circuit with externally adjustable overcurrent threshold

Abstract

The present invention provides an overcurrent protection circuit with an externally adjustable overcurrent threshold, wherein the output end of a current reference module is connected to the reference input end of a current comparison module; N comparison input ends of the current comparison module are connected to N detection ends of a current detection module in a one-to-one correspondence; N output ends of the current comparison module are connected to N input ends of a control module in a one-to-one correspondence; the output end of the control module is connected to the control end of the current detection module; the enable end of the current detection module serves as the enable end of the overcurrent protection circuit; the output end of the current detection module serves as the output end of the overcurrent protection circuit; the current reference module, the current comparison module, the current detection module and the control module are combined to enable the overcurrent protection circuit to generate N overcurrent thresholds, and different overcurrent thresholds can be adjusted by inputting an enable signal, thereby greatly reducing the static power consumption of the circuit and improving the reliability and stability of the circuit.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and more particularly, relates to an overcurrent protection circuit with an externally adjustable overcurrent threshold. Background Art

[0002] Smart power chip circuits are widely used in the market, offering advantages such as strong driving capabilities and low power consumption. However, because these chip circuits may operate under high current conditions, they can be damaged. To ensure the reliable operation of these smart power chip circuits and their loads, an overcurrent protection module must be integrated within the chip. This module is a fundamental component of the chip circuit. When it detects that the load current exceeds a set overcurrent threshold, it shuts down the circuit to protect the entire chip circuit and the load. Therefore, the overcurrent protection module is crucial for the stable operation of the chip circuit.

[0003] The working principle of the traditional overcurrent protection circuit is as follows Figure 1 As shown in the figure, the sampling tube MP2 is responsible for sampling the changes in the load current, and the current mirrors MN1 and MN2 replicate the sampled current; MN3 acts as a constant current source, and after passing through the current mirrors MP4 and MP5, it is compared with the sampled current in MN2 to determine the high and low levels of the gate voltage of MP3. When MP1 is working normally, I P4 >I N2 , V GP3 When the overcurrent is high, MP3 is turned off. P4 N2 , V GP3 is low level, MP3 is turned on, and the gate voltage of MP1 is pulled to a high level, thereby realizing the overcurrent protection function.

[0004] However, the bias current error of the constant current source controlled by the bias voltage in the prior art is large when the temperature changes, thereby affecting the current threshold of the overcurrent protection circuit and reducing the circuit accuracy. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide an overcurrent protection circuit whose overcurrent threshold can be externally adjusted, which is used to provide multiple overcurrent thresholds, reduce the static power consumption of the circuit, and improve the reliability and stability of the circuit.

[0006] The present application discloses an overcurrent protection circuit with an externally adjustable overcurrent threshold, comprising: a current reference module, a current comparison module, a current detection module and a control module;

[0007] The power supply terminal of the current reference module, the power supply terminal of the current comparison module and the power supply terminal of the control module are all connected to a power supply;

[0008] ​The output terminal of the current reference module is connected to the reference input terminal of the current comparison module;

[0009] The N comparison input terminals of the current comparison module are connected to the N detection terminals of the current detection module in a one-to-one correspondence; N is a positive integer greater than 1;

[0010] The N output terminals of the current comparison module are connected to the N input terminals of the control module in a one-to-one correspondence;

[0011] The output end of the control module is connected to the control end of the current detection module;

[0012] The enable terminal of the current detection module serves as the enable terminal of the overcurrent protection circuit;

[0013] The output end of the current detection module serves as the output end of the overcurrent protection circuit;

[0014] In combination with the current reference module, the current comparison module, the current detection module and the control module, the overcurrent protection circuit generates N overcurrent thresholds.

[0015] Optionally, the current reference module includes: a reference startup circuit and a reference generation circuit;

[0016] The first end of the reference startup circuit is connected to the first end of the reference generation circuit, and the connection point serves as the power supply end of the current reference module;

[0017] The second end of the reference startup circuit and the second end of the reference generation circuit are both grounded;

[0018] The third terminal of the reference startup circuit is connected to the third terminal of the reference generation circuit.

[0019] Optionally, the reference startup circuit includes: a first resistor, a first switch tube, and a second switch tube;

[0020] One end of the first resistor serves as the first end of the reference startup circuit;

[0021] The other end of the first resistor is respectively connected to the control end of the first switch tube, the first end of the first switch tube, the first end of the second switch tube, and the control end of the second switch tube;

[0022] The second end of the first switch tube serves as the third end of the reference startup circuit;

[0023] The second end of the second switch tube serves as the second end of the reference startup circuit.

[0024] Optionally, the reference generation circuit includes: a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube and a second resistor;

[0025] The first end of the third switch tube is connected to the first end of the fifth switch tube, and the connection point serves as the first end of the reference generation circuit;

[0026] The second end of the third switch tube is connected to the control end of the sixth switch tube and the first end of the fourth switch tube respectively, and the connection point serves as the third end of the reference generation circuit;

[0027] The control end of the third switch tube is respectively connected to the second end of the fifth switch tube, the control end of the fifth switch tube and the first end of the sixth switch tube;

[0028] The second end of the sixth switch tube is connected to the control end of the fourth switch tube and one end of the second resistor respectively;

[0029] The other end of the second resistor is connected to the second end of the fourth switch tube, and the connection point serves as the second end of the reference generation circuit.

[0030] Optionally, the current comparison module includes: N comparison circuits;

[0031] The reference input terminal of each comparison circuit is connected to the reference input terminal of the current comparison module;

[0032] The comparison input terminal of the comparison circuit serves as a comparison input terminal of the current comparison module;

[0033] The output end of the comparison circuit serves as an output end of the current comparison module;

[0034] The power supply terminal of each comparison circuit is connected to the power supply terminal of the current comparison module;

[0035] The ground terminals of the comparison circuits are all grounded.

[0036] Optionally, the comparison circuit includes: a seventh switching tube, an eighth switching tube, a ninth switching tube, a tenth switching tube, a third resistor, and a fourth resistor;

[0037] The control terminal of the seventh switch tube is connected to the control terminal of the ninth switch tube, and the connection point serves as the reference input terminal of the comparison circuit;

[0038] The first end of the seventh switch tube is connected to the first end of the ninth switch tube, and the connection point serves as the power supply end of the comparison circuit;

[0039] The second end of the seventh switch tube is respectively connected to the first end of the eighth switch tube, the control end of the eighth switch tube and the control end of the tenth switch tube;

[0040] The second end of the ninth switch tube is connected to the first end of the tenth switch tube, and the connection point serves as the output end of the comparison circuit;

[0041] The second end of the tenth switch tube is connected to one end of the fourth resistor, and the connection point serves as a comparison input end of the comparison circuit;

[0042] The second end of the eighth switch tube is connected to one end of the third resistor;

[0043] The other end of the fourth resistor is connected to the other end of the third resistor, and the connection point serves as the ground terminal of the comparison circuit.

[0044] Optionally, the current detection module includes: N detection circuits and an eleventh switch tube;

[0045] The control end of the detection circuit is connected to the control end of the eleventh switch tube, and the connection point serves as the control end of the current detection module;

[0046] The output end of the detection circuit is connected to the first end of the eleventh switch tube, and the connection point serves as the output end of the current detection module;

[0047] The detection end of the detection circuit serves as a detection end of the current detection module;

[0048] The enabling terminal of the detection circuit serves as an enabling terminal of the current detection module;

[0049] The ground terminal of the detection circuit is grounded.

[0050] Optionally, the detection circuit includes: a sampling tube and an enable control tube;

[0051] The first end of the sampling tube serves as the output end of the detection circuit;

[0052] The control end of the sampling tube serves as the control end of the detection circuit;

[0053] The second end of the sampling tube is connected to the first end of the enabling control tube, and the connection point serves as the detection end of the detection circuit;

[0054] The second end of the enabling control tube serves as the grounding end of the detection circuit;

[0055] The control end of the enable control tube serves as the enable end of the detection circuit;

[0056] Optionally, the enabling control tube includes a built-in switch tube or an external switch.

[0057] Optionally, the control module includes: an N-input comparator, a charging switch tube, a ninth resistor, and N discharge switch tubes;

[0058] The N input terminals of the N-input comparator are respectively connected to the N input terminals of the control module;

[0059] The control terminals of the N discharge switch tubes are respectively connected to the N input terminals of the control module;

[0060] The output terminal of the N-input comparator is connected to the control terminal of the charging switch tube;

[0061] The first end of the charging switch tube serves as the power supply end of the control module;

[0062] The second end of the charging switch tube is respectively connected to one end of the ninth resistor and the first ends of the N discharge switch tubes;

[0063] The other end of the ninth resistor serves as the output end of the control module;

[0064] The second end of the discharge switch tube is grounded.

[0065] As can be seen from the above technical solution, the present invention provides an overcurrent protection circuit with an externally adjustable overcurrent threshold, wherein the power supply terminal of the current reference module, the power supply terminal of the current comparison module, and the power supply terminal of the control module are all connected to a power supply; the output terminal of the current reference module is connected to the reference input terminal of the current comparison module; the N comparison input terminals of the current comparison module are connected one-to-one with the N detection terminals of the current detection module; N is a positive integer greater than 1; the N output terminals of the current comparison module are connected one-to-one with the N input terminals of the control module; the output terminal of the control module is connected to the control terminal of the current detection module; the enable terminal of the current detection module serves as the enable terminal of the overcurrent protection circuit; the output terminal of the current detection module serves as the output terminal of the overcurrent protection circuit; the current reference module, the current comparison module, the current detection module, and the control module are combined to enable the overcurrent protection circuit to generate N overcurrent thresholds, and different overcurrent thresholds can be adjusted by inputting an enable signal. When one of the overcurrent thresholds deviates due to process mismatch, the other overcurrent thresholds can also play a role in protecting the circuit, which can greatly reduce the static power consumption of the circuit and improve the reliability and stability of the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 This is a schematic diagram of an overcurrent protection circuit provided by the prior art;

[0068] Figure 2 This is a schematic diagram of an overcurrent protection circuit provided by the prior art;

[0069] Figure 3 Schematic diagram of an overcurrent protection circuit with an externally adjustable overcurrent threshold, provided by an embodiment of the present invention;

[0070] Figure 4 Schematic diagram of another overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention;

[0071] Figure 5 This is the simulation verification result of the overcurrent protection function of an overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention under a 0.25 μm BCD process;

[0072] Figure 6 This is the overcurrent protection process angle simulation result of an overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention under a 0.25 μm BCD process;

[0073] Figure 7 This is the functional simulation verification result of the input enable signal EN10 of an overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention in a 0.25μm BCD process;

[0074] Figure 8 This is the functional simulation verification result of the input enable signal EN20 of an overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention in a 0.25 μm BCD process;

[0075] Figure 9 This is the functional simulation verification result of the input enable signal EN40 of an overcurrent protection circuit with an externally adjustable overcurrent threshold provided by an embodiment of the present invention under a 0.25um BCD process. DETAILED DESCRIPTION

[0076] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0077] In this application, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0078] An embodiment of the present application provides an overcurrent protection circuit whose overcurrent threshold can be externally adjusted, which is used to solve the problem in the prior art that the bias current error of the constant current source controlled by the bias voltage is large when the temperature changes, thereby affecting the current threshold of the overcurrent protection circuit and reducing the circuit accuracy.

[0079] See also Figure 3 The overcurrent protection circuit with an externally adjustable overcurrent threshold includes: a current reference module, a current comparison module, a current detection module and a control module.

[0080] The power supply end of the current reference module, the power supply end of the current comparison module and the power supply end of the control module are all connected to a power supply.

[0081] The output terminal of the current reference module is connected to the reference input terminal of the current comparison module.

[0082] Specifically, the current reference module receives power supply, converts the power supply into a reference current, and transmits the reference current to the reference input terminal of the current comparison module.

[0083] The specific conversion process of the current reference module will not be described here in detail. It will depend on the actual situation and is within the scope of protection of this application.

[0084] The N comparison input terminals of the current comparison module are connected to the N detection terminals of the current detection module in a one-to-one correspondence. N is a positive integer greater than 1.

[0085] Specifically, N=3. Of course, N can also take other values, which will not be detailed here. It depends on the actual situation and is within the scope of protection of this application.

[0086] The N output terminals of the current comparison module are connected to the N input terminals of the control module in a one-to-one correspondence.

[0087] Specifically, the N output terminals of the current comparison module correspond one-to-one with the N input terminals of the control module. The first output terminal of the current comparison module is connected to the first input terminal of the control module; the second output terminal of the current comparison module is connected to the second input terminal of the control module, and so on. The Nth output terminal of the current comparison module is connected to the Nth input terminal of the control module. The case where N is greater than 2 is used for illustration. The case where N is equal to 2 is similar to the above case and will not be described in detail here. It can be determined according to the actual situation and is within the scope of protection of this application.

[0088] That is, the current comparator can output N control signals to the control module.

[0089] The output end of the control module is connected to the control end of the current detection module.

[0090] Specifically, the output end of the control module outputs a control signal to the current detection module. The control signals output by different modules are different, which will not be described here one by one. It depends on the actual situation and is within the protection scope of this application.

[0091] The enable terminal of the current detection module serves as the enable terminal of the overcurrent protection circuit.

[0092] That is, the enable terminal of the current detection module receives an enable signal; the enable signal may be used to control the state of the current detection module.

[0093] It should be noted that the current detection module includes N enable terminals, and can be combined with other modules to achieve adjustment at N overcurrent thresholds.

[0094] The output end of the current detection module serves as the output end of the overcurrent protection circuit.

[0095] That is to say, the current output by the current detection module is used as the current output by the overcurrent protection circuit, thereby controlling the current of the overcurrent protection circuit and preventing the protection device connected to the overcurrent protection circuit from being damaged by overcurrent.

[0096] In combination with the current comparison module, the current detection module and the control module, the overcurrent protection circuit generates N overcurrent thresholds.

[0097] That is to say, the overcurrent protection circuit can generate N overcurrent thresholds, and can also adjust different overcurrent thresholds through potential energy signals.

[0098] like Figure 3As shown, VDD and GND are the power supply and ground respectively; EN10\EN20\EN40 are the input enable signals, and the enable signals are valid at low level; OC10\OC20\OC40 are the overcurrent logic output signals, that is, the output signals of the current comparison module; OUT is the output terminal of the overall overcurrent protection circuit.

[0099] In this embodiment, the power supply end of the current reference module, the power supply end of the current comparison module and the power supply end of the control module are all connected to the power supply; the output end of the current reference module is connected to the reference input end of the current comparison module; the N comparison input ends of the current comparison module are connected one-to-one with the N detection ends of the current detection module; N is a positive integer greater than 1; the N output ends of the current comparison module are connected one-to-one with the N input ends of the control module; the output end of the control module is connected to the control end of the current detection module; the enable end of the current detection module serves as the enable end of the overcurrent protection circuit; the output end of the current detection module serves as the output end of the overcurrent protection circuit; combined with the current reference module, the current comparison module, the current detection module and the control module, the overcurrent protection circuit generates N overcurrent thresholds, and different overcurrent thresholds can also be adjusted by inputting an enable signal. When one of the overcurrent thresholds deviates due to process mismatch, the other overcurrent thresholds can also play a role in protecting the circuit, which can greatly reduce the static power consumption of the circuit and improve the reliability and stability of the circuit.

[0100] In practical applications, the current reference module includes a reference startup circuit and a reference generation circuit.

[0101] The first end of the reference startup circuit is connected to the first end of the reference generation circuit, and the connection point serves as the power supply end of the current reference module.

[0102] That is, the first terminal of the reference startup circuit and the first terminal of the reference generation circuit are both connected to a power supply.

[0103] The second terminal of the reference startup circuit and the second terminal of the reference generation circuit are both grounded.

[0104] That is, the second end of the reference startup circuit is connected to the second end of the reference generation circuit, and the connection point serves as the ground terminal of the current reference module and is grounded.

[0105] The third terminal of the reference startup circuit is connected to the third terminal of the reference generation circuit.

[0106] Specifically, the reference startup circuit can be used to start the reference generation circuit. The specific generation process will not be described here in detail. It depends on the actual situation and is within the scope of protection of this application.

[0107] In practical applications, see Figure 3The reference startup circuit includes: a first resistor R1, a first switch tube MN1 and a second switch tube MN2.

[0108] One end of the first resistor R1 serves as a first end of the reference startup circuit.

[0109] Specifically, one end of the first resistor R1 serves as the first end of the reference startup circuit and is connected to the power supply.

[0110] The other end of the first resistor R1 is respectively connected to the control end of the first switch tube MN1 , the first end of the first switch tube MN1 , the first end of the second switch tube MN2 , and the control end of the second switch tube MN2 .

[0111] The second terminal of the first switch tube MN1 serves as the third terminal of the reference startup circuit.

[0112] Specifically, the second end of the first switch tube MN1 serves as the third end of the reference startup circuit and is connected to the third end of the reference generation circuit.

[0113] The second end of the second switch tube MN2 serves as the second end of the reference startup circuit.

[0114] Specifically, the second end of the second switch tube MN2 serves as the second end of the reference startup circuit and is grounded.

[0115] In practical applications, see Figure 3 The reference generation circuit includes: a third switch tube MP1, a fourth switch tube MN4, a fifth switch tube MP2, a sixth switch tube MN3 and a second resistor R2.

[0116] The first end of the third switch transistor MP1 is connected to the first end of the fifth switch transistor MP2 , and the connection point serves as the first end of the reference generation circuit.

[0117] Specifically, the first end of the third switch tube MP1 and the first end of the fifth switch tube MP2 are respectively connected to the power supply.

[0118] The second end of the third switch transistor MP1 is connected to the control end of the sixth switch transistor MN3 and the first end of the fourth switch transistor MN4 respectively, and the connection point serves as the third end of the reference generation circuit.

[0119] Specifically, the second end of the third switch transistor MP1 is connected to the control end of the sixth switch transistor MN3 and the first end of the fourth switch transistor MN4 respectively, and the connection point serves as the third end of the reference generation circuit and is connected to the third end of the reference startup circuit.

[0120] More specifically, the second end of the first switch tube MN1 is connected to the second end of the third switch tube MP1 , the control end of the sixth switch tube MN3 , and the first end of the fourth switch tube MN4 , respectively.

[0121] The control end of the third switch tube MP1 is connected to the second end of the fifth switch tube MP2 , the control end of the fifth switch tube MP2 , and the first end of the sixth switch tube MN3 , respectively.

[0122] The second end of the sixth switch tube MN3 is connected to the control end of the fourth switch tube MN4 and one end of the second resistor R2 respectively.

[0123] The other end of the second resistor is connected to the second end of the fourth switch transistor MN4, and the connection point serves as the second end of the reference generation circuit.

[0124] Specifically, the other end of the second resistor and the second end of the fourth switch transistor MN4 are both grounded.

[0125] It should be noted that the third switch MP1, the fifth switch MP2, the sixth switch MN3, the fourth switch MN4, and the second resistor R2 constitute a reference generation structure. The size ratio of the switch MP1:MP2 is 1:1, so the currents flowing through the switch MP1 and MP2 are equal. The current I P1 The voltage V GSN4 , the current I of the fifth switch MP2 P2 The voltage generated by the second resistor R2 is I P2 *R2, since the voltages at the two points are equal, we can get:

[0126]

[0127] Among them, I P1 =I P2 , V THN4 is the threshold voltage of MN4, L N4 and W N4 are the channel length and width of MN4, μ n is the electron mobility, C ox is the oxide layer capacitance.

[0128] From the above formula, we can see that I P1 and I P2 The sensitivity to power supply VDD is essentially zero, meeting the reference current requirement. However, since this equation contains two possible degeneracy points—one required for normal circuit operation and the other the zero degeneracy point—the circuit requires a reference startup structure consisting of a first resistor R1, a first switch MN1, and a second switch MN2. When the circuit is powered on, the first switch MN1 provides current to the reference generation structure, allowing the circuit to escape the zero degeneracy point and achieve the required normal operation. Once the reference generation structure is operating normally, the source voltage of the first switch MN1 increases, causing the current in the first switch MN1 to decrease until it shuts down.

[0129] In practical applications, the current comparison module includes: N comparison circuits.

[0130] The reference input terminal of each comparison circuit is connected to the reference input terminal of the current comparison module.

[0131] Specifically, the reference input terminal of each comparison circuit receives a reference current.

[0132] The comparison input terminal of the comparison circuit serves as a comparison input terminal of the current comparison module.

[0133] Specifically, the comparison input terminals of the comparison circuit respectively receive the comparison currents of the current detection modules.

[0134] The current detection module can detect different comparison currents and then combine with other modules to achieve different overcurrent protection thresholds.

[0135] The output end of the comparison circuit serves as an output end of the current comparison module.

[0136] Specifically, the output end of the comparison circuit is connected to the corresponding input end of the control module, and outputs a control signal to the corresponding input end of the control module.

[0137] The power supply terminal of each comparison circuit is connected to the power supply terminal of the current comparison module.

[0138] Specifically, the power supply terminals of each comparison circuit are connected to a power supply.

[0139] The ground terminals of the respective comparison circuits are all grounded.

[0140] That is to say, the ground terminal of each comparison circuit serves as the ground terminal of the current comparison module.

[0141] In practical applications, see Figure 3 The comparison circuit includes: a seventh switch tube MP3, an eighth switch tube MN5, a ninth switch tube MP4, a tenth switch tube MN6, a third resistor R3 and a fourth resistor R4.

[0142] The control end of the seventh switch tube MP3 is connected to the control end of the ninth switch tube MP4 , and the connection point serves as a reference input end of the comparison circuit.

[0143] Specifically, the control end of the seventh switch tube MP3 is connected to the control end of the ninth switch tube MP4 , and the connection point is connected to the output end of the current reference module.

[0144] More specifically, a connection point between the control end of the seventh switch transistor MP3 and the control end of the ninth switch transistor MP4 is connected to a connection point between the control end of the third switch transistor MP1 and the control end of the fifth switch transistor MP2.

[0145] A first end of the seventh switch tube MP3 is connected to a first end of the ninth switch tube MP4 , and the connection point serves as a power supply end of the comparison circuit.

[0146] Specifically, the first end of the seventh switch tube MP3 and the first end of the ninth switch tube MP4 are both connected to the power supply.

[0147] The second end of the seventh switch transistor MP3 is respectively connected to the first end of the eighth switch transistor MN5 , the control end of the eighth switch transistor MN5 , and the control end of the tenth switch transistor MN6 .

[0148] The second end of the ninth switch tube MP4 is connected to the first end of the tenth switch tube MN6 , and the connection point serves as the output end of the comparison circuit.

[0149] That is, the connection point between the ninth switch tube MP4 and the tenth switch tube MN6 is connected to the corresponding input terminal of the control module.

[0150] A second end of the tenth switch tube MN6 is connected to one end of the fourth resistor R4 , and the connection point serves as a comparison input end of the comparison circuit.

[0151] Specifically, the connection point between the tenth switch tube MN6 and the fourth resistor R4 is connected to the corresponding detection terminal of the current detection module.

[0152] A second terminal of the eighth switch tube MN5 is connected to one terminal of the third resistor R3.

[0153] The other end of the fourth resistor R4 is connected to the other end of the third resistor R3 , and the connection point serves as a ground terminal of the comparison circuit.

[0154] Specifically, the other end of the fourth resistor R4 and the other end of the third resistor R3 are both grounded.

[0155] The above description uses the comparison circuit formed by the seventh switch tube MP3, the ninth switch tube MP4, the eighth switch tube MN5, the tenth switch tube MN6, the third resistor R3, and the fourth resistor R4 as an example; the comparison circuit formed by the switch tubes MP5, MP6, MN7, MN8 and the resistors R5 and R6, and the comparison circuit formed by the switch tubes MP7, MP8, MN9, MN10 and the resistors R7 and R8 are similarly described here and are all within the scope of protection of the present application.

[0156] It should be noted that the current comparison module has three independent comparison circuits. Among them, the comparison circuit with an overcurrent threshold of 10 A is composed of the seventh switching transistor MP3, the ninth switching transistor MP4, the eighth switching transistor MN5, the tenth switching transistor MN6, the third resistor R3, and the fourth resistor R4; the comparison circuit with an overcurrent threshold of 20 A is composed of the switching transistors MP5, MP6, MN7, MN8 and the resistors R5, R6; the comparison circuit with an overcurrent threshold of 40 A is composed of the switching transistors MP7, MP8, MN9, MN10 and the resistors R7, R8. Here, N is taken as 3 for display. At the same time, the values of each current are only examples and will not be elaborated here. It depends on the actual situation and is within the protection scope of the application.

[0157] Taking the comparison circuit with an overcurrent threshold of 10 A as an example, the size ratio of MP1:MP3:MP4 is A:1:1, and A < 1. Therefore, MP3 and MP4 amplify the reference current, enabling the current comparison module to have a certain current amplification ability and improving the comparison accuracy at the same time. MN5 and MN6 form a current mirror, and the size ratio of MN5:MN6 is p:q, and p < q. When there is no overcurrent, I N6 >I P4 , the operating state of MN6 changes from the saturation region to the linear region, and the logic signal OC10 outputs a low level; when an overcurrent occurs, the sampled current increases, causing the voltage drop across R4 to increase. Therefore, the source voltage of MN6 increases, the current flowing through MN6 decreases, I N6 <I P4 , the operating state of MP4 changes from the saturation region to the linear region, and the logic signal OC10 outputs a high level.

[0158] In this embodiment, the overcurrent protection circuit adopts a current comparison structure, so it does not require a complex bandgap reference circuit and bias circuit, reducing the design difficulty and the power consumption of the circuit. In addition, this structure has a certain current amplification ability and can improve the comparison accuracy; in addition, this structure has a certain current amplification ability and can improve the comparison accuracy.

[0159] It should be noted that the senseFET structure is adopted in the current detection module to sample the load current.

[0160] Specifically, in actual applications, the current detection module includes: N detection circuits and the eleventh switching transistor MN40V.

[0161] The control end of the detection circuit is connected to the control end of the eleventh switching transistor MN40V, and the connection point is used as the control end of the current detection module.

[0162] Specifically, the control ends of the detection circuit and the eleventh switching transistor MN40V are both connected to the output end of the control module.

[0163] The output end of the detection circuit is connected to the first end of the eleventh switch tube MN40V, and the connection point serves as the output end of the current detection module.

[0164] That is to say, the current at the connection point between the detection circuit and the eleventh switch tube MN40V serves as the output current of the overcurrent protection circuit.

[0165] The detection end of the detection circuit serves as a detection end of the current detection module.

[0166] The detection terminal of the detection circuit is used to detect a current value and transmit it to the corresponding comparison input terminal of the current comparison module.

[0167] Specifically, the detection terminals of the N detection circuits are connected to the comparison input terminals of the N comparison circuits in the current comparison module.

[0168] The enable terminal of the detection circuit serves as an enable terminal of the current detection module.

[0169] That is to say, the enable terminal of the detection circuit may receive an enable signal, and then the corresponding detection circuit may be selected for detection according to the enable signal, thereby realizing the selection of different overcurrent thresholds for protection.

[0170] The ground terminal of the detection circuit is grounded.

[0171] That is, the ground terminals of each detection circuit serve as the ground terminal of the current detection module.

[0172] In practical applications, the detection circuit includes: a sampling tube M1 and an enabling control tube MN11.

[0173] The first end of the sampling tube M1 serves as the output end of the detection circuit.

[0174] Specifically, the first end of the sampling tube M1 of each detection circuit serves as the output end of the current detection module.

[0175] That is, the current of the sampling tube M1 is the output current of the overcurrent protection circuit.

[0176] The control end of the sampling tube M1 serves as the control end of the detection circuit.

[0177] Specifically, the control end of the sampling tube M1 is connected to the output end of the control module.

[0178] The second end of the sampling tube M1 is connected to the first end of the enable control tube MN11, and the connection point serves as the detection end of the detection circuit.

[0179] Specifically, a connection point between the sampling tube M1 and the enable control tube MN11 is connected to a corresponding comparison input terminal of the current comparison module.

[0180] More specifically, the connection point between the sampling tube M1 and the enable control tube MN11 is connected to the connection point between the tenth switch tube MN6 and the fourth resistor R4.

[0181] The second terminal of the enable control transistor MN11 serves as the ground terminal of the detection circuit.

[0182] Specifically, the second end of the enable control end is grounded.

[0183] The control terminal of the enable control transistor MN11 serves as the enable terminal of the detection circuit.

[0184] Specifically, the control end of the enable control transistor MN11 receives the enable signal.

[0185] In practical applications, the enabling control transistor MN11 includes a built-in switch transistor or an external switch.

[0186] Specifically, such as Figure 3 As shown, when the enabling control tube MN11 is a built-in switch tube, the enabling control tube MN11 receives a control instruction from a host computer and performs a corresponding switching action according to the instruction.

[0187] like Figure 4 As shown, when the enable control tube MN11 is an external switch, it can be manually turned to realize the switch operation, thereby realizing the input enable signal. Of course, the external switch can be controlled by a controller to control the switch action. I will not go into details here. It depends on the actual situation and is within the scope of protection of this application. That is, Figure 4 The external switches S1, S2 and S3 are used as the enable control tube MN11 to replace Figure 3 MN11, MN12, and MN13.

[0188] The above description is made by taking the enabling control tube as MN11 and the sampling tube as M1 as an example. The enabling control tube as MN12 / MN13 and the sampling tube as M2 / M3 are similar. They will not be described one by one here. It depends on the actual situation and they are all within the protection scope of this application.

[0189] It should be noted that there are multiple sampling circuits in the current detection module that do not affect each other ( Figure 3 Take 3 as an example), where MN40V is a switch tube, M1 and MN11 are respectively a sampling tube with an overcurrent threshold of 10A and an enable control tube, M2 and MN12 are respectively a sampling tube with an overcurrent threshold of 20A and an enable control tube, M3 and MN13 are respectively a sampling tube with an overcurrent threshold of 40A and an enable control tube MN. Figure 3 MN40V shown) and sampling tube (as Figure 3 The M1, M2, and M3 shown in the figure are all power tubes, and the control tube (such as Figure 3MN11, MN12, and MN13 shown are low-voltage tubes. Let the parallel number ratio of the switching tube to the sampling tube be m:n, and m << n. For the power tube, ignoring the channel length modulation effect, its current I DS is as follows:

[0190]

[0191] where μ n is the electron mobility, C ox is the oxide capacitance, W and L are the channel width and length of the power tube respectively, V GS is the voltage between the gate and the source, and V TH is the threshold voltage.

[0192] It can be seen that under the same manufacturing process, the saturation current is related to the width-to-length ratio of the power tube and the voltage between the gate and the source. This circuit uses the senseFET structure to sample the load current, that is, connecting the gates and drains of the switching tube and the sampling tube together. Ignoring the slight voltage change at the source of the sampling tube, the ratio of the current flowing through the switching tube to the sampling current flowing through the sampling tube is the ratio of the number of parallel power tubes. Therefore, when the load current is too large, the sampling current also increases. When the enable signal is at a low level, the sampling current enters the current comparison module; when the enable signal is at a high level, the sampling current flows to the ground.

[0193] It should be noted that the traditional overcurrent threshold adjustment structure is as shown in Figure 2 This circuit samples the input voltage, uses this voltage as the control quantity, and adjusts the size of VS through an adjustment circuit. The adjusted VS is compared with the preset overcurrent protection reference voltage. If it exceeds the reference voltage, the overcurrent protection circuit starts to work. Therefore, the overcurrent protection circuit can ensure that the device is turned off before overcurrent, preventing the device from being damaged due to overcurrent. However, this design requires adding an additional adjustment circuit, a comparison circuit, a PWM control circuit, and a transformer on the basis of the overcurrent protection circuit, increasing the complexity of the circuit and also increasing the circuit power consumption. When the input voltage is large, the charging slope of the inductor current in the transformer increases, resulting in a delay in the loop, so that the power tube cannot be turned off in time during overcurrent, increasing the probability of overcurrent damage to the power tube and reducing the stability and reliability of the circuit.

[0194] In this embodiment, an overcurrent protection circuit is provided whose overcurrent threshold can be externally adjusted. The circuit can adjust different overcurrent thresholds by inputting an enable signal. At this time, only the circuit related to the selected overcurrent threshold works, which can greatly reduce the static power consumption of the circuit; the circuit adopts a senseFET structure to sample the load current. When it is detected that the load current is greater than the set overcurrent threshold, the circuit is turned off to protect the entire chip and the load; the circuit has three different overcurrent thresholds. When one of the overcurrent thresholds deviates due to process mismatch, the other overcurrent thresholds can also play a role in protecting the circuit, thereby improving the reliability and stability of the circuit.

[0195] In practical applications, such as Figure 3 As shown, the control module includes: an N-input comparator, a charging switch tube MP9, a ninth resistor R9 and N discharge switch tubes.

[0196] Figure 3 Take N=3 as an example for demonstration, where NM14, NM15, and NM16 are all discharge switch tubes.

[0197] The N input terminals of the N-input comparator are respectively connected to the N input terminals of the control module.

[0198] Specifically, the first input terminal of the N-input comparator is connected to the first input terminal of the control module; the second input terminal of the N-input comparator is connected to the second input terminal of the control module, and so on, the Nth input terminal of the N-input comparator is connected to the Nth input terminal of the control module.

[0199] More specifically, the first input terminal of the N-input comparator is connected to the first output terminal of the current comparison module; the second input terminal of the N-input comparator is connected to the second output terminal of the current comparison module, and so on, the Nth input terminal of the N-input comparator is connected to the Nth output terminal of the current comparison module.

[0200] The control ends of the N discharge switch tubes are respectively connected to the N input ends of the control module.

[0201] Specifically, taking N=3 as an example, the control end of the first discharge switch tube MN14 is connected to the first input end of the control module and receives the OC10 signal; the control end of the second discharge switch tube MN15 is connected to the second input end of the control module and receives the OC20 signal; the control end of the Nth discharge switch tube MN16 is connected to the Nth input end of the control module and receives the OC40 signal.

[0202] More specifically, the first control end of the discharge switch tube is connected to the first output end of the current comparison module; the second control end of the discharge switch tube is connected to the second output end of the current comparison module, and so on, the Nth control end of the discharge switch tube is connected to the Nth output end of the current comparison module.

[0203] The output terminal of the N-input comparator is connected to the control terminal of the charging switch tube MP9.

[0204] The first end of the charging switch tube MP9 serves as the power supply end of the control module.

[0205] Specifically, a first end of the charging switch tube MP9 is connected to a power source.

[0206] The second end of the charging switch tube MP9 is connected to one end of the ninth resistor R9 and the first ends of the N discharging switch tubes respectively.

[0207] The other end of the ninth resistor R9 serves as an output end of the control module.

[0208] Specifically, the other end of the ninth resistor R9 is connected to the control end of the current detection module.

[0209] In more detail, the other end of the ninth resistor R9 is connected to the control end of the eleventh switch tube MN40V and the control end of the sampling tube M1 in the current detection module respectively.

[0210] The second end of the discharge switch tube is grounded.

[0211] That is, the second end of each discharge switch tube serves as the grounding end of the control module.

[0212] Specifically, the first terminal of the discharge switch tube MN14 is connected to one terminal of the ninth resistor R9 and the second terminal of the charge switch tube MP9 respectively. The second terminal of the discharge switch tube MN14 is grounded. The control terminal of the discharge switch tube MN14 is connected to the corresponding output terminal of the current comparison module.

[0213] The above description is based on the discharge switch tube being MN14. The same is true for the discharge switch tubes being NM15 and NM16. Detailed descriptions will not be given here. Specific examples may be used depending on the actual situation. All of these are within the scope of protection of this application.

[0214] It should be noted that the control module consists of a three-input OR gate, MP9, MN14, MN15, MN16, and R9, and primarily includes charging and discharging branches. In the charging branch, when overcurrent is not occurring, OC10, OC20, and OC30 are all low, MP9 turns on, and the power supply charges the gate of the power transistor in the current sensing module. When overcurrent occurs, one of the signals in OC10, OC20, or OC30 goes high, MP9 turns off, and the charging branch shuts down. In the discharging branch, when overcurrent is not occurring, OC10, OC20, and OC30 are all low, MN14, MN15, and MN16 turn off, and the discharging branch shuts down. When overcurrent occurs, one of the signals in OC10, OC20, or OC30 goes high, turning on the corresponding transistor in MN14, MN15, or MN16, lowering the gate voltage of the power transistor and implementing the overcurrent protection circuit. R9 serves as the gate resistor for the power transistor, preventing it from turning on and off too quickly. Without a gate resistor, although the power consumption is small, it will cause the power tube to switch too quickly, resulting in voltage and current overshoot. However, if the resistance value of R9 is too large, the power consumption will be high, so the resistance value needs to be selected at a compromise.

[0215] In this embodiment, the overcurrent protection circuit has multiple different overcurrent thresholds, and can also control different overcurrent thresholds by inputting an enable signal. At this time, only the circuit related to the selected overcurrent threshold works, which can greatly reduce the static power consumption of the circuit and improve the reliability and stability of the circuit; since the senseFET structure is used to sample the load current, the generation of additional on-resistance and power consumption can be avoided; due to the current comparison structure used in the circuit, it has a certain current amplification capability and can improve the comparison accuracy.

[0216] The following uses experimental data to illustrate the overcurrent protection circuit provided by this application.

[0217] This design provides an overcurrent protection circuit with an externally adjustable overcurrent threshold. When the enable control signal is high, the overcurrent protection circuit is inoperative; when the enable control signal is low, the overcurrent protection circuit is operational. This design can adjust different overcurrent thresholds. If the desired overcurrent threshold is 10A, set the input enable signal EN10 to a low level, and EN20 and EN40 to high levels. When the load current is less than 10A, the overcurrent logic output signal OC10 is low, turning on the gate charging branch and turning off the gate discharging branch. When the load current is greater than 10A, the overcurrent logic output signal OC10 is high, turning off the gate charging branch and turning on the gate discharging branch, thus implementing the overcurrent protection function.

[0218] When the input enable signals EN10\EN20\EN40 are all low, the simulation results are as follows Figure 5As shown, the horizontal axis is the load current value and the vertical axis is the overcurrent logic output signal.

[0219] Among them, when the first output curve OC10 becomes a high level, it means the load current exceeds 10A; when the second output curve OC20 becomes a high level, it means the load current exceeds 20A; when the third output color curve OC40 becomes a high level, it means the load current exceeds 40A. The simulation results under different process angles are shown as follows. Figure 6 shown.

[0220] When the input enable signal EN10 is high, the overcurrent thresholds are 20A and 40A. The simulation results are as follows: Figure 7 shown.

[0221] When the input enable signal EN20 is high, the overcurrent thresholds are 10A and 40A. The simulation results are as follows: Figure 8 shown.

[0222] When the input enable signal EN40 is high, the overcurrent thresholds are 10A and 20A. The simulation results are as follows: Figure 9 shown.

[0223] This design can be applied to various intelligent power chip circuits that require overcurrent protection design. At the same time, it can also adjust different overcurrent thresholds according to application requirements to achieve detection and protection of chip load current.

[0224] The features described in the various embodiments of this specification can be replaced or combined with each other. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple. For relevant parts, refer to the partial description of the method embodiment. The system and system embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, 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 modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.

[0225] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0226] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An overcurrent protection circuit with an externally adjustable overcurrent threshold, characterized in that: include: Current reference module, current comparison module, current detection module and control module; The power supply terminal of the current reference module, the power supply terminal of the current comparison module and the power supply terminal of the control module are all connected to a power supply; The output terminal of the current reference module is connected to the reference input terminal of the current comparison module; The N comparison input terminals of the current comparison module are connected to the N detection terminals of the current detection module in a one-to-one correspondence; N is a positive integer greater than 1; The N output terminals of the current comparison module are connected to the N input terminals of the control module in a one-to-one correspondence; The output end of the control module is connected to the control end of the current detection module; The enable terminal of the current detection module serves as the enable terminal of the overcurrent protection circuit; The output end of the current detection module serves as the output end of the overcurrent protection circuit; In combination with the current reference module, the current comparison module, the current detection module and the control module, the overcurrent protection circuit generates N overcurrent thresholds; The current comparison module includes: N comparison circuits; The reference input terminal of each comparison circuit is connected to the reference input terminal of the current comparison module; The comparison input terminal of the comparison circuit serves as a comparison input terminal of the current comparison module; The output end of the comparison circuit serves as an output end of the current comparison module; The power supply terminal of each comparison circuit is connected to the power supply terminal of the current comparison module; The ground terminals of the comparison circuits are all grounded.

2. The overcurrent protection circuit with an externally adjustable overcurrent threshold according to claim 1, characterized in that: The current reference module includes: a reference startup circuit and a reference generation circuit; The first end of the reference startup circuit is connected to the first end of the reference generation circuit, and the connection point serves as the power supply end of the current reference module; The second end of the reference startup circuit and the second end of the reference generation circuit are both grounded; The third terminal of the reference startup circuit is connected to the third terminal of the reference generation circuit.

3. The overcurrent protection circuit with an externally adjustable overcurrent threshold according to claim 2, characterized in that: The reference startup circuit includes: a first resistor, a first switch tube and a second switch tube; One end of the first resistor serves as the first end of the reference startup circuit; The other end of the first resistor is respectively connected to the control end of the first switch tube, the first end of the first switch tube, the first end of the second switch tube, and the control end of the second switch tube; The second end of the first switch tube serves as the third end of the reference startup circuit; The second end of the second switch tube serves as the second end of the reference startup circuit.

4. The overcurrent protection circuit with an externally adjustable overcurrent threshold according to claim 2, characterized in that: The reference generation circuit includes: a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube and a second resistor; The first end of the third switch tube is connected to the first end of the fifth switch tube, and the connection point serves as the first end of the reference generation circuit; The second end of the third switch tube is connected to the control end of the sixth switch tube and the first end of the fourth switch tube respectively, and the connection point serves as the third end of the reference generation circuit; The control end of the third switch tube is respectively connected to the second end of the fifth switch tube, the control end of the fifth switch tube and the first end of the sixth switch tube; The second end of the sixth switch tube is connected to the control end of the fourth switch tube and one end of the second resistor respectively; The other end of the second resistor is connected to the second end of the fourth switch tube, and the connection point serves as the second end of the reference generation circuit.

5. The overcurrent protection circuit with externally adjustable overcurrent threshold according to claim 1, characterized in that: The comparison circuit includes: a seventh switching tube, an eighth switching tube, a ninth switching tube, a tenth switching tube, a third resistor and a fourth resistor; The control terminal of the seventh switch tube is connected to the control terminal of the ninth switch tube, and the connection point serves as the reference input terminal of the comparison circuit; The first end of the seventh switch tube is connected to the first end of the ninth switch tube, and the connection point serves as the power supply end of the comparison circuit; The second end of the seventh switch tube is respectively connected to the first end of the eighth switch tube, the control end of the eighth switch tube and the control end of the tenth switch tube; The second end of the ninth switch tube is connected to the first end of the tenth switch tube, and the connection point serves as the output end of the comparison circuit; The second end of the tenth switch tube is connected to one end of the fourth resistor, and the connection point serves as a comparison input end of the comparison circuit; The second end of the eighth switch tube is connected to one end of the third resistor; The other end of the fourth resistor is connected to the other end of the third resistor, and the connection point serves as the ground terminal of the comparison circuit.

6. The overcurrent protection circuit with externally adjustable overcurrent threshold according to claim 1, characterized in that: The current detection module includes: N detection circuits and an eleventh switch tube; The control end of the detection circuit is connected to the control end of the eleventh switch tube, and the connection point serves as the control end of the current detection module; The output end of the detection circuit is connected to the first end of the eleventh switch tube, and the connection point serves as the output end of the current detection module; The detection end of the detection circuit serves as a detection end of the current detection module; The enabling terminal of the detection circuit serves as an enabling terminal of the current detection module; The ground terminal of the detection circuit is grounded.

7. The overcurrent protection circuit with externally adjustable overcurrent threshold according to claim 6, characterized in that: The detection circuit includes: a sampling tube and an enabling control tube; The first end of the sampling tube serves as the output end of the detection circuit; The control end of the sampling tube serves as the control end of the detection circuit; The second end of the sampling tube is connected to the first end of the enabling control tube, and the connection point serves as the detection end of the detection circuit; The second end of the enabling control tube serves as the grounding end of the detection circuit; The control end of the enable control tube serves as the enable end of the detection circuit.

8. The overcurrent protection circuit with externally adjustable overcurrent threshold according to claim 7, characterized in that: The enabling control tube includes a built-in switch tube or an external switch.

9. The overcurrent protection circuit with externally adjustable overcurrent threshold according to claim 1, characterized in that: The control module includes: an N-input comparator, a charging switch tube, a ninth resistor and N discharge switch tubes; The N input terminals of the N-input comparator are respectively connected to the N input terminals of the control module; The control terminals of the N discharge switch tubes are respectively connected to the N input terminals of the control module; The output terminal of the N-input comparator is connected to the control terminal of the charging switch tube; The first end of the charging switch tube serves as the power supply end of the control module; The second end of the charging switch tube is respectively connected to one end of the ninth resistor and the first ends of the N discharge switch tubes; The other end of the ninth resistor serves as the output end of the control module; The second end of the discharge switch tube is grounded.

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