Zero-cross detection circuit and detection equipment thereof
By using the charging and discharging process of rectifier modules and electrical energy storage units in the zero-crossing detection circuit, the problem of insufficient accuracy of zero-crossing detection in the prior art is solved, and a higher accuracy of zero-crossing detection is achieved.
Patent Information
- Application Number
- CN202421321650.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-11
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2034-06-11
AI Technical Summary
The existing zero crossing detection circuits are not accurate enough due to the on-voltage problem of the tertiary tube or optocoupler.
A zero-crossing detection circuit is designed, and the AC power is converted into DC power by a rectifier module, and charged by the electric energy storage unit when the AC power is not at the zero-crossing point and discharged at the zero-crossing point to generate a discharge current with a set direction, and accurately output the detection signal at the zero-crossing point.
The accuracy of zero crossing detection is improved, so that the detection signal is output more accurately at the zero crossing point of the alternating current, and is suitable for various electronic devices that require high-precision timing control.
Smart Images
Figure CN222994562U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of electronic circuits, in particular to a zero-crossing detection circuit and its detection device. Background Technique
[0002] Zero-crossing detection refers to the system detecting whether the waveform of the AC power supply passes through the zero position, including the conversion from the positive half-cycle to the negative half-cycle and the conversion from the negative half-cycle to the positive half-cycle; zero-crossing detection is usually used for frequency detection or switch control systems and is applied in many electronic devices.
[0003] The existing zero-crossing detection circuit using a triode, such as Figure 1 shown, includes: the sixth resistor R6, the sixth resistor R7, the eighth resistor R8, the ninth resistor R9, the third capacitor C3, the first power supply VCC1, and the triode Q1; specifically, the first end of the sixth resistor R6 is connected to the external power supply line and other AC power supplies to access the alternating current; the second end of the sixth resistor R6 is connected to the base of the triode Q1 through the seventh resistor R7 to reduce the circuit current and reduce the impact of current mutation on the circuit components; the first end of the eighth resistor R8 is connected to the first power supply VCC1; the second end of the eighth resistor R8 is connected to the collector of the triode Q1 and the first end of the ninth resistor; the second end of the ninth resistor R9 is grounded through the third capacitor C3 and outputs the first signal.
[0004] During actual use, when the circuit is connected to the alternating current, the base voltage of the triode Q1 changes periodically following the alternating current; at this time, when the alternating current approaches the zero-crossing point and the base voltage of the triode is less than the threshold voltage for the triode Q1 to conduct, the triode Q1 cuts off, and the first signal output by the circuit is at a high level; when the alternating current is far from the zero-crossing point and the base voltage of the triode is greater than the threshold voltage for the triode Q1 to conduct, the triode Q1 conducts; since the voltage difference between the collector and the emitter of the triode Q1 is approximately zero, the first signal output by the circuit is at a low level.
[0005] The existing zero-crossing detection circuit using an optocoupler, such as Figure 2As shown in the figure, it includes: the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the sixth diode D6, the optocoupler U2, and the second power supply VCC2; specifically, the first end of the tenth resistor R10 is connected to an external power supply line and other AC power supplies to access alternating current; the second end of the tenth resistor R10 is connected to the first end of the twelfth resistor R12 through the eleventh resistor R11; the second end of the twelfth resistor R1 is connected to the cathode of the sixth diode D6 and the first input terminal of the optocoupler U2 to reduce the circuit current; the anode of the sixth diode D6 is connected to the second input terminal of the optocoupler U2, the above-mentioned external power supply line, and other AC power supplies to prevent damage to the optocoupler U2 when the alternating current is a negative voltage; the ground terminal of the optocoupler U2 is grounded; the output terminal of the optocoupler U2 is connected to the second power supply VCC2 through the thirteenth resistor R13 and outputs a second signal.
[0006] During actual use, when the circuit is connected to alternating current, the voltage difference between the first input terminal and the second input terminal of the optocoupler U2 changes periodically with the alternating current; when the alternating current approaches the zero-crossing point, the optocoupler U2 is turned off, the light-emitting diode inside the optocoupler U2 goes out, the output terminal of the optocoupler U2 is turned off, and the second signal output by the circuit is at a high level; when the voltage difference between the first input terminal and the second input terminal of the optocoupler U2 is greater than the conduction voltage value of the optocoupler U2, the optocoupler U2 is turned on, the light-emitting diode inside the optocoupler U2 lights up, the output terminal of the optocoupler U2 is turned on, and similarly, the second signal output by the circuit is at a low level.
[0007] In the above zero-crossing detection circuit using a triode / zero-crossing detection circuit using an optocoupler, due to the conduction voltage of the triode Q1 / optocoupler U2, the zero-crossing point detection is not accurate enough. Utility Model Content
[0008] The embodiments of the present application aim to provide a zero-crossing detection circuit that can solve the defect of low accuracy of the existing zero-crossing detection circuit.
[0009] To solve the above technical problems, an embodiment of the present utility model provides a zero-crossing detection circuit. The zero-crossing detection circuit includes:
[0010] A rectification module, the input terminal of the rectification module is connected to a power supply; the rectification module is configured to: convert the alternating current of the power supply into direct current;
[0011] An electrical energy storage unit, the electrical energy storage unit is connected to the output terminal of the rectification module;
[0012] The electrical energy storage unit is configured to: when the alternating current is not at the zero-crossing point, be in a charging process, charge through the direct current to gradually increase the storage voltage; and
[0013] When the alternating current is at the zero crossing point, switch to the discharging process and gradually reduce the storage voltage to generate a discharging current with a set direction; the storage voltage is the voltage difference formed across the energy storage unit.
[0014] A detection module, the detection module is connected to the energy storage unit; the detection module is configured to: generate a high-level first detection signal when the energy storage unit is in the charging process; and generate a low-level second detection signal when the energy storage unit is in the discharging process.
[0015] Optionally, in the zero-crossing detection circuit, the detection module includes: a detection switch unit and a signal output unit; the detection switch unit is respectively connected to the energy storage unit and the signal output unit to form a detection loop between the energy storage unit and the signal output unit; wherein, the detection switch unit is configured to: keep the detection loop disconnected when the energy storage unit is in the charging process, and make the detection loop conduct when the energy storage unit is in the discharging process so that the discharging current is provided to the signal output unit; the signal output unit is configured to: generate the first detection signal when receiving the discharging current; and generate the second detection signal when not receiving the discharging current.
[0016] Optionally, in the zero-crossing detection circuit, the energy storage unit is a capacitor; the detection switch unit includes: at least one controllable switch and a third resistor; wherein, the control end of the controllable switch is connected to one end of the third resistor to form a first connection node, and the first connection node is also connected to the rectification module; the first connection end of the controllable switch is connected to the first end of the energy storage unit; the second connection end of the controllable switch is connected to one end of the signal output unit, and the second end of the energy storage unit is connected to the other end of the signal output unit to form the detection loop; the other end of the third resistor is connected to the second end of the capacitor.
[0017] Optionally, in the zero-crossing detection circuit, the detection switch unit further includes: a first diode; the negative electrode of the first diode is connected to the control end of the controllable switch, the first connection end of the controllable switch is connected to the first end of the energy storage unit; the second connection end of the controllable switch is connected to the signal output module; the first end of the energy storage unit is also connected to the positive electrode of the first diode, and the second end of the energy storage unit is connected to the signal output module.
[0018] Optionally, the zero-crossing detection circuit further includes: a fourth resistor; wherein, a first end of the fourth resistor is connected to a first end of the capacitor, and the other end of the fourth resistor is connected to the signal output unit.
[0019] Optionally, in the zero-crossing detection circuit, the signal output unit includes: an optocoupler, a fifth resistor, and a DC power supply; a first end of the optocoupler is connected to a third end of the zero-crossing detection module; a second end of the optocoupler is connected to a fourth end of the zero-crossing detection module; a third end of the optocoupler is connected to a second end of the fifth resistor and the external device, and is configured to output the second detection signal to the external device; a fourth end of the optocoupler is grounded; a first end of the fifth resistor is connected to the DC power supply.
[0020] Optionally, in the zero-crossing detection circuit, the optocoupler includes: a light-emitting diode and a phototransistor; an anode of the light-emitting diode is connected to a third end of the zero-crossing detection module; a cathode of the light-emitting diode is connected to a fourth end of the zero-crossing detection module; a collector of the phototransistor is connected to a second end of the fifth resistor; an emitter of the phototransistor is grounded.
[0021] Optionally, in the zero-crossing detection circuit, the rectification module includes: a first resistor, a second resistor, a first capacitor, and a full-wave rectifier bridge; a first end of the first resistor is connected to the external power supply line; a second end of the first resistor is connected to a first end of the first capacitor and a first end of the full-wave rectifier bridge; a first end of the second resistor is connected to the external ground wire; a second end of the second resistor is connected to a second end of the first capacitor and a second end of the full-wave rectifier bridge; a third end of the full-wave rectifier bridge is connected to a first end of the zero-crossing detection module; a fourth end of the full-wave rectifier bridge is connected to a second end of the zero-crossing detection module.
[0022] Optionally, in the zero-crossing detection circuit, the full-wave rectifier bridge includes: a second diode, a third diode, a fourth diode, and a fifth diode; an anode of the second diode is connected to an anode of the fourth diode and the electric energy storage unit; a cathode of the second diode is connected to an anode of the third diode and a second end of the first resistor; a cathode of the third diode is connected to a cathode of the fifth diode and the electric energy storage unit; a cathode of the fourth diode is connected to an anode of the fifth diode and a second end of the second resistor.
[0023] To solve the above problems, an embodiment of the present application further provides a detection device, including: the zero-crossing detection circuit as described above.
[0024] The zero-crossing detection circuit provided by the present utility model utilizes the charging and discharging processes of the electric energy storage unit to enable the detection module to accurately output a detection signal at the zero-crossing point of the AC voltage, with relatively high accuracy. Brief Description of the Drawings
[0025] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the drawings in the figures do not constitute a scale limitation.
[0026] Figure 1 is a schematic structural diagram of an existing zero-crossing detection circuit using a triode;
[0027] Figure 2 is a schematic structural diagram of an existing zero-crossing detection circuit using an optocoupler;
[0028] Figure 3 is a schematic structural diagram of the zero-crossing detection circuit provided by an embodiment of the present utility model;
[0029] Figure 4 is a schematic diagram of the principle of the zero-crossing detection circuit provided by an embodiment of the present utility model;
[0030] Figure 5 is a circuit schematic diagram of the zero-crossing detection circuit provided by another embodiment of the present utility model. Detailed Embodiments
[0031] The present utility model will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present utility model, but do not limit the utility model in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can be made. These all fall within the protection scope of the present utility model.
[0032] In order to make the purpose, technical solution and advantages of the present utility model more clear, the following further details the present application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0033] It should be noted that if there is no conflict, the various features in the embodiments of the present utility model can be combined with each other, and all are within the protection scope of the present application. In addition, although the functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order from the module division in the device or the flowchart.
[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those of ordinary skill in the technical field to which this utility model belongs. The terms used in this specification in the description of the utility model are only for the purpose of describing specific embodiments and are not intended to limit the utility model. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.
[0035] In addition, the technical features involved in the various embodiments of the utility model described below can be combined with each other as long as they do not conflict with each other.
[0036] Figure 3 The structural schematic diagram of the zero-crossing detection circuit provided by the embodiment of the utility model is shown, as Figure 3 shown: The zero-crossing detection circuit 1 includes: a rectification module 10, an electric energy storage unit 201, and a detection module 30.
[0037] Among them, the input end of the rectification module 10 is connected to the power supply 100; the rectification module 10 is configured to: convert the alternating current of the power supply 100 into direct current. The input end of the rectification module 10 can be set in any suitable form according to the actual needs. For example, as Figure 5 shown, the input end of the rectification module 10 may include: a connection end L connected to the live wire carrying voltage and a connection end N connected to the neutral wire providing a current return path.
[0038] The electric energy storage unit 201 is connected to the output end of the rectification module 10.
[0039] The electric energy storage unit 201 is configured to: when the alternating current is not at the zero-crossing point, be in the charging process, charge through direct current so that the stored voltage gradually increases; and when the alternating current is at the zero-crossing point, switch to the discharging process, gradually reduce the stored voltage to generate a discharging current with a set direction; the stored voltage is: the voltage difference formed at both ends of the electric energy storage unit 201.
[0040] The detection module 30 is connected to the electric energy storage unit 201; the detection module 30 is configured to: when the electric energy storage unit 201 is in the charging process, generate a high-level first detection signal; and when the electric energy storage unit 201 is in the discharging process, generate a low-level second detection signal.
[0041] During actual use, the power supply 100 can use an external power cord and other AC power sources to provide alternating current; the rectification module 10 can be implemented using any suitable type of hardware circuit according to actual needs, as long as it can complete the above-mentioned logical function steps; when the alternating current of the power supply 100 is not at the zero-crossing point, the detection module 30 generates a high-level first detection signal; when the alternating current of the power supply 100 is at the zero-crossing point, the detection module 30 generates a low-level second detection signal, which is used to indicate the position and time of the alternating positive and negative half-wave alternating zero-crossing point, and can be used for lamps, frequency converters, and other timing control devices.
[0042] Figure 4 shows the schematic diagram of the zero-crossing detection circuit provided by the embodiment of the present invention, as Figure 4 shown:
[0043] The rectification module 10 includes: a first resistor R1, a second resistor R2, a first capacitor C1, and a full-wave rectifier bridge BD1.
[0044] The first end of the first resistor R1 is connected to the power supply 100; the second end of the first resistor R1 is connected to the first end of the first capacitor C1 and the first input terminal of the full-wave rectifier bridge BD1.
[0045] The first end of the second resistor R2 is connected to the power supply 100; the second end of the second resistor R2 is connected to the second end of the first capacitor C1 and the second input terminal of the full-wave rectifier bridge BD1.
[0046] The output terminal of the full-wave rectifier bridge BD1 is connected to the energy storage unit 201.
[0047] During actual use, the first resistor R1 and the second resistor R2 are used to reduce the circuit current and prevent the circuit from being damaged by sudden changes in the power supply voltage; the first capacitor C1 is used to filter out high-frequency noise in the alternating current and improve the accuracy of detection; the full-wave rectifier bridge BD1 is used to convert the alternating current into direct current and charge the energy storage unit 201 when the alternating current is not at the zero-crossing point.
[0048] In this embodiment, the full-wave rectifier bridge BD1 includes: a second diode D2, a third diode D3, a fourth diode D4, and a fifth diode D5.
[0049] The anode of the second diode D2 is connected to the anode of the fourth diode D4 and the energy storage unit 201; the cathode of the second diode D2 is connected to the anode of the third diode D3 and the second end of the first resistor R1.
[0050] The cathode of the third diode D3 is connected to the cathode of the fifth diode D5 and the first end of the zero-crossing detection module 20.
[0051] The cathode of the fourth diode D4 is connected to the anode of the fifth diode D5 and the electrical energy storage unit 201.
[0052] During actual use, when the alternating current is at the zero crossing, the full-wave rectifier bridge BD1 is turned off; when the alternating current is not at the zero crossing, the full-wave rectifier bridge BD1 is turned on, and the current flows unidirectionally to the electrical energy storage unit 201; specifically, when the alternating current is a positive voltage, the voltage at the first input terminal of the full-wave rectifier bridge BD1 is greater than the voltage at the second input terminal, the third diode D3 and the fourth diode D4 are turned on, the second diode D2 and the fifth diode D5 are turned off, and the current flows out from the cathode of the third diode D3 to the electrical energy storage unit 201; when the alternating current is a negative voltage, the voltage at the first input terminal of the full-wave rectifier bridge BD1 is less than the voltage at the second input terminal, the third diode D3 and the fourth diode D4 are turned on, the second diode D2 and the fifth diode D5 are turned off, and the current flows out from the cathode of the third diode D3 to the electrical energy storage unit 201.
[0053] The detection module 30 includes: a detection switch unit 301 and a signal output unit 302.
[0054] The detection switch unit 301 is respectively connected to the electrical energy storage unit 201 and the signal output unit 302 to form a detection circuit between the electrical energy storage unit 201 and the signal output unit 302.
[0055] Among them, the detection switch unit 301 is configured to: keep the detection circuit disconnected when the electrical energy storage unit 201 is in the charging process, and turn on the detection circuit when the electrical energy storage unit 201 is in the discharging process, so that the discharge current is provided to the signal output unit 302.
[0056] The signal output unit 302 is configured to: generate a first detection signal when receiving the discharge current; and generate a second detection signal when not receiving the discharge current.
[0057] In this embodiment, the electrical energy storage unit 201 is a capacitor C2; the detection switch unit 301 includes: at least one controllable switch SW1 and a third resistor R3.
[0058] Among them, the control terminal of the controllable switch SW1 is connected to one end of the third resistor R3 to form a first connection node, and the first connection node is also connected to the rectification module 10.
[0059] The first connection end of the controllable switch SW1 is connected to the first end of the electrical energy storage unit 201; the second connection end of the controllable switch SW1 is connected to one end of the signal output unit 302, and the second end of the electrical energy storage unit 201 is connected to the other end of the signal output unit 302 to form a detection circuit.
[0060] The other end of the third resistor R3 is connected to the second end of the capacitor C2.
[0061] Furthermore, the detection switch unit 301 further includes: a first diode D1; the negative electrode of the first diode D1 is connected to the control end of the controllable switch SW1, the first connection end of the controllable switch SW1 is connected to the first end of the electric energy storage unit 201; the second connection end of the controllable switch SW1 is connected to the signal output unit 302; the first end of the electric energy storage unit 201 is also connected to the positive electrode of the first diode D1, and the second end of the electric energy storage unit 201 is connected to the signal output unit 302; it can be understood that the first diode D1 is used to limit the charging or discharging current path of the electric energy storage unit 201.
[0062] Specifically, when the electric energy storage unit 201 is in the charging process, the voltage across the capacitor C2 is lower than the voltage across the third resistor R3. At this time, the first diode D1 conducts, the control end of the controllable switch SW1 is at a low level, and the controllable switch SW1 is turned on, so that the detection circuit is disconnected; when the electric energy storage unit 201 is in the discharging process, the voltage across the capacitor C2 is higher than the voltage across the third resistor R3. At this time, the first diode D1 is cut off, the control end of the controllable switch SW1 is at a high level, and the controllable switch SW1 is closed, so that the detection circuit is turned on.
[0063] Specifically, the controllable switch SW1 can use any suitable type of electronic device according to the actual needs, as long as it can switch between the on and off states under the action of the electrical signal change generated by the charging state / discharging state of the capacitor, so as to control the on / off of the detection circuit.
[0064] For example, as Figure 5 shown, the controllable switch SW1 can be a triode Q1. The base of the triode Q1 is used as the control end, the emitter of the triode is used as the first connection end, and the collector of the triode is used as the second connection end.
[0065] Thus, when the capacitor C2 is in the charging process, the first diode D1 conducts, and the voltage difference between the base and the emitter of the triode Q1 is less than the conduction voltage of the triode. At this time, the triode Q1 remains in the cut-off state.
[0066] When the capacitor C2 is in the discharging process, the first diode D1 is cut off, so that there is a large voltage difference between the base and the emitter of the triode Q1. At this time, the triode Q1 switches to the on state.
[0067] It can be understood that when the zero-crossing detection circuit 1 is connected to the power supply 100, after a preset time, the average charging current and the average discharging current of the electric energy storage unit 201 are equal. At this time, the voltage across the electric energy storage unit 201 remains stable.
[0068] Preferably, by controlling and adjusting the resistance value, the voltage across the capacitor C2 can be maintained within a preset target range, thereby preventing excessive voltage and damaging the device.
[0069] In this embodiment, the zero-crossing detection circuit 1 further includes a fourth resistor R4.
[0070] One end of the fourth resistor R4 is connected to one end of the capacitor C2, and the other end of the fourth resistor R4 is connected to the signal output unit 302, for reducing the current in the detection circuit and minimizing the impact of current mutation on the circuit components.
[0071] The signal output unit 302 includes: an optocoupler U1, a fifth resistor R5, and a DC power supply VCC.
[0072] One end of the optocoupler U1 is connected to the electrical energy storage unit 201; the second end of the optocoupler U1 is connected to the second end of the fifth resistor R5; the third end of the optocoupler U1 is grounded.
[0073] One end of the fifth resistor R5 is connected to the DC power supply VCC.
[0074] During actual use, when the detection circuit is disconnected, the optocoupler U1 is turned off and outputs a first detection signal; when the detection circuit is connected, the optocoupler U1 is turned on and outputs a second detection signal.
[0075] In this embodiment, the optocoupler U1 includes: a light-emitting diode DS1 and a phototransistor Q2.
[0076] The anode of the light-emitting diode DS1 is connected to the electrical energy storage unit 201; the cathode of the light-emitting diode DS1 is connected to the electrical energy storage unit 201.
[0077] The collector of the phototransistor Q2 is connected to the second end of the fifth resistor R5; the emitter of the phototransistor Q2 is grounded.
[0078] It can be understood that an insulating medium is provided between the light-emitting diode DS1 and the phototransistor Q2, enabling the signal to be transmitted unidirectionally only and avoiding the influence of the output signal on the input end; specifically, when the light-emitting diode DS1 is turned on, the optical signal is transmitted to the phototransistor Q2 through the insulating medium, causing the phototransistor Q2 to turn on; when the light-emitting diode DS1 is turned off, no optical signal is transmitted to the phototransistor Q2, and the phototransistor Q2 is turned off.
[0079] In the actual use process, when the optocoupler U1 is turned off, the light-emitting diode DS1 is cut off; at this time, the phototransistor Q2 is cut off, and the collector of the phototransistor Q2 is at a high level, outputting a first detection signal; when the optocoupler U1 is turned on, the light-emitting diode DS1 is turned on; at this time, the phototransistor Q2 is turned on, and the collector of the phototransistor Q2 is at a low level, outputting a second detection signal.
[0080] In some embodiments, the optocoupler U1 can also use a light-emitting diode and a photodiode, a photoresistor, and other light-sensing devices, as long as the above-mentioned logical functions are implemented.
[0081] The technical features involved in the embodiments of the present application can be combined with each other as long as they do not conflict with each other, and can be independently applied in different embodiments as long as they do not depend on each other.
[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above. For the sake of brevity, they are not provided in detail; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A zero-crossing detection circuit, characterized in that: include: A rectifier module, wherein an input end of the rectifier module is connected to a power supply; The rectifier module is configured to: convert the alternating current of the power supply into direct current; An electric energy storage unit, wherein the electric energy storage unit is connected to an output end of the rectifier module; The electric energy storage unit is configured to: when the alternating current is not at a zero-crossing point, be in a charging process, be charged by the direct current, so that the storage voltage gradually increases; and when the alternating current is at a zero-crossing point, switch to a discharging process, gradually reduce the storage voltage, so as to generate a discharge current with a set direction; the storage voltage is: a voltage difference formed at both ends of the electric energy storage unit; A detection module, the detection module is connected to the electric energy storage unit; the detection module is configured to: generate a first detection signal of a high level when the electric energy storage unit is in a charging process; and generate a second detection signal of a low level when the electric energy storage unit is in a discharging process.
2. The zero-crossing detection circuit according to claim 1, characterized in that: The detection module includes: a detection switch unit and a signal output unit; The detection switch unit is connected to the electric energy storage unit and the signal output unit respectively to form a detection loop between the electric energy storage unit and the signal output unit; Wherein, the detection switch unit is configured to: keep the detection circuit disconnected when the electric energy storage unit is in the charging process, and turn on the detection circuit when the electric energy storage unit is in the discharging process, so that the discharge current is provided to the signal output unit; The signal output unit is configured to: generate the first detection signal when receiving the discharge current; and generate the second detection signal when not receiving the discharge current.
3. The zero-crossing detection circuit according to claim 2, characterized in that: The electric energy storage unit is a capacitor; The detection switch unit includes: a controllable switch, a first diode and a third resistor; The cathode of the first diode is connected to the control end of the controllable switch, the first connection end of the controllable switch is connected to the first end of the capacitor; the second connection end of the controllable switch is connected to the signal output unit; The first end of the capacitor is also connected to the anode of the first diode, and the second end of the capacitor is connected to the signal output unit; The control end of the controllable switch is connected to one end of the third resistor to form a first connection node, and the first connection node is also connected to the rectifier module; The first connection end of the controllable switch is connected to the first end of the capacitor; the second connection end of the controllable switch is connected to one end of the signal output unit, and the second end of the capacitor is connected to the other end of the signal output unit to form the detection loop; The other end of the third resistor is connected to the second end of the capacitor.
4. The zero-crossing detection circuit according to claim 3, characterized in that: The controllable switch comprises: a triode having a preset conduction voltage; Wherein, the base of the triode forms the control end of the controllable switch, the emitter of the triode forms the first connection end of the controllable switch, and the collector of the triode forms the second connection end of the controllable switch; When the capacitor is in the discharge process, the voltage difference between the base and the emitter of the transistor is greater than or equal to the turn-on voltage, so that the transistor is turned on; When the capacitor is in the charging process, the voltage difference between the base and the emitter of the transistor is smaller than the turn-on voltage, so that the transistor remains turned off.
5. The zero-crossing detection circuit according to claim 3, characterized in that: Also includes: a fourth resistor; Wherein, a first end of the fourth resistor is connected to a first end of the capacitor, and the other end of the fourth resistor is connected to the signal output unit.
6. The zero-crossing detection circuit according to claim 3, characterized in that: The signal output unit includes: a photoelectric coupler, a fifth resistor and a DC power supply; The first end of the photoelectric coupler is connected to the electric energy storage unit; the second end of the photoelectric coupler is connected to the second end of the fifth resistor; the third end of the photoelectric coupler is grounded; A first end of the fifth resistor is connected to the DC power supply.
7. The zero-crossing detection circuit according to claim 6, characterized in that: The photoelectric coupler includes: a light emitting diode and a photo transistor; The anode of the light emitting diode is connected to the electric energy storage unit; the cathode of the light emitting diode is connected to the electric energy storage unit; The collector of the phototransistor is connected to the second end of the fifth resistor; the emitter of the phototransistor is grounded.
8. The zero-crossing detection circuit according to claim 1, characterized in that: The rectifier module includes: a first resistor, a second resistor, a first capacitor and a full-wave rectifier bridge; The first end of the first resistor is connected to the power supply; the second end of the first resistor is connected to the first end of the first capacitor and the first input end of the full-wave rectifier bridge; The first end of the second resistor is connected to the power supply; the second end of the second resistor is connected to the second end of the first capacitor and the second input end of the full-wave rectifier bridge; The output end of the full-wave rectifier bridge is connected to the electric energy storage unit.
9. The zero-crossing detection circuit according to claim 8, characterized in that: The full-wave rectifier bridge comprises: a second diode, a third diode, a fourth diode and a fifth diode; The anode of the second diode is connected to the anode of the fourth diode and the electric energy storage unit; the cathode of the second diode is connected to the anode of the third diode and the second end of the first resistor; The cathode of the third diode is connected to the cathode of the fifth diode and the electric energy storage unit; A cathode of the fourth diode is connected to an anode of the fifth diode and a second end of the second resistor.
10. A detection device, characterized in that: It comprises the zero-crossing detection circuit described in any one of claims 1-9.