Overcurrent protection circuit

Abstract

The invention provides an overcurrent protection circuit, which comprises three main branches arranged in parallel, each main branch is provided with an upper resonant capacitor, a resonant inductor and an excitation inductor of a transformer; three over-current detection branches, the other end of each over-current detection branch is grounded, and each over-current detection branch is provided with a detection capacitor and a detection resistor; the input end of the first comparison module is connected with the three over-current detection branches, and the first comparison module is set to be that when the maximum current value of the three over-current detection branches is larger than a first preset value, the output level of the first comparison module is overturned; the input end of the second comparison module is connected with the three over-current detection branches, and the second comparison module is set to overturn the output level of the second comparison module when the minimum current value of the three over-current detection branches is smaller than a second preset value. Through the technical scheme provided by the invention, the technical problem that the cost of obtaining the resonance current by adopting a current transformer in the prior art is relatively high can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of overcurrent circuit protection, and in particular to an overcurrent protection circuit. Background Art

[0002] At present, in order to realize the overcurrent protection circuit of the circuit in the prior art, a three-phase LLC overcurrent protection circuit is generally used, and the three-phase LLC overcurrent protection circuit is provided with a CT (current transformer), and a current transformer is generally used to obtain the resonant current for overcurrent protection.

[0003] However, the cost of the current transformer is too high, which makes the overall cost of the overcurrent protection circuit high. Summary of the invention

[0004] The main purpose of the present invention is to provide an overcurrent protection circuit to solve the technical problem of high cost in obtaining resonant current by using a current transformer in the prior art.

[0005] In order to achieve the above object, the present invention provides an overcurrent protection circuit, comprising:

[0006] Three main branches are arranged in parallel, one end of the three main branches is connected to a DC power supply, the other end of the three main branches is grounded, and each main branch is provided with an upper resonant capacitor, a resonant inductor and an excitation inductor of a transformer;

[0007] Three overcurrent detection branches, the three overcurrent detection branches are arranged in one-to-one correspondence with the three main branches, one end of each overcurrent detection branch is connected to the corresponding main branch, the other end of each overcurrent detection branch is grounded, and each overcurrent detection branch is provided with a detection capacitor and a detection resistor;

[0008] A first comparison module, wherein an input end of the first comparison module is connected to the three overcurrent detection branches, and the first comparison module is configured to flip an output level of the first comparison module when the maximum current of the three overcurrent detection branches is greater than a first preset value;

[0009] A second comparison module, wherein an input end of the second comparison module is connected to the three overcurrent detection branches, and the second comparison module is configured to flip an output level of the second comparison module when a minimum current value of the three overcurrent detection branches is less than a second preset value;

[0010] The digital signal processor is connected to the output end of the first comparison module and the output end of the second comparison module so as to perform overcurrent protection through the digital signal processor.

[0011] Further, one end of each overcurrent detection branch is connected to a portion of the corresponding main branch located between the detection capacitor and the detection resistor, the capacitance value of the resonant capacitor is C1, and the capacitance value of the detection capacitor is C5;

[0012] Among them, C1≥50C5.

[0013] Furthermore, the overcurrent protection circuit also includes:

[0014] Three voltage-lifting branches, the three voltage-lifting branches are arranged one by one correspondingly to the three overcurrent detection branches, one end of each voltage-lifting branch is connected to the corresponding overcurrent detection branch, the other end of each voltage-lifting branch is connected to the first external power supply, and each voltage-lifting branch is provided with at least one voltage-lifting resistor;

[0015] The input end of the first comparison module is connected to the three voltage-boosting branches, and the input end of the second comparison module is connected to the three voltage-boosting branches.

[0016] Furthermore, two voltage-lifting resistors are arranged on each voltage-lifting branch, and a portion of each voltage-lifting branch located between the two voltage-lifting resistors is connected.

[0017] Furthermore, the overcurrent protection circuit also includes:

[0018] Three first connection branches, the three first connection branches are arranged in one-to-one correspondence with the three lifting and pressing branches, one end of each first connection branch is connected to the corresponding lifting and pressing branch, and the other end of each first connection branch is connected to the input end of the first comparison module;

[0019] Wherein, a first diode is arranged on the first connecting branch.

[0020] Furthermore, the overcurrent protection circuit also includes:

[0021] Three second connection branches, the three second connection branches are arranged in one-to-one correspondence with the three lifting and pressing branches, one end of each second connection branch is connected to the corresponding lifting and pressing branch, and the other end of each second connection branch is connected to the input end of the second comparison module;

[0022] A second diode is provided on the second connecting branch, and the current conduction direction of the second diode is opposite to that of the first diode.

[0023] Furthermore, the overcurrent protection circuit also includes:

[0024] The first external resistor is connected to the first comparison module, and the first external resistor is grounded.

[0025] Furthermore, the overcurrent protection circuit also includes:

[0026] A second external resistor, the second comparison module is connected to the second external resistor, and the second external resistor is connected to the second external power supply.

[0027] Furthermore, the overcurrent protection circuit also includes:

[0028] An isolator, one end of the isolator is connected to the output end of the first comparison module and the output end of the second comparison module, and the other end of the isolator is connected to the digital signal processor.

[0029] By applying the technical solution of the present invention, the detection capacitor and the detection resistor can obtain the current of the resonant inductor on the corresponding main branch, so that it is convenient to obtain the current of the resonant inductor on the corresponding main branch through the first comparison module through the corresponding overcurrent detection branch, so as to facilitate the acquisition of the current of the three main branches, so as to facilitate better judgment of whether there is an overcurrent situation and facilitate overcurrent protection. In addition, the overcurrent detection branch can obtain the current of the resonant inductor of the corresponding main branch only by the combination of the detection capacitor and the detection resistor. Compared with the method of obtaining the resonant current through the current transformer for overcurrent protection, the cost is low, the current structure is relatively simple, and the accuracy of overcurrent detection and judgment is also high. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 A schematic structural diagram of an overcurrent protection circuit provided according to an embodiment of the present invention is shown;

[0032] Figure 2 A schematic diagram showing the connection relationship between a first comparison module, a second comparison module and a digital signal processor provided according to an embodiment of the present invention is shown;

[0033] Figure 3 The voltage changes on three detection resistors on three overcurrent detection branches are shown;

[0034] Figure 4 The waveform diagram of the maximum voltage and the minimum voltage on the corresponding detection resistors of the three overcurrent detection branches is shown.

[0035] The above drawings include the following reference numerals:

[0036] 10. Main branch; 11. Resonant capacitor; 12. Resonant inductor; 13. Excitation inductor;

[0037] 20. Overcurrent detection branch; 21. Detection capacitor; 22. Detection resistor;

[0038] 30. First comparison module; 40. Second comparison module; 50. Digital signal processor;

[0039] 60. voltage lifting branch; 61. voltage lifting resistor;

[0040] 70. a first connecting branch; 71. a first diode;

[0041] 80. second connecting branch; 81. second diode;

[0042] 90. First external resistor; 100. Second external resistor; 110. Isolator; 120. First external power source; 130. Switch; 140. Transformer; 150. Load capacitor; 160. Load resistor; 170. Rectifier diode; 180. DC power source. DETAILED DESCRIPTION

[0043] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] like Figure 1 and 2 As shown, an embodiment of the present invention provides an overcurrent protection circuit, which includes: three main branches 10 arranged in parallel, three overcurrent detection branches 20, a first comparison module 30, a second comparison module 40 and a digital signal processor 50, one end of the three main branches 10 is connected to a DC power supply 180, the other end of the three main branches 10 is grounded, and each main branch 10 is provided with an upper resonant capacitor 11, a resonant inductor 12 and an excitation inductor 13 of a transformer 140. The three overcurrent detection branches 20 are arranged in a one-to-one correspondence with the three main branches 10, one end of each overcurrent detection branch 20 is connected to the corresponding main branch 10, the other end of each overcurrent detection branch 20 is grounded, and each overcurrent detection branch 20 is provided with a detection capacitor 21 and a detection resistor 22. The input end of the first comparison module 30 is connected to the three overcurrent detection branches 20, and the first comparison module 30 is configured to flip the output level of the first comparison module 30 when the maximum current of the three overcurrent detection branches 20 is greater than the first preset value. The input end of the second comparison module 40 is connected to the three overcurrent detection branches 20, and the second comparison module 40 is configured to flip the output level of the second comparison module 40 when the minimum current value of the three overcurrent detection branches 20 is less than the second preset value. The digital signal processor 50 is connected to the output end of the first comparison module 30 and the output end of the second comparison module 40, so as to perform overcurrent protection through the digital signal processor 50.

[0045] Specifically, the three main branches 10 correspond to three phases respectively. Correspondingly, the above-mentioned overcurrent protection circuit can be understood as an overcurrent protection circuit of a three-phase LLC. It should be noted that the first preset value is greater than the second preset value. It should be noted that the grounding point of the main branch 10 is different from the grounding point of the overcurrent detection branch 20.

[0046] The overcurrent protection circuit provided by the present embodiment is provided with three overcurrent detection branches 20, and each overcurrent detection branch 20 includes a detection capacitor 21 and a detection resistor 22. In this way, the detection capacitor 21 and the detection resistor 22 can obtain the current of the resonant inductor 12 on the corresponding main branch 10, so that it is convenient to obtain the current of the resonant inductor 12 on the corresponding main branch 10 through the corresponding overcurrent detection branch 20 through the first comparison module 30, so as to facilitate the acquisition of the current of the three main branches 10, so as to facilitate better judgment of whether there is an overcurrent situation, and facilitate overcurrent protection. In addition, the overcurrent detection branch 20 can obtain the current of the resonant inductor 12 of the corresponding main branch 10 only through the combination of the detection capacitor 21 and the detection resistor 22. Compared with the method of obtaining the resonant current through the current transformer for overcurrent protection, the cost is low, the current structure is relatively simple, and the accuracy of overcurrent detection and judgment is also high.

[0047] In this embodiment, one end of each overcurrent detection branch 20 is connected to the portion of the corresponding main branch 10 between the detection capacitor 21 and the detection resistor 22, the capacitance value of the resonant capacitor 11 is C1, and the capacitance value of the detection capacitor 21 is C5. Wherein, C1≥50C5. In this way, C1 can be much larger than C5, and the voltage across the detection capacitor 21 is much smaller than the voltage across the resonant capacitor 11.

[0048] like Figure 3 As shown, VR1, VR2 and VR3 are the voltages of the three detection resistors 22 of the three overcurrent detection branches 20, and iL1, iL2 and iL3 are the currents of the resonant inductors 12 of the corresponding three main branches 10. Figure 3 It can be seen that the waveforms of the voltages on the three detection resistors 22 are substantially consistent with the waveforms of the resonant current.

[0049] Specifically, the capacitance value of the detection capacitor 21 on one overcurrent detection branch 20 may be equal to or different from the capacitance value of the detection capacitor 21 on another overcurrent detection branch 20, and the resistance value of the detection resistor 22 on one overcurrent detection branch 20 may be equal to or different from the resistance value of the detection resistor 22 on another overcurrent detection branch 20.

[0050] In this embodiment, the overcurrent protection circuit also includes three voltage-lifting branches 60, and the three voltage-lifting branches 60 are arranged one by one corresponding to the three overcurrent detection branches 20. One end of each voltage-lifting branch 60 is connected to the corresponding overcurrent detection branch 20, and the other end of each voltage-lifting branch 60 is connected to the first external power supply 120. At least one voltage-lifting resistor 61 is arranged on each voltage-lifting branch 60. Among them, the input end of the first comparison module 30 is connected to the three voltage-lifting branches 60, and the input end of the second comparison module 40 is connected to the three voltage-lifting branches 60. With such a structural arrangement, it is convenient to lift the voltage of the corresponding overcurrent detection branch 20 through each voltage-lifting branch 60, so as to avoid the negative voltage of the AC voltage, so that the AC voltage is raised to a positive value as a whole, so as to facilitate the subsequent comparison by the comparison module.

[0051] Specifically, the first external power source 120 is also a DC power source.

[0052] Specifically, two lifting resistors 61 are provided on each lifting branch 60, and the portion of each lifting branch 60 located between the two lifting resistors 61 is connected. In this way, it is convenient to determine the lifting condition of the corresponding overcurrent detection branch 20 according to the resistance value of the two lifting resistors 61. Specifically, the resistance values ​​of the two lifting resistors 61 can be made equal, and when the power value of the first external power supply 120 is V_ref, the corresponding lifting resistance value is 0.5V_ref.

[0053] In this embodiment, the overcurrent protection circuit further includes three first connection branches 70, which are arranged one by one with the three boost branches 60, one end of each first connection branch 70 is connected to the corresponding boost branch 60, and the other end of each first connection branch 70 is connected to the input end of the first comparison module 30. Among them, a first diode 71 is arranged on the first connection branch 70. With such a structural arrangement, it is convenient to screen the flow direction of the current value, so that the first comparison module 30 can effectively obtain the maximum current value of the three detection branches.

[0054] Specifically, the overcurrent protection circuit also includes three second connection branches 80, which are arranged one by one with the three boost branches 60, one end of each second connection branch 80 is connected to the corresponding boost branch 60, and the other end of each second connection branch 80 is connected to the input end of the second comparison module 40. Among them, a second diode 81 is arranged on the second connection branch 80, and the current conduction direction of the second diode 81 is opposite to that of the first diode 71. In this way, it is convenient to screen the flow direction of the current, so that the second comparison module 40 can effectively obtain the minimum current value of the three detection branches.

[0055] Specifically, the relevant calculation process and formula are as follows. C1 is much larger than C5, and the voltage V across the detection resistor 22R1 is R1 Much smaller than the voltage V across C1 C1 .

[0056] For each overcurrent detection branch 20:

[0057] The current i of L1 L1 For: i L1 =C1*dV C1 / dt;

[0058] The voltage V across the detection resistor 22R1 R1 =V R1 =R1*C5*dV C1 / dt=R1*i L1 *C5 / C1;

[0059] Specifically, the voltage drops of the three first diodes 71 and the three second diodes 81 are all VF.

[0060] Specifically, the maximum voltage calculation formula of the first ratio module is as follows:

[0061] MAX_OCP=MAX(0.5*VR1+0.5*V_ref,0.5*VR2+0.5*V_ref,0.5*VR3+0.5*V_ref)-VF.

[0062] Specifically, the minimum voltage calculation formula of the second comparison module 40 is as follows:

[0063] MIN_OCP=MIN(0.5*VR1+0.5*V_ref,0.5*VR2+0.5*V_ref,0.5*VR3+0.5*V_ref)+VF.

[0064] Specifically, Figure 4 As shown, they are waveform diagrams of the maximum voltage and the minimum voltage on the corresponding detection resistors 22 on the three overcurrent detection branches 20 respectively.

[0065] In this embodiment, the overcurrent protection circuit further includes a first external resistor 90 , the first comparison module 30 is connected to the first external resistor 90 , and the first external resistor 90 is grounded.

[0066] In this embodiment, the overcurrent protection circuit further includes a second external resistor 100 , the second comparison module 40 is connected to the second external resistor 100 , and the second external resistor 100 is connected to a second external power source.

[0067] Specifically, the overcurrent protection circuit further includes an isolator 110, one end of which is connected to the output end of the first comparison module 30 and the output end of the second comparison module 40, and the other end of the isolator 110 is connected to the digital signal processor 50. In this way, it is possible to facilitate the sudden change of current or voltage to affect other parts and reduce interference.

[0068] Specifically, the overcurrent protection circuit in this embodiment also includes a switch 130, and one end of the main branch 10 is connected to the two ends of the DC power supply 180 through two switches 130. Specifically, the switch 130 can be a power electronic switch 130 tube or a bidirectional switch 130 tube, and the switch 130 specifically includes MOSFET, IGBT, GaN, triode, etc. The overcurrent protection circuit in this embodiment also includes a load circuit, which includes three transformers 140, a load capacitor 150 and a load resistor 160 arranged in parallel, and each transformer 140 is connected to the two ends of the load capacitor 150 arranged in parallel through two rectifier diodes 170, and the current flow directions of the two rectifier diodes 170 are opposite.

[0069] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: low cost, relatively simple current structure, and high accuracy of overcurrent detection and judgment.

[0070] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0071] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0072] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0073] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0074] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An overcurrent protection circuit, characterized in that: include: Three main branches (10) are arranged in parallel, one end of the three main branches (10) is connected to a DC power supply (180), the other end of the three main branches (10) is grounded, and each of the main branches (10) is provided with an upper resonant capacitor (11), a resonant inductor (12) and a transformer excitation inductor (13); Three overcurrent detection branches (20), the three overcurrent detection branches (20) being arranged in one-to-one correspondence with the three main branches (10), one end of each overcurrent detection branch (20) being connected to the corresponding main branch (10), the other end of each overcurrent detection branch (20) being grounded, and each overcurrent detection branch (20) being provided with a detection capacitor (21) and a detection resistor (22); A first comparison module (30), wherein an input end of the first comparison module (30) is connected to the three overcurrent detection branches (20), and the first comparison module (30) is configured such that when the maximum current of the three overcurrent detection branches (20) is greater than a first preset value, the output level of the first comparison module (30) is flipped; A second comparison module (40), wherein an input end of the second comparison module (40) is connected to the three overcurrent detection branches (20), and the second comparison module (40) is configured to flip an output level of the second comparison module (40) when a minimum current value of the three overcurrent detection branches (20) is less than a second preset value; A digital signal processor (50) is connected to an output end of the first comparison module (30) and an output end of the second comparison module (40) so as to perform overcurrent protection through the digital signal processor (50).

2. The overcurrent protection circuit according to claim 1, characterized in that: One end of each of the overcurrent detection branches (20) is connected to a portion of the corresponding main branch (10) located between the detection capacitor (21) and the detection resistor (22), the capacitance value of the resonant capacitor (11) is C1, and the capacitance value of the detection capacitor (21) is C5; Among them, C1≥50C5.

3. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent protection circuit further includes: Three voltage-lifting branches (60), the three voltage-lifting branches (60) being arranged in one-to-one correspondence with the three overcurrent detection branches (20), one end of each voltage-lifting branch (60) being connected to the corresponding overcurrent detection branch (20), the other end of each voltage-lifting branch (60) being connected to a first external power source (120), and each voltage-lifting branch (60) being provided with at least one voltage-lifting resistor (61); The input end of the first comparison module (30) is connected to the three voltage-boosting branches (60), and the input end of the second comparison module (40) is connected to the three voltage-boosting branches (60).

4. The overcurrent protection circuit according to claim 3, characterized in that: Two voltage-lifting resistors (61) are arranged on each of the voltage-lifting branches (60), and the portion of each of the voltage-lifting branches (60) located between the two voltage-lifting resistors (61) is connected.

5. The overcurrent protection circuit according to claim 3, characterized in that: The overcurrent protection circuit further includes: Three first connection branches (70), the three first connection branches (70) being arranged in one-to-one correspondence with the three pressure-lifting branches (60), one end of each of the first connection branches (70) being connected to the corresponding pressure-lifting branch (60), and the other end of each of the first connection branches (70) being connected to the input end of the first comparison module (30); Wherein, a first diode (71) is arranged on the first connecting branch (70).

6. The overcurrent protection circuit according to claim 5, characterized in that: The overcurrent protection circuit further includes: Three second connection branches (80), the three second connection branches (80) being arranged in one-to-one correspondence with the three boosting branches (60), one end of each second connection branch (80) being connected to the corresponding boosting branch (60), and the other end of each second connection branch (80) being connected to the input end of the second comparison module (40); A second diode (81) is provided on the second connecting branch (80), and the current conduction direction of the second diode (81) is opposite to that of the first diode (71).

7. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent protection circuit further includes: A first external resistor (90), the first comparison module (30) is connected to the first external resistor (90), and the first external resistor (90) is grounded.

8. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent protection circuit further includes: A second external resistor (100), the second comparison module (40) is connected to the second external resistor (100), and the second external resistor (100) is connected to a second external power source.

9. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent protection circuit further includes: An isolator (110), one end of the isolator (110) being connected to the output end of the first comparison module (30) and the output end of the second comparison module (40), and the other end of the isolator (110) being connected to the digital signal processor (50).

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