A protection circuit and inverter

Abstract

The utility model relates to the field of power electronics technology, and discloses a protection circuit and an inverter, wherein the inverter comprises: an inverter body, a drive circuit, a sampling circuit, a first switch circuit and a second switch circuit, wherein the sampling circuit, the first end of which is connected to the first end of the inverter body and the control end of the first switch circuit; the first switch circuit, the control end of which is connected to the second end of the second switch circuit, the first end of which is connected to the first end of the second switch circuit, the first power supply and the input end of the drive circuit, and the second end of which is connected to the control end of the second switch circuit and then grounded; the drive circuit, the output end of which is connected to the control end of the inverter body. The utility model can quickly block the drive when the inverter is overcurrent in both positive and negative directions, ensuring that the inverter bridge arm will not be damaged due to overcurrent, and has a simple circuit structure and low cost.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to a protection circuit and an inverter. Background Art

[0002] The inverter bridge arm current detection usually uses resistor voltage division, and then obtains the appropriate current sampling signal through the operational amplifier, and sends the current sampling signal to the comparator for overcurrent detection. When the inverter has overcurrent, the comparator outputs an overcurrent protection signal to drive the blockade. Since this method uses many components, the circuit is complex, the response speed is slow, and an additional power supply needs to be introduced as the overcurrent comparison threshold. If negative current needs to be detected, a reference source needs to be introduced for voltage boosting, which increases the circuit cost. Utility Model Content

[0003] Therefore, the technical problem to be solved by the present invention is to solve the problems of slow response speed and high cost of the bidirectional overcurrent protection circuit in the prior art, thereby providing a protection circuit and an inverter.

[0004] In order to achieve the above object, the utility model provides the following technical solutions:

[0005] In a first aspect, the utility model provides a protection circuit, comprising: a sampling circuit, a first switch circuit and a second switch circuit, wherein the sampling circuit has a first end connected to the first end of a device to be protected and a control end of the first switch circuit, and a second end connected to the second end of the device to be protected and then grounded, and after a potential difference is generated between the first end and the second end under the action of the output current of the device to be protected, the voltage at the first end is a sampling voltage; the first switch circuit has a control end connected to the second end of the second switch circuit, a first end connected to the first end of the second switch circuit and the control end of the device to be protected, and a second end connected to the control end of the second switch circuit and then grounded; when the sampling voltage is a positive voltage and the sampling voltage is greater than the conduction voltage drop of the first switch circuit, after the first switch circuit is turned on and the second switch circuit is turned off, the first switch circuit controls the device to be protected to be blocked and driven; when the sampling voltage is a negative voltage and the absolute value of the sampling voltage is greater than the conduction voltage drop of the second switch circuit, after the second switch circuit is turned on and the first switch circuit is turned off, the second switch circuit controls the device to be protected to be blocked and driven.

[0006] The protection circuit provided by the utility model can trigger the first switch circuit or the second switch circuit to conduct when the sampling voltage exceeds the conduction voltage drop of the first switch circuit or the second switch circuit, regardless of whether the sampling voltage is a positive voltage or a negative voltage, so that the signal state of the control end of the device to be protected changes to turn off the drive. Therefore, the utility model can quickly realize bidirectional overcurrent protection for the device to be protected only when the sampling voltage reaches the conduction voltage drop of the first switch circuit or the second switch circuit without introducing an additional power supply as an overcurrent comparison threshold. The overcurrent protection response speed is fast and the circuit cost is low.

[0007] In an optional implementation, the sampling circuit includes: a sampling resistor, a first end of which is connected to a first end of the device to be protected, and a second end of which is connected to a second end of the device to be protected.

[0008] In an optional embodiment, the first switch circuit includes: a first switch, whose control end is connected to the first end of the sampling circuit and the second end of the second switch circuit, whose first end is connected to the first end of the second switch circuit and the first power supply, and whose second end is connected to the control end of the second switch circuit; when the sampling voltage is a positive voltage and the sampling voltage is greater than the on-state voltage drop of the first switch, the first switch is turned on and the second switch circuit is turned off; when the sampling voltage is a negative voltage and the absolute value of the sampling voltage is greater than the on-state voltage drop of the second switch circuit, the second switch circuit is turned on and the first switch is turned off.

[0009] In an optional embodiment, the second switch circuit includes: a second switch, whose control end is connected to the second end of the first switch, whose first end is connected to the first end of the first switch, and whose second end is connected to the control end of the first switch; when the sampling voltage is a positive voltage and the sampling voltage is greater than the on-state voltage drop of the first switch, the first switch is turned on and the second switch is turned off; when the sampling voltage is a negative voltage and the absolute value of the sampling voltage is greater than the on-state voltage drop of the second switch circuit, the second switch is turned on and the first switch is turned off.

[0010] In the protection circuit provided by the utility model, the first switch circuit and the second switch circuit each include only one switch, and the circuit structure is simple, which further improves the response speed of the first switch circuit and the second switch circuit and reduces the circuit cost.

[0011] In an optional implementation, the protection circuit further includes: a first current limiting circuit, a first end of which is connected to the first end of the sampling circuit, and a second end of which is connected to the control end of the first switch circuit, and is used to limit the current output by the sampling circuit.

[0012] In an optional implementation, the protection circuit further includes: a second current limiting circuit, a first end of which is connected to the first power supply, and a second end of which is connected to the first end of the first switch circuit, and is used to limit the current output by the first power supply.

[0013] The protection circuit provided by the utility model, the first current limiting circuit and the second current limiting circuit can limit the current flowing into the first switch circuit and the second switch circuit, avoid the impact current in the first power supply and the protected equipment to damage the first switch circuit and the second switch circuit, and improve the service life of the protection circuit.

[0014] In a second aspect, the present invention provides an inverter, comprising: an inverter body, a drive circuit and the protection circuit of the first aspect, wherein the inverter body, a control end thereof is connected to the output end of the drive circuit, a first end thereof is connected to the first end of the sampling circuit, and a second end thereof is connected to the second end of the sampling circuit; the drive circuit, an input end thereof is connected to the first end of the first switch circuit; when the sampling voltage at the first end of the inverter body is a positive voltage, and the sampling voltage is greater than the conduction voltage drop of the first switch circuit, the drive circuit blocks the inverter body drive after the first switch circuit is turned on and the second switch circuit is turned off; when the sampling voltage at the detection end of the inverter body is a negative voltage, and the absolute value of the sampling voltage is greater than the conduction voltage drop of the second switch circuit, the drive circuit blocks the inverter body drive after the second switch circuit is turned on and the first switch circuit is turned off.

[0015] The inverter provided by the utility model can trigger the first switch circuit or the second switch circuit to conduct, and switch the level signal state of the input end of the drive circuit, regardless of whether the sampling voltage is a positive voltage or a negative voltage, when the sampling voltage exceeds the conduction voltage drop of the first switch circuit or the second switch circuit, so that the drive circuit blocks the drive of the inverter body.

[0016] The utility model does not need to introduce an additional power supply as the overcurrent comparison threshold. The on-state voltage drop of the first switch circuit and the second switch circuit is used as the overcurrent comparison threshold. When the sampling voltage reaches the on-state voltage drop of the first switch circuit or the second switch circuit, bidirectional overcurrent protection for the inverter can be quickly achieved, with fast response speed and low circuit cost.

[0017] In an optional embodiment, the inverter body includes: a full-bridge inverter unit and a support capacitor, wherein the full-bridge inverter unit has a first end connected to the second power supply and the first end of the support capacitor, a second end connected to the first end of the sampling circuit, and a control end connected to the output end of the drive circuit, and is used to switch the switch state based on the switch sequence output by the drive circuit; the support capacitor has a second end connected to the second end of the sampling circuit, and is used to maintain the stability of the second power supply; the full-bridge inverter unit has different directions of bridge arm current flowing through the sampling circuit in different switching states; when the bridge arm current flows from the first end of the sampling circuit to its second end, the first end of the sampling circuit is a positive voltage and the second end is a negative voltage; when the bridge arm current flows from the second end of the sampling circuit to its first end, the first end of the sampling circuit is a negative voltage and the second end is a positive voltage.

[0018] In an optional embodiment, the full-bridge inverter unit includes: a first power device, a second power device, a third power device and a fourth power device, wherein the first power device, a first end of which is connected to the third power device, the first end of the supporting capacitor and the second power supply, and a second end of which is connected to the first end of the second power device and the first end of the load; the second power device, a second end of which is connected to the second end of the fourth power device and the first end of the load; the third power device, a second end of which is connected to the first end of the fourth power device and the second end of the load; the control ends of the first power device, the second power device, the third power device and the fourth power device are all connected to the output end of the drive circuit; when the first power device and the fourth power device are turned on and the second power device and the third power device are turned off, or when the second power device and the third power device are turned on and the first power device and the fourth power device are turned off, the bridge arm current flows from the first end of the sampling circuit to its second end; when the first power device, the second power device, the third power device and the fourth power device are all turned off, the bridge arm current flows from the second end of the sampling circuit to its first end.

[0019] In an optional implementation, the first power device, the second power device, the third power device and the fourth power device are all composed of a fully controlled power device and a diode connected in reverse parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A composition diagram of a specific example of a protection circuit according to an embodiment of the utility model;

[0022] Figure 2 A structural diagram of a specific circuit of the protection circuit of an embodiment of the utility model;

[0023] Figure 3 A composition diagram of a specific example of an inverter according to an embodiment of the utility model;

[0024] Figure 4 The figure is a structural diagram of a specific circuit of an inverter according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0025] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0028] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] In the related art, the overcurrent protection circuit needs to introduce an additional power supply as the overcurrent comparison threshold, which leads to a complex circuit structure and high cost. In addition, since the sampled current needs to be compared with the thresholds in two directions, the overcurrent protection circuit has a slow response speed. To solve the above problems, this embodiment provides a protection circuit 1, such as Figure 1 As shown, it includes: a first switch circuit 11, a second switch circuit 12 and a sampling circuit 13.

[0030] Figure 1 In the example, the sampling circuit 13 has a first end connected to the first end of the device to be protected and the control end of the first switch circuit 11, and a second end connected to the second end of the device to be protected and then grounded. After a potential difference is generated between the first end and the second end under the action of the output current of the device to be protected, the voltage at the first end is the sampling voltage, which is the voltage borne by the device to be protected.

[0031] For example, Figure 1 In the embodiment, after the current at the first end of the device to be protected flows through the sampling circuit 13, a voltage drop is generated at both ends of the sampling circuit 13. After the current flows through the sampling circuit 13, the voltage direction applied by the sampling circuit 13 to the first switch circuit 11 or the second switch circuit 12 can be positive or negative. Therefore, the voltage conditions borne by the sampling circuit 13 are the following two: the voltage at the first end of the sampling circuit 13 is positive and the voltage at the second end is negative, or the voltage at the first end of the sampling circuit 13 is negative and the voltage at the second end is positive.

[0032] Figure 1 In the embodiment, the first switch circuit 11 has a control end connected to the second end of the second switch circuit 12, a first end connected to the first end of the second switch circuit 12 and the control end of the device to be protected, and a second end connected to the control end of the second switch circuit 12 and then grounded.

[0033] Specifically, Figure 1 There are three cases for sampling voltage:

[0034] (1) When the first end of the sampling circuit 13 has no sampling voltage due to a fault, maintenance or other reasons of the device to be protected, the protection circuit 1 does not function. At this time, both the first switch circuit 11 and the second switch circuit 12 remain in the off state.

[0035] (2) When the absolute value of the sampled voltage is less than the conduction voltage drop of the first switch circuit 11 and the second switch circuit 12, it is determined that no overcurrent occurs in the device to be protected. At this time, the overcurrent protection action is not triggered, and the first switch circuit 11 and the second switch circuit 12 both remain in the off state. The control terminal level of the device to be protected remains unchanged, and the device to be protected maintains the original working state. Optionally, for different devices to be protected, the original working state can be maintained unchanged, or the power supply can be maintained, but this is just an example and is not intended to be limiting.

[0036] (3) When the sampling voltage is a positive voltage and the sampling voltage is greater than the on-state voltage drop of the first switch circuit 11, it is determined that an overcurrent occurs in the device to be protected. At this time, after the first switch circuit 11 is turned on and the second switch circuit 12 is turned off, the first end of the first switch circuit 11 switches the level state, so that the control end of the device to be protected turns off the drive based on the current level state, or after the protection circuit 1 directly cuts off the power supply line to be protected, the device to be protected stops working to prevent internal components from being damaged by large current.

[0037] (4) When the sampled voltage is a negative voltage and the absolute value of the sampled voltage is greater than the on-state voltage drop of the second switch circuit 12, it is determined that an overcurrent occurs in the device to be protected. At this time, after the second switch circuit 12 is turned on and the first switch circuit 11 is turned off, the first end of the second switch circuit 12 switches the level state, so that the control end of the device to be protected turns off the drive based on the current level state, or after the protection circuit 1 directly cuts off the power supply line of the device to be protected, the device to be protected stops working to prevent internal components from being damaged by large current.

[0038] Optionally, the linkage state between the first switch circuit and the second switch circuit of this embodiment can be set according to actual needs and is not limited to the above action flow.

[0039] It should be noted that the first switch circuit 11 and the second switch circuit 12 are both structures that are turned on when subjected to a forward voltage and the forward voltage is greater than a certain threshold, and are turned off when subjected to a reverse voltage, or other structures that can be alternately turned on when the sampling voltage is positive or negative and the voltage exceeds a certain threshold. The two can be composed of transistors, and there is no limitation here.

[0040] The protection circuit provided in this embodiment can trigger the first switch circuit or the second switch circuit to conduct when the sampled voltage exceeds the conduction voltage drop of the first switch circuit or the second switch circuit, so that the signal state of the control terminal of the device to be protected changes to turn off the drive, regardless of whether the sampled voltage is a positive voltage or a negative voltage. This embodiment does not need to introduce an additional power supply as an overcurrent comparison threshold, and when the sampled voltage reaches the conduction voltage drop of the first switch circuit or the second switch circuit, bidirectional overcurrent protection can be quickly achieved for the device to be protected, with fast response speed and low circuit cost.

[0041] In some optional embodiments, such as Figure 2 As shown, the sampling circuit 13 includes: a sampling resistor Rs, a first end of which is connected to the first end of the device to be protected, and a second end of which is connected to the second end of the device to be protected.

[0042] Specifically, Figure 2 When the current of the device to be protected flows from the first end of the sampling resistor Rs to its second end, the voltage at the first end of the sampling resistor Rs is positive and the voltage at the second end is negative; when the current of the device to be protected flows from the second end of the sampling resistor Rs to its first end, the voltage at the first end of the sampling resistor Rs is negative and the voltage at the second end is positive.

[0043] Optionally, the sampling circuit 13 is a component that can generate positive and negative voltages at both ends of the sampling circuit 13 when the current of the device to be protected flows through the sampling circuit 13 . The sampling circuit 13 may include other linear components such as capacitors and inductors.

[0044] In some optional embodiments, such as Figure 2As shown, the first switch circuit 11 includes: a first switch Q1, whose control end is connected to the first end of the sampling circuit 13 and the second end of the second switch circuit 12, whose first end is connected to the first end of the second switch circuit 12 and the first power supply Vcc, and whose second end is connected to the control end of the second switch circuit 12, wherein the first switch Q1 takes a transistor as an example, but this is only an example and is not intended to be limiting.

[0045] Alternatively, if Figure 2 As shown, the protection circuit 1 further includes: a first current limiting circuit 14 , a first end of which is connected to the first end of the sampling circuit 13 , and a second end of which is connected to the control end of the first switch circuit 11 , and is used to limit the current output by the sampling circuit 13 .

[0046] Alternatively, if Figure 2 As shown, the protection circuit 1 further includes: a second current limiting circuit 15, a first end of which is connected to the first power supply Vcc, and a second end of which is connected to the first end of the first switch circuit 11, and is used to limit the current output by the first power supply Vcc.

[0047] Specifically, Figure 2 When the first end of the sampling circuit 13 has no sampling voltage due to a fault, maintenance or other reasons of the protected device, the protection circuit 1 does not function, and the first switch Q1 and the second switch circuit 12 both remain in the off state.

[0048] Specifically, Figure 2 When the absolute value of the sampled voltage does not exceed the conduction voltage drop of the first switch Q1 and the second switch circuit 12, it is determined that no overcurrent occurs in the device to be protected. At this time, the overcurrent protection action is not triggered, and the control end of the device to be protected maintains the original level state, that is, the original driving state of the device to be protected is maintained unchanged.

[0049] Specifically, Figure 2 When the sampling voltage is a positive voltage and is greater than the on-state voltage drop of the first switch Q1, it is determined that an overcurrent occurs in the device to be protected. At this time, after the first switch Q1 is turned on and the second switch circuit 12 is turned off, the first end of the first switch Q1 outputs a low-level signal to the control end of the device to be protected, thereby blocking the drive of the device to be protected.

[0050] Specifically, Figure 2 In the embodiment, when the sampling voltage is a negative voltage and the absolute value of the sampling voltage is greater than the on-state voltage drop of the second switch circuit 12, it is determined that an overcurrent occurs in the device to be protected. At this time, the second switch circuit 12 is turned on and the first switch Q1 is turned off. The first end of the second switch circuit 12 outputs a low-level signal to the control end of the device to be protected, thereby blocking the drive of the device to be protected.

[0051] Optionally, Figure 2In the embodiment, the low level signal output by the first switch Q1 or the second switch circuit 12 can also control the switch or circuit breaker on the power supply line of the device to be protected to disconnect, so that the device to be protected is powered off and stops working, avoiding internal overcurrent damaging components.

[0052] In some optional embodiments, the second switch circuit 12 includes: a second switch Q2, whose control end is connected to the second end of the first switch Q1, whose first end is connected to the first end of the first switch Q1, and whose second end is connected to the control end of the first switch Q1, wherein the second switch Q2 takes a transistor as an example, but this is only an example and is not intended to be limiting.

[0053] Specifically, Figure 2 When the first end of the sampling circuit 13 has no sampling voltage due to a failure or maintenance of the protected device, the protection circuit 1 does not function, and the first switch Q1 and the second switch Q2 both remain in the off state.

[0054] Specifically, Figure 2 When the absolute value of the sampled voltage does not exceed the conduction voltage drop of the first switch Q1 and the second switch Q2, it is determined that no overcurrent occurs in the device to be protected. At this time, the overcurrent protection action is not triggered, and the control end of the device to be protected maintains the original level state, that is, the original driving state of the device to be protected is maintained unchanged.

[0055] Specifically, Figure 2 In the embodiment, when the sampling voltage is a positive voltage and the sampling voltage is greater than the on-state voltage drop of the first switch Q1, it is determined that an overcurrent occurs in the device to be protected. At this time, after the first switch Q1 is turned on and the second switch Q2 is turned off, the first end of the first switch Q1 outputs a low-level signal to the control end of the device to be protected, thereby blocking the drive of the device to be protected.

[0056] Specifically, Figure 2 In the embodiment, when the sampling voltage is a negative voltage and the absolute value of the sampling voltage is greater than the on-state voltage drop of the second switch Q2, it is determined that an overcurrent occurs in the device to be protected. At this time, after the second switch Q2 is turned on and the first switch Q1 is turned off, the first end of the second switch Q2 outputs a low-level signal to the control end of the device to be protected, thereby blocking the drive of the device to be protected.

[0057] Optionally, Figure 2 In the embodiment, the low level signal output by the first switch Q1 or the second switch Q2 can also control the switch or circuit breaker on the power supply line of the device to be protected to disconnect, so that the device to be protected is powered off and stops working, avoiding internal overcurrent damaging components.

[0058] It should be noted that when the device to be protected works normally, the level state of its control terminal is not restricted here.

[0059] It should be noted that the first switch Q1 and the second switch Q2 can be transistors, MOS transistors, IGBTs, etc., and the types and quantities are not limited here.

[0060] This embodiment provides an inverter, such as Figure 3 As shown, it includes: an inverter body 2, a drive circuit 3 and a protection circuit 1 of the above embodiment and any optional implementation manner thereof.

[0061] Figure 3 In the embodiment, the inverter body 2 has a control end connected to the output end of the drive circuit 3, a first end connected to the first end of the sampling circuit 13, and a second end connected to the second end of the sampling circuit 13; the drive circuit 3 has an input end connected to the first end of the first switch circuit 11.

[0062] Specifically, Figure 3 When the absolute value of the sampling voltage at the first end of the inverter body 2 is less than the conduction voltage drop of the first switch circuit 11 and the second switch circuit 12, the input level signal of the drive circuit 3 does not change, and the drive circuit 3 drives the inverter body 2 to work normally based on the current level signal.

[0063] Specifically, Figure 3 In the embodiment, when the sampling voltage at the first end of the inverter body 2 is a positive voltage and the sampling voltage is greater than the conduction voltage drop of the first switch circuit 11, after the first switch circuit 11 is turned on and the second switch circuit 12 is turned off, the input end of the drive circuit 3 switches the level state, so that the drive circuit 3 is in a disabled state, stops driving the inverter body 2, and the inverter body 2 stops working.

[0064] Specifically, Figure 3 In the embodiment, when the sampling voltage at the detection end of the inverter body 2 is a negative voltage and the absolute value of the sampling voltage is greater than the conduction voltage drop of the second switch circuit 12, after the second switch circuit 12 is turned on and the first switch circuit 11 is turned off, the input end of the drive circuit 3 switches the level state, so that the drive circuit 3 is in a disabled state, stops driving the inverter body 2, and the inverter body 2 stops working.

[0065] The inverter provided in this embodiment, regardless of whether the sampling voltage is a positive voltage or a negative voltage, can trigger the first switch circuit or the second switch circuit to conduct and switch the level signal state of the input end of the drive circuit when the sampling voltage exceeds the conduction voltage drop of the first switch circuit or the second switch circuit, so that the drive circuit blocks the drive of the inverter body. This embodiment does not need to introduce an additional power supply as an overcurrent comparison threshold. When the sampling voltage reaches the conduction voltage drop of the first switch circuit or the second switch circuit, bidirectional overcurrent protection of the inverter can be quickly achieved, with fast response speed and low circuit cost.

[0066] In some optional embodiments, such as Figure 4As shown, the inverter body 2 includes: a full-bridge inverter unit 21 and a support capacitor C1, wherein the first end of the full-bridge inverter unit 21 is connected to the second power supply Vbus and the first end of the support capacitor C1, the second end is connected to the first end of the sampling circuit 13, and the control end is connected to the output end of the drive circuit 3, which is used to switch the switch state based on the switch sequence output by the drive circuit 3; the direction of the bridge arm current flowing through the sampling circuit 13 of the full-bridge inverter unit 21 is different in different switching states. Figure 4 In the embodiment, the supporting capacitor C1 has a second end connected to the second end of the sampling circuit 13, and is used to maintain the stability of the second power supply Vbus.

[0067] like Figure 4 As shown, the full-bridge inverter unit 21 includes: a first power device 211 , a second power device 212 , a third power device 213 and a fourth power device 214 .

[0068] like Figure 4 As shown, the first power device 211 has a first end connected to the first end of the third power device 213, the first end of the support capacitor and the second power source, and a second end connected to the first end of the second power device 212 and the first end of the load.

[0069] like Figure 4 As shown, the second end of the second power device 212 is connected to the second end of the fourth power device 214 and the first end of the load.

[0070] like Figure 4 As shown, the second end of the third power device 213 is connected to the first end of the fourth power device 214 and the second end of the load.

[0071] like Figure 4 As shown, the control ends of the first power device 211 , the second power device 212 , the third power device 213 and the fourth power device 214 are all connected to the output end of the driving circuit.

[0072] like Figure 4 As shown, when the first power device 211 and the fourth power device 214 are turned on and the second power device 212 and the third power device 213 are turned off, or the second power device 212 and the third power device 213 are turned on and the first power device 211 and the fourth power device 214 are turned off, the bridge arm current flows from the first end of the sampling circuit to the second end thereof.

[0073] like Figure 4 As shown, when the first power device 211 , the second power device 212 , the third power device 213 and the fourth power device 214 are all turned off, the bridge arm current flows from the second end of the sampling circuit to the first end thereof.

[0074] like Figure 4As shown, the first power device 211, the second power device 212, the third power device 213 and the fourth power device 214 are all composed of fully controlled power devices and diodes connected in reverse parallel: the first power device 211 is composed of a third switch Q3 and a first diode D1, the second power device 212 is composed of a fourth switch Q4 and a second diode D2, the third power device 213 is composed of a fifth switch Q5 and a third diode D3, and the fourth power device 214 is composed of a sixth switch Q6 and a first diode D1.

[0075] For example, Figure 4 In the example, the bridge arm current in the inverter body 2 has the following two flow directions:

[0076] (1) When the bridge arm current passes through Vbus→Q3→Q6→Rs→GND, or passes through Vbus→Q5→Q4→Rs→GND, a voltage with a positive top and a negative bottom is generated at both ends of Rs. When the voltage at the first end of Rs is greater than the conduction voltage drop of the first switch Q1, after the first switch Q1 is turned on and the second switch Q2 is turned off, the first end of the first switch Q1 outputs a low-level signal to the input end of the drive circuit 3, so that the drive circuit 3 is disabled and stops driving the third switch Q3 to the sixth switch Q6, thereby achieving the purpose of blocking the drive of the inverter body 2.

[0077] (2) When the bridge arm current passes through D3→Vbus→C1→GND→D2, or through D1→Vbus→C1→GND→D4, a voltage with a negative top and a positive bottom is generated at both ends of Rs. When the absolute value of the voltage at the first end of Rs is greater than the conduction voltage drop of the second switch Q2, after the second switch Q2 is turned on and the first switch Q1 is turned off, the first end of the second switch Q2 outputs a low-level signal to the input end of the drive circuit 3, so that the drive circuit 3 is disabled and stops driving the third switch Q3 to the sixth switch Q6, thereby achieving the purpose of blocking the drive of the inverter body 2.

[0078] It should be noted that, in this embodiment, the full-bridge inverter unit 21 takes a single-phase full-bridge structure as an example, and it can also be a three-phase full-bridge or other structure, without limitation here. That is, no matter what structure the full-bridge inverter unit 21 adopts, the overcurrent protection method adopted by the protection circuit 1 based on the bridge arm current of the full-bridge inverter unit 21 is consistent with the above content of this embodiment.

[0079] It should be noted that the overcurrent threshold of the bridge arm current of the inverter body 2 can be adjusted by adjusting the conduction voltage drops of the first switch Q1 and the second switch Q2.

[0080] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A protection circuit, characterized in that: include: A sampling circuit, a first switch circuit and a second switch circuit, wherein: A sampling circuit, wherein a first end of the sampling circuit is connected to a first end of the device to be protected and a control end of the first switch circuit, a second end of the sampling circuit is connected to a second end of the device to be protected and then grounded, and after a potential difference is generated between the first end and the second end of the sampling circuit under the action of the output current of the device to be protected, a voltage at the first end of the sampling circuit is a sampling voltage; A first switch circuit, whose control end is connected to the second end of the second switch circuit, whose first end is connected to the first end of the second switch circuit and the control end of the device to be protected, and whose second end is connected to the control end of the second switch circuit and then grounded; When the sampled voltage is a positive voltage and the sampled voltage is greater than the conduction voltage drop of the first switch circuit, after the first switch circuit is turned on and the second switch circuit is turned off, the first switch circuit controls the device to be protected to block driving; When the sampled voltage is a negative voltage and the absolute value of the sampled voltage is greater than the on-state voltage drop of the second switch circuit, after the second switch circuit is turned on and the first switch circuit is turned off, the second switch circuit controls the device to be protected to block driving.

2. The protection circuit according to claim 1, characterized in that: The sampling circuit comprises: A sampling resistor, a first end of which is connected to the first end of the device to be protected, and a second end of which is connected to the second end of the device to be protected.

3. The protection circuit according to claim 1, characterized in that: The first switch circuit comprises: A first switch, whose control end is connected to the first end of the sampling circuit and the second end of the second switch circuit, whose first end is connected to the first end of the second switch circuit and a first power supply, and whose second end is connected to the control end of the second switch circuit; When the sampling voltage is a positive voltage and the sampling voltage is greater than the on-state voltage drop of the first switch, the first switch is turned on and the second switch circuit is turned off; When the sampled voltage is a negative voltage and the absolute value of the sampled voltage is greater than the on-state voltage drop of the second switch circuit, the second switch circuit is turned on and the first switch is turned off.

4. The protection circuit according to claim 1, characterized in that: The second switch circuit comprises: a second switch, whose control end is connected to the second end of the first switch, whose first end is connected to the first end of the first switch, and whose second end is connected to the control end of the first switch; When the sampled voltage is a positive voltage and the sampled voltage is greater than the on-state voltage drop of the first switch, the first switch is turned on and the second switch is turned off; When the sampled voltage is a negative voltage and the absolute value of the sampled voltage is greater than the on-state voltage drop of the second switch circuit, the second switch is turned on and the first switch is turned off.

5. The protection circuit according to claim 1, characterized in that: Also includes: The first current limiting circuit has a first end connected to the first end of the sampling circuit and a second end connected to the control end of the first switch circuit, and is used to limit the current output by the sampling circuit.

6. The protection circuit according to claim 1, characterized in that: Also includes: The second current limiting circuit has a first end connected to the first power supply and a second end connected to the first end of the first switch circuit, and is used to limit the current output by the first power supply.

7. An inverter, characterized in that: include: An inverter body, a drive circuit and a protection circuit as claimed in any one of claims 1 to 6, wherein: An inverter body, whose control end is connected to the output end of the drive circuit, whose first end is connected to the first end of the sampling circuit, and whose second end is connected to the second end of the sampling circuit; A driving circuit, an input end of which is connected to the first end of the first switch circuit; When the sampling voltage at the first end of the inverter body is a positive voltage and the sampling voltage is greater than the conduction voltage drop of the first switch circuit, after the first switch circuit is turned on and the second switch circuit is turned off, the drive circuit blocks the inverter body drive; When the sampling voltage at the detection end of the inverter body is a negative voltage and the absolute value of the sampling voltage is greater than the conduction voltage drop of the second switch circuit, after the second switch circuit is turned on and the first switch circuit is turned off, the drive circuit blocks the inverter body drive.

8. The inverter according to claim 7, characterized in that: The inverter body includes: a full-bridge inverter unit and a supporting capacitor, wherein: A full-bridge inverter unit, a first end of which is connected to the second power supply and the first end of the support capacitor, a second end of which is connected to the first end of the sampling circuit, and a control end of which is connected to the output end of the drive circuit, and is used to switch the switch state based on the switch sequence output by the drive circuit; A supporting capacitor, a second end of which is connected to the second end of the sampling circuit, and is used to maintain the stability of the second power supply; The direction of the bridge arm current flowing through the sampling circuit of the full-bridge inverter unit is different in different switching states; When the bridge arm current flows from the first end of the sampling circuit to the second end thereof, the first end of the sampling circuit is a positive voltage and the second end is a negative voltage; When the bridge arm current flows from the second end of the sampling circuit to the first end thereof, the first end of the sampling circuit is a negative voltage and the second end is a positive voltage.

9. The inverter according to claim 8, characterized in that: The full-bridge inverter unit includes: a first power device, a second power device, a third power device and a fourth power device, wherein: A first power device, a first end of which is connected to the third power device, the first end of the support capacitor and the second power supply, and a second end of which is connected to the first end of the second power device and the first end of the load; A second power device, a second end of which is connected to the second end of the fourth power device and the first end of the load; A third power device, a second end of which is connected to the first end of the fourth power device and the second end of the load; The control ends of the first power device, the second power device, the third power device and the fourth power device are all connected to the output end of the driving circuit; When the first power device and the fourth power device are turned on and the second power device and the third power device are turned off, or when the second power device and the third power device are turned on and the first power device and the fourth power device are turned off, the bridge arm current flows from the first end of the sampling circuit to the second end thereof; When the first power device, the second power device, the third power device and the fourth power device are all turned off, the bridge arm current flows from the second end of the sampling circuit to the first end thereof.

10. The inverter according to claim 9, characterized in that: The first power device, the second power device, the third power device and the fourth power device are all composed of a fully controlled power device and a diode connected in reverse parallel.

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