A DC bus voltage detection circuit, method and inverter

Abstract

The present invention discloses a voltage detection circuit, method and frequency converter for a DC bus. By periodically controlling the on and off of a switch, the voltage on the DC bus is converted into an AC signal, thereby effectively avoiding the detection error caused by the fluctuation of the chopping frequency and the duty cycle in the forward-type transformer. In this way, the voltage conversion process becomes more stable and controllable, which not only improves the accuracy of the voltage signal, but also reduces the delay problem caused by the conversion. The processing circuit performs real-time detection based on the voltage signal output by the secondary coil, and can quickly respond to the change of the DC bus voltage, thereby improving the dynamic performance and control accuracy of the system, and effectively solving the problem of insufficient accuracy and real-time performance of bus voltage detection in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency converters, and in particular to a voltage detection circuit and method for a DC bus and a frequency converter. Background Art

[0002] Detecting the DC bus voltage is of great significance in the inverter system. It not only ensures the effective transmission and storage of electric energy and the normal operation of the system, but also directly affects the output power of the motor and the working status of the inverter. By monitoring the DC bus voltage in real time, potential faults can be discovered and handled in a timely manner to prevent motor overload, damage and accidents, thereby improving the safety and reliability of the system. In addition, the detection of the DC bus voltage also provides a basis for the control strategy of the inverter, helps to optimize system performance, and ensures that the inverter meets the strict safety standards and specifications of various countries and regions.

[0003] In the prior art, a forward transformer is used to isolate and convert the bus voltage, and the secondary output of the transformer is rectified into a DC voltage for detection. However, due to the characteristics of the forward transformer, the secondary output voltage is not only related to the bus voltage, but also directly affected by the chopping frequency and duty cycle. When the system chopping frequency fluctuates greatly, the detection error of the transformer output voltage will increase significantly, resulting in a decrease in the accuracy and real-time performance of the bus voltage detection. In addition, due to the existence of the conversion process, the detection signal will have a certain delay, which may lead to an untimely response to the change of the DC bus voltage, affecting the dynamic performance and control accuracy of the system. Summary of the invention

[0004] The purpose of the present invention is to provide a DC bus voltage detection circuit, method and inverter, which improve the dynamic performance and control accuracy of the system and effectively solve the problem of insufficient bus voltage detection accuracy and real-time performance in the prior art.

[0005] In a first aspect, the present application provides a DC bus voltage detection circuit, comprising:

[0006] A switch, a transformer and a processing circuit, wherein the transformer includes a primary coil and a secondary coil, wherein:

[0007] One end of the primary coil is connected to the first end of the DC bus, the second end of the primary coil is connected to the second end of the DC bus through the switch, and the two ends of the secondary coil are respectively connected to the two input ends of the processing circuit;

[0008] The switch is used to periodically turn on and off to convert the DC voltage on the DC bus into an AC voltage;

[0009] The transformer is used to isolate and convert the AC voltage to obtain a voltage signal;

[0010] The processing circuit is used to detect the voltage signal output by the secondary coil and determine the DC voltage according to the voltage signal.

[0011] Optionally, the processing circuit is specifically configured to be triggered when the rising edge of the voltage signal is identified to arrive, and to detect the voltage signal after a preset delay time after the triggering, and to determine the DC voltage according to the voltage signal.

[0012] Optionally, also include:

[0013] A filter circuit, wherein two input terminals are connected to two ends of the secondary coil respectively, and two output terminals are connected to two input terminals of the processing circuit respectively;

[0014] The filtering circuit is used to filter out the peaks in the voltage signal.

[0015] Optionally, the filtering circuit includes a first resistor and a first capacitor, wherein the first end of the first resistor is connected to the first end of the secondary coil, the second end of the first resistor is respectively connected to the first end of the first capacitor and the first end of the processing circuit, and the second end of the first capacitor is respectively connected to the second end of the secondary coil and the second end of the processing circuit.

[0016] Optionally, also include:

[0017] A second resistor has a first end connected to the first end of the first resistor, the first end of the first capacitor and the first end of the processing circuit respectively, and a second end connected to the second end of the first capacitor and the second end of the processing circuit respectively.

[0018] Optionally, also include:

[0019] The voltage follower has a positive input terminal connected to the first end of the first resistor and the first end of the first capacitor, and a negative input terminal connected to its own output terminal and the first end of the processing circuit respectively.

[0020] Optionally, also include:

[0021] An overvoltage protection circuit, wherein a first input terminal is connected to the DC bus, a reference voltage is input to a second input terminal, and an output terminal is connected to a control terminal of the switch, and is used for outputting a control signal to a drive circuit when the DC voltage of the DC bus is greater than the reference voltage, so that the drive circuit drives the switch to be continuously disconnected; wherein the drive circuit outputs a preset pulse width signal when the DC voltage is not greater than the reference voltage to cause the switch to be periodically turned on and off.

[0022] Optionally, the overvoltage protection circuit includes:

[0023] A reference voltage source, used for outputting the reference voltage;

[0024] A voltage comparator, whose non-phase input terminal is connected to the DC bus, whose inverting input terminal is connected to the reference voltage source, and whose output terminal is connected to the drive circuit, is used to output the control signal to the drive circuit when the voltage at its own non-phase input terminal is greater than the voltage at its inverting input terminal, so that the drive circuit drives the switch to be continuously disconnected.

[0025] In a second aspect, the present application provides a frequency converter, comprising a DC bus and a voltage detection circuit of the DC bus as described above, wherein the voltage detection circuit of the DC bus is connected to the DC bus.

[0026] In a third aspect, the present application provides a DC bus voltage detection method, which is applied to the DC bus voltage detection circuit as described above, comprising:

[0027] Obtaining a voltage signal output by the secondary coil, and obtaining a turns ratio between the primary coil and the secondary coil;

[0028] The amplitude of the voltage signal is determined, and the voltage of the DC bus is determined according to the amplitude of the voltage signal and the turns ratio.

[0029] The present invention discloses a voltage detection circuit, method and frequency converter of a DC bus. By periodically controlling the on and off of a switch, the voltage on the DC bus is converted into an AC signal. The isolation and conversion functions of the transformer are used to directly perform voltage detection in the AC domain. The amplitude of the AC signal is directly related to the absolute value of the DC bus voltage and is not affected by the chopping frequency and the duty cycle. Therefore, even if the chopping frequency fluctuates greatly, the detection result of the secondary output voltage can still accurately reflect the true value of the DC bus voltage, avoiding the direct influence of the chopping frequency and the duty cycle on the secondary output voltage, thereby improving the accuracy and real-time performance of the detection. At the same time, since the detection is performed in the AC domain, the detection of the AC voltage can directly utilize the fast response characteristics of the transformer without going through a complex DC to DC conversion process, reducing the delay in the conversion process, making the response to the change of the DC bus voltage more timely, and solving the problems of detection error and conversion delay. The processing circuit performs real-time detection according to the voltage signal output by the secondary coil, and can quickly respond to the change of the DC bus voltage, thereby improving the dynamic performance and control accuracy of the system, and effectively solving the problem of insufficient accuracy and real-time performance of the bus voltage detection in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. 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 creative work.

[0031] Figure 1 A schematic diagram of a voltage detection circuit for a DC bus provided by the present invention;

[0032] Figure 2 A preferred schematic diagram of a DC bus voltage detection circuit provided by the present invention;

[0033] Figure 3 A preferred schematic diagram of another DC bus voltage detection circuit provided by the present invention;

[0034] Figure 4 The present invention provides a flow chart of a method for detecting a voltage of a DC bus. DETAILED DESCRIPTION

[0035] The core of the present invention is to provide a DC bus voltage detection circuit, method and inverter, which improve the dynamic performance and control accuracy of the system and effectively solve the problem of insufficient bus voltage detection accuracy and real-time performance in the prior art.

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] First, as Figure 1 As shown, the present application provides a DC bus voltage detection circuit, comprising:

[0038] Switch Q1, transformer T1 and processing circuit, transformer T1 includes a primary coil and a secondary coil, where:

[0039] One end of the primary coil is connected to the first end of the DC bus, the second end of the primary coil is connected to the second end of the DC bus through the switch Q1, and the two ends of the secondary coil are respectively connected to the two input ends of the processing circuit;

[0040] The switch Q1 is used to periodically turn on and off to convert the DC voltage on the DC bus into an AC voltage;

[0041] Transformer T1 is used to isolate and convert the AC voltage to obtain a voltage signal;

[0042] The processing circuit is used to detect the voltage signal output by the secondary coil and determine the DC voltage according to the voltage signal.

[0043] In this embodiment, the function of the switch Q1 is to periodically turn on and off the current to control the conversion process of the DC voltage on the DC bus. Specifically, each time the switch Q1 is turned on, the voltage of the DC bus will be transmitted to the secondary coil of the transformer T1 through the primary coil. When turned off, the bus voltage is isolated to prevent the continuous application of the DC bus voltage from affecting the secondary side of the transformer T1. Because if the DC voltage is continuously applied to the secondary coil of the transformer, it will cause the transformer to saturate, thereby affecting the normal operation of the transformer and may even damage the transformer. Through the periodic conduction and shutdown of the switch Q1, the DC bus voltage can be effectively isolated to avoid its continuous influence on the secondary coil of the transformer, ensuring the normal operation of the transformer and the accuracy of detection. Through periodic conduction and shutdown, the switch Q1 converts the DC voltage into a pulsed AC voltage. This AC signal has a certain frequency and duty cycle. The changes in frequency and duty cycle can reflect the dynamic characteristics of the DC bus voltage, so that the subsequent processing circuit can more accurately extract and identify voltage information, which is convenient for processing.

[0044] Transformer T1 isolates and converts AC voltage through the coupling of the primary coil and the secondary coil. The primary coil receives the pulse signal from the DC bus (generated by switch Q1) and converts the DC signal into an AC signal. The secondary coil is connected to the input end of the processing circuit to receive the AC voltage signal isolated by transformer T1. The function of transformer T1 is not only to isolate the signal and prevent the bus voltage from interfering with the processing circuit, but also to appropriately convert the input voltage by changing the turns ratio of the secondary coil to generate a voltage signal suitable for the processing circuit.

[0045] The main function of the processing circuit is to detect and analyze the voltage signal output by the secondary coil. The processing circuit may include, but is not limited to, functional modules such as amplification, filtering, and rectification, which are used to improve the quality of the signal and remove noise and unnecessary high-frequency components. By processing the secondary coil signal, the circuit can accurately restore the original voltage level on the DC bus. The processing circuit calculates the voltage value of the DC bus by analyzing the output signal of the secondary coil and combining the known conversion ratio of the transformer T1, thereby completing real-time monitoring of the bus voltage. Among them, the processing circuit may not be limited to an MCU.

[0046] The specific working process of this embodiment is as follows: when the switch Q1 is turned on, the DC voltage on the DC bus is transmitted to the transformer T1 through the primary coil. At this time, the DC voltage will generate a pulse signal in the primary coil, converting the DC voltage into an AC voltage. The primary coil of the transformer T1 receives the pulsed DC voltage from the bus and converts it into an AC voltage, while electrically isolating the signal. The secondary coil receives the isolated AC signal and transmits it to the processing circuit. The processing circuit optimizes the AC voltage signal output by the secondary coil by means of amplification, filtering, etc., to ensure the accuracy and stability of the signal. The processing circuit determines the voltage value of the DC bus based on the signal, and calculates the DC voltage in combination with the conversion ratio of the transformer T1. When the switch Q1 is turned off, the DC bus voltage no longer affects the transformer T1, and the circuit enters a dormant state, waiting for the next cycle to be turned on. By periodically turning on and off the switch Q1, the system realizes continuous monitoring of the DC bus voltage.

[0047] In this way, the circuit can measure the DC bus voltage in real time and accurately, and use the isolation and conversion functions of the transformer to perform voltage detection directly in the AC domain. The amplitude of the AC signal is directly related to the absolute value of the DC bus voltage and is not affected by the chopping frequency and duty cycle. Therefore, even if the chopping frequency fluctuates greatly, the detection result of the secondary output voltage can still accurately reflect the true value of the DC bus voltage, avoiding measurement errors caused by frequency and duty cycle fluctuations, and ensuring the stability and safety of the inverter system.

[0048] As an optional embodiment, the processing circuit is specifically configured to be triggered when the rising edge of the voltage signal is recognized to arrive, detect the voltage signal after a preset delay time after the triggering, and determine the DC voltage according to the voltage signal.

[0049] In this embodiment, the trigger detection, delay processing, and analysis and calculation of the voltage signal of the processing circuit are further described in detail. Specifically, the processing circuit first receives an AC voltage signal from the secondary coil of the transformer T1. The voltage signal is an AC signal that is periodically converted from the DC voltage on the DC bus through the switch Q1. Since the signal is a periodic pulse signal, each cycle contains a rising edge (i.e., the signal jumps from a low level to a high level). The processing circuit continuously monitors the input signal, and when it detects the arrival of the rising edge of the voltage signal, it triggers subsequent operations in the circuit. This trigger mechanism is usually implemented by a comparator or a zero crossing detection circuit. When the signal rises rapidly from a low level, the circuit immediately responds and starts the subsequent detection process.

[0050] After the rising edge arrives and is triggered, the processing circuit does not immediately detect the voltage signal in real time, but delays for a preset time. This delay is usually set based on the response time of the system, the characteristics of transformer T1, and the requirements of circuit design. The purpose of the delay is to ensure the stability and accuracy of the signal. The pulse signal during the conversion process may have short-term fluctuations or noise. The delay helps filter out these transient effects and ensure that the processing circuit captures a stable and representative voltage signal.

[0051] After the delay is over, the processing circuit starts to detect the voltage signal. At this time, the voltage signal has gone through a sufficient stabilization period, and the processing circuit can accurately read the amplitude and waveform of the signal. According to the preset conversion ratio (for example, the turns ratio of transformer T1), the processing circuit will reversely infer the voltage value of the DC bus according to the AC voltage signal of the secondary coil. The specific detection method in this embodiment is to directly detect the amplitude of the AC signal output by the secondary coil of the transformer T1, and then infer the DC voltage value on the DC bus according to this amplitude and the turns ratio of the transformer T1.

[0052] Once the processing circuit completes the detection and analysis of the voltage signal, it will calculate the actual voltage value of the DC bus based on the obtained voltage signal and the operating characteristics of the transformer T1 (such as parameters such as turns ratio). Since the switch Q1 generates a periodic voltage signal every time it is turned on, the processing circuit can obtain an accurate DC voltage value through multiple measurements and analyses. This value will be used as feedback information for the inverter control system to adjust the system's operating status and optimize the control strategy to ensure safe and stable operation of the system.

[0053] Through the above process, the processing circuit can delay processing and accurately detect the voltage signal after the rising edge of the signal is triggered, thereby achieving high-precision DC bus voltage measurement. This method can effectively avoid errors caused by voltage signal fluctuations or noise interference, and improve the system's response speed and measurement accuracy.

[0054] As an optional embodiment, the voltage detection circuit further includes:

[0055] A filter circuit, wherein two input terminals are connected to two ends of the secondary coil respectively, and two output terminals are connected to two input terminals of the processing circuit respectively;

[0056] Filter circuit, used to filter out spikes in voltage signals.

[0057] In this embodiment, the function of the filtering circuit is to remove the spikes (instantaneous high-frequency noise or interference) in the voltage signal output by the secondary coil to ensure that the subsequent processing circuit can receive a smoother and more stable signal, thereby improving the accuracy and reliability of voltage detection.

[0058] Specifically, the filtering circuit is connected between the secondary coil and the processing circuit. Due to the working principle of transformer T1, the voltage signal output by the secondary coil changes periodically, but it may contain some high-frequency noise or spikes. These spikes are usually caused by the turn-on and turn-off process of switch Q1, magnetic field fluctuations of transformer T1, or external interference sources.

[0059] The two output ends of the filter circuit are connected to the input ends of the processing circuit respectively, transmitting the smooth voltage signal with the spikes filtered out. The processing circuit will receive this relatively stable voltage signal, and then further analyze it to calculate the voltage value of the DC bus. Through filtering, the quality of the voltage signal is greatly improved, and the detection error caused by spike noise is reduced.

[0060] The core function of the filter circuit is to remove high-frequency noise or spikes in the signal through a specific circuit structure (such as capacitors, inductors, resistors, etc.). These spike signals usually have a higher frequency than the target signal (i.e., the change in bus voltage), so the filter circuit can be designed to pass only low-frequency signals (representing the real change in voltage) while suppressing high-frequency spikes.

[0061] Common types of filter circuits include low-pass filters and band-pass filters. Low-pass filters allow signals below a certain cutoff frequency to pass through, while suppressing signals above the frequency. Band-pass filters further enhance the passage of signals in a specific frequency band and suppress noise in other frequency bands. In this embodiment, the filter circuit is generally a low-pass filter, which filters out high-frequency spikes in the voltage signal by setting an appropriate cutoff frequency.

[0062] It can be seen that the filter circuit removes high-frequency spikes and noise in the output voltage signal of the secondary coil by connecting it between the secondary coil and the processing circuit. It ensures that only the low-frequency part (i.e. stable voltage change) is retained in the signal by low-pass filtering, thereby improving the signal quality and avoiding the error caused by spike interference in voltage detection. This processing method can ensure the high accuracy and high reliability of the voltage detection circuit and adapt to more complex and dynamic electrical environments.

[0063] like Figure 1 and Figure 2 As shown, as an optional embodiment, the filtering circuit includes a first resistor R1 and a first capacitor C1, wherein the first end of the first resistor R1 is connected to the first end of the secondary coil, the second end of the first resistor R1 is respectively connected to the first end of the first capacitor C1 and the first end of the processing circuit, and the second end of the first capacitor C1 is respectively connected to the second end of the secondary coil and the second end of the processing circuit.

[0064] Specifically, the filter circuit may include, but is not limited to, a first resistor R1 and a first capacitor C1 to form an RC filter network. The core function of the RC filter network is to smooth the signal through the capacitor and limit the current flow through the resistor, thereby effectively suppressing high-frequency noise and spike signals.

[0065] The function of the first resistor R1 is to limit the flow of current in the signal and, together with the capacitor, determine the cutoff frequency of the filter. The resistor controls the bandwidth of the signal through the filter through interaction with the capacitor, ensuring that high-frequency noise is filtered out while allowing the target signal (usually the low-frequency part) to continue to pass. The resistor can also ensure the stability of the capacitor charging and discharging process to prevent excessive oscillation of the signal. The first capacitor C1 is used to smooth the voltage signal and offset the spikes in the voltage signal through the charging and discharging process. The capacitor can provide a low impedance path for the instantaneous voltage signal, thereby filtering out the high-frequency components, while having less impact on the low-frequency signal. Therefore, the capacitor helps the filter circuit "absorb" instantaneous spikes or noise without changing the main frequency components of the signal.

[0066] Through the above design, the filter circuit can effectively remove high-frequency noise or spikes in the output signal of the secondary coil. The voltage signal of the secondary coil may contain some instantaneous high-frequency spike interference, especially the electromagnetic interference caused by the operation of the switch Q1.

[0067] like Figure 2 As shown, as an optional embodiment, it also includes:

[0068] The second resistor R2 has a first end connected to the first end of the first resistor R1, the first end of the first capacitor C1 and the first end of the processing circuit, and a second end connected to the second end of the first capacitor C1 and the second end of the processing circuit.

[0069] In this optional embodiment, the second resistor R2 is added mainly to adjust the voltage level of the signal to ensure that the voltage transmitted to the processing circuit does not exceed the threshold value that it can safely process. Its working principle is based on the principle of resistor voltage division. By reasonably selecting the resistance value of the second resistor R2, it is ensured that the voltage input to the processing circuit is within an acceptable range, thereby preventing the processing circuit from being damaged or distorted due to excessive input voltage.

[0070] The function of the second resistor R2 is to control the voltage transmitted to the processing circuit by cooperating with the first resistor R1 and the first capacitor C1. By reasonably selecting the resistance value of the second resistor R2, the voltage output by the secondary coil can be divided, and the voltage finally input to the processing circuit is always lower than the maximum input voltage of the processing circuit. In this way, even if the voltage output by the secondary coil fluctuates greatly, the second resistor R2 can control it within a safe range by dividing the voltage, thereby protecting the processing circuit from the influence of overvoltage.

[0071] This design ensures that the processing circuit will not be damaged or unstable due to excessive input voltage. The addition of the second resistor R2 acts like a voltage limiter to ensure that the voltage received by the processing circuit is within its operating range. This plays an important protective role in preventing processing circuit failure due to excessive voltage or false detection due to low voltage.

[0072] like Figure 3 As shown, as an optional embodiment, it also includes:

[0073] The voltage follower U1 has a positive input terminal connected to the first end of the first resistor R1 and the first end of the first capacitor C1, and a negative input terminal connected to its own output terminal and the first end of the processing circuit respectively.

[0074] In this optional embodiment, the addition of the voltage follower U1 is mainly used to further ensure that the voltage input to the processing circuit remains within a safe range, preventing the voltage from exceeding the maximum input value of the processing circuit, thereby protecting the processing circuit from damage. The voltage follower U1 (usually an operational amplifier configuration) has a very high input impedance and a low output impedance. Its function is to "follow" the input voltage and output the same voltage value as the input voltage, basically without introducing additional voltage changes.

[0075] The core function of the voltage follower U1 is to output the input voltage signal through a gain-free transmission mode, and its output voltage is consistent with the input voltage. Therefore, the output voltage of the voltage follower U1 will not exceed its input voltage, ensuring that the signal voltage entering the processing circuit does not exceed the predetermined safety threshold, avoiding damage to the processing circuit due to excessive voltage.

[0076] The introduction of the voltage follower U1 ensures that the voltage does not exceed the safety threshold of the processing circuit when the signal is transmitted to the processing circuit after passing through the voltage follower U1. In this way, the voltage follower U1 not only provides voltage stability, but also plays a protective role, avoiding circuit damage or malfunction due to excessive voltage.

[0077] As an optional embodiment, it also includes:

[0078] An overvoltage protection circuit, wherein a first input terminal is connected to a DC bus, a reference voltage is input to a second input terminal, and an output terminal is connected to a control terminal of a switch Q1, and is used for outputting a control signal to a drive circuit when a DC voltage of the DC bus is greater than a reference voltage, so that the drive circuit drives the switch Q1 to be continuously disconnected; wherein the drive circuit outputs a preset pulse width signal when the DC voltage is not greater than the reference voltage to cause the switch Q1 to be periodically turned on and off.

[0079] In this optional embodiment, the overvoltage protection circuit is used to determine whether an overvoltage condition exists by detecting the relationship between the DC bus voltage and the reference voltage, and to protect the system by controlling the state of the switch Q1 when an overvoltage condition occurs.

[0080] As an optional embodiment, the overvoltage protection circuit includes:

[0081] A reference voltage source, used for outputting a reference voltage;

[0082] A voltage comparator, whose non-phase input terminal is connected to the DC bus, whose inverting input terminal is connected to the reference voltage source, and whose output terminal is connected to the drive circuit, is used to output a control signal to the drive circuit when the voltage at its non-phase input terminal is greater than the voltage at its inverting input terminal, so that the drive circuit drives the switch Q1 to be continuously disconnected.

[0083] The reference voltage source is used to generate a stable reference voltage as a reference voltage for comparison. This reference voltage is a known, safe voltage value used to compare with the voltage of the DC bus. Usually, this reference voltage is set to the maximum safe voltage value that the system can withstand. A voltage comparator is a circuit used to compare two voltage signals. Its main function is to detect the difference between the DC bus voltage (positive input) and the reference voltage (inverting input). When the positive input of the voltage comparator (i.e., the DC bus voltage) is greater than the inverting input (i.e., the reference voltage), the output of the voltage comparator will generate a control signal to inform the drive circuit to trigger the switch Q1 to continue to disconnect, preventing the DC bus voltage from being too high and causing harm to the system. If the voltage at the positive input is less than or equal to the voltage at the inverting input (i.e., the DC bus voltage is within the safe range), the output signal of the voltage comparator will remain low or unchanged.

[0084] The function of the drive circuit is to drive the switch Q1 according to the control signal from the voltage comparator. When the DC bus voltage is greater than the reference voltage, the voltage comparator outputs a control signal. After receiving the signal, the drive circuit drives the switch Q1 to be continuously disconnected, thereby avoiding damage to the system caused by excessive voltage. When the DC bus voltage is not greater than the reference voltage, the voltage comparator outputs a low level or no control signal. The drive circuit periodically drives the switch Q1 to turn on and off according to the set pulse width signal to maintain normal regulation of the DC bus voltage.

[0085] The control of switch Q1 is the responsibility of the drive circuit, which controls the state of switch Q1 according to the output signal of the voltage comparator: in the overvoltage state, when the DC bus voltage is greater than the reference voltage, switch Q1 will continue to be in the disconnected state to ensure that the bus voltage will not continue to rise, thereby protecting downstream equipment from overvoltage; in the normal working state, when the voltage is not greater than the reference voltage, the drive circuit controls the switch Q1 to be periodically turned on and off according to the preset pulse width signal. This periodic control will keep the DC bus voltage within a safe and stable working range.

[0086] The design of the overvoltage protection circuit can effectively prevent the DC bus voltage from being too high. The voltage comparator monitors the real-time voltage of the DC bus and compares it with the reference voltage. Once an overvoltage is detected, the voltage comparator outputs a control signal, and the drive circuit then controls the switch Q1 to remain in the off state, preventing the DC bus voltage from further increasing. If the voltage returns to a safe range, the drive circuit restarts the periodic control of the switch Q1 on and off according to the preset pulse width signal to maintain the normal operation of the system.

[0087] Through the synergy of the reference voltage source, voltage comparator and drive circuit, the overvoltage protection circuit can monitor the DC bus voltage in real time and take effective measures (such as disconnecting switch Q1) when overvoltage occurs to prevent equipment damage caused by overvoltage. At the same time, when the voltage returns to a safe range, the circuit will return to normal working state to ensure stable operation of the system. This protection mechanism not only enhances the safety of the system, but also ensures the long-term stable operation of the equipment.

[0088] In a second aspect, the present application provides a frequency converter, including a DC bus and a voltage detection circuit of the DC bus as described above, wherein the voltage detection circuit of the DC bus is connected to the DC bus.

[0089] For other introductions to the frequency converter, please refer to the above embodiments, which will not be repeated in this application.

[0090] Thirdly, Figure 4 As shown, the present application provides a DC bus voltage detection method, which is applied to the DC bus voltage detection circuit as described above, including:

[0091] S11: obtaining a voltage signal output by the secondary coil, and obtaining a turns ratio between the primary coil and the secondary coil;

[0092] In this step, you first need to obtain a voltage signal from the secondary coil of the transformer. The secondary coil is the output end of the transformer, and the relationship between the voltage at both ends and the voltage at the input end of the transformer (i.e., the primary coil) is affected by the turns ratio. The turns ratio is defined as the ratio of the number of turns of the primary coil to the number of turns of the secondary coil. By obtaining the voltage signal of the secondary coil, the AC voltage information related to the DC bus voltage can be obtained.

[0093] In addition, the turns ratio is a fixed parameter in transformer design, which is used to describe the proportional relationship between the primary and secondary coils. The turns ratio directly affects the voltage change of the transformer during the AC voltage conversion process. Therefore, when performing voltage detection, the turns ratio is a very important parameter, which helps quantify the relationship between the voltage signal output by the secondary coil and the bus voltage.

[0094] S12: Determine the amplitude of the voltage signal, and determine the voltage of the DC bus according to the amplitude of the voltage signal and the turns ratio.

[0095] First, it is necessary to determine the amplitude of the voltage signal output by the secondary coil. Since the output of the secondary coil is an AC voltage converted from the DC bus voltage through periodic switching, a signal proportional to the DC bus voltage can be obtained by measuring its amplitude. At this time, the amplitude of the voltage signal reflects the strength of the DC bus voltage, but since the voltage signal is a converted AC voltage, it is also necessary to use the turns ratio to convert it into the actual voltage of the DC bus.

[0096] The function of the turns ratio is to associate the voltage signal of the secondary coil with the voltage signal of the primary coil, and then establish a relationship with the DC bus voltage. In this way, the voltage value of the DC bus can be calculated by the known amplitude of the secondary coil voltage signal and the turns ratio. In summary, the core principle of this step is to use the amplitude of the voltage signal and the turns ratio for proportional conversion, and then accurately determine the voltage of the DC bus. This process can effectively eliminate the interference caused by factors such as switching frequency and duty cycle, and ensure the accuracy of voltage detection.

[0097] For further introduction to the DC bus voltage detection method, please refer to the above embodiments, and this application will not go into details here.

[0098] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0099] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC bus voltage detection circuit, characterized in that: include: A switch, a transformer and a processing circuit, wherein the transformer includes a primary coil and a secondary coil, wherein: One end of the primary coil is connected to the first end of the DC bus, the second end of the primary coil is connected to the second end of the DC bus through the switch, and the two ends of the secondary coil are respectively connected to the two input ends of the processing circuit; The switch is used to periodically turn on and off to convert the DC voltage on the DC bus into an AC voltage; The transformer is used to isolate and convert the AC voltage to obtain a voltage signal; The processing circuit is used to detect the voltage signal output by the secondary coil and determine the DC voltage according to the voltage signal.

2. The voltage detection circuit of the DC bus according to claim 1, characterized in that: The processing circuit is specifically configured to be triggered when the rising edge of the voltage signal is identified, detect the voltage signal after a preset delay time after the triggering, and determine the DC voltage according to the voltage signal.

3. The voltage detection circuit of the DC bus according to claim 1, characterized in that: Also includes: A filter circuit, wherein two input terminals are connected to two ends of the secondary coil respectively, and two output terminals are connected to two input terminals of the processing circuit respectively; The filtering circuit is used to filter out the peaks in the voltage signal.

4. The voltage detection circuit of the DC bus as claimed in claim 3, characterized in that: The filtering circuit includes a first resistor and a first capacitor, wherein the first end of the first resistor is connected to the first end of the secondary coil, the second end of the first resistor is respectively connected to the first end of the first capacitor and the first end of the processing circuit, and the second end of the first capacitor is respectively connected to the second end of the secondary coil and the second end of the processing circuit.

5. The voltage detection circuit of the DC bus as claimed in claim 4, characterized in that: Also includes: A second resistor has a first end connected to the first end of the first resistor, the first end of the first capacitor and the first end of the processing circuit respectively, and a second end connected to the second end of the first capacitor and the second end of the processing circuit respectively.

6. The voltage detection circuit of the DC bus as claimed in claim 4, characterized in that: Also includes: A voltage follower has a positive input terminal connected to the first end of the first resistor and the first end of the first capacitor, and a negative input terminal connected to its own output terminal and the first end of the processing circuit respectively.

7. The voltage detection circuit of the DC bus according to any one of claims 1 to 6, characterized in that: Also includes: an overvoltage protection circuit, wherein a first input terminal is connected to the DC bus, a reference voltage is input to a second input terminal, and an output terminal is connected to a control terminal of the switch, and is used for outputting a control signal to a drive circuit when the DC voltage of the DC bus is greater than the reference voltage, so that the drive circuit drives the switch to be continuously disconnected; Wherein the driving circuit outputs a preset pulse width signal when the DC voltage is not greater than the reference voltage to enable the switch to be periodically turned on and off.

8. The voltage detection circuit of the DC bus as claimed in claim 7, characterized in that: The overvoltage protection circuit comprises: A reference voltage source, used for outputting the reference voltage; A voltage comparator, whose non-phase input terminal is connected to the DC bus, whose inverting input terminal is connected to the reference voltage source, and whose output terminal is connected to the drive circuit, is used to output the control signal to the drive circuit when the voltage at its non-phase input terminal is greater than the voltage at its inverting input terminal, so that the drive circuit drives the switch to be continuously disconnected.

9. A frequency converter, characterized in that: It comprises a DC bus and a voltage detection circuit of the DC bus according to any one of claims 1 to 8, wherein the voltage detection circuit of the DC bus is connected to the DC bus.

10. A method for detecting a voltage of a DC bus, characterized in that: A voltage detection circuit for a DC bus according to any one of claims 1 to 8, comprising: Obtaining a voltage signal output by the secondary coil, and obtaining a turns ratio between the primary coil and the secondary coil; The amplitude of the voltage signal is determined, and the voltage of the DC bus is determined according to the amplitude of the voltage signal and the turns ratio.

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