Frequency converter current sampling circuit and frequency converter

Abstract

The utility model discloses a frequency converter current sampling circuit and a frequency converter. The frequency converter current sampling circuit comprises a sampling module, a voltage generation module, a switch module and a control module. The sampling module outputs sampling voltage according to the sampling signal; the voltage generation module generates a zero bias voltage, synthesizes the zero bias voltage and the sampling voltage, outputs the synthesized zero bias voltage and sampling voltage to the first switching end, and outputs the zero bias voltage to the second switching end; the control module controls the common end of the switch module to switch on the first switching end or the second switching end so as to receive the sampling voltage comprising the zero bias voltage or the zero bias voltage. According to the technical scheme, the zero bias voltage only needs to be generated once, the complexity and the cost of the circuit are reduced, fluctuation caused by different generation modes is reduced through a single zero bias voltage source, and therefore the current sampling precision is improved, the influence of external interference on the system is reduced, and the reliability and the stability of the system are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a frequency converter current sampling circuit and a frequency converter. Background Art

[0002] During the operation of the inverter, current sampling is required, and zero-bias voltage must also be continuously collected. In order to adapt to different operating conditions, the existing technology must design two independent zero-bias voltage generation circuits. One zero-bias voltage generation circuit works in conjunction with the current sampling circuit to provide zero-bias voltage for the control module, and the other zero-bias voltage generation circuit provides zero-bias voltage for the control module alone. The traditional method usually requires generating zero-bias voltage twice, which brings some drawbacks, including:

[0003] 1. Designing two independent zero-bias voltage generation circuits not only increases the complexity of hardware design, but also increases the size and cost of the circuit.

[0004] 2. Since the circuits for generating the zero-bias voltage twice use different methods, the zero-bias voltage is unstable. This fluctuation will reduce the accuracy of signal sampling. Utility Model Content

[0005] The embodiments of the present utility model provide a frequency converter current sampling circuit and a frequency converter to solve the above technical problems.

[0006] A first aspect of an embodiment of the present utility model provides an inverter current sampling circuit, comprising: a sampling module, a voltage generating module, a switch module and a control module;

[0007] The sampling module outputs a sampling voltage according to the sampling signal;

[0008] The input end of the voltage generating module is connected to the output end of the sampling module, the first voltage output end is connected to the first switching end of the switching module, and the second voltage output end is connected to the second switching end of the switching module to generate a zero-bias voltage, and the zero-bias voltage and the sampling voltage are synthesized and output to the first switching end, and the zero-bias voltage is output to the second switching end;

[0009] The signal acquisition end of the control module is connected to the common end of the switch module, the output end of the control module is connected to the control end of the switch module, and the control module controls the common end of the switch module to switch on the first switching end or the second switching end to receive the sampling voltage including the zero-bias voltage or the zero-bias voltage.

[0010] Optionally, the power supply end of the voltage generating module and the power supply end of the sampling module are connected to the same power supply, and the third voltage output end of the voltage generating module is connected to the power supply end of the control module to convert the voltage of the power supply and then power the control module.

[0011] Optionally, the voltage generating module includes a voltage stabilizing unit, a synthesizing unit and a voltage dividing unit;

[0012] One end of the voltage stabilizing unit is connected to the power supply, and the other end is the third voltage output end of the voltage generating module, so as to obtain a first zero-bias voltage after stabilizing the voltage of the power supply and supply power to the control module;

[0013] The first end of the synthesis unit is connected to the other end of the voltage stabilizing unit, the second end of the synthesis unit is the input end of the voltage generating module, and the third end of the synthesis unit is the first voltage output end of the voltage generating module, so as to synthesize the sampling voltage and the first zero-bias voltage;

[0014] The first end of the voltage divider unit is connected to the other end of the voltage stabilizing unit, the second end of the voltage divider unit is grounded, and the third end of the voltage divider unit is the second voltage output end of the voltage generating module, so as to obtain a second zero-bias voltage after dividing the first zero-bias voltage and output it to the switching module.

[0015] Optionally, the voltage stabilizing unit includes a first resistor, a first capacitor and a voltage stabilizing diode;

[0016] The first end of the first resistor is one end of the voltage stabilizing unit, the second end of the first resistor, the cathode of the voltage stabilizing diode and the first end of the first capacitor are connected together as the other end of the voltage stabilizing unit, and the anode of the voltage stabilizing diode and the second end of the first capacitor are connected to the ground.

[0017] Optionally, the synthesis unit includes a second resistor and a third resistor;

[0018] The first end of the second resistor is the second end of the synthesis unit, the second end of the second resistor and the first end of the third resistor are connected together to form the third end of the synthesis unit, and the second end of the third resistor is the first end of the synthesis unit.

[0019] Optionally, the synthesis unit includes a fourth resistor and a fifth resistor;

[0020] The first end of the fourth resistor is the first end of the voltage divider unit, the second end of the fourth resistor and the first end of the fifth resistor are connected together to form the third end of the voltage divider unit, and the second end of the fifth resistor is the second end of the voltage divider unit.

[0021] Optionally, the switch module includes a first switch device and a second switch device;

[0022] One end of the first switching device is the first switching end of the switching module, one end of the second switching device is the second switching end of the switching module, the other end of the first switching device and the other end of the second switching device are connected together as the common end of the switching module, and the control end of the first switching device and the control end of the second switching device are respectively connected to the output end of the control module.

[0023] Optionally, the sampling module includes an operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor and a second capacitor, one end of the sixth resistor is a first sampling end, the other end of the sixth resistor is respectively connected to the non-inverting input end of the operational amplifier and one end of the seventh resistor, the other end of the seventh resistor is connected to the output end of the operational amplifier and one end of the tenth resistor, one end of the eighth resistor is a second sampling end, the other end of the eighth resistor is connected to the inverting input end of the operational amplifier and one end of the ninth resistor, the other end of the ninth resistor is grounded, the other end of the tenth resistor and one end of the second capacitor are connected to the output end of the sampling module, and the other end of the second capacitor is grounded.

[0024] A second aspect of an embodiment of the present utility model provides a frequency converter, comprising: the frequency converter current sampling circuit described in the first aspect.

[0025] The technical effect of the embodiment of the present utility model is as follows: the present technical solution, by setting a voltage generating module to cooperate with the switching module and the sampling module, only requires one zero-bias voltage circuit to generate zero-bias voltage at one time, thereby reducing the complexity and cost of the circuit, and the single zero-bias voltage source reduces the fluctuations caused by different generation methods, thereby improving the accuracy of current sampling, reducing the impact of external interference on the system, and improving the reliability and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 This is a structural diagram of a current sampling circuit for a frequency converter provided by the first embodiment of the present utility model;

[0028] Figure 2This is another structural diagram of a current sampling circuit for a frequency converter provided by the first embodiment of the present utility model;

[0029] Figure 3 This is a structural diagram of a voltage generation module of a frequency converter current sampling circuit provided by the first embodiment of the present utility model;

[0030] Figure 4 This is a circuit diagram of a voltage generation module of a frequency converter current sampling circuit provided by the first embodiment of the present utility model;

[0031] Figure 5 This is a structural diagram of a switch module of a frequency converter current sampling circuit provided by the first embodiment of the present utility model;

[0032] Figure 6 This is a circuit diagram of a sampling module of a frequency converter current sampling circuit provided by the first embodiment of the present utility model;

[0033] Figure 7 This is a circuit diagram of a frequency converter current sampling circuit provided by the first embodiment of the present utility model;

[0034] Figure 8 This is an equivalent circuit diagram of a frequency converter current sampling circuit provided by the first embodiment of the present invention when the first logic switch K1 is turned on and the second logic switch K2 is turned off;

[0035] Figure 9 This is an equivalent circuit diagram of a frequency converter current sampling circuit provided by the first embodiment of the present utility model when the first logic switch K1 is turned off and the second logic switch K2 is turned on;

[0036] Figure 10 This is a main circuit diagram of a frequency converter provided by the second embodiment of the present utility model;

[0037] In the figure: 10, inverter current sampling circuit; 101, sampling module; 102, voltage generation module; 103, switch module; 104, control module; 201, voltage stabilization unit; 202, synthesis unit; 203, voltage dividing unit; 301, first switching device; 302, second switching device. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] It should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0040] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part.

[0041] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the drawings is flipped, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0042] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0043] In order to fully understand the present invention, the following description will provide detailed structures and steps to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementation methods.

[0044] Example 1

[0045] This embodiment provides a converter current sampling circuit 10, such as Figure 1 As shown, it includes: a sampling module 101, a voltage generating module 102, a switching module 103 and a control module 104;

[0046] The sampling module 101 outputs a sampling voltage according to the sampling signal;

[0047] The input end of the voltage generating module 102 is connected to the output end of the sampling module 101, the first voltage output end is connected to the first switching end of the switching module 103, and the second voltage output end is connected to the second switching end of the switching module 103 to generate a zero-bias voltage, and the zero-bias voltage and the sampling voltage are synthesized and output to the first switching end, and the zero-bias voltage is output to the second switching end;

[0048] The signal acquisition end of the control module 104 is connected to the common end of the switch module 103, and the output end of the control module 104 is connected to the control end of the switch module 103. The control module 104 controls the common end of the switch module 103 to switch on the first switching end or the second switching end to receive the sampling voltage or the zero-bias voltage including the zero-bias voltage.

[0049] The inverter current sampling circuit design includes four main modules: sampling module 101, voltage generation module 102, switch module 103, and control module 104. Each module has a specific function. Through the coordinated operation of the four modules, a zero-bias voltage circuit can meet the system requirements. The functions of these modules are as follows:

[0050] The sampling module 101 is responsible for measuring and collecting the current in the inverter. Current sampling in the inverter is a key part of monitoring and controlling the operating status of the motor. Current sampling can be achieved in different ways, including but not limited to the following current sampling methods:

[0051] 1. Lower-bridge sampling: Lower-bridge sampling is a very economical current sampling method, commonly used in low-power general-purpose inverters. This sampling method does not require additional isolation components, thereby reducing overall system costs. The sampling resistor is placed in the lower bridge arm of the power switch (i.e., between the power device and ground), and sampling is performed by measuring the current flowing through the lower bridge arm.

[0052] 2. Output sampling: By measuring the current flowing out of the inverter output terminal, it provides more accurate current readings and is suitable for high power applications or occasions where high-precision current measurement is required.

[0053] 3. Neutral point current sampling: The three-phase current is inferred by measuring the current at the neutral point of the motor bridge arm. It is mostly used in specific multi-phase motor control scenarios.

[0054] As an implementation, when current passes through the sampling resistor, the sampling module 101 measures a voltage drop across the resistor. The voltage drop is proportional to the current passing through the resistor, and the sampling module 101 outputs the voltage signal.

[0055] The voltage generation module 102 is used to generate the zero-bias voltage required by the system. It has two output terminals: one for the first switching terminal of the switch module 103, and one for the second switching terminal of the switch module 103. The voltage generation module 102 generates a stable zero-bias voltage, which is combined with the sampled voltage output by the sampling module 101 and then supplied to the first switching terminal of the switch module 103. The zero-bias voltage is also output to the second switching terminal of the switch module 103.

[0056] The main function of the switch module 103 is to switch the sampling voltage and the zero-bias voltage including the zero-bias voltage. The switch module 103 has three ports: a first switching terminal, a second switching terminal and a common terminal. According to the instruction of the control module 104, the switch module 103 can switch the common terminal to be connected to the first switching terminal to output the sampling voltage and the zero-bias voltage, and can also switch the common terminal to the second switching terminal to output the zero-bias voltage.

[0057] Control module 104 is responsible for controlling the switching operation of switch module 103 and collecting the corresponding voltage signal. Control module 104 receives the voltage signal from the common terminal of switch module 103 via the signal acquisition terminal. Based on system requirements, control module 104 sends a control signal to the control terminal of switch module 103 via the output terminal, controlling switch module 103 to switch to the first switching terminal or the second switching terminal to receive the sampled voltage and the zero-bias voltage, or to receive the zero-bias voltage. That is, during operation, control module 104 can continuously receive the zero-bias voltage. Control module 104 can use the zero-bias voltage as a reference voltage to accurately determine and calibrate other measurement signals, or use the zero-bias voltage for system calibration and compensation.

[0058] The technical effect of the technical solution of this embodiment is that: by setting up a voltage generation module, the zero-bias voltage only needs to be generated once, which reduces the complexity and cost of the circuit, and the single zero-bias voltage source reduces the fluctuations caused by different generation methods, thereby improving the accuracy of current sampling, reducing the impact of external interference on the system, and improving the reliability and stability of the system.

[0059] As an implementation method, Figure 2 As shown, the power supply end of the voltage generating module 102 and the power supply end of the sampling module 101 are connected to the same power supply VCC, and the third voltage output end of the voltage generating module 102 is connected to the power supply end of the control module 104 to convert the voltage of the power supply and then power the control module 104.

[0060] In addition to generating a stable zero-bias voltage, the voltage generation module 102 also provides power conversion for the control module 104. The voltage generation module 102 receives input voltage from a common power supply with the sampling module 101 and, through internal voltage stabilization and regulation circuitry, generates multiple voltage outputs, including a zero-bias voltage and a power supply voltage. The zero-bias voltage is output to the switching module 103 and then to the control module 104 for reference voltage and signal calibration. The voltage generation module 102 converts the power supply voltage into a power supply voltage, providing a stable operating voltage for the control module 104.

[0061] The control module 104 obtains a stable supply voltage from the voltage generation module 102 to ensure its normal operation. It receives signals from the switch module 103, including the sampled voltage and the zero-bias voltage, via the signal acquisition terminal. Based on system requirements, the control module 104 controls the state of the switch module 103 via the output terminal to switch between the sampled signal and the zero-bias voltage. By using the same power supply, the impact of power supply ripple on system stability is reduced. The principle of power supply ripple reduction is based on synchronization and phase offset. In electronic circuits, power supply ripple refers to periodic fluctuations or noise in the supply voltage. These fluctuations can affect the normal operation of the circuit, especially in applications such as high-precision signal processing and measurement. To reduce the impact of power supply ripple, in this circuit design, the voltage generation module 102 generates the supply voltage based on the power supply voltage and outputs it to the control module 104. This can be considered as the voltage generation module 102 and the control module 104 using the same power supply signal. This means that the ripple in the supply voltage is synchronized for all modules using the power supply, i.e., they are aligned in time. Since the zero-bias voltage and the supply voltage are generated from the same power supply signal, their ripple components also appear synchronously. At this time, if the zero-bias voltage generating circuit and the signal processed by the sampling module 101 are both affected by power supply ripples of the same phase and frequency, these ripples may cancel each other out in some cases. Specifically, when the voltage fluctuations caused by the power supply ripple appear in both the zero-bias voltage and the sampled signal, these fluctuations will affect both signals in the same way. Since the sampling module 101 and the zero-bias circuit share the same power supply, this means that the ripple has the same direction and magnitude of impact on both. When the control module 104 calculates the actual signal, it uses the zero-bias voltage as a reference. If both the zero-bias voltage and the sampled signal are affected by the same ripple, then these effects can be canceled out when calculating the actual measurement value.

[0062] The technical effects of this embodiment are as follows: by using a unified power supply and zero-bias voltage source, the voltage mismatch and signal interference between different modules are reduced, the impact of power supply ripple and noise on the system is reduced, and the signal measurement and processing accuracy is improved. Through centralized power management and unified zero-bias voltage setting, the system design and implementation are simplified, and at the same time, the problem that analog signals are susceptible to power noise and power supply disturbances, resulting in zero-bias deviation and causing current waveform jitter, is solved.

[0063] The voltage generation module 102 provides a stable power supply and a reference voltage. The voltage generation module 102 includes but is not limited to the following structures:

[0064] 1. Voltage regulator module: This module regulates the input voltage to a stable output voltage. Common types include linear regulators and switching regulators.

[0065] 2. Switching power supply module: Converts voltage using high-speed switching elements and energy storage components (such as inductors and capacitors). A step-down power supply module reduces high input voltage to a low output voltage. A step-up power supply module increases low input voltage to a high output voltage.

[0066] 3.DC-DC conversion module: Efficiently converts between DC voltages and provides isolated or non-isolated output voltage.

[0067] 4. Precision voltage reference: used to provide high-precision reference voltage, usually used in calibration and high-precision measurement applications.

[0068] 5. Voltage divider circuit: Divides the input voltage proportionally through two or more resistors to generate different voltage outputs.

[0069] As an implementation of the structure of the voltage generating module 102, this implementation is only an example and does not limit the structure of the voltage generating module 102. Figure 3 As shown, the voltage generating module 102 includes a voltage stabilizing unit 201, a synthesizing unit 202 and a voltage dividing unit 203;

[0070] One end of the voltage stabilizing unit 201 is connected to the power supply, and the other end is the third voltage output terminal of the voltage generating module 102, so as to obtain the first zero-bias voltage V1 after stabilizing the voltage of the power supply and supply power to the control module 104;

[0071] A first end of the synthesizing unit 202 is connected to the other end of the voltage stabilizing unit 201, a second end of the synthesizing unit 202 is an input end of the voltage generating module 102, and a third end of the synthesizing unit 202 is a first voltage output end of the voltage generating module 102, so as to synthesize the sampling voltage V0 and the first zero-bias voltage V1;

[0072] The first end of the voltage divider unit 203 is connected to the other end of the voltage stabilizing unit 201, the second end of the voltage divider unit 203 is grounded, and the third end of the voltage divider unit 203 is the second voltage output end of the voltage generating module 102, so as to divide the first zero-bias voltage V1 to obtain the second zero-bias voltage V2 and output it to the switch module 103.

[0073] The main function of the voltage stabilizing unit 201 is to stabilize the power supply voltage to a constant first zero-bias voltage V1 (power supply voltage) for supplying to subsequent circuit modules. Specifically, one end of the voltage stabilizing unit 201 is connected to the power supply, and the other end outputs a stable first zero-bias voltage V1, which powers the control module 104 and also serves as the input voltage for the synthesizing unit 202 and the voltage divider unit 203.

[0074] The function of the synthesis unit 202 is to synthesize the first zero-bias voltage V1 output by the voltage stabilization unit 201 with the sampled voltage V0 to generate a sampled voltage including the zero-bias voltage. The synthesis unit 202 is connected between the output of the voltage stabilization unit 201 and the sampling module 101, and synthesizes the first zero-bias voltage and the sampled voltage via a voltage divider resistor network. The control module 104 identifies the zero-bias voltage within the sampled voltage including the zero-bias voltage, including but not limited to the following methods: During design and testing, a known calibration signal can be used to calibrate the zero-bias voltage; during actual operation, the control module 104 can periodically or when necessary switch to these calibration signals and confirm the magnitude and stability of the zero-bias voltage by comparing them with known values; alternatively, the control module 104 can utilize digital signal processing techniques, such as low-pass filtering, to extract low-frequency components from the signal, which are typically the zero-bias voltage. Because the frequency range of the actual measured signal may be wider, the components remaining after low-frequency filtering are primarily the zero-bias voltage, with the remainder being the sampled voltage. Alternatively, the control module uses a software algorithm to dynamically correct and compensate for the zero-bias voltage. For example, by monitoring the changing trend and statistical characteristics of the output signal in real time, the stable bias voltage component can be identified and compensated.

[0075] The function of voltage divider unit 203 is to divide the first zero-bias voltage V1 output by voltage stabilizing unit 201 to generate a second zero-bias voltage V2. Voltage divider unit 203 is similarly connected to the output of voltage stabilizing unit 201 and operates similarly to synthesizing unit 202, but its voltage division ratio may differ. The generated second zero-bias voltage V2 is output to switch module 103 for output to control module 104 during switching operations. By configuring a voltage divider resistor network, a proportional relationship between the first zero-bias voltage V1 and the second zero-bias voltage V2 can be established.

[0076] The technical effect of this embodiment is that: by setting up a voltage stabilizing unit, a stable first zero-bias voltage is obtained. Through the design of the synthesis unit and the voltage divider unit, the first zero-bias voltage and the sampling voltage can be synthesized and output to the first switching end of the switch module, and the first zero-bias voltage is divided to obtain a second zero-bias voltage, which is output to the second switching end of the switch module. Through the coordinated work of the voltage stabilizing unit, the synthesis unit, the voltage divider unit and the switch module, a stable supply of zero-bias voltage is ensured. On this basis, the control module can accurately perform signal processing and system control based on the zero-bias voltage, thereby ensuring the stability and reliability of the system performance.

[0077] As an implementation of the voltage stabilizing unit 201, Figure 4 As shown, the voltage stabilizing unit 201 includes a first resistor R1, a first capacitor C1 and a voltage stabilizing diode ZD;

[0078] The first end of the first resistor R1 is one end of the voltage stabilizing unit 201. The second end of the first resistor R1, the cathode of the voltage stabilizing diode ZD, and the first end of the first capacitor C1 are commonly connected to form the other end of the voltage stabilizing unit 201. The anode of the voltage stabilizing diode ZD and the second end of the first capacitor C1 are commonly connected to ground.

[0079] The power supply voltage passes through the first resistor R1, which limits the current flowing through the Zener diode ZD, thereby protecting the Zener diode ZD. The first resistor R1, the Zener diode ZD, and the first capacitor C1 form a voltage divider network. The function of the Zener diode ZD is to start conducting and maintain the cathode voltage at a constant voltage value when its cathode voltage reaches its nominal voltage value (i.e., the regulated voltage value). This voltage value is the regulated voltage of the Zener diode ZD. The anode of the Zener diode ZD is grounded, so the cathode voltage is stabilized at the regulated voltage value of the Zener diode ZD relative to the ground voltage. For example, if a 5V Zener diode is used, the output regulated voltage is 5V. The first capacitor C1 is used for filtering, eliminating noise and fluctuations in the voltage, making the output voltage more stable. The stabilized voltage (first zero-bias voltage) after voltage stabilization can be used as the input voltage for subsequent circuit modules (such as the synthesis unit 202 and the voltage divider unit 203). The first zero-bias voltage is generally a relatively stable DC voltage, which is provided to other circuits to ensure the normal operation of other circuit modules.

[0080] The technical effect of this embodiment is that the voltage stabilizing unit adjusts and stabilizes the input voltage by using the first resistor, the first capacitor and the voltage regulator tube, outputs a constant first zero-bias voltage, and provides reliable power supply for subsequent circuit modules of the system.

[0081] As an embodiment of the synthesis unit 202, Figure 4 As shown, the synthesis unit 202 includes a second resistor R2 and a third resistor R3;

[0082] The first end of the second resistor R2 is the second end of the synthesis unit 202 . The second end of the second resistor R2 and the first end of the third resistor R3 are connected together to form the third end of the synthesis unit 202 . The second end of the third resistor R3 is the first end of the synthesis unit 202 .

[0083] The first end of the second resistor R2 is connected to the sampling voltage V0, and the second end of the third resistor R3 is connected to the first zero-bias voltage V1. Then, the output voltage of the synthesis unit 202 is:

[0084]

[0085] R2 is the resistance of the second resistor R2, and R3 is the resistance of the third resistor R3.

[0086] Furthermore, the above formula can be simplified as:

[0087]

[0088] The resistance of the second resistor R2 is the same as the resistance of the third resistor R3.

[0089] The technical effect of this embodiment is that the main function of the synthesis unit is to synthesize different voltage sources (zero-bias voltage and sampling voltage) into an output voltage. By adjusting the ratio of resistors in the synthesis unit, the proportion of zero-bias voltage and sampling voltage in the synthesized signal can be effectively controlled to ensure the accuracy and consistency of the output signal.

[0090] As an implementation of the voltage dividing unit 203, Figure 4 As shown, the voltage dividing unit 203 includes a fourth resistor R4 and a fifth resistor R5;

[0091] The first end of the fourth resistor R4 is the first end of the voltage divider unit 203 . The second end of the fourth resistor R4 and the first end of the fifth resistor R5 are connected together to form the third end of the voltage divider unit 203 . The second end of the fifth resistor R5 is the second end of the voltage divider unit 203 .

[0092] The first end of the fourth resistor R4 is connected to the first zero-bias voltage V1, and the output voltage of the voltage divider unit 203, the second zero-bias voltage V2, is:

[0093]

[0094] Wherein, R4 is the resistance value of the fourth resistor R4, and R5 is the resistance value of the fifth resistor R5.

[0095] It can be seen from the formula of the synthesis unit 202 and the formula of the voltage divider unit 203 that by setting the value of the resistor, the zero-bias voltage included in the sampled voltage can be made identical to the output second zero-bias voltage, that is, during the switching process of the switch module 103, the control module 104 can always obtain the same zero-bias voltage.

[0096] Regarding the switch module 103 in this embodiment, the switch module 103 is used to control the on and off of the current path in the electronic circuit, including but not limited to the following switching devices: MOSFET (metal oxide semiconductor field effect transistor), BJT (bipolar junction transistor), relay (Relay), solid-state relay (SSR), optocoupler (OptoCoupler), switch integrated circuit (Switch ICs), IGBT (insulated gate bipolar transistor), etc.

[0097] As an implementation method, the switch module 103 may include the two switch devices mentioned above, such as Figure 5As shown, the switch module 103 includes a first switch device 301 and a second switch device 302; one end of the first switch device 301 is the first switching end of the switch module 103, one end of the second switch device 302 is the second switching end of the switch module 103, the other end of the first switch device 301 and the other end of the second switch device 302 are connected together as the common end of the switch module 103, and the control end of the first switch device 301 and the control end of the second switch device 302 are respectively connected to the output end of the control module 104.

[0098] The control module 104 generates a control signal that alternately turns on the first switching device 301 and the second switching device 302. When the control module 104 outputs a control signal to turn on the first switching device 301, one end of the first switching device 301 is connected to the common terminal. In this case, a signal path connects the first switching terminal to the common terminal, transmitting the first zero-bias voltage and the sampled voltage to the control module 104. When the control module 104 outputs a control signal to turn on the second switching device 302, one end of the second switching device 302 is connected to the common terminal. In this case, a signal path connects the second switching terminal to the common terminal, transmitting the second zero-bias voltage to the control module 104.

[0099] Furthermore, the inverter includes at least one phase bridge arm and a sampling resistor, an upper bridge arm switch tube and a lower bridge arm switch tube are provided on both sides of the midpoint of the bridge arm, the sampling resistor and the lower bridge arm switch tube are connected in series, and the sampling end of the sampling module 101 is connected to the sampling resistor;

[0100] The control module 104 synchronously sends PWM control signals to the upper bridge arm switch tube, the lower bridge arm switch tube, the first switch device 301 and the second switch device 302 respectively, so as to control the first switching terminal and the common terminal of the switch module 103 to be conductive when the sampling resistor is working, and to control the second switching terminal and the common terminal of the switch module 103 to be conductive when the sampling resistor is not working.

[0101] The control module 104 generates a PWM control signal to control the bridge arm of the sampling resistor and the switch device of the switch module 103. The control module 104 sends a specific PWM signal to the bridge arm to cause current to flow through the sampling resistor. Simultaneously, the control module 104 also sends a PWM signal to the switch module 103 to ensure that the first switch device 301 of the switch module 103 is turned on synchronously with the operating state of the sampling resistor. Specifically, when sampling the sampling resistor, the control module 104 turns on the first switch device 301 of the switch module 103, connecting the first switching terminal to the common terminal. The sampled voltage and the first zero-bias voltage are transmitted to the control module 104 during the sampling process. When the sampling resistor is not operating or in a dormant state, the control module 104 controls the second switch device 302 of the switch module 103 to turn on via a PWM signal. At this time, the second switching terminal is connected to the common terminal, and the control module 104 receives the second zero-bias voltage independently.

[0102] The technical effect of this embodiment is that: this technical solution generates a PWM control signal through the control module, accurately controlling the operating state of the bridge arm of the sampling resistor and the switch module. The PWM signal synchronously controls the operating state of the sampling resistor and the switch module, ensuring the correct transmission of the sampling voltage and zero-bias voltage when sampling the current, ensuring the precise controllability and consistency of the sampling process, and reducing signal distortion and measurement. When the sampling resistor is operating, the first switch device of the switch module is turned on, connecting the sampling voltage and the first zero-bias voltage path; when the sampling resistor is not operating, the second switch device is turned on, transmitting the second zero-bias voltage. This allows for flexible selection and switching of signal paths to meet the needs of different operating states, enabling the control module to receive the zero-bias voltage at any time. This continuous zero-bias voltage monitoring capability allows the system to be adjusted at any time to ensure the stability of control and measurement accuracy.

[0103] The sampling module 101 is used for performing lower bridge sampling, including but not limited to the following implementations: shunt resistor sampling, voltage divider sampling, operational amplifier sampling, isolation amplifier sampling, Hall effect sensor sampling, etc.

[0104] As an implementation mode, this implementation mode is only an example and does not limit the structure of the sampling module 101. Figure 6As shown, the sampling module 101 includes an operational amplifier U1, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10 and a second capacitor C2. One end of the sixth resistor R6 is a first sampling end and is connected to the first end of the sampling resistor R0. The other end of the sixth resistor R6 is respectively connected to the non-inverting input terminal of the operational amplifier U1 and one end of the seventh resistor R7. The other end of the seventh resistor R7 is connected to the output terminal of the operational amplifier U1 and one end of the tenth resistor R10. One end of the eighth resistor R8 is a second sampling end and is connected to the second end of the sampling resistor R0. The other end of the eighth resistor R8 is connected to the inverting input terminal of the operational amplifier U1 and one end of the ninth resistor R9. The other end of the ninth resistor R9 is grounded. The other end of the tenth resistor R10 and one end of the second capacitor C2 are commonly connected to the output terminal of the sampling module 101. The other end of the second capacitor C2 is grounded.

[0105] The calculation formula of the output voltage of the sampling module 101 is:

[0106]

[0107] Wherein, R7 is the resistance value of the seventh resistor R7, R6 is the resistance value of the sixth resistor R6, V IN is the input voltage, V OUT1 is the output voltage of the sampling module 101.

[0108] The circuit structure of this embodiment is a typical differential amplifier, which is used to amplify the difference between two input signals and can effectively suppress common-mode noise. It is particularly suitable for environments with large common-mode voltages. Through the combination of operational amplifiers and resistors, the differential amplifier can provide high-precision and high-gain signal processing.

[0109] The present embodiment is described in detail below through the specific circuit of the inverter current sampling circuit:

[0110] like Figure 7As shown, the inverter current sampling circuit includes a sampling module 101, a voltage generation module 102, a switch module 103, a control module 104, and an inverter N1. The circuit connections between the sampling module 101 and the voltage generation module 102 have been described in the above embodiment and will not be repeated here. The switch module 103 includes a first logic switch K1, a second logic switch K2, a resistor R11, and a capacitor C3. One end of the first logic switch K1 serves as the first switching end of the switch module 103, and one end of the second logic switch K2 serves as the second switching end of the switch module 103. The other ends of the first logic switch K1, the second logic switch K2, and one end of the resistor R11 are connected together. The other end of the resistor R11 and one end of the capacitor C3 are connected together to form the common end of the switch module 103. The other end of the capacitor C3 is grounded. The control module 104 is a DSP chip. The output end of the DSP chip is connected to the control end of the first logic switch K1 and, through the inverter N1, to the control end of the second logic switch K2.

[0111] This circuit structure is based on the topology of a general frequency converter and adopts a lower bridge sampling method. The sampling resistors are placed between the lower bridge arm switch tube and the ground. The sampling resistor analog signal is based on the negative bus, eliminating the isolation device in the sampling circuit. The sampling resistor converts the current signal into a voltage signal. The sampling resistor resistance is R, the frequency converter current is I, and the analog voltage drop U generated at this time is:

[0112] U=RI.

[0113] The sampling module 101 includes an operational amplifier circuit and corresponding feedback link parameter settings. Since the subsequent logic switch signal can only transmit a positive signal, a zero-bias circuit needs to be added to the circuit. The zero-bias circuit is generated by a power supply consistent with the operational amplifier as input. At the same time, the power supply voltage V1 generated should be consistent with the power supply voltage of the DSP chip port. Using the same power supply signal, the power supply ripple will offset the internal ripple of the chip, offsetting the impact of the power supply ripple and increasing the sampling accuracy. The circuit uses the same power supply to generate a zero-bias voltage once to meet the operation of the entire system. The resistance values ​​of resistors R2 and R3 are consistent, and the resistance values ​​of resistors R4 and R5 are consistent. The circuit can be composed of this circuit and can be written as:

[0114]

[0115] Among them, V OUT2 is the output voltage of the voltage generation module, and U1 is the V1 terminal voltage.

[0116] At this point, the amplified voltage is an analog signal that can be sampled and processed by the DSP.

[0117] The control signal of the switch module 103 is the control signal for the lower bridge sampling. Since the current of the lower bridge is only the current to be sampled when the lower tubes of each phase are turned on, a PWM control switch is required for sampling. At the same time, when some lower tubes are not turned on, it is also necessary to sample the standby zero-bias voltage at this time to achieve software modulation. The PWM signal is the control signal generated by the DSP. This PWM signal is the drive signal for the lower bridge. Assuming that the drive signal is triggered at a high level, the first logic switch K1 is turned on and the second logic switch K2 is turned off. At this time, Figure 7 The circuit can be simplified to Figure 8 If the driving signal is low at this time, the first logic switch K1 is disconnected and the second logic switch K2 is turned on. Figure 7 The circuit can be simplified to Figure 9 The equivalent circuit shown in the figure and the corresponding relationship between the equivalent circuit and each module are shown in the following table:

[0118]

[0119]

[0120] By switching the first logic switch K1 and the second logic switch K2 through a PWM control signal, the DSP chip can always receive the zero-bias voltage. In addition, the DSP chip port input part inputs V1 and cooperates with the voltage generation module 102 to achieve power supply ripple suppression.

[0121] Example 2

[0122] The second embodiment provides a frequency converter, including the frequency converter current sampling circuit and sampling resistor provided in the first embodiment.

[0123] like Figure 10As shown, the inverter also includes a rectifier module, a pre-charge module, a capacitor array, a three-phase bridge arm and a motor. The rectifier module includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5 and a diode D6. The capacitor array includes a plurality of parallel capacitor branches, each capacitor branch includes two capacitors C in series. The pre-charge module includes a switch K3 and a resistor R15 connected in parallel. The three-phase bridge arm includes a first phase bridge arm, a second phase bridge arm and a third phase bridge arm. The first phase bridge arm includes a first upper bridge arm switch tube S1, a first lower bridge arm switch tube S4 and a sampling resistor R20. The first phase bridge arm is located at The midpoint between the first upper arm switching tube S1 and the first lower arm switching tube S4 is connected to the U-phase coil of the motor M. The second phase bridge arm includes the second upper arm switching tube S2, the second lower arm switching tube S5 and the sampling resistor R30. The midpoint between the second upper arm switching tube S2 and the second lower arm switching tube S5 on the second phase bridge arm is connected to the V-phase coil of the motor M. The third phase bridge arm includes the third upper arm switching tube S3, the first lower arm switching tube S6 and the sampling resistor R40. The midpoint between the third upper arm switching tube S3 and the first lower arm switching tube S6 on the third phase bridge arm is connected to the W-phase coil of the motor M.

[0124] The inverter current sampling circuit in this embodiment can collect the current of at least one of the sampling resistors R20 , R30 , and R40 .

[0125] By setting the above-mentioned structure of the inverter current sampling circuit, the utility model solves the problem that the analog signal is susceptible to power noise and power supply disturbance, thereby causing zero-bias deviation to cause current waveform jitter, and solves the problem of needing to perform two zero-bias circuit designs. Only one zero-bias voltage needs to be generated to ensure the normal operation of the system, reducing the system complexity, and solving the problem of zero-bias voltage fluctuation caused by the different ways of generating two zero-bias reference voltages, thereby improving the sampling accuracy.

[0126] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A frequency converter current sampling circuit, characterized in that: include: Sampling module, voltage generation module, switch module and control module; The sampling module outputs a sampling voltage according to the sampling signal; The input end of the voltage generating module is connected to the output end of the sampling module, the first voltage output end is connected to the first switching end of the switching module, and the second voltage output end is connected to the second switching end of the switching module to generate a zero-bias voltage, and the zero-bias voltage and the sampling voltage are synthesized and output to the first switching end, and the zero-bias voltage is output to the second switching end; The signal acquisition end of the control module is connected to the common end of the switch module, the output end of the control module is connected to the control end of the switch module, and the control module controls the common end of the switch module to switch on the first switching end or the second switching end to receive the sampling voltage including the zero-bias voltage or the zero-bias voltage.

2. The inverter current sampling circuit according to claim 1, characterized in that: The power supply end of the voltage generating module and the power supply end of the sampling module are connected to the same power supply, and the third voltage output end of the voltage generating module is connected to the power supply end of the control module to convert the voltage of the power supply and then power the control module.

3. The inverter current sampling circuit according to claim 2, characterized in that: The voltage generating module includes a voltage stabilizing unit, a synthesizing unit and a voltage dividing unit; One end of the voltage stabilizing unit is connected to the power supply, and the other end is the third voltage output end of the voltage generating module, so as to obtain a first zero-bias voltage after stabilizing the voltage of the power supply and supply power to the control module; The first end of the synthesis unit is connected to the other end of the voltage stabilizing unit, the second end of the synthesis unit is the input end of the voltage generating module, and the third end of the synthesis unit is the first voltage output end of the voltage generating module, so as to synthesize the sampling voltage and the first zero-bias voltage; The first end of the voltage divider unit is connected to the other end of the voltage stabilizing unit, the second end of the voltage divider unit is grounded, and the third end of the voltage divider unit is the second voltage output end of the voltage generating module, so as to obtain a second zero-bias voltage after dividing the first zero-bias voltage and output it to the switching module.

4. The inverter current sampling circuit according to claim 3, characterized in that: The voltage stabilizing unit includes a first resistor, a first capacitor and a voltage stabilizing tube; The first end of the first resistor is one end of the voltage stabilizing unit, the second end of the first resistor, the cathode of the voltage stabilizing diode and the first end of the first capacitor are connected together as the other end of the voltage stabilizing unit, and the anode of the voltage stabilizing diode and the second end of the first capacitor are connected to the ground.

5. The inverter current sampling circuit according to claim 3, characterized in that: The synthesis unit includes a second resistor and a third resistor; The first end of the second resistor is the second end of the synthesis unit, the second end of the second resistor and the first end of the third resistor are connected together to form the third end of the synthesis unit, and the second end of the third resistor is the first end of the synthesis unit.

6. The inverter current sampling circuit according to claim 3, characterized in that: The voltage dividing unit includes a fourth resistor and a fifth resistor; The first end of the fourth resistor is the first end of the voltage divider unit, the second end of the fourth resistor and the first end of the fifth resistor are connected together to form the third end of the voltage divider unit, and the second end of the fifth resistor is the second end of the voltage divider unit.

7. The inverter current sampling circuit according to any one of claims 1 to 6, characterized in that: The switch module includes a first switch device and a second switch device; One end of the first switching device is the first switching end of the switching module, one end of the second switching device is the second switching end of the switching module, the other end of the first switching device and the other end of the second switching device are connected together as the common end of the switching module, and the control end of the first switching device and the control end of the second switching device are respectively connected to the output end of the control module.

8. The inverter current sampling circuit according to claim 1 or 2, characterized in that: The sampling module includes an operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor and a second capacitor, one end of the sixth resistor is a first sampling end, the other end of the sixth resistor is respectively connected to the non-inverting input end of the operational amplifier and one end of the seventh resistor, the other end of the seventh resistor is connected to the output end of the operational amplifier and one end of the tenth resistor, one end of the eighth resistor is a second sampling end, the other end of the eighth resistor is connected to the inverting input end of the operational amplifier and one end of the ninth resistor, the other end of the ninth resistor is grounded, the other end of the tenth resistor and one end of the second capacitor are connected together as the output end of the sampling module, and the other end of the second capacitor is grounded.

9. A frequency converter, characterized in that: include: The inverter current sampling circuit according to any one of claims 1 to 8.

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