Frequency converter current sampling circuit

Abstract

The utility model relates to a frequency converter current sampling circuit comprising an isolation amplifier comprising a power supply pin, an input pin and an output pin, the power supply pin is connected with a power supply, and the input pin is connected with the output end of a frequency converter; the input end of the dial switch is connected with the output pin of the isolation amplifier; the first end of the adjusting resistor unit is connected with the output end of the dial switch; the operational amplifier is connected with the second end of the adjusting resistor unit; wherein the dial switch adjusts the gain of the operational amplifier by changing the state of a resistor switch in the resistor unit, and further adjusts the sampling amplification factor of the output current. According to the utility model, by introducing the design of combining the dial switch and the adjusting resistor unit, the gain of the operational amplifier can be flexibly adjusted, so that the sampling amplification factor of the output current is adjusted, and the problem that various power frequency converters cannot be compatible in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to sampling circuit technical field especially relates to a frequency converter current sampling circuit. BACKGROUND

[0002] In the application of frequency converter, not only for preventing overcurrent damage equipment, also for realizing dead zone compensation and current closed loop control. However, the current sampling circuit of existing general compatibility, flexibility is insufficient and so on, cannot effectively support the demand of multiple power frequency converter. Most current sampling circuit needs to design special circuit board for different power frequency converter, usually based on single amplification multiple or fixed current induction mode. This design makes the circuit board not be used between different power grade frequency converter, caused the increase of production cost and the improvement of design complexity. The current sampling demand of different power needs to replace resistance, adjust gain or redesign circuit, greatly influenced the expansibility and universality of system.

[0003] In summary, the current sampling circuit of existing cannot be compatible with multiple different power grade frequency converter, causes the same circuit board to be unable to adapt to diversified application scene, this not only increases the cost of equipment, also limits the flexibility and expansibility of system. Therefore, how to design a kind of current sampling circuit that can be compatible with different power demand, improve compatibility and flexibility becomes the bottleneck of current technical development. UTILITY MODEL CONTENT

[0004] The utility model aims at providing a kind of frequency converter current sampling circuit to solve the technical problem that the current sampling circuit of existing cannot be compatible with different power demand.

[0005] To achieve this purpose, the utility model adopts the following technical scheme:

[0006] The application provides a kind of frequency converter current sampling circuit, comprising:

[0007] Isolation amplifier, including power supply pin, input pin and output pin, the power supply pin is connected power supply, the input pin is connected the output end of frequency converter;

[0008] Dial switch, the input end of dial switch is connected with the output pin of isolation amplifier;

[0009] Adjusting resistance unit, the first end of adjusting resistance unit is connected with the output end of dial switch;

[0010] Operational amplifier, the second end of adjusting resistance unit is connected with operational amplifier;

[0011] The dial switch adjusts the gain of the operational amplifier by changing the resistance switch state in the resistance unit, thereby adjusting the sampling amplification multiple of the output current.

[0012] Further, the output end of the dial switch includes a plurality of terminals (TP1, TP2, TP3, TP4), and the plurality of terminals are connected with the adjusting resistance unit; the input end of the dial switch includes a plurality of reverse terminals (TP1#, TP2#, TP3#, TP4#), and the plurality of reverse terminals are connected with the output pin of the isolation amplifier.

[0013] Further, the adjusting resistance unit includes a first resistance, a second resistance, a third resistance, a fourth resistance, a fifth resistance and a sixth resistance, the first resistance and the sixth resistance are connected with the terminals (TP1, TP2, TP3, TP4), and the second resistance, the third resistance, the fourth resistance and the fifth resistance are respectively connected with the reverse terminals (TP1#, TP2#, TP3#, TP4#).

[0014] Further, a seventh resistance is further included, one end of the seventh resistance is connected with the power supply, and the other end is connected with the power supply pin of the isolation amplifier, for limiting the current flowing into the isolation amplifier from the power supply.

[0015] Further, a sampling resistance unit is further included, including an eighth resistance, a ninth resistance, a tenth resistance and an eleventh resistance, the eighth resistance, the ninth resistance, the tenth resistance and the eleventh resistance are arranged in parallel, and the sampling resistance unit is connected with the output end of the frequency converter, for converting the output signal of the frequency converter into a voltage signal.

[0016] Further, a filtering unit is further included, the filtering unit includes a twelfth resistance and a first capacitor, one end of the twelfth resistance is connected with the sampling resistance unit, the other end is connected with the first capacitor, and the first capacitor is connected with the amplification pin of the isolation amplifier.

[0017] Further, a first diode is further included, the first diode is connected with the seventh resistance, for stabilizing the power supply voltage.

[0018] Further, a second capacitor and a third capacitor are further included, the second capacitor and the third capacitor are connected with the first diode.

[0019] Further, the adjusting resistance unit further includes a thirteenth resistance, the thirteenth resistance is connected with the operational amplifier.

[0020] Further, a fourth capacitor is further included, the fourth capacitor is connected with the thirteenth resistance in parallel and is connected with the operational amplifier.

[0021] Compared with the prior art, the utility model has the following beneficial effects:

[0022] The frequency converter current sampling circuit of the present application introduces the design of combination of the dial switch and the adjusting resistor unit, which can flexibly adjust the gain of the operational amplifier, thereby adjusting the sampling amplification multiple of the output current, and solves the problem of incompatibility with multiple power frequency converters in the prior art. Specifically, the dial switch changes the resistance switch state in the resistor unit to realize the adjustability of the gain, so that the same circuit board can adapt to frequency converters of different power levels, thereby avoiding the cumbersome replacement of circuit boards or redesign of circuits for different power requirements. This design not only improves the compatibility and flexibility of the system, but also significantly reduces the production cost, because the same circuit board can be used in multiple frequency converter models, simplifying the production and maintenance process. In addition, due to the use of the combination of the isolation amplifier and the adjusting resistor unit, the current sampling accuracy is improved, which can more accurately feedback the current signal, providing more reliable protection and control for the frequency converter. Therefore, the current sampling circuit of the present application has high adaptability and cost-effectiveness, can meet the needs of various application scenarios, and greatly promotes the development of frequency converter current sampling technology. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0024] The structures, proportions, sizes, etc. shown in the drawings of the present specification are only used to cooperate with the content disclosed in the specification, to enable those skilled in the art to understand and read, and are not used to limit the implementation conditions of the present application, so they do not have technical significance. Any modification of structure, change of proportion relationship or adjustment of size, which does not affect the functions and purposes of the present application, should still fall within the scope of the technical content disclosed by the present application.

[0025] Figure 1 The frequency converter current sampling circuit schematic diagram in the present embodiment.

[0026] U8, isolation amplifier; VDD, power pin; Vin, input pin; Vout, output pin; SW1, DIP switch; TP1, TP2, TP3, TP4, terminal; TP1#, TP2#, TP3#, TP4#, reverse terminal; U9, operational amplifier; R44, first resistor; R45, second resistor; R47, third resistor; R50, fourth resistor; R54, fifth resistor; R55, sixth resistor; R43, seventh resistor; RA1, eighth resistor; RA2, ninth resistor; RA3, tenth resistor; RA4, eleventh resistor; R46, twelfth resistor; R51, thirteenth resistor; C29, first capacitor; C26, second capacitor; C27, third capacitor; C32, fourteenth resistor; ZD1, first diode. DETAILED DESCRIPTION

[0027] In order to make the utility model of the utility model purposes, characteristics, advantages can be more obvious and easy to understand, below will combine the drawings in the embodiments of the utility model, the technical scheme in the embodiments of the utility model is described clearly and completely, obviously, the following described embodiments are only a part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor are within the scope of the utility model.

[0028] In the description of the utility model, it is understood that the terms "upper", "lower", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the utility model. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there can be a component disposed therebetween.

[0029] The technical scheme of the utility model will be further illustrated below by combining the drawings and through specific embodiments.

[0030] Referring to Figure 1 The frequency converter current sampling circuit disclosed in the embodiment comprises:

[0031] The isolation amplifier U8 comprises a power pin VDD, an input pin Vin and an output pin Vout, the power pin VDD is connected to a power supply, and the input pin Vin is connected to an output end of a frequency converter;

[0032] The DIP switch SW1 is connected with the output pin Vout of the isolation amplifier U8.

[0033] a regulating resistance unit, a first end of the regulating resistance unit being connected with an output end of the dial switch SW1;

[0034] an operational amplifier U9, a second end of the regulating resistance unit being connected with the operational amplifier U9;

[0035] wherein the dial switch SW1 adjusts the gain of the operational amplifier U9 by changing the resistance switch state in the resistance unit, thereby adjusting the sampling amplification multiple of the output current.

[0036] In the embodiment, by combining the isolation amplifier U8, the dial switch SW1, the regulating resistance unit and the operational amplifier U9, the accurate sampling of the output current is realized, and the gain is adjusted to adapt to the requirements of the frequency converter of different power. Specifically, the current signal output by the frequency converter is sent to the input end of the isolation amplifier U8, and the isolation amplifier U8 functions to electrically isolate the current signal and avoid the interference of external circuits, while amplifying the signal to improve the processing precision. In the embodiment, the gain of the isolation amplifier U8 is set to 8 times, that is, the voltage signal entering the isolation amplifier U8 is amplified by 8 times, so as to ensure that the subsequent processing circuit can obtain a signal of sufficient strength for calculation and protection control. The output signal of the isolation amplifier U8 is then sent to the operational amplifier U9 in the form of a differential signal for further processing. The operational amplifier U9 functions to amplify the signal again to adapt to the final feedback control. In order to adapt to the frequency converter of different power requirements, the dial switch SW1 is used to adjust the gain of the operational amplifier U9 in the embodiment. Specifically, the dial switch SW1 is used to adjust the state of the resistance unit in the circuit, so as to change the parallel combination of the resistance, and then adjust the gain value of the amplifier. In actual operation, by changing the position of the dial switch SW1, the user can flexibly select the appropriate gain according to the power requirement of the frequency converter. For example, for a low-power frequency converter, a smaller gain is selected to adapt to the lower current sampling requirement, while for a high-power frequency converter, a higher gain can be selected to ensure that the current signal can be accurately sampled and amplified to a sufficient range. The adjustability of the gain makes the same circuit board adapt to frequency converters of different power, avoiding the cumbersome process of replacing the circuit board or redesigning in the traditional scheme.

[0037] The working process and control mode of the entire current sampling circuit have high flexibility and customizability. During system operation, the sampling resistor converts the inverter output current into a voltage signal, which is sent to the operational amplifier U9 after amplification by the isolation amplifier U8, and finally forms a voltage signal suitable for DSP processing. The DSP performs current detection and protection calculation based on these signals, timely triggers overcurrent protection or dead zone compensation, and avoids overcurrent damage to the inverter and load. In the specific current control process, the operational amplifier U9 and the dip switch SW1 are combined to realize the selection of different current amplification multiples, thereby ensuring the accuracy of current measurement and the adaptability of the system. In addition, since the invention uses domestic isolation amplifiers U8 and operational amplifiers U9, it not only reduces production costs, but also ensures the stability and economy of the circuit. By adjusting the current sampling amplification multiple, the invention realizes the compatibility of the circuit board between multiple power level inverters, so that the same circuit board can be widely used in different models of inverters, thereby greatly improving the versatility and scalability of the system. In summary, the current sampling circuit of the invention takes into account precision, flexibility and cost-effectiveness, solves the problems of poor compatibility and insufficient flexibility of traditional current sampling circuits, and provides reliable technical support for current detection and protection of inverters.

[0038] In an embodiment, the output end of the dip switch SW1 includes a plurality of terminals (TP1, TP2, TP3, TP4), and the plurality of terminals are connected with the adjustment resistance unit. The input end of the dip switch SW1 includes a plurality of reverse terminals (TP1#, TP2#, TP3#, TP4#), and the plurality of reverse terminals are connected with the output pin Vout of the isolation amplifier U8. The adjustment resistance unit includes a first resistance R44, a second resistance R45, a third resistance R47, a fourth resistance R50, a fifth resistance R54, and a sixth resistance R55. The first resistance R44 and the sixth resistance R55 are connected with the terminals (TP1, TP2, TP3, TP4). The second resistance R45, the third resistance R47, the fourth resistance R50, and the fifth resistance R54 are respectively connected with the reverse terminals (TP1#, TP2#, TP3#, TP4#). The adjustment resistance unit further includes a thirteenth resistance R51, and the thirteenth resistance R51 is connected with the operational amplifier U9.

[0039] In this embodiment, the output terminals of the dip switch SW1 include multiple terminals (TP1, TP2, TP3, TP4) connected to the adjusting resistance units, and the input terminals of the dip switch SW1 include multiple reverse terminals (TP1#, TP2#, TP3#, TP4#) connected to the output pin Vout of the isolation amplifier U8. This design uses multiple terminals and reverse terminals to more accurately control the switching and adjustment of resistances in the circuit, thereby adjusting the amplification factor of the current sampling. Specifically, different switch states of the dip switch SW1 correspond to different resistance connection combinations, and these combinations adjust the gain of the current sampling circuit by connecting different terminals, thereby controlling the strength of the output signal. This structure enhances the flexibility and adjustability of the circuit, allowing users to accurately adjust the gain of the current sampling system according to different working conditions and requirements. In one example, when the 1st pin TP1 and the 3rd pin TP3 of the dip switch SW1 are set to ON, the amplification factor A1 is determined by the parallel resistance value, where the calculation formula of A1 is: The calculation formula of the final output current IU is: In this way, the gain of the operational amplifier U9 is adjusted, allowing the current signal to be amplified to different degrees to meet the needs of different power inverters. Further, when the 2nd and 4th switches of the dip switch SW1 are set to ON, another resistance combination will affect the calculation of the gain A2, with the formula: The calculation formula of the final output current IU is: where 1.414 is derived from the relationship between the peak value and the effective value of alternating current, i.e., 1.414 represents the conversion factor between the effective value and the peak value of alternating current, approximately equal to the square root of two. The above adjustment method ensures that the same circuit board can adapt to three different power inverters, achieving flexibility and versatility of the current sampling circuit.

[0040] In one embodiment, a seventh resistance R43 is also included, with one end connected to the power supply and the other end connected to the power supply pin VDD of the isolation amplifier U8, for limiting the current flowing from the power supply to the isolation amplifier U8.

[0041] In this embodiment, the current sampling circuit further comprises a seventh resistor R43, one end of which is connected to the power supply and the other end is connected to the power supply pin VDD of the isolation amplifier U8, for limiting the current flowing into the isolation amplifier U8 from the power supply. The function of the seventh resistor R43 is to provide current limiting function for the power supply, so as to avoid overcurrent of the power supply causing damage or unstable operation of the isolation amplifier U8. The isolation amplifier U8 is used to improve the isolation degree of the current signal and ensure that the input signal is not disturbed by other parts of the circuit. The seventh resistor R43 controls the current flowing into the power supply pin VDD of the isolation amplifier U8 by connecting with the power supply, ensuring that the power supply current is within a safe range, thereby protecting other sensitive components in the circuit and ensuring the stability and reliability of the entire circuit.

[0042] In an embodiment, a sampling resistor unit is further included, which comprises an eighth resistor RA1, a ninth resistor RA2, a tenth resistor RA3 and an eleventh resistor RA4, the eighth resistor RA1, the ninth resistor RA2, the tenth resistor RA3 and the eleventh resistor RA4 are connected in parallel, and the sampling resistor unit is connected with the output end of the frequency converter, for converting the output signal of the frequency converter into a voltage signal.

[0043] In this embodiment, the function of the sampling resistor unit is to convert the output current signal of the frequency converter into a voltage signal, which is realized by parallel connection of resistors. The parallel connection of resistors enables the signal to pass through appropriate voltage division, thereby being converted into a voltage signal suitable for subsequent processing. By selecting different resistance values, the amplitude of the sampling signal can be adjusted, so that the sampling circuit can adapt to different working environments and signal strengths, ensuring that the sampling signal can accurately reflect the output current of the frequency converter. This part of the circuit plays a role in converting the current signal into a voltage signal for subsequent analysis and processing. In an example, assuming that the U-phase output current is I and the parallel equivalent resistance of the eighth resistor RA1, the ninth resistor RA2, the tenth resistor RA3 and the eleventh resistor RA4 is R, the calculation formula of the output voltage is: ;

[0044] Assuming that the amplification factor of the later-stage operational amplifier U9 is A, A = R44 / R51, then IU is a software setting value corresponding to different output currents.

[0045] In an embodiment, a filtering unit is further included, which comprises a twelfth resistor R46 and a first capacitor C29, one end of the twelfth resistor R46 is connected with the sampling resistor unit, the other end is connected with the first capacitor C29, and the first capacitor C29 is connected with the amplification pin of the isolation amplifier U8.

[0046] In this embodiment, the role of the filter unit is to filter the signal transmitted from the sampling resistance unit, remove high-frequency noise or unnecessary signal interference. The twelfth resistance R46 and the first capacitor C29 form a low-pass filter, which can smooth the sampling signal, remove the high-frequency components that change rapidly, and ensure that the signal is more stable and pure to be transmitted to the isolation amplifier U8 for amplification. This design can effectively improve the quality of the signal and avoid the influence of noise on the current sampling result, thereby improving the measurement accuracy.

[0047] In an embodiment, a first diode ZD1 is also included, which is connected with the seventh resistance R43, for stabilizing the power supply voltage.

[0048] In this embodiment, the first diode ZD1 is a voltage stabilizing diode (5.1V), which provides a 5.1V voltage to the primary side of the isolation amplifier U8, protecting the isolation amplifier U8 and other circuit elements from the influence of power supply voltage fluctuations, thereby ensuring the stability of the power supply voltage. Excessive fluctuations in current and voltage can affect the performance of the circuit, especially for precise current sampling circuits, the stability of the power supply voltage is crucial. By using a diode to limit excessive current or voltage fluctuations, the normal operation of the circuit can be effectively ensured, and the stability and long-term reliability of the system can be improved.

[0049] In an embodiment, a second capacitor C26 and a third capacitor C27 are also included, which are connected with the first diode ZD1.

[0050] In this embodiment, the second and third capacitors C27 serve to further enhance the stability of the power supply voltage and provide smooth current or voltage changes in the circuit. Capacitors, as filtering elements, can effectively store and release charges, helping to remove noise or voltage fluctuations in the power supply, thereby improving the stability of the power supply voltage. The connection mode of the second and third capacitors C27 forms a power filter network with the first diode ZD1, helping to buffer the transient changes of the power supply current and provide more stable power output. This configuration enables the current sampling circuit to operate stably under various external environments, improving the anti-interference ability and stability of the system.

[0051] In an embodiment, a fourth capacitor is also included, which is connected in parallel with the thirteenth resistance R51 and connected with the operational amplifier U9.

[0052] In the present embodiment, the fourth capacitor can improve the stability between the adjusting resistance unit and the operational amplifier U9, and its parallel effect helps to balance the frequency response of the circuit. The role of the fourth capacitor is to smooth the voltage change in the circuit, especially when processing high-frequency signals, the capacitor can effectively remove high-frequency noise. By being connected in parallel with the thirteenth resistor R51, the fourth capacitor can improve the gain response of the circuit, reduce the gain instability phenomenon caused by voltage fluctuations, and thus improve the accuracy of current sampling. After being connected with the operational amplifier U9, this capacitor also helps to stabilize the working state of the operational amplifier U9, ensuring the performance consistency of the entire circuit in long-time operation.

[0053] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A frequency converter current sampling circuit, characterized by The application relates to an isolation amplifier (U8) comprising a power supply pin (VDD) connected to a power supply, an input pin (Vin) connected to an output end of a frequency converter, and an output pin (Vout); a dial switch (SW1) with an input end connected to the output pin (Vout) of the isolation amplifier (U8); an adjusting resistance unit with a first end connected to an output end of the dial switch (SW1); and an operational amplifier (U9) connected to a second end of the adjusting resistance unit. The dial switch (SW1) adjusts the gain of the operational amplifier (U9) by changing the resistance switch state of the resistance unit, thereby adjusting the sampling amplification multiple of the output current. The output end of the dial switch (SW1) comprises a plurality of terminals (TP1, TP2, TP3, TP4) connected to the adjusting resistance unit, and the input end of the dial switch (SW1) comprises a plurality of reverse terminals (TP1#, TP2#, TP3#, TP4#) connected to the output pin (Vout) of the isolation amplifier (U8). The adjusting resistance unit comprises a first resistance (R44), a second resistance (R45), a third resistance (R47), a fourth resistance (R50), a fifth resistance (R54), and a sixth resistance (R55), wherein the first resistance (R44) and the sixth resistance (R55) are connected to the terminals (TP1, TP2, TP3, TP4), and the second resistance (R45), the third resistance (R47), the fourth resistance (R50), and the fifth resistance (R54) are respectively connected to the reverse terminals (TP1#, TP2#, TP3#, TP4#). The application further comprises a seventh resistance (R43) with one end connected to the power supply and the other end connected to the power supply pin (VDD) of the isolation amplifier (U8), for limiting the current flowing from the power supply to the isolation amplifier (U8). The application further comprises a sampling resistance unit comprising an eighth resistance (RA1), a ninth resistance (RA2), a tenth resistance (RA3), and an eleventh resistance (RA4), wherein the eighth resistance (RA1), the ninth resistance (RA2), the tenth resistance (RA3), and the eleventh resistance (RA4) are arranged in parallel, and the sampling resistance unit is connected to the output end of the frequency converter, for converting the output signal of the frequency converter into a voltage signal.

2. The frequency converter current sampling circuit of claim 1, wherein, The application further comprises a filtering unit comprising a twelfth resistance (R46) and a first capacitor (C29), wherein one end of the twelfth resistance (R46) is connected to the sampling resistance unit, the other end is connected to the first capacitor (C29), and the first capacitor (C29) is connected to the amplification pin of the isolation amplifier (U8).

3. The frequency inverter current sampling circuit of claim 2, wherein, The application further comprises a first diode (ZD1) connected to the seventh resistance (R43), for stabilizing the power supply voltage.

4. The frequency inverter current sampling circuit of claim 1, wherein, ​ 5. The frequency inverter current sampling circuit of claim 1, wherein, ​ 6. The frequency inverter current sampling circuit of claim 5, wherein, ​ 7. The frequency inverter current sampling circuit of claim 4, wherein, ​ 8. The frequency inverter current sampling circuit of claim 7, wherein, A second capacitor (C26) and a third capacitor (C27) are also included, which are connected with the first diode (ZD1).

9. The frequency inverter current sampling circuit of claim 7, wherein, The adjusting resistance unit further includes a thirteenth resistance (R51), which is connected with the operational amplifier (U9).

10. The frequency inverter current sampling circuit of claim 9, wherein, A fourth capacitor is also included, which is connected with the thirteenth resistance (R51) in parallel and with the operational amplifier (U9).

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