Fault protection circuit

Abstract

The utility model relates to the technical field of power electronics, and discloses a fault protection circuit. According to the circuit, the switching circuit is arranged to be connected with the potential pull-down circuit in the sampling circuit in parallel, when the threshold comparison circuit outputs a fault signal, the potential pull-down circuit rapidly pulls down the output fault signal, the switching circuit is switched on, and due to the fact that the voltage drop of the switching circuit is small, it can be guaranteed that the fault signal is pulled down to the corresponding detection standard and kept; meanwhile, the potential delay circuit can slow down the disappearance time of fault signals, and it is guaranteed that faults can be sampled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to a fault protection circuit. BACKGROUND

[0002] With the development of new energy vehicles, fault identification and protection of lines are more and more important. At present, sensors are mainly used to collect full-scale input parameters based on electromagnetic induction principle for identification, and corresponding fault protection measures are taken according to the identification results.

[0003] Although the current input parameter sampling scheme can realize basic sampling, the sampling results are disturbed by the vehicle fault working condition and the pressure difference existing in the sampling circuit itself, so that the actual output parameter may be higher than the set sampling threshold or the sampling signal reset time is too short. At this time, the sampling is considered not to be a fault, which affects the accuracy of sampling. CONTENT OF THE INVENTION

[0004] In view of this, the present application provides a fault protection circuit to solve the problem that the existing fault collection scheme is disturbed by other factors, resulting in abnormal fault signals and inaccurate sampling and identification.

[0005] The present application provides a fault protection circuit, which comprises a threshold comparison circuit, a switching circuit and a sampling circuit; the sampling circuit comprises a potential pull-down circuit and a potential delay circuit; the threshold comparison circuit is used for receiving collected line voltage signals and outputting comparison results of line faults to the sampling circuit; the output end of the threshold comparison circuit is connected with the input end of the potential delay circuit and the output end of the potential pull-down circuit respectively; and the switching circuit is connected with the potential delay circuit in parallel and connected with the output end of the potential pull-down circuit.

[0006] In a feasible implementation, the potential delay circuit comprises a voltage dividing circuit and a discharging circuit; one end of the voltage dividing circuit is connected with a power supply, and the other end of the voltage dividing circuit is connected with the input end of the discharging circuit; the output end of the discharging circuit is connected with the output end of the threshold comparison circuit; and the potential pull-down circuit is connected with the discharging circuit in parallel.

[0007] In a feasible implementation, the switching circuit comprises a switching device and a first resistor; the switching device and the first resistor are connected in series and then connected with the discharging circuit in parallel.

[0008] In a feasible implementation, the switching device comprises a power switch tube, a relay or an optoelectronic coupler.

[0009] In an embodiment, the source of the power switch tube is connected with the first resistor, the drain of the power switch tube is connected with the output of the threshold comparison circuit, and the gate of the power switch tube is connected with the voltage dividing circuit.

[0010] In an embodiment, the potential pull-down circuit is connected with the source and the drain of the power switch tube, forming a MOS push-pull structure.

[0011] In an embodiment, the coil of the relay is connected with the voltage dividing circuit in parallel, and the contact switch of the relay is connected with the first resistor in series and then connected with the potential pull-down circuit in parallel.

[0012] In an embodiment, when the switch device is a photoelectric coupler, the primary side of the photoelectric coupler is connected with the voltage dividing circuit in parallel, and the secondary side of the photoelectric coupler is connected with the first resistor in series and then connected with the potential pull-down circuit in parallel.

[0013] In an embodiment, the threshold comparison circuit comprises a first comparator circuit and a second comparator circuit connected in parallel; the positive input of the first comparator circuit and the negative input of the second comparator circuit are connected and then connected with the acquisition circuit of the line voltage signal; the negative input of the first comparator circuit inputs a negative parameter threshold value, and the positive input of the second comparator circuit inputs a positive parameter threshold value.

[0014] In an embodiment, the fault protection circuit further comprises a threshold generation circuit comprising a first output connected with the negative input of the first comparator circuit and a second output connected with the positive input of the second comparator circuit.

[0015] In the technical scheme provided in the present application, the circuit comprises a threshold comparison circuit, a switch circuit and a sampling circuit; the sampling circuit comprises a potential pull-down circuit and a potential delay circuit; the threshold comparison circuit is used for receiving the acquired line voltage signal and outputting a comparison result of line fault to the sampling circuit; the output of the threshold comparison circuit is connected with the input of the potential delay circuit and the output of the potential pull-down circuit respectively; and the switch circuit is connected with the potential delay circuit in parallel and connected with the output of the potential pull-down circuit. In the present application, the switch circuit is connected with the potential pull-down circuit in parallel in the sampling circuit, when the threshold comparison circuit outputs a fault signal, the potential pull-down circuit quickly pulls down the output fault signal, and the switch circuit is turned on, since the voltage drop of the switch circuit itself is small, the fault signal can be pulled down to the corresponding detection standard and maintained, thereby ensuring the accuracy of fault sampling, and the potential delay circuit can slow down the disappearance time of the fault signal, ensuring that the fault can be sampled. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A first schematic diagram of a fault protection circuit provided by an embodiment of the present application;

[0017] Figure 2 A second schematic diagram of a fault protection circuit provided by an embodiment of the present application;

[0018] Figure 3 A third schematic diagram of a fault protection circuit provided by an embodiment of the present application;

[0019] Figure 4 A circuit schematic diagram of a fault protection circuit provided by an embodiment of the present application;

[0020] Figure 5 Another circuit schematic diagram of a fault protection circuit provided by an embodiment of the present application;

[0021] Figure 6 Still another circuit schematic diagram of a fault protection circuit provided by an embodiment of the present application. DETAILED DESCRIPTION

[0022] The present application provides a fault protection circuit, which mainly increases a switching circuit and a potential pull-down circuit in parallel in an existing circuit structure, and uses the small voltage drop characteristic of the switching circuit to reduce the voltage drop of the potential pull-down circuit, so as to improve the accuracy of fault sampling.

[0023] The terms "first", "second", "third", "fourth" and the like in the description and claims of the present application, and above-described drawings (if there are) are used to distinguish similar objects, and do not necessarily have to be used to describe a particular sequential or chronological order. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in other than the order illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a list of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to such processes, methods, products or devices.

[0024] As Figure 1 shown, the fault protection circuit provided by an embodiment of the present application includes a threshold comparison circuit 110, a switching circuit 120 and a sampling circuit 130, wherein the output end of the threshold comparison circuit 110 is connected to the input end of the sampling circuit 130, and the output end of the sampling circuit 130 is connected to a monitored device of a fault.

[0025] The threshold comparison circuit 110 is connected with the current acquisition unit of the line current, receives the line voltage signal converted by the current acquisition unit, and outputs the comparison result of the line fault to the sampling circuit. The output line fault can be an overcurrent fault or an overvoltage fault. The overcurrent fault is taken as an example for description.

[0026] The monitoring device acquires the potential output by the sampling circuit 130 after determining the line fault. The switch circuit 120 is connected in parallel with the sampling circuit 130. When the threshold comparison circuit 110 outputs the fault potential signal, the sampling circuit 130 continues to pull down the potential signal at this time by discharging, until the switch circuit 120 is turned on, so that the low potential is maintained for a certain time, thereby meeting the acquisition time requirement of the monitoring device for the low potential.

[0027] In the embodiment, the sampling circuit 130 includes a potential pull-down circuit 131 and a potential delay circuit 132. The potential pull-down circuit 131 is connected in series with the potential delay circuit 132. The output end of the potential pull-down circuit 131 is connected with the output end of the threshold comparison circuit 110. The potential pull-down circuit 131 is used to pull down the potential signal to the threshold value or below the threshold value by discharging when the threshold comparison circuit 110 outputs the fault potential signal. When the potential signal is pulled down to the threshold value or below the threshold value, the switch circuit 120 is turned on, so that the potential signal is maintained at the threshold value or below the threshold value. When the threshold comparison circuit 110 outputs the fault disappearance potential signal, the potential delay circuit 132 is charged, and the potential signal gradually rises to the voltage value of the fault disappearance potential signal.

[0028] It should be noted that the potential pull-down circuit 131 is implemented by a diode. The cathode of the diode is connected with the output end of the threshold comparison circuit 110. When the output end of the threshold comparison circuit 110 is pulled down (outputs the fault potential signal), the voltage of the potential delay circuit 132 is rapidly discharged through the diode, so as to rapidly pull down the potential of the output end of the threshold comparison circuit 110.

[0029] In another embodiment, the potential delay circuit 132 includes a voltage division circuit 1321 and a discharge circuit 1322. One end of the voltage division circuit 1321 is connected with a power supply, and the other end of the voltage division circuit 1321 is connected with the input end of the discharge circuit 1322. The output end of the discharge circuit 1322 is connected with the output end of the threshold comparison circuit 110. The potential pull-down circuit 131 is connected in parallel with the discharge circuit 1322.

[0030] In practical application, when the voltage dividing circuit 1321 is connected with the switch circuit 120, it is connected with a certain potential position of the voltage dividing circuit 1321, instead of being connected with the input end or the output end of the voltage dividing circuit 1321, and the output end of the voltage dividing circuit 1321 is connected with the input end of the discharging circuit 1322, so that the voltage dividing circuit 1321 charges the discharging circuit 1322 when the output end of the threshold comparison circuit 110 needs to be converted from low level to high level.

[0031] It can be understood that the voltage dividing circuit 1321 is formed by a plurality of resistors connected in series. The discharging circuit 1322 is composed of a resistor and a plurality of capacitors, the resistor is connected in parallel with the potential pull-down circuit 131, one end of the resistor is connected with the output end of the threshold comparison circuit 110, the other end is connected with one end of the plurality of capacitors and the monitoring device, the plurality of capacitors are arranged in parallel, and the other end is grounded.

[0032] In another embodiment, the switch circuit 120 includes a switch device 121 and a first resistor 122; the switch device 121 is connected in series with the first resistor 122, and then connected in parallel with the discharging circuit 1322.

[0033] Through the implementation of the above-mentioned fault protection circuit, by connecting the switch circuit in parallel with the potential pull-down circuit, when the threshold comparison circuit outputs a fault signal, the potential pull-down circuit quickly pulls down the output fault signal, and the switch circuit is turned on, and the voltage drop of the switch circuit itself is small, which has little effect on the pulled-down fault signal, so as to realize the maintenance of the pulled-down signal, thereby improving the accuracy of fault sampling.

[0034] In a feasible implementation, the switch device 121 is a power switch tube or a relay or an optoelectronic coupler. The characteristics of these devices are that the voltage drop of the device itself is basically negligible.

[0035] If the switch device 121 is a power switch tube, the source of the power switch tube is connected with the first resistor 122, the drain of the power switch tube is connected with the output end of the threshold comparison circuit 110, and the gate of the power switch tube is connected with the voltage dividing circuit 1321, as shown in Figure 2 .

[0036] It should be noted that the power switch tube can be implemented by using a common MOS tube or an NMOS tube. When a common MOS tube is used, the potential pull-down circuit 131 is connected with the source and the drain of the power switch tube, and the potential pull-down circuit 131 and the power switch tube form a MOS push-pull structure.

[0037] If NMOS is used, the body diode of NMOS is used to replace the potential pull-down circuit 131, which is equivalent to integrating the potential pull-down circuit 131 on the power switch tube.

[0038] In another embodiment, as shown in Figure 3 If the switch device is a relay, the coil of the relay is connected in parallel with the voltage dividing circuit 1321, and the contact switch of the relay is connected in series with the first resistor 122 and then connected in parallel with the potential pull-down circuit 131.

[0039] If the switch device is an optocoupler, the primary side of the optocoupler is connected in parallel with the voltage dividing circuit 1321, and the secondary side of the optocoupler is connected in series with the first resistor 122 and then connected in parallel with the potential pull-down circuit 131.

[0040] In the embodiment, the threshold comparison circuit 110 includes a first comparator circuit 111 and a second comparator circuit 112 connected in parallel; the positive input end of the first comparator circuit 111 and the negative input end of the second comparator circuit 112 are connected and then connected with a line voltage signal acquisition circuit; the negative input end of the first comparator circuit 111 inputs a negative parameter threshold, and the positive input end of the second comparator circuit 112 inputs a positive parameter threshold. The positive parameter threshold and the negative parameter threshold can be a current threshold and a voltage threshold. The acquisition circuit can be a current sensor or a voltage sensor, which is arranged on the line to be measured to acquire a voltage signal and output to the first comparator circuit 111 and the second comparator circuit 112 for comparison and judgment.

[0041] Further, the fault protection circuit further includes a threshold generation circuit, which includes a first output end connected with the negative input end of the first comparator circuit 111 and a second output end connected with the positive input end of the second comparator circuit 112.

[0042] The following will take NMOS, relay and optocoupler as examples to illustrate, as shown in Figure 4 is the circuit principle diagram of the fault protection circuit of the switch circuit 120 designed by using NMOS.

[0043] The switch circuit 120 is composed of NMOS Q1 and resistor R14. Because of the PN junction characteristics of NMOS, there is a body diode inside, so there is no need to set a separate potential pull-down circuit 131, and the body diode in the NMOS is used as the potential pull-down circuit 131. In addition, the switch circuit 120 also includes a capacitor C2. The voltage dividing circuit 1321 is composed of resistors R2 and R4. The source of NMOS Q1 is connected to one end of resistor R4 through resistor R14. The other end of resistor R4 is connected to one end of resistor R2. The other end of resistor R2 is connected to a 5V power supply. The drain of NMOS Q1 is connected to the output of the threshold comparison circuit 110. The gate of NMOS Q1 is connected to the common end of resistor R4 and resistor R2. The capacitor C2 is arranged between the source and the gate.

[0044] The potential delay circuit 132 in the figure is composed of resistors R6, capacitors C6, C8 and C7. One end of resistor R6 is connected to the drain. The other end of resistor R6 is connected to the common end of resistor R14 and resistor R4. The three capacitors C6, C8 and C7 are connected in parallel and connected to the common end of resistor R14 and resistor R4.

[0045] The threshold comparison circuit 110 is designed by two comparators U1A and U1B. According to the parameter threshold value, such as the overcurrent threshold value, two voltage comparison values OC_REFH and OC_REFL are set as the positive input of comparator U1B and the negative input of U1A, respectively.

[0046] When the current value exceeds the reverse parameter threshold value (such as the reverse overcurrent threshold value), the current sensor voltage output PC_U is less than OC_REFL and OC_REFH, then U1B outputs high at this time, and U1A outputs low, and then PC_OC signal is pulled low to low level.

[0047] When the current value is between the reverse parameter threshold value and the forward parameter threshold value, the current sensor voltage output OC_REFL < PC_U < OC_REFH, then U1B outputs high at this time, and U1A outputs high, and then PC_OC signal is pulled high to high level by VQUC_5V.

[0048] Taking current as an example, when the current value is greater than the forward overcurrent threshold value, the current sensor voltage output OC_REFL < OC_REFH < PC_U, then U1B outputs low at this time, and U1A outputs high, and then PC_OC signal is pulled low to low level.

[0049] Through the above circuit design, because NMOS Q1 is used to design the switch circuit 120, and the body diode voltage drop of NMOS Q1 is Vd, when one of U1B and U1A outputs low to turn on the NMOS, there is also a tube voltage drop Vm2.

[0050] Assuming that the current fault occurs, the threshold comparison circuit 110 output low, then the drain voltage of Q1 is Vm2, the source voltage of Q1 is Vm2+Vd, then the gate-to-source voltage is VGS=(5-(Vm2+Vd))*R4 / (R2+R4+R14), the minimum conduction voltage of NMOS is Vth, so when VGS<Vth, NMOS is in the off state, and when VGS≥Vth, NMOS is in the on state. Configure R2, R4, R14 resistance, so that VGS=Vth at this time, then when the line fault occurs, the drain of Q1 is pulled low, at this time Q1 is in the open state, the current flows from the body diode of Q1, and finally when the drain voltage of Q1 is pulled low to Vm2, Q1 is closed, then the source voltage and drain voltage difference at this time is Vm2, and the source voltage will decrease by Vd-Vm2 at the moment of Q1 closing, so VGS will increase, ensuring that Q1 is in the on state and will not jitter. When the fault signal disappears, the output MOS of the comparator is off, and due to the pull-up of 5V, the drain voltage of Q1 starts to rise, the source voltage rises synchronously, and VGS gradually decreases, when VGS<Vth, Q1 is off, and the source voltage rises by Vd-Vm2 at the moment of off, so VGS will decrease, ensuring that Q1 is in the off state and will not jitter. Then 5V charges C6 through R6, and the voltage slowly rises to 5V. Thus, after the fault occurs, the level can be quickly pulled to a lower level, and after the fault disappears, the level can be slowly raised to meet the fault recovery time required by the monitoring device, so that the monitoring device can collect the fault signal.

[0051] As shown in Figure 5 , it is a circuit principle diagram of a fault protection circuit designed by adopting a relay to design a switching circuit, the relay consists of two parts, which are coil K1A and contact K1B, the potential pull-down circuit 131 is diode D1, diode D1 is connected in parallel with resistor R6, and contact K1B is connected in series with resistor R14 and then connected in parallel with diode D1.

[0052] When the fault signal occurs, the low level of the output end of the threshold comparison circuit 110 is 0V, and the anode voltage of the diode is VF1. The voltage drop Vka of the coil K1A is (5-VF1)*R4 / (R2+R4+R14). The minimum voltage drop of the coil K1A is Von. If Vka>Von, the coil K1A is conductive and closed, and the contact K1B is closed. If VkaVon, the coil K1A is broken and open, and the contact K1B is open. The resistors R2, R4 and R14 are configured so that Vka=Von at this time. When the line fails, the A1+ of the contact K1B is pulled low by the high level, and at this time, the contact K1B is in an open state. The current flows from the diode D1. When the level of the A2- of the final contact K1B reaches VF1, the voltage of the coil K1A reaches the conduction threshold Von, the contact K1B is closed, and the voltage of the A2- will be further pulled down to 0V. The voltage across the K1A will be further increased, so the closed state of the K1B will not be dithered. When the fault disappears, the A1+ of the contact K1B is raised by the low level, and the K1B is in a closed state. After the voltage of the A2- rises to VF1, the voltage of the coil K1A is lower than the conduction threshold Von, and the K1B is open. The diode D1 is in a reverse blocking state, and can only be charged through R6 and C6, C7 and C8. Thus, after the fault occurs, the level can be quickly pulled to a lower level. After the fault disappears, the level can be slowly raised to meet the fault recovery time required by the monitoring device, so that the monitoring device can collect the fault signal.

[0053] Further, the switch circuit 120 can also be implemented by an optoelectronic coupler. The circuit principle is the same as that of the relay, except that the optoelectronic coupler is composed of a primary device A and a secondary device B. These devices can be replaced by corresponding structures of the relay, as shown in FIG. 4. Figure 6

[0054] In the protection of the fault signal, the primary device A takes power from the voltage divider circuit composed of R2, R4 and R14. When the voltage across the primary device A reaches a specified threshold, the secondary device B will switch states to switch from conduction to off state. When the voltage across the primary device A is lower than the specified threshold, the secondary device B will switch states to switch from off to conduction state.

[0055] In this application, the switch circuit designed by using a power switch device, a relay or an optoelectronic coupler is connected in parallel to the potential pull-down circuit (i.e. the diode D1), which can reduce the level of the fault pull-down when the fault occurs, and ensure that the fault signal can be pulled to a low level. At the same time, the potential delay circuit is added to prolong the time when the low level is restored to the high level after the fault disappears, so as to ensure that the recovery time is long enough. In this way, not only the collection accuracy of the fault signal is improved, but also the fault signal can be collected when the fault occurs.

[0056] ​Finally, it should be noted that the above examples are merely specific embodiments of the present application, and are used to illustrate the technical solutions of the present application, but not to limit the same. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that, within the technical scope disclosed by the present application, any person skilled in the art can still modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features; and these modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A fault protection circuit, characterized by, The application relates to a threshold value comparison circuit, a switch circuit and a sampling circuit. The sampling circuit comprises a potential pull-down circuit and a potential delay circuit. The threshold value comparison circuit is used for receiving a collected line voltage signal and outputting a comparison result of line fault to the sampling circuit. The output end of the threshold value comparison circuit is connected with the input end of the potential delay circuit and the output end of the potential pull-down circuit respectively. The switch circuit is connected with the potential delay circuit in parallel and connected with the output end of the potential pull-down circuit. The potential delay circuit comprises a voltage dividing circuit and a discharging circuit.

2. The fault protection circuit of claim 1, wherein, One end of the voltage dividing circuit is connected with a power supply, and the other end of the voltage dividing circuit is connected with the input end of the discharging circuit. The output end of the discharging circuit is connected with the output end of the threshold value comparison circuit. The potential pull-down circuit is connected with the discharging circuit in parallel.

3. The fault protection circuit of claim 2, wherein, The switch circuit comprises a switch device and a first resistor.

4. The fault protection circuit of claim 3, wherein, The switch device is connected with the first resistor in series and then connected with the discharging circuit in parallel.

5. The fault protection circuit of claim 4, wherein, The switch device comprises a power switch tube or a relay or a photoelectric coupler.

6. The fault protection circuit of claim 5, wherein, The source of the power switch tube is connected with the first resistor, the drain of the power switch tube is connected with the output end of the threshold value comparison circuit, and the gate of the power switch tube is connected with the voltage dividing circuit.

7. The fault protection circuit of claim 4, wherein, The potential pull-down circuit is connected with the source and the drain of the power switch tube, forming a MOS push-pull structure.

8. The fail-safe circuit of claim 4, wherein, The coil of the relay is connected with the voltage dividing circuit in parallel, and the contact switch of the relay is connected with the first resistor in series and then connected with the potential pull-down circuit in parallel.

9. The fail-safe circuit of claim 1, wherein, If the primary side of the photoelectric coupler is connected with the voltage dividing circuit in parallel, the secondary side of the photoelectric coupler is connected with the first resistor in series and then connected with the potential pull-down circuit in parallel. The threshold value comparison circuit comprises a first comparator circuit and a second comparator circuit connected in parallel. The positive input end of the first comparator circuit and the negative input end of the second comparator circuit are connected and then connected with the collection circuit of the line voltage signal.

10. The fault protection circuit of claim 9, wherein, The negative input end of the first comparator circuit inputs a negative parameter threshold value, and the positive input end of the second comparator circuit inputs a positive parameter threshold value. The fault protection circuit further comprises: A threshold value generation circuit comprising a first output end connected with the negative input end of the first comparator circuit and a second output end connected with the positive input end of the second comparator circuit.

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