Method and circuit for protecting an in-vehicle charging device

Abstract

1. A method for protecting an on-board charging device, comprising: detecting phase and neutral voltages from a grid; detecting a current signal representative of a compensation current generated by a compensation circuit; combining the phase voltages to obtain a homopolar voltage signal; squaring the current signal and the homopolar voltage signal to obtain a first rectangular current wave and a second rectangular voltage wave; combining the first and second square waves to generate an output signal having a first logic level when the first and second square waves are in phase and a second logic level when the first and second square waves are not in phase; generating a voltage that increases in proportion to a duration of each section of the output signal having a first value; comparing a value of the voltage with a limit value; and generating an alarm signal if the value of the voltage exceeds the limit value.

Description

Technical Field

[0001] The present invention relates to a method and a circuit for protecting an in-vehicle charger.

[0002] Therefore, the present invention is mainly applied to the field of automobiles, especially the design and construction of charging systems for in-vehicle batteries.

Background Art

[0003] In fact, in the field of electric vehicles, the charging modes of battery packs are classified into two different macro-categories: in-vehicle chargers and ground chargers.

[0004] As the name indicates, an "in-vehicle charger" is incorporated in a vehicle and includes all the power supplies and control electronics necessary to convert alternating current from the grid into the direct current required for recharging the battery pack.

[0005] On the other hand, a "ground" charger is a normal "column" or wall box that directly provides conversion by supplying direct current to the vehicle.

[0006] Therefore, in-vehicle type battery chargers have significant problems from the perspective of user safety, and it is considered that the battery charger must be equipped with an appropriate protection system. This is because the battery charger has to manage the alternating current provided by the grid and convert the alternating current into direct current to recharge the high-voltage battery.

[0007] This is extremely important in the construction of a non-insulated type in-vehicle charging system, in which the battery charger has a direct electrical connection with the alternating current wiring socket, thus defining a true mesh that can close the circuit to the ground.

[0008] In these types of battery chargers, the continuous switching of electronic components within the converter block actually changes the voltage of the battery capacitor, resulting in the problem of compensating for leakage current caused by the switching that leads to current leakage to ground.

[0009] In three-phase systems, these currents exceed 100 mA RMS and often reach amplitude levels close to 150 mARMS, requiring compensation to avoid intervention by circuit breakers or differential switches.

[0010] Therefore, a compensation circuit is inserted into the charging device that is configured to generate a current equal to and in the opposite direction to the current flowing to ground through the battery capacitor.

[0011] Unfortunately, this presented a significant safety problem, as the compensation circuit could intervene even in the presence of insulation losses between the battery charger and the vehicle chassis, potentially "deceiving" the differential switch and preventing it from operating.

[0012] To overcome this drawback, software systems have been developed that are managed by a microcontroller and can distinguish between cases where the current flowing through the system is capacitive and therefore flows through a capacitor and is thus to be compensated for, and cases where the current is resistive and therefore dangerous (i.e., current flowing through the human body or another resistor).

[0013] However, since these are extremely important safety systems in electric vehicles, the applicant realized that having purely software-level safety at such critical points of the system may not be sufficient. [Overview of the Initiative]

[0014] Therefore, an object of the present invention is to provide a method and circuit for protecting an in-vehicle charging device that can overcome the aforementioned drawbacks of the prior art.

[0015] In particular, an object of the present invention is to provide a method and circuit for protecting an in-vehicle charging device that is highly reliable and easy to implement or manufacture.

[0016] The aforementioned objective is achieved by a method and circuit for protecting an in-vehicle charging device having one or more features of the claims of the subsequent patent claims.

[0017] In particular, this method includes detecting the phase voltage and neutral point voltage supplied from the grid, and detecting a current signal representing the compensation current generated by the compensation circuit.

[0018] Preferably, the phase voltages are coupled to obtain a common-pole voltage signal.

[0019] Preferably, the current signal and the same-polarity voltage signal are used to obtain a first rectangular current wave and a second rectangular voltage wave. Square wave conversion It will be done.

[0020] Preferably, the first rectangular wave and the second rectangular wave are coupled to produce an output signal having a first logic level when the first rectangular wave and the second rectangular wave are in phase, and a second logic level when the first rectangular wave and the second rectangular wave are not in phase.

[0021] Therefore, preferably, a first voltage is generated that increases in proportion to the duration of each section of the output signal having the first value.

[0022] The value of the first voltage is compared with a limit value, and an alarm signal is generated if the value of the first voltage exceeds the limit value.

[0023] A further object of the present invention is to provide a circuit that protects a charging device.

[0024] This circuit includes an addition network configured to receive, as input, signals representing the phase voltage and neutral point voltage of the grid, and to return, as output, a same-pole voltage signal.

[0025] Preferably, an element for detecting a current signal representing a compensation current is provided.

[0026] Furthermore, preferably, a conversion stage is provided that is configured to receive, as input, the same-pole voltage signal and the current signal, and to generate a first rectangular wave representing the same-pole voltage signal and a second rectangular wave representing the current signal.

[0027] The coupling stage is located downstream of the conversion stage and is configured to couple both the first rectangular wave and the second rectangular wave together so as to generate an output signal that has a first logic level when the first rectangular wave and the second rectangular wave are in the same phase, and has a second logic level when the first rectangular wave and the second rectangular wave are not in the same phase.

[0028] The charging module (or charger) is also preferably provided downstream of the coupling stage and is operably arranged and configured to generate a first voltage that increases in proportion to the duration of each section of the output signal having the first value.

[0029] The comparator element is preferably associated with the charging module and is configured to compare the value of the first voltage with a limit value and generate an alarm signal when the value of the first voltage exceeds the limit value.

[0030] The dependent claims incorporated herein by reference correspond to various embodiments of the present invention.

Brief Description of the Drawings

[0031] Further features and advantages of the present invention will become more apparent from the illustrative, and therefore non-limiting, description of preferred but non-exclusive embodiments of methods and circuits for protecting an in-vehicle charging device, as shown in the accompanying drawings. [Figure 1] The structure of an in-vehicle charging device is shown in a schematic diagram. [Figure 2] A schematic diagram of the circuit structure for protecting the in-vehicle charging device according to the present invention is shown. [Modes for carrying out the invention]

[0032] Referring to the attached drawings, reference numeral 1 shows the overall circuit protecting the in-vehicle charging device 100 according to the present invention.

[0033] In this specification, the term "onboard charging device 100" is intended to generally define any charging system for a traction battery pack 6 that can be connected to an AC grid and converted to DC before supplying power to the battery.

[0034] Preferably, the grid is of the three-phase type.

[0035] Therefore, the charging device 100 comprises at least one casing C (connected to earth) associated with a connection socket 101 for connecting to a grid G, and the casing C houses a converter assembly 104 configured to convert the alternating current provided by the grid G ​​into a direct current usable for recharging the battery pack 105.

[0036] Therefore, the connection socket 101 is configured to accept both the three-phase L1, L2, L3 and the neutral wire N.

[0037] Preferably, the charging device 100 further comprises at least one electromagnetic disturbance filter element located along the current input line, i.e., between the connection socket 101 and the converter assembly 104.

[0038] More preferably, there are two electromagnetic disturbance filter elements, the first filter element 102 along the (AC) current input line and the second filter element 103 along the (DC) current output line, i.e., between the converter assembly 104 and the battery pack 105.

[0039] In a preferred embodiment, the charging device 100 is non-isolated, that is, it provides a physical (i.e., non-inductive) connection between the battery and the power distribution system.

[0040] Preferably, in this type of device 100, the converter assembly 104 comprises at least one boost module and at least one buck module.

[0041] In a preferred embodiment, the converter assembly 104 comprises the following: - A first conversion stage (or AC-DC converter) configured to convert the alternating current provided by the grid G ​​into direct current, - A charging stage, preferably defined by a capacitor bank, operably positioned downstream of a first conversion stage, and configured to be charged by receiving its output. - A second conversion stage (or DC-DC converter) configured to modulate the level of DC supplied to the battery pack 105.

[0042] In a preferred embodiment, as described above, the charging device 100 is non-isolated, so the second conversion stage is directly connected to the battery pack (i.e., without a conversion / induction stage).

[0043] Furthermore, the charging device 100 preferably includes a compensation circuit 106 configured to generate a compensation current equal to and opposite to the leakage current flowing toward the earth PE.

[0044] To avoid the safety issues described at the beginning, the charging device 100 may include a microcontroller with a protection module 107 configured to generate an alarm signal when a relevant resistive component is detected within the leakage current.

[0045] Alternatively, or together with, the charging device is associated with the protection circuit 1 according to the present invention.

[0046] Therefore, the protection circuit 1 is preferably configured to receive signals representing the phase voltage and neutral point voltage of the grid G ​​and a current signal representing the compensation current as inputs, and to generate an alarm signal as an output when a relevant resistive component is detected in the leakage current.

[0047] More specifically, the protection circuit 1 includes an summing network 2 configured to receive signals representing the phase voltage and neutral point voltage of the grid G ​​as inputs and return the same-pole voltage signals as outputs.

[0048] In this specification, the term “equal voltage” is intended to mean that the voltage at the actual star point of a three-phase system, relative to the voltage at the ideal star point, coincides with the centroid of the triangle of line voltages.

[0049] Furthermore, an element is provided to detect a current signal Icomp representing the compensation current.

[0050] These signals, namely the current signal and the same-pole voltage signal, are then injected into the conversion stage X.

[0051] The conversion stage 3 is preferably configured to receive the same-pole voltage signal and the current signal as inputs and to generate a first rectangular wave representing the same-pole voltage signal and a second rectangular wave representing the current signal.

[0052] Preferably, the conversion stage 3 comprises a first conversion module 4 (or transformer) and a second conversion module 5 (or transformer), each configured to generate a first square wave and a second square wave, respectively.

[0053] In a preferred embodiment, the first conversion module 4 and the second conversion module 5 are each defined by a comparator.

[0054] The comparator is configured to receive a voltage signal or current signal of the same polarity as input and to generate a square wave representing the sign of the signal.

[0055] In other words, a comparator is configured to compare an input signal to a null reference and output a signal with a value of 1 if the input signal has a positive sign, and a signal with a value of 0 if the input signal has a negative sign (or output a signal with a value of 0 if the input signal has a positive sign, and a signal with a value of 1 if the input signal has a negative sign).

[0056] The electronic protection circuit 1 further includes a coupling stage 6 configured to couple a first rectangular wave and a second rectangular wave together, which generates an output signal having a first logic level when the first rectangular wave and the second rectangular wave are in phase, and a second logic level when the first rectangular wave and the second rectangular wave are not in phase.

[0057] In other words, coupling stage 6 is configured to generate a signal representing the phase shift between the first square wave and the second square wave, to return a first logic level at time intervals when the two waves are in phase (i.e., when the current signal and the same-pole voltage signal have the same sign), and to return a second logic level at time intervals when the two waves are not in phase (i.e., when the current signal and the same-pole voltage signal have different signs).

[0058] In a preferred embodiment, the coupling stage 6 is at least partially defined by a multiplier that returns a value of 1 only when the two square waves overlap.

[0059] A charging module 7 is also provided, which is operably positioned downstream of the coupling stage 6.

[0060] The charging module 7 is configured to generate a first voltage that increases in proportion to the duration of each section of the output signal having the first value.

[0061] In other words, the first voltage generated by the charging module 7 is proportional to the duration of the overlap between the first and second rectangular waves, and therefore defines a precise indicator of the phase shift between the same-electrode voltage signal and the current signal.

[0062] Preferably, the charging module is defined by an RC circuit having resistors 8 and capacitors 9 in series with respect to each other.

[0063] Next, the protection circuit 1 includes a comparator element 10 configured to compare the value of the first voltage with a limit value and generate an alarm signal if the voltage level of the capacitor exceeds the limit value.

[0064] The value of the first voltage is proportional to the time constant of the RC circuit and the acceptable phase level between the two input signals.

[0065] In a preferred embodiment, the time constant is equal to 2.2 ms, and the first voltage limit is reached in about 9 ms.

[0066] In a preferred embodiment, the protection circuit 1 is arranged in parallel (i.e., redundantly) with the protection module 107 of the microcontroller.

[0067] Advantageously, this allows for two independent levels of safety, thus increasing the reliability of the system.

[0068] Preferably, in this regard, the charging device 100 includes at least one enable node (108) connected to module 107 and protection circuit 1 and configured to generate an enable signal to compensation circuit 106 only when there is no alarm signal generated by module 107 and protection circuit 1.

[0069] A further object of the present invention is a method for protecting the in-vehicle charging device 100, which is preferably, but not necessarily, carried out by the protection circuit 1 according to the present invention as described herein.

[0070] Therefore, although the method is described in more detail below, it should be emphasized that all features mentioned and described in relation to Circuit 1 should be considered adaptable to the following description of the method of the present invention, with modifications where necessary, unless explicitly stated or incompatible.

[0071] This method includes detecting the phase voltage and neutral point voltage supplied from the grid G, and detecting a current signal representing the compensation current generated by the compensation circuit.

[0072] Therefore, the phase voltages are coupled together to obtain the same-pole voltage signal.

[0073] Therefore, the current signal and the same-polarity voltage signal are used to obtain a first rectangular current wave and a second rectangular voltage wave. Square wave conversion It will be done.

[0074] More specifically, the square wave actually defines the code of the input signal.

[0075] Therefore, the first and second rectangular waves are coupled to produce an output signal having a first logic level when the first and second rectangular waves are in phase, and a second logic level when the first and second rectangular waves are not in phase.

[0076] Preferably, the first square wave and the second square wave are multiplied together. When the two square waves overlap, the multiplication yields a value of 1, so the first logic level is equal to 1 and the second logic level is equal to 0.

[0077] Advantageously, this method makes it possible to obtain easily interpretable signals that provide accurate information about the phase shift between the current signal and the voltage signal of the same pole.

[0078] In fact, the degree of phase shift is proportional to the duration of the overlap interval, and therefore proportional to the duration of the output signal section having the first logical value.

[0079] At this point, a first voltage is generated that increases in proportion to the duration of each section of the output signal having the first value.

[0080] The step of generating the first voltage is preferably performed by charging a capacitor located in an RC circuit similar to that described above.

[0081] Therefore, the value of the first voltage is compared with a limit value, and an alarm signal is generated if the level of the first voltage of the capacitor exceeds the limit value.

[0082] Therefore, following the generation of the alarm signal, a step is provided to disable the compensation circuit 106.

[0083] This invention achieves its intended purpose and provides significant advantages.

[0084] In fact, the reliability of a protection system can be increased by using entirely physical / hardware-based protection methods and circuits.

Claims

1. A method for protecting an in-vehicle charging device (100), The charging device (100) comprises a socket for connecting to a grid (G), a converter assembly (104) configured to convert the alternating current provided by the grid (G) into a direct current usable for charging a battery pack (105), and a compensation circuit (106) configured to generate a compensation current (Icomp) equal to and in the opposite direction to one or more leakage currents flowing toward earth, and the method is as follows: - A step of detecting the phase voltage and neutral point voltage from the grid (G), - A step of detecting a current signal representing the compensation current (Icomp) generated by the compensation circuit (106), - A step of coupling the phase voltages to obtain a voltage signal of the same pole, - A step of converting the current signal and the voltage signal of the same pole into rectangular waves in order to obtain a first rectangular current wave and a second rectangular voltage wave, - The steps of coupling the first rectangular wave and the second rectangular wave such that an output signal having a first logic level when the first rectangular wave and the second rectangular wave are in phase, and having a second logic level when the first rectangular wave and the second rectangular wave are not in phase, - A step of generating a first voltage that increases in proportion to the duration of each section of the output signal having the first logic level, - A step of comparing the value of the first voltage with a limit value, A method comprising the step of generating an alarm signal when the value of the first voltage exceeds the limit value.

2. The method according to claim 1, wherein the step of combining the first rectangular wave and the second rectangular wave includes multiplying the first rectangular wave and the second rectangular wave together.

3. The method according to claim 1 or 2, wherein the step of generating the first voltage is performed by charging a capacitor (9).

4. The method according to any one of claims 1 to 3, further comprising the step of disabling the compensation circuit (106) following the generation of the alarm signal.

5. A circuit for protecting an on-board charging device (100), The charging device (100) comprises a socket for connecting to a grid (G), a converter assembly (104) configured to convert the alternating current provided by the grid (G) into a direct current usable for charging a battery pack (105), and a compensation circuit (106) configured to generate a compensation current (Icomp) equal to and in the opposite direction to one or more leakage currents flowing toward earth, and the device, - An summing network (2) configured to receive signals representing the phase voltages (L1, L2, L3) and neutral point voltage (N) of the grid (G) as inputs and generate same-pole voltage signals as outputs, - An element for detecting the current signal (Icomp) representing the compensation current, - A conversion stage (3) configured to receive the same-pole voltage signal and the current signal as inputs and generate a first rectangular wave representing the same-pole voltage signal and a second rectangular wave representing the current signal, - A coupling stage (6) configured to couple the first rectangular wave and the second rectangular wave such that it generates an output signal having a first logic level when the first rectangular wave and the second rectangular wave are in phase, and a second logic level when the first rectangular wave and the second rectangular wave are not in phase, - A charging module (7) operably positioned downstream of the coupling stage (6) and configured to generate a first voltage that increases in proportion to the duration of each section of the output signal having the first logic level, A circuit comprising: a comparator element (10) configured to compare the value of the first voltage with a limit value and generate an alarm signal if the value of the first voltage exceeds the limit value.

6. The circuit according to claim 5, wherein the conversion stage (3) comprises a first conversion module (4) and a second conversion module (5), each configured to generate the first square wave and the second square wave, respectively.

7. The circuit according to claim 6, wherein the first conversion module (4) and the second conversion module (5) are each defined by a comparator configured to receive the corresponding same-pole voltage signal or current signal as input and to generate a square wave representing the sign of the signal.

8. The coupling stage (6) is at least partially defined by a multiplier, according to any one of claims 5 to 7.

9. The circuit according to any one of claims 5 to 8, wherein the charging module (7) is defined by a circuit having a resistor (8) and a capacitor (9) in series with respect to each other.

10. An on-board charging device (100), - A socket (101) for connecting to the grid (G), - A converter assembly (104) configured to convert the alternating current provided by the grid (G) into direct current usable for recharging the battery pack (105), - A compensation circuit (106) configured to generate a compensation current equal to and in the opposite direction to the leakage current flowing toward the earth (PE) and - A microcontroller equipped with a protection module (107) configured to generate an alarm signal when a relevant resistance component is detected within the leakage current, - A protection circuit (1) according to any one of claims 5 to 9, arranged in parallel with the protection module (107), - An on-board charging device (100) comprising: at least one enable node (108) connected to the module (107) and the protection circuit (1), and configured to generate an enable signal to the compensation circuit (106) only when there is no alarm signal generated by the module (107) and the protection circuit (1).

Images