Self-checking constant current device for a leakage current sensor

Abstract

The utility model discloses a kind of self-checking constant current devices for leakage current sensor, it is related to leakage current measurement and detection technical field, including magnetic ring, excitation coil and self-checking coil are wound on the magnetic ring, the excitation coil is connected with magnetic flux gate excitation circuit signal, the self-checking coil is electrically connected with self-checking circuit, the excitation circuit is connected with magnetic demodulation circuit signal, the excitation circuit is used to receive the signal of the excitation coil induction and output corresponding voltage, the self-checking circuit is electrically connected with CHECK signal input end, power supply VCC5V and ground GND respectively, the self-checking circuit is used to provide constant direct current to the self-checking coil.This device can provide stable self-checking current output, to ensure the reliability and stability of sensor self-checking function and measurement function.

Description

Technical Field

[0001] This utility model relates to the field of leakage current measurement and detection technology, specifically to a self-testing constant current device for leakage current sensors. Background Technology

[0002] Leakage current sensors are widely used in various electrical systems to monitor leakage current in real time and ensure the safe operation of the electrical system. Based on market demand for the reliability and accuracy of leakage current sensor measurements, and the performance requirements of related technological advancements, leakage current sensors on the market typically need to be equipped with automatic detection functions. This automatic detection function, under the control of the host computer, performs two main functions: First, the host computer outputs a corresponding control signal during power-on. This signal is used to determine the condition of the leakage current sensor itself, ensuring that the sensor is in normal working order before use. Second, the same control signal is used to correct the error in the current signal output by the leakage current sensor, minimizing measurement errors and enabling the sensor to more accurately capture and measure leakage current. This reduces false triggering caused by measurement deviations and avoids unnecessary system shutdowns or fault responses due to false triggering.

[0003] However, the automatic detection circuits currently used in leakage current sensors still have significant technical limitations in practical applications. Specifically, when the voltage input to the leakage current sensor drifts or undergoes other changes, the self-test current output by the automatic detection circuit will change accordingly, directly affecting the accuracy of the host's judgment on the sensor's condition and potentially leading to misjudgment of the sensor's status. Furthermore, temperature changes are also a crucial factor affecting the performance of the automatic detection circuit in the leakage current sensor's operating environment. When the ambient temperature changes from a lower to a higher level, the large temperature difference causes parameter differences in the electronic components used inside the leakage current sensor. These parameter changes are further transmitted to the automatic detection circuit, causing variations in the circuit's output self-test current. This not only interferes with the host's judgment of the sensor's condition but also reduces the effectiveness of error correction for the leakage current sensor's output current signal, ultimately affecting the overall measurement accuracy and operational reliability of the leakage current sensor. Utility Model Content

[0004] The objective of this invention is to provide a self-testing constant current device for a leakage current sensor, which can provide a stable self-testing current output, thereby ensuring the reliability and stability of the sensor's self-testing and measurement functions.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A self-testing constant current device for a leakage current sensor includes a magnetic ring with an excitation coil and a self-test coil wound on it. The excitation coil is connected to a fluxgate excitation circuit, and the self-test coil is connected to a self-test circuit. The excitation circuit is connected to a magnetic demodulation circuit. The excitation circuit receives a signal induced by the excitation coil and outputs a voltage corresponding to the induced signal, which then enters the magnetic demodulation circuit. The input terminal of the self-test circuit is connected to a CHECK signal, and a power supply VCC5V is connected to the self-test coil. The self-test circuit loop is connected to GND, and the self-test circuit provides a constant DC current to the self-test coil.

[0007] In one possible implementation, the self-test circuit includes transistors Q5 and Q6 and a sampling resistor R15. Transistor Q5 is an NPN current regulator, and transistor Q6 is an NPN constant current controller. One end of the self-test coil is connected to the power supply.

[0008] The VCC5V circuit is connected. The other end of the self-test coil is connected to the collector of transistor Q5. The emitter of transistor Q5 is connected to one end of the sampling resistor R15. The other end of the sampling resistor R15 is connected to ground GND. The base of transistor Q6 is connected to the end of the sampling resistor R15 near the emitter of transistor Q5. The collector of transistor Q6 is connected to the base of transistor Q5. The emitter of transistor Q6 is connected to ground GND.

[0009] In one possible implementation, the self-test circuit further includes a resistor R51, one end of which is electrically connected to the base of the transistor Q5, and the other end of which is used to receive a CHECK signal.

[0010] In one possible implementation, the self-test circuit further includes a resistor R49, one end of which is electrically connected to the CHECK signal input terminal, and the other end of which is electrically connected to the end of the resistor R51 away from the base of the transistor Q5.

[0011] In one possible implementation, the self-test circuit further includes a resistor R13 and a capacitor C32. One end of the resistor R13 is electrically connected to the end of the resistor R49 away from the CHECK signal input terminal, and the other end of the resistor R13 is electrically connected to the end of the resistor R51 away from the base of the transistor Q5. One end of the capacitor C32 is electrically connected to the connection point of the resistors R13 and R51, and the other end of the capacitor C32 is electrically connected to ground GND. The resistor R13 and the capacitor C32 form an RC filter circuit.

[0012] In one possible implementation, the sampling resistor R15 is a single resistor, one end of which is electrically connected to the emitter of the transistor Q5, and the other end of which is electrically connected to ground GND.

[0013] In one possible implementation, the sampling resistor R15 includes at least two resistors that are connected end-to-end in sequence, wherein one end of the first resistor is connected to the emitter of the transistor Q5, and the other end of the last resistor is connected to ground GND.

[0014] In one possible implementation, the sampling resistor R15 includes at least two resistors, one end of which is electrically connected to the emitter of the transistor Q5, and the other end of which is electrically connected to ground GND.

[0015] In one possible implementation, the sampling resistor R15 includes at least two resistor groups, each resistor group including at least two resistors connected end to end in sequence, one end of the at least two resistor groups being electrically connected to the emitter of the transistor Q5, and the other end of the at least two resistor groups being electrically connected to ground GND.

[0016] In one possible implementation, the sampling resistor R15 includes at least two resistor branches, each resistor branch including at least two resistors connected end to end in sequence, one end of the at least two resistor branches is connected to the emitter of the transistor Q5, and the other end of the at least two resistor branches is connected to the ground GND.

[0017] Compared with the prior art, the advantages of this utility model are as follows:

[0018] The self-testing constant current circuit of this invention has excellent output current stability and can maintain a constant state. When the input power supply voltage fluctuates, such as when the power supply VCC5V rises or falls, the output current will not change accordingly; even if the operating environment temperature changes, whether the temperature rises from a lower level to a higher level or falls from a higher level to a lower level, the output current will not be affected and will always remain at the set constant value.

[0019] This invention's self-test constant current circuit is equipped with an input filter circuit. This filter circuit filters the input CHECK signal, preventing interference signals from entering it. The input filter circuit consists of an RC filter circuit composed of resistor R13 and capacitor C32, which, together with resistor R49, provides anti-interference. Resistor R49 prevents additional interference caused by parasitic parameters, thus ensuring a stable input CHECK signal and avoiding adverse effects of interference signals on the circuit's self-test function.

[0020] The output current of the self-test constant current circuit of this invention can be adjusted according to actual usage requirements to meet the self-test current requirements in different scenarios. The adjustment process can be achieved by adjusting the resistance value of the sampling resistor R15. Specifically, a standard resistance value of sampling resistor R15 corresponding to the required current can be selected, or multiple resistors can be connected in series, parallel, or a combination of series and parallel connections to form the required resistance value of sampling resistor R15. This allows for flexible setting of the output current to adapt to the self-test requirements of different leakage current sensors. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the self-test circuit used in current market products.

[0023] Figure 2 This is a schematic diagram of the self-test circuit in an embodiment of the present invention;

[0024] Figure 3 This is a basic circuit diagram of an embodiment of the present utility model;

[0025] Figure 4 This is a circuit diagram of the sampling resistor series type in an embodiment of this utility model;

[0026] Figure 5 This is a circuit diagram of the parallel sampling resistor in an embodiment of the present invention;

[0027] Figure 6 This is a parallel-series circuit diagram of the sampling resistors in this embodiment of the present invention;

[0028] Figure 7 This is the second form of the parallel-series sampling resistor circuit diagram in this utility model embodiment;

[0029] Figure 8 This is circuit diagram form three of the parallel-series sampling resistors in the embodiments of this utility model. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] Example:

[0032] It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments of this utility model are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or devices.

[0033] The schematic diagram of the automatic detection circuit used in leakage current sensors currently on the market is as follows: Figure 1 As shown, the Figure 1 This is a schematic diagram of a self-test circuit used in current market products. From... Figure 1 As shown in the schematic diagram, the current flowing through the self-test coil can be calculated using the following formula.

[0034] Iws=VCC / (R+Rsdc+Rds) (Formula 1)

[0035] In the formula, Iws is the current flowing through the self-test coil; R is the current limiting current; Rwdc is the DC resistance of the self-test coil; and Rds is the internal resistance of the MOSFET Q7.

[0036] When the host sends a high level to the Check network, the MOSFET Q7 will turn on. At this time, the self-test current Iws will start from VCC, pass through the resistor R, the self-test coil, the drain of the MOSFET, and the source, and finally flow to ground, forming a complete current loop.

[0037] Based on the above principles and Formula 1, it is clear that when VCC changes for some reason, such as VCC rising from 5V to 5.3V or falling from 5V to 4.8V, the current flowing through the self-test coil will increase or decrease accordingly, and the stability of the self-test current will be directly affected by the fluctuation of VCC voltage.

[0038] Based on the above principle and Formula 1, it is clear that when the ambient temperature changes, the resistance of resistor R will increase or decrease, and the internal resistance of MOSFET Q7 may also increase or decrease. Furthermore, the changes in the parameters of electronic components caused by temperature changes will further increase or decrease the current flowing through the self-test coil, and the stability of the self-test current will also be affected by changes in ambient temperature.

[0039] When the current flowing through the self-test coil changes, it can adversely affect the normal operation of the leakage current sensor. On the one hand, this current change can cause the host to mistakenly determine that the leakage current sensor is damaged, thus causing the entire machine to stop working. On the other hand, this current change can introduce significant errors when the host calibrates the leakage current sensor. These errors can lead the host to incorrectly determine that there is leakage, ultimately causing the entire machine to stop working as well, even though there is actually no leakage in the system; the incorrect judgment is simply due to a significant error during calibration.

[0040] In fluxgate current sensors, the magnetic rings used can have different characteristics due to material deviations. Materials from different batches are not completely identical in composition or performance, resulting in differences in magnetic field bias of the produced magnetic rings. Moreover, deviations in the manufacturing process of the magnetic rings can also cause differences in the characteristics of each magnetic ring. Both of these factors affect the consistency of the magnetic rings.

[0041] In fluxgate circuits, nonlinear components are used, which can cause bias voltage drift. For example, operational amplifiers used in excitation and demodulation circuits can produce voltage and current offsets, which can further affect the normal signal output of the circuit.

[0042] The resistors and capacitors used in the circuit have inherent errors, which directly cause deviations in the circuit output signal, making the actual output signal not completely consistent with the theoretically required signal.

[0043] The combined effect of the above factors will inevitably cause a deviation between the circuit output signal and the theoretically required signal. In order to minimize the deviation between the output signal and the expected signal and ensure the accuracy of the circuit output, this utility model proposes a self-testing circuit scheme, which can effectively solve the deviation problem in practical applications.

[0044] The following explains the solution principle of the self-test circuit: Two sets of coils are wound on a magnetic ring. One set is an excitation coil, which is connected to the excitation circuit of the fluxgate. The other set is a self-test coil, which is connected to the self-test circuit. The two sets of coils are magnetically coupled through the magnetic ring to transmit signals.

[0045] When current flows through the two ends of the L1 winding, the L2 coil can detect the change in the magnetic field generated by the current. Specifically, when the current flowing through the L1 coil increases, the current detected by the L2 coil will also increase, and when the current flowing through the L1 coil decreases, the current detected by the L2 coil will also decrease. The current detected by the L2 coil will change with the change in the current of the self-test coil L1.

[0046] The current detected by coil L2 is magnetically modulated under the control of a fluxgate. The modulated signal is then transmitted to a demodulation circuit. This demodulation circuit processes the signal and outputs a voltage corresponding to the detected current. The level of this output voltage reflects the magnitude of the current detected by excitation coil L2, and consequently, the magnitude of the current flowing through self-test coil L1. The block diagram of this solution is shown below. Figure 2 As shown.

[0047] In summary, when a fixed current flows through the self-test coil, the circuit outputs a fixed voltage. If the voltage measured at the output corresponds to the current flowing through the self-test coil, the error of the entire circuit is within a controllable range, and the corresponding product meets the qualification standard. If the voltage measured at the output does not correspond to the current flowing through the self-test coil, and the deviation exceeds the allowable range, the error of the entire circuit is too large, and the corresponding product does not meet the qualification standard.

[0048] Therefore, the stability and accuracy of controlling the current flowing through the self-test coil have a significant impact on the accuracy of the entire circuit's current measurement and error control. This solution can keep the DC current flowing through the self-test coil on the magnetic ring constant. This current will not fluctuate with the power supply VCC5V or with changes in the operating environment temperature. The schematic diagram of this self-test circuit is shown below. Figure 3 As shown.

[0049] The self-test circuit of this utility model is composed of transistor Q5, transistor Q6, sampling resistor R15, resistor R51, resistor R13, resistor R49, capacitor C32, and self-test coil L1. This self-test circuit is used to generate a constant DC current so that the output current is not affected by changes in input voltage and temperature drift. The specific function of each electronic component is described below. Transistor Q5 is an NPN transistor, acting as a current regulator. By adjusting its base voltage, it regulates the output current of the entire circuit. Transistor Q6 is also an NPN transistor, acting as a constant current control transistor, primarily used to control the base voltage of transistor Q5. Sampling resistor R15 is a low-temperature drift resistor, its function being current sampling; therefore, it is also called a current sampling resistor. Resistor R51 is the base input bias resistor for transistor Q5, providing a suitable bias current to the base of transistor Q5. Resistor R13 and capacitor C32 together form an RC filter circuit, which filters out interference signals present in the external input line. Resistor R49 is a line impedance resistor, its function being to prevent interference signals generated by parasitic parameters in the line. Self-test coil L1 is the core coil for realizing the self-test function, used to transmit current signals to complete the self-test process.

[0050] The working principle of the self-test circuit will be explained in detail below.

[0051] When the CHECK signal input is high, the current first passes through the RC filter circuit composed of resistor R13 and capacitor C32 to filter out interference signals. Then, it passes through resistor R51 to the base of transistor Q5, at which point transistor Q5 will conduct. After transistor Q5 conducts, the current flows from the power supply terminal VCC5V, sequentially through the self-test coil L1, the collector of transistor Q5, and then from the emitter of transistor Q5. Finally, it flows through the current sampling resistor R15 to ground GND, forming a complete current loop.

[0052] Since the base of transistor Q6 is directly connected to the sampling resistor R15, the voltage across R15 directly reflects the current flowing through the self-test coil L1. This sampling voltage, transmitted to the base of transistor Q6, controls the conduction depth of Q6. Furthermore, because the collector of transistor Q6 is connected to the base of transistor Q5, the conduction depth of Q6 further controls the voltage at the base of transistor Q5, thus controlling the conduction depth of transistor Q5. When the voltage across the sampling resistor R15 reaches 0.7V, transistor Q6 enters saturation conduction. At this point, the voltage across R15 is clamped by the Vbe voltage of transistor Q6, and the conduction depth of Q6 no longer changes. The circuit utilizes this characteristic to achieve constant current.

[0053] To more clearly illustrate how the circuit maintains a constant current, we will analyze this by assuming two common unstable factors. In the first scenario, if the power supply voltage VCC5V drifts from 5V to 5.5V, according to the circuit diagram, the current flowing through the self-test coil L1 will increase, leading to a rise in the voltage across the sampling resistor R15. With the voltage across R15 increasing, the current Ib6 flowing into the base of transistor Q6 will increase, and the current Ic6 flowing into the collector of transistor Q6 will also increase accordingly. Simultaneously, the collector voltage Uc6 of transistor Q6 will decrease, causing a decrease in the base voltage Ub5 of transistor Q5. Due to the presence of transistor Q6, the emitter voltage of transistor Q5 will be maintained at 0.7V by the base voltage Vbe6 of transistor Q6, resulting in a decrease in the base-emitter voltage Vbe5 of transistor Q5. This reduces the current Ic5 flowing through the collector of transistor Q5, ultimately leading to a decrease in the current flowing through the self-test coil L1. The entire process is a negative feedback process. It is through the negative feedback process that the circuit can maintain a constant current flowing through the self-test coil L1. The process can be described as follows: the power supply voltage VCC5V increases → the current of the self-test coil L1 increases → the voltage across the sampling resistor R15 increases → Ib6 increases → Ic6 increases → Uc6 decreases → Ub5 decreases → Ic5 decreases → the current of the self-test coil L1 decreases → the current of the self-test coil L1 remains constant.

[0054] The second scenario, also based on the same principle, conversely maintains a constant current flowing through the self-test coil L1. If the power supply voltage VCC5V drifts down from 5V to 4.5V, according to the circuit diagram, the current flowing through the self-test coil L1 will decrease, leading to a drop in the voltage across the sampling resistor R15. With the voltage across R15 decreasing, the current Ib6 flowing into the base of transistor Q6 will decrease, and the current Ic6 flowing into the collector of transistor Q6 will also decrease accordingly. Simultaneously, the collector voltage Uc6 of transistor Q6 will increase, causing the base voltage Ub5 of transistor Q5 to rise. Due to the presence of transistor Q6, the emitter voltage of transistor Q5 will be maintained at 0.7V by the base voltage Vbe6 of transistor Q6, resulting in an increase in the base-emitter voltage Vbe5 of transistor Q5. This increases the collector current Ic5 of transistor Q5, ultimately leading to an increase in the current flowing through the self-test coil L1. The entire process is also a negative feedback process. Through the negative feedback process, the circuit can maintain a constant current flowing through the self-test coil L1. The process can be described as follows: the power supply voltage VCC5V decreases → the current in the self-test coil L1 decreases → the voltage across the sampling resistor R15 decreases → Ib6 decreases.

[0055] →Ic6 decreases →Uc6 increases →Ub5 increases →Ic5 increases →The current of self-test coil L1 increases →The current of self-test coil L1 remains constant.

[0056] Besides power supply voltage fluctuations, changes in ambient temperature also affect the current. If an increase in ambient temperature leads to an increase in the current flowing through the self-test coil L1, the process of the current stabilizing is exactly the same as the process of the current increasing due to an increase in power supply voltage, and will not be described again here. If a decrease in ambient temperature leads to a decrease in the current flowing through the self-test coil L1, the process of the current stabilizing is exactly the same as the process of the current decreasing due to a decrease in power supply voltage, and will not be described again here.

[0057] This circuit design allows for setting the required self-test current based on different current demands. According to the circuit principle described above, the voltage across the current sampling resistor R15 will remain at 0.7V during constant current operation. Therefore, when setting the current, dividing 0.7V by the resistance value Rs of the sampling resistor R15 yields the required current Is. The calculation relationship is Is equal to 0.7V divided by Rs, where Is represents the current to be set, and Rs represents the resistance value of the sampling resistor R15.

[0058] The following example illustrates the calculation process for setting the current. Assume that a setting is required.

[0059] For a current of 100mA, according to the above calculation relationship, the resistance of the sampling resistor Rs is 0.7V divided by 0.1A, resulting in 7Ω; assuming a current of 500mA needs to be set, the resistance of the sampling resistor Rs is 0.7V divided by 0.5A, resulting in 1.4Ω; assuming a current of 1A needs to be set, the resistance of the sampling resistor Rs is 0.7V divided by 1A, resulting in 0.7Ω.

[0060] In the actual current setting process, if the calculated sampling resistor value is not the standard value, besides choosing a standard resistor close to the theoretically calculated value, a sampling resistor with the required resistance value can be formed by connecting resistors in series, in parallel, or a combination of series and parallel connections. Based on this resistor combination mode, this scheme also proposes three other different circuit forms, corresponding to... Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 The characteristics of the circuit forms corresponding to each diagram are explained below.

[0061] Figure 3 The corresponding circuit form is the circuit form described above, which is called the basic circuit. Figure 4 The corresponding circuit form is a series sampling resistor circuit, in which the number of resistors connected in series can be multiple, not limited to only two; Figure 5 The corresponding circuit form is a parallel sampling resistor circuit, in which the number of resistors connected in parallel can be multiple, and is not limited to only two; Figure 6 The corresponding circuit form is a combination of parallel and series circuit form one. Its characteristic is that the resistors are first connected in series, and then the series resistor is connected in parallel with other resistors. The number of resistors in series can be multiple, not limited to only two, and the number of resistors in parallel can also be multiple, not limited to only two. Figure 7 The corresponding circuit form is the second form of parallel-series combined circuit. Its characteristic is that multiple resistors are first connected in series, and then the series resistors are connected in parallel. The number of resistors in each series can be multiple, not limited to two, and the number of resistors in the parallel can be multiple, not limited to two. The number of series circuits can be multiple, not limited to two, and the number of parallel circuits can also be multiple, not limited to two. Figure 8 The corresponding circuit form is the sampling resistor parallel and series type circuit form three. Its characteristic is that the circuit has both series and parallel resistor structures. The number of resistors in series can be multiple, not limited to two, and the number of resistors in parallel can also be multiple, not limited to two. The number of series paths can be multiple, not limited to two, and the number of parallel paths can also be multiple, not limited to two.

[0062] The circuit configurations mentioned above—resistors in series, parallel, and a combination of both—are only used to illustrate the basic principles of circuits and are not limited to specific numbers of resistors, series connections, or parallel connections. In practical applications, the number of resistors, series connections, and parallel connections can be flexibly adjusted according to the required current, circuit power, and standardized resistor values ​​to meet different usage needs.

[0063] This self-test constant current circuit includes a CHECK signal anti-interference circuit. This circuit uses the cooperation of multiple components to process the CHECK signal to ensure the stability of the CHECK signal transmission.

[0064] Among them, resistor R49 is a line impedance matching resistor, whose main function is to prevent interference signals generated by parasitic parameters in the line, and to avoid such interference signals affecting the normal transmission of the CHECK signal. Resistor R13 and capacitor C32 together form an RC filter circuit, which can filter out interference signals mixed in from the external input line, further improving the purity of the CHECK signal.

[0065] The cutoff frequency of an RC filter circuit can be calculated using a specific formula: Fc = 1 / 2πRC, where Fc represents the cutoff frequency, R represents the resistance value, and C represents the capacitance value. In practical applications, the parameters of resistor R13 and capacitor C32 can be adjusted according to the characteristics of interference signals appearing in the circuit, based on the above formula, so that the anti-interference effect of the RC filter circuit meets the anti-interference requirements of actual use.

[0066] In the self-testing constant current circuit of this utility model, the parameter of resistor R13 is set to 4.7K, and the parameter of capacitor C32 is set to 0.1uF. When calculating the cutoff frequency of the RC filter circuit based on these two parameters, the values ​​are first substituted into the above formula. During the calculation process, 3.14 is used to approximate pi (π). At this time, the formula expands to:

[0067] Fc=1 / 2*3.14*4.7*0.1*10^3*10^-6

[0068] Fc = 1 / 2.9516 * 10^-3

[0069] Fc = 338 Hz.

[0070] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0071] The above embodiments are merely illustrative of the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All equivalent changes or modifications made based on the substance of the content of this utility model should be covered within the scope of protection of this utility model.

Claims

1. A self-testing constant current device for a leakage current sensor, comprising a magnetic ring, characterized in that, An excitation coil and a self-test coil are wound on the magnetic ring. The excitation coil is connected to the fluxgate excitation circuit, and the self-test coil is connected to the self-test circuit. The excitation circuit is connected to the magnetic demodulation circuit. The excitation circuit receives the signal induced by the excitation coil and outputs a voltage corresponding to the induced signal, which then enters the magnetic demodulation circuit. The input terminal of the self-test circuit is connected to the CHECK signal, and the power supply VCC5V is connected to the self-test coil. The self-test circuit loop is connected to GND, and the self-test circuit provides a constant DC current to the self-test coil.

2. The self-testing constant current device for a leakage current sensor according to claim 1, characterized in that, The self-test circuit includes transistors Q5 and Q6 and a sampling resistor R15. Transistor Q5 is an NPN current regulating transistor, and transistor Q6 is an NPN constant current control transistor. One end of the self-test coil is electrically connected to the power supply VCC5V, and the other end of the self-test coil is electrically connected to the collector of transistor Q5. The emitter of transistor Q5 is electrically connected to one end of the sampling resistor R15, and the other end of the sampling resistor R15 is electrically connected to ground GND. The base of transistor Q6 is electrically connected to the end of the sampling resistor R15 near the emitter of transistor Q5. The collector of transistor Q6 is electrically connected to the base of transistor Q5, and the emitter of transistor Q6 is electrically connected to ground GND.

3. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The self-test circuit also includes a resistor R51, one end of which is electrically connected to the base of the transistor Q5, and the other end of which is used to receive the CHECK signal.

4. The self-testing constant current device for a leakage current sensor according to claim 3, characterized in that, The self-test circuit also includes a resistor R49, one end of which is electrically connected to the CHECK signal input terminal, and the other end of which is electrically connected to the end of the resistor R51 away from the base of the transistor Q5.

5. The self-testing constant current device for a leakage current sensor according to claim 4, characterized in that, The self-test circuit also includes a resistor R13 and a capacitor C32. One end of the resistor R13 is electrically connected to the end of the resistor R49 away from the CHECK signal input terminal, and the other end of the resistor R13 is electrically connected to the end of the resistor R51 away from the base of the transistor Q5. One end of the capacitor C32 is electrically connected to the connection point of the resistors R13 and R51, and the other end of the capacitor C32 is electrically connected to ground GND. The resistor R13 and the capacitor C32 form an RC filter circuit.

6. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The sampling resistor R15 is a single resistor. One end of the single resistor is electrically connected to the emitter of the transistor Q5, and the other end of the single resistor is electrically connected to ground GND.

7. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The sampling resistor R15 includes at least two resistors, which are connected end to end in sequence. One end of the first resistor is connected to the emitter of the transistor Q5, and the other end of the last resistor is connected to ground GND.

8. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The sampling resistor R15 includes at least two resistors, one end of which is electrically connected to the emitter of the transistor Q5, and the other end of which is electrically connected to ground GND.

9. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The sampling resistor R15 includes at least two resistor groups, each resistor group including at least two resistors connected end to end in sequence. One end of the at least two resistor groups is connected to the emitter of the transistor Q5, and the other end of the at least two resistor groups is connected to the ground GND.

10. The self-testing constant current device for a leakage current sensor according to claim 2, characterized in that, The sampling resistor R15 includes at least two resistor branches, each of which includes at least two resistors connected end to end in sequence. One end of each of the at least two resistor branches is connected to the emitter of the transistor Q5, and the other end of each of the at least two resistor branches is connected to ground GND.

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