Battery charging system with an on-board charger

Abstract

A battery charging system of a vehicle and method for charging a low-voltage battery from a high-voltage battery or an external power supply are provided, where the battery charging system includes an on-board charger (OBC) to charge the low voltage battery either from the high-voltage battery or from the external power supply, and the OBC is powered either by the low-voltage battery or the external power supply.

Claims

1. A battery charging system for a vehicle, comprising: an on-board charger configured to be connected to an external power supply, the on-board charger including a charging DC/DC converter, a high voltage battery connected to an output of the charging DC/DC converter, the high voltage battery configured to be charged by the on-board charger when connected to the external power supply; a high power DC/DC converter connected to the high voltage battery; a low voltage battery configured to be charged by the external power supply; and a low power DC/DC converter adapted to operate in a first and a second mode of operation, wherein the low power DC/DC converter in the first mode of operation is connected to an input of the charging DC/DC converter and in the second mode of operation is connected to the output of the charging DC/DC converter; wherein the low voltage battery is configured to be charged by the external power supply via the on-board charger when the low power DC/DC converter is in the first mode of operation, and configured to be charged by the high voltage battery when the low power DC/DC converter is in the second mode of operation.

2. The battery charging system of claim 1, wherein the on-board charger comprises a power factor correction circuit, wherein an input of the power factor correction circuit is connected to an external power input and an output of the power factor correction circuit is connected to the input of the charging DC/DC converter.

3. The battery charging system of claim 1, wherein the low power DC/DC converter is connected to a switch having a first position for connecting the low power DC/DC converter to the input of the charging DC/DC converter and a second position for connecting the low power DC/DC converter to the output of the charging DC/DC converter; wherein the low voltage battery is configured to be charged by the external power supply via the on-board charger when the switch is in the first position, and configured to be charged by the high voltage battery when the switch is in the second position.

4. The battery charging system of claim 3, wherein the on-board charger further comprises a control unit for providing control logic to control the switch.

5. The battery charging system of claim 4, wherein the on-board charger further comprises an AC/DC converter for supplying DC voltage to the control unit.

6. The battery charging system of claim 1, wherein the on-board charger further comprises an external power input having its input adapted to be connected to the external power supply.

7. The battery charging system of claim 6, wherein the on-board charger circuit further comprises a power factor correction circuit having its input connected to the external power input and its output connected to the input of the charging DC/DC converter.

8. The battery charging system of claim 4, wherein the control unit supplies the control logic to power a battery management control logic unit.

9. The battery charging system of claim 1, wherein the battery charging system is installed in a plug-in hybrid or electric vehicle.

10. The battery charging system of claim 3, wherein the low power DC/DC converter is directly connected to the output of the power factor correction circuit.

11. A method for operating an on-board charger of a vehicle, comprising the steps of: providing an on-board charger including a charging DC/DC converter and a low power DC/DC converter adapted to operate in a first and a second mode of operation; providing a high voltage battery connected to an output of the charging DC/DC converter, a high power DC/DC converter connected to the high voltage battery, and a low voltage battery; connecting the on-board charger to an external power supply so as to charge the high voltage battery and the low voltage battery, the low voltage battery being charged when the low power DC/DC converter operates in the first mode of operation; and disconnecting the on-board charger circuit from the external power supply, wherein the low voltage battery is configured to be charged by the high voltage battery when the low power DC/DC converter operates in the second mode of operation.

12. The method for operating an on-board charger of a vehicle according to claim 11, comprising the step of connecting the low power DC/DC converter to a switch having a first position for connecting the low power DC/DC converter to an input of the charging DC/DC converter in the first mode of operation and a second position for connecting the low power DC/DC converter to the output of the charging DC/DC converter in the second mode of operation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing FIGURES wherein like reference character denote corresponding parts throughout the several views and wherein:

(2) FIG. 1 is a schematic block diagram of a battery charging system including an on-board charger (OBC) circuit according to the subject invention.

DEFINITIONS

(3) The subject invention is most clearly understood with reference to the following definitions:

(4) As used in the specification and claims, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, it is noted that a plurality of high-voltage batteries may be provided in an electric vehicle according to the subject invention, although the term “a” or “the” high-voltage battery is used throughout the present application.

(5) Also, it will be understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

(6) It will be further understood that the term “vehicle” or similar term as used herein includes motor vehicles such as sports utility vehicles (SUV), buses, trucks, commercial vehicles, watercraft including boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

DETAILED DESCRIPTION OF THE INVENTION

(7) Referring to FIG. 1, a block diagram of a battery charging system, generally designated 1, including an on-board charger (OBC) 10 is depicted according to the subject invention. As shown in FIG. 1, various components of the OBC 10 are encircled by a dotted line, thereby separating the OBC 10 from other components of the battery charging system 1. The battery charging system preferably includes at least a high-voltage battery 2, a low-voltage battery 3, and an external power input 11 that can be coupled to an external power supply (e.g., a public power grid, not shown) for charging the high-voltage battery 2 and/or the low-voltage battery 3, where the external power input 11 may be part of the OBC

(8) As shown in FIG. 1, an input of the external power input 11 is configured to be connected to an external power supply, and an output of the external power input 11, i.e., an AC connection, is connected to a power factor correction (PFC) circuit 12. The PFC circuit 12 is adapted to adjust the power factor of the output to improve efficiency of the system, as is well known by the person of ordinary skill in the art. The PFC circuit 12 comprises a rectifier to convert the AC voltage from the external power input into a DC voltage. The output from the PFC circuit 12 is a DC voltage (high voltage) which is fed to the input of a charging DC/DC converter 13 for converting the high voltage from the PFC circuit 12 into a high voltage which corresponds to the DC high voltage required to cause current to flow into the high-voltage battery 2.

(9) As further shown in FIG. 1, a “second” DC/DC converter (low-power DC/DC converter) 14 is integrated into the battery charging system. The low-power DC/DC converter 14 is also referred to herein as the “second” DC/DC converter to distinguish from a “first” or high-power DC/DC converter used to supply DC power to the high-voltage battery 2. The second DC/DC converter 14 can be connected, for example, via a switch 15, either to a first position (a) at the output side of the PFC 12 or to a second position (b) at the input side of the high-voltage battery 2 via a high-voltage rail 4. In particular, if the switch 15 is closed such that the low-power DC/DC converter 14 is connected to the PFC 12, the low-power DC/DC converter 14 would be coupled to the external power input 11, and thus to the external power supply. The switch 15 can be controlled by control logic 16 as depicted by the dashed line. It will be understood by one of ordinary skill in the art that it is possible to carry out the function of the switch 15 by one or more switches, or circuit solutions, so as to alternate the energy source for the low power DC/DC converter 14 between (1) the PFC 12, and (2) the high-voltage rail and the high-voltage battery 2. As described above, the output voltage from the PFC 12 preferably is a DC voltage, and therefore no additional AC/DC converter is required between the external power supply and the low-power DC/DC converter 14 in order to supply a DC voltage to the second DC/DC converter 14.

(10) Thus, according to the subject invention, the number of components required for the battery charger system can be reduced. Further, the architecture of the second low-power DC/DC converter 14 can be optimized to supply the internal low voltage control logic 16, charge the low-voltage battery 3, and provide power to optional auxiliary loads 14 and other low voltage supply logic 8, in the most efficient manner.

(11) In operation, when the vehicle is connected to an external power supply, the external power input 11 is connected to the external power supply (e.g., a public AC power grid having 1-3 phases and a voltage of 380 volts, 220 volts, or 110 volts, for example). The AC high-voltage is fed from the external power input 11 to the PFC 12, where the DC voltage output from the PFC 12 is regulated in the high-voltage charging DC/DC 13 and fed to the high-voltage battery 2 for charging the high-voltage battery 2. Necessary synchronization between the high-voltage charging DC/DC 13 and the high voltage battery 2 is handled over a communication bus 5, e.g., to manage charge levels and on/off conditions.

(12) If the vehicle remains connected to the external power supply via the external power input 11 but charging of the high voltage battery 2 is not desired, the high voltage battery 2 can be internally disabled and the switch 15 be set to the (a) position. Thereby, the low-voltage battery 3 and/or the auxiliary loads 14 (e.g. lights, ventilation, etc.) can be powered from the external power supply (i.e. the external power input 11 via the PFC 12 and the low-power DC/DC converter 14) without having to power/operate the high-power system, and without draining power from the high-voltage battery 2. This is an important feature in case the battery charging system is connected to the public power grid for a longer period of time than necessary to charge the high-voltage battery 2 (e.g., several days).

(13) On the other hand, if the external power input 11 is disconnected or otherwise disabled by a timer, for example, the switch 15 is set to the (b) position and continues to provide power to the low-voltage battery 3 from the high voltage battery 2 via a low voltage rail 7 through the low power DC/DC converter 14 without having to engage a less efficient, high power DC/DC converter 16. Therefore, in-vehicle low power supplied functions are available in an energy-efficient way because of the optimized design of the low power DC/DC converter 14 and the OBC.

(14) As shown, the OBC includes the control logic 16 being connected to the switch 15. The control logic 16 is further connected to the input side of the on-board charger thus receiving power from the external power supply via the external power input 11. That is, the control unit 16 is connected, via an AC/DC converter 17 (rectifier), to the external power input 11. The control logic 16 is also supplied from the low-voltage rail, such that the AC/DC converter 17 can be small and efficiently adapted to serve the control logic 16 only. Thus, a control unit that supplies the control logic 16 can be powered from the low-voltage battery 3 or from the external power supply via the AC/DC converter 17 whenever it is available. The supply from the external power supply (i.e., via the external power input 11) is especially advantageous when both batteries (the high-voltage battery 2 and the low-voltage battery 3) are empty to such a degree that the OBC control logic (or control unit) 16 cannot be powered by the almost empty batteries as a power source.

(15) For example, the battery charging system is operable in at least the following two stages. In a first stage (when both batteries are almost empty), the control logic 16 (powered by the external power supply 11) can provide energy to a low-voltage supplied high-voltage battery management control logic 8 to enable a charging process of the high-voltage battery 2, as opposed to when the low-voltage battery 3 is drained and thus there is no power available for the control logic 16. In a second stage, the control logic 16 can then, for a period of time, switch to charge the low-voltage battery 3 from the high voltage rail and the low-power DC/DC converter 14. By the above operation, it also can be assured that the low-voltage battery 3 is not drained when the vehicle is not driven and connected to an external power supply (e.g., a charging station) for a long period of time and when, for example, a starter circuit of the vehicle is coupled to the low-voltage battery.

(16) According to a further operation, when the vehicle is being driven, upon failure of the high power DC/DC converter 16, the system could be controlled so as to run critical auxiliary loads (e.g., lights) in an emergency mode ensuring they are fed energy by at least periodically connect low-power DC/DC converter 14 to the high-voltage rail and high voltage battery 2.

(17) According to yet a further operation, when auxiliary loads, such as radios, are in use at a vehicle stand still, the high power DC/DC converter 16 does not have to be activated since the low-power DC/DC converter 14 can be directly connected to the high-voltage rail and the high-voltage battery 2 and/or directly to the external grid during charging without activating the high-power system components via the PFC 12.

(18) Although preferred embodiments of the invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims. Thus, although a switch is described as the means of switching between the operation of the external power input and the high voltage rail, it will be realized that the term “switch” should be interpreted broadly, including any means that switches the operation between these two modes.