Insulation detection device

Abstract

The present invention discloses an insulation detection device. First, a primary insulation detection circuit performs insulation detection on a device under test. If the damage degree of the device under test is large at this time, it can not only detect that the impedance of the device under test is less than the first preset minimum impedance, that is, the insulation performance of the device under test is damaged, but also because the primary detection voltage is less than the safety voltage, the current generated on the device under test is also small, which will not cause a large impact on the device under test; if the primary insulation detection circuit does not detect that the insulation performance of the device under test is damaged, the secondary insulation detection circuit performs detection with a secondary detection voltage greater than the safety voltage. If the secondary impedance of the device under test is less than the second preset minimum impedance, that is, when the insulation performance of the device under test is damaged, the connection between the device under test and the secondary detection voltage is immediately disconnected to avoid burning the device under test. The alarm circuit is used to alarm, which can remind the staff to perform insulation repair on the device under test in time.

Description

Technical Field

[0001] The invention relates to the field of insulation protection, and in particular to an insulation detection device. Background Art

[0002] In order to prevent electrical equipment from leaking electricity, an insulating shell is usually set on the outside of the electrical equipment to isolate the live parts inside the electrical equipment, prevent current from leaking to the outside, and protect the safety of personnel.

[0003] However, during the transportation of electrical equipment, the insulating shell may be damaged. Therefore, before the electrical equipment is put into use, the insulation performance of the electrical equipment must be tested. The insulation testing device in the prior art usually inputs a large voltage such as 500V into the insulating shell of the electrical equipment and detects the impedance of the electrical equipment. If the impedance of the electrical equipment is large, it can be determined that the insulation performance of the electrical equipment is good. If the impedance of the electrical equipment is close to 0, it can be determined that the insulation performance of the electrical equipment is damaged and cannot be directly put into use.

[0004] However, since the voltage output by the insulation detection device in the prior art is relatively large, if the insulation performance of the electrical equipment is severely damaged, applying a large voltage to the electrical equipment during insulation testing will cause the leakage current to increase sharply, and the insulation detection device cannot be disconnected from the electrical equipment manually in time. The electrical equipment may be damaged as a result and cannot be put into use at all. Summary of the invention

[0005] The purpose of the present invention is to provide an insulation detection device, wherein the first-level insulation detection circuit first performs insulation detection on the device under test. If the damage degree of the device under test is large at this time, it can not only detect that the impedance of the device under test is less than the first preset minimum impedance, that is, the insulation performance of the device under test is damaged, but also because the first-level detection voltage is less than the safety voltage, the current generated on the device under test is also small, which will not cause a large impact on the device under test; if the first-level insulation detection circuit does not detect that the insulation performance of the device under test is damaged, the second-level insulation detection circuit performs detection with a second-level detection voltage greater than the safety voltage. If the second-level impedance of the device under test is less than the second preset minimum impedance, that is, when the insulation performance of the device under test is damaged, the connection between the device under test and the second-level detection voltage is immediately disconnected to avoid burning the device under test. The alarm circuit is used to give an alarm, which can remind the staff to repair the insulation of the device under test in time.

[0006] In order to solve the above technical problems, the present invention provides an insulation detection device, comprising:

[0007] A primary insulation detection circuit, wherein the first end is connected to a primary detection voltage, and the second end is connected to a device under test, and is used to control the device under test to access the primary detection voltage, and output a first alarm signal when it is detected that the primary impedance of the device under test is less than a first preset minimum impedance; and send a trigger signal to the secondary insulation detection circuit when it is detected that the primary impedance of the device under test is not less than the first preset minimum impedance; the primary detection voltage is less than a safety voltage;

[0008] The secondary insulation detection circuit, the first control end is connected to the trigger signal output end of the primary insulation detection device, the first end is connected to the secondary detection voltage, and the second end is connected to the device under test, and is used to control the device under test to connect to the secondary detection voltage when receiving the trigger signal, and output a second alarm signal and disconnect the device under test from the secondary detection voltage when detecting that the secondary impedance of the device under test is less than a second preset minimum impedance; the secondary detection voltage is greater than the safety voltage;

[0009] The alarm circuit has a first input end connected to the alarm signal output end of the primary insulation detection circuit, and a second input end connected to the alarm signal output end of the secondary insulation detection circuit, and is used to give an alarm when receiving the first alarm signal and / or the second alarm signal;

[0010] The primary impedance is the impedance of the device under test when receiving the primary detection voltage, and the secondary impedance is the impedance of the device under test when receiving the secondary detection voltage.

[0011] Preferably, the primary insulation detection circuit comprises:

[0012] A primary switch circuit, a first end of which is connected to a preset high level, and a second end of which is connected to a control end of a primary detection switch, and is used to be turned on based on a turn-on instruction to control the control end of the primary detection switch to be connected to the preset high level, and to be turned off after a preset time has passed to make the control end of the primary detection switch connected to the preset low level;

[0013] The first-level detection switch, the second end of which is connected to the device under test, is used to be turned on when its control end is connected to the preset high level, and to connect the device under test to the first-level detection voltage, and to be turned off when its control end is connected to the preset low level;

[0014] A primary current detection circuit, wherein the first end is connected to the primary detection voltage, the second end is connected to the first end of the primary detection switch, the alarm signal output end is connected to the alarm circuit, and the trigger signal output end is connected to the first control end of the secondary insulation detection circuit, and is used to detect the primary current flowing through the device under test, and output the first alarm signal when it is detected that the primary current is greater than the primary preset minimum current; and send a trigger signal to the secondary insulation detection circuit when it is detected that the primary current is not greater than the primary preset minimum current;

[0015] The primary current is negatively correlated with the primary impedance, and the primary preset minimum current is a current threshold value set based on the primary preset minimum impedance.

[0016] Preferably, the primary current detection circuit comprises:

[0017] A primary sampling resistor, a first end of which is connected to the primary detection voltage, and a second end of which is connected to the first end of the primary detection switch;

[0018] A primary sampling module, wherein a first input terminal is connected to a first terminal of the primary sampling resistor, and a second input terminal is connected to a second terminal of the primary sampling resistor, and is used to collect voltages across the primary sampling resistor;

[0019] A primary comparison module, wherein the first input terminal is connected to the output terminal of the primary sampling module, and the second input terminal is connected to a primary preset voltage threshold, and is used to output the preset high level when the voltage across the primary sampling resistor is greater than the primary preset voltage threshold, and output a preset low level when the voltage across the primary sampling resistor is not greater than the primary preset voltage threshold; the primary preset voltage threshold is a voltage threshold set based on the resistance value of the primary sampling resistor and the primary preset minimum current; the preset low level is different from the preset high level;

[0020] A first pull-up resistor, a first end of which is connected to the preset high level, and a second end of which is connected to the output end of the first-level comparison module;

[0021] A first logic gate circuit, wherein the first input end is connected to the output end of the first-level comparison module, the second input end is connected to the preset high level, and the output end is connected to the input end of the alarm circuit and the control end of the second-level insulation detection circuit, and is used to output the preset high level when the levels of the first input end and the second input end are different, otherwise output the preset low level;

[0022] The second control end of the secondary insulation detection circuit is connected to the primary detection switch, and is specifically used to control the device under test to access the secondary detection voltage when the first logic gate circuit outputs the preset high level and the primary switch circuit is disconnected, and when it is detected that the secondary impedance of the device under test is less than a second preset minimum impedance, output the second alarm signal and disconnect the connection between the device under test and the secondary detection voltage;

[0023] The alarm circuit is specifically configured to generate an alarm when detecting that the output of the first logic gate circuit changes from the preset low level to the preset high level, and / or when receiving the second alarm signal.

[0024] Preferably, the primary switch circuit comprises:

[0025] a switch module, a first end of which is connected to the preset high level, and a second end of which is connected to the first end of the switch holding circuit, and is configured to be turned on upon receiving the turn-on instruction so that the first end of the switch holding circuit is connected to the preset high level, and to be turned off after the preset time has passed;

[0026] The switch holding circuit, the second end of which is connected to the set end of the first latch, is used to be turned on when the switch module is turned on, so that the set end of the first latch is connected to the preset high level, and is turned off after the preset time has passed, so that the set end of the first latch is connected to the preset low level;

[0027] The first latch, the reset end is connected to the output end of the second logic gate circuit, the first output end is connected to the control end of the primary detection switch, and is used to output the preset high level to the control end of the primary detection switch when the reset end of the first latch receives the preset low level and the set end receives the preset high level, and output the preset low level to the control end of the primary detection switch when the reset end of the first latch receives the preset high level and the set end receives the preset low level;

[0028] The second logic gate circuit has a first input terminal connected to the second terminal of the switch holding circuit, and a second input terminal connected to the output terminal of the third logic gate circuit, and is used to output the preset high level when the levels of the first input terminal and the second input terminal are different, and otherwise output the preset low level;

[0029] The third logic gate circuit has a first input end connected to the output end of the first logic gate circuit, and a second input end connected to the output end of the fourth logic gate circuit, and is configured to output the preset high level when the first input end and / or the second input end thereof receives the preset low level, and otherwise output the preset low level;

[0030] The fourth logic gate circuit has a first input terminal connected to the preset high level, and a second input terminal connected to the output terminal of the first-level comparison module, and is configured to output the preset high level when both the first input terminal and the second input terminal receive the preset high level, and otherwise output the preset low level;

[0031] A first pull-down resistor has a first end connected to the second end of the switch holding circuit and a second end grounded.

[0032] Preferably, the primary switch circuit further includes:

[0033] a fifth logic gate circuit, wherein the first input end is connected to the second end of the switch module, the second input end is disconnected from the alarm signal output of the secondary insulation detection circuit, and the output end is connected to the first end of the switch holding circuit, and is used for outputting the preset high level when the first input end and / or the second input end thereof receives the preset high level, otherwise outputting the preset low level; the second alarm signal is the preset high level;

[0034] A second pull-down resistor, a first end of which is connected to the first input end of the fifth logic gate circuit, and a second end of which is grounded;

[0035] The switch module is specifically configured to be turned on upon receiving the turn-on instruction, so that the first input terminal of the fifth logic gate circuit is connected to the preset high level, and to be turned off after the preset time has passed;

[0036] The switch holding circuit is specifically used to be turned on when the fifth logic gate circuit outputs the preset high level, so that the set end of the first latch is connected to the preset high level, and is turned off after a preset time.

[0037] Preferably, the first latch is further configured to output the preset low level from its second output terminal when its reset terminal receives the preset low level and its set terminal receives the preset high level, and to output the preset high level from its second output terminal when its reset terminal receives the preset high level and its set terminal receives the preset low level;

[0038] The secondary insulation detection circuit comprises:

[0039] A secondary switch circuit, wherein the first end is connected to the preset high level, the second input end is connected to the trigger signal output end of the primary insulation detection circuit, the third input end is connected to the second output end of the first latch, the fourth input end is connected to the output end of the secondary current detection circuit, and the output end is connected to the control end of the secondary detection switch, and is used for receiving the trigger signal and the second output end of the first latch is changed from the preset low level to the preset high level, and the secondary current detection circuit outputs the preset low level, outputting the preset high level to the control end of the secondary detection switch, otherwise outputting the preset low level to the control end of the secondary detection switch;

[0040] The secondary detection switch has a first end connected to the first end of the secondary current detection circuit and a second end connected to the device under test, and is used to be turned on when its control end is connected to the preset high level and to connect the device under test to the secondary detection voltage, and to be turned off when its control end is connected to the preset low level;

[0041] The secondary current detection circuit, the second end is connected to the first end of the secondary detection switch, the alarm signal output end is connected to the alarm circuit, and is used to detect the secondary current flowing through the device under test, and output the second alarm signal when it is detected that the secondary current is greater than the secondary preset minimum current;

[0042] The secondary current is negatively correlated with the secondary impedance, and the secondary preset minimum current is a current threshold value set based on the secondary preset minimum impedance.

[0043] Preferably, the secondary current detection circuit comprises:

[0044] A current transformer, the primary side of which is connected between the secondary detection voltage and the first end of the secondary detection switch, and the secondary side is connected to the first end and the second end of the secondary sampling resistor, for sensing the secondary current flowing through the device under test;

[0045] The secondary sampling resistor is used to collect the current of the secondary side of the current transformer;

[0046] A secondary sampling module, wherein a first input end is connected to a first end of the secondary sampling resistor, and a second input end is connected to a second end of the secondary sampling resistor, and is used to collect voltages across the two ends of the secondary sampling resistor;

[0047] A secondary comparison module, wherein the first input terminal is connected to the output terminal of the secondary sampling module, and the second input terminal is connected to the secondary preset voltage threshold, and is used to output the preset high level when the voltage across the secondary sampling resistor is greater than the secondary preset voltage threshold, and output the preset low level when the voltage across the secondary sampling resistor is not greater than the secondary preset voltage threshold; the secondary preset voltage threshold is a voltage threshold set based on the resistance value of the secondary sampling resistor and the secondary preset minimum current;

[0048] A first trigger, whose clock signal input terminal is connected to the output terminal of the secondary comparison module, and whose output terminal is connected to the alarm circuit, is used to output the preset high level when detecting that the output of the secondary comparison module changes from the preset low level to the preset high level, otherwise output the preset low level;

[0049] The alarm circuit is specifically configured to generate an alarm when detecting that the output of the first trigger changes from the preset low level to the preset high level.

[0050] Preferably, the secondary switch circuit comprises:

[0051] A second trigger, whose clock signal input terminal is connected to the trigger signal output terminal of the primary insulation detection circuit, and whose output terminal is connected to the trigger terminal of the third trigger, is used to output the preset low level when the output of the first logic gate circuit changes from the preset low level to the preset high level, otherwise output the preset high level;

[0052] A third trigger, whose clock signal input terminal is connected to the second output terminal of the first latch, whose reset terminal is connected to the output terminal of the secondary current detection circuit, and whose output terminal is connected to the control terminal of the secondary detection switch, is used for outputting the preset high level when the second trigger outputs the preset high level, the output of the second output terminal of the first latch changes from the preset low level to the preset high level, and the secondary current detection circuit does not detect that the secondary current is greater than the secondary preset minimum current, outputting the preset high level, otherwise outputting the preset low level.

[0053] Preferably, the secondary switch circuit further includes:

[0054] The first end is connected to the clock signal input end of the third trigger, and the second end is connected to the charging capacitor connected to the ground.

[0055] Preferably, the alarm circuit comprises:

[0056] A fourth trigger, wherein the clock signal input end is connected to the alarm signal output end of the primary insulation detection circuit, and the output end is connected to the first end of the first alarm module, and is used to output a preset low level when the first alarm signal is received, otherwise output a preset high level; the preset high level is opposite to the preset low level;

[0057] The first alarm module, the second end of which is connected to the preset high level, is used to alarm when the fourth trigger outputs the preset low level;

[0058] The second alarm module is connected to the alarm signal output terminal of the secondary insulation detection circuit and is used for giving an alarm when receiving the second alarm signal.

[0059] The present application provides an insulation detection device, in which the insulation detection of the device under test is first performed by a primary insulation detection circuit. If the damage degree of the device under test is large at this time, it can not only detect that the impedance of the device under test is less than the first preset minimum impedance, that is, the insulation performance of the device under test is damaged, but also because the primary detection voltage is less than the safety voltage, the current generated on the device under test is also small, which will not cause a significant impact on the device under test; if the primary insulation detection circuit does not detect the insulation performance damage of the device under test, the secondary insulation detection circuit will perform the detection with a secondary detection voltage greater than the safety voltage. If the secondary impedance of the device under test is less than the second preset minimum impedance, that is, when the insulation performance of the device under test is damaged, the connection between the device under test and the secondary detection voltage is immediately disconnected to avoid burning the device under test. The alarm circuit can be used to alert the staff to promptly repair the insulation of the device under test. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 A schematic structural diagram of an insulation detection device provided by the present invention;

[0062] Figure 2 A schematic diagram of the structure of a primary insulation detection circuit provided by the present invention;

[0063] Figure 3 A schematic diagram of the structure of a secondary insulation detection circuit provided by the present invention;

[0064] Figure 4 A schematic diagram of an alarm circuit provided by the present invention;

[0065] Figure 5 A simulation circuit diagram of an RC charging and discharging circuit provided by the present invention;

[0066] Figure 6 A simulation result diagram of an RC charging and discharging circuit provided by the present invention;

[0067] Figure 7 A test timing diagram for detecting a fault-free insulation state of the device under test after pressing the switch module after power-on provided by the present invention;

[0068] Figure 8 A test timing diagram of the primary insulation detection circuit detecting the existence of a fault state of the insulation of the device under test after the switch module is pressed after power-on provided by the present invention;

[0069] Fig. 9 The present invention provides a test timing diagram in which after the switch module is powered on and pressed, the upper insulation detection circuit detects that the insulation of the tested device is in a fault-free state, but the secondary insulation detection circuit detects that the insulation of the tested device is in a faulty state. DETAILED DESCRIPTION

[0070] The core of the present invention is to provide an insulation detection device. First, the first-level insulation detection circuit performs insulation detection on the device under test. If the damage degree of the device under test is large at this time, it can not only detect that the impedance of the device under test is less than the first preset minimum impedance, that is, the insulation performance of the device under test is damaged, but also because the first-level detection voltage is less than the safety voltage, the current generated on the device under test is also small, which will not cause a large impact on the device under test; if the first-level insulation detection circuit does not detect that the insulation performance of the device under test is damaged, the second-level insulation detection circuit will perform detection with a second-level detection voltage greater than the safety voltage. If the second-level impedance of the device under test is less than the second preset minimum impedance, that is, when the insulation performance of the device under test is damaged, the connection between the device under test and the second-level detection voltage is immediately disconnected to avoid burning the device under test. The alarm circuit can be used to alert the staff to promptly repair the insulation of the device under test.

[0071] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 described embodiments 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 creative work are within the scope of protection of the present invention.

[0072] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of an insulation detection device provided by the present invention, the device comprises:

[0073] A primary insulation detection circuit 1, a first end connected to a primary detection voltage, and a second end connected to a device under test 4, for controlling the device under test 4 to access the primary detection voltage VCC, and outputting a first alarm signal when it is detected that the primary impedance of the device under test 4 is less than a first preset minimum impedance; when it is detected that the primary impedance of the device under test 4 is not less than the first preset minimum impedance, a trigger signal is sent to the secondary insulation detection circuit 2; the primary detection voltage VCC is less than the safety voltage;

[0074] A secondary insulation detection circuit 2, wherein the first control end is connected to the trigger signal output end of the primary insulation detection device, the first end is connected to the secondary detection voltage, and the second end is connected to the device under test 4, and is used to control the device under test 4 to connect to the secondary detection voltage when receiving the trigger signal, and output a second alarm signal and disconnect the connection between the device under test 4 and the secondary detection voltage when it is detected that the secondary impedance of the device under test 4 is less than the second preset minimum impedance; the secondary detection voltage is greater than the safety voltage;

[0075] An alarm circuit 3, wherein a first input terminal is connected to an alarm signal output terminal of the primary insulation detection circuit 1, and a second input terminal is connected to an alarm signal output terminal of the secondary insulation detection circuit 2, and is used for giving an alarm when receiving a first alarm signal and / or a second alarm signal;

[0076] The primary impedance is the impedance of the device under test 4 when receiving the primary detection voltage VCC, and the secondary impedance is the impedance of the device under test 4 when receiving the secondary detection voltage.

[0077] When the insulation performance of the device under test 4 is normal, the impedance of the device under test 4 will be infinite. If voltage is applied to the device under test 4, no current will pass through. If the insulation performance of the device under test 4 is abnormal, the impedance of the device under test 4 will decrease. Then, after voltage is applied to the device under test 4, current will pass through the device under test 4.

[0078] In the present application, when the insulation test is performed on the device under test 4, the first-level insulation detection circuit 1 first performs the test. If the first-level insulation detection circuit 1 detects that the insulation of the device under test 4 is abnormal, the first alarm signal is directly output to make the alarm circuit 3 alarm. If the first-level insulation detection circuit 1 does not detect the insulation abnormality of the device under test 4, in order to further determine whether the insulation performance of the device under test 4 is normal, the insulation test of the device under test 4 is performed by the second-level insulation detection circuit 2. If the insulation abnormality of the device under test 4 is still not detected, it can be determined that the insulation performance of the device under test 4 is intact. If the insulation abnormality of the device under test 4 is detected, the second alarm signal is output to make the alarm circuit 3 alarm.

[0079] Specifically, when the primary insulation detection circuit 1 performs insulation detection on the device under test 4, it first controls the device under test 4 to access the primary detection voltage VCC, thereby detecting the primary impedance of the device under test 4, that is, the primary impedance reflected by the device under test 4 after accessing the primary detection voltage VCC. If the primary impedance of the device under test 4 is less than the first preset minimum impedance, the primary insulation detection device directly outputs a first alarm signal, and an alarm is sounded through the alarm circuit 3 to prompt that the insulation of the device under test 4 is abnormal. However, if the primary impedance of the device under test 4 is not less than the first preset minimum impedance, the insulation performance of the device under test 4 may be normal, or the insulation abnormality of the device under test 4 cannot be detected because the detection voltage is less than the safety voltage. At this time, the primary insulation monitoring circuit outputs a trigger signal to the secondary insulation detection circuit 2, and the secondary insulation detection circuit 2 performs further insulation detection.

[0080] Since the first-level detection voltage VCC is lower than the safety voltage, such as the first-level detection voltage VCC is 12V, the first-level detection voltage VCC is a voltage that will not pose a safety threat to the human body. When the first-level detection voltage VCC is used to perform insulation detection on the device under test 4, it can be detected that the first-level impedance of the device under test 4 is lower than the first preset minimum impedance when the insulation performance of the device under test 4 is severely damaged. However, if the insulation performance of the device under test 4 is less damaged, the first-level detection voltage VCC cannot detect whether the insulation of the device under test 4 is damaged. Based on this, in this application, the primary insulation detection circuit 1 and the secondary insulation detection circuit 2 are used for detection together. When the secondary insulation detection circuit 2 receives the trigger signal sent by the primary insulation detection circuit 1, it controls the device under test 4 to access the secondary detection voltage. Since the secondary detection voltage is greater than the safety voltage, the insulation performance of the device under test 4 can be damaged. When the degree of damage is small, it is detected that the secondary impedance of the device under test 4 is less than the second preset minimum impedance, thereby outputting a second alarm signal to indicate that the insulation performance is damaged, and disconnecting the connection between the device under test 4 and the secondary detection voltage to protect the device under test 4 and the staff, and prevent the device under test 4 from being burned by the larger secondary detection voltage. Among them, in order to improve the accuracy of the secondary insulation detection circuit 2 in detecting the insulation performance of the device under test 4, the secondary detection voltage can be a large voltage of 500V, which is not limited in this application.

[0081] Among them, because the insulation damage degree of the device under test 4 is different, the impedance it exhibits is different. Therefore, in this embodiment, the primary impedance when the device under test 4 is connected to the primary detection voltage VCC and the secondary impedance when the device under test 4 is connected to the secondary detection voltage are distinguished.

[0082] In summary, the first-level insulation detection circuit first performs insulation detection on the device under test. If the damage degree of the device under test is large at this time, it can not only detect that the impedance of the device under test is less than the first preset minimum impedance, that is, the insulation performance of the device under test is damaged, but also because the first-level detection voltage is less than the safety voltage, the current generated on the device under test is also small, which will not cause a large impact on the device under test; if the first-level insulation detection circuit does not detect that the insulation performance of the device under test is damaged, the second-level insulation detection circuit will perform detection with a second-level detection voltage greater than the safety voltage. If the second-level impedance of the device under test is less than the second preset minimum impedance, that is, when the insulation performance of the device under test is damaged, the connection between the device under test and the second-level detection voltage is immediately disconnected to avoid burning the device under test. The alarm circuit can be used to alert the staff to promptly repair the insulation of the device under test.

[0083] Based on the above embodiments:

[0084] As a preferred embodiment, the primary insulation detection circuit 1 includes:

[0085] A primary switch circuit, a first end of which is connected to a preset high level VCC1, and a second end of which is connected to the control end of the primary detection switch Q1, and is used to be turned on based on a turn-on instruction to control the control end of the primary detection switch Q1 to be connected to the preset high level VCC1, and to be turned off after a preset time, so that the control end of the primary detection switch Q1 is connected to a preset low level;

[0086] The first-level detection switch Q1 has a second end connected to the device under test 4, and is used to be turned on when its control end is connected to a preset high level VCC1, and to connect the device under test 4 to the first-level detection voltage VCC, and to be turned off when its control end is connected to a preset low level;

[0087] A primary current detection circuit, wherein the first end is connected to a primary detection voltage VCC, the second end is connected to a first end of a primary detection switch Q1, the alarm signal output end is connected to an alarm circuit 3, and the trigger signal output end is connected to a first control end of a secondary insulation detection circuit 2, and is used to detect a primary current flowing through a device under test 4, and output a first alarm signal when it is detected that the primary current is greater than a primary preset minimum current; and send a trigger signal to the secondary insulation detection circuit 2 when it is detected that the primary current is not greater than a primary preset minimum current;

[0088] The primary current is negatively correlated with the primary impedance, and the primary preset minimum current is a current threshold value set based on the primary preset minimum impedance.

[0089] In this embodiment, the primary switch circuit in the primary insulation detection circuit 1 is used to connect the control end of the primary detection switch Q1 to the preset high level VCC1, that is, when receiving the conduction instruction to detect the device under test 4, the primary detection switch Q1 is turned on so as to connect the device under test 4 to the primary detection voltage VCC. After the device under test 4 is connected to the primary detection voltage VCC, if the insulation performance of the device under test 4 is good, the primary impedance of the device under test 4 is infinite, or the insulation performance of the device under test 4 is slightly damaged, and the primary impedance of the device under test 4 is large, resulting in no current passing through the device under test 4, or the primary current flowing through is very small. After detecting that the primary current flowing through the device under test 4 is not greater than the primary preset minimum current, the primary current detection circuit can determine that the insulation performance of the device under test 4 is good, or no major damage has occurred, and does not directly output the first alarm signal, but sends a trigger signal to the secondary insulation detection circuit 2, so that the secondary insulation detection circuit 2 further detects whether the device under test 4 has been damaged in a way that is not easily noticeable.

[0090] Since the primary switch circuit is disconnected after the preset time, the primary detection switch Q1 can be disconnected in time after the primary current flowing through the device under test 4 is detected, so as to avoid damage to the device under test 4 due to loading the primary detection switch Q1 when a serious insulation performance abnormality occurs. Since the current on the device under test 4 changes rapidly, the preset time can be set to a time in milliseconds.

[0091] It should be noted that when the primary switch circuit is not turned on, the primary detection switch Q1 is in the off state. Since the device under test 4 is not connected to the primary detection voltage VCC, no current passes through it. The primary current detection circuit cannot detect the current and will not alarm or output a trigger signal.

[0092] As a preferred embodiment, the primary current detection circuit includes:

[0093] A first-level sampling resistor R3, a first end of which is connected to a first-level detection voltage VCC, and a second end of which is connected to a first end of a first-level detection switch Q1;

[0094] A primary sampling module U2, a first input end connected to a first end of a primary sampling resistor R3, a second input end connected to a second end of the primary sampling resistor R3, for collecting voltages across the primary sampling resistor R3;

[0095] A first-level comparison module U4, a first input terminal connected to the output terminal of the first-level sampling module U2, a second input terminal connected to the first-level preset voltage threshold Vref1, for outputting a preset high level VCC1 when the voltage across the first-level sampling resistor R3 is greater than the first-level preset voltage threshold Vref1, and outputting a preset low level when the voltage across the first-level sampling resistor R3 is not greater than the first-level preset voltage threshold Vref1; the first-level preset voltage threshold Vref1 is a voltage threshold set based on the resistance value of the first-level sampling resistor R3 and the first-level preset minimum current; the preset low level is different from the preset high level VCC1;

[0096] A first pull-up resistor R1, a first end of which is connected to a preset high level VCC1, and a second end of which is connected to an output end of a first-level comparison module;

[0097] A first logic gate circuit U1, wherein a first input terminal is connected to an output terminal of a primary comparison module, a second input terminal is connected to a preset high level VCC1, and an output terminal is connected to an input terminal of an alarm circuit 3 and a control terminal of a secondary insulation detection circuit 2, and is used for outputting a preset high level VCC1 when the levels of its first input terminal and its second input terminal are different, and otherwise outputting a preset low level;

[0098] The second control end of the secondary insulation detection circuit 2 is connected to the primary detection switch Q1, and is specifically used to control the device under test 4 to access the secondary detection voltage when the first logic gate circuit U1 outputs a preset high level VCC1 and the primary switch circuit is disconnected, and when it is detected that the secondary impedance of the device under test 4 is less than the second preset minimum impedance, output a second alarm signal and disconnect the connection between the device under test 4 and the secondary detection voltage;

[0099] The alarm circuit 3 is specifically configured to generate an alarm when detecting that the output of the first logic gate circuit U1 changes from a preset low level to a preset high level VCC1 and / or when receiving a second alarm signal.

[0100] Please refer to Figure 2 , Figure 2A structural schematic diagram of a primary insulation detection circuit provided by the present invention, wherein a primary sampling resistor R3 is arranged between a primary detection voltage VCC and a primary detection switch Q1, after the primary detection switch Q1 is turned on, the primary sampling resistor R3 and the device under test 4 are connected in series, the current flowing through the device under test 4 is the same as the current flowing through the primary sampling resistor R3, and the voltage across the primary sampling resistor R3 can reflect the primary current flowing through the primary sampling resistor R3, that is, the primary current is the ratio of the voltage across the primary sampling resistor R3 to the resistance value of the primary sampling resistor R3, and the primary current is positively correlated with the voltage across the primary sampling resistor R3. Based on this, the primary preset voltage threshold Vref1 is the primary sampling voltage. The product of the resistance value of the resistor R3 and the first-level preset minimum current is obtained by collecting the voltage across the first-level sampling resistor R3, and comparing the voltage across the first-level sampling resistor R3 with the first-level preset voltage threshold Vref1. If the voltage across the first-level sampling resistor R3 is greater than the first-level preset voltage threshold Vref1, the first-level current is greater than the first-level preset minimum current, and the insulation performance of the device under test 4 is abnormal. The first-level comparison module U4 outputs a preset high level VCC1. If the voltage across the first-level sampling resistor R3 is not greater than the first-level preset voltage threshold Vref1, the first-level current is not greater than the first-level preset minimum current, and the insulation performance of the device under test 4 is not detected to be abnormal. The first-level comparison module U4 outputs a preset low level.

[0101] When the primary switch circuit is not turned on, but the primary insulation detection circuit 1 is powered on, the primary detection switch Q1 is in the off state, no current flows through the device under test 4 and the primary sampling resistor R3, and the voltage difference between the two ends of the primary sampling resistor R3 is 0V, that is, V R3 =0V, the output of the primary sampling module U2 is , the voltage of the IN+ pin of the first-level comparison circuit U4 is less than the voltage Vref1 of the IN- pin, and the preset low level is output. The first input terminal of the first logic gate circuit U1 is the preset low level, and the second input terminal is the preset high level VCC1. Then, the levels of the first input terminal and the second input terminal of the first logic gate circuit U1 are different, and thus the preset high level VCC1 is continuously output;

[0102] After power-on, the first-level switch circuit is turned on, and the insulation performance of the device under test 4 is good, or the damage is not serious, the first-level comparison circuit U4 outputs a preset low level, the first input end of the first logic gate circuit U1 is the preset low level, and the second input end is the preset high level VCC1, then the levels of the first input end and the second input end of the first logic gate circuit U1 are different, and thus the preset high level VCC1 is continuously output; since the first-level switch circuit is disconnected after a preset time, after the first-level switch circuit is disconnected, the first-level detection switch Q1 is also disconnected, the device under test 4 is disconnected from the first-level detection voltage VCC, no current flows through the device under test 4 and the first-level sampling resistor R3, the first-level comparison module outputs a preset low level, and the first logic gate circuit U1 still outputs the preset high level VCC1.

[0103] After power-on, the first-level switch circuit is turned on. If the insulation performance of the device under test 4 is greatly damaged and the first-level comparison circuit U4 outputs a preset high level VCC1, the first input end of the first logic gate circuit U1 is pulled to the preset high level VCC1, and the second input end is the preset high level VCC1, then the first input end and the second input end of the first logic gate circuit U1 are at the same level, and the output changes from the preset high level VCC1 to the preset low level, that is, a falling edge signal is output; because the first-level switch circuit is disconnected after a preset time, after the first-level switch circuit is disconnected, the first-level detection switch Q1 is also disconnected, the device under test 4 is disconnected from the first-level detection voltage VCC, no current flows through the device under test 4 and the first-level sampling resistor R3, and the first-level comparison module outputs a preset low level, resulting in the first input end of the first logic gate circuit U1 being the preset low level, the second input end being the preset high level VCC1, and the output of the first logic gate circuit U1 changing from the preset low level to the preset high level VCC1, that is, when the first-level switch circuit is disconnected, the first logic gate circuit U1 outputs a rising edge signal, triggering the alarm circuit 3 to alarm.

[0104] Among them, the primary detection switch Q1 can be but not limited to NMOS (N-Metal-Oxide-Semiconductor, N-type metal oxide semiconductor), the gate of NMOS is the control terminal, the source is connected to the device under test 4, and the drain is connected to the second end of the primary sampling resistor R3. A resistor R2 can also be set between RG+ and RG- of the primary sampling module U2. The second input terminal of the primary comparison module U4 can be connected to the primary preset voltage threshold Vref1 through the first current limiting resistor R5. Figure 2 The Rload in is the device under test 4.

[0105] As a preferred embodiment, the primary switch circuit includes:

[0106] The switch module S1 has a first end connected to a preset high level VCC1, and a second end connected to a first end of a switch holding circuit, and is used to be turned on when receiving a turn-on instruction, so that the first end of the switch holding circuit is connected to the preset high level VCC1, and is turned off after a preset time;

[0107] The switch holding circuit has a second end connected to the set end of the first latch U6, and is used to be turned on when the switch module S1 is turned on, so that the set end of the first latch U6 is connected to a preset high level VCC1, and is turned off after a preset time, so that the set end of the first latch U6 is connected to a preset low level;

[0108] The first latch U6, whose reset end is connected to the output end of the second logic gate circuit U15, and whose first output end is connected to the control end of the primary detection switch Q1, is used to output a preset high level VCC1 to the control end of the primary detection switch Q1 when its reset end receives a preset low level and its set end receives a preset high level VCC1, and output a preset low level to the control end of the primary detection switch Q1 when its reset end receives a preset high level VCC1 and its set end receives a preset low level;

[0109] A second logic gate circuit U15, a first input terminal connected to the second terminal of the switch holding circuit, a second input terminal connected to the output terminal of the third logic gate circuit U3, for outputting a preset high level VCC1 when the levels of the first input terminal and the second input terminal thereof are different, and otherwise outputting a preset low level;

[0110] A third logic gate circuit U3, a first input terminal connected to the output terminal of the first logic gate circuit U1, a second input terminal connected to the output terminal of the fourth logic gate circuit U5, and configured to output a preset high level VCC1 when the first input terminal and / or the second input terminal thereof receives a preset low level, and otherwise output a preset low level;

[0111] A fourth logic gate circuit U5, a first input terminal of which is connected to a preset high level VCC1, and a second input terminal of which is connected to the output terminal of the first-level comparison module, and is used for outputting a preset high level VCC1 when both the first input terminal and the second input terminal thereof receive the preset high level VCC1, and outputting a preset low level otherwise;

[0112] The first pull-down resistor R23 has a first end connected to the second end of the switch holding circuit and a second end grounded.

[0113] When the switch module S1 is not turned on, and after the primary insulation detection circuit 1 is powered on, the switch holding circuit is not turned on, the set end of the first latch U6 is a preset low level, so that the control end of the primary detection switch Q1 is a preset low level, and the primary detection switch Q1 is in an off state. At this time, no current passes through the device under test 4 and the primary sampling resistor R3. When the primary comparison circuit U4 outputs a preset low level, the first input end of the first logic gate circuit U1 and the second end of the fourth logic gate circuit U5 are preset low levels, and the second input end of the first logic gate circuit U1 and the first input end of the fourth logic gate circuit U5 are pulled up to a preset high level VCC1 by the first pull-up resistor R1. Then, the first logic gate circuit U1 continues to output the preset high level VCC1 due to the different levels of its first input end and the second input end. The fourth logic gate circuit U5 Circuit U5 outputs a preset low level because its first input terminal and second input terminal do not both receive the preset high level VCC1; the third logic gate circuit U3 outputs a preset high level VCC1 because its first input terminal is the preset high level VCC1 and the second input terminal is the preset low level; the second input terminal of the second logic gate circuit U15 is the preset high level VCC1, and the first input terminal is pulled down to the preset high level VCC1 by the first pull-down resistor R23 because the switch holding circuit is not turned on, and the preset high level VCC1 is output due to the different levels between the first input terminal and the second input terminal; the reset terminal of the first latch U6 is the preset low level, and the set terminal is pulled down to the preset low level by the first pull-down resistor R23, therefore, the preset low level is output from the first output terminal to the control terminal of the first-stage detection switch Q1, and the first-stage detection switch Q1 remains in the off state.

[0114] When the primary detection switch Q1 is turned on, if the insulation performance of the device under test 4 is normal or the damage is small, the primary comparison circuit U4 outputs a preset low level, the first input end of the first logic gate circuit U1 and the second end of the fourth logic gate circuit U5 are the preset low level, the second input end of the first logic gate circuit U1 and the first input end of the fourth logic gate circuit U5 are the preset high level VCC1, then the first logic gate circuit U1 continues to output the preset high level VCC1 due to the different levels of its first input end and the second input end, the fourth logic gate circuit U5 outputs a preset low level because its first input end and the second input end do not both receive the preset high level VCC1; the third logic gate circuit U3 outputs a preset high level VCC1 because its first input end is the preset high level VCC1 and the second input end is the preset low level; after the preset time, after the primary switch circuit is disconnected, the primary detection switch Q1 is also turned off, no current passes through the device under test 4, the primary comparison circuit U4 keeps outputting the preset low level, and the third logic gate circuit U3 keeps outputting the preset high level VCC1.

[0115] It can be seen that no matter what the insulation performance of the device under test 4 is, or whether the primary detection switch Q1 is turned on, the third logic gate circuit U3 outputs the preset high level VCC1, so the second input terminal of the second logic gate circuit U15 is always the preset high level VCC1.

[0116] In addition, a second current limiting resistor R7 may be disposed between the second end of the switch holding circuit and the set end of the first latch U6.

[0117] As a preferred embodiment, the primary switch circuit further includes:

[0118] A fifth logic gate circuit U7, wherein the first input end is connected to the second end of the switch module S1, the second input end is disconnected from the alarm signal output of the secondary insulation detection circuit 2, and the output end is connected to the first end of the switch holding circuit, and is used for outputting a preset high level VCC1 when the first input end and / or the second input end thereof receives the preset high level VCC1, otherwise outputting a preset low level; the second alarm signal is the preset high level VCC1;

[0119] A second pull-down resistor R22, a first end of which is connected to the first input end of the fifth logic gate circuit U7, and a second end of which is grounded;

[0120] The switch module S1 is specifically used to be turned on when receiving a turn-on instruction, so that the first input terminal of the fifth logic gate circuit U7 is connected to a preset high level VCC1;

[0121] The switch holding circuit is specifically used to be turned on when the fifth logic gate circuit U7 outputs a preset high level VCC1, so that the set end of the first latch U6 is connected to the preset high level VCC1, and is turned off after a preset time.

[0122] In this embodiment, the first input end of the fifth logic gate circuit U7 is connected to the preset high level VCC1 when the switch module S1 is turned on, and the second input end is input with the preset high level VCC1 when the secondary insulation detection circuit 22 outputs the second alarm signal. Therefore, no matter whether the switch module S1 is turned on or the secondary insulation detection circuit 2 outputs the second alarm signal, the fifth logic gate circuit U7 can output the preset high level VCC1 to keep the switch circuit turned on.

[0123] It should be noted that the first input end of the fifth logic gate circuit U7 is connected to the preset high level VCC1 because the switch module S1 is turned on when it receives a turn-on instruction because insulation detection of the device under test 4 is required, and the second input end is connected to the preset high level VCC1 when receiving the second alarm signal because after the secondary insulation detection circuit 2 detects that the insulation performance of the device under test 4 is abnormal, the primary insulation detection circuit 1 is triggered again to perform insulation detection on the device under test 4. If the primary insulation detection circuit 1 also detects that the insulation performance of the device under test 4 is abnormal at this time, it also outputs the first alarm signal, so that the staff can be strongly reminded through the first alarm signal and the second alarm signal.

[0124] When the switch module S1 is not turned on, the first input terminal of the fifth logic gate circuit U7 is pulled down to a preset low level by the second pull-down resistor R22, thereby ensuring the stability of the first input terminal of the fifth logic gate circuit U7.

[0125] When the switch module S1 is pressed, the fifth logic gate circuit U7 outputs the preset high level VCC1 because its first input terminal is the preset high level VCC1, and the switch keeps the circuit turned on. During the preset time when the switch keeps the circuit turned on, the switch keeps the circuit outputting the preset high level VCC1 continuously. The first input terminal and the second input terminal of the second logic gate circuit U15 are both the preset high level VCC1, and the preset low level is output. The set terminal input of the first latch U6 is the preset high level VCC1, and the reset terminal input is the preset low level. At this time, the first output terminal Q of the first latch U6 is the preset high level VCC1, and the second output terminal Q̅ outputs the preset low level. At this time, the first-level detection switch Q1 is turned on, and after the device under test 4 is connected to the first-level detection voltage VCC, if the insulation performance of the device under test 4 is abnormal, the resistance value of the device under test 4 tends to 0, and the voltage difference between the two ends of the first-level sampling resistor R3 tends to the first-level detection voltage VCC, then V R3 =VCC. At this time, the output terminal of the primary sampling module U2 , VCC is sent to the IN+ pin of the first-level comparison module U4, the voltage of this pin is VCC>the voltage on IN-, the first-level preset voltage threshold Vref1, the first-level comparison module U4 outputs a preset high level VCC1, the first input end of the first logic gate circuit U1 and the second end of the fourth logic gate circuit U5 are the preset high level VCC1, the second input end of the first logic gate circuit U1 and the first input end of the fourth logic gate circuit U5 are the preset high level VCC1, then the first logic gate circuit U1 outputs a preset low level because the levels of its first input end and the second input end are the same, the fourth logic gate circuit U5 outputs a preset low level because of its first input end and the second input end. The first input terminal and the second input terminal both receive the preset high level VCC1 and output the preset high level VCC1; the third logic gate circuit U3 outputs the preset low level because its first input terminal is the preset low level and the second input terminal is the preset high level VCC1; at this time, because the preset time has not passed, the levels of the first input terminal and the second input terminal of the second logic gate circuit U15 are both the preset high level VCC1, the reset terminal of the first latch U6 is the preset low level, the set terminal is the preset high level VCC1, the first output terminal Q still outputs the preset high level VCC1, the first-level detection switch Q1 is still turned on, but because the first-level detection voltage VCC Small, will not cause damage to the device under test 4; after the preset time, the first switch circuit is disconnected, the second input end of the second logic gate circuit U15 is the preset high level VCC1, the first input end is the preset low level, the output is the preset high level VCC1, the reset end of the first latch U6 is the preset high level VCC1, the set end is the preset low level, then the first output end Q output is L, at this time, the first detection switch Q1 is disconnected, the device under test 4 is disconnected from the first detection voltage VCC, and the state is the same as the first insulation detection circuit 1 when it is only powered on. No current flows through the device under test 4 and the first sampling resistor R3, and the first comparison module outputs The preset low level causes the first input end of the first logic gate circuit U1 and the second end of the fourth logic gate circuit U5 to be the preset low level, the second input end of the first logic gate circuit U1 and the first input end of the fourth logic gate circuit U5 to be the preset high level VCC1, and the output of the first logic gate circuit U1 changes from the preset low level to the preset high level VCC1, that is, when the first-level switch circuit is disconnected, the first logic gate circuit U1 outputs a rising edge signal, triggering the alarm circuit 3 to alarm, and the output of the fourth logic gate circuit U5 changes from the preset high level VCC1 to the preset low level, and the third logic gate circuit U3 outputs the preset high level VCC1.

[0126] When the switch module S1 is pressed, the fifth logic gate circuit U7 outputs the preset high level VCC1 because its first input terminal is the preset high level VCC1, and the switch holding circuit is turned on. During the preset time of the switch holding circuit being turned on, the switch holding circuit continues to output the preset high level VCC1, and the set terminal of the first latch U6 and the first input terminal of the second logic gate circuit U15 are both set to the preset high level VCC1. The second logic gate circuit U15 outputs the preset low level to the reset terminal of the first latch U6 because its first input terminal is the preset high level VCC1 and the second input terminal is also the preset high level VCC1. At this time, the first output terminal of the first latch U6 can output the preset high level VCC1 to the control terminal of the first-level detection switch Q1, and the first-level detection switch Q1 is turned on. After a preset time, the switch holding circuit is disconnected, the set end of the first latch U6 and the first input end of the second logic gate circuit U15 are both pulled down to a preset low level by the first pull-down resistor R23, and the second logic gate circuit U15 outputs a preset high level VCC1 to the reset end of the first latch U6, so that the first latch U6 outputs a preset low level to the control end of the first-level detection switch Q1, and the first-level detection switch Q1 is disconnected.

[0127] Based on this, not only the insulation performance of the device under test 4 can be tested, but also the primary detection switch Q1 can be turned off in time after the test is completed to protect the device under test 4.

[0128] It should be noted that the switch module S1 in the present application is a non-holding switch, which will be disconnected after a preset time after being turned on. The switch holding circuit includes a single-pole single-throw switch U16 and an RC charge and discharge circuit. The S end of the single-pole single-throw switch U16 is connected to the output end of the fifth logic gate circuit U7, and the D end is the second end of the switch holding circuit, which is connected to the set end of the first latch U6. Its on and off are controlled by the enable pin EN. When EN is at a high level, pin S and pin D are connected, that is, the switch holding circuit is turned on. When EN is at a low level, pin S and pin D are disconnected, that is, the switch holding circuit is turned off; the RC charge and discharge circuit includes a charge and discharge capacitor C1 and a charge and discharge resistor R21, The first end of the charge and discharge capacitor C1 is connected to the output end of the fifth logic gate circuit U7, and the second end is connected to the first end of the charge and discharge resistor R21 and the second end of the single-pole single-throw switch U16. The second end of the charge and discharge resistor R21 is grounded. At the moment when the switch module S1S1 is turned on, the charge and discharge capacitor C1 is charged to a preset high level VCC1, the EN end of the single-pole single-throw switch U16 is at a high level, the switch keeps the circuit turned on, and then the charge and discharge capacitor C1 starts to discharge. After a preset time, the charge and discharge capacitor C1 is discharged, the EN end of the single-pole single-throw switch U16 is at a low level, and the switch keeps the circuit turned off. The preset time can be set according to the parameters of the charge-discharge capacitor C1 and the charge-discharge resistor R21, that is, after the switch module S1 is turned on and the preset time 2τ=2×R×C seconds has passed, the voltage at the second end of the charge-discharge capacitor C1 will reach 0V, that is, the discharge of the charge-discharge capacitor C1 is completed, and the EN end of the single-pole single-throw switch U16 becomes a low level, where R is the resistance of the charge-discharge resistor R21, and C is the capacitance of the charge-discharge capacitor C1. Please refer to Figure 5 and Figure 6 , Figure 5 A simulation circuit diagram of an RC charging and discharging circuit provided by the present invention, Figure 6 A simulation result diagram of an RC charging and discharging circuit provided by the present invention is shown in FIG. Figure 5 In the figure, V simulates the preset high level VCC1 in the circuit of the present invention, which is set to 5V, the resistor R is the charge and discharge resistor R21 in the present application, which is set to 4.7kΩ, and the capacitor C is the charge and discharge capacitor C1 in the present application, which is set to 1uF. According to the calculation formula of time τ, 2τ=2×4.7×1000Ω×1×10 -6 F=9.4ms. According to the simulation results in the figure, it can be seen that at 9.4ms, the voltage at the Vc terminal is about 0.7V, which is the low level required by the EN terminal of the single-pole single-throw switch U16. According to the simulation results, the present invention can adjust the value of the charge and discharge capacitor C1 and the charge and discharge resistor R21 according to the actual required time and thus adjust the value of the preset time 2τ.

[0129] It should also be noted that a third current limiting resistor R6 can be further provided between the second end of the switch module S1 and the first input end of the fifth logic gate circuit U7 to raise the level of the first input end of the fifth logic gate circuit U7 to a preset high level VCC1 when the switch module S1 is turned on.

[0130] As a preferred embodiment, the first latch U6 is further used to output a preset low level from its second output terminal when its reset terminal receives a preset low level and its set terminal receives a preset high level VCC1, and to output a preset high level VCC1 from its second output terminal when its reset terminal receives a preset high level VCC1 and its set terminal receives a preset low level;

[0131] The secondary insulation detection circuit 2 comprises:

[0132] A secondary switch circuit, wherein the first end is connected to a preset high level VCC1, the second input end is connected to the trigger signal output end of the primary insulation detection circuit 1, the third input end is connected to the second output end of the first latch U6, the fourth input end is connected to the output end of the secondary current detection circuit, and the output end is connected to the control end of the secondary detection switch Q2, and is used for receiving a trigger signal and the second output end of the first latch U6 is changed from a preset low level to a preset high level VCC1, and the secondary current detection circuit outputs a preset low level, outputting a preset high level VCC1 to the control end of the secondary detection switch Q2, otherwise outputting a preset low level to the control end of the secondary detection switch Q2;

[0133] A secondary detection switch Q2, a first end of which is connected to a first end of a secondary current detection circuit, and a second end of which is connected to a device under test 4, is used to be turned on when its control end is connected to a preset high level VCC1, and to connect the device under test 4 to the secondary detection voltage, and to be turned off when its control end is connected to a preset low level;

[0134] A secondary current detection circuit, the second end of which is connected to the first end of the secondary detection switch Q2, and the alarm signal output end is connected to the alarm circuit 3, for detecting the secondary current flowing through the device under test 4, and outputting a second alarm signal when it is detected that the secondary current is greater than the secondary preset minimum current;

[0135] The secondary current is negatively correlated with the secondary impedance, and the secondary preset minimum current is a current threshold value set based on the secondary preset minimum impedance.

[0136] Please refer to Figure 3 , Figure 3A structural schematic diagram of a secondary insulation detection circuit provided by the present invention. In this embodiment, when the switch module S1 is not turned on, and only the primary insulation detection circuit 1 and the secondary insulation detection circuit 2 are powered on, the switch holding circuit is also not turned on, the set end of the first latch U6 is a preset low level, the reset end is a preset high level VCC1, and the second output end outputs a preset high level VCC1; after the switch module S1 is turned on and the switch holding circuit is also turned on, the reset end of the first latch U6 is a preset low level, the set end is a preset high level VCC1, and the output of the second output end changes from the preset high level VCC1 to the preset low level, that is, a falling edge signal is output; after a preset time has passed and the switch holding circuit is turned off, the reset end of the first latch U6 is a preset high level VCC1, the set end is a preset low level, and the output of the second output end changes from the preset low level to the preset high level VCC1, that is, a rising edge signal is output.

[0137] If the secondary insulation detection circuit 2 is only powered on and the primary insulation detection circuit 1 does not output a trigger signal, the secondary switch circuit outputs a preset low level to the control end of the secondary detection switch Q2, the secondary detection switch Q2 is turned off, and the secondary detection voltage is not connected between the device under test 4, and the secondary current detection circuit will not output a second alarm signal.

[0138] When the secondary switch circuit receives the trigger signal and the rising edge signal output by the second output terminal of the first latch U6, the secondary current detection circuit outputs the preset high level VCC1 to the control end of the secondary detection switch Q2 when the preset low level is output, and the secondary detection switch Q2 is turned on. The device under test 4 is connected to the secondary detection voltage, and the secondary current detection circuit collects the secondary current flowing through the device under test 4. When it is detected that the secondary current is greater than the secondary preset minimum current, the second alarm signal is output to prompt that the insulation performance of the device under test 4 is abnormal.

[0139] As a preferred embodiment, the secondary current detection circuit includes:

[0140] A current transformer PT1, with a primary side PT1A connected between a secondary detection voltage and a first end of a secondary detection switch Q2, and a secondary side connected to a first end and a second end of a secondary sampling resistor R9, for sensing a secondary current flowing through the device under test 4;

[0141] The secondary sampling resistor R9 is used to collect the current of the secondary side PT1B of the current transformer PT1;

[0142] A secondary sampling module U12, a first input end connected to a first end of a secondary sampling resistor R9, a second input end connected to a second end of the secondary sampling resistor R9, for collecting voltages across the secondary sampling resistor R9;

[0143] A secondary comparison module U11, wherein the first input terminal is connected to the output terminal of the secondary sampling module U12, and the second input terminal is connected to the secondary preset voltage threshold Vref2, and is used to output a preset high level VCC1 when the voltage across the secondary sampling resistor R9 is greater than the secondary preset voltage threshold Vref2, and output a preset low level when the voltage across the secondary sampling resistor R9 is not greater than the secondary preset voltage threshold Vref2; the secondary preset voltage threshold Vref2 is a voltage threshold set based on the resistance value of the secondary sampling resistor R9 and the secondary preset minimum current;

[0144] The first trigger U10, whose clock signal input terminal is connected to the output terminal of the secondary comparison module U11, and whose output terminal is connected to the alarm circuit 3, is used to output a preset high level VCC1 when detecting that the output of the secondary comparison module U11 changes from a preset low level to a preset high level VCC1, otherwise output a preset low level;

[0145] The alarm circuit 3 is specifically used to generate an alarm when it is detected that the output of the first trigger changes from a preset low level to a preset high level VCC1.

[0146] In this embodiment, the primary side PT1A of the current transformer PT1 can sense the current in the circuit between the secondary detection switch Q2 and the device under test 4, that is, the secondary current flowing through the device under test 4. The secondary sampling resistor R9 is connected in parallel between the two ends of the secondary side PTIB of the current transformer PT1. Therefore, the current flowing through the secondary sampling resistor R9 is the secondary current. Since the voltage across the two ends of the secondary sampling resistor R9 is positively correlated with the current flowing through the secondary sampling resistor R9, such as the voltage across the two ends of the secondary sampling resistor R9 is the product of the current flowing through the secondary sampling resistor R9 and the resistance value of the secondary sampling resistor R9, after the secondary sampling module U12 collects the voltage across the two ends of the secondary sampling resistor R9, the secondary ratio The comparison module U11 compares the voltage across the secondary sampling resistor R9 with the secondary preset voltage threshold Vref2. When the voltage across the secondary sampling resistor R9 is greater than the secondary preset voltage threshold Vref2, the secondary current flowing through the device under test 4 is greater than the secondary preset minimum current. At this time, the secondary comparison module U11 outputs a preset high level VCC1; when the voltage across the secondary sampling resistor R9 is not greater than the secondary preset voltage threshold Vref2, the secondary current flowing through the device under test 4 is not greater than the secondary preset minimum current. At this time, the secondary comparison module U11 outputs a preset low level, and the preset voltage threshold can be the product of the resistance value of the secondary sampling resistor R9 and the secondary preset minimum current. Of course, the turns ratio of the primary side PT1A and the secondary side PT1B of the current transformer PT1 can be changed, and the secondary preset voltage threshold Vref2 can also be adjusted according to the turns ratio of the current transformer PT1.

[0147] When the insulation performance of the device under test 4 is abnormal, the output end of the secondary comparison module U11 is converted from a preset low level to a preset high level VCC1, that is, a rising edge signal is output. After receiving the rising edge signal, the output end of the first trigger is also converted from a preset low level to a preset high level VCC1, thereby outputting a second alarm signal and causing the alarm circuit 3 to alarm.

[0148] When the insulation performance of the device under test 4 is normal, or the secondary insulation detection circuit 2 is only powered on, the output end of the secondary comparison module U11 continuously outputs a preset low level, and the first trigger also continuously outputs a preset low level.

[0149] In addition, a resistor R11 may be provided between RG+ and RG- of the secondary sampling module U12. The second input terminal of the secondary comparison module U11 may be connected to the secondary preset voltage threshold Vref2 through the fourth current limiting resistor R14. The output terminal of the secondary comparison module U11 may also be connected to a second pull-up resistor R15, and the second terminal of the second pull-up resistor R15 may be connected to a preset high level.

[0150] As a preferred embodiment, the secondary switch circuit includes:

[0151] The second trigger U8, whose clock signal input terminal is connected to the trigger signal output terminal of the primary insulation detection circuit 1, and whose output terminal is connected to the trigger terminal of the third trigger, is used to output a preset low level when the output of the first logic gate circuit U1 changes from a preset low level to a preset high level VCC1, otherwise output a preset high level VCC1;

[0152] The third trigger U9, the clock signal input end is connected to the second output end of the first latch U6, the reset end is connected to the output end of the secondary current detection circuit, and the output end is connected to the control end of the secondary detection switch Q2, and is used for outputting a preset high level VCC1 in the second trigger, the output of the second output end of the first latch U6 is changed from a preset low level to a preset high level VCC1, and when the secondary current detection circuit does not detect that the secondary current is greater than the secondary preset minimum current, it outputs a preset high level VCC1, otherwise it outputs a preset low level.

[0153] In this embodiment, when the first logic gate circuit U1 continuously outputs a preset high level VCC1, continuously outputs a preset low level, or outputs a falling edge signal, they are all trigger signals, that is, when the first logic gate circuit U1 does not output a rising edge signal, it is an output trigger signal. However, the problem of sequential detection between the primary insulation detection circuit 1 and the secondary insulation detection circuit 2 is also taken into consideration. The second trigger U8 receives the trigger signal, and the third trigger U9 receives the rising edge signal output by the second output end of the first latch U6. The second detection switch Q2 will be controlled to turn on, that is, the secondary insulation detection circuit 2 will perform insulation detection at this time.

[0154] Specifically, when the primary insulation detection circuit 1 and the secondary insulation detection circuit 2 are only powered on, and the switch module S1 and the primary detection switch Q1 are not turned on, the first logic gate circuit U1 continues to output the preset high level VCC1, and the second trigger U8 therefore outputs the preset high level VCC1, but because the second output end of the first latch U6 outputs the preset high level VCC1 at this time, which is not a rising edge signal, the secondary current detection circuit also outputs a preset low level, therefore, the third trigger U9 outputs a preset low level to the control end of the secondary detection switch Q2, and the secondary detection switch Q2 is not turned on. Specifically, when the secondary insulation detection circuit 2 is only powered on, that is, the plug P1 connected to the primary PT1A of the current transformer PT1 is connected to the secondary detection voltage, but the secondary detection switch Q2 is not turned on, the primary PT1A detection current of the current transformer PT1 is I PT1A =0A, the output current of the secondary side PT1B is also I PT1B =0A, at this time, the voltage across the secondary sampling resistor R9 is 0V, and the output of the secondary sampling module U12 is At this time, the voltage of the IN+ pin of the secondary comparison module U11 is 0V<the secondary preset voltage threshold Vref2 on the IN- pin, the output of the secondary comparison module U11 is the preset low level, the CLR of the third trigger U9 is the preset low level, and the CLK has no level change, so the output of the third trigger U9 does not change and continues to maintain the initial state, that is, outputs the preset low level, and the secondary detection switch Q2 is not turned on. The first trigger U10 also maintains the initial state unchanged and does not output the second alarm signal.

[0155] When the switch module S1 is pressed, the fifth logic gate circuit U7 outputs the preset high level VCC1 because its first input terminal is the preset high level VCC1, and the switch keeps the circuit turned on. During the preset time when the switch keeps the circuit turned on, the first-level insulation detection circuit 1 does not detect the insulation performance abnormality of the device under test 4, that is, when the first logic gate circuit U1 continues to output the preset high level VCC1, the second trigger U8 therefore outputs the preset high level VCC1, but because the second output terminal of the first latch U6 outputs the preset low level at this time, which is not a rising edge signal, the secondary current detection circuit also outputs the preset low level. Therefore, the third trigger U9 outputs the preset low level to the control terminal of the secondary detection switch Q2, and the secondary detection switch Q2 is not turned on; after the preset time, when the switch keeps the circuit turned off, the first logic gate circuit U1 continues to output the preset high level VCC1, and the second trigger outputs the preset high level VCC1. At this time, the first latch U6 The second output end of the register U6 outputs a rising edge signal, and the secondary current detection circuit also outputs a preset low level. Therefore, the third trigger U9 outputs a preset high level VCC1 to the control end of the secondary detection switch Q2, the secondary detection switch Q2 is turned on, the device under test 4 is connected to the secondary detection voltage, and the secondary insulation detection circuit 2 performs insulation detection on the device under test 4; if the insulation performance of the device under test 4 is normal after the secondary detection voltage is connected, the secondary comparison module U11 still outputs a preset low level; and if the insulation performance of the device under test 4 is abnormal after the secondary detection voltage is connected, the secondary comparison module U11 outputs a preset high level VCC1, and the reset end of the third trigger is the preset high level VCC1. At this time, the third trigger outputs a preset low level, and the secondary detection switch Q2 is turned off, that is, the device under test 4 can be disconnected from the secondary detection voltage instantly after the insulation abnormality of the device under test 4 is detected, so as to avoid the device under test 4 being damaged by a large voltage shock.

[0156] In the above process, the level state of the output end of the first logic gate circuit U1 changes from the preset high level VCC1 when the switch module S1 is first powered on and not pressed, to the preset low level when the switch module S1 is pressed and the insulation performance of the tested device 4 is abnormal and faulty, and then changes to the preset high level VCC1 after the first-level detection switch Q1 is disconnected, with a falling edge and a rising edge. Since the clock signal input end of the second trigger U8 is connected to the output end of the first logic gate circuit U1, when the output end of the first logic gate circuit U1 outputs a rising edge, the clock signal input end of the second trigger U8 will also have a rising edge, and the output of the second trigger U8 will change, Q output is the preset high level VCC1, and Q̅ output connected to the third trigger U9 is the preset low level. At the same time, the second output end Q̅ of the first latch U6 changes from the preset high level VCC1 when the switch module S1 is first powered on and not pressed, to the preset low level after the switch module S1 is pressed, and then changes to the preset high level VCC1 after the first-level detection switch Q1 is disconnected, with 1 rising edge. At this time, the clock signal input terminal of the third trigger U9 has a rising edge, but the output terminal Q̅ of the second trigger U8 also becomes a preset low level when the clock signal input terminal of the second trigger U8 has a rising edge, so the D input pin of the third trigger U9, that is, the trigger terminal, is the preset low level, and the output terminal Q of the third trigger U9 is still maintained at the preset low level, and the secondary detection switch Q2 is not turned on.

[0157] In the above process, the level state of pin 3 of U1 changes from H when the switch S1 is powered on but not pressed, to L when S1 is pressed to detect a fault, and then to H after Q1 is disconnected, with a falling edge and a rising edge. The fourth trigger U13 pin CLK of the alarm circuit 33 will be triggered by a rising edge, the Q̅ terminal output is L, and the first light-emitting diode D1 lights up to alarm.

[0158] When the primary insulation detection circuit 1 does not detect abnormal insulation performance of the device under test 4 and enters the detection process of the secondary insulation detection circuit 2, the output terminal Q of the third trigger U9 is a preset high level VCC1, and the output terminal Q of the first trigger U10 is a preset low level. When the insulation of the device under test 4 is damaged, the resistance of the device under test 4 approaches 0, and the current I on the primary side PT1A of the current transformer PT1 PT1A Can be as high as tens of A, the secondary output current I PT1B >1mA, at this time, the output end of the secondary sampling module U12 >Vref2, the output of the secondary comparison module U11 is the preset high level VCC1, the reset end of the third trigger U9 is the preset high level VCC1, the output end Q is the preset low level, and the secondary detection switch Q2 is closed. At the same time, the clock signal input end of the first trigger U10 changes from the preset low level to the preset high level VCC1, and there is a rising edge trigger. At this time, the output end Q of the first trigger U10 outputs the preset high level VCC1 and outputs the second alarm signal. In addition, the Q end of the first trigger U10 is connected to the second input end of the fifth logic gate circuit U7, which will start the primary insulation detection circuit 1. At this time, if the fault still exists, the primary insulation detection circuit 1 will also output the first alarm signal.

[0159] When the switch holds the circuit on, the primary insulation detection circuit 1 detects that the insulation performance of the device under test 4 is abnormal, that is, the first logic gate circuit U1 continues to output a preset low level, and the second trigger therefore outputs a preset high level VCC1. At this time, the second output end of the first latch U6 outputs a preset low level, not a rising edge signal, and the secondary current detection circuit also outputs a preset low level. Therefore, the third trigger outputs a preset low level to the control end of the secondary detection switch Q2, and the secondary detection switch Q2 is not turned on; after a preset time, when the switch holds the circuit off, the first logic gate circuit U1 outputs a rising edge signal, and the second trigger outputs a preset low level. Even if the second output end of the first latch U6 outputs a rising edge signal at this time, the secondary current detection circuit outputs a preset low level, the third trigger will also output a preset low level to the control end of the secondary detection switch Q2, and the secondary detection switch Q2 remains off, and the secondary insulation detection circuit 2 does not need to perform insulation detection on the device under test 4.

[0160] As a preferred embodiment, the secondary switch circuit further includes:

[0161] The first end is connected to the clock signal input end of the third trigger, and the second end is connected to the grounded charging capacitor C2.

[0162] Because the changes of the clock signal input terminals of the second trigger U8 and the third trigger U9 are synchronous, the change of the clock signal input terminal of the third trigger U9 should be made after the output of the second trigger U8 is transformed to ensure its reliability, so the charging capacitor C2 is added for a delay.

[0163] Please refer to Figure 4 , Figure 4 A schematic diagram of an alarm circuit provided by the present invention.

[0164] As a preferred embodiment, the alarm circuit 3 includes:

[0165] The fourth trigger U13, the clock signal input end is connected to the alarm signal output end of the primary insulation detection circuit 1, and the output end is connected to the first end of the first alarm module, and is used to output a preset low level when receiving the first alarm signal, otherwise output a preset high level VCC1; the preset high level VCC1 is opposite to the preset low level;

[0166] A first alarm module, the second end of which is connected to a preset high level VCC1, and is used to generate an alarm when the fourth trigger U13 outputs a preset low level;

[0167] The second alarm module is connected to the alarm signal output terminal of the secondary insulation detection circuit 2 and is used for giving an alarm when receiving the second alarm signal.

[0168] The fourth trigger U13 in this embodiment receives the first alarm signal outputted from the alarm signal output terminal of the primary insulation detection circuit 1, that is, when the output terminal of the first logic gate circuit U1 outputs a rising edge signal, the first terminal of the first alarm module is connected to a preset low level, so that the first alarm module alarms. Figure 4 It can be seen that the first alarm module in the present application can be a first light-emitting diode D1. The second end of the first light-emitting diode D1 is pulled up to a preset high level VCC1 or connected to a primary detection voltage VCC through a third pull-up resistor R4. After the first end of the first light-emitting diode D1 is connected to a preset low level, the first light-emitting diode D1 performs a light alarm. Of course, the present application does not limit this, and the first alarm module can also be a buzzer.

[0169] The second alarm module is connected to the alarm signal output terminal of the secondary insulation detection circuit 2, such as Figure 3 , which can be specifically connected to the output terminal of the first trigger U10, that is, Figure 3 Taking the second alarm module including the second light-emitting diode D2 as an example, the first end of the second light-emitting diode D2 is connected to the output end of the first trigger U10 through the fourth pull-up resistor R8, and the second end is grounded. That is, when the output end of the first trigger U10 outputs the second alarm signal as a high level, the second light-emitting diode D2 lights up to alarm. Of course, the present application does not limit this, and the second alarm module can also be a buzzer.

[0170] The present invention uses the following logic gate devices, and the switching logic of each logic gate device is described below.

[0171] In the following description: H: preset high level, voltage is VCC1; L: preset low level, voltage is 0V; ×: no fixed level state.

[0172] 1) Logic XOR gate device (first logic gate circuit U1 and second logic gate circuit U15)

[0173] In the present application, the first logic gate circuit U1 and the second logic gate circuit U15 use logic XOR gate devices, including two input terminals, and their output is H only when the level states of the two input terminals are inconsistent, and their output is L when the level states of the two input pins are consistent. The truth table is shown in Table 1.

[0174] Table 1 Truth table of logical XOR gate device

[0175]

[0176] 2) Logic NAND gate device (third logic gate circuit U3)

[0177] In the present application, the third logic gate circuit U3 uses a logic NAND gate device, and its output is L when each input terminal is H, and when one input terminal is L, the output is H. Its truth table is shown in Table 2.

[0178] Table 2 Truth table of logic NAND gate device

[0179]

[0180] 3) Logic AND gate device (fourth logic gate circuit U5)

[0181] In the present application, the fourth logic gate circuit U5 uses a logic AND gate device, which includes two input terminals, and its output is H when each input terminal is H, and L when one input terminal is L. Its truth table is shown in Table 3.

[0182] Table 3 Truth table of logic AND gate devices

[0183]

[0184] 4) Logic OR gate device (fifth logic gate circuit U7)

[0185] The fifth logic gate circuit U7 in the present application uses a logic OR gate device, including two input terminals, and its output is H when one of the input terminals is H, and its output is L when both input terminals are L. Its truth table is shown in Table 4.

[0186] Table 4 Logic OR gate device truth table

[0187]

[0188] 5) RS latch (first latch U6)

[0189] In the present invention, the first latch U6 uses an RS latch, which includes two input terminals, wherein the R input terminal is a reset terminal, H is valid, and the S input terminal is a set terminal, H is valid. When the reset terminal input is H, the first output terminal Q terminal is L, and the second output terminal Q̅ outputs H. When the set terminal input is H, the first output terminal outputs Q terminal H, and the second output terminal Q̅ outputs L. When the reset terminal and the set terminal input are both L, the two output pins remain unchanged, and the reset terminal and the set terminal cannot input H at the same time. Its truth table is shown in Table 5.

[0190] Table 5 RS latch truth table

[0191]

[0192] 6) D flip-flops (first flip-flop U10, second flip-flop U8, third flip-flop U9 and fourth flip-flop U13)

[0193] In the present application, the first trigger U10, the second trigger U8, the third trigger U9 and the fourth trigger U13 are selected as D triggers. The D trigger has 6 pins, among which SET is the set terminal. When the SET input is H, the output Q terminal is H, and the Q̅ output is L; CLR is the reset terminal. When CLR is H, the output Q terminal is L, and the Q̅ output is H; CLK is the clock signal input terminal. The D trigger selected in the present invention is a rising edge trigger, so when the CLK pin input level signal is L to H, at this moment, according to the input level signal of the D pin, the output pin changes. Its truth table is shown in Table 6.

[0194] Table 6 D flip-flop truth table

[0195]

[0196] It should be noted that the set end of the first trigger U10 is grounded through the first trigger pull-down resistor R16, the reset end is grounded through the second trigger pull-down resistor R17, and the trigger end is connected to the preset high level VCC1 through the fifth pull-up resistor R13, so that the first trigger U10 outputs a preset high level when the clock signal input end receives a rising edge signal; the set end of the second trigger U8 is grounded through the third trigger pull-down resistor R24, the reset end is grounded through the fourth trigger pull-down resistor R25, and the trigger end is connected to the preset high level VCC1 through the sixth pull-up resistor R10, so that The second trigger U8 outputs a preset low level when the clock signal input terminal receives a rising edge signal; the set end of the third trigger U9 is grounded through the fifth trigger pull-down resistor R12, and the reset end is connected to the output end of the secondary comparison module U11; the set end of the fourth trigger U13 is grounded through the sixth trigger pull-down resistor R20, the reset end is grounded through the seventh trigger pull-down resistor R19, and the trigger end is connected to the preset high level VCC1 through the seventh pull-up resistor R18, so that the fourth trigger U13 outputs a preset low level when the clock signal input terminal receives a rising edge signal.

[0197] The output initial states of the RS latch and the D flip-flop selected in the present invention are: Q is L, Q̅ is H.

[0198] Figure 7 The test timing diagram of the present invention is to detect the insulation fault-free state of the tested equipment after the switch module is pressed after power-on. Figure 8 The test timing diagram of the primary insulation detection circuit detecting the insulation fault state of the tested equipment after the switch module is pressed after power-on provided by the present invention, Fig. 9 The present invention provides a test timing diagram in which after the switch module is powered on and pressed, the upper insulation detection circuit detects that the insulation of the tested device is in a fault-free state, but the secondary insulation detection circuit detects that the insulation of the tested device is in a faulty state.

[0199] Figure 7 In the middle: the T1 stage is the timing when the switch module S1 is not pressed when the power is turned on, T1→T1+τ is the timing when the primary insulation detection circuit 1 does not detect the insulation abnormality of the device under test 4 after the switch module S1 is pressed, and the T1+τ→T2 stage is the timing when the primary insulation detection circuit 1 does not detect the insulation abnormality of the device under test 4, disconnects the primary detection switch Q1, triggers the detection of the secondary insulation detection circuit 2, and does not detect the insulation abnormality of the device under test 4.

[0200] Figure 8 In the middle: the T1 stage is the timing when the switch module S1 is not pressed when the power is turned on, T1→T1+τ is the timing when the primary insulation detection circuit 1 detects that the insulation performance of the device under test 4 is damaged after the switch module S1 is pressed, and T1+τ→T2 is the timing after the primary detection switch Q1 is disconnected.

[0201] In the above figure: stage T1 is the timing when the switch module S1 is not pressed when the power is turned on, T1→T1+τ is the timing when the primary insulation detection circuit 1 does not detect the insulation abnormality of the device under test 4 after the switch module S1 is pressed, T1+τ→T2 is the timing when the primary detection switch Q1 is disconnected after Q1 is disconnected, triggering the detection of the secondary insulation detection circuit 2, T2→T3 is the timing when the secondary insulation detection circuit 2 detects that the insulation performance of the device under test 4 is damaged, T3→T3+τ is the timing when the secondary detection switch Q2 is disconnected to trigger the primary insulation detection circuit 1 to perform insulation detection again, and T3+τ→T4 is the timing when the primary insulation detection circuit 1 detects the insulation abnormality of the device under test 4.

[0202] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0203] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An insulation detection device, characterized in that: include: A primary insulation detection circuit, wherein the first end is connected to a primary detection voltage, and the second end is connected to a device under test, and is used to control the device under test to access the primary detection voltage, and output a first alarm signal when it is detected that the primary impedance of the device under test is less than a first preset minimum impedance; and send a trigger signal to the secondary insulation detection circuit when it is detected that the primary impedance of the device under test is not less than the first preset minimum impedance; the primary detection voltage is less than a safety voltage; The secondary insulation detection circuit has a first control end connected to the trigger signal output end of the primary insulation detection device, a first end connected to the secondary detection voltage, and a second end connected to the device under test, and is used to control the device under test to connect to the secondary detection voltage when receiving the trigger signal, and output a second alarm signal and disconnect the device under test from the secondary detection voltage when detecting that the secondary impedance of the device under test is less than a second preset minimum impedance; The secondary detection voltage is greater than the safety voltage; The alarm circuit has a first input end connected to the alarm signal output end of the primary insulation detection circuit, and a second input end connected to the alarm signal output end of the secondary insulation detection circuit, and is used to give an alarm when receiving the first alarm signal and / or the second alarm signal; The primary impedance is the impedance of the device under test when receiving the primary detection voltage, and the secondary impedance is the impedance of the device under test when receiving the secondary detection voltage.

2. The insulation detection device according to claim 1, characterized in that: The primary insulation detection circuit comprises: A primary switch circuit, a first end of which is connected to a preset high level, and a second end of which is connected to a control end of a primary detection switch, and is used to be turned on based on a turn-on instruction to control the control end of the primary detection switch to be connected to the preset high level, and to be turned off after a preset time has passed to make the control end of the primary detection switch connected to the preset low level; The first-level detection switch, the second end of which is connected to the device under test, is used to be turned on when its control end is connected to the preset high level, and to connect the device under test to the first-level detection voltage, and to be turned off when its control end is connected to the preset low level; A primary current detection circuit, wherein the first end is connected to the primary detection voltage, the second end is connected to the first end of the primary detection switch, the alarm signal output end is connected to the alarm circuit, and the trigger signal output end is connected to the first control end of the secondary insulation detection circuit, and is used to detect the primary current flowing through the device under test, and output the first alarm signal when it is detected that the primary current is greater than the primary preset minimum current; and send a trigger signal to the secondary insulation detection circuit when it is detected that the primary current is not greater than the primary preset minimum current; The primary current is negatively correlated with the primary impedance, and the primary preset minimum current is a current threshold value set based on the primary preset minimum impedance.

3. The insulation detection device according to claim 2, characterized in that: The primary current detection circuit comprises: A primary sampling resistor, a first end of which is connected to the primary detection voltage, and a second end of which is connected to the first end of the primary detection switch; A primary sampling module, wherein a first input terminal is connected to a first terminal of the primary sampling resistor, and a second input terminal is connected to a second terminal of the primary sampling resistor, and is used to collect voltages across the primary sampling resistor; A primary comparison module, wherein the first input terminal is connected to the output terminal of the primary sampling module, and the second input terminal is connected to a primary preset voltage threshold, and is used to output the preset high level when the voltage across the primary sampling resistor is greater than the primary preset voltage threshold, and output a preset low level when the voltage across the primary sampling resistor is not greater than the primary preset voltage threshold; the primary preset voltage threshold is a voltage threshold set based on the resistance value of the primary sampling resistor and the primary preset minimum current; the preset low level is different from the preset high level; A first pull-up resistor, a first end of which is connected to the preset high level, and a second end of which is connected to the output end of the first-level comparison module; A first logic gate circuit, wherein the first input end is connected to the output end of the first-level comparison module, the second input end is connected to the preset high level, and the output end is connected to the input end of the alarm circuit and the control end of the second-level insulation detection circuit, and is used to output the preset high level when the levels of the first input end and the second input end are different, otherwise output the preset low level; The second control end of the secondary insulation detection circuit is connected to the primary detection switch, and is specifically used to control the device under test to access the secondary detection voltage when the first logic gate circuit outputs the preset high level and the primary switch circuit is disconnected, and when it is detected that the secondary impedance of the device under test is less than a second preset minimum impedance, output the second alarm signal and disconnect the connection between the device under test and the secondary detection voltage; The alarm circuit is specifically configured to generate an alarm when detecting that the output of the first logic gate circuit changes from the preset low level to the preset high level, and / or when receiving the second alarm signal.

4. The insulation detection device according to claim 3, characterized in that: The primary switch circuit comprises: a switch module, a first end of which is connected to the preset high level, and a second end of which is connected to the first end of the switch holding circuit, and is used to be turned on when receiving the turn-on instruction so that the first end of the switch holding circuit is connected to the preset high level, and to be turned off after the preset time has passed; The switch holding circuit, the second end of which is connected to the set end of the first latch, is used to be turned on when the switch module is turned on, so that the set end of the first latch is connected to the preset high level, and is turned off after the preset time has passed, so that the set end of the first latch is connected to the preset low level; The first latch, the reset end is connected to the output end of the second logic gate circuit, the first output end is connected to the control end of the primary detection switch, and is used to output the preset high level to the control end of the primary detection switch when the reset end of the first latch receives the preset low level and the set end receives the preset high level, and output the preset low level to the control end of the primary detection switch when the reset end of the first latch receives the preset high level and the set end receives the preset low level; The second logic gate circuit has a first input terminal connected to the second terminal of the switch holding circuit, and a second input terminal connected to the output terminal of the third logic gate circuit, and is used to output the preset high level when the levels of the first input terminal and the second input terminal are different, and otherwise output the preset low level; The third logic gate circuit has a first input end connected to the output end of the first logic gate circuit, and a second input end connected to the output end of the fourth logic gate circuit, and is configured to output the preset high level when the first input end and / or the second input end thereof receives the preset low level, and otherwise output the preset low level; The fourth logic gate circuit has a first input terminal connected to the preset high level, and a second input terminal connected to the output terminal of the first-level comparison module, and is configured to output the preset high level when both the first input terminal and the second input terminal receive the preset high level, and otherwise output the preset low level; A first pull-down resistor has a first end connected to the second end of the switch holding circuit and a second end grounded.

5. The insulation detection device according to claim 4, characterized in that: The primary switch circuit further includes: a fifth logic gate circuit, wherein the first input end is connected to the second end of the switch module, the second input end is disconnected from the alarm signal output of the secondary insulation detection circuit, and the output end is connected to the first end of the switch holding circuit, and is used for outputting the preset high level when the first input end and / or the second input end thereof receives the preset high level, otherwise outputting the preset low level; the second alarm signal is the preset high level; A second pull-down resistor, a first end of which is connected to the first input end of the fifth logic gate circuit, and a second end of which is grounded; The switch module is specifically configured to be turned on upon receiving the turn-on instruction, so that the first input terminal of the fifth logic gate circuit is connected to the preset high level, and to be turned off after the preset time has passed; The switch holding circuit is specifically used to be turned on when the fifth logic gate circuit outputs the preset high level, so that the set end of the first latch is connected to the preset high level, and is turned off after a preset time.

6. The insulation detection device according to claim 4, characterized in that: The first latch is further configured to output the preset low level from its second output terminal when its reset terminal receives the preset low level and its set terminal receives the preset high level, and to output the preset high level from its second output terminal when its reset terminal receives the preset high level and its set terminal receives the preset low level; The secondary insulation detection circuit comprises: A secondary switch circuit, wherein the first end is connected to the preset high level, the second input end is connected to the trigger signal output end of the primary insulation detection circuit, the third input end is connected to the second output end of the first latch, the fourth input end is connected to the output end of the secondary current detection circuit, and the output end is connected to the control end of the secondary detection switch, and is used for receiving the trigger signal and the second output end of the first latch is changed from the preset low level to the preset high level, and the secondary current detection circuit outputs the preset low level, outputting the preset high level to the control end of the secondary detection switch, otherwise outputting the preset low level to the control end of the secondary detection switch; The secondary detection switch has a first end connected to the first end of the secondary current detection circuit and a second end connected to the device under test, and is used to be turned on when its control end is connected to the preset high level and to connect the device under test to the secondary detection voltage, and to be turned off when its control end is connected to the preset low level; The secondary current detection circuit, the second end is connected to the first end of the secondary detection switch, the alarm signal output end is connected to the alarm circuit, and is used to detect the secondary current flowing through the device under test, and output the second alarm signal when it is detected that the secondary current is greater than the secondary preset minimum current; The secondary current is negatively correlated with the secondary impedance, and the secondary preset minimum current is a current threshold value set based on the secondary preset minimum impedance.

7. The insulation detection device according to claim 6, characterized in that: The secondary current detection circuit comprises: A current transformer, the primary side of which is connected between the secondary detection voltage and the first end of the secondary detection switch, and the secondary side is connected to the first end and the second end of the secondary sampling resistor, for sensing the secondary current flowing through the device under test; The secondary sampling resistor is used to collect the current of the secondary side of the current transformer; A secondary sampling module, wherein a first input end is connected to a first end of the secondary sampling resistor, and a second input end is connected to a second end of the secondary sampling resistor, and is used to collect voltages across the two ends of the secondary sampling resistor; A secondary comparison module, wherein the first input terminal is connected to the output terminal of the secondary sampling module, and the second input terminal is connected to the secondary preset voltage threshold, and is used to output the preset high level when the voltage across the secondary sampling resistor is greater than the secondary preset voltage threshold, and output the preset low level when the voltage across the secondary sampling resistor is not greater than the secondary preset voltage threshold; the secondary preset voltage threshold is a voltage threshold set based on the resistance value of the secondary sampling resistor and the secondary preset minimum current; A first trigger, whose clock signal input terminal is connected to the output terminal of the secondary comparison module, and whose output terminal is connected to the alarm circuit, is used to output the preset high level when detecting that the output of the secondary comparison module changes from the preset low level to the preset high level, otherwise output the preset low level; The alarm circuit is specifically configured to generate an alarm when detecting that the output of the first trigger changes from the preset low level to the preset high level.

8. The insulation detection device according to claim 6, characterized in that: The secondary switch circuit comprises: A second trigger, whose clock signal input terminal is connected to the trigger signal output terminal of the primary insulation detection circuit, and whose output terminal is connected to the trigger terminal of the third trigger, is used to output the preset low level when the output of the first logic gate circuit changes from the preset low level to the preset high level, otherwise output the preset high level; A third trigger, whose clock signal input terminal is connected to the second output terminal of the first latch, whose reset terminal is connected to the output terminal of the secondary current detection circuit, and whose output terminal is connected to the control terminal of the secondary detection switch, is used for outputting the preset high level when the second trigger outputs the preset high level, the output of the second output terminal of the first latch changes from the preset low level to the preset high level, and the secondary current detection circuit does not detect that the secondary current is greater than the secondary preset minimum current, outputting the preset high level, otherwise outputting the preset low level.

9. The insulation detection device according to claim 8, characterized in that: The secondary switch circuit also includes: The first end is connected to the clock signal input end of the third trigger, and the second end is connected to the charging capacitor connected to the ground.

10. The insulation detection device according to any one of claims 1 to 9, characterized in that: The alarm circuit comprises: A fourth trigger, wherein the clock signal input end is connected to the alarm signal output end of the primary insulation detection circuit, and the output end is connected to the first end of the first alarm module, and is used to output a preset low level when the first alarm signal is received, otherwise output a preset high level; the preset high level is opposite to the preset low level; The first alarm module, the second end of which is connected to the preset high level, is used to alarm when the fourth trigger outputs the preset low level; The second alarm module is connected to the alarm signal output terminal of the secondary insulation detection circuit and is used for giving an alarm when receiving the second alarm signal.

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