Method for diagnosing the proper functioning of an on-board charger of a motor vehicle

Abstract

The invention relates to a method for diagnosing the proper functioning of an on-board charger of a motor vehicle having a plurality of phase-switching relays and / or a plurality of current sensors in a PFC circuit connected to a PFC control device. According to the invention, the same sensor system and actuator system, which already control the power electronics in the OBC, are used for the tests or plausibility checks carried out as part of the diagnostic method. In particular, cyclical current and voltage measurements are carried out to this end within the OBC in various test sequences, and these are compared with predefined reference values depending on the switching position of the phase-switching relays.

Description

[0001] Method for diagnosing the functionality of a motor vehicle's on-board charger

[0002] The invention relates to a method for diagnosing the functionality of an on-board charger of a motor vehicle with several phase-changing relays and / or several current sensors in a PFC circuit, which is connected to a PFC control unit.

[0003] Nowadays, environmentally friendly vehicles, such as electric vehicles (EVs) or plug-in hybrid vehicles (PHEVs), use on-board chargers (OBCs) to charge the drive battery of such vehicles.

[0004] The traction battery is a high-voltage direct current (HVDC) battery, hereinafter referred to as an HV battery. Charging stations for such batteries in electric and hybrid vehicles provide either direct current (DC) or alternating current (AC). AC charging typically uses an onboard battery bank (OBC) carried in the electric vehicle.

[0005] The OBC receives its input voltage from a so-called wallbox, which is provided, for example, by an energy supplier at a charging station.

[0006] The OBC generates a direct current or voltage to charge the high-voltage battery. Therefore, it is extremely important to check the OBC's functionality before commissioning.

[0007] Therefore, it is particularly necessary to cyclically check the functionality of the electrical components installed within the OBC. In addition to electrical components such as coils, resistors, and various semiconductor components, the OBC contains numerous sensors as well as switches and relays, specifically phase-change relays.

[0008] In particular, such phase-changing relays ensure that they can transfer the appropriately conditioned current from the AC power source directly to the HV battery.

[0009] A phase change relay can be controlled to an open or closed position. When the phase change relay is closed, current can be drawn from the AC power source through the OBC and transferred directly to the HV battery via the phase change relay. Conversely, when the phase change relay is open, no current can be transferred to the HV battery via the phase change relay.

[0010] Fault diagnosis of such phase-change relays is therefore very important for the stable operation of the entire electrical system in an EV or PHEV. Furthermore, a reliable and fail-safe system must be in place throughout the entire driving time, making cyclical testing of the phase-change relays before each operation of the OBC indispensable.

[0011] In order to identify an error or defect within the OBC caused by a faulty switching or incorrect position of the phase change relays due to a component fault or defect before the power electronics are activated, it must therefore be ensured that the phase change relays have the correct switch position.

[0012] According to the current state of the art, testing of such phase-change relays has so far been carried out using auxiliary or so-called mirror contacts. These auxiliary contacts are mechanically coupled to the phase-change relays and can thus contribute to diagnosing a contact position. The major disadvantage of using such auxiliary contacts is primarily that they incur additional costs and thus higher overall costs for an OBC, and also require additional installation space, thereby imposing layout limitations.

[0013] To effectively circumvent these disadvantages, the present invention proposes a novel diagnostic method which is able to check the functionality of such switches, in particular phase-changing relays, in an inexpensive and simple manner.

[0014] In this context, the present invention proposes to use the same sensors and actuators already used for controlling power electronics for a novel diagnostic method for phase-change relays.

[0015] It is known that the state of the art has already dealt with various diagnostic and monitoring methods for electronic components in the past.

[0016] For example, EP 18 190 21 B1 discloses a method and a device for monitoring a multi-phase network in order to reliably detect the failure of a phase. In particular, the phase positions and voltages are measured and subsequently analyzed, so that a precise statement can be made regarding a fault or anomaly in a three-phase line.

[0017] For example, DE 10 2021 129 579 A1 describes a method and a system for controlling a multi-phase OBC in an electric vehicle. Specifically, when an OBC is receiving power from a charging station (e.g., a mains power supply) to charge the EV's traction battery, the charging process is stopped if an incorrect voltage condition, such as an overvoltage or undervoltage condition of the received current, occurs.

[0018] Based on the current state of the art, the object of the invention is therefore to demonstrate a diagnostic method for an OBC in a motor vehicle in which the switching state of the phase-changing relays installed there is checked.

[0019] To solve this problem, a diagnostic method according to claim 1 is presented. The dependent claims relate to advantageous further developments of the invention.

[0020] According to the invention, the same sensors and actuators are used for the checks and plausibility checks within the diagnostic procedure as already control the power electronics in the OBC.

[0021] In particular, cyclic current and voltage measurements are performed within the OBC in various test sequences, and these are compared with predefined reference values ​​depending on the switching position of the phase change relays.

[0022] The above objectives and properties and further advantages of the invention will now be clarified from the following description in conjunction with the accompanying drawings.

[0023] They show:

[0024] Fig. 1: a block diagram of an electrical system with the essential electrical components used to charge an HV battery, for example in an EV according to the state of the art;

[0025] Fig. 2: a block diagram of the electrical system with a detailed

[0026] Illustration of a multi-phase OBC, here in particular a three-phase (or three-path) OBC with two phase-changing relays R x and R2 between the circuit paths, as well as the corresponding current and voltage sensors.

[0027] Fig. 3 to a flowchart with the individual test sequences 30 to 70, Fig. 7: the individual test steps of the inventive

[0028] Diagnostic procedure based on the corresponding current and voltage measurements for plausibility checks of the phase change relays R x and R2.

[0029] As can be seen in the block diagram in Fig. 1, the diagnostic method according to the invention is based on an electrical system in which the conversion of the input alternating voltage into an output direct voltage is the main focus.

[0030] The electrical system used for this purpose consists primarily of an OBC 1, which is connected to an AC power source 5, and an HV battery 6 connected to its output.

[0031] In addition, the OBC 1 comprises an electromagnetic compatibility filter (EMC filter 8), a power factor correction circuit (PFC circuit 3), and an active rectifier 2 located within the PFC circuit 3, followed by an intermediate circuit capacitor 21. A DC-DC converter 7 is also connected to the PFC circuit 3 and is ultimately connected to the high-voltage battery 6. The electrical system shown in Fig. 1 also has two communicating control units. The first control unit, the PFC control unit 4, is directly connected to the PFC circuit 3, while the main control unit 9 communicates with the PFC control unit 4.

[0032] As shown in Fig. 1, the input AC voltage 5 is rectified in an OBC 1 using a rectifier 2 and converted to DC voltage via a DC / DC converter 7 using a power converter consisting of a PFC circuit 3 and supplied to the HV battery 6.

[0033] The DC voltage converter 7 is connected between an output terminal of the PFC circuit 3 and an input terminal of an HV battery 6 to receive a regulated DC voltage output by the PFC circuit 3 and convert it into a voltage for charging the high-voltage battery 7.

[0034] In many AC line applications, an EMC filter 8 is additionally connected upstream of the input to the OBC 1 in order to perform a low-pass filtering of the input AC voltage 5 in order to further reduce the high-frequency line interference.

[0035] Additionally, a digital signal processor (PFC-DSP), here called PFC control unit 4, ensures that 3 different electrical, thermal and user-defined parameters are monitored within the PFC circuit, so that precise control of the output voltage and frequency can be carried out using the phase-changing relays.

[0036] The PFC control unit 4 implements comprehensive diagnostic, protection, and thermal management functions for the safe and reliable operation of the OBC 1 based on various voltage, current, and temperature sensor outputs connected to the PFC control unit 4. Furthermore, the PFC control unit 4 is connected to the main control unit 9 of the entire electrical system and can prompt the main control unit 9 to take further action in the event of faults within the OBC 1.

[0037] In this specific case, depending on the result of the diagnostic procedure in a specific test sequence 30-70, the PFC control unit 4 can either send a warning signal in the event of a fault or confirmation of the operational readiness of the individual tested electrical components (e.g. current and / or voltage sensors, phase switching relays) to the main control unit 9.

[0038] The main control unit 9, in conjunction with the PFC control unit 4, thus controls the entire operation of the electrical system shown in Fig. 1.

[0039] Fig. 2 shows, with reference to Fig. 1, a block diagram of the electrical system with a detailed representation of the OBC 1 and, in particular, the integrated PFC circuit 3. This circuit includes, among other things, the three circuit paths 22, 23, 24 with a PFC choke coil arrangement (12), the two phase-changing relays R xand R2, the rectifier 2, and the voltage measuring point 10 as well as the current measuring points 11 , shown.

[0040] As can be seen further in Fig. 2, the OBC 1 in this embodiment is multiphase, or preferably three-phase. The OBC 1 thus has three phases L x , L2, L3, which are assigned to the respective circuit paths 22, 23, 24 and a neutral conductor (ground wire) L N the alternating current source 5.

[0041] The PFC circuit 3 integrated in the OBC 1 contains, as explained at the beginning, two phase-changing relays R. x and R2. The first phase change relay R x The phase change relay R2 is located between the inputs of circuit paths 22 and 23. The phase change relay R2, on the other hand, is located between circuit paths 22 and 24.

[0042] Each phase changeover relay R x and R2 can be switched between an open and a closed state.

[0043] A closed phase changeover relay connects the inputs of two circuit paths between which this phase changeover relay is located. Conversely, an open phase changeover relay disconnects the two circuit paths between which the phase changeover relay is located.

[0044] Fig. 2 shows the two phase-changing relays R x and R2 each in an open state, that is, in the so-called rest position.

[0045] In this specific case, this means that the input of circuit path 23 is not connected to the input of circuit path 22 via the phase-changing relay R. x is connected.

[0046] Similarly, the input of circuit path 24 is also not connected to the input of circuit path 22 via the phase-changing relay R2.

[0047] Are the two phase switching relays R xand R2, on the other hand, is closed, so the input of circuit path 23 is connected to the input of circuit path 22 when the phase-changing relay R x is located between these two circuit paths.

[0048] Similarly, the two circuit paths 24 and 22 are closed via the phase-changing relay R2.

[0049] Since the mains power supply is multi-phase worldwide due to the various connection options of the AC grid, it is necessary to distribute the energy within an OBC 1 across the different phases or circuit paths. Switching these circuit paths on or off is accomplished via the phase-changing relays R. x and R2, so that the OBC 1 can be operated either single-phase or multi-phase in that case.

[0050] The PFC control unit 4 checks whether and which mains power supply is currently available, and then sends the corresponding commands to open or close the two phase switching relays R. x and R2 specifies, so that the current is distributed according to the switched circuit paths in an active rectifier 2.

[0051] As can be seen from Fig. 2, the active rectifier 2 consists of a total of six switching elements, each in the form of a MOSFET semiconductor switch in a three-phase bridge circuit (= so-called B6 bridge) in three half-bridges.

[0052] In addition, two rectifier diodes 13, 14 are connected in front of the B6 bridge, which ensure that the falling electrical power loss can be advantageously reduced here and also provide protection against possible overvoltages.

[0053] Typically, a semiconductor switch which is arranged between the tap or load and the positive input voltage line is referred to as a high-side semiconductor 15, 17, 19 or high-side switch, and a semiconductor switch which is arranged between the tap and a negative input voltage line or a ground line is referred to as a low-side semiconductor 16, 18, 20 or low-side switch.

[0054] Furthermore, at most one switch-on process (low to high) and one switch-off process (high to low) occurs per half-bridge and one pulse-width modulation period. In this case, the diagnostic procedure is performed for current and / or voltage measurements on the low-side semiconductors 16, 18, 20 and via the circuit paths 22, 23, 24. The diagnostic procedure according to the invention will now be explained in more detail below with reference to Figures 3 to 7 for the individual test sequences 30 to 70.

[0055] The flowcharts in Figs. 3 to 7 are primarily based on the prior plausibility check of the current and voltage sensors 10a, 10b, 10c; 11a, 11b, 11c and the subsequent verification of the two phase-changing relays R. x and R2.

[0056] The current sensors 11a, 11b, 11c are preferably Hall sensors or current measuring coils, which are coupled in the current measuring point 11 in Fig. 2 with the respective choke coils 12a, 12b, 12c, in the PFC choke coil arrangement 12.

[0057] For the voltage sensors 10a, 10b, 10c, capacitive elements, in particular a capacitor arrangement, and / or at least one resistive element, in particular a resistor arrangement, are suitable. These are located in the voltage measuring point 10 in Fig. 2.

[0058] According to the invention, the following steps are proposed for checking the above-mentioned sensors, as illustrated in Fig. 3:

[0059] For this purpose, the test sequence 30 is called up by the PFC control unit 4, in which in particular a measurement of the alternating voltage via the switching path 22 between phase L is performed. x and the neutral conductor L N is carried out.

[0060] The process is started in step 31.

[0061] In step 32) it is checked whether an alternating voltage is present.

[0062] In step 33) the first low-side semiconductor 16 is switched on.

[0063] This is preferably a MOSFET. A MOSFET is a semiconductor device with three terminals: a source (S), a gate (G), and a drain (D). The first low-side semiconductor 16 is connected via its drain terminal to the first inductor 12a and its source terminal to the neutral conductor L. NThe system is connected for a predetermined time interval t (pulse duration). Subsequently, the pulse of length t is induced within the voltage peak of the phase voltage U. L1 / 22 (measured between the potential L x and L N ) switched.

[0064] A current measurement is then taken between the first choke coil 12a and the first phase L. The first current sensor 11a and the first choke coil 12a are connected in series.

[0065] The resulting change in current AI12a in the first choke coil 12a is determined in a further step. For this purpose, the coil current before pulse 112a (t = start) is compared with the coil current after pulse 112a (t = end).

[0066] The following applies:

[0067] AI12a = 112a (t = end) - 112a (t = start)

[0068] The evaluation of the current change AI12a forms the basis for further decision steps of the diagnostic method according to the invention.

[0069] Next, the individual sensors will be checked for plausibility.

[0070] The procedure now checks in step 33a) whether the first current sensor 11a is functional.

[0071] The current of the first choke coil 12a is checked.

[0072] If the choke coil current change AI12a is zero within the measurement tolerance, then the first current sensor 11a is defective. Branch "No" to step 33a1 is selected, and a signal is output from the PFC control unit 4 indicating that the first current sensor 11a is defective. The procedure then terminates in step 33a1. If, however, the first current sensor 11a is not defective, branch "Yes" is selected, and the diagnostic procedure proceeds to step 33b), where the first voltage sensor 10a is then checked for functionality.

[0073] The change in the choke coil current AI12a is checked within the measurement tolerance. If this is greater than zero and the measured voltage U L1 / 22 If the measurement tolerance is zero, it follows that the first voltage sensor 10a is defective, and branch "No" is selected for step 33b1. Analogous to step 33a1, the PFC control unit 4 transmits a signal to the main control unit 9 with the information that the first voltage sensor 10a is defective, and the diagnostic procedure is terminated.

[0074] If, however, the first voltage sensor 10a is OK, the branch “Yes” is selected and in the last step 33c of the test sequence 30 it is checked whether the change in the choke coil current AI12a with respect to the time interval T (with T = t (end) - 1 (start) multiplied by the inductance value of the first choke coil 12a, corresponds to the value of the measured voltage, where

[0075] U L1 / 22 = L * AI12a / T; with T as the time interval.

[0076] If the two values ​​match, it follows that both the first current sensor 11a and the first voltage sensor 10a are functional and the diagnostic procedure continues with the next test sequence 40, in which the phase-changing relays R 1( R2 can be checked for functionality.

[0077] In test sequence 40, the first phase change relay R is subsequently tested. x Its functionality was checked. The first phase change relay R x It is located between the first circuit path 22 and the second circuit pad 23. The PFC control unit 4 now controls the first phase change relay R. x according to the current diagnostic step, in order to either open (switch off) or close (switch on) this relay.

[0078] In step 41, phase L is now x by closing the phase change relay R xswitched to circuit path 23.

[0079] In the next step 42, the second low-side semiconductor 18 is now switched on for a pulse of length t. The second low-side semiconductor 18 is also connected via its drain terminal to the second choke coil 12b and via its source terminal to the neutral conductor L. N tied together.

[0080] Finally, the pulse with length t is located in the voltage peak of the phase voltage U. L1 / 23 (measured between the potential L x and L N ) switched.

[0081] The current measurement in the second current sensor 11 b is now carried out via the second choke coil 12b connected in series.

[0082] Here too, the resulting change in current AI12b in the second choke coil 12b is determined by comparing the coil current before pulse 112b (t = start) with the coil current after pulse 112b (t = end).

[0083] The following applies:

[0084] AI12b = 112b (t = end) - 112b (t = start)

[0085] In the next step 43, the two voltage and current sensors 10b and 11b are checked for plausibility - analogous to steps 33a) - 33c).

[0086] The system checks whether the choke coil current change AI12b is within the measurement tolerance. If so, it follows that the second current sensor 11b is implausible. Consequently, the "No" branch is selected for step 43a1, and a signal is output from the PFC control unit 4 indicating that current sensor 11b is defective.

[0087] The procedure is then terminated in step 43a1.

[0088] If, however, the current sensor 11 a is not defective, the branch “Yes” is selected and the diagnostic procedure proceeds to step 43b).

[0089] Here, it is checked whether the change in the choke coil current AI12b is zero within the measurement tolerance, and whether the measured voltage U is also within the tolerance. L1 / 23within the measurement tolerance, the value is zero. If this is the case, it means that the phase-change relay R x is defective. At the same time, the "No" branch is selected for step 43b1. Here too, a signal is sent from the PFC control unit 4 to the main control unit 9 indicating that the phase change relay R is defective. x is defective and the diagnostic procedure is therefore terminated.

[0090] If, however, the relationship exists that the change in the choke coil current AI12b, based on the time interval T (with T = t (end) - 1 (start)) and multiplied by the inductance value of the second choke coil 12b, corresponds to the value of the measured voltage U L1 / 23 corresponds,

[0091] U L1 / 23 = L * AI12b / T; with T as the time interval, it follows that the second current sensor 11b is OK and the phase change relay R x successfully establishes a galvanic connection between the voltage U L1 / 23and the second choke coil 12b. As a result, the branch “Yes” is selected, and the diagnostic procedure can therefore proceed to the next test sequence 50.

[0092] In test sequence 50, the phase change relay R is now used. x so closed (step 52) that the current from the second phase L2 flows via circuit path 23 to the neutral conductor L N flows. Analogous to test sequence 40, the same plausibility steps for determining the functionality of the second voltage and current sensors 10b, 11b are carried out in test sequence 50, but here in a changed order.

[0093] Step 53a focuses in particular on comparing the measured voltage U L2 / 23 with the choke coil current change AI12b in the foreground:

[0094] If the change in the choke coil current AI12b, based on the time interval T (with T = t (end) - 1 (start)), is multiplied by the inductance value L of the second choke coil 12b, the value of the measured voltage U L2 / 23 corresponds and applies.

[0095] U L2 / 23 = L * AI12b / T; with T as the time interval.

[0096] As a result, the phase change relay R x erroneously the galvanic connection between the voltage U L2 / 23 produced.

[0097] However, if the change in the choke coil current AI12b is greater than zero within the measurement tolerance, and the measured voltage U L2 / 23 If the voltage measurement U is zero within the measurement tolerance, it follows that the voltage measurement U L2 / 23 This is not plausible. Because a faulty current measurement 111 b was already ruled out in the previous procedure step 50a.

[0098] If, on the other hand, U L2 / 23= L * AI12b / T; with T being the time interval, it follows that the second voltage sensor 10b is OK and the phase change relay R x successfully establishes a galvanic connection between the voltage U L2 / 23 and the second choke coil 12b.

[0099] The diagnostic procedure can therefore proceed to checking the functionality of the second phase-changing relay R2. Here too, the same procedures are used analogously as with the first phase-changing relay R2. x described, the third voltage and current sensors 10c and 11c were checked for plausibility.

[0100] The phase-changing relay R2 is located between circuit pad 22 and circuit path 24. Here, the phases L x and controlled L3.

[0101] As can be seen in Fig. 6, the diagnostic procedure for the phase changeover relay R2 is now continued in test sequence 60. For this purpose, the first phase L xThe circuit path 24 is switched via the phase-changing relay R2. The current flows from the first phase L. x via circuit path 24 to the neutral conductor L N flows.

[0102] In a further step 63a, the third low-side semiconductor 20 is then switched on for a pulse of length T, analogous to the test sequence steps already described. The third choke coil 12c is also energized here, and a current measurement of the choke coil current change AI12c is also performed accordingly.

[0103] Depending on the measurement result within the measurement tolerance, a decision is then made analogously, as shown in Fig. 4-5, steps 43a-43c, as to whether one of the electrical components is fully functional or not. The resulting results for the second phase-change relay R2 are then transmitted from the PFC control unit 4 to the main control unit 9, as already described above.

[0104] The relevant diagnostic steps in test sequence 60 are in particular steps 63a, 63b and 63c.

[0105] In step 63a, it is checked whether the change in the choke coil current AI12c is zero within the measurement tolerance. If this is the case, it follows that the third current sensor 11c is defective. If this is not the case, the branch "Yes" is selected, and in step 63b it is checked whether the change in the choke coil current AI12c is greater than zero within the measurement tolerances and the measured voltage U L1 / 24 The reading at the third voltage sensor 10c is zero. If this is the case, then the phase change relay R2 is defective. A faulty voltage measurement U L1 / 24 was already ruled out in the previous test step.

[0106] If the test was successfully performed and passed according to the selected criteria, then in the last step 63c of test sequence 60 it is checked whether the correlation

[0107] UL1 / 24 = L * AI12C / T; with T as the time interval.

[0108] If this relationship exists, it means that the third current sensor 11c is functional, and that the phase changeover relay R2 has successfully established a galvanic connection between the first phase L x the throttle coil 12c has been manufactured, so that the diagnostic procedure can proceed to the last test sequence 70.

[0109] In test sequence 70 (see Fig. 7), the phase-change relay R2 is also switched. In this case, the phase-change relay R2 is closed, so that the third phase L3 is coupled to the third current sensor 11c and the third choke coil 12c.

[0110] Similarly, the third low-side semiconductor 20 is switched on for a pulse of length T (step 72).

[0111] The resulting change in current in the third choke coil AI12c is measured and then evaluated in the PFC control unit 4.

[0112] In step 73a, it is specifically checked whether the following relationship U L3 / 24 = L * AI12C / T; with T as the time interval.

[0113] If the measured values ​​and the calculation show this relationship, it means that the phase change relay R2 is not correctly establishing a connection between the first phase L x and the third choke coil 12c. This in turn means that the phase-change relay R2 is defective and the charging of the HV battery 6 cannot be carried out without problems. In this case, analogous to step 43b1, a message is sent from the PFC circuit 4 to the main control unit 9, and the diagnostic procedure is terminated (step 73a1).

[0114] However, in a further diagnostic step 73b1, the relationship between the choke coil current change AI12c and the voltage measurement U is examined. L3 / 24 is checked, and it turns out that the choke coil current change AI12c is greater than zero and the measured voltage U L3 / 24 If the value is also zero within the measurement tolerance, this means that the third voltage sensor 10c is defective.

[0115] A faulty current measurement in the third choke coil 12c and a faulty phase change relay R2 were already ruled out in the previous diagnostic step 73a.

[0116] If, therefore, the connection

[0117] U L3 / 24 = L * AI12C / T; where T is the time interval, this means that the third voltage sensor 10c is OK, and that the phase change relay R2 has successfully established the galvanic connection between the third phase L3 and the third choke coil 12c.

[0118] If all previous test sequences are successfully completed, the diagnostic procedure is terminated and a message is sent from the PFC control unit 4 to the main control unit 9 indicating that both phase switching relays R x and R2 plausible and therefore functional.

[0119] Overall, the present invention presents a simple, cost-effective and safe diagnostic method which can be used to check the functionality of phase-change relays (relays) and / or sensors not only in the automotive sector, but also in other industries.

[0120] Reference sign

[0121] 1 On-board charger (OBC)

[0122] 2 rectifiers

[0123] 3 PFC circuit

[0124] 4 PFC control unit

[0125] 5 AC power source

[0126] 6 HV batteries

[0127] 7 DC-DC converters

[0128] 8 EMC filters

[0129] 9 Main control unit

[0130] 10 Voltage measuring point

[0131] 10a first voltage sensor

[0132] 10b second voltage sensor

[0133] 10c third voltage sensor

[0134] 11 Electricity metering point

[0135] 11a first current sensor

[0136] 11 b second current sensor

[0137] 11 c third current sensor

[0138] 12 PFC choke coil arrangement

[0139] 12a first choke coil

[0140] 12b second choke coil

[0141] 12c third choke coil

[0142] 13,14 rectifier diodes

[0143] 15 first high-side semiconductor

[0144] 17 second high-side semiconductor

[0145] 19 third high-side semiconductor 16 first low-side semiconductor

[0146] 18 second low-side semiconductor

[0147] 20 third low-side semiconductor

[0148] 21 Intermediate circuit capacitor

[0149] 22 first circuit path

[0150] 23 second circuit path

[0151] 24 third circuit path

[0152] R x first phase changeover relay

[0153] R2 second phase change relay

[0154] L x first phase

[0155] L2 second phase

[0156] L3 third phase

[0157] L N Neutral conductor (neutral wire)

Claims

Patent claims 1. Method for diagnosing the functionality of an on-board charger (1) of a motor vehicle with multiple phase-changing relays (R) x , R2) and several voltage sensors (10a, 10b, 10c) and / or several current sensors (11a, 11b, 11c) in a PFC circuit (3) which is connected to a PFC control unit (4), characterized in that the method comprises the following steps: a) Checking in the PFC control unit (4) whether the current sensors (11a, 11b, 11c) at a current measuring point (11 ) and the voltage sensors (10a, 10b, 10c) at a voltage measuring point (10) are functional after passing a test sequence (30); b) Checking in the PFC control unit (4) whether the first phase change relay ( / ? x ) is functional taking into account the following steps: i) Connecting the first phase (L) via the second circuit path (23) to the first phase changeover relay (R) x ) to the neutral conductor (L N); ii) Switching the second low-side semiconductor (18) and coupling the second current sensor (11b) to the second choke coil (12b) on the neutral conductor (L N ) for a predetermined time interval t; iii) Determination of the voltage U L1 / 23 ; iv) Connecting the second phase (L2) via the second circuit path (23) to the neutral conductor (L N ); v) Switching the second low-side semiconductor (18) and coupling the second current sensor (11b) to the second choke coil (12b) on the neutral conductor (L N ) for a predetermined time t; vi) Determination of the voltage U L2 / 23 c) Check in the PFC control unit (4) whether the second phase changeover relay (R2) is functional by taking the following steps: i) Connect the first phase (L) via the third circuit path 24 to the second phase changeover relay (R2) to the neutral conductor (L N) ii) Switching the third low-side semiconductor (20) and coupling the third current sensor (11c) to the third choke coil (12c) on the neutral conductor (L N ) for a predetermined time interval t; iii) Determination of the voltage U L1 / 24 iv) Connecting the third phase (L3) via the third circuit path 24 to the second phase changeover relay (R2) to the neutral conductor (L N ); v) Switching the third low-side semiconductor (20) and coupling the third current sensor (11c) to the third choke coil (12c) on the neutral conductor (L N ) for a predetermined time interval t; vi) Determination of the voltage U L3 / 24 ; 2. The method according to claim 1, characterized in that the PFC control unit (4) executes several test sequences (30) to (70) successively.

3. The method according to claim 1 or 2, characterized in that the PFC control unit (4) transmits the results of the individually executed test sequences (30) to (70) to the main control unit (9).

4. Method according to one of claims 1 to 3 characterized in that the PFC circuit (3), an intermediate circuit capacitor (21), a rectifier (2), a PFC choke coil arrangement (12), a current measuring point (11), a voltage measuring point (10) and the two phase switching relays (R) x , R2).

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