Magnetic lock

Abstract

The utility model discloses a magnetic lock. The magnetic lock comprises an electromagnet installed on the door frame, an iron plate fixed to the door plate, a pull plug penetrating and inserted into the iron plate in the thickness direction, a permanent magnet arranged at the tail end of the pull plug and a circuit control board connected with the electromagnet. The circuit control board comprises a transistor, a pickup circuit, a first preprocessing circuit, a comparator and a set voltage input circuit. According to the magnetic lock, the current fluctuation in the electromagnet is detected through the circuit control board, whether a door pushing event occurs or not when the magnetic lock is in a locking state can be detected, and the magnetic lock structure is not prone to being affected by external force friction, humidity, temperature and other environmental factors and is high in stability; and the device is simple in structure, low in cost, fast in response, low in noise and suitable for large-scale application and implementation.

Description

Technical Field

[0001] The utility model relates to the technical field of electromagnetic devices, in particular to a magnetic lock. Background Art

[0002] Magnetic locks (also known as electromagnetic locks) use the principle of electromagnetism. When current passes through silicon steel sheets, the electromagnetic lock will generate a strong suction force to tightly absorb objects made of ferromagnetic materials, thereby achieving the effect of locking the door. Magnetic locks are widely used for their advantages such as no complex mechanical structure and low cost.

[0003] In order to ensure user safety, some magnetic locks provide an early warning function. When the magnetic lock detects actions such as pushing the door in the locked state, it can generate an early warning (EARLY WARNNING, referred to as EW) signal.

[0004] However, the prior art uses a micro-motion mechanism to detect the door-pushing action and then generate an early warning signal. However, this structure is easily affected by external friction, humidity, temperature, etc., and has poor stability. Utility Model Content

[0005] In view of the above problems, embodiments of the present utility model are proposed to provide a magnetic lock that overcomes the above problems or at least partially solves the above problems.

[0006] According to one aspect of the embodiment of the utility model, a magnetic lock is provided, comprising: an electromagnet mounted on a door frame, an iron plate fixed to a door panel, a pull bolt inserted through the iron plate in a thickness direction, a permanent magnet disposed at the rear end of the pull bolt, and a circuit control board connected to the electromagnet;

[0007] Wherein, the circuit control board includes: a transistor, a pickup circuit, a first pre-processing circuit, a comparator, and a set voltage input circuit;

[0008] The first end of the electromagnet is connected to the power supply voltage, and the second end of the electromagnet is connected to the drain of the transistor;

[0009] The gate of the transistor is input with a bias signal, and the source of the transistor is connected to the input terminal of the pickup circuit;

[0010] The output end of the pickup circuit is connected to the input end of the first preprocessing circuit, and the pickup circuit is used to pick up the current fluctuation signal of the electromagnet;

[0011] The output terminal of the first preprocessing circuit is connected to the first input terminal of the comparator, and is used to preprocess the current fluctuation signal;

[0012] The output end of the setting voltage input circuit is connected to the second input end of the comparator, and is used to input a setting voltage signal to the second input end of the comparator;

[0013] The comparator compares the voltage magnitudes of the current fluctuation signal at the first input terminal and the set voltage signal at the second input terminal, and outputs a detection signal according to the voltage magnitudes.

[0014] In an optional implementation, if the voltage of the current fluctuation signal is higher than the voltage of the set voltage signal, the comparator outputs a low level; if the voltage of the current fluctuation signal is lower than or equal to the voltage of the set voltage signal, the comparator outputs a high level.

[0015] In an optional embodiment, the pickup circuit includes a capacitor C2 and a resistor R9;

[0016] A first end of the capacitor C2 is connected to the source of the transistor, a second end of the capacitor C2 is connected to a first end of the resistor R9 and an input end of the first preprocessing circuit; and a second end of the resistor R9 is grounded.

[0017] In an optional implementation, the first preprocessing circuit includes: a first filtering circuit and a first amplifying circuit;

[0018] The input end of the first filter circuit is connected to the output end of the pickup circuit; the output end of the first filter circuit is connected to the input end of the first amplifier circuit, and the first filter circuit is used to filter the baseband signal;

[0019] The output end of the first amplifier circuit is connected to the first input end of the comparator, and the first amplifier circuit is used to amplify the current fluctuation signal.

[0020] In an optional implementation, the first filter circuit includes: an RC filter circuit consisting of a resistor R5, a resistor R6, a capacitor C4 and a capacitor C5;

[0021] The first amplifier circuit includes: an amplifier U3, a resistor R2, and a common-phase amplifier circuit formed by a resistor R3.

[0022] In an optional embodiment, the magnetic lock further includes: a single chip microcomputer;

[0023] The first input terminal of the single-chip microcomputer is connected to the output terminal of the comparator, and the output terminal of the single-chip microcomputer is connected to the gate of the transistor. The single-chip microcomputer is used to determine the target operating voltage or target operating current of the electromagnet according to the detection signal transmitted by the comparator, and transmit a PWM signal to the gate of the transistor based on the target operating voltage or target operating current.

[0024] In an optional embodiment, the magnetic lock further includes: a second preprocessing circuit;

[0025] The input end of the second preprocessing circuit is connected to the source of the transistor, the output end of the second preprocessing circuit is connected to the second input end of the single chip computer, and the second preprocessing circuit is used to preprocess the working current signal of the electromagnet;

[0026] The single chip microcomputer is also used to obtain the electromagnet working current and the electromagnet working voltage according to the working current signal, and perform PID control according to the electromagnet working current and the electromagnet working voltage so that the electromagnet working current is maintained at the target working current or the electromagnet working voltage is maintained at the target working voltage.

[0027] In an optional implementation, the second preprocessing circuit includes: a second filtering circuit, a second amplifying circuit, and a decoupling circuit;

[0028] Among them, the input end of the second filter circuit is connected to the source of the transistor, the output end of the second filter circuit is connected to the input end of the second amplifier circuit, and the second filter circuit is used to filter the baseband signal; the output end of the second amplifier circuit is connected to the input end of the decoupling circuit, and the second amplifier circuit is used to amplify the working current signal; the output end of the decoupling circuit is connected to the second input end of the microcontroller, and the decoupling circuit is used to decouple the working current signal.

[0029] In an optional implementation, the second filtering circuit includes: a Π-type filtering circuit consisting of a resistor R14, a resistor R15, a capacitor C9, and a capacitor C10.

[0030] In an optional implementation, the second amplifier circuit includes: a common-mode amplifier circuit composed of an amplifier U4, a resistor R13, and a resistor R16.

[0031] According to the magnetic lock provided by the embodiment of the utility model, by detecting the current fluctuation in the electromagnet through the circuit control board, it is possible to detect whether a door pushing event occurs when the magnetic lock is in the locked state. In addition, the magnetic lock structure provided by the utility model is not easily affected by environmental factors such as external friction, humidity, temperature, etc., and has high stability. In addition, it has a simple structure, low cost, fast response, and low noise, and is suitable for large-scale application and implementation.

[0032] The above description is only an overview of the technical solution of the embodiment of the utility model. In order to more clearly understand the technical means of the embodiment of the utility model, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the utility model more obvious and easy to understand, the specific implementation method of the embodiment of the utility model is listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only used for the purpose of illustrating the preferred embodiments and are not to be considered as limitations of the embodiments of the present utility model. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 A schematic diagram of the structure of an electromagnetic lock provided by an embodiment of the utility model is shown;

[0035] Figure 2 A circuit diagram of a circuit control board provided by an embodiment of the utility model is shown;

[0036] Figure 3 A circuit diagram of another circuit control board provided by an embodiment of the utility model is shown;

[0037] Figure 4 A circuit diagram of another circuit control board provided by an embodiment of the utility model is shown;

[0038] Figure 5 A circuit diagram of another circuit control board provided in an embodiment of the utility model is shown. DETAILED DESCRIPTION

[0039] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0040] Figure 1 FIG. 1 shows a schematic diagram of the structure of an electromagnetic lock provided by an embodiment of the utility model. Figure 1 As shown, the magnetic lock includes: an electromagnet 110 , an iron plate 120 , a pull bolt 130 , a permanent magnet 140 and a circuit control board 150 .

[0041] The electromagnet 110 is installed on the door frame, the iron plate 120 is installed on the door panel, the bolt 130 penetrates the iron plate 120 along the thickness direction of the iron plate 120, the tail end of the bolt 130 is close to the suction surface of the iron plate and the electromagnet, and the head end of the bolt 130 is exposed on the other side of the iron plate. The tail end of the bolt 130 is provided with a permanent magnet 140, and the electromagnet 110 is locked when the iron plate is sucked, and the permanent magnet 140 can be on the suction surface. And the circuit control board 150 is connected to the electromagnet 110.

[0042] When the electromagnet 110 and the iron plate 120 are in the state of being attracted, if the door panel is pushed by an external force, the pull bolt will be displaced, and the permanent magnet will be displaced accordingly, and then the magnetic field of the electromagnet coil will change, causing the current in the electromagnet coil to fluctuate due to the magneto-electric coupling effect. The circuit control board 150 determines whether the current door panel is pushed by an external force by detecting the current fluctuation signal in the electromagnet 110, and then generates an EW signal.

[0043] Specifically, Figure 2The circuit diagram of the circuit control board shown is as follows: the circuit control board 150 includes: a transistor Q1, a pickup circuit 151, a first preprocessing circuit 152, a comparator U2, and a set voltage input circuit 153.

[0044] The transistor Q1 includes a source, a drain and a gate, and MTD3055 can be selected. The first end of the electromagnet 110 is connected to the power supply voltage VCC, and the second end of the electromagnet 110 is connected to the drain of the transistor Q1. The gate of the transistor Q1 inputs a bias signal, and the bias signal (such as a PWM signal) can be used to adjust the working current in the electromagnet 110. The source of the transistor Q1 is connected to the input end of the pickup circuit 151.

[0045] The input end of the pickup circuit 151 is connected to the source of the transistor Q1, and the current path is the first end of the electromagnet 110 → the second end of the electromagnet 110 → the drain of the transistor Q1 → the source of the transistor Q1, and then flows to the ground through the resistor or directly, so that the pickup circuit 151 is connected to the source of the transistor Q1, and can pick up the current fluctuation signal flowing through the electromagnet 110. In addition, the output end of the pickup circuit 151 is connected to the first pre-processing circuit 152, and the picked-up current fluctuation signal is transmitted to the first pre-processing circuit 152.

[0046] The input end of the first preprocessing circuit 152 is connected to the output end of the pickup current 151, so as to receive the current fluctuation signal picked up by the pickup current 151. The first preprocessing circuit 152 performs preprocessing on the current fluctuation signal, such as filtering, amplification, etc. The output end of the first preprocessing circuit 152 is connected to the first input end of the comparator U2, and the first preprocessing circuit 152 can transmit the preprocessed current fluctuation signal to the comparator U2.

[0047] The output end of the setting voltage input circuit 153 is connected to the second input end of the comparator U2, and is used to input a setting voltage signal to the second input end of the comparator U2. For example, the setting voltage may be 0.5V.

[0048] The comparator U2 compares the voltage of the current fluctuation signal at the first input end and the voltage of the set voltage signal at the second input end, and outputs a detection signal according to the voltage, and the detection signal can indicate whether there is a push door at present. Among them, the comparator U2 can use LM358A-SR. Specifically, if the voltage of the current fluctuation signal is higher than the voltage of the set voltage signal, indicating that there is a certain fluctuation in the current of the electromagnet, the comparator outputs a low level, indicating that there is a push door or a pull door event at present; if the voltage of the current fluctuation signal is lower than or equal to the voltage of the set voltage signal, indicating that the current fluctuation of the electromagnet is small or does not fluctuate, the comparator outputs a high level, indicating that there is no push door or a pull door event at present. Therefore, the level of the comparator output can be used to determine whether there is a push door at present, and then generate an early warning signal.

[0049] It can be seen that the magnetic lock provided in this embodiment detects the current fluctuation in the electromagnet through the circuit control board, and can detect whether a door pushing or door pulling event occurs in the locked state. The structure is not easily affected by external friction, humidity, temperature, etc., and has high stability; and it has the characteristics of simple structure, low cost, fast response, low noise, etc., and is suitable for large-scale application and implementation.

[0050] In an optional implementation, the pickup circuit 151 specifically includes a capacitor C2 and a resistor R9. Figure 3 As shown, the first end of capacitor C2 is connected to the source S of transistor Q1, and the second end of capacitor C2 is connected to the first end of resistor R9 and the input end of the first preprocessing circuit 152; the second end of resistor R9 is grounded. That is, the first end of capacitor C2 is the input end of the pickup circuit, and the second end of capacitor C2 is the output end of the pickup circuit. Among them, due to the isolation of DC and AC characteristics of the capacitor, the pickup circuit will not pick up the DC working signal of the electromagnet, so that the pickup circuit picks up the current fluctuation signal caused by the current fluctuation of the electromagnet coil due to the magnetic field fluctuation. Among them, capacitor C2 can be selected from 1uf / 25V, and resistor R9 can be selected from 510KΩ.

[0051] In addition, the source electrode S of the transistor Q1 is also connected to the first end of the resistor R8, and the second end of the resistor R8 is grounded, so as to facilitate current sampling. For example, the current path is the first end of the electromagnet 110 → the second end of the electromagnet 110 → the drain electrode D of the transistor Q1 → the source electrode S of the transistor Q1 → the resistor R8 → the ground, and the current flowing through the resistor is sampled through the resistor R8 (the resistance value can be 0.1Ω), and the current calculated per MV represents 10ma.

[0052] In an optional embodiment, the first preprocessing circuit 152 includes: a first filtering circuit and a first amplifying circuit. The input end of the first filtering circuit is connected to the output end of the pickup circuit 151; the output end of the first filtering circuit is connected to the input end of the first amplifying circuit, and the output end of the first amplifying circuit is connected to the first input end of the comparator U2. Since the gate of the transistor Q1 inputs a bias signal, the current fluctuation signal picked up by the pickup circuit 151 is superimposed with the current fluctuation signal and the baseband signal (PWM signal) in the electromagnet coil, and the baseband signal can be filtered by the first filtering circuit. The first amplifying circuit amplifies the filtered current fluctuation signal for subsequent signal processing.

[0053] Further optional, such as Figure 3As shown, the first filter circuit includes: an RC filter circuit composed of a resistor R5, a resistor R6, a capacitor C4 and a capacitor C5. In the utility model, the baseband signal is a high-frequency signal of 12KHZ, so the filter circuit is specifically a high-frequency filter circuit. The values ​​of the resistor R5 and the resistor R6 can be 15KΩ, and the capacitor C4 and the capacitor C5 can be selected from 103pf / 25V. Among them, the cut-off frequency = 1 / (2*π*R*C), R represents the resistance value, and C represents the capacitance value, that is, the cut-off frequency is inversely proportional to the product of the capacitance and the resistance, that is, the value of the resistor or capacitor increases, and the cut-off frequency decreases; conversely, the value of the resistor or capacitor decreases, and the cut-off frequency increases. Specifically, the first end of the resistor R5 is connected to the second end of the capacitor C2, and the second end of the resistor R5 is connected to the first end of the capacitor C4 and the first end of the resistor R6; the second end of the resistor R6 is connected to the first end of the capacitor C5, and the second ends of the capacitor C4 and the capacitor C5 are grounded. The first amplifier circuit also includes a resistor R10, whose value can be 220KΩ; the first end of the resistor R10 is connected to the second end of the resistor R6, and the second end of the resistor R10 is grounded. Then the first end of the resistor R5 is the input end of the first filter circuit, and the first end of the capacitor C5 is the output end of the first filter circuit.

[0054] Further optional, such as Figure 3 As shown, the first amplifier circuit includes: an amplifier U3, a resistor R2 and a common-phase amplifier circuit composed of a resistor R3. Among them, the output end of the first filter circuit is connected to the positive input end of the amplifier U3, the second end of the resistor R2 and the first end of the resistor R3 are connected to the negative input end of the amplifier U3, the first end of the resistor R2 is grounded, the second end of the resistor R3 is connected to the output end of the amplifier U3, and the output end of the amplifier U3 is connected to the first input end (negative input end) of the comparator U2. The amplification factor of the first amplifier circuit is 1+R3 / R2. Among them, the values ​​of the resistor R2 and the resistor R3 can be 0.51KΩ and 110KΩ respectively, and the amplifier U3 can select LM358A-SR.

[0055] In an optional implementation, the setting voltage input circuit 153 includes a resistor R7, a resistor R11 and a capacitor C6. Figure 3 As shown, the first end of resistor R7 is connected to the first end of capacitor C6, the second end of resistor R7 is connected to VDD, the second end of capacitor C6 is grounded, and resistor R11 is connected in parallel with capacitor C6. Thus, a set voltage signal is provided to the second input end (positive input end) of comparator U2. Set voltage = VDD*(R11 / (R7+R11)), the resistance values ​​of resistor R7 and resistor R11 can be 150KΩ and 27KΩ respectively, and capacitor C6 can be selected from 104pf / 25V.

[0056] In addition, if Figure 3As shown, a resistor R1 is connected between the output terminal of the comparator U2 and VDD, and a capacitor C1 is connected between VDD and ground. R1 and C1 can be selected as 100KΩ and 104pf / 25V respectively.

[0057] In an optional embodiment, if Figure 4 As shown, the magnetic lock also includes a single-chip microcomputer U1. The single-chip microcomputer U1 can be STC8G1K08-08, which includes pins 1-8, of which pin 1 is P5.4 (RST), pin 2 is VCC (AVCC / VREF+), pin 3 is P5.5, pin 4 is GND (AGND / VREF-), pin 5 is P3.0 (ADC8 / RXD), pin 6 is P3.1 (ADC9 / TXD), pin 7 is P3.2 (ADC10 / INT0), and pin 8 is P3.3 (ADC11 / INT1). The first input terminal of the single-chip microcomputer U1 is connected to the output terminal of the comparator, and the output terminal of the single-chip microcomputer U1 is connected to the gate of the transistor Q1. The single-chip microcomputer U1 is used to determine the target operating voltage or target operating current of the electromagnet according to the detection signal transmitted by the comparator, and transmit a PWM signal to the gate of the transistor based on the target operating voltage or target operating current to control the transistor operating current. For example, when the microcontroller U1 detects that the comparator outputs a low level, it determines a higher target operating voltage or target operating current to increase the operating current of the transistor Q1 and enhance the attraction force; when the comparator outputs a high level, it determines a lower target operating voltage or target operating current to reduce the operating current of the transistor Q1 and achieve energy saving.

[0058] In an optional embodiment, if Figure 4 As shown, the magnetic lock also includes a second preprocessing circuit 154; the input end of the second preprocessing circuit 154 is connected to the source of the transistor Q1, and the output end of the second preprocessing circuit 154 is connected to the second input end of the single-chip computer U1, and the second preprocessing circuit 154 is used to preprocess the working current signal of the electromagnet. The single-chip computer U1 is also used to obtain the working current of the electromagnet and the working voltage of the electromagnet according to the working current signal, and perform PID control according to the working current of the electromagnet and the working voltage of the electromagnet so that the working current of the electromagnet is maintained at the target working current or the working voltage of the electromagnet is maintained at the target working voltage.

[0059] Further optionally, the second preprocessing circuit includes: a second filtering circuit, a second amplifying circuit, and a decoupling circuit. The second filtering circuit input end is connected to the transistor source, the second filtering circuit output end is connected to the second amplifying circuit input end, and the second filtering circuit is used to filter the baseband signal; the second amplifying circuit output end is connected to the decoupling circuit input end, and the second amplifying circuit is used to amplify the working current signal; the decoupling circuit output end is connected to the second input end of the single-chip microcomputer, and the decoupling circuit is used to decouple the working current signal.

[0060] Specifically, Figure 5 As shown, the second filter circuit includes a Π-type filter circuit composed of a resistor R14, a resistor R15, a capacitor C9, and a capacitor C10. Wherein, the first end of the resistor R14 is connected to the first end of the capacitor C9, and the connection point is used as the output end of the second filter circuit; the first end of the resistor R15 is connected to the first end of the capacitor C10, and the second end of the resistor R15 is connected to the source of the transistor Q1, and the second end of the resistor R15 is used as the input end of the second filter circuit. The second ends of the capacitor C9 and the capacitor C10 are both grounded. Thus, the resistor R14, the resistor R15, the capacitor C9, and the capacitor C10 constitute a Π-type filter circuit, thereby filtering out the baseband signal. Wherein, the resistor R14 and the resistor R15 can be selected from 15kΩ, and the capacitor C9 and the capacitor C10 can be selected from 103pF / 25V.

[0061] In an optional embodiment, if Figure 5 As shown, the second amplifier circuit includes: an in-phase amplifier circuit composed of an amplifier U4, a resistor R13, and a resistor R16. Among them, the negative input end of the amplifier U4 is connected to the output end of the second filter circuit, the positive input end of the amplifier U4 is connected to the second end of the resistor R13 and the first end of the resistor R16, the second end of the resistor R16 is grounded, and the first end of the resistor R13 is connected to the output end of the amplifier U4. Then the negative input end of the amplifier U4 is the input end of the second amplifier circuit, and the output end of the amplifier U4 is the output end of the second amplifier circuit. Among them, the amplification factor of the second amplifier circuit is: (R13 / R16)+1), the resistor R13 can be selected from 91KΩ, the resistor R16 can be selected from 10KΩ, and the amplifier U4 can be selected from LMV321B.

[0062] In an optional embodiment, if Figure 5 As shown, the decoupling circuit includes: a resistor R12 and a capacitor C7. The first end of the resistor R12 is connected to the first end of the capacitor C7, and the connection point serves as the output end of the decoupling circuit; the second end of the resistor R12 is connected to the output end of the second amplifier circuit, that is, the first end of the resistor R12 is the input end of the decoupling circuit. The output end of the decoupling circuit is connected to the second output end of the single-chip microcomputer U1 ( Figure 5 The 5th pin of U1 and the 6th pin of U1 are the first input terminal of the microcontroller, and the 6th pin is connected to U2_OUT, i.e., the comparator output terminal signal). Among them, the values ​​of the resistor R12 and the capacitor C7 can be 4.7kΩ and 104pF / 25V.

[0063] In an optional embodiment, the control circuit board 150 also includes: a resistor R18, a resistor R17, a capacitor C11, and a capacitor C3. Among them, R17 can be selected from 1KΩ, R18 can be selected from 9.1KΩ, and C11 and C3 can be selected from 104pF / 25V. Among them, the first end of the resistor R17 is grounded, the second end of the resistor R17 is connected to the first end of the resistor R18, and the second end of the resistor R18 is connected to the voltage VCC, which is the working voltage of the electromagnet. And the second end of the resistor R17 and the first end of the resistor R18 are connected to the third input terminal ( Figure 5 The 1st pin of U1 shown in the figure) is connected to the MCU U1 to input a voltage signal. The MCU U1 processes the voltage signal at the third input terminal to obtain the electromagnet working voltage, that is, Vout=VCC*(R17 / (R17+R18)), where Vout is the voltage value of the third input terminal and VCC is the electromagnet working voltage. In addition, the 2nd pin of the MCU U1 is grounded through the capacitor C3. Moreover, the 2nd pin of the MCU U1 is the output terminal, which is connected to the gate of the transistor Q1 through the resistor R8 (which can be 330Ω).

[0064] It should be noted that, in the present invention, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not represent any actual relationship or order between the entities or operations.

[0065] The illustrations provided by the present invention are only schematic illustrations of the basic concept of the present invention. The illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0066] The "connection" in the present invention includes both direct connection and indirect connection, such as connection through some active devices, passive devices or electrically conductive media; it may also include connection through other active devices or passive devices on the basis of achieving the same or similar functional purposes as is well known to those skilled in the art, such as connection through circuits or components such as switches and follower circuits.

[0067] The description and application of the utility model here are illustrative, and it is not intended to limit the scope of the utility model to the above-mentioned embodiments. The effects or advantages involved in the embodiments may not be embodied in the embodiments due to interference from various factors, and the description of the effects or advantages is not used to limit the embodiments. The deformation and changes of the embodiments disclosed here are possible, and the replacement of the embodiments and the various equivalent components are well known to those of ordinary skill in the art. It should be clear to those skilled in the art that the utility model can be implemented in other forms, structures, arrangements, proportions, and with other components, materials and parts without departing from the spirit or essential features of the utility model. Other deformations and changes can be made to the embodiments disclosed here without departing from the scope and spirit of the utility model.

Claims

1. A magnetic lock, characterized in that: include: An electromagnet installed on the door frame, an iron plate fixed to the door panel, a pull bolt inserted through the iron plate in the thickness direction, a permanent magnet arranged at the tail end of the pull bolt, and a circuit control board connected to the electromagnet; Wherein, the circuit control board includes: a transistor, a pickup circuit, a first pre-processing circuit, a comparator, and a setting voltage input circuit; A first end of the electromagnet is connected to a power supply voltage, and a second end of the electromagnet is connected to a drain of the transistor; The gate of the transistor is input with a bias signal, and the source of the transistor is connected to the input terminal of the pickup circuit; The output end of the pickup circuit is connected to the input end of the first preprocessing circuit, and the pickup circuit is used to pick up the current fluctuation signal of the electromagnet; The output terminal of the first preprocessing circuit is connected to the first input terminal of the comparator, and is used to preprocess the current fluctuation signal; The output end of the setting voltage input circuit is connected to the second input end of the comparator, and is used to input a setting voltage signal to the second input end of the comparator; The comparator compares the voltage magnitudes of the current fluctuation signal at the first input terminal and the set voltage signal at the second input terminal, and outputs a detection signal according to the voltage magnitudes.

2. The magnetic lock according to claim 1, characterized in that: If the voltage of the current fluctuation signal is higher than the voltage of the set voltage signal, the comparator outputs a low level; if the voltage of the current fluctuation signal is lower than or equal to the voltage of the set voltage signal, the comparator outputs a high level.

3. The magnetic lock according to claim 1, characterized in that: The pickup circuit includes a capacitor C2 and a resistor R9; A first end of the capacitor C2 is connected to the source of the transistor, a second end of the capacitor C2 is connected to a first end of the resistor R9 and an input end of the first preprocessing circuit; and a second end of the resistor R9 is grounded.

4. The magnetic lock according to claim 1, characterized in that: The first preprocessing circuit includes: a first filtering circuit and a first amplifying circuit; The input end of the first filter circuit is connected to the output end of the pickup circuit; the output end of the first filter circuit is connected to the input end of the first amplifier circuit, and the first filter circuit is used to filter the baseband signal; The output end of the first amplifier circuit is connected to the first input end of the comparator, and the first amplifier circuit is used to amplify the current fluctuation signal.

5. The magnetic lock according to claim 4, characterized in that: The first filter circuit includes: an RC filter circuit composed of a resistor R5, a resistor R6, a capacitor C4 and a capacitor C5; The first amplifier circuit includes: an amplifier U3, a resistor R2, and a common-phase amplifier circuit formed by a resistor R3.

6. The magnetic lock according to any one of claims 1 to 5, characterized in that: The magnetic lock also includes: a single chip microcomputer; The first input terminal of the single-chip microcomputer is connected to the output terminal of the comparator, and the output terminal of the single-chip microcomputer is connected to the gate of the transistor. The single-chip microcomputer is used to determine the target operating voltage or target operating current of the electromagnet according to the detection signal transmitted by the comparator, and transmit a PWM signal to the gate of the transistor based on the target operating voltage or target operating current.

7. The magnetic lock according to claim 6, characterized in that: The magnetic lock further includes: a second preprocessing circuit; The input end of the second preprocessing circuit is connected to the source of the transistor, the output end of the second preprocessing circuit is connected to the second input end of the single chip computer, and the second preprocessing circuit is used to preprocess the working current signal of the electromagnet; The single chip microcomputer is also used to obtain the electromagnet working current and the electromagnet working voltage according to the working current signal, and perform PID control according to the electromagnet working current and the electromagnet working voltage so that the electromagnet working current is maintained at the target working current or the electromagnet working voltage is maintained at the target working voltage.

8. The magnetic lock according to claim 7, characterized in that: The second preprocessing circuit includes: a second filtering circuit, a second amplifying circuit, and a decoupling circuit; Among them, the input end of the second filter circuit is connected to the source of the transistor, the output end of the second filter circuit is connected to the input end of the second amplifier circuit, and the second filter circuit is used to filter the baseband signal; the output end of the second amplifier circuit is connected to the input end of the decoupling circuit, and the second amplifier circuit is used to amplify the working current signal; the output end of the decoupling circuit is connected to the second input end of the microcontroller, and the decoupling circuit is used to decouple the working current signal.

9. The magnetic lock according to claim 8, characterized in that: The second filter circuit includes: a Π-type filter circuit composed of a resistor R14, a resistor R15, a capacitor C9, and a capacitor C10.

10. The magnetic lock according to claim 8, characterized in that: The second amplifier circuit includes: an amplifier U4, a resistor R13, and a resistor R16 forming a common-phase amplifier circuit.

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