Multi-fan locked-rotor detection circuit and medical instrument

Abstract

The utility model discloses a locked-rotor detection circuit for multiple fans and a medical instrument, and belongs to the technical field of medical instruments, and the circuit comprises N fan detection branches which are the same in structure and are respectively used for detecting the operation conditions of the N fans; the logic judgment module is connected with the N fan detection branches and used for judging whether locked-rotor occurs in the N fans or not according to signals output by the N fan detection branches; wherein the fan detection branch circuit comprises a signal sampling module, a signal processing module and a control module; the signal sampling module is used for detecting the rotating speed of a fan and outputting a square signal; the filtering module is connected with the signal sampling module and is used for filtering the square wave signal to obtain a filtered signal; the buffering module is connected with the filtering module and is used for buffering the filtering signal; and the comparison and judgment module is connected with the buffer module and is used for comparing the buffer signal with a preset signal to obtain a target comparison signal. Through the circuit, locked-rotor detection of multiple fans can be realized.

Description

Technical Field

[0001] The utility model relates to the technical field of medical devices, and particularly relates to a stall detection circuit for multiple fans and a medical device. Background Art

[0002] Many current electronic instruments generate excess heat during normal operation. If the electronic instruments cannot timely dissipate this heat, it will not only affect the operating performance of the electronic instruments, but also pose great potential safety hazards, such as: explosion, combustion, etc. of the electronic instruments.

[0003] To avoid the occurrence of the above problems, fans are usually used to dissipate heat from the electronic instruments. And, to ensure the good operation of the fans, it is also necessary to detect the operating state of the fans in real time. However, the existing fan stall detection circuits can only detect the operation of one fan and cannot detect the stall of multiple fans. Currently, there is no relatively effective solution to this technical problem. Summary of the Utility Model

[0004] In view of this, the purpose of the utility model is to provide a stall detection circuit for multiple fans and a medical device to solve the problem that the operation of multiple fans cannot be detected for stall in the prior art. The specific scheme is as follows:

[0005] To solve the above technical problem, the utility model provides a stall detection circuit for multiple fans, including: N fan detection branches with the same structure, respectively used to detect the operation status of N fans; and a logic judgment module connected to all N fan detection branches, used to judge whether there is a fan with a stall among the N fans according to the signals output by the N fan detection branches; N≥2;

[0006] Wherein, the fan detection branch includes:

[0007] A signal sampling module used to detect the rotation speed of the fan and output a target square wave signal;

[0008] A filtering module connected to the signal sampling module, used to filter the target square wave signal to obtain a target filtered signal;

[0009] A buffering module connected to the filtering module, used to buffer the target filtered signal to obtain a target buffered signal;

[0010] A comparison and judgment module connected to the buffering module, used to compare the target buffered signal with a preset signal to obtain a target comparison signal.

[0011] Preferably, the signal sampling module includes a first resistor;

[0012] Wherein, the first end of the first resistor is used to receive the rotation speed signal of the fan, and the second end of the first resistor is connected to VCC.

[0013] Preferably, the filtering module is specifically a passive second-order RC filter.

[0014] Preferably, the buffering module includes: a first operational amplifier;

[0015] Wherein, the positive input terminal of the first operational amplifier is used to receive the target filtered signal, the negative input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier, and the output terminal of the first operational amplifier outputs the target buffered signal.

[0016] Preferably, the filtering module includes:

[0017] A second-order active Butterworth low-pass filter for filtering the target square wave signal;

[0018] An anti-oscillation circuit connected to the second-order active Butterworth low-pass filter for eliminating the oscillation signal brought by the cascading of the operational amplifier in the second-order active Butterworth low-pass filter and the first operational amplifier to obtain the target filtered signal.

[0019] Preferably, the second-order active Butterworth low-pass filter includes: a second resistor, a third resistor, a first capacitor, a second capacitor, and a second operational amplifier;

[0020] Wherein, the second end of the second resistor is respectively connected to the first end of the third resistor and the first end of the first capacitor, the second end of the first capacitor is connected to the output terminal of the second operational amplifier, the second end of the third resistor is respectively connected to the first end of the second capacitor and the positive input terminal of the second operational amplifier, the second end of the second capacitor is grounded, and the negative input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier;

[0021] Correspondingly, the first end of the second resistor is used to receive the target square wave signal.

[0022] Preferably, the anti-oscillation circuit includes: a fourth resistor, a third capacitor, and the second operational amplifier;

[0023] Wherein, the negative input terminal of the second operational amplifier is correspondingly replaced by: being respectively connected to the first end of the fourth resistor and the first end of the third capacitor, and the second end of the fourth resistor is respectively connected to the second end of the third capacitor and the output terminal of the second operational amplifier.

[0024] Preferably, the comparison and judgment module includes: a third operational amplifier, a fifth resistor, and a sixth resistor;

[0025] Among them, the first end of the fifth resistor is connected to VCC, the second end of the fifth resistor is respectively connected to the negative input end of the third operational amplifier and the first end of the sixth resistor, and the second end of the sixth resistor is grounded;

[0026] Correspondingly, the positive input end of the third operational amplifier is used to receive the target buffer signal, and the output end of the third operational amplifier is used to output the target comparison signal.

[0027] Preferably, the logic judgment module is specifically a logic circuit built by an OR gate.

[0028] To solve the above technical problems, the present utility model also provides a medical device, including a multi-fan stall detection circuit as disclosed above.

[0029] Beneficial effects: In the multi-fan stall detection circuit provided by the present utility model, there are N fan detection branches with the same structure, respectively used to detect the operating conditions of N fans, and a logic judgment module connected to all N fan detection branches, used to judge whether there is a stalled fan among the N fans according to the signals output by the N fan detection branches. Each fan detection branch includes: a signal sampling module, a filtering module, a buffering module, and a comparison and judgment module; among them, the signal sampling module is used to detect the rotation speed of the fan and output a target square wave signal; then, the filtering module filters the target square wave signal to obtain a target filtered signal; afterwards, the buffering module buffers the target filtered signal to obtain a target buffer signal; finally, the comparison and judgment module compares the target buffer signal with a preset signal to obtain a target comparison signal. In this circuit, each fan detection branch can detect the operating state of the fan, and the logic judgment module can also judge whether there is a stalled fan among the N fans according to the signals output by the N fan detection branches, thus realizing the stall detection of multiple fans.

[0030] Correspondingly, a medical device provided by the present application also has the above beneficial effects. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present utility model. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0032] Figure 1 It is a structural diagram of a multi-fan stall detection circuit provided by an embodiment of the present utility model;

[0033] Figure 2 The structural diagram of another stall detection circuit for multiple fans provided by the embodiment of the present invention;

[0034] Figure 3 The structural diagram of yet another stall detection circuit for multiple fans provided by the embodiment of the present invention. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] Please refer to Figure 1 , Figure 1 The structural diagram of a stall detection circuit for multiple fans provided by the embodiment of the present invention. The circuit includes: N fan detection branches 11 with the same structure, respectively used to detect the operating conditions of N fans; and a logic judgment module 12 connected to all N fan detection branches 11, used to judge whether there is a stall in the N fans according to the signals output by the N fan detection branches 11; N≥2;

[0037] Among them, the fan detection branch 11 includes:

[0038] A signal sampling module 101 used to detect the rotation speed of the fan and output a target square wave signal;

[0039] A filtering module 102 connected to the signal sampling module 101, used to filter the target square wave signal to obtain a target filtered signal;

[0040] A buffering module 103 connected to the filtering module 102, used to buffer the target filtered signal to obtain a target buffered signal;

[0041] A comparison and judgment module 104 connected to the buffering module 103, used to compare the target buffered signal with a preset signal to obtain a target comparison signal.

[0042] In this embodiment, a locked-rotor detection circuit for multiple fans is provided, and this circuit can be used to detect the locked-rotor conditions of multiple fans in real time. In this locked-rotor detection circuit, N fan detection branches 11 with the same structure and a logic judgment module 12 are provided. Among them, each fan detection branch 11 can detect the operating condition of one fan, and the logic judgment module 12 can judge whether there is a fan with a locked-rotor phenomenon among the N fans according to the signals output by the N fan detection branches 11.

[0043] Specifically, a signal sampling module 101, a filtering module 102, a buffering module 103, and a comparison and judgment module 104 are provided in the fan detection branch 11. Among them, the signal sampling module 101 is used to detect the rotation speed of the fan and convert the rotation speed signal of the fan into a target square wave signal; when the signal sampling module 101 outputs the target square wave signal, the filtering module 102 filters the target square wave signal to remove the high-frequency signals in the target square wave signal, so as to obtain a target filtered signal; then, the buffering module 103 buffers the target filtered signal to obtain a target buffered signal; finally, the comparison and judgment module 104 compares the target buffered signal with a preset signal to obtain a target comparison signal. Among them, by comparing the target buffered signal with the preset signal, it can be judged whether the target comparison signal is a high-level signal or a low-level signal.

[0044] When the fan is in a normal operating state, the fan detection branch 11 outputs a low-level signal. When the fan detection branch 11 outputs a high-level signal, it indicates that the fan connected to the fan detection branch 11 has a locked-rotor or non-rotation situation. At this time, according to the output signal of the fan detection branch 11, it can be judged whether the fan in this path has a locked-rotor phenomenon.

[0045] It is not difficult to think that in this circuit, since it can be judged whether the fan in each fan detection branch 11 has a locked-rotor according to the output signal of each fan detection branch 11, and the logic judgment module 12 can integrate the output signals of the N fan detection branches 11, so at this time, through the pre-set judgment logic and combined with the judgment of the logic gate circuit, it can be determined whether there is a fan with a locked-rotor phenomenon among these N fans, and thus the locked-rotor detection of multiple fans can be realized.

[0046] When the logic judgment module 12 detects that the fan has a locked-rotor phenomenon, the logic judgment module 12 can also transmit the detected locked-rotor signal to the subsequent controller, so as to alarm the locked-rotor situation of the fan. In this setting method, the problem that the instrument equipment cannot dissipate heat in time due to the locked-rotor of the fan can be effectively avoided, and thus the occurrence probability of safety accidents can be reduced.

[0047] Based on the above embodiments, the technical solution is further described and optimized in this embodiment. Please refer to Figure 2 , Figure 2 which is the structural diagram of another stall detection circuit for multiple fans provided by the embodiment of the present invention. As a preferred implementation manner, the signal sampling module 101 includes a first resistor R1;

[0048] wherein, the first end of the first resistor R1 is used to receive the rotation speed signal of the fan, and the second end of the first resistor R1 is connected to VCC.

[0049] For the convenience of those skilled in the art to understand, in Figure 2 two fan detection branches are listed to perform stall detection on the operation conditions of two fans. In Figure 2 , INPUT-1 and INPUT-2 respectively represent the rotation speed signals of two fans.

[0050] Specifically, in this embodiment, the signal sampling module 101 is set as the first resistor R1. The first resistor R1 is essentially a pull-up resistor, and through this pull-up resistor, the rotation speed signal of the fan can be converted into a target square wave signal.

[0051] In practical applications, the rotation speed signal generation circuit of the fan is a circuit built by a triode (generally built by NPN), and the output rotation speed signal is the voltage signal on the collector. At this time, using the pull-up resistor can pull this signal up to VCC. After sampling, the rotation speed signal of the fan will be a square wave signal with a constant duty cycle, usually 50%, and its amplitude ranges from zero to VCC. When the fan stalls or is not connected, the sampling signal output by the first resistor R1 at this time is the DC voltage signal of VCC.

[0052] In other words, when the rotation speed of the fan is constant and the fan is in a normal operation state, the target square wave signal sampled by the pull-up resistor will be a voltage signal with a fixed frequency. When the fan stalls or is not connected to the circuit, the target square wave signal sampled by the pull-up resistor will be a voltage signal with a frequency almost zero, which can be considered close to DC.

[0053] Based on the above embodiments, the technical solution is further described and optimized in this embodiment. Please refer to Figure 2 , Figure 2 which is the structural diagram of another stall detection circuit for multiple fans provided by the embodiment of the present invention. As a preferred implementation manner, the buffer module 103 includes: a first operational amplifier U1;

[0054] Among them, the positive input terminal of the first operational amplifier U1 is used to receive the target filtering signal. The negative input terminal of the first operational amplifier U1 is connected to the output terminal of the first operational amplifier U1, and the output terminal of the first operational amplifier U1 outputs the target buffer signal.

[0055] In this embodiment, the buffer module 103 can be set as the first operational amplifier U1, that is, an operational amplifier is used to form a buffer. Since the input impedance of the first operational amplifier U1 is large and the output impedance is small, and it has a strong impedance transformation effect, therefore, using the first operational amplifier U1 can achieve the function of buffering the signal for the subsequent circuit.

[0056] As a preferred implementation manner, the filtering module 102 includes:

[0057] A second-order active Butterworth low-pass filter for filtering the target square wave signal;

[0058] An anti-oscillation circuit, connected to the second-order active Butterworth low-pass filter, for eliminating the oscillation signal brought by the cascading of the operational amplifier in the second-order active Butterworth low-pass filter and the first operational amplifier to obtain the target filtering signal.

[0059] In this embodiment, the filtering module 102 can be set as a second-order active Butterworth low-pass filter, and the second-order active Butterworth low-pass filter is used to filter out the high-frequency signals in the target square wave signal. Since there is an operational amplifier in the second-order active Butterworth low-pass filter, and this operational amplifier and the first operational amplifier U1 may cause an oscillation phenomenon, therefore, in order to avoid the oscillation phenomenon in the circuit, an anti-oscillation circuit can also be set in the filtering module, and the anti-oscillation circuit is used to eliminate the oscillation signal in the circuit.

[0060] As a preferred implementation manner, the second-order active Butterworth low-pass filter includes: a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, and a second operational amplifier U2;

[0061] Among them, the second end of the second resistor R2 is respectively connected to the first end of the third resistor R3 and the first end of the first capacitor C1. The second end of the first capacitor C1 is connected to the output terminal of the second operational amplifier U2. The second end of the third resistor R3 is respectively connected to the first end of the second capacitor C2 and the positive input terminal of the second operational amplifier U2. The second end of the second capacitor C2 is grounded. The negative input terminal of the second operational amplifier U2 is connected to the output terminal of the second operational amplifier U2;

[0062] Correspondingly, the first end of the second resistor R2 is used to receive the target square wave signal.

[0063] In this embodiment, the setting structure of the second-order active Butterworth low-pass filter is specifically described. Among them, the second-order active Butterworth low-pass filter is composed of a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, and a second operational amplifier U2. The second-order active Butterworth low-pass filter can effectively filter out the high-frequency signals in the target square-wave signal and convert the target square-wave signal into a DC signal with a small ripple and a fixed level. The amplitude of this DC signal is approximately VCC / 2.

[0064] As a preferred embodiment, the anti-oscillation circuit includes: a fourth resistor R4, a third capacitor C3, and a second operational amplifier U2;

[0065] Among them, the negative input terminal of the second operational amplifier U2 is correspondingly replaced with: being respectively connected to the first terminal of the fourth resistor R4 and the first terminal of the third capacitor C3, and the second terminal of the fourth resistor R4 is respectively connected to the second terminal of the third capacitor C3 and the output terminal of the second operational amplifier U2.

[0066] In this embodiment, the anti-oscillation circuit is specifically described. Among them, the anti-oscillation circuit is composed of a fourth resistor R4, a third capacitor C3, and a second operational amplifier U2. Using this circuit can effectively prevent the oscillation phenomenon generated in the circuit.

[0067] It should be noted that in practical applications, the filtering value of the second-order active Butterworth low-pass filter can be set according to the rotation speed of the fan, and the values of the fourth resistor R4 and the third capacitor C3 can be specifically determined according to the setting parameters of other components in the circuit.

[0068] In addition, when using the second-order active Butterworth low-pass filter to filter the target square-wave signal, its frequency response in the passband is flat, and there will be no amplitude distortion or phase delay. It not only has a fast response speed but also has a high conversion rate. At the same time, after setting the anti-oscillation circuit in the circuit, it can not only eliminate the oscillation signals in the circuit but also improve the transmission quality of the signals.

[0069] Based on the above embodiments, this embodiment further illustrates and optimizes the technical solution. Please refer to Figure 2 , Figure 2 which is the structural diagram of another multi-fan stall detection circuit provided by the embodiment of the present invention. As a preferred embodiment, the comparison and judgment module 104 includes: a third operational amplifier U3, a fifth resistor R5, and a sixth resistor R6;

[0070] Among them, the first terminal of the fifth resistor R5 is connected to VCC, the second terminal of the fifth resistor R5 is respectively connected to the negative input terminal of the third operational amplifier U3 and the first terminal of the sixth resistor R6, and the second terminal of the sixth resistor R6 is grounded;

[0071] Correspondingly, the positive input terminal of the third operational amplifier U3 is used to receive the target buffer signal, and the output terminal of the third operational amplifier U3 is used to output the target comparison signal.

[0072] In this embodiment, the comparison and judgment module 104 is specifically described. The comparison and judgment module 104 is composed of a third operational amplifier U3, a fifth resistor R5, and a sixth resistor R6. After the fifth resistor R5 and the sixth resistor R6 perform voltage division, a preset signal is obtained. The preset signal is input to the negative input terminal of the third operational amplifier U3, and the target buffer signal output by the buffer module is input to the positive input terminal of the third operational amplifier U3. At this time, the third operational amplifier U3 forms a voltage comparison circuit.

[0073] When the fan is running normally, the voltage at the positive input terminal of the third operational amplifier U3 is less than the voltage at its negative input terminal. At this time, the third operational amplifier U3 outputs a low-level signal. When the fan is blocked or not connected, the voltage at the positive input terminal of the third operational amplifier U3 is greater than the voltage at its negative input terminal. At this time, the third operational amplifier U3 outputs a high-level signal. According to the signal at the output terminal of the third operational amplifier U3, it can be judged whether the fan connected to the fan detection branch is blocked.

[0074] It should be noted that in this embodiment, the third operational amplifier U3 can also be set as a comparator. Moreover, in order to ensure the reliability of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3 during the circuit operation, VCC is also connected to the power supply terminals of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3, and the ground terminals of the first operational amplifier U1, the second operational amplifier U2, and the third operational amplifier U3 are grounded.

[0075] Based on the above embodiment, this embodiment further illustrates and optimizes the technical solution. As a preferred implementation manner, the logic judgment module 12 is specifically a logic circuit built by an OR gate.

[0076] In practical applications, multiple OR gates can be used to build the logic judgment module. In this case, as long as one of the N fan detection branches outputs a high-level signal, the logic judgment module 12 will output a high-level signal. At this time, it can be determined that there must be a fan with a blocked rotation phenomenon among the N fans. Only when all the output signals of the N fan detection branches are low-level signals, the logic judgment module 12 will output a low-level signal. At this time, it means that all these N fans are in normal operation.

[0077] It should be noted that in actual operation, the logic judgment module 12 can be set as an OR gate with N input terminals and one output terminal, or the logic judgment module 12 can be set as a combinational circuit of multiple OR gates. When the logic judgment module 12 is set as a combination of multiple OR gates, the number of OR gates and the number of input ports of each OR gate can also be adaptively adjusted according to the number of fan detection branches to build the logic judgment module, as long as the logic judgment module can judge whether there is a fan with a stuck-rotor phenomenon among the N fans based on the signals output by the N fan detection branches.

[0078] In Figure 2 the shown stuck-rotor detection circuit, there is an OR gate OR, which has two input terminals and one output terminal. Through the output signal of the OR gate OR, it can be judged whether the fans in the two fan detection branches connected to its previous stage have a stuck-rotor phenomenon.

[0079] Obviously, through the technical solution provided by this embodiment, the stuck-rotor detection of multiple fans can be realized.

[0080] Based on the above embodiment, this embodiment further illustrates and optimizes the technical solution. Please refer to Figure 3 , Figure 3 which is the structural diagram of another stuck-rotor detection circuit for multiple fans provided by the embodiment of the present invention. As a preferred implementation manner, the filtering module 102 is specifically a passive second-order RC filter.

[0081] In actual application, the filtering module 102 can also be set as a passive second-order RC filter, and the high-frequency signals in the target square wave signal are filtered out by using the passive second-order RC filter. In addition, it should be noted that if the filtering module 102 is set as a passive first-order RC filter, the internal resistor will consume part of the voltage, and the signal loss is relatively large. The filtering effect on the square wave signal output by the signal sampling module is poor, the detection accuracy is not ideal, and misjudgment is likely to occur. When the filtering module 102 is set as a passive second-order RC filter, the above problems can be avoided.

[0082] Obviously, through the technical solution provided by this embodiment, the flexibility and diversity in the construction process of the multiple-fan stuck-rotor detection circuit can be improved.

[0083] Refer to Figure 2 and Figure 3As can be seen from the multi-fan stall detection circuit shown, this application only uses relatively common circuit modules to build the multi-fan stall detection circuit. Compared with using an IO (Input / Output) interface on a microcontroller to detect the rotation speed of one fan respectively and requiring the use of a timer in the microcontroller and the use of pre-set calculation logic to detect the stall of multiple fans, through such a setting method, not only can the consumption of the microcontroller's computing resources be reduced, but also the number of IO interfaces occupied on the microcontroller can be reduced. At the same time, the logic complexity during the stall detection of multiple fans can also be reduced.

[0084] Correspondingly, this embodiment also provides a medical device, including a multi-fan stall detection circuit as disclosed above.

[0085] In practical applications, many medical devices have relatively strict limitations on their operating temperatures during use. For example, mass spectrometers, vaccine storage devices, etc. Therefore, when a multi-fan stall detection circuit is set in these medical devices, the safety and reliability of such medical devices during actual use can be further improved.

[0086] The medical device provided in this embodiment has the beneficial effects of a multi-fan stall detection circuit as disclosed above.

[0087] 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 obvious to those skilled in the art, and the general principles defined herein can 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 locked-rotor detection circuit for multiple fans, characterized in that, Including: N fan detection branches with the same structure, each for detecting the operating conditions of N fans; And a logic judgment module connected to the N fan detection branches, for judging whether there is a stall in the N fans according to the signals output by the N fan detection branches; N≥2； Wherein, the fan detection branch includes: A signal sampling module for detecting the rotation speed of the fan and outputting a target square wave signal; A filtering module connected to the signal sampling module, for filtering the target square wave signal to obtain a target filtered signal; A buffering module connected to the filtering module, for buffering the target filtered signal to obtain a target buffered signal; A comparison and judgment module connected to the buffering module, for comparing the target buffered signal with a preset signal to obtain a target comparison signal.

2. The stall detection circuit of a multi-fan according to claim 1, wherein The signal sampling module includes a first resistor; Wherein, the first end of the first resistor is used to receive the rotation speed signal of the fan, and the second end of the first resistor is connected to VCC.

3. The blocked-rotation detection circuit of a multi-fan according to claim 1, wherein The filtering module is specifically a passive second-order RC filter.

4. The blocked-rotor detection circuit of a multi-fan according to claim 1, characterized in that, The buffering module includes: a first operational amplifier; Wherein, the positive input terminal of the first operational amplifier is used to receive the target filtered signal, the negative input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier, and the output terminal of the first operational amplifier outputs the target buffered signal.

5. The stall detection circuit of a multi-fan according to claim 4, characterized in that, The filtering module includes: A second-order active Butterworth low-pass filter for filtering the target square wave signal; An anti-oscillation circuit connected to the second-order active Butterworth low-pass filter, for eliminating the oscillation signal caused by the cascading of the operational amplifier in the second-order active Butterworth low-pass filter and the first operational amplifier to obtain the target filtered signal.

6. The blocked-rotation detection circuit of a multi-fan according to claim 5, wherein, The second-order active Butterworth low-pass filter includes: a second resistor, a third resistor, a first capacitor, a second capacitor and a second operational amplifier; Wherein, the second end of the second resistor is respectively connected to the first end of the third resistor and the first end of the first capacitor, the second end of the first capacitor is connected to the output terminal of the second operational amplifier, the second end of the third resistor is respectively connected to the first end of the second capacitor and the positive input terminal of the second operational amplifier, the second end of the second capacitor is grounded, and the negative input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier; Correspondingly, the first end of the second resistor is used to receive the target square wave signal.

7. The blocked-rotation detection circuit of a multi-fan according to claim 6, characterized in that, The anti-oscillation circuit includes: a fourth resistor, a third capacitor and the second operational amplifier; ​ 8. The blocked-rotation detection circuit of a multi-fan according to claim 1, wherein, ​ ​ Correspondingly, the positive input terminal of the third operational amplifier is used to receive the target buffer signal, and the output terminal of the third operational amplifier is used to output the target comparison signal.

9. The blocked-rotation detection circuit of a multi-fan according to claim 1, wherein The logic judgment module is specifically a logic circuit built by an OR gate.

10. A medical device, characterized in that, It includes a stall detection circuit for multiple fans according to any one of claims 1 to 9.

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