Grounding detection circuit

Abstract

The utility model discloses a grounding detection circuit, which comprises a switching circuit, a signal conversion circuit and a control circuit, and is characterized in that the control circuit sends a control signal to the switching circuit, so that a circuit between a live wire output end of the switching circuit and a live wire connecting end of equipment to be detected is conducted by the switching circuit; when the to-be-detected device is connected with the mains supply and the ground wire of the mains supply is safely grounded, the signal conversion circuit outputs a first square wave signal with the same frequency as the alternating-current voltage frequency of the mains supply, so that the control circuit judges whether the ground wire of the mains supply is safely grounded or not. Therefore, the grounding detection circuit is simple in structure and low in cost, and can detect whether the connected mains supply ground wire is safely grounded or not before the to-be-detected equipment works, so that the safety of operators after the to-be-detected equipment starts to work is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of circuit protection, especially relates to a grounding detection circuit. BACKGROUND

[0002] When the electrical equipment is connected to the mains, the electrical equipment is required to be safely grounded, otherwise the human body touching the electrical equipment will have the electric shock feeling, which may cause a safety threat to the user. The ultrasonic atomization equipment is widely used in landscape manufacturing, public place disinfection and respiratory disease treatment scenes, and is also applied to related disease treatment, epidemic disease immunity and breeding environment disinfection scenes in the animal feeding process. The current ultrasonic atomization equipment is mostly small-sized equipment, and the ultrasonic atomization equipment needs to be manually moved during use to complete the atomization in a large space. Therefore, a large-sized ultrasonic atomization equipment is developed to complete the overall atomization in a large space at one time. To develop the large-sized ultrasonic atomization equipment, a large number of atomization plates need to be provided, and the atomization plates need to be powered by direct current and have a large required power. Therefore, a plurality of AC (Alternating Current) to DC (Direct Current) switching power supplies are usually used to convert the mains into direct current to power the ultrasonic atomization equipment. However, when the mains is not safely grounded, the ultrasonic electrical equipment cannot be safely grounded, and when the working environment of the ultrasonic atomization equipment is humid, the human body touching the ultrasonic atomization equipment will have the electric shock feeling, which may cause serious personnel casualties.

[0003] Therefore, in order to supervise the electrical equipment and ensure the safety of the electrical equipment operators, a grounding detection circuit needs to be designed to detect whether the mains is safely grounded before the electrical equipment is grounded. CONTENT OF THE UTILITY MODEL

[0004] The utility model aims to provide a grounding detection circuit which not only has a simple structure and low cost, but also can detect whether the connected mains ground wire is safely grounded before the to-be-detected equipment works, so as to ensure the safety of the operators when the to-be-detected equipment starts to work.

[0005] To solve the above technical problems, the utility model provides a grounding detection circuit, which comprises:

[0006] A switching circuit connected between the live wire input end and the live wire connection end of the to-be-detected equipment, used to conduct the circuit between the live wire output end of the switching circuit and the live wire connection end of the to-be-detected equipment when a control signal is received;

[0007] The signal conversion circuit is connected with the live wire output end of the switch circuit and the ground wire connection end of the device to be detected, and is used for outputting a first square wave signal with the same frequency as the alternating voltage frequency of the commercial power when the live wire connection end of the device to be detected is connected with the live wire of the commercial power, the ground wire connection end is connected with the ground wire of the commercial power, and the ground wire of the commercial power is safely grounded.

[0008] The control circuit is connected with the control end of the switch circuit and the output end of the signal conversion circuit, and is used for outputting the control signal and determining whether the commercial power is safely grounded based on whether the first square wave signal is received.

[0009] Preferably, the switch circuit comprises:

[0010] The contact of the relay is connected with the live wire input end of the device to be detected and the input end of the signal conversion circuit, and is used for being closed when the coil of the relay is powered.

[0011] The coil of the relay is connected with the first end of the transistor, and is used for being powered when the transistor is turned on.

[0012] The transistor is connected with the second end of the control circuit, and is used for being turned on when the control signal is received.

[0013] Preferably, the switch circuit further comprises:

[0014] The anti-reverse diode is connected with the second end of the coil of the relay and the first end of the coil of the relay.

[0015] Preferably, the switch circuit further comprises:

[0016] The first alarm circuit is connected with the first alarm output end of the control circuit, and is used for alarming based on the control of the control circuit when the control circuit does not detect the first square wave signal.

[0017] Preferably, the switch circuit further comprises:

[0018] The first signal amplification circuit is connected with the output end of the signal conversion circuit and the second end of the control circuit, and is used for transmitting the first square wave signal after amplification processing to the control circuit.

[0019] Preferably, the zero wire input end of the switch circuit is connected with the zero wire connection end of the device to be detected, and is further used for conducting the circuit between the zero wire output end of the switch circuit and the zero wire connection end of the device to be detected when the control signal is received.

[0020] The signal conversion circuit comprises:

[0021] The positive input end is connected with the ground connection end of the device to be detected, the negative input end is connected with the live wire output end of the switch circuit, the level pull-up end is connected with the preset high level, and the output end is connected with the second end of the control circuit.

[0022] Preferably, the signal conversion circuit further comprises:

[0023] The positive input end is connected with the ground connection end of the device to be detected, the negative input end is connected with the live wire output end of the switch circuit, the level pull-up end is connected with the preset high level, and the output end is connected with the second end of the control circuit.

[0024] Preferably, the signal conversion circuit further comprises:

[0025] The positive input end is connected with the live wire output end of the switch circuit, the negative input end is connected with the live wire output end of the switch circuit, the level pull-up end is connected with the preset high level, and the output end is connected with the third end of the control circuit.

[0026] Preferably, the signal conversion circuit further comprises:

[0027] The input end is connected with the output end of the third optocoupler relay, and the output end is connected with the third end of the control circuit.

[0028] Preferably, the signal conversion circuit further comprises:

[0029] The input end is connected with the second alarm circuit of the control circuit, and the output end is connected with the second alarm circuit of the control circuit.

[0030] The utility model provides a kind of grounding detection circuit, including switching circuit, signal conversion circuit and control circuit, control circuit sends control signal to switching circuit, to make switching circuit the circuit between own fire line output end and the fire line connecting end of to-be-detected equipment is conducted, so that signal conversion circuit is connected in to-be-detected equipment and commercial power, and the first square wave signal of the frequency same as the ac voltage frequency of commercial power is output when commercial power ground is safely grounded, to make control circuit judge whether commercial power ground is safely grounded.Visibly, the grounding detection circuit in the application not only simple structure, low in cost, but also can detect whether the commercial power ground connected before to-be-detected equipment works is safely grounded, to ensure the safety of to-be-detected equipment operator after starting work. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the utility model embodiment, the following will be needed to use the drawings in the embodiment is simply introduced, obviously, the following description in the drawings is only some embodiments of the utility model, for those skilled in the art, without creative labor, according to these drawings, other drawings can also be obtained.

[0032] Figure 1 The utility model provides a kind of grounding detection circuit's structural schematic diagram;

[0033] Figure 2 The utility model provides a kind of switching circuit's structural schematic diagram;

[0034] Figure 3 The utility model provides a kind of first signal amplification circuit's structural schematic diagram;

[0035] Figure 4 The utility model provides a kind of signal conversion circuit's structural schematic diagram;

[0036] Figure 5 The utility model provides a kind of third opto-coupler relay related connection's structural schematic diagram;

[0037] Figure 6 The utility model provides a kind of second signal amplification circuit's structural schematic diagram. DETAILED DESCRIPTION

[0038] The core of the utility model is to provide a kind of grounding detection circuit, not only simple structure, low in cost, but also can detect whether the commercial power ground connected before to-be-detected equipment works is safely grounded, to ensure the safety of to-be-detected equipment operator after starting work.

[0039] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a ground detection circuit provided by the utility model, which includes:

[0041] A switch circuit 12 whose live wire input terminal is connected to the live wire connection terminal of the device to be detected 11 is used to connect the circuit between its own live wire output terminal and the live wire connection terminal of the device to be detected 11 when receiving a control signal;

[0042] A signal conversion circuit 13 having an input end connected to the live wire output end of the switch circuit 12 and a ground end connected to the ground wire connection end of the device to be detected 11, configured to output a first square wave signal having the same frequency as the AC voltage frequency of the mains when the live wire connection end of the device to be detected 11 is connected to the live wire of the mains, the ground wire connection end is connected to the ground wire of the mains, and the ground wire of the mains is securely grounded;

[0043] The control circuit 14 has a first end connected to the control end of the switch circuit 12 and a second end connected to the output end of the signal conversion circuit 13, and is used to output a control signal and determine whether the mains power is safely grounded based on whether the first square wave signal is received.

[0044] If the device to be detected 11 is connected to the mains power but the mains power is not safely grounded, when the operator operates the device to be detected 11 , the device to be detected 11 may be grounded through the human body, which poses a great threat to the safety of the operator.

[0045] In order to detect whether the ground of the commercial power is safely grounded when the to-be-detected device 11 is connected to the commercial power, in the embodiment, the switch circuit 12 and the signal conversion circuit 13 are arranged between the live wire connection end and the ground wire connection end of the to-be-detected device 11, when the to-be-detected device 11 is connected to the commercial power and needs to be grounded, the control circuit 14 turns on the switch circuit 12, if the ground of the commercial power is safely grounded, the signal conversion circuit 13 can output a first square wave signal with the same frequency as the frequency of the alternating voltage of the commercial power, that is, the alternating voltage on the live wire of the commercial power is converted into the first square wave signal, if the control circuit 14 receives the first square wave signal, it can be determined that there is a voltage difference between the live wire and the ground wire, and the ground wire is safely grounded; and if the first square wave signal is not received, there is no voltage difference between the live wire and the ground wire, and the ground wire is not safely grounded, and the to-be-detected device 11 cannot be put into use.

[0046] Specifically, after the power plug of the to-be-detected device 11 is inserted into the commercial power socket, the live wire connection end of the to-be-detected device 11 is connected with the live wire of the commercial power, and the ground wire connection end is connected with the ground wire of the commercial power, and the ground of the commercial power is detected when the to-be-detected device 11 is not put into use.

[0047] In summary, the ground detection circuit in the application not only has simple structure and low cost, but also can detect whether the connected ground wire of the commercial power is safely grounded before the to-be-detected device 11 works, so as to ensure the safety of the operator when the to-be-detected device 11 starts to work.

[0048] On the basis of the above embodiment:

[0049] Please refer to Figure 2 , Figure 2 The utility model provides a kind of structure schematic diagram of switch circuit.

[0050] As a preferred embodiment, the switch circuit 12 includes:

[0051] The live wire input end is connected with the live wire connection end of the to-be-detected device 11, and the contact of the relay connected with the input end of the signal conversion circuit 13 is used to close when the coil of the relay is powered on;

[0052] The first end is connected with the coil of the relay, and the second end is connected with the first end of the transistor Q1, which is used to be powered on when the transistor Q1 is turned on;

[0053] The second end is grounded, and the control end is connected with the transistor Q1 of the second end of the control circuit 14, which is used to be turned on when receiving control signal.

[0054] In this embodiment, the switch circuit 12 includes the contact of the relay, the coil of the relay and the transistor Q1, the control circuit 14 sends the control signal to the transistor Q1 to make the transistor Q1 conduct, the coil of the relay is electrified after the transistor Q1 conducts, the contact of the relay is closed after the coil is electrified, the input end of the signal conversion circuit 13 is connected with the live wire of the commercial power, and the alternating current of the commercial power is converted into the first square wave signal.

[0055] Specifically, the preset high level accessed by the first end of the coil of the relay can be +48V voltage, the transistor Q1 conducts after the control circuit 14 sends the control signal to the control end of the transistor Q1, the second end of the coil of the relay is grounded through the transistor Q1, the coil of the relay is electrified to attract the contact of the relay to be closed, and the conduction of the switch circuit 12 is realized.

[0056] As a preferred embodiment, the switch circuit 12 further includes:

[0057] The anti-reverse diode D1 connected with the second end of the coil of the relay at the input end and connected with the first end of the coil of the relay at the output end.

[0058] In order to ensure the safe connection of the circuit, the anti-reverse diode D1 is arranged between the first end and the second end of the coil of the relay in this embodiment to avoid the abnormal short circuit of the circuit between the first end and the second end of the coil of the relay.

[0059] It should be noted that the first pull-down resistor R1 can also be arranged between the control end and the second end of the transistor Q1 to ensure the normal work of the transistor Q1, and the transistor Q1 can only be conducted when the control circuit 14 outputs the control signal, that is, outputs the high level to the control end of the transistor Q1.

[0060] As a preferred embodiment, the switch circuit 12 further includes:

[0061] The first alarm circuit connected with the first alarm output end of the control circuit 14 at the input end, used for alarming based on the control of the control circuit 14 when the control circuit 14 does not detect the first square wave signal.

[0062] If the control circuit 14 does not detect the first square wave signal, it indicates that the ground wire of the commercial power is not safely grounded, and the input end and the ground end of the signal conversion circuit 13 cannot form a pressure difference. In order to ensure the safety of the operator, the alarm circuit is arranged in this embodiment to control the first alarm circuit to alarm when the first square wave signal is not detected.

[0063] Specifically, the first alarm circuit in this application can be but is not limited to a sound alarm and / or a light alarm, and can timely and effectively warn the operator.

[0064] Please refer to Figure 3 ,Figure 3 A structure schematic view of the first signal amplification circuit is provided.

[0065] As a preferred embodiment, further comprising:

[0066] The first signal amplification circuit, connected between the input end and the output end of the signal conversion circuit 13 and the second end of the control circuit 14, is used for transmitting the first square wave signal after amplification and processing to the control circuit 14.

[0067] In the embodiment, the first signal amplification circuit is further provided, and the first square wave signal is amplified and processed, so that the control circuit 14 can identify the first square wave signal.

[0068] The specific structure of the first signal amplification circuit can include a first signal amplification triode Q2, the control end of the first signal amplification triode Q2 is connected with the output end of the signal conversion circuit 13, a second pull-down resistor R2 is arranged between the control end and the ground end, when the signal conversion circuit 13 outputs the first square wave signal, the first signal amplification triode Q2 is used for up pull processing of the first square wave signal, and the amplification of the first square wave signal is realized.

[0069] Please refer to Figure 4 , Figure 4 A structure schematic view of the signal conversion circuit is provided.

[0070] As a preferred embodiment, the zero line input end of the switch circuit 12 is connected with the zero line connection end of the to-be-detected equipment 11, and is further used for conducting the circuit between the zero line output end of the switch circuit 12 and the zero line connection end of the to-be-detected equipment 11 when receiving the control signal;

[0071] The signal conversion circuit 13 comprises:

[0072] The positive input end is connected with the ground line connection end of the to-be-detected equipment 11, the negative input end is connected with the fire wire output end of the switch circuit 12, the level pull-up end is connected with the preset high level, and the output end is connected with the second end of the control circuit 14.

[0073] The switch circuit 12 in the embodiment not only has a live wire input end, but also has a zero wire input end. When the live wire input end of the switch circuit 12 is connected with the live wire of the device to be detected 11, the zero wire input end is connected with the zero wire of the device to be detected 11, and the live wire connection end of the device to be detected 11 is connected with the live wire of the mains and the zero wire connection end is connected with the zero wire of the mains, the live wire input end of the switch circuit 12 is connected with the live wire of the mains and the zero wire input end is connected with the zero wire of the mains. At this time, the first optocoupler relay U1 in the signal conversion circuit 13 isolates the input end from the output end. When the ground wire of the mains is safely grounded, a pressure difference is formed between the positive input end and the negative input end, and the circuit between the level pull-up end and the output end is turned on and turned off according to the frequency of the alternating voltage of the mains, so that the first square wave signal with the same frequency as the alternating voltage of the mains is output. The high level of the first square wave signal is the preset high level.

[0074] Specifically, the input end of the first optocoupler relay U1 can be provided with a first overcurrent protection resistor R3 and a first anti-reverse diode D3 to protect the first optocoupler relay U1. The level pull-up end of the first optocoupler relay U1 can also be provided with a first pull-up resistor R5.

[0075] As can be seen, in the present application, current is only drawn from the ground wire for a short time. After the detection is completed, the ground wire is completely free of current.

[0076] By using the optocoupler relay as the signal conversion circuit 13, the strong current of the mains will not be transmitted to the weak current system of the control circuit 14, thereby ensuring the safety of the system.

[0077] As a preferred embodiment, the signal conversion circuit 13 further comprises:

[0078] The positive input end is connected with the ground wire connection end of the device to be detected 11, the negative input end is connected with the zero wire output end of the switch circuit 12, the level pull-up end is connected with the preset high level, and the output end is connected with the second optocoupler relay U2 of the second end of the control circuit 14. The second optocoupler relay U2 is used to output the first square wave signal with the same frequency as the alternating voltage of the mains when the zero wire connection end of the device to be detected 11 is connected with the live wire of the mains, the zero wire connection end is connected with the live wire of the mains, the ground wire connection end is connected with the ground wire of the mains, and the ground wire of the mains is safely grounded.

[0079] In the embodiment, when the device to be detected 11 is reversely connected, that is, the zero wire connection end is connected with the live wire of the mains and the live wire connection end is connected with the zero wire of the mains, in order to ensure that the first square wave signal can be output based on the alternating current of the live wire, the second optocoupler relay U2 is additionally provided in the embodiment. When the device to be detected 11 is reversely connected, the second optocoupler relay U2 outputs the first square wave signal with the same frequency as the alternating voltage of the mains when the ground wire of the mains is safely grounded.

[0080] When the to-be-detected device 11 is connected, that is, the zero line connection end is connected with the zero line of the commercial power, and the fire line connection end is connected with the fire line of the commercial power, the first light-coupled relay U1 still outputs the first square wave signal with the same frequency as the commercial alternating voltage frequency when the ground line of the commercial power is safely grounded.

[0081] Based on this, no matter how the to-be-detected device 11 and the commercial power are connected, the ground detection circuit can detect whether the ground line of the commercial power is safely grounded.

[0082] Specifically, the input end of the second light-coupled relay U2 can be provided with the second overcurrent protection resistor R4 and the second anti-reverse diode D4 to perform circuit protection on the second light-coupled relay U2.

[0083] Please refer to Figure 5 , Figure 5 A structure diagram related to the connection of the third light-coupled relay is provided in the utility model.

[0084] As a preferred embodiment, the utility model further comprises:

[0085] The positive input end is connected with the zero line output end of the switching circuit 12, the negative input end is connected with the fire line output end of the switching circuit 12, the level pull-up end is connected with the preset high level, the output end is connected with the third end of the third light-coupled relay U3 of the control circuit 14, and the third light-coupled relay U3 is used for outputting the second square wave signal with the same frequency as the commercial alternating voltage frequency when the to-be-detected device 11 is connected with the commercial power, so that the control circuit 14 determines that the switching circuit 12 and / or the signal conversion circuit 13 do not work normally when the second square wave signal is not received.

[0086] In the embodiment, in order to exclude the problem that the ground detection circuit cannot detect whether the ground line of the commercial power is normally grounded, the third light-coupled relay U3 is further arranged, the positive input end and the negative input end of the third light-coupled relay U3 are connected with the zero line output end and the fire line output end of the switching circuit 12, when the zero line connection end and the fire line connection end of the to-be-detected circuit are normally connected, that is, the zero line and the fire line of the commercial power are normally connected, a pressure difference is formed between the positive input end and the negative input end of the third light-coupled relay U3, so that the second square wave signal with the same frequency as the commercial alternating voltage frequency is outputted, and the second square wave signal reflects whether the ground detection circuit works normally.

[0087] Specifically, the input end of the third light-coupled relay U3 can be provided with the third overcurrent protection resistor R6 and the third anti-reverse diode D5 to perform circuit protection on the third light-coupled relay U3, and the level pull-up end of the third light-coupled relay U3 can be further provided with the second pull-up resistor R7.

[0088] Please refer to Figure 6 , Figure 6The utility model provides a kind of second signal amplification circuit's structural schematic diagram.

[0089] As a preferred embodiment, further comprising:

[0090] The input end is connected with the output end of the third opto-coupler relay U3, and the output end is connected with the third end of the control circuit 14.

[0091] In the embodiment, a second signal amplification circuit is further provided, and the second square wave signal is amplified and processed, so that the control circuit 14 can identify the second square wave signal.

[0092] The specific structure of the second signal amplification circuit can include a second signal amplification triode Q3, the control end of the second signal amplification triode Q3 is connected with the output end of the third opto-coupler relay U3, a third pull-down resistor R8 is arranged between the control end and the ground end, when the third opto-coupler relay U3 outputs the second square wave signal, the second signal amplification triode Q3 is used to perform pull-up processing on the second square wave signal, so as to amplify the second square wave signal.

[0093] As a preferred embodiment, further comprising:

[0094] The input end of the second alarm circuit is connected with the second alarm output end of the control circuit 14, and the second alarm circuit is used to alarm based on the control of the control circuit 14 when the control circuit 14 does not detect the second square wave signal.

[0095] If the control circuit 14 does not detect the second square wave signal, it indicates that the switch circuit 12 and the zero line connection end and the live line connection end of the to-be-detected circuit are not normally connected, or the grounding detection circuit has an abnormality, and the positive input end and the negative input end of the third opto-coupler relay cannot form a pressure difference, in order to ensure the accuracy of the detection result of the grounding detection circuit, the second alarm circuit is further provided in the embodiment, so as to control the second alarm circuit to alarm when the second square wave signal is not detected.

[0096] Specifically, the second alarm circuit in the application can be, but is not limited to, a sound alarm and / or a light alarm, which can timely and effectively warn the operator.

[0097] When it is necessary to detect whether the ground of the mains is safely grounded, the control circuit sends a control signal to the control terminal of the transistor Q1, i.e. the base of the transistor Q1. At this time, the transistor Q1 enters a saturated state, so that the coil of the relay is powered (the voltage is about 48V), and then the firewire input end and the zero line input end are powered through the device to be detected and the mains, the circuit between the firewire input end and the firewire output end is conducted, and the circuit between the zero line input end and the zero line output end is conducted, and the voltage of the firewire and the voltage of the zero line are sent to the signal conversion circuit. When the detection is completed, the control circuit stops sending the control signal, i.e. sends a low level to the control terminal of the transistor Q1. At this time, the transistor Q1 enters a cut-off state, so that the coil of the relay is de-energized, and the reverse electromotive force generated by the de-energization of the coil is absorbed by the anti-reverse diode D1, so as to protect the transistor Q1 from being damaged. Then, the circuit between the firewire input end and the firewire output end of the contact of the relay is disconnected, and the circuit between the zero line input end and the zero line output end is disconnected. Thus, when the device to be detected does not need to be grounded, it is completely disconnected from the mains, and no current flows, which is safer.

[0098] When the firewire output end and the zero line output end are powered, assuming that the device to be detected is correctly connected, then the firewire output end corresponds to the firewire, and the zero line output end corresponds to the zero line. When the device to be detected is reversely connected, then the firewire output end corresponds to the zero line, and the zero line output end corresponds to the firewire. In field application, this reverse connection mode is very common.

[0099] When the device to be detected is normally connected, i.e. the firewire output end corresponds to the firewire, and the zero line output end corresponds to the zero line, and the EGND is not safely grounded, under the condition that the alternating voltage on the firewire is in the "positive half cycle", D3 and D5 are cut off, there is no current between the positive input end and the negative input end of U1, and then the level pull-up end and the output end of U1 will not be conducted; there is no current between the positive input end and the negative input end of U3, and then the level pull-up end and the output end of U3 will not be conducted.

[0100] When the firewire voltage is in the "negative half cycle", D3 and D5 are conducted, the current flows from the EGND to the firewire through the positive input end, the negative input end of U1, D3 and R3, and then the level pull-up end and the output end of U1 are conducted, the output end is powered, and the high level of the first square wave signal is output; the current flows from the positive input end of U3 to the firewire through the negative input end of U3, D5 and R6, and then the level pull-up end and the output end of U3 are conducted, the output end is powered, and the high level of the second square wave signal is output.

[0101] When the device to be detected is normally connected, there will be no current flowing through the positive input end and the negative input end of U2.

[0102] When the live wire output end corresponds to the live wire, the zero line output end corresponds to the zero line, and the EGND is not safely grounded, the positive input end and the negative input end of U1 have no current at any time, and the output end cannot always be powered.

[0103] When the device to be detected is reversed, that is, the live wire output end corresponds to the zero line, the zero line output end corresponds to the live wire, and the working modes of U1, U2 and U3 are just opposite to those when the device to be detected is normally connected, which will not be described here.

[0104] The first square wave signal and the second square wave signal are relatively weak, and are synchronously amplified by Q2 and Q3 for one stage. After amplification, the first square wave signal and the second square wave signal are sent to the control circuit for further detection.

[0105] Because the voltage of the live wire is a 50Hz sine wave under standard working conditions, when only half a cycle of the first square wave signal and the second square wave signal is powered, the waveforms of the two groups of signals should be 50Hz standard square wave signals.

[0106] As known from the above, whether the device to be detected is reversed with the zero line and the live wire of the power supply or not, when not correctly grounded, the second square wave signal will always be powered in half a cycle of the frequency of the alternating voltage of the live wire, and the first square wave signal will not be powered. When correctly grounded, the first square wave signal and the second square wave signal will both be powered in half a cycle of the frequency of the alternating voltage of the live wire. Therefore, the control circuit only needs to detect the amplitude and frequency of the first square wave signal and the second square wave signal, so as to know whether the device to be detected is safely grounded. The amplitude and frequency of the second square wave signal can also be used to judge whether the grounding detection circuit is abnormal.

[0107] It should also be noted that in the present specification, relational terms such as first and second are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or apparatus including the element.

[0108] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ground detection circuit, characterized in that: include: A switch circuit having a live wire input terminal connected to a live wire connection terminal of a device to be detected, configured to conduct the circuit between its own live wire output terminal and the live wire connection terminal of the device to be detected upon receiving a control signal; A signal conversion circuit having an input end connected to the live wire output end of the switching circuit and a ground end connected to the ground wire connection end of the device to be detected, configured to output a first square wave signal having the same frequency as the AC voltage frequency of the mains when the live wire connection end of the device to be detected is connected to the live wire of the mains, the ground wire connection end is connected to the ground wire of the mains, and the ground wire of the mains is securely grounded; A control circuit having a first end connected to the control end of the switch circuit and a second end connected to the output end of the signal conversion circuit is used to output the control signal and determine whether the mains power is safely grounded based on whether the first square wave signal is received.

2. The ground detection circuit according to claim 1, wherein: The switching circuit comprises: The live wire input end is connected to the live wire connection end of the device to be detected, and the live wire output end is connected to the input end of the signal conversion circuit, and is used to close when the coil of the relay is energized; The coil of the relay, the first end of which is connected to a preset high level and the second end of which is connected to the first end of the transistor, is used to be energized when the transistor is turned on; The transistor, whose second end is grounded and whose control end is connected to the second end of the control circuit, is configured to be turned on when receiving the control signal.

3. The ground detection circuit according to claim 2, wherein: The switching circuit further includes: The input end is connected to the second end of the coil of the relay, and the output end is connected to the first end of the coil of the relay.

4. The ground detection circuit according to claim 1, wherein: Also includes: The first alarm circuit, whose input terminal is connected to the first alarm output terminal of the control circuit, is used to issue an alarm based on the control of the control circuit when the control circuit fails to detect the first square wave signal.

5. The ground detection circuit according to claim 1, wherein: Also includes: The first signal amplifying circuit, whose input end is connected to the output end of the signal conversion circuit and whose output end is connected to the second end of the control circuit, is used to amplify the first square wave signal and transmit it to the control circuit.

6. The ground detection circuit according to any one of claims 1 to 5, characterized in that: The zero line input terminal of the switch circuit is connected to the zero line connection terminal of the device to be detected, and is further used to connect the circuit between its own zero line output terminal and the zero line connection terminal of the device to be detected when receiving the control signal; The signal conversion circuit includes: The positive input terminal is connected to the ground connection terminal of the device to be detected, the negative input terminal is connected to the live wire output terminal of the switching circuit, the level pull-up terminal is connected to a preset high level connection, and the output terminal is connected to the second end of the control circuit. The first optocoupler relay is used to connect the live wire connection terminal of the device to be detected to the live wire of the mains, the neutral wire connection terminal is connected to the neutral wire of the mains, the ground wire connection terminal is connected to the ground wire of the mains, and when the ground wire of the mains is safely grounded, the output frequency is the same as the AC voltage frequency of the mains. A first square wave signal.

7. The ground detection circuit according to claim 6, wherein: The signal conversion circuit further includes: The positive input terminal is connected to the ground connection terminal of the device to be detected, the negative input terminal is connected to the zero line output terminal of the switching circuit, the level pull-up terminal is connected to the preset high level, and the output terminal is connected to the second end of the control circuit. The second optocoupler relay is used to connect the zero line connection terminal of the device to be detected to the live wire of the mains, the zero line connection terminal is connected to the live wire of the mains, the ground line connection terminal is connected to the ground wire of the mains, and when the ground wire of the mains is safely grounded, the output frequency is the same as the AC voltage frequency of the mains. A first square wave signal.

8. The ground detection circuit according to claim 6, wherein: Also includes: The positive input terminal is connected to the neutral line output terminal of the switching circuit, the negative input terminal is connected to the live line output terminal of the switching circuit, the level pull-up terminal is connected to the preset high level, and the output terminal is connected to the third end of the control circuit. The third optocoupler relay is used to output a second square wave signal with a frequency the same as the AC voltage frequency of the mains when the device to be detected is connected to the mains, so that the control circuit determines that the switching circuit and / or the signal conversion circuit is not working properly when the second square wave signal is not received.

9. The ground detection circuit according to claim 8, wherein: Also includes: The second signal amplifying circuit, whose input end is connected to the output end of the third optical coupling relay and whose output end is connected to the third end of the control circuit, is used to amplify the second square wave signal and transmit it to the control circuit.

10. The ground detection circuit according to claim 8, wherein: Also includes: The second alarm circuit, whose input terminal is connected to the second alarm output terminal of the control circuit, is used to issue an alarm based on the control of the control circuit when the control circuit fails to detect the second square wave signal.

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