Insulation detection circuit, method and equipment

Abstract

The invention discloses an insulation detection circuit, method and device which can be used in the field of electronic circuits, the insulation detection circuit comprises a first switch, a second switch and a sampling branch, and the sampling branch comprises a divider resistor, a sampling resistor and a third switch; the sampling branch is connected with a positive power line through a first switch and connected with a negative power line through a second switch. The sampling branch is provided with a first part connected with the first earth impedance in parallel and a second part connected with the second earth impedance in parallel, the first part comprises at least one divider resistor and a sampling resistor, and the second part comprises at least one divider resistor; the third switch is connected in parallel with at least one divider resistor. Therefore, the sampling branch is connected only under the condition of insulation detection, the number of electronic components is small, the circuit structure is simpler, the size of insulation detection equipment can be effectively reduced, and the circuit cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to an insulation detection circuit, method and device. Background Art

[0002] With the rapid popularization of new energy vehicles, people are paying more and more attention to the safety of new energy vehicle charging piles. During the use of charging piles, their insulation is often affected by external factors and decreases. When the insulation decreases to a certain level, leakage current may be generated to the outside, thus causing electrical safety accidents.

[0003] At present, the insulation detection equipment commonly used is large in size. Therefore, how to reduce the size of the insulation detection equipment has become a problem that needs to be solved. Summary of the invention

[0004] Based on the above problems, the present application provides an insulation detection circuit, method and device, which can reduce the volume of the insulation detection device.

[0005] The embodiments of the present application disclose the following technical solutions:

[0006] In a first aspect, an embodiment of the present application provides an insulation detection circuit, the circuit comprising: a first switch, a second switch and a sampling branch, wherein the sampling branch comprises a voltage dividing resistor, a sampling resistor and a third switch;

[0007] The sampling branch is connected to the positive power line through the first switch, and is connected to the negative power line through the second switch;

[0008] The sampling branch comprises a first part connected in parallel with the first impedance to ground and a second part connected in parallel with the second impedance to ground, wherein the first part comprises at least one voltage-dividing resistor and a sampling resistor, and the second part comprises at least one voltage-dividing resistor;

[0009] The third switch is connected in parallel with the at least one voltage dividing resistor.

[0010] Optionally, the circuit further comprises: a controller; the controller is electrically connected to the third switch;

[0011] The controller is used to:

[0012] Controlling the opening and closing of the third switch.

[0013] Optionally, the controller is electrically connected to the first switch and the second switch; the controller is further configured to:

[0014] When performing insulation detection, the first switch and the second switch are closed, and a first voltage is output to obtain the first impedance to ground and the second impedance to ground.

[0015] Optionally, the first part of the sampling branch includes a first voltage-dividing resistor, a second voltage-dividing resistor and the sampling resistor; the second part of the sampling branch includes a third voltage-dividing resistor, a fourth voltage-dividing resistor and the third switch;

[0016] The first voltage-dividing resistor, the sampling resistor, the second voltage-dividing resistor, the third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the first switch and the second switch;

[0017] The third switch is connected in parallel to two ends of the third voltage-dividing resistor.

[0018] Optionally, the first voltage-dividing resistor, the second voltage-dividing resistor, the third voltage-dividing resistor, and the fourth voltage-dividing resistor have equal resistance values.

[0019] Optionally, a connection point between the first part and the second part in the sampling branch is grounded; and a connection point between the first impedance to ground and the second impedance to ground is grounded.

[0020] In a second aspect, an embodiment of the present application provides an insulation detection method, which is applied to the insulation detection circuit described in any implementation of the first aspect, and the method includes:

[0021] When performing insulation detection, closing the first switch and the second switch to output a first voltage;

[0022] When the third switch is disconnected, a first sampling voltage across the sampling resistor is obtained; when the third switch is closed, a second sampling voltage across the sampling resistor is obtained; and the first impedance to ground and the second impedance to ground are determined;

[0023] Based on the first impedance to ground and the second impedance to ground, an insulation state of the charging pile is determined.

[0024] Optionally, determining the insulation state of the charging pile based on the first impedance to ground and the second impedance to ground includes:

[0025] Acquiring a voltage value of a second voltage for charging;

[0026] If the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground are both greater than the first threshold, it is determined that the insulation state of the charging pile is normal, the first switch and the second switch are disconnected, and the second voltage is output.

[0027] Optionally, after acquiring the voltage value of the second voltage for charging, the method further includes:

[0028] If any one of the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground is greater than the first threshold and less than or equal to the second threshold, insulation alarm information is output; the first threshold is less than the second threshold.

[0029] Optionally, determining the insulation state of the charging pile based on the first impedance to ground and the second impedance to ground includes:

[0030] Acquiring a voltage value of a second voltage for charging;

[0031] If any one of the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground is less than or equal to a first threshold, it is determined that the insulation state of the charging pile is abnormal, and a first signal is output, wherein the first signal is used to control the disconnection of at least one of the positive output contactor and the negative output contactor.

[0032] Optionally, the first part of the sampling branch includes a first voltage-dividing resistor, a second voltage-dividing resistor and a sampling resistor; the second part of the sampling branch includes a third voltage-dividing resistor, a fourth voltage-dividing resistor and a third switch; the first voltage-dividing resistor, the sampling resistor, the second voltage-dividing resistor, the third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the first switch and the second switch; the third switch is connected in parallel to both ends of the third voltage-dividing resistor;

[0033] When the third switch is disconnected, obtaining a first sampled voltage across the sampling resistor; when the third switch is closed, obtaining a second sampled voltage across the sampling resistor; and determining the first impedance to ground and the second impedance to ground include:

[0034] When the third switch is disconnected, obtaining a first sampling voltage across the sampling resistor;

[0035] Determine a first voltage to ground across the first portion and a second voltage to ground across the second portion according to the first sampled voltage and the resistance value of the sampling resistor;

[0036] When the third switch is closed, obtaining a second sampling voltage across the sampling resistor;

[0037] Determine a third voltage to ground at both ends of the first part and a fourth voltage to ground at both ends of the second part according to the second sampled voltage and the resistance value of the sampling resistor;

[0038] The first impedance to ground and the second impedance to ground are determined according to the first voltage to ground, the second voltage to ground, the third voltage to ground, and the fourth voltage to ground.

[0039] The embodiment of the present application provides an insulation detection circuit, which includes a first switch, a second switch and a sampling branch, wherein the sampling branch includes a voltage-dividing resistor, a sampling resistor and a third switch; the sampling branch is connected to the positive power line through the first switch, and is connected to the negative power line through the second switch; the sampling branch has a first part connected in parallel with the first impedance to ground and a second part connected in parallel with the second impedance to ground, wherein the first part includes at least one voltage-dividing resistor and a sampling resistor, and the second part includes at least one voltage-dividing resistor; the third switch is connected in parallel with the at least one voltage-dividing resistor. As a result, the number of electronic components is small, the circuit structure is simpler, and the volume of the insulation detection equipment can be effectively reduced, and the circuit cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A structural diagram of a balanced bridge circuit provided in an embodiment of the present application;

[0042] Figure 2 A structural diagram of an insulation detection circuit provided in an embodiment of the present application;

[0043] Figure 3 Another insulation detection circuit structure diagram provided in an embodiment of the present application;

[0044] Figure 4 A structural diagram of another insulation detection circuit provided in an embodiment of the present application;

[0045] Figure 5 A flow chart of an insulation detection method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] The insulation detection circuit, method and device provided in the present application can be used in the field of electronic circuits. The above is only an example and does not limit the application field of the insulation detection circuit, method and device provided in the present application.

[0047] The terms "first", "second", "third" and "fourth" etc. in the specification, claims and drawings of this application are used to distinguish different objects rather than to limit a specific order.

[0048] In the embodiments of the present application, the words "as an example" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "as an example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "as an example" or "for example" is intended to present the relevant concepts in a specific way.

[0049] The terms used in the implementation section of this application are only used to explain the specific embodiments of this application and are not intended to limit this application.

[0050] As mentioned above, with the rapid popularization of electric equipment such as new energy vehicles, people are paying more and more attention to the safety of energy transmission. Take DC charging piles as an example. They are used outdoors for a long time. Affected by weather conditions such as high temperature, low temperature and rain, the insulation of the charging piles will decrease. When the insulation decreases to a certain level, leakage current may be generated. If someone uses such a charging pile, the leakage current will flow through the human body to the ground, threatening the user's personal safety and causing electrical safety accidents.

[0051] Therefore, before using the charging pile, its insulation must be tested, that is, the impedance of the transmission system to the ground must be tested to determine whether it can be used.

[0052] Take the insulation detection scheme using the balanced bridge method as an example, see Figure 1 , this figure is a balanced bridge circuit structure diagram provided in an embodiment of the present application, wherein DC+ is the positive pole of the charging pile power output, DC- is the negative pole of the charging pile power output; DC+_OUT is the positive pole of the charging gun, and DC-_OUT is the negative pole of the charging gun; r01 and r02 are sampling resistors; R01, R02, R03, R04, R05, R06, R07, and R08 are voltage-dividing resistors with the same resistance value; R+ is the impedance of the positive power line to ground, and R- is the impedance of the negative power line to ground; S01, S02, and S03 are switches; K01 is the positive output contactor of the charging pile, and K02 is the negative output contactor of the charging pile.

[0053] Since the charging pile usually needs to output a higher voltage during operation, the bridge arm of the balancing bridge needs to be able to withstand high voltage. For example, if the charging pile outputs a voltage of 1000V, the bridge arm of the balancing bridge needs to withstand a voltage of 1000V. As an example, if the switch S01 is closed, each voltage-dividing resistor connected to the circuit needs to be able to withstand a voltage of 334V. Due to limitations in resistor materials and other aspects, resistors cannot meet the requirements of high voltage and high power at the same time. Usually, in order for the bridge arm to withstand such a high voltage and the power of the resistor does not exceed the rated power, multiple voltage-dividing resistors with higher resistance values ​​need to be connected in series in the bridge arm. However, on the one hand, the large number of resistors required in the circuit leads to a large size of the PCB, which in turn leads to a large volume of the insulation detection equipment; on the other hand, the two-way high-precision sampling circuit used also makes the circuit cost and complexity high; on the other hand, the high resistance of the voltage-dividing resistor also leads to too small a current flowing through the bridge arm, and the noise floor error has a greater impact on the sampling current, which is not conducive to sampling and affects the accuracy of insulation detection.

[0054] Therefore, an embodiment of the present application provides an insulation detection circuit, which includes a first switch, a second switch and a sampling branch, wherein the sampling branch includes a voltage-dividing resistor, a sampling resistor and a third switch; the sampling branch is connected to the positive power line through the first switch and to the negative power line through the second switch; the sampling branch has a first part connected in parallel with the first impedance to ground and a second part connected in parallel with the second impedance to ground, wherein the first part includes at least one voltage-dividing resistor and a sampling resistor, and the second part includes at least one voltage-dividing resistor; the third switch is connected in parallel with the at least one voltage-dividing resistor.

[0055] It can be understood that the above-mentioned first impedance to ground is different from the second impedance to ground. When the first impedance to ground is the impedance to ground of the positive power line, the second impedance to ground is the impedance to ground of the negative power line; when the first impedance to ground is the impedance to ground of the negative power line, the second impedance to ground is the impedance to ground of the positive power line.

[0056] In the case of insulation detection, the first switch and the second switch are closed, and the DCDC outputs a first voltage to obtain the impedance to ground of the positive power line and the impedance to ground of the negative power line; then, the insulation state of the charging pile can be determined based on the impedance to ground of the positive power line and the impedance to ground of the negative power line. Therefore, the sampling branch is only connected when insulation detection is performed, the number of electronic components is small, the circuit structure is simpler, and the volume of the insulation detection equipment can be effectively reduced, and the circuit cost can be reduced.

[0057] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] See also Figure 2 , which is a structural diagram of an insulation detection circuit provided in an embodiment of the present application, and the circuit includes:

[0059] A first switch S1 , a second switch S2 and a sampling branch 300 .

[0060] The sampling branch 300 includes voltage divider resistors (such as R1, R2, R3 and R4), a sampling resistor r1 and a third switch S3. The sampling branch 300 is connected to the positive power line 100 through the first switch S1 and to the negative power line 200 through the second switch S2.

[0061] Specifically, one end of the positive power line 100 is the positive power output pole DC+ of the charging pile, and the other end is the positive pole DC+_OUT of the matching charging gun, and DC+_OUT is connected to the positive pole of the battery of the new energy vehicle; one end of the negative power line 200 is the negative power output pole DC- of the charging pile, and the other end is the negative pole DC-_OUT of the matching charging gun, and DC-_OUT is connected to the negative pole of the battery of the new energy vehicle.

[0062] The sampling branch 300 has a first part 301 connected in parallel with the ground impedance (first ground impedance) R+ of the positive power line 100 and a second part 302 connected in parallel with the ground impedance (second ground impedance) R- of the negative power line 200; wherein the first part 301 includes at least one voltage-dividing resistor and a sampling resistor r1, and the second part 302 includes at least one voltage-dividing resistor; the third switch is connected in parallel with the at least one voltage-dividing resistor; the connection point of the first part 301 and the second part 302 is grounded PE; the connection point of the ground impedance R+ of the positive power line 100 and the ground impedance R- of the negative power line 200 is grounded PE, thereby reducing the risk of electric shock to the user.

[0063] When performing insulation detection, the first switch S1 and the second switch S2 are closed, so that the sampling branch 300 is connected to the circuit and the first voltage is output. It can be understood that the first voltage is the voltage provided by the DCDC for insulation detection. For example, the first voltage U can be a 400V voltage provided by the DCDC. Thus, under the first voltage, the ground impedance R+ of the positive power line 100 and the ground impedance R- of the negative power line 200 can be detected by the sampling branch 300, and the insulation state of the charging pile can be determined based on R+ and R-.

[0064] In this embodiment, during the operation of the charging pile, the sampling branch can be cut out of the circuit by disconnecting at least one of the first switch S1 and the second switch S2. Thus, the first voltage U and the voltage used by the charging pile for charging do not affect each other. A smaller first voltage U (such as 400V) can be set for the insulation detection situation, so that the resistors in the sampling branch only need to withstand a smaller voltage, and the total resistance required by the sampling branch is lower. The number of resistors required in the sampling branch is small and the resistance is low, which can reduce the size of the PCB and promote the miniaturization of the insulation detection equipment, and increase the current flowing through the sampling branch, improve the reliability of the sampling results, and thus improve the accuracy of the insulation detection results.

[0065] Therefore, the embodiment of the present application provides an insulation detection circuit, which is connected to the sampling branch only when insulation detection is performed. The number of electronic components is small, the circuit structure is simpler, and the volume of the insulation detection equipment can be effectively reduced, thereby reducing the circuit cost.

[0066] See also Figure 3 , this figure is another insulation detection circuit structure diagram provided in an embodiment of the present application, which: a first switch S1, a second switch S2, a first voltage-dividing resistor R1, a second voltage-dividing resistor R2, a sampling resistor r1, a third voltage-dividing resistor R3, a fourth voltage-dividing resistor R4, and a third switch S3.

[0067] Among them, the first voltage-dividing resistor R1, the sampling resistor r1 and the second voltage-dividing resistor R2 are connected in series in sequence to form a first part 301 of the sampling branch 300; the third voltage-dividing resistor R3, the fourth voltage-dividing resistor R4 and the third switch S3 form a second part 302 of the sampling branch 300; the first voltage-dividing resistor R1, the sampling resistor r1, the second voltage-dividing resistor R2, the third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4 are connected in series between the first switch S1 and the second switch S2; the third switch S3 is connected in parallel to both ends of the third voltage-dividing resistor R3.

[0068] In an optional embodiment, the circuit further includes: a positive output contactor K1 and a negative output contactor K2.

[0069] The first voltage-dividing resistor R1 is connected to the positive power line 100 through the first switch S1, and the fourth voltage-dividing resistor R4 is connected to the negative power line 200 through the second switch S2; the positive power line 100 has a positive output contactor K1; the negative power line 200 has a negative output contactor K2.

[0070] The connection point of the second voltage-dividing resistor R2 and the third voltage-dividing resistor R3 is connected to the ground PE; the connection point of the ground impedance R+ of the positive power line 100 and the ground impedance R− of the negative power line 200 is connected to the ground PE.

[0071] In one embodiment, the resistance values ​​of the first voltage-dividing resistor R1, the second voltage-dividing resistor R2, the third voltage-dividing resistor R3 and the fourth voltage-dividing resistor R4 are equal, so that the voltages corresponding to the voltage-dividing resistors at the access point are the same, and R+ and R- can be calculated more simply, thereby improving calculation efficiency.

[0072] Optionally, the first switch S1, the second switch S2 and the third switch S3 may be controllable switches such as relays, transistors or MOS tubes; the sampling resistor r1 is not limited to the sampling type, for example, it may be a resistor or a current sampling device such as a current transformer.

[0073] In the case of insulation detection, a first voltage U is provided between the positive power line 100 and the negative power line 200, and the first switch S1, the second switch S2, the positive output contactor K1 and the negative output contactor K2 are first closed to collect the first sampled voltage U1 across the sampling resistor r1; then, the third switch S3 is also closed to collect the second sampled voltage U2 across the sampling resistor r1; finally, based on U1 and U2, two expressions of the voltage ratios between R+ and R- are calculated, which are respectively and Based on the resistance in the circuit when the third switch S3 is open and the resistance in the circuit when the third switch S3 is closed, two relationship equations between the voltage ratio between R+ and R- and the resistance in the circuit can be obtained:

[0074] Formula (1): And formula (2): Since U, U1, U2, R1, R2, R3, R4 and r1 are all known quantities, the values ​​of R+ and R- can be solved by combining equations (1) and (2).

[0075] Among them, (R1+R2) / / R+ in formula (1) and formula (2) represents the total resistance of R1 and R2 connected in series and then connected in parallel with R+; (R3+R4) / / R- in formula (1) represents the total resistance of R3 and R4 connected in series and then connected in parallel with R-; R4 / / R- in formula (2) represents the total resistance of R4 and R- in parallel.

[0076] Therefore, during the insulation detection process, the switch only needs to be closed twice to obtain the values ​​of R+ and R-. Fewer actions need to be performed, which can shorten the insulation detection time and effectively improve the insulation detection efficiency of the charging pile.

[0077] Specifically, see Figure 4 , which is another insulation detection circuit structure diagram provided in an embodiment of the present application, wherein the circuit also includes a controller. The controller is electrically connected to the third switch S3. Specifically, the controller and the third switch S3 may be connected by wire or wirelessly.

[0078] The controller is used to control the opening and closing of the third switch S3. When the controller controls S3 to be opened, the current flowing through the sampling branch can be calculated based on U1 and r1, and then combined with the resistance value of the voltage divider resistor, the sum of the voltages across R1 and R2 (i.e., the first voltage to ground) and the sum of the voltages across R3 and R4 (i.e., the second voltage to ground) can be calculated. Since R1 and R2 are connected in parallel to R+, and R3 and R4 are connected in parallel to R-, an expression for the ratio of the voltages across R+ to R- can be obtained based on the first voltage to ground and the second voltage to ground:

[0079] Based on the same principle, when the controller controls S3 to be closed, the current flowing through the sampling branch can be calculated based on U2 and r1, and then combined with the resistance value of the voltage divider resistor, the sum of the voltages across R1 and R2 (that is, the third voltage to ground) and the voltage across R4 (that is, the fourth voltage to ground) can be calculated. Then, based on the third voltage to ground and the fourth voltage to ground, another expression for the ratio of the voltages across R+ and R- can be obtained.

[0080] Based on the relationship between the voltage ratio between R+ and R- and the resistance in the circuit, the values ​​of R+ and R- can be solved by combining the two expressions for the voltage ratio between R+ and R-.

[0081] Optionally, the controller is also electrically connected to the first switch S1 and the second switch S2. Specifically, the controller and the third switch S3 may be wired or wirelessly connected. The controller is used to close the first switch S1 and the second switch S2 when performing insulation detection, and the DCDC terminal outputs a first voltage U to obtain a first impedance to ground R+ and a second impedance to ground R-.

[0082] The voltage required to be output when the charging pile is used for charging is recorded as the second voltage U0. If the ratio of the second voltage U0 to the ground impedance R+ of the positive power line 100 and the ratio of the second voltage U0 to the ground impedance R- of the negative power line 200 are both greater than the first threshold, the first switch S1 and the second switch S2 are disconnected, and the DCDC provides a second voltage between the positive power line 100 and the negative power line 200; the second voltage is greater than the first voltage provided by the DCDC. Among them, the first threshold can be set according to actual needs, for example, it can be set according to relevant requirements in the safety specifications. If the ratio of the second voltage U0 to the ground impedance R+ of the positive power line 100 and the ratio of the second voltage U0 to the ground impedance R- of the negative power line 200 are both greater than the first threshold, it can be considered that the insulation of the charging pile meets the safety requirements.

[0083] As an example, the second voltage U0 may be the charging voltage of the vehicle when the new energy vehicle is charged. If both U0 / R+ and U0 / R- are greater than the first threshold, for example, U0 / R+>100Ω / V and U0 / R->100Ω / V, it can be considered that the insulation of the charging pile meets the safety requirements. At this time, the first switch S1 and the second switch S2 are disconnected, so that the sampling branch 300 is disconnected from the circuit, and the second voltage U0 is provided between the positive power line 100 and the negative power line 200. For example, the second voltage U0 may be 1000V.

[0084] If any of the ratio of the second voltage U0 to the ground impedance R+ of the positive power line 100 and the ratio of the second voltage U0 to the ground impedance R- of the negative power line 200 is less than or equal to the first threshold, it can be considered that the insulation of the charging pile cannot meet the safety requirements and cannot be used. At this time, the positive output contactor K1 can be disconnected; or the negative output contactor K2 can be disconnected; or the positive output contactor K1 and the negative output contactor K2 can be disconnected, thereby disconnecting the connection between the charging pile and the charging gun, and charging is prohibited.

[0085] In one embodiment, when any one of the ratio of the second voltage U0 to the ground impedance R+ of the positive power line 100 and the ratio of the second voltage U0 to the ground impedance R- of the negative power line 200 is less than or equal to the first threshold, the first switch S1, the second switch S2, the positive output contactor K1 and the negative output contactor K2 can be disconnected, that is, the connection between the charging pile and the charging gun, and the connection between the charging pile and the sampling branch are disconnected.

[0086] See also Figure 5 , which is a flow chart of an insulation detection method provided in an embodiment of the present application, the method comprising:

[0087] S501: When performing insulation detection, close the first switch and the second switch to output a first voltage.

[0088] As an example, when performing insulation detection, the first switch S1 and the second switch S2 are closed, so that the sampling branch is connected between the positive power line 100 and the negative power line 200, and the positive output contactor K1 and the negative output contactor K2 are both disconnected, and only the insulation detection of the charging pile is performed without performing the charging task. A first voltage U is provided between the positive power line 100 and the negative power line 200, wherein the voltage value of the first voltage U can be preset according to actual needs, for example, the first voltage U can be 400V.

[0089] S502: When the third switch is open, obtain a first sampled voltage across the sampling resistor; when the third switch is closed, obtain a second sampled voltage across the sampling resistor to determine a first impedance to ground and a second impedance to ground.

[0090] Specifically, in this embodiment, the first part of the sampling branch includes a first voltage-dividing resistor R1, a second voltage-dividing resistor R2 and a sampling resistor r1; the second part of the sampling branch includes a third voltage-dividing resistor R3, a fourth voltage-dividing resistor R4 and a third switch S3; R1, r1, R2, R3 and R4 are connected in series between S1 and S2; S3 is connected in parallel across R3.

[0091] When S3 is disconnected, a first sampled voltage U1 across r1 is obtained; a first voltage to ground across the first part is determined according to the resistance values ​​of U1 and r1, and a second voltage to ground across the second part is determined.

[0092] Specifically, at this time, r1, R1, R2, R3 and R4 are all connected to the circuit, R1 and R2 are connected in parallel with the first impedance to ground R+, and R3 and R4 are connected in parallel with the second impedance to ground R-. The sum of the voltages across R1 and R2 (i.e., the first voltage to ground) can be expressed as The sum of the voltages across R3 and R4 (i.e., the second voltage to ground) can be expressed as

[0093] When S3 is closed, a second sampled voltage U2 across r1 is obtained; a third voltage to ground across the first part is determined according to the resistance values ​​of U2 and r1, and a fourth voltage to ground across the second part is determined.

[0094] Specifically, at this time, R3 is short-circuited, R1, R2, and R4 are connected to the circuit, R1 and R2 are connected in parallel with the first impedance to ground R+, and R4 is connected in parallel with the second impedance to ground R-. The sum of the voltages across R1 and R2 can be expressed as R3 is short-circuited, and the voltage across R4 can be expressed as

[0095]

[0096] A first impedance to ground and a second impedance to ground are determined according to the first voltage to ground, the second voltage to ground, the third voltage to ground and the fourth voltage to ground.

[0097] Specifically, when S3 is disconnected, R1 and R2 are connected in parallel across R+, R3 and R4 are connected in parallel across R-, and the ratio of the voltage across R+ to R- can be expressed as Based on the relationship between the voltage ratio between R+ and R- and the resistance in the circuit, we can get formula (1):

[0098]

[0099] When S3 is closed, R1 and R2 are connected in parallel across R+, and R4 is connected in parallel across R-. The ratio of the voltage across R+ to that across R- can be expressed as Based on the relationship between the voltage ratio between R+ and R- and the resistance in the circuit, we can get formula (2):

[0100] In summary, U, U1, U2, R1, R2, R3, R4 and r1 are all known quantities. By combining equations (1) and (2), we can solve for the values ​​of R+ and R-.

[0101] S503: Determine the insulation state of the charging pile based on the first impedance to ground and the second impedance to ground.

[0102] Specifically, first obtain the voltage value of the second voltage U0 used for charging. It can be understood that the vehicle end will issue a charging demand when charging is required, and then the charging pile can obtain the voltage value of the second voltage U0 according to the charging demand, and then calculate the ratio of the voltage value of the second voltage U0 to the comparison impedance. If the ratio U0 / R+ of the voltage value of the second voltage U0 to the first impedance to ground R+, and the ratio U0 / R- of the voltage value of the second voltage U0 to the second impedance to ground R- are both greater than the first threshold, it is determined that the insulation state of the charging pile is normal, the first switch S1 and the second switch S2 are disconnected, and the second voltage U0 can be output, that is, when it is determined that the insulation state of the charging pile is normal, the sampling branch is disconnected, and the second voltage U0 is output for charging the vehicle end. In an optional embodiment, the voltage value of the second voltage U0 can be greater than the voltage value of the first voltage U. For example, the second voltage U0 is 1000V and the first voltage U is 400V. Among them, the first threshold can be set according to actual needs, for example, it can be set according to relevant requirements in the safety specification. If the ratio of the second voltage U0 to the ground impedance R+ of the positive power line 100 and the ratio of the second voltage U0 to the ground impedance R- of the negative power line 200 are both greater than the first threshold, it can be considered that the insulation of the charging pile meets the safety requirements.

[0103] As an example, the first threshold may be 100Ω / V. If U0 / R+>100Ω / V and U0 / R->100Ω / V, it can be considered that the insulation of the charging pile meets the safety requirements. At this time, the first switch S1 and the second switch S2 may be disconnected, the second voltage U0 may be output, and the charging task may be performed.

[0104] If any one of the ratio U0 / R+ of the voltage value of the second voltage U0 to the first impedance to ground R+ and the ratio U0 / R- of the voltage value of the second voltage U0 to the second impedance to ground R- is greater than the first threshold value and less than or equal to the second threshold value, an insulation alarm message is output; wherein the first threshold value is less than the second threshold value. Specifically, similar to the first threshold value, the second threshold value can also be set according to actual needs, for example, it can be set according to relevant requirements in the safety specification. If any one of the ratio of the second voltage U0 to the impedance to ground R+ of the positive power line 100 and the ratio of the second voltage U0 to the impedance to ground R- of the negative power line 200 is greater than the first threshold value and less than or equal to the second threshold value, it can be considered that although the insulation of the charging pile meets the safety requirements, it has dropped to within the range of the safety red line.

[0105] As an example, the second threshold value may be 500Ω / V. When both U0 / R+ and U0 / R- are greater than the first threshold value, if any one of U0 / R+ and U0 / R- is less than the second threshold value, it can be considered that the insulation performance of the energy transmission device has decreased and is within the safety red line. At this time, the insulation alarm information can be output to prompt the user to avoid using it as much as possible. The alarm information may be a flashing indicator light or a buzzer sounding.

[0106] If any one of the ratio U0 / R+ of the voltage value of the second voltage U0 to the first impedance to ground R+ and the ratio U0 / R- of the voltage value of the second voltage U0 to the second impedance to ground R- is less than or equal to the first threshold value, it is determined that the insulation state of the charging pile is abnormal, and a first signal is output, wherein the first signal is used to control the disconnection of the positive output contactor K1 and / or the negative output contactor K2.

[0107] As an example, the first threshold value may be 100Ω / V. If any one of U0 / R+ and U0 / R- is less than or equal to 100Ω / V, it can be considered that the insulation of the charging pile cannot meet the safety requirements. At this time, the positive output contactor K1 can be disconnected, or the negative output contactor K2 can be disconnected, or the positive output contactor K1 and the negative output contactor K2 can be disconnected to disconnect the charging circuit and prohibit charging, thereby avoiding electric shock accidents. Preferably, in this case, the first switch S1, the second switch S2, the positive output contactor K1 and the negative output contactor K2 can be disconnected at the same time, that is, the connection between the energy transmission device and the electrical appliance and the sampling branch is disconnected, thereby ensuring the safety of electricity use.

[0108] Therefore, in the embodiment of the present application, the sampling branch is connected only when insulation detection is performed, the number of electronic components is small, the circuit structure is simpler, and the volume of the insulation detection equipment can be effectively reduced, reducing the circuit cost.

[0109] In addition, the present application also provides an insulation detection device, which includes the insulation detection circuit provided by any of the above embodiments.

[0110] It should be noted that each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. The device embodiment described above is merely schematic, in which the unit described as a separate component may or may not be physically separated, and the component prompted as a unit may or may not be a physical unit, that is, it may be located in one place, or it may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative work.

[0111] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An insulation detection circuit, characterized in that: The circuit comprises: a first switch, a second switch and a sampling branch, wherein the sampling branch comprises a voltage dividing resistor, a sampling resistor and a third switch; The sampling branch is connected to the positive power line through the first switch, and is connected to the negative power line through the second switch; The sampling branch comprises a first part connected in parallel with the first impedance to ground and a second part connected in parallel with the second impedance to ground, wherein the first part comprises at least one voltage-dividing resistor and a sampling resistor, and the second part comprises at least one voltage-dividing resistor; The third switch is connected in parallel with the at least one voltage dividing resistor.

2. The circuit according to claim 1, characterized in that The circuit further comprises: a controller; the controller is electrically connected to the third switch; The controller is used to: Controlling the opening and closing of the third switch.

3. The circuit according to claim 2, characterized in that The controller is electrically connected to the first switch and the second switch; the controller is also used for: When performing insulation detection, the first switch and the second switch are closed, and a first voltage is output to obtain the first impedance to ground and the second impedance to ground.

4. The circuit according to any one of claims 1 to 3, characterized in that: The first part of the sampling branch includes a first voltage-dividing resistor, a second voltage-dividing resistor and the sampling resistor; the second part of the sampling branch includes a third voltage-dividing resistor, a fourth voltage-dividing resistor and the third switch; The first voltage-dividing resistor, the sampling resistor, the second voltage-dividing resistor, the third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the first switch and the second switch; The third switch is connected in parallel to two ends of the third voltage-dividing resistor.

5. The circuit according to claim 4, characterized in that The resistance values ​​of the first voltage-dividing resistor, the second voltage-dividing resistor, the third voltage-dividing resistor and the fourth voltage-dividing resistor are equal.

6. The circuit according to claim 1, characterized in that The connection point between the first part and the second part in the sampling branch is grounded; the connection point between the first impedance to ground and the second impedance to ground is grounded.

7. An insulation detection method, characterized in that: The method is applied to the insulation detection circuit described in any one of claims 1 to 6, and the method comprises: When performing insulation detection, closing the first switch and the second switch to output a first voltage; When the third switch is disconnected, a first sampling voltage across the sampling resistor is obtained; when the third switch is closed, a second sampling voltage across the sampling resistor is obtained; and the first impedance to ground and the second impedance to ground are determined; Based on the first impedance to ground and the second impedance to ground, the insulation state of the charging pile is obtained.

8. The method according to claim 7, characterized in that The step of determining the insulation state of the charging pile based on the first impedance to ground and the second impedance to ground includes: Acquiring a voltage value of a second voltage for charging; If the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground are both greater than the first threshold, it is determined that the insulation state of the charging pile is normal, and the first switch and the second switch are disconnected.

9. The method according to claim 8, characterized in that After acquiring the voltage value of the second voltage for charging, the method further includes: If any one of the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground is greater than the first threshold and less than or equal to the second threshold, insulation alarm information is output; the first threshold is less than the second threshold.

10. The method according to claim 7, characterized in that The step of determining the insulation state of the charging pile based on the first impedance to ground and the second impedance to ground includes: Acquiring a voltage value of a second voltage for charging; If any one of the ratio of the voltage value of the second voltage to the first impedance to ground and the ratio of the voltage value of the second voltage to the second impedance to ground is less than or equal to a first threshold, it is determined that the insulation state of the charging pile is abnormal, and a first signal is output, wherein the first signal is used to control the disconnection of at least one of the positive output contactor and the negative output contactor.

11. The method according to claim 7, characterized in that The first part of the sampling branch includes a first voltage-dividing resistor, a second voltage-dividing resistor and a sampling resistor; the second part of the sampling branch includes a third voltage-dividing resistor, a fourth voltage-dividing resistor and a third switch; the first voltage-dividing resistor, the sampling resistor, the second voltage-dividing resistor, the third voltage-dividing resistor and the fourth voltage-dividing resistor are connected in series between the first switch and the second switch; the third switch is connected in parallel to both ends of the third voltage-dividing resistor; acquiring a first sampling voltage across the sampling resistor when the third switch is disconnected; When the third switch is closed, obtaining a second sampling voltage across the sampling resistor; To determine the first impedance to ground and the second impedance to ground, comprising: When the third switch is disconnected, obtaining a first sampling voltage across the sampling resistor; Determine a first voltage to ground across the first portion and a second voltage to ground across the second portion according to the first sampled voltage and the resistance value of the sampling resistor; When the third switch is closed, obtaining a second sampling voltage across the sampling resistor; Determine a third voltage to ground at both ends of the first part and a fourth voltage to ground at both ends of the second part according to the second sampled voltage and the resistance value of the sampling resistor; The first impedance to ground and the second impedance to ground are determined according to the first voltage to ground, the second voltage to ground, the third voltage to ground, and the fourth voltage to ground.

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