Power conversion electronic appliance for electric or hybrid cars

Abstract

The power conversion electronic appliance (A) for electric cars, installable on an electric vehicle without low-voltage battery and connectable to two electric batteries (B1, B2) for the power supply of the electric vehicle connected in series with each other, comprises three single-phase battery chargers (OBC1, OBC2, OBC3), wherein: a first single-phase battery charger (OBC1) is connected to a first high-voltage electric battery (B1) for the power supply of the electric vehicle and supplies the first electric battery (B1); a second single-phase battery charger (OBC2) is connected to a second high-voltage electric battery (B2) for the power supply of the electric vehicle and supplies the second electric battery (B2); a third single-phase battery charger (OBC3) is connected in series to the first electric battery (B1) and to the second electric battery (B2) and supplies the first and second batteries (B1, B2) in series; and wherein the first single-phase battery charger (OBC1) and the second single-phase battery charger (OBC2) comprise a first and a second built-in low-voltage DC / DC converter respectively, which are configured for the low-voltage power supply to the low-voltage circuits of the electric vehicle.

Description

[0001] POWER CONVERSION ELECTRONIC APPLIANCE FOR ELECTRIC OR HYBRID CARS

[0002] Technical Field

[0003] The present invention relates to a power conversion electronic appliance for electric cars, specifically of the type of an OBC and DC / DC converter device usable on electric vehicles without low-voltage battery.

[0004] Background Art

[0005] As is well known, in order to enable periodic recharging of batteries, electric vehicles are provided with special appliances (so-called “on-board chargers”, OBCs) connectable at the input to an AC power line and at the output to the battery of the vehicle.

[0006] In addition, in order to reduce the number of devices and components installed on an electric vehicle as much as possible, especially so as to reduce overall costs, there is a need felt to eliminate the low-voltage electric battery dedicated to powering all low-voltage systems on the electric vehicle (e.g., the control unit, closure system and communication devices).

[0007] However, eliminating the low-voltage battery poses several issues, particularly in terms of safety and reliability of the solution.

[0008] In fact, it is of paramount importance to ensure power supply to the most critical low-voltage loads (such as e.g., steering, airbags, etc.) even in the event of a single failure of the DC / DC converters; hence the use of at least two DC / DC converters capable of both redundantly supplying power to the critical loads and separately supplying additional low- voltage loads. As an additional safety measure, it is also necessary to prevent the possible failure of the HV battery supplying the DC / DC converters from simultaneously impairing the operation of the two DC / DC converters.

[0009] Description of the Invention

[0010] The main aim of the present invention is to devise a power conversion electronic appliance for electric vehicles which can be used on electric vehicles without low- voltage battery and is capable of meeting safety regulations related to critical low- voltage devices while using a small number of converters. Another object of the present invention is to devise a power conversion electronic appliance for electric cars which can be used on electric vehicles without low- voltage battery and which allows the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and efficient to use as well as cost-effective solution.

[0011] The aforementioned objects are achieved by this power conversion electronic appliance for electric cars according to the characteristics described in claim 1. Brief Description of the Drawings

[0012] Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a power conversion electronic appliance for electric cars, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings wherein:

[0013] Figure 1 is a general diagram of the appliance according to the invention;

[0014] Figure 2 is a diagram showing a possible embodiment of a single-phase battery charger of the appliance according to the invention;

[0015] Figure 3 is a diagram showing an additional and preferred embodiment of a single-phase battery charger of the appliance according to the invention.

[0016] Embodiments of the Invention

[0017] With particular reference to the general diagram shown in Figure 1, letter A globally denotes a power conversion electronic appliance for electric cars, specifically of the type of an On-Board Charger (OBC) and DC / DC converter device employable on electric vehicles without 12 V low-voltage battery and powered by a (rated) 800V split battery.

[0018] Specifically, the appliance A according to the invention is installable on an electric vehicle without low-voltage (12V) battery and is connectable to two electric batteries Bl, B2 for the power supply of the electric vehicle connected in series to each other.

[0019] Preferably, the two electric batteries Bl, B2 consist of respective rated 400V batteries connected together to form a rated 800V split battery.

[0020] Specifically, the appliance A comprises three single-phase battery chargers OBC1, OBC2, OBC3, wherein:

[0021] - a first single-phase battery charger OBC1 is connected to a first high- voltage (rated 400V) electric battery Bl for the power supply of the electric vehicle and supplies such first electric battery Bl;

[0022] - a second single-phase battery charger OBC2 is connected to a second high- voltage (rated 400V) electric battery B2 for the power supply of the electric vehicle and supplies such second electric battery B2;

[0023] - a third single-phase battery charger OBC3 is connected in series to the first electric battery B 1 and to the second electric battery B2 and supplies such first and second batteries Bl, B2 in series.

[0024] Therefore, the three single-phase battery chargers OBC1, OBC2, OBC2 make three single-phase channels: each of two of the three single-phase channels supplies one of the two rated 400V batteries B 1 and B2, while the third channel (rated 800 Vdc) supplies the two batteries Bl and B2 in series.

[0025] In addition, the first single-phase battery charger OBC1 and the second singlephase battery charger OBC2 comprise a first and second built-in low-voltage DC / DC converter respectively, which are configured for the low- voltage (12V) power supply to the low- voltage circuits of the electric vehicle.

[0026] The fact that each of the two DC / DC converters is independently supplied by one of the two rated 400V battery blocks prevents any failure of one of the two high- voltage battery blocks from inhibiting power to both DC / DC converters at the same time.

[0027] According to a possible embodiment of the appliance A, the third single-phase battery charger OBC3 also comprises a respective third built-in low-voltage DC / DC converter for the low- voltage (12V) power supply.

[0028] Therefore, the appliance A according to the invention allows making up for the absence of a low- voltage battery (12V) on the electric vehicle, while enabling multiple benefits to be achieved.

[0029] First of all, in case of failure of one of the single-phase battery chargers OBC1, OBC2, OBC3, the two battery chargers still working allow charging the electric batteries Bl and B2. Specifically, in the event of failure of the first single-phase battery charger OBC 1 and / or of the second single-phase battery charger OBC2, the third single-phase battery charger OBC3 still allows charging the electric batteries Bl, B2, since it is connected in series to the batteries themselves.

[0030] In addition, according to a preferred embodiment, the appliance A comprises balancing means operationally connected to the first single-phase battery charger OBC1 and to the second single-phase battery charger OBC2, configured to control the first single-phase battery charger OBC1 and the second single-phase battery charger OBC2 during charging, to balance the charge of the two batteries Bl and B2, which, by supplying both common loads and different loads, may discharge differently.

[0031] Specifically, through such balancing means, when charging, the first and the second single-phase battery chargers OBC1 and OBC2 are commanded to charge the two rated 400V batteries Bl, B2 differently, thus balancing possible different discharges due to the different load applied to the DC / DC converters.

[0032] In addition, according to a preferred embodiment, such balancing means comprise a balancing switch R7 which connects the single-phase inputs R and S of the first and of the second single-phase battery chargers OBC1 and OBC2 and which is configured to be closed while driving to carry out balancing.

[0033] Thus, while driving, it is possible to balance the two batteries Bl, B2 by closing the balancing switch R7 and taking advantage of the bidirectionality of the two single-phase battery chargers OBC1 and OBC2.

[0034] As schematically shown in Figure 1, the appliance A also comprises a switching matrix SWM configured to connect / disconnect the phases R, S, T, and the neutral N to / from the single-phase battery chargers OBC1, OBC2, OBC3, to switch the appliance A between a three-phase operational mode and a single-phase operational mode.

[0035] The switching matrix SWM comprises a plurality of switches Rl, R2, R3, R4, R5, R6 properly connected to each other, as known to the engineer in the field. Conveniently, such switching matrix SWM is also provided with the balancing switch R7, connected between the single-phase inputs R and S of the first and of the second single-phase battery chargers OBC1 and OBC2.

[0036] Figure 2 schematically shows a possible embodiment of the first single-phase battery charger OBC1, of the second single-phase battery charger OBC2 and possibly of the third single-phase charger OBC3, with built-in DC / DC converter. According to this possible embodiment, the first single-phase battery charger OBC1, the second single-phase battery charger OBC2 and possibly the third single-phase battery charger OBC3, comprise:

[0037] - a first filter Fl connected to the switching matrix SWM;

[0038] - a Power Factor Correction (PFC) module connected to the first filter Fl;

[0039] - a first high-voltage converter HV CNV, consisting of a transformer comprising a primary side HV CNV PS connected to the PFC module and a secondary side HV CNV SS connected to the high-voltage output / input HVDC connected to one of the electric batteries Bl, B2;

[0040] - a second filter F2 connected to the high-voltage output / input HVDC;

[0041] - a second low-voltage converter LV CNV, consisting of a transformer comprising a primary side LV CNV PS connected to the high-voltage output / input HVDC and a secondary side LV CNV SS connected to the low- voltage output LVDC, for the power supply of the low- voltage (12 V) circuits of the electric vehicle.

[0042] Advantageously, according to a further preferred embodiment, schematically shown in Figure 3, in order to further reduce the overall size, weight and cost of the appliance A, the first single-phase battery charger OBC1 and the second single-phase charger OBC2 comprise just one three-port output transformer which is used for both high-voltage conversion (rated 400V) and low-voltage conversion (12V), respectively.

[0043] According to a possible embodiment of the appliance A, in case more redundancy is needed, the third single-phase battery charger OBC3 also comprises just one three-port output transformer CNV.

[0044] Specifically, according to this preferred embodiment, the first single-phase battery charger OBC1, the second single-phase battery charger OBC2 and possibly the third single-phase battery charger OBC3, comprise: - an individual filter F connected to the switching matrix SWM;

[0045] - a Power Factor Correction (PFC) module connected to the filter F;

[0046] - an individual low-voltage and high-voltage converter CNV, consisting of an individual transformer comprising an individual primary side CNV PS connected to the PFC module, a first secondary side HV CNV SS connected to the high-voltage output / input HVDC connected to one of the electric batteries Bl, B2, and a second secondary side LV CNV SS connected to the low-voltage output LVDC, for the power supply of the low- voltage circuits (12 V) of the electric vehicle.

[0047] According to this preferred embodiment, during charging, the primary side CNV PS of each transformer is connected to the grid-powered intermediate circuit; both the high-voltage secondary side HV CNV SS and the low-voltage secondary side LV CNV SS are simultaneously powered by the primary side CNV PS.

[0048] When driving, the secondary side HV CNV SS becomes the primary one for the DC / DC converter, which can thus supply power to the grid at low voltage.

[0049] With this solution, it is possible to save the two transformers HV CNV and LV CNV shown in the embodiment in Figure 2 and the two full bridges normally adopted in the primary stage of the DC / DC converter.

[0050] The first and the second input filters Fl and F2 of the two DC / DC converters are no longer required as they are not needed in this type.

[0051] Considering that each OBC channel has a power rating of about 7 Kwatts, they are oversized when driving with respect to the power needed by the primary one, thus increasing the reliability of the device. When charging, the energy not used by the DC / DC converter is supplied to the high-voltage battery.

[0052] It has in practice been ascertained that the described invention achieves the intended objects.

[0053] In particular, the fact is emphasized that the appliance according to the invention can be used on electric vehicles without low-voltage battery, thus enabling compliance with the strict safety regulations related to the critical low-voltage devices while using a reduced number of converters and components.

Claims

CLAIMS1) Power conversion electronic appliance (A) for electric cars, installable on an electric vehicle without low-voltage battery and connectable to two electric batteries (B 1, B2) for the power supply of the electric vehicle connected in series with each other, characterized by the fact that said appliance (A) comprises three single-phase battery chargers (OBC1, OBC2, OBC3), wherein: a first single-phase battery charger (OBC1) is connected to a first high- voltage electric battery (Bl) for the power supply of the electric vehicle and supplies said first electric battery (Bl); a second single-phase battery charger (OBC2) is connected to a second high- voltage electric battery (B2) for the power supply of the electric vehicle and supplies said second electric battery (B2); a third single-phase battery charger (OBC3) is connected in series to said first electric battery (B 1) and to said second electric battery (B2) and supplies said first and second batteries (Bl, B2) in series; and wherein said first single-phase battery charger (OBC1) and said second single-phase battery charger (OBC2) comprise a first and a second built-in low- voltage DC / DC converter respectively, which are configured for the low-voltage power supply to the low- voltage circuits of the electric vehicle.2) Appliance (A) according to claim 1, characterized by the fact that said third single-phase battery charger (OBC3) comprises a respective third built-in low- voltage DC / DC converter.3) Appliance (A) according to one or more of the preceding claims, characterized by the fact that said two electric batteries (Bl, B2) consist of respective rated 400V batteries connected together to form a rated 800V split battery.4) Appliance (A) according to one or more of the preceding claims, characterized by the fact that it comprises balancing means operationally connected to said first single-phase battery charger (OBC1) and to said second single-phase battery charger (OBC2), configured to control said first single-phase battery charger (OBC1) and said second single-phase battery charger (OBC2)during charging, to balance the charge of said two batteries (Bl, B2).5) Appliance (A) according to one or more of the preceding claims, characterized by the fact that it comprises at least one balancing switch (R7) which connects the single-phase inputs (R, S) of said first and second singlephase battery chargers (OBC1, OBC2) and which is configured to be closed while driving to perform balancing of said batteries (Bl, B2).6) Appliance (A) according to one or more of the preceding claims, characterized by the fact that it comprises a switching matrix (SWM) configured to connect / disconnect the phases (R, S, T) and the neutral (N) to / from said singlephase battery chargers (OBC1, OBC2, OBC3), to switch the appliance (A) between a three-phase operational mode and a single-phase operational mode.7) Appliance (A) according to claim 6, characterized by the fact that said switching matrix (SWM) comprises said balancing switch (R7).8) Appliance (A) according to one or more of the preceding claims, characterized by the fact that at least one of either said first single -phase battery charger (OBC1), said second single-phase battery charger (OBC2) or said third single-phase battery charger (OBC3) comprises:- a first filter (Fl) connected to said switching matrix (SWM);- a Power Factor Correction (PFC) module connected to said first filter (Fl);- a first high-voltage converter (HV CNV), consisting of a transformer comprising a primary side (HV CNV PS) connected to the PFC module and a secondary side (HV CNV SS) connected to the high-voltage output / input (HVDC) connected to one of the electric batteries (Bl, B2);- a second filter (F2) connected to the high-voltage output / input (HVDC);- a second low-voltage converter (LV CNV), consisting of a transformer comprising a primary side (LV CNV PS) connected to the high-voltage output / input (HVDC) and a secondary side (LV CNV SS) connected to the low-voltage output (LVDC), for the power supply of the low-voltage circuits of the electric vehicle.9) Appliance (A) according to one or more of the preceding claims, characterized by the fact that at least one of either said first single -phase batterycharger (0BC1), said second single-phase batery charger (OBC2) or said third single-phase batery charger (OBC3) comprises an individual three-port output transformer which is used for both high-voltage conversion and low-voltage conversion (12V). 10) Appliance (A) according to claim 9, characterized by the fact that at least one of either said first single-phase batery charger (OBC1), said second single-phase batery charger (OBC2) or said third single-phase batery charger (OBC3) comprises:- an individual filter (F) connected to said switching matrix (SWM); - a Power Factor Correction (PFC) module connected to said filter (F);- an individual low-voltage and high-voltage converter (CNV), consisting of an individual transformer comprising an individual primary side (CNV PS) connected to the PFC module, a first secondary side (HV CNV SS) connected to the high-voltage output / input (HVDC) connected to one of the electric bateries (Bl, B2), and a second secondary side (LV CNV SS) connected to the low-voltage output (LVDC), for the power supply of the low- voltage circuits (12 V) of the electric vehicle.

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