Three-channel elevator brake safety control circuit

Abstract

The present invention discloses a three-channel elevator brake safety control circuit, comprising: a trunk circuit, including a fuse and three terminal switches connected in series therewith, wherein the output of the trunk circuit can be disconnected when any terminal switch is disconnected; three channels, each channel is used to obtain an external safety signal and output a drive signal according to a preset logic to control the conduction or shutdown of the terminal switch; a monitoring circuit is used to diagnose the short-circuit state of each channel and respond according to a preset solution.

Description

Technical Field

[0001] The present invention relates to the field of elevators, and in particular to a three-channel elevator brake safety control circuit. Background Art

[0002] The revised national elevator standard [1] and type test rules [2] now allow the use of a safety circuit to cut off the brake current. The national elevator standard [1] has the following requirements for safety circuits:

[0003] a) If a fault (first fault) combined with a subsequent fault (second fault) results in a dangerous situation, the elevator shall be stopped at the latest during the next operating sequence in which the first faulty component participates. All further operation of the elevator shall be impossible as long as the first fault persists. The possibility of a second fault occurring after the first fault has occurred and before the elevator has been stopped according to the above operating sequence is not taken into account.

[0004] b) If the combination of two faults does not lead to a dangerous situation, but their combination with a third fault will lead to a dangerous situation, the elevator should be stopped at the latest in the next operating sequence in which any of the first two faulty components participates. Before the elevator is stopped according to the above operating sequence, the possibility of a third fault leading to a dangerous situation is not taken into account.

[0005] c) If there is a possibility of three or more faults occurring simultaneously, the safety circuit should have multiple channels and a monitoring circuit that checks the same status in each channel. If different statuses are detected, the elevator should be stopped. In the case of two channels, the function of the monitoring circuit should be checked at the latest before restarting the elevator. If the function fails, restarting the elevator should not be possible.

[0006] d) When the power supply that has been cut off is restored, if the elevator can be forced to stop again under 5.11.2.3.3a), b) and c), the elevator does not need to remain in the stopped position.

[0007] e) In redundant safety circuits, measures shall be taken to limit as far as possible the risk of simultaneous failures in more than one circuit due to a single cause.

[0008] Obviously, according to the above clauses, for the possibility of more than three faults occurring simultaneously, the brake control circuit can be designed according to the following system architecture:

[0009] With up to three channels, a monitoring circuit checks the same status of each channel. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a circuit which can meet the requirements of elevator regulations on elevator brake safety control circuits and realize effective and safe control of elevator brakes.

[0011] To solve the above technical problems, the present invention provides a three-channel elevator brake safety control circuit, comprising:

[0012] A main circuit, comprising a fuse and three terminal switches connected in series, wherein disconnection of any terminal switch can disconnect the output of the main circuit;

[0013] Three channels, each channel is used to obtain an external safety signal and output a drive signal according to a preset logic to control the on or off of the terminal switch;

[0014] Monitoring circuit, used to diagnose the short circuit status of each channel and respond according to the preset plan.

[0015] Preferably, the external safety signal includes an elevator safety circuit signal, an elevator main control circuit signal and a monitoring circuit fault signal;

[0016] When any of the above signals fails, the main circuit has no output;

[0017] When any one of the above signals is valid, the main circuit will have an output only when the other two signals are both valid.

[0018] Preferably, each of the channels comprises:

[0019] Sensors, used to obtain external signals;

[0020] A logic unit, processing the external signal according to a preset logic to generate a signal and output the signal;

[0021] The actuator outputs a driving voltage signal to the terminal switch according to the signal generated by the logic unit.

[0022] Preferably, the monitoring circuit comprises:

[0023] Channel diagnostic circuit, used for diagnosing channel short circuit;

[0024] The response logic circuit responds according to a preset solution after the channel diagnosis circuit diagnoses that a channel failure has occurred.

[0025] Preferably, the channel diagnostic circuit includes:

[0026] Terminal switch conduction detection device, which is turned on or off synchronously with the terminal switch;

[0027] A driving voltage output detection device, wherein when the driving voltage is output, the driving voltage output detection device is turned on;

[0028] The output signal of the channel diagnosis circuit is a low-level signal only when the terminal switch conduction detection device is turned on and the drive voltage output detection device is not turned on.

[0029] Preferably, the preset scheme is:

[0030] When a short circuit fault occurs in any channel, the logic circuit should output the fault and latch it.

[0031] Preferably, the response logic circuit includes:

[0032] three response logic devices, to which the output signals of the channel diagnostic circuits of the respective channels are respectively input;

[0033] a thyristor, configured to receive an output signal of the response logic device;

[0034] Only when the output signals of all channel diagnostic circuits are at a high level, all corresponding logic devices are turned on, and the thyristor will not receive the output drive signal; as long as the output signal of any channel diagnostic circuit is at a low level, the series circuit where the corresponding logic device is located will be disconnected, the thyristor will receive the drive signal and turn on, and the fault signal of the monitoring circuit will be invalid.

[0035] Preferably, the preset scheme is:

[0036] When short-circuit faults occur in multiple channels at the same time, the output of the logic circuit should be hard shut down.

[0037] Preferably, the response logic circuit includes:

[0038] Three hard-off devices, the main circuit output end, the elevator safety circuit signal, and the elevator main control circuit signal are respectively input into the hard-off devices;

[0039] When the output end of the main circuit is energized, if any input signal of the elevator safety circuit signal or the elevator main control circuit signal is low, the series output circuit will be disconnected to blow the fuse.

[0040] The present invention also discloses a three-channel elevator brake safety control circuit, comprising:

[0041] A main circuit, comprising a fuse and three terminal switches connected in series, wherein disconnection of any terminal switch can disconnect the output of the main circuit;

[0042] Three channels, each channel is used to obtain an external safety signal and output a drive signal according to a preset logic to control the on or off of the terminal switch;

[0043] The monitoring circuit checks whether the opening and closing states of each channel are the same; if the opening and closing state of any channel is inconsistent with that of other channels, the safety circuit output is shut off and latched.

[0044] Preferably, the monitoring circuit includes 6 monitoring response devices, wherein:

[0045] The first monitoring response device, the second monitoring response device, and the third monitoring response device are synchronously turned on corresponding to the three terminal switches;

[0046] The fourth monitoring response device, the fifth monitoring response device, and the sixth monitoring response device are disconnected synchronously with the three terminal switches;

[0047] When the conduction state of any one monitoring component is inconsistent with that of other components, the monitoring circuit turns off the driving outputs of all channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings herein are intended to illustrate the general characteristics of methods, structures, and / or materials used in certain exemplary embodiments of the present invention, supplementing the descriptions in the specification. However, the drawings herein are schematic diagrams not drawn to scale and may not accurately reflect the precise structure or performance characteristics of any given embodiment. The drawings herein should not be interpreted as defining or limiting the range of values ​​or properties encompassed by the exemplary embodiments of the present invention. The present invention is further described in detail below in conjunction with the drawings and specific embodiments:

[0049] Figure 1 This is a diagram of the overall system architecture of the first embodiment of the present invention;

[0050] Figure 2 Schematic diagram of the main circuit and channels of the first embodiment of the present invention;

[0051] Figure 3 Schematic diagram of a channel diagnostic circuit according to a first embodiment of the present invention;

[0052] Figure 4 Schematic diagram of a soft shutdown circuit in a response logic circuit according to a first embodiment of the present invention;

[0053] Figure 5 Schematic diagram of a hard shutdown circuit in a response logic circuit according to a first embodiment of the present invention;

[0054] Figure 6 Schematic diagram of the main circuit and channels of the second embodiment of the present invention;

[0055] Figure 7 This is a schematic diagram of a monitoring circuit according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0056] Example 1

[0057] The goal of this invention is to implement corresponding response methods and risk assessment for the possible failure modes of each channel of the brake control circuit, as shown in the following table:

[0058] Table 1. Failure mode analysis and response of three-channel embodiment 1

[0059]

[0060]

[0061] Figure 1 The following is an implementation scheme of this embodiment. The elevator brake safety control circuit mainly includes three channels, a monitoring circuit and a trunk circuit. The following is a detailed description of the circuit:

[0062] 1. Channel

[0063] 1.1 Definition and Logic

[0064] A channel is a pathway through which safety signals flow and ultimately control the output of terminal switches. Specifically, a channel receives external safety signals (fault signals generated by the safety circuit's internal monitoring circuitry are also considered "external" safety signals and are treated similarly) and outputs corresponding terminal switch drive signals to turn on or off the terminal switches (in this case, power semiconductor devices), thereby controlling the safety circuit output. Each channel receives the same safety input signal or signals, and any channel can independently shut down the safety circuit output.

[0065] The channel consists of a sensor, logic unit, actuator, and terminal switch for obtaining external safety signals. When the external safety signal changes, the terminal switch state changes accordingly, thereby achieving control over the safety loop output.

[0066] The sensor receives the external safety signals 41DG and DLB of the elevator main circuit and the fault signal (ERROR) generated by the monitoring circuit.

[0067] 41DG: Elevator safety circuit signal, generated by the elevator safety circuit. When any safety contact is disconnected, the safety circuit is disconnected, the 41DG signal becomes invalid (i.e. power is lost), and the main circuit should have no output. When the 41DG signal is valid, the main circuit will release the brake only when other conditions are met (DLB and ERROR signals are normal).

[0068] DLB: This is the main control circuit signal, generated by the elevator's main control circuit. When the elevator needs to run, the elevator controller sends a DLB signal to control the brake. When the DLB signal is ineffective (i.e., power is lost), the main circuit should have no output. When the DLB signal is effective, the main circuit will release the brake only when other conditions are met (41DG and ERROR signals are normal).

[0069] ERROR: This is a monitoring circuit fault signal, generated by the main circuit's internal monitoring circuit. When the ERROR signal is inactive (i.e., power is lost, indicating a fault), the main circuit should have no output. When the ERROR signal is active, the main circuit will release the circuit breaker only when other conditions are met (e.g., both the 41DG and DLB signals are normal).

[0070] The logic implemented by the logic unit is: if any of the above signals fails, the channel is shut down (by shutting down the drive output of the power switch device of the channel), and then shutting down the safety circuit output, as shown in the following table:

[0071] Table 2. Three-channel embodiment. Channel 1 output logic: Y = A·B·C

[0072] A B C Y Enter 41DG Enter DLB Monitoring ERROR Drive output 1 conduction 1 conduction 1Normal 1 output driver 0 off X X 0 turns off the driver X 0 off X 0 turns off the driver X X 0 failures 0 turns off the driver

[0073] The actuator outputs a drive voltage to the control terminal of the terminal switch (i.e., the MOSFET gate) based on the signal generated by the logic unit. When the actuator outputs the drive voltage, the terminal switch will be turned on, otherwise it will be turned off.

[0074] The terminal switch is turned on or off according to the driving voltage output by the actuator.

[0075] 1.2 Implementation of the Circuit

[0076] The specific circuit design that can realize the logical functions of Table 2 is as follows:

[0077] Channel circuit (including trunk circuit) such as Figure 2 In the main circuit, due to the need for three channels, a fuse FS1 is configured, and the fuse is connected in series with the three power switching devices.

[0078] In the figure, BKPW is the positive brake power supply, and BKGND is the negative brake power supply. The power switching device is MOSFET (IGBT or similar devices are also acceptable). Each MOSFET has its own drive circuit and power supply. To simplify the core circuit, auxiliary circuits such as the drive power supply are omitted here.

[0079] Taking channel 1, where the first switch device Q1 resides, as an example, TR1 will only output the Drive1 drive signal when all three signals, 41DG, DLB, and ERROR, are high (valid) and all three optocouplers, U1-U3, are conducting. The drive design for other channels is the same as above.

[0080] 2. Monitoring circuit

[0081] The monitoring circuit consists of the following three parts:

[0082] 1) The first part is used to diagnose channel short circuit;

[0083] 2) The second part mainly describes the response logic after the channel short circuit fault is diagnosed in the first part;

[0084] 3) The third part is used to deal with scenarios where short circuit faults occur in three channels at the same time and / or drive circuit faults occur in three channels at the same time.

[0085] 2.1 Part 1

[0086] 2.1.1 Diagnostic Logic

[0087] In this solution, the monitoring function's requirement for channel short-circuit diagnosis is that if any channel is short-circuited, the output will fail and be latched. Therefore, the monitoring circuit needs to implement the "channel short-circuit" diagnostic function in advance. Its logic is shown in Table 3:

[0088] Table 3. Three-channel embodiment. Channel diagnostic logic:

[0089] A B Y <![CDATA[Drive output x > <![CDATA[Switch conduction monitoring Diag x > <![CDATA[Output diagnosis Error x > 1 output driver 1 switch is on 1Normal X 0 switch off 1Normal 0 turns off the driver 1 switch is on 0 failures

[0090] Note: The subscript "x" in the above table refers to the channel, such as channel 1, channel 2, and similarly in the following.

[0091] 2.1.2 Monitoring Circuit - Channel Diagnosis Circuit

[0092] The specific circuit design that can realize the logical functions in Table 3 is as follows Figure 3 As shown in Figure 1, the diagnostic circuit needs to detect whether the switch device has a dangerous failure, that is, whether the conduction state is inconsistent with the expected state. Figure 3 Taking the first switch device as an example, its working principle is explained as follows:

[0093] (1) Optocoupler U4, the terminal switch conduction detection device, is used to detect whether the switch device is conducting:

[0094] When the device is turned on, the potential of D1 is basically the same as the potential of S1, except for the internal resistance R DSONTherefore, when the device is turned on, the U4 optocoupler is also turned on, and vice versa.

[0095] (2) Optocoupler U5, which is a driving voltage output detection device, is used to detect whether the device drives the output:

[0096] When the drive output is on, the drive voltage signal Drive1 has a signal potential that is equal to the drive power supply V g1 Basically the same, the optocoupler U5 is turned on at the same time, and vice versa.

[0097] (3) Only when U4 is conducting (device is on) and U5 is not conducting (device gate is not driven), the output signal Error1 of the channel diagnosis circuit will output a low-level signal, indicating a fault. Otherwise, Error1 outputs a high-level signal, indicating that the device is diagnosed as normal.

[0098] 2.2 Part 2

[0099] 2.2.1. Monitoring Fault Logic

[0100] This section mainly discusses how the safety circuit should adopt what logic to generate a shutdown signal for turning off the terminal switch to ensure system safety after a short circuit fault is diagnosed in the channel in the first section.

[0101] The logic that needs to be implemented in this part is: if any channel is short-circuited, the fault is output and latched. This part uses the fault diagnosis signal (Error x ) as an input signal and outputs a shutdown signal for turning off the terminal switch. Here, the output shutdown signal is referred to as a soft shutdown signal. The specific logic is shown in Table 4.

[0102] Table 4. Soft shutdown output logic for three-channel embodiment 1: Y = A·B·C

[0103]

[0104] 2.2.2 Monitoring circuit - soft shutdown circuit

[0105] The specific circuit design that can realize the logic function of Table 4 is shown in Figure 4. The function that this circuit needs to realize is: when any channel diagnoses a dangerous failure, it will immediately shut down the drive output and latch the fault. Figure 4 shown.

[0106] The circuit includes multiple coping logic devices, Figure 4 In the figure, U6 is the first corresponding logic device, U7 is the second corresponding logic device, and U8 is the third corresponding logic device. In this embodiment, the first corresponding logic device, the second corresponding logic device, and the third corresponding logic device are all optocouplers, but they can also be other devices.

[0107] Only when the three diagnostic signals Error1-Error3 are all high (channel is normal), the three optocouplers are all turned on and SCR1 will not receive the driving signal; on the contrary, as long as any diagnostic signal Error x When the voltage is low (channel short-circuited), the series circuit where the optocoupler output is located will be disconnected, and thyristor SCR1 will receive the drive signal. After SCR1 turns on, it will continuously pull the ERROR signal low (making the ERROR signal invalid and shutting off the drive output of all channels). Due to the characteristics of thyristor devices, they will only return to the off state after power is turned off and restarted. Otherwise, they will continue to output the fault signal, thus realizing the fault latch function.

[0108] 2.3 Part III

[0109] 2.3.1 Diagnostic Logic

[0110] If a short circuit occurs in all three channels, the terminal switch cannot be turned off even if the drive output is turned off; or when the drive circuit of the three channels fails and the drive signal is incorrectly given, the safety circuit output cannot be cut off even if the switch device is not short-circuited.

[0111] To address this particular scenario, the brake safety control circuit of this invention incorporates a self-destruct function. This function shuts down the output by blowing a fuse (a circuit breaker is also possible, but this article uses a fuse as an example). This method can be considered a hard shutdown. Because a blown fuse requires on-site replacement, this function is only triggered in the most extreme circumstances.

[0112] The logic of hard shutdown is as follows:

[0113] a) The fault output of the soft shutdown function cannot trigger this function. For example, if only one or two channels are short-circuited, it will only lock the drive output and will not blow the fuse;

[0114] b) Executed only when the final output RLB signal is inconsistent with the safety input signal 41DG / DLB.

[0115] Table 5. Hard shutdown logic:

[0116] A B C Y Enter 41DG Enter DLB Output RLB Fuse blown 1Normal 1Normal 1 conduction 0 No melting 0 exceptions X 1 conduction 1 fuse X 0 exceptions 1 conduction 1 fuse X X 0 failures 0 No melting

[0117] 2.3.2 Monitoring Circuit - Hard Shutdown Circuit

[0118] The specific circuit design that can realize the logical functions in Table 5 is as follows Figure 5 As shown, when the main circuit output signal RLB is inconsistent with the elevator safety circuit signal 41DG and the elevator main control circuit signal DLB, the hard shutdown circuit is responsible for burning the fuse to deal with the extreme situation of all three channels being short-circuited or all being falsely connected.

[0119] Figure 5 When the main circuit output terminal RLB is energized, the first hard-off device U 41 At this time, if any input signal of 41DG or DLB is low, the second hard-off device U 42 and the third hard-off device U 43 The series output circuit will be disconnected, and SCR2 will be connected to the power supply by BKPW through U 41 The output terminal is driven. Resistor R1 needs to be configured as a power resistor to blow the fuse.

[0120] 3. Main circuit

[0121] like Figure 2 As shown, the main circuit of this embodiment is composed of a fuse 1 and three power switch devices Q1, Q2, and Q3 connected in series in sequence. If any one of them is disconnected, the brake output can be disconnected.

[0122] Example 2

[0123] The goal of this embodiment is the same as that of embodiment 1, and its system structure is as follows: Figure 6 As shown, the embodiment 1 also includes three channels, a monitoring circuit and a trunk circuit. Only the differences from the embodiment 1 are described below.

[0124] In this embodiment, the functions of the monitoring circuit include:

[0125] 1) The monitoring circuit checks whether the opening and closing states of each channel are the same;

[0126] 2) When an abnormality occurs, the safety circuit output is shut down and latched: the shutdown mode is divided into soft shutdown and hard shutdown;

[0127] a) Soft shutdown: When the opening and closing states of the three channels are inconsistent, a fault signal is output, the drive output is shut down, and the switch device is disconnected;

[0128] b) Hard shutdown: When the brake output terminal is inconsistent with the safety input signal, the fuse will burn out to deal with the extreme situation of all three channels being short-circuited or all being falsely connected.

[0129] The system structure of Example 1 ( Figure 1 )compared to, Figure 6 The system diagram shown does not require diagnosis of each channel, but only requires monitoring and comparing the opening and closing states of each channel. Therefore, its implementation is slightly simpler than the system structure of Example 1.

[0130] Table 6 shows the possible failure modes, response methods and risk assessment for each channel.

[0131] Table 6. Failure mode analysis and solutions for three-channel embodiment 2

[0132] Failure Mode Monitoring output Coping methods Risk Assessment Three channels are normally conductive normal - Safety Three channels normally shut down normal - Safety If any channel is open circuit, the others are connected. Fault Locking drive Safety If any two channels are open circuit, the rest are connected. Fault Locking drive Safety Three-channel open circuit fault normal - Safety If any channel is short-circuited, the others will be disconnected. Fault Locking drive Safety If any two channels are short-circuited, the rest will be disconnected. Fault Locking drive Safety All three channels are short-circuited or incorrectly turned on Fault Burnt fuse Safety

[0133] In this embodiment, the logic of the second part of the monitoring circuit, the soft shutdown part, is: if the opening and closing state of any channel is inconsistent with that of other channels, a fault is output and latched, as shown in Table 7 for details.

[0134] Table 7. Soft shutdown output logic for three-channel embodiment 2:

[0135]

[0136]

[0137] Accordingly, the hardware circuit design of the second part is as follows Figure 7 As shown, its working principle is as follows:

[0138] The monitoring circuit includes a first monitoring response device U 21 , the second monitoring response device U 22 , the third monitoring response device U 23 , and the fourth monitoring response device U 31 , Fifth monitoring response device U 32 , Sixth monitoring response device U 33 In this embodiment, the above-mentioned monitoring response devices are all optocouplers. Of course, other devices can also be selected.

[0139] When all three MOSFETs Q1-Q3 are turned on, the drain D and source S potentials of each device are almost the same, so the optocoupler U 21 ~U 23 All are turned on, and the base of TR2 is connected to U 21 ~U 23 The output current is turned on, SCR1 is turned off, and ERROR outputs a high level (normal);

[0140] When all three MOSFETs Q1-Q3 are turned off, the drain D and source S of each device are disconnected, so the optocoupler U 31 ~U 33 All are turned off, and the base of TR2 is connected to U 31 ~U 33 The output circuit is turned on, SCR1 is turned off, and ERROR outputs a high level (normal).

[0141] If the conduction state of any device is inconsistent with that of the other devices, TR2 will not conduct. At this time, SCR1 will receive the drive signal. After SCR1 conducts, it will continuously pull the ERROR signal low (turning off the drive output of all channels). This realizes the fault latch function.

[0142] The present invention has been described in detail above by way of specific embodiments and examples, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered within the scope of protection of the present invention.

Claims

1. A three-channel elevator brake safety control circuit, characterized in that: include: A main circuit, comprising a fuse and three terminal switches connected in series, wherein disconnection of any terminal switch can disconnect the output of the main circuit; Three channels, each channel is used to obtain an external safety signal and output a drive signal according to a preset logic to control the on or off of the terminal switch; Monitoring circuit, used to diagnose the short circuit status of each channel and respond according to the preset plan; The external safety signal includes an elevator safety circuit signal, an elevator main control circuit signal and a monitoring circuit fault signal; When any of the above signals fails, the main circuit has no output; When any of the above signals is valid, the main circuit will have an output only when the other two signals are valid; Each of the channels comprises: Sensors, used to obtain external signals; A logic unit, processing the external signal according to a preset logic to generate a signal and output the signal; an actuator, outputting a driving voltage signal to the terminal switch according to the signal generated by the logic unit; The monitoring circuit includes: Channel diagnostic circuit, used for diagnosing channel short circuit; The response logic circuit responds according to a preset solution after the channel diagnosis circuit diagnoses that a channel failure has occurred.

2. The three-channel elevator brake safety control circuit according to claim 1, characterized in that: Channel diagnostic circuitry includes: Terminal switch conduction detection device, which is turned on or off synchronously with the terminal switch; A driving voltage output detection device, wherein when the driving voltage is output, the driving voltage output detection device is turned on; The output signal of the channel diagnosis circuit is a low-level signal only when the terminal switch conduction detection device is turned on and the drive voltage output detection device is not turned on.

3. The three-channel elevator brake safety control circuit according to claim 1, characterized in that: The preset scheme is: When a short circuit fault occurs in any channel, the logic circuit should output the fault and latch it.

4. The three-channel elevator brake safety control circuit according to claim 3, characterized in that: The response logic circuit includes: three response logic devices, to which the output signals of the channel diagnostic circuits of the respective channels are respectively input; a thyristor, configured to receive an output signal of the response logic device; Only when the output signals of all channel diagnostic circuits are at a high level, all corresponding logic devices are turned on, and the thyristor will not receive the output drive signal; as long as the output signal of any channel diagnostic circuit is at a low level, the series circuit where the corresponding logic device is located will be disconnected, the thyristor will receive the drive signal and turn on, and the fault signal of the monitoring circuit will be invalid.

5. The three-channel elevator brake safety control circuit according to claim 1, characterized in that: The preset scheme is: When short-circuit faults occur in multiple channels at the same time, the output of the logic circuit should be hard shut down.

6. The three-channel elevator brake safety control circuit according to claim 5, characterized in that: The response logic circuit includes: Three hard-off devices, the main circuit output end, the elevator safety circuit signal, and the elevator main control circuit signal are respectively input into the hard-off devices; When the output end of the main circuit is energized, if any input signal of the elevator safety circuit signal or the elevator main control circuit signal is low, the series output circuit will be disconnected to blow the fuse.

7. A three-channel elevator brake safety control circuit, characterized in that: include: A main circuit, comprising a fuse and three terminal switches connected in series, wherein disconnection of any terminal switch can disconnect the output of the main circuit; Three channels, each channel is used to obtain an external safety signal and output a drive signal according to a preset logic to control the on or off of the terminal switch; The monitoring circuit checks whether the opening and closing states of each channel are the same; if the opening and closing state of any channel is inconsistent with that of other channels, the safety circuit output is shut off and latched.

8. The three-channel elevator brake safety control circuit according to claim 7, characterized in that: The monitoring circuit includes 6 monitoring response devices, including: The first monitoring response device, the second monitoring response device, and the third monitoring response device are synchronously turned on corresponding to the three terminal switches; The fourth monitoring response device, the fifth monitoring response device, and the sixth monitoring response device are disconnected synchronously with the three terminal switches; When the conduction state of any one monitoring component is inconsistent with that of other components, the monitoring circuit turns off the driving outputs of all channels.

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