Vehicle-mounted charger and fault detection method for low-voltage battery of vehicle-mounted charger

Abstract

The invention discloses a vehicle-mounted charger and a fault detection method of a low-voltage battery thereof, the vehicle-mounted charger comprises a high-voltage side and a low-voltage side provided with the low-voltage battery, and the detection method comprises the following steps: when the vehicle-mounted charger executes reverse pre-charging, detecting electrical parameters of the low-voltage battery before and after reverse pre-charging, obtaining the internal resistance R of the low-voltage battery according to the electrical parameters; and comparing the internal resistance R and the electrical parameter with a preset judgment standard, and judging whether the low-voltage battery breaks down or not according to a comparison result. Whether the low-voltage battery breaks down or not can be detected by means of a hardware circuit of the vehicle-mounted charger, additional components are not needed, and additional production cost is avoided.

Description

Technical Field

[0001] The present invention relates to the field of testing technology, and in particular to a vehicle charger and a fault detection method for a low-voltage battery thereof. Background Art

[0002] Traditional low-voltage battery health detection is achieved by adding additional switches and diagnostic resistors, that is, refer to the attached Figure 1 A first end of a first switch K1 is provided between the low-voltage battery and the vehicle-mounted low-voltage load, and a second end of the first switch K1 is connected in series with a diagnostic resistor Rd and then grounded.

[0003] In this way, by closing the first switch K1, the low-voltage battery is discharged through the diagnostic resistor Rd, and then the battery management system BMS calculates the internal resistance of the low-voltage battery by detecting the voltage and current of the low-voltage battery, so as to judge whether the low-voltage battery is healthy or whether a fault occurs through the internal resistance of the low-voltage battery.

[0004] However, the above traditional solution requires the addition of additional components, which will incur additional production costs. Summary of the invention

[0005] In view of this, the present invention provides an on-board charger and a low-voltage battery fault detection method thereof, which are used to solve the problem in the prior art that the low-voltage battery needs to add additional components.

[0006] The technical solution of the present invention is a method for detecting a fault of a low-voltage battery of an on-board charger, wherein the on-board charger comprises a high-voltage side and a low-voltage side provided with a low-voltage battery, and the detection method comprises:

[0007] When the on-board charger performs reverse pre-charging, the electrical parameters of the low-voltage battery before and after reverse pre-charging are detected, and the internal resistance R of the low-voltage battery is obtained according to the electrical parameters;

[0008] The internal resistance R and the electrical parameters are compared with preset judgment criteria, and whether the low-voltage battery fails is determined based on the comparison result.

[0009] Furthermore, the electrical parameters include:

[0010] The first voltage U1 and the first current I1 of the low-voltage battery before reverse pre-charging, and the second voltage U2 and the second current I2 of the low-voltage battery after reverse pre-charging.

[0011] Further, the obtaining the internal resistance R of the low-voltage battery according to the electrical parameter includes:

[0012]

[0013] Furthermore, comparing the internal resistance R and the electrical parameter with a preset judgment standard, and judging whether the low-voltage battery fails according to the comparison result, includes:

[0014] When V1≤U2<V2 and R≥R1, or U2≥V2 and R≥R2, it is determined that the low-voltage battery fails;

[0015] When V2≤U2<V3 and R1≤R<R2, or V3≤U2<V4 and R3≤R<R2, or U2≥V4 and R4≤R<R2, it is determined that the low-voltage battery has a fault warning;

[0016] When V3≤U2<V4 and R1≤R<R3, or U2≥V4 and R1≤R<R4, it is determined that the low-voltage battery has no fault;

[0017] Among them, V1, V2, V3 and V4 are all preset voltage values ​​in the preset judgment standard, and R1, R2, R3 and R4 are all preset internal resistance values ​​in the preset judgment standard.

[0018] Furthermore, when the low-voltage battery is reversely pre-charged, it is necessary to wait for a predetermined period of time and then detect the electrical parameters of the low-voltage battery after reverse pre-charging.

[0019] The present invention also proposes a vehicle charger using the above-mentioned low-voltage battery fault detection method, comprising a high-voltage side and a low-voltage side provided with a low-voltage battery, and the vehicle charger further comprises:

[0020] An electronic control unit, used for sending a reverse pre-charging instruction;

[0021] A communication circuit, used for receiving a reverse pre-charging instruction sent by an electronic control unit and outputting a control signal;

[0022] A DCDC power conversion circuit is located between the high voltage side and the low voltage side, and the DCDC power conversion circuit is used to receive the control signal to perform reverse pre-charging;

[0023] A detection circuit is located between the communication circuit and the DCDC power conversion circuit, and the detection circuit is used to detect the electrical parameters of the low-voltage battery before and after reverse pre-charging and transmit them to the calculation module, and the calculation module obtains the internal resistance R of the low-voltage battery according to the electrical parameters;

[0024] The judgment module is used to compare the internal resistance R and the electrical parameter with a preset judgment standard, and judge whether the low-voltage battery fails according to the comparison result.

[0025] Furthermore, the DCDC power conversion circuit includes a first capacitor, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a transformer and a first inductor;

[0026] The first switch tube and the second switch tube are connected in series to form a first bridge arm, and the third switch tube and the fourth switch tube are connected in series to form a second bridge arm; the transformer includes a primary winding and a secondary winding with a center tap end;

[0027] The first bridge arm, the second bridge arm and both ends of the first capacitor are connected to both ends of the high voltage side; the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding;

[0028] The center tap end of the secondary winding is connected in series with the first inductor and then connected to one end of the second capacitor, the first end of the secondary winding is connected to one end of the sixth switch tube, the second end of the secondary winding is connected to one end of the fifth switch tube, the other end of the fifth switch tube and the other end of the sixth switch tube are both connected to the other end of the second capacitor, and the two ends of the second capacitor are also connected to the two ends of the low-voltage side.

[0029] Furthermore, the DCDC power conversion circuit includes a first capacitor, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a transformer, a diode and a common-mode inductor;

[0030] The first switch tube and the second switch tube are connected in series to form a first bridge arm, and the third switch tube and the fourth switch tube are connected in series to form a second bridge arm; the transformer includes a primary winding and a secondary winding with a center tap end;

[0031] The first bridge arm, the second bridge arm and both ends of the first capacitor are connected to both ends of the high voltage side; the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding;

[0032] The upper tube of the second bridge arm is connected to the cathode of the diode, and the anode of the diode is connected to the first pin of the common mode inductor;

[0033] The center tap end of the secondary winding is connected to the second pin of the common-mode inductor, and the fourth pin of the common-mode inductor is connected to one end of the second capacitor; the first end of the secondary winding is connected to one end of the sixth switch tube, the second end of the secondary winding is connected to one end of the fifth switch tube, the other end of the fifth switch tube and the other end of the sixth switch tube are both connected to the other end of the second capacitor, and the two ends of the second capacitor are also connected to the two ends of the low-voltage side.

[0034] Furthermore, the calculation module is arranged in the electronic control unit or in the communication circuit or in the vehicle charger;

[0035] The judgment module is arranged in the electronic control unit or in the communication circuit or in the vehicle charger.

[0036] Furthermore, the high-voltage side includes a high-voltage battery and a vehicle-mounted high-voltage load arranged in parallel;

[0037] The low-voltage side includes a low-voltage battery and a vehicle-mounted low-voltage load arranged in series.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] The present invention can rely on the hardware circuit of the on-board charger itself to detect the health status of the low-voltage battery and determine whether the low-voltage battery fails, without adding additional components and generating additional production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present invention; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present invention or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 labor.

[0042] Figure 1A schematic diagram of a circuit connection between an existing low-voltage battery and a vehicle-mounted low-voltage load in the background technology;

[0043] Figure 2 This is a module block diagram of the vehicle charger proposed by the present invention;

[0044] Figure 3 A circuit diagram of a DCDC power conversion circuit proposed by the present invention;

[0045] Figure 4 A circuit diagram of another DCDC power conversion circuit proposed by the present invention;

[0046] Figure 5 is a preset judgment standard table of the present invention;

[0047] Figure 6 The electrical parameter table of the low-voltage battery proposed by the present invention before and after reverse pre-charging;

[0048] Figure 7 A flow chart of a method for detecting a fault of a low-voltage battery of an on-board charger proposed by the present invention.

[0049] Reference numerals:

[0050] 10. High-voltage side;

[0051] 11. High-voltage battery; 12. On-board high-voltage load;

[0052] 20. Low pressure side;

[0053] 21. Low voltage battery; 22. Vehicle-mounted low voltage load;

[0054] 30. Communication circuit;

[0055] 40. Electronic control unit;

[0056] 50. DCDC power conversion circuit;

[0057] 60. Detection circuit. DETAILED DESCRIPTION

[0058] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described features. In addition, it should be noted that this specification describes many features. Although certain features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0059] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0060] Example 1

[0061] The traditional low-voltage battery fault detection method requires an additional detection circuit to calculate the internal resistance of the low-voltage battery by detecting the current and voltage of the low-voltage battery, and then determine whether the low-voltage battery has a fault. However, this will require the addition of additional components and incur additional production costs.

[0062] Therefore, in order to solve the above problems, refer to the attached Figure 7 The present invention proposes a method for detecting a fault of a low-voltage battery of an on-board charger based on an existing hardware circuit. The on-board charger includes a high-voltage side 10 provided with a high-voltage battery 11, a low-voltage side 20 provided with a low-voltage battery 21, and a DCDC power conversion circuit 50 arranged between the high-voltage side 10 and the low-voltage side 20. The detection method includes:

[0063] When the on-board charger performs reverse pre-charging, the electrical parameters of the low-voltage battery 21 before and after reverse pre-charging are detected, and the internal resistance R of the low-voltage battery 21 is obtained according to the electrical parameters;

[0064] The internal resistance R and the electrical parameters are compared with the preset judgment criteria, and whether the low-voltage battery 21 fails is determined based on the comparison result.

[0065] It should be noted that the electronic control unit 40 is preferably a computer control module ECU of an automobile.

[0066] In this way, the present invention can rely on the hardware circuit of the on-board charger itself to detect the health status of the low-voltage battery 21 and determine whether the low-voltage battery 21 fails, without adding additional components and generating additional production costs.

[0067] Wherein, the internal resistance R and the electrical parameters are compared with the preset judgment standard, and whether the low-voltage battery 21 fails is judged according to the comparison result, including:

[0068] The electrical parameters include a first voltage U1 and a first current I1 when the low-voltage battery 21 is not reversely pre-charged, and a second voltage U2 and a second current I2 after the low-voltage battery 21 is reversely pre-charged;

[0069] The calculation formula of internal resistance R is:

[0070]

[0071] When V1≤U2<V2 and R≥R1, or U2≥V2 and R≥R2, it is determined that the low-voltage battery 21 has a fault, and then the computer control module ECU will display the fault information on the car dashboard, where the fault information includes: the fault light of the low-voltage battery 21 is continuously lit, or the fault information of the low-voltage battery 21 is played in the form of voice broadcast to prompt the user.

[0072] When V2≤U2<V3 and R1≤R<R2, or V3≤U2<V4 and R3≤R<R2, or U2≥V4 and R4≤R<R2, it is determined that a fault warning occurs in the low-voltage battery 21, and then the computer control module ECU will display the fault warning information on the car dashboard, wherein the fault warning information includes: the fault light of the low-voltage battery 21 flashes, or the fault warning information of the low-voltage battery 21 is played in the form of voice broadcast to warn the user.

[0073] When V3≤U2<V4 and R1≤R<R3, or U2≥V4 and R1≤R<R4, it is determined that the low-voltage battery 21 has no fault;

[0074] Among them, V1, V2, V3 and V4 are all preset voltage values ​​in the preset judgment standard, and R1, R2, R3 and R4 are all preset internal resistance values ​​in the preset judgment standard.

[0075] For ease of understanding, this embodiment provides specific values ​​of some preset voltage values ​​and preset internal resistance values ​​in the preset judgment criteria. Figure 5 It can be seen that V1 is preferably 9V, V2 is preferably 10V, V3 is preferably 11V, and V4 is preferably 11.5V; R1 is preferably 5Ω, R2 is preferably 12Ω, the calculation formula of R3 is preferably k1×U2+b1, and the calculation formula of R4 is preferably k2×U2+b2.

[0076] Among them, the formula k1×U2-b1 is derived from (11, 5) and (11.5, 11), k1=12, b1=-127, so R3=12×U2-127 (U2∈[11V, 11.5V]); the formula k2×U2-b2 is derived from (11.5, 11) and (13, 11.375), k2=0.25, b2=8.125, so R4=0.25×U2+8.125 (U2≥11.5V).

[0077] Specifically, when 9V≤U2<10V and R≥5Ω, or U2≥10V and R≥12Ω, it is determined that the low-voltage battery 21 has a fault, and then the computer control module ECU will display the fault information on the car dashboard, where the fault information includes: the fault light of the low-voltage battery 21 is continuously lit, or the fault information of the low-voltage battery 21 is played in the form of voice broadcast to prompt the user.

[0078] When 10V≤U2<11V and 5Ω≤R<12Ω, or 11V≤U2<11.5V and 12×U2-127(U2∈[11V, 11.5V])≤R<12Ω, or U2≥11.5V and 0.25×U2+8.125(U2≥11.5V)≤R<12Ω, it is determined that a fault warning occurs in the low-voltage battery 21, and then the computer control module ECU will display the fault warning information on the car dashboard, wherein the fault warning information includes: the fault light of the low-voltage battery 21 flashes, or the fault warning information of the low-voltage battery 21 is played in the form of voice broadcast to alert the user.

[0079] When 11V≤U2<11.5V and 5Ω≤R<12×U2-127(U2∈[11V,11.5V]), or U2≥11.5V and 5Ω≤R<0.25×U2+8.125(U2≥11.5V), it is determined that the low-voltage battery 21 has no fault.

[0080] Among them, in order to ensure that a stable and accurate second voltage U2 and second current I2 can be detected after the low-voltage battery 21 is reverse pre-charged, when the low-voltage battery 21 is reverse pre-charged, it is necessary to wait for a predetermined period of time and then detect the electrical parameters of the low-voltage battery 21 after reverse pre-charging.

[0081] Example 2

[0082] Based on the same inventive concept, refer to the attached Figure 2 The present invention further provides a vehicle charger, comprising a high voltage side 10 provided with a high voltage battery 11 and a low voltage side 20 provided with a low voltage battery 21, the vehicle charger further comprising:

[0083] The electronic control unit 40 is used to send a reverse pre-charging instruction;

[0084] The communication circuit 30 is used to receive the reverse pre-charging instruction sent by the electronic control unit 40 and output a control signal;

[0085] The DCDC power conversion circuit 50 is located between the high voltage side 10 and the low voltage side 20, and the DCDC power conversion circuit 50 is used to receive a control signal to perform reverse pre-charging, that is, reverse pre-charging the energy of the low voltage side 20 to the high voltage side 10;

[0086] The detection circuit 60 is located between the communication circuit 30 and the DCDC power conversion circuit 50, and the detection circuit 60 is used to detect the electrical parameters of the low-voltage battery 21 before and after reverse pre-charging and transmit them to the calculation module (not shown, the same throughout), and the calculation module calculates the internal resistance R of the low-voltage battery 21 according to the electrical parameters;

[0087] The judgment module (not shown, the same as in the whole text) is used to compare the internal resistance R and the electrical parameters with the preset judgment criteria, and judge whether the low-voltage battery 21 fails according to the comparison result.

[0088] In this way, the present invention can rely on the hardware circuit of the vehicle charger itself to detect the health status of the low-voltage battery 21, and compare the internal resistance R of the low-voltage battery 21 in combination with the second voltage U2 in the electrical parameter with the preset judgment standard, and then determine whether the low-voltage battery 21 has a fault based on the comparison result, without adding additional components or incurring additional production costs.

[0089] The comparison results are as follows:

[0090] 1. The low-voltage battery 21 fails: V1≤U2<V2 and R≥R1, or U2≥V2 and R≥R2.

[0091] 2. Fault warning of low-voltage battery 21: V2≤U2<V3 and R1≤R<R2, or V3≤U2<V4 and 12×U2-127(U2∈[V3,V4])≤R<R2, or U2≥V4 and 0.25×U2+8.125(U2≥V4)≤R<R2.

[0092] 3. The low-voltage battery 21 has no fault: V3≤U2<V4 and R1≤R<12×U2-127(U2∈[V3,V4]), or U2≥V4 and R1≤R<0.25×U2+8.125(U2≥V4).

[0093] And V1 is preferably 9V, V2 is preferably 10V, V3 is preferably 11V, and V4 is preferably 11.5V; R1 is preferably 5Ω, and R2 is preferably 12Ω.

[0094] Wherein, the calculation module is arranged in the electronic control unit 40 or in the communication circuit 30 or in the vehicle charger;

[0095] The determination module is arranged in the electronic control unit 40 or in the communication circuit 30 or in the vehicle charger.

[0096] It should be noted that, in this embodiment, the calculation module and the judgment module are both arranged in the electronic control unit 40 .

[0097] The high-voltage side 10 includes a high-voltage battery 11 and a vehicle-mounted high-voltage load 12 arranged in parallel. Of course, the high-voltage battery 11 and the vehicle-mounted high-voltage load 12 in this embodiment can also be arranged in series according to actual conditions, which is not limited here;

[0098] The low-voltage side 20 includes a low-voltage battery 21 and a vehicle-mounted low-voltage load 22 arranged in series. Of course, the low-voltage battery 21 and the vehicle-mounted low-voltage load 22 in this embodiment can also be arranged in parallel according to actual conditions, which is not limited here.

[0099] Among them, refer to the attached Figure 6 , the electrical parameters proposed in this embodiment include the following:

[0100] The first voltage U1 and the first current I1 of the low-voltage battery 21 before reverse pre-charging, and the second voltage U2 and the second current I2 of the low-voltage battery 21 after reverse pre-charging.

[0101] The calculation formula of internal resistance R is:

[0102]

[0103] Among them, this embodiment proposes a circuit diagram of a DCDC power conversion circuit 50, refer to the attached Figure 3 The DCDC power conversion circuit 50 includes a first capacitor C1, a second capacitor C2, a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a transformer T1 and a first inductor L1;

[0104] The first switch tube Q1 and the second switch tube Q2 are connected in series to form a first bridge arm, and the third switch tube Q3 and the fourth switch tube Q4 are connected in series to form a second bridge arm; the transformer T1 includes a primary winding and a secondary winding with a center tap end;

[0105] The first bridge arm, the second bridge arm and both ends of the first capacitor C1 are connected to both ends of the high voltage side 10; the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding;

[0106] The center tap end of the secondary winding is connected in series with the first inductor L1 and then connected to one end of the second capacitor C2. The first end of the secondary winding is connected to one end of the sixth switch tube Q6. The second end of the secondary winding is connected to one end of the fifth switch tube Q5. The other end of the fifth switch tube Q5 and the other end of the sixth switch tube Q6 are both connected to the other end of the second capacitor C2, and the two ends of the second capacitor C2 are also connected to the two ends of the low-voltage side 20.

[0107] It should be noted that a control unit is provided in the DCDC power conversion circuit 50, and the control unit can control the on and off of all switch tubes.

[0108] Therefore, when the communication circuit 30 receives the reverse pre-charging instruction sent by the electronic control unit 40, it will output a control signal. After the control unit receives the control signal, it will control the transformer T1 in the DCDC power conversion circuit 50 to reversely pre-charge the energy of the low-voltage side 20 to the high-voltage side 10; and the detection circuit 60 will first detect and record the first voltage U1 and the first current I1 of the low-voltage battery 21 before reverse pre-charging and transmit them to the calculation module, and then the low-voltage battery 21 is reversely pre-charged and after a predetermined time period, the detection circuit 60 will detect and record the first voltage U2 and the first current I2 of the low-voltage battery 21 after reverse pre-charging and transmit them to the calculation module, and then the calculation module calculates according to the formula The internal resistance R of the low-voltage battery 21 is obtained; then the judgment module receives the internal resistance R and the second voltage U2, and compares the internal resistance R combined with the second voltage U2 with the preset judgment standard, and finally determines whether the low-voltage battery 21 is faulty according to the comparison result.

[0109] Example 3

[0110] Based on the same inventive concept, this embodiment also provides another circuit diagram of a DCDC power conversion circuit 50, as shown in FIG. Figure 4 The DCDC power conversion circuit 50 includes a first capacitor C1, a second capacitor C2, a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a transformer T1, a diode D1 and a common mode inductor L2;

[0111] The first switch tube Q1 and the second switch tube Q2 are connected in series to form a first bridge arm, and the third switch tube Q3 and the fourth switch tube Q4 are connected in series to form a second bridge arm; the transformer T1 includes a primary winding and a secondary winding with a center tap end;

[0112] The first bridge arm, the second bridge arm and both ends of the first capacitor C1 are connected to both ends of the high voltage side 10; the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding;

[0113] The upper tube of the second bridge arm is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the first pin of the common mode inductor L2 (equivalent to the end of the second bridge arm close to the upper tube being connected to the cathode of the diode D1);

[0114] The center tap end of the secondary winding is connected to the second pin of the common-mode inductor L2, and the fourth pin of the common-mode inductor L2 is connected to one end of the second capacitor C2; the first end of the secondary winding is connected to one end of the sixth switch tube Q6, the second end of the secondary winding is connected to one end of the fifth switch tube Q5, the other end of the fifth switch tube Q5 and the other end of the sixth switch tube Q6 are both connected to the other end of the second capacitor C2, and the two ends of the second capacitor C2 are also connected to the two ends of the low-voltage side 20.

[0115] It should be noted that the common-mode inductor L2 can suppress common-mode noise, reduce electromagnetic interference, and protect subsequent circuits, while the diode D1 provides a freewheeling path, protects switching devices, and prevents reverse current; and the first pin and the second pin of the common-mode inductor L2 are both the same-name terminals.

[0116] Therefore, when the communication circuit 30 receives the reverse pre-charging instruction sent by the electronic control unit 40, it will output a control signal. After the control unit receives the control signal, it will control the common-mode inductor L2, the diode D1 and / or the transformer T1 in the DCDC power conversion circuit 50 to reversely pre-charge the energy of the low-voltage side 20 to the high-voltage side 10; and the detection circuit 60 will first detect and record the first voltage U1 and the first current I1 of the low-voltage battery 21 before reverse pre-charging and transmit them to the calculation module, and then the low-voltage battery 21 is reverse pre-charged and after a predetermined time period, the detection circuit 60 will detect and record the first voltage U2 and the first current I2 of the low-voltage battery 21 after reverse pre-charging and transmit them to the calculation module, and then the calculation module will calculate according to the formula The internal resistance R of the low-voltage battery 21 is obtained; then the judgment module receives the internal resistance R and the second voltage U2, and compares the internal resistance R and the second voltage U2 with the preset judgment standard, and finally judges whether the low-voltage battery 21 fails according to the comparison result.

[0117] Obviously, the embodiments described above are only some embodiments of the present invention, rather than all embodiments. The preferred embodiments of the present invention are given in the accompanying drawings, but they do not limit the patent scope of the present invention. The present invention can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Although the present invention has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions recorded in the aforementioned specific embodiments, or to perform equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the specification and drawings of the present invention, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A method for detecting a fault of a low-voltage battery of an on-board charger, wherein the on-board charger comprises a high-voltage side (10) and a low-voltage side (20) provided with a low-voltage battery (21), characterized in that: The detection method comprises: When the on-board charger performs reverse precharging, electrical parameters of the low-voltage battery (21) before and after reverse precharging are detected, and an internal resistance R of the low-voltage battery (21) is obtained based on the electrical parameters; The internal resistance R and the electrical parameter are compared with a preset judgment standard, and whether the low-voltage battery (21) has a fault is determined based on the comparison result.

2. The method for detecting a fault of a low-voltage battery of a vehicle charger according to claim 1, characterized in that: The electrical parameters include: A first voltage U1 and a first current I1 of the low-voltage battery (21) when reverse pre-charging is not performed, and a second voltage U2 and a second current I2 of the low-voltage battery (21) after reverse pre-charging is performed.

3. The method for detecting a fault of a low-voltage battery of a vehicle charger according to claim 2, characterized in that: The step of obtaining the internal resistance R of the low-voltage battery (21) according to the electrical parameter comprises:

4. The method for detecting a fault of a low-voltage battery of a vehicle charger according to claim 3, characterized in that: The step of comparing the internal resistance R and the electrical parameter with a preset judgment standard and judging whether the low-voltage battery (21) fails according to the comparison result comprises: When V1≤U2<V2 and R≥R1, or U2≥V2 and R≥R2, it is determined that the low-voltage battery (21) has a fault; When V2≤U2<V3 and R1≤R<R2, or V3≤U2<V4 and R3≤R<R2, or U2≥V4 and R4≤R<R2, it is determined that a fault warning occurs in the low-voltage battery (21); When V3≤U2<V4 and R1≤R<R3, or U2≥V4 and R1≤R<R4, it is determined that the low-voltage battery (21) has no fault; Among them, V1, V2, V3 and V4 are all preset voltage values ​​in the preset judgment standard, and R1, R2, R3 and R4 are all preset internal resistance values ​​in the preset judgment standard.

5. The method for detecting a fault of a low-voltage battery of a vehicle charger according to claim 1, characterized in that: When the low-voltage battery (21) is reversely precharged, it is necessary to wait for a predetermined period of time and then detect the electrical parameters of the low-voltage battery (21) after reverse precharge.

6. A vehicle charger using the low-voltage battery fault detection method according to any one of claims 1 to 5, comprising a high-voltage side (10) and a low-voltage side (20) provided with a low-voltage battery (21), characterized in that: The vehicle charger also includes: An electronic control unit (40), used for sending a reverse pre-charging instruction; A communication circuit (30) is used to receive a reverse pre-charging instruction sent by an electronic control unit (40) and output a control signal; A DCDC power conversion circuit (50) is located between the high voltage side (10) and the low voltage side (20), and the DCDC power conversion circuit (50) is used to receive the control signal to perform reverse pre-charging; A detection circuit (60) is located between the communication circuit (30) and the DCDC power conversion circuit (50), and the detection circuit (60) is used to detect electrical parameters of the low-voltage battery (21) before and after reverse precharging and transmit them to a calculation module, and the calculation module obtains the internal resistance R of the low-voltage battery (21) according to the electrical parameters; A judgment module is used to compare the internal resistance R and the electrical parameter with a preset judgment standard, and judge whether the low-voltage battery (21) has a fault according to the comparison result.

7. The vehicle charger according to claim 6, characterized in that: The DCDC power conversion circuit (50) comprises a first capacitor, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a transformer and a first inductor; The first switch tube and the second switch tube are connected in series to form a first bridge arm, and the third switch tube and the fourth switch tube are connected in series to form a second bridge arm; the transformer includes a primary winding and a secondary winding with a center tap end; The first bridge arm, the second bridge arm and both ends of the first capacitor are all connected to the two ends of the high voltage side (10); the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding; The center tap end of the secondary winding is connected in series with the first inductor and then connected to one end of the second capacitor, the first end of the secondary winding is connected to one end of the sixth switch tube, the second end of the secondary winding is connected to one end of the fifth switch tube, the other end of the fifth switch tube and the other end of the sixth switch tube are both connected to the other end of the second capacitor, and the two ends of the second capacitor are also connected to the two ends of the low-voltage side (20).

8. The vehicle charger according to claim 6, characterized in that: The DCDC power conversion circuit (50) comprises a first capacitor, a second capacitor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a transformer, a diode and a common mode inductor; The first switch tube and the second switch tube are connected in series to form a first bridge arm, and the third switch tube and the fourth switch tube are connected in series to form a second bridge arm; the transformer includes a primary winding and a secondary winding with a center tap end; The first bridge arm, the second bridge arm and both ends of the first capacitor are all connected to the two ends of the high voltage side (10); the midpoint of the first bridge arm is connected to the first end of the primary winding, and the midpoint of the second bridge arm is connected to the second end of the primary winding; The upper tube of the second bridge arm is connected to the cathode of the diode, and the anode of the diode is connected to the first pin of the common mode inductor; The center tap end of the secondary winding is connected to the second pin of the common-mode inductor, and the fourth pin of the common-mode inductor is connected to one end of the second capacitor; the first end of the secondary winding is connected to one end of the sixth switch tube, the second end of the secondary winding is connected to one end of the fifth switch tube, the other end of the fifth switch tube and the other end of the sixth switch tube are both connected to the other end of the second capacitor, and the two ends of the second capacitor are also connected to the two ends of the low-voltage side (20).

9. The vehicle charger according to claim 6, characterized in that: The calculation module is arranged in the electronic control unit (40) or in the communication circuit (30) or in a vehicle charger; The judgment module is arranged in the electric control unit (40) or in the communication circuit (30) or in a vehicle charger.

10. The vehicle charger according to claim 6, characterized in that: The high-voltage side (10) comprises a high-voltage battery (11) and a vehicle-mounted high-voltage load (12) arranged in parallel; The low-voltage side (20) comprises a low-voltage battery (21) and a vehicle-mounted low-voltage load (22) which are arranged in series.

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