A multi-channel temperature sampling circuit inside a frequency converter

Abstract

The utility model discloses a kind of multichannel temperature sampling circuits inside frequency converter, it is related to temperature sampling circuit technical field, and the sampling circuit includes temperature front-end conditioning and synthetic circuit, control circuit and device highest temperature gating circuit and filter protection circuit;The temperature front-end conditioning and synthetic circuit carries out the temperature signal collection of multiple sampling points to N devices respectively, and the temperature signal collected is preliminarily conditioned and screened, obtains the highest temperature sampling signal of N devices;The control circuit and device highest temperature gating circuit carry out ordered gating to the highest temperature sampling signal of N devices;The filter protection circuit carries out optimization and protection to the signal after gating.This sampling circuit realizes efficient, safe monitoring to multichannel temperature signal under single ADC resource condition, solves the technical pain points such as high resource occupation, large signal interference in traditional scheme, significantly improves the reliability of frequency converter temperature monitoring system.

Description

Technical Field

[0001] This utility model relates to the field of temperature sampling circuit technology, specifically to a multi-channel temperature sampling circuit inside a frequency converter. Background Technology

[0002] In the field of industrial automation temperature monitoring, especially in the internal temperature monitoring of frequency converters, the traditional solution usually equips each real-time temperature sampling circuit with an independent ADC (analog-to-digital converter) chip resource, which is then conditioned and fed into the MCU (microcontroller unit) for digital processing. However, when multiple temperature monitoring and sampling of multiple heat-generating devices in the frequency converter are required, this traditional method will consume a large amount of the ADC resources of the main control chip, resulting in resource shortages and increasing system cost and design complexity.

[0003] While some temperature acquisition solutions exist, they are insufficient to efficiently and accurately monitor the real-time temperature of various heat-generating components within the inverter under limited ADC resources of the main control chip. Therefore, there is an urgent need for a solution that can address the problem of real-time monitoring of the temperature of various heat-generating components within the inverter using a single main control chip ADC resource, in order to optimize resource utilization and improve the efficiency and reliability of temperature monitoring. Utility Model Content

[0004] The purpose of this invention is to provide a multi-channel temperature sampling circuit inside a frequency converter to address the shortcomings in the prior art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a multi-channel temperature sampling circuit inside a frequency converter, the sampling circuit including a temperature front-end conditioning and synthesis circuit, a control circuit and a device maximum temperature gating circuit and a filter protection circuit;

[0006] The output of the temperature front-end conditioning and synthesis circuit is electrically connected to the input of the control circuit and the device maximum temperature gating circuit, and the output of the control circuit and the device maximum temperature gating circuit is electrically connected to the input of the filter protection circuit.

[0007] The temperature front-end conditioning and synthesis circuit acquires temperature signals from multiple sampling points for each of the N devices, where N ≥ 2. It performs preliminary conditioning and synthesis on the temperature signals from multiple sampling points for each device to obtain the highest temperature sampling signal for each device. The control circuit and the device highest temperature gating circuit perform ordered gating on the highest temperature sampling signals of the N devices. The filtering and protection circuit optimizes and protects the gated signals.

[0008] Preferably, the control circuit and device maximum temperature selection circuit includes a control circuit, an analog control switch chip, and a second operational amplifier. The control circuit receives the output GPIO control signal from the inverter main control chip DSP. The analog control switch chip switches at fixed times according to the high and low levels issued by the inverter main control chip DSP. The selected signal is then output by the follower circuit composed of the second operational amplifier.

[0009] Preferably, the control circuit controls the SET1 / SET2 ports of the analog control switch chip through GPIO control signals to select to collect the highest temperature sampling signal of device A or device B. The analog control switch chip switches at fixed intervals according to the high and low levels issued by the inverter main control chip DSP, so that the ADC port of the inverter main control chip DSP polls and reads the highest temperature sampling signals of the front-end devices A / B of the analog control switch chip.

[0010] Preferably, the temperature front-end conditioning and synthesis circuit includes multiple temperature front-end conditioning circuits and a temperature synthesis circuit. The temperature front-end conditioning circuit includes an NTC resistor, a voltage divider resistor R1, a voltage divider resistor Rf, and a filter capacitor C1. The temperature synthesis circuit includes a diode D1 and a first operational amplifier. The NTC resistor and the voltage divider resistor Rf are connected in parallel to form a resistor voltage divider network. The voltage divider resistor R1 is connected in series with the resistor voltage divider network and then connected to the reference power supply REF. The temperature front-end conditioning circuit obtains the voltage Untc output by multiple resistor voltage divider networks to represent the temperature signals of multiple sampling points. The temperature synthesis circuit compares and processes the multiple Untc voltages generated in the temperature front-end conditioning circuit and outputs the minimum Untc voltage, which represents the signal of the highest temperature among the multiple sampling points.

[0011] Preferably, the filter capacitor C1 is used to filter out noise and interference in the Untc voltage signal, and the first operational amplifier amplifies or buffers the voltage Untc output by the resistor divider network.

[0012] Preferably, the filter protection circuit includes a resistor R2, a capacitor C2, a diode D2, and a diode D3. The resistor R2 and the capacitor C2 form a low-pass filter circuit, and the diode D2 and the diode D3 form a voltage clamping circuit.

[0013] Preferably, the low-pass filter circuit filters out interference signals in the output signal of the previous stage, and the voltage clamping circuit protects the ADC analog-to-digital converter of the main control chip of the subsequent frequency converter.

[0014] The technical effects and advantages provided by this utility model in the above technical solution are as follows:

[0015] 1. This invention uses a front-end temperature synthesis circuit to filter out the highest temperature (i.e., the minimum Untc voltage) among multiple sampling points of each device. Then, through a control circuit and a device highest temperature gating circuit, an analog control switching chip (such as CD4051 or a multiplexer) is used to switch the highest temperature signals of device A and device B in turn at fixed intervals. Finally, only one ADC resource is needed to complete the polling sampling of the highest temperature of all key devices. This "filter first, then poll" mechanism greatly reduces the ADC resource occupancy rate, enabling a single ADC port to efficiently serve the needs of multiple temperature monitoring channels, significantly improving the system resource utilization efficiency, while reducing hardware costs and design complexity.

[0016] 2. This invention achieves accurate extraction of the highest temperature (i.e., the hottest spot temperature of the device) from multiple temperature sampling points through temperature front-end conditioning and synthesis circuitry. Specifically, each temperature sampling point consists of a resistor voltage divider network formed by an NTC resistor (negative temperature coefficient thermistor) connected in parallel with a voltage divider resistor Rf. Combined with the voltage divider resistor R1 and the reference power supply REF, since the resistance of the NTC resistor decreases significantly with increasing temperature, the smaller the resistance in the resistor voltage divider network, the lower the voltage obtained. Therefore, among the Untc voltages corresponding to multiple sampling points, the minimum Untc voltage is the signal of the sampling point with the highest temperature. This minimum Untc voltage is compared and filtered by a temperature synthesis circuit composed of diode D1 and the first operational amplifier, ultimately outputting a signal representing the highest temperature of the device. This process ensures that the system can accurately focus on the critical temperature points most likely to cause faults (such as the risk area of ​​excessively high junction temperature of power devices), avoid interference from non-critical information in multiple temperature data, and improve the targeting and effectiveness of temperature monitoring.

[0017] 3. This invention significantly improves the reliability and safety of temperature signals through multi-stage signal conditioning and protection circuits. In the front-end conditioning stage, the first operational amplifier amplifies or buffers the Untc voltage output from the resistor divider network, enhancing the signal's driving capability and ensuring stable reception by subsequent circuits (such as diode synthesis circuits). The filter capacitor C1 filters out high-frequency noise and interference in the Untc voltage, making the signal smoother and purer, providing high-quality input for the temperature synthesis circuit. In the gating stage, the follower circuit composed of the second operational amplifier acts as a buffer stage, further enhancing the signal's driving capability and ensuring that the highest temperature signal selected by the analog control switch chip can be transmitted to the subsequent filtering and protection circuit without distortion. In the output protection stage, the low-pass filter circuit composed of resistor R2 and capacitor C2 effectively filters out high-frequency interference signals, ensuring the smoothness of the signal before entering the ADC; the voltage clamping circuit composed of diode D2 and diode D3 strictly limits the input signal within a safe range, preventing damage to the ADC analog-to-digital converter of the downstream inverter main control chip due to abnormal voltage (such as surge or spike pulse), thereby comprehensively ensuring the long-term stable operation of the system and the safety of key electronic components. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings.

[0019] Figure 1 This is a schematic diagram of the sampling circuit of this utility model.

[0020] Figure 2 This is a circuit diagram of the temperature front-end conditioning and synthesis circuit of this utility model.

[0021] Figure 3 This is the circuit diagram for selecting the highest temperature of the control circuit and device of this utility model.

[0022] Figure 4 This is the circuit diagram for the filter protection of this utility model. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0024] The components of the internal multi-channel temperature sampling circuit of the frequency converter are labeled as follows:

[0025] Temperature front-end conditioning and synthesis circuit:

[0026] NTC resistor: Negative temperature coefficient thermistor, is a temperature-sensitive element whose resistance decreases as temperature increases. In a circuit, it is used to sense temperature changes and convert temperature information into changes in resistance, which in turn affects the voltage value.

[0027] Voltage divider resistor R1: A fixed resistor that acts as a voltage divider in the temperature front-end conditioning circuit. Together with other resistors in the circuit, it forms a specific voltage division relationship, providing a suitable voltage ratio for subsequent voltage measurements.

[0028] Voltage divider resistor Rf: It is connected in parallel with the NTC resistor to form a voltage divider network, which participates in the calculation of the voltage corresponding to the measured temperature and further adjusts the voltage after voltage division by the NTC resistor.

[0029] Operational Amplifier 1: Further amplifies or buffers the voltage Untc corresponding to the measured temperature output from the voltage divider network, enhancing the signal's driving capability and ensuring that subsequent circuits can stably receive and process the signal.

[0030] Filter capacitor C1: mainly used to filter out high-frequency noise and interference in the signal, making the voltage Untc signal corresponding to the measured temperature smoother and more stable, improving the signal quality, and providing a cleaner input signal for the subsequent temperature synthesis circuit.

[0031] Diode D1: Together with the first operational amplifier, it forms a temperature synthesis circuit, which participates in comparing and processing multiple Untc voltages generated in the temperature front-end conditioning circuit, and selects the smallest Untc voltage.

[0032] Reference power supply REF: Provides a stable reference voltage Uref for the temperature front-end conditioning circuit, serving as the basis for calculating the voltage Untc corresponding to the measured temperature.

[0033] Control circuit and device maximum temperature gating circuit:

[0034] Control circuit: Receives the output GPIO control signal from the inverter's main control chip DSP, and controls the SET1 / SET2 ports of the analog control switch chip according to the signal to select the highest temperature sampling signal of device A or device B, thereby realizing the selection control of the highest temperature sampling signal of different devices.

[0035] Analog control switch chip: Based on the high and low levels issued by the inverter's main control chip DSP, it switches at fixed intervals, enabling the ADC port of the inverter's main control chip DSP to poll and read the highest temperature signals of different devices in front of the analog control switch chip. The channels of the analog control switch chip can be adjusted according to the number of front-end acquisition devices, and it has good scalability.

[0036] The second operational amplifier forms a follower circuit, which outputs the selected signal, serving to buffer and enhance the driving capability, ensuring that the signal can be stably transmitted to the subsequent circuit.

[0037] The inverter's main control chip, DSP, issues GPIO control signals and high / low level signals to control the working state of the analog control switch chip, enabling the selection and polling of the highest temperature signals of different devices. It is the core control unit of the entire control circuit.

[0038] SET1 / SET2 ports: Control ports on the analog control switch chip, controlled by the control circuit according to the output GPIO control signal of the inverter's main control chip DSP, used to select and collect the highest temperature sampling signal of different devices.

[0039] Filter protection circuit:

[0040] Resistor R2: Together with capacitor C2, it forms a low-pass filter circuit to filter out high-frequency interference signals in the output signal of the previous stage, making the signal smoother and purer.

[0041] Capacitor C2: Together with resistor R2, it forms a low-pass filter circuit to filter out high-frequency interference signals in the output signal of the previous stage and reduce the impact of external interference on subsequent processing.

[0042] Diodes D2 and D3 form a voltage clamping circuit to protect the ADC (Analog-to-Digital Converter) of the main control chip of the downstream frequency converter, preventing damage to the ADC due to excessively high input signal voltage, and ensuring the safety and stability of the entire circuit.

[0043] The ADC analog-to-digital converter of the main control chip of the downstream frequency converter converts the filtered and protected analog signal into a digital signal, enabling real-time monitoring of the highest temperature of each heat-generating component in the frequency converter.

[0044] Example: This example provides a multi-channel temperature sampling circuit inside a frequency converter. Please refer to [link / reference]. Figure 1 As shown, the multi-channel temperature sampling circuit inside the frequency converter aims to solve the problem of real-time monitoring of the temperature of various heat-generating components within the frequency converter using the ADC resources of a single main control chip. It involves temperature front-end conditioning and synthesis circuits, control circuits, a maximum device temperature gating circuit, and a final output filtering and protection circuit. These circuits work together as follows:

[0045] like Figure 2 As shown, the temperature front-end conditioning and synthesis circuit is the starting point of the entire temperature sampling process. It includes multiple temperature front-end conditioning circuits and a temperature synthesis circuit. The temperature front-end conditioning circuit mainly consists of an NTC resistor, voltage divider resistors R1 and Rf, and a filter capacitor C1. The temperature synthesis circuit consists of diode D1 and the first operational amplifier. In the temperature front-end conditioning circuit, the NTC resistor and the voltage divider resistor Rf are connected in parallel to form a resistor divider network. The voltage divider resistor R1 is connected in series with the resistor divider network and then connected to the reference power supply REF. At each sampling point, there is a corresponding temperature front-end conditioning circuit. The voltage Untc output from the multiple resistor divider networks represents the temperature signal at each sampling point. The voltage corresponding to the measured temperature at each sampling point is: The NTC resistor here is a temperature-sensitive element, and its resistance value changes significantly with temperature. Specifically, NTC resistors have a negative temperature coefficient, meaning their resistance decreases as temperature increases. Since temperature and NTC resistance are inversely proportional, the higher the temperature at a sampling point, the lower the NTC resistance. In a resistor divider network, the smaller the resistance, the smaller the voltage drop across the divided resistor. Therefore, among the Untc voltages corresponding to multiple temperature sampling points, the lowest Untc voltage actually represents the highest temperature sampling value of the device.

[0046] The first operational amplifier is used to further amplify or buffer the UnTC voltage output from the resistor divider network to enhance the signal's driving capability and ensure that subsequent circuits can stably receive and process the signal. The filter capacitor C1 is mainly used to filter out high-frequency noise and interference in the signal, making the UnTC voltage signal smoother and more stable, improving signal quality, and providing a cleaner input signal for the subsequent temperature synthesis circuit.

[0047] Diode D1 and the first operational amplifier form a temperature synthesis circuit. This circuit compares and processes multiple Untc voltages generated in the front-end temperature conditioning circuit, and finally outputs the smallest Untc voltage. This smallest Untc voltage represents the signal of the highest temperature among multiple temperature sampling points. For the N (N≧2) devices under test, preliminary conditioning and filtering of the highest temperature among multiple temperature sampling points are performed on each device to obtain the highest temperature sampling signal for each device. The conditioned and filtered signals are then transmitted to the subsequent control circuit and the device highest temperature gating circuit for further processing and detection.

[0048] In summary, the temperature front-end conditioning and synthesis circuit obtains the temperature-related Untc voltage by constructing a resistor voltage divider network, determines the voltage corresponding to the highest temperature by utilizing the temperature characteristics of the NTC resistor, processes and optimizes the signal through the filter capacitor C1, and finally the temperature synthesis circuit selects the signal representing the highest temperature and passes it to the subsequent circuits.

[0049] like Figure 3 As shown, the control circuit and device maximum temperature selection circuit include a control circuit, an analog control switch chip, and a second operational amplifier. The control circuit receives the output GPIO control signal from the inverter's main control chip DSP, and uses this signal to control the SET1 / SET2 ports of the analog control switch chip, thereby selecting to acquire the maximum temperature sampling signal of device A or device B. The analog control switch chip switches between high and low levels based on the high and low levels emitted by the inverter's main control chip DSP for a fixed time. This allows the ADC port of the inverter's main control chip DSP to poll and read the maximum temperature signals of devices A / B in front of the analog control switch chip. This process achieves orderly selection of the maximum temperature signals of different devices, avoiding excessive occupation of the main control chip's ADC resources by simultaneously acquiring multiple signals, and improving the utilization efficiency of ADC resources. The selected signal is then output by a follower circuit composed of the second operational amplifier. The follower circuit acts as a buffer and enhances the driving capability, ensuring that the signal can be stably transmitted to the subsequent circuit. Moreover, the channels of the analog control switch chip can be adjusted according to the number of preceding acquisition devices, providing good scalability.

[0050] like Figure 4 As shown, the filtering and protection circuit consists of resistor R2, capacitor C2, diode D2, and diode D3. It receives signals from the control circuit and the highest temperature selection circuit for the components. Resistor R2 and capacitor C2 form a low-pass filter, which filters out high-frequency interference signals from the previous stage output signal, making the signal smoother and purer, and reducing the impact of external interference on subsequent processing. Diodes D2 and D3 form a voltage clamping circuit, which protects the ADC (Analog-to-Digital Converter) of the inverter's main control chip, preventing damage due to excessively high input signal voltage, and ensuring the safety and stability of the entire circuit. After filtering and protection, the signal can be accurately digitally acquired by the ADC port of the inverter's main control chip, enabling real-time monitoring of the highest temperature of each heat-generating component within the inverter.

[0051] In summary, the temperature front-end conditioning and synthesis circuit is responsible for acquiring temperature signals from multiple sampling points of N devices, and performing preliminary conditioning and filtering on the acquired temperature signals to obtain the highest temperature sampling signal of N devices. The control circuit and the device highest temperature gating circuit perform orderly gating of the highest temperature sampling signals of N devices, making reasonable use of the ADC resources of the inverter's main control chip. Finally, the output filtering and protection circuit optimizes and protects the gated signals to ensure that the signals can be accurately and safely acquired by the inverter's main control chip. The three circuits work closely together to achieve efficient sampling and monitoring of multiple temperature channels inside the inverter.

[0052] Traditional temperature monitoring methods typically monitor individual devices or heat sources, and each real-time temperature sampling circuit requires ADC (Analog-to-Digital Converter) chip resources for conditioning before being processed by the MCU (Microcontroller Unit). In cases with multiple devices and heat sources, this approach consumes significant ADC resources from the main control chip, increasing hardware costs and potentially leading to untimely or incomplete monitoring, failing to accurately grasp the overall temperature status of the equipment.

[0053] The multi-channel temperature sampling circuit inside this frequency converter, through its unique design, can effectively solve the above problems and provide a reliable temperature monitoring solution for the various heat-generating components inside the frequency converter.

[0054] The temperature front-end conditioning and synthesis circuit of this system can perform multi-point temperature sampling on multiple key heat-generating components of the frequency converter. Each sampling point has a corresponding NTC resistor and a corresponding UnTC voltage. Since the NTC resistor has a negative temperature coefficient characteristic, that is, the higher the temperature, the lower the resistance value. In the resistor voltage divider network, the smaller the resistance value, the smaller the voltage obtained. Therefore, among the UnTC voltages corresponding to multiple temperature sampling points, the smallest UnTC voltage actually represents the highest temperature sampling value of the device. The temperature synthesis circuit composed of diode D1 and the first operational amplifier outputs the smallest UnTC voltage in the front-end temperature conditioning circuit, which means that the highest temperature among each key heat-generating component is selected, completing the preliminary conditioning and selection of the highest temperature among multiple temperature sampling points.

[0055] The control circuit and device maximum temperature selection circuit include a control circuit, an analog control switch chip, and a second operational amplifier. The control circuit receives the output GPIO control signal from the inverter's main control chip (DSP), and uses this signal to control the SET1 / SET2 ports of the analog control switch chip, thereby selecting and acquiring the maximum temperature sampling signals of different devices (such as device A and device B). The analog control switch chip switches between high and low levels at fixed intervals according to the high and low levels emitted by the inverter's main control chip (DSP). This allows the ADC port of the inverter's main control chip (DSP) to poll and read the maximum temperature signals of different devices in front of the analog control switch chip. This process achieves orderly selection of the maximum temperature signals of different devices, avoiding excessive occupation of the ADC resources of the main control chip by simultaneously acquiring multiple signals, and improving the utilization efficiency of ADC resources. The selected signal is then output by a follower circuit composed of the second operational amplifier, which acts as a buffer and enhances the driving capability, ensuring that the signal can be stably transmitted to the subsequent circuits. Moreover, the channels of the analog control switch chip can be adjusted according to the number of devices acquired in the preceding stage, providing good scalability.

[0056] The filtering and protection circuit consists of resistor R2, capacitor C2, diode D2, and diode D3. It receives the signal from the control circuit and the highest temperature gating circuit of the components. Resistor R4 and capacitor C2 form a low-pass filter circuit, filtering out high-frequency interference signals in the output signal of the previous stage, making the signal smoother and purer, and reducing the impact of external interference on subsequent processing. Diodes D2 and D3 form a voltage clamping circuit, protecting the ADC (Analog-to-Digital Converter) of the inverter's main control chip, preventing damage to the ADC due to excessively high input signal voltage, and ensuring the safety and stability of the entire circuit. After filtering and protection, the signal can be accurately digitally acquired by the ADC port of the inverter's main control chip.

[0057] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0058] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, thereby enabling those skilled in the art to better understand and utilize it. This utility model is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-channel temperature sampling circuit inside a frequency converter, characterized in that: The sampling circuit includes a temperature front-end conditioning and synthesis circuit, a control circuit and a device maximum temperature gating circuit, as well as a filter protection circuit; The output of the temperature front-end conditioning and synthesis circuit is electrically connected to the input of the control circuit and the device maximum temperature gating circuit, and the output of the control circuit and the device maximum temperature gating circuit is electrically connected to the input of the filter protection circuit. The temperature front-end conditioning and synthesis circuit acquires temperature signals from multiple sampling points for each of the N devices, where N ≥ 2. It performs preliminary conditioning and synthesis on the temperature signals from multiple sampling points for each device to obtain the highest temperature sampling signal for each device. The control circuit and the device highest temperature gating circuit perform ordered gating on the highest temperature sampling signals of the N devices. The filtering and protection circuit optimizes and protects the selected signal.

2. The multi-channel temperature sampling circuit inside a frequency converter according to claim 1, characterized in that: The control circuit and device maximum temperature selection circuit includes a control circuit, an analog control switch chip, and a second operational amplifier. The control circuit receives the output GPIO control signal from the inverter main control chip DSP. The analog control switch chip switches at fixed times according to the high and low levels issued by the inverter main control chip DSP. The selected signal is then output by the follower circuit composed of the second operational amplifier.

3. The multi-channel temperature sampling circuit inside a frequency converter according to claim 2, characterized in that: The control circuit controls the SET1 / SET2 ports of the analog control switch chip through GPIO control signals to select to collect the highest temperature sampling signal of device A or device B. The analog control switch chip switches at fixed intervals according to the high and low levels issued by the inverter main control chip DSP, and the ADC port of the inverter main control chip DSP polls and reads the highest temperature sampling signals of the front-end devices A / B of the analog control switch chip.

4. The multi-channel temperature sampling circuit inside a frequency converter according to claim 1, characterized in that: The temperature front-end conditioning and synthesis circuit includes multiple temperature front-end conditioning circuits and a temperature synthesis circuit. The temperature front-end conditioning circuit includes an NTC resistor, a voltage divider resistor R1, a voltage divider resistor Rf, and a filter capacitor C1. The temperature synthesis circuit includes a diode D1 and a first operational amplifier. The NTC resistor and the voltage divider resistor Rf are connected in parallel to form a resistor voltage divider network. The voltage divider resistor R1 is connected in series with the resistor voltage divider network and then connected to the reference power supply REF. The temperature front-end conditioning circuit obtains the voltage Untc output by multiple resistor voltage divider networks to represent the temperature signals of multiple sampling points. The temperature synthesis circuit compares and processes the multiple Untc voltages generated in the temperature front-end conditioning circuit and outputs the minimum Untc voltage, which represents the signal of the highest temperature among the multiple sampling points.

5. The multi-channel temperature sampling circuit inside a frequency converter according to claim 4, characterized in that: The filter capacitor C1 is used to filter out noise and interference in the Untc voltage signal, and the first operational amplifier amplifies or buffers the voltage Untc output by the resistor divider network.

6. The multi-channel temperature sampling circuit inside a frequency converter according to claim 1, characterized in that: The filtering protection circuit includes resistor R2, capacitor C2, diode D2, and diode D3. Resistor R2 and capacitor C2 form a low-pass filter circuit, and diode D2 and diode D3 form a voltage clamping circuit.

7. The inverter internal multi-channel temperature sampling circuit according to claim 6, characterized in that: The low-pass filter circuit filters out interference signals in the output signal of the previous stage, and the voltage clamping circuit protects the ADC analog-to-digital converter of the main control chip of the subsequent frequency converter.

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