System and method for controlling a low voltage DC-DC converter for a hybrid vehicle

Abstract

The present invention relates to a system and method for controlling a low-voltage DC-DC converter of a hybrid vehicle, the control method comprising: determining whether a cold start occurs in the hybrid vehicle based on the size and change rate of a detection value obtained by detecting the voltage of an auxiliary battery; a first adjustment operation, wherein, when it is determined in the determination process that a cold start occurs, an output voltage command of the low-voltage DC-DC converter is set to a value substantially the same as the detection value, thereby adjusting the output voltage of the low-voltage DC-DC converter; and a second adjustment operation, wherein the output voltage command is adjusted based on whether the detection value increases or decreases and a comparison result between the detection value and the value of the output voltage command, thereby adjusting the output voltage of the low-voltage DC-DC converter.

Description

Technical Field

[0001] The present invention relates to a system and method for controlling a low-voltage DC-DC converter of a hybrid vehicle, and more particularly, to a system and method for controlling a low-voltage DC-DC converter of a hybrid vehicle that can control the output of the low-voltage DC-DC converter during a cold start of the hybrid vehicle, thereby stably managing the hybrid vehicle. Background Art

[0002] A hybrid vehicle has an engine and an electric motor as power sources of the vehicle, and includes a high-voltage main battery for supplying power to the electric motor and an auxiliary battery for supplying power to the electrical loads of the vehicle. A low voltage DC-DC converter (LDC) is provided between the main battery and the auxiliary battery, and the LDC is used to convert the high voltage power output from the main battery into a low voltage and provide the low voltage power as charging power for the auxiliary battery or provide the low voltage power as power for the electrical loads.

[0003] The hybrid vehicle includes an engine, and therefore, since the starter motor needs to be operated when the engine is started, a cold start phenomenon in which the voltage of the auxiliary battery drops suddenly occurs. When the engine is started, since the starter motor consumes a large amount of power of the auxiliary battery in a short time, a cold start phenomenon in which the voltage of the auxiliary battery drops suddenly occurs. In this case, if the LDC performs conventional output voltage control, there is a problem that when the voltage of the auxiliary battery drops suddenly, an overcurrent is supplied from the LDC to the auxiliary battery.

[0004] In addition, if a difference occurs between the output voltage of the auxiliary battery and the voltage of the LDC during cold start, there is a problem that a dimming phenomenon in which the brightness of the headlight of the vehicle changes unstably may occur.

[0005] The contents described herein are only used to help understand the background of the present invention and should not be considered to correspond to the related art known to those of ordinary skill in the art. Summary of the invention

[0006] Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a system and method for controlling a low-voltage DC-DC converter of a hybrid vehicle so as to be able to control the output of the low-voltage DC-DC converter during the cold start of the hybrid vehicle, thereby stably managing the hybrid vehicle.

[0007] According to one aspect of the present invention, the above and other objects can be achieved by a system for controlling a DC-DC converter of a hybrid vehicle, the system comprising: a main battery; a DC-DC converter configured to step down and output the voltage of the main battery; an auxiliary battery connected to the output end of the DC-DC converter; a voltage sensor configured to detect the voltage of the auxiliary battery; and a controller configured to determine whether a cold start occurs in the hybrid vehicle based on a detection value of the voltage of the auxiliary battery detected by the voltage sensor, and to adjust the DC-DC converter based on the detection value when a cold start occurs in the hybrid vehicle.

[0008] According to an embodiment of the present invention, the controller can determine that a cold start has occurred when the detection value decreases at a rate greater than a preset reference change rate per unit time, and the detection value maintains a preset reference voltage or lower voltage for a preset reference time or longer.

[0009] According to an embodiment of the present invention, when it is determined that a cold start has occurred, the controller can be configured to adjust the output voltage of the DC-DC converter by setting the output voltage command of the DC-DC converter to a value substantially the same as the detection value, and the output voltage of the DC-DC converter can be adjusted.

[0010] According to an embodiment of the present invention, when it is determined that a cold start has occurred, the controller can be configured to: in a state where the detection value is increasing, when the output voltage command is less than or equal to the detection value, increase the output voltage command of the DC-DC converter at a preset first change rate per unit time; and can be configured to: in a state where the detection value is increasing, when the output voltage command of the DC-DC converter is greater than the detection value, increase the output voltage command at a preset second change rate per unit time, the value of the preset second change rate per unit time being less than the value of the first change rate per unit time.

[0011] According to an embodiment of the present invention, when it is determined that a cold start has occurred, the controller may be configured to derate the DC-DC converter when the DC-DC converter outputs an overcurrent greater than a preset reference value while the detection value is decreasing.

[0012] According to an embodiment of the present invention, when it is determined that a cold start has occurred, the controller may be configured to maintain the output voltage command when the DC-DC converter does not output an overcurrent greater than a preset reference value while the detection value is decreasing.

[0013] According to an embodiment of the present invention, the DC-DC converter may be a low voltage DC-DC converter.

[0014] According to another aspect of the present invention, the above and other purposes can be achieved by a method for controlling a DC-DC converter of a hybrid vehicle, wherein the hybrid vehicle includes a DC-DC converter configured to step down the voltage of a main battery and output the stepped-down voltage to an auxiliary battery and an electrical load, the method comprising: determining whether a cold start occurs in the hybrid vehicle based on a detection value obtained by detecting the voltage of the auxiliary battery and a rate of change of the detection value; a first adjustment operation, wherein, when a cold start is determined to have occurred during the determination process, the output voltage of the DC-DC converter is adjusted by setting the output voltage command of the DC-DC converter to a value substantially the same as the detection value; and a second adjustment operation, wherein the output voltage of the DC-DC converter is adjusted by adjusting the output voltage command based on whether the detection value increases or decreases and a comparison result between the detection value and the value of the output voltage command.

[0015] According to an embodiment of the present invention, determining whether a hybrid vehicle has a cold start may include: determining that a cold start has occurred when the detection value decreases at a rate greater than a preset reference change rate per unit time, and the detection value maintains a preset reference voltage or a lower voltage for a preset reference time or longer.

[0016] According to an embodiment of the present invention, the first adjustment operation may include: in a state where the detection value is increasing, when the output voltage command is less than or equal to the detection value, increasing the output voltage command of the DC-DC converter at a preset first change rate per unit time; in a state where the detection value is increasing, when the output voltage command of the DC-DC converter is greater than the detection value, increasing the output voltage command at a preset second change rate per unit time, the value of the preset second change rate per unit time being less than the value of the first change rate per unit time.

[0017] According to an embodiment of the present invention, the second adjustment operation may include: when the DC-DC converter outputs an overcurrent greater than a preset reference value in a state where the detection value is reduced, de-rating the DC-DC converter.

[0018] According to an embodiment of the present invention, the second adjustment operation may include: maintaining the output voltage command when the DC-DC converter does not output an overcurrent greater than a preset reference value in a state where the detection value is reduced.

[0019] According to an embodiment of the present invention, the DC-DC converter may be a low voltage DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and other advantages of the present invention will be more clearly understood through the following detailed description presented in conjunction with the accompanying drawings, in which:

[0021] Figure 1 is a block diagram showing a configuration of a control system of a low voltage DC-DC converter (LDC) of a hybrid vehicle according to an embodiment of the present invention;

[0022] Figure 2 is a flowchart illustrating a method of controlling an LDC of a hybrid vehicle according to an embodiment of the present invention; and

[0023] Figure 3 is a graph showing an example of an output voltage command of an LDC adjusted according to a detected voltage of an auxiliary battery in a system and method for controlling an LDC of a hybrid vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Hereinafter, a system and method of controlling a low voltage DC-DC converter of a hybrid vehicle according to an exemplary embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

[0025] Figure 1 is a block diagram showing a configuration of a control system of a low voltage DC-DC converter of a hybrid vehicle according to an embodiment of the present invention.

[0026] Reference Figure 1 According to various embodiments of the present invention, a control system of a low voltage DC-DC converter of a hybrid vehicle may include a main battery 20, a low voltage DC-DC converter (LDC) 10, an auxiliary battery 30, a voltage sensor 40 and a controller 100; the low voltage DC-DC converter (LDC) 10 is used to step down the voltage of the main battery 20 and output the stepped-down voltage; the auxiliary battery 30 is connected to the output terminal of the LDC 10; the voltage sensor 40 is used to detect the voltage of the auxiliary battery 30; the controller 100 is used to determine whether a cold start occurs in the hybrid vehicle based on a detection value of the voltage of the auxiliary battery 30 detected by the voltage sensor 40, and adjust the output of the LDC 10 based on the detection value when a cold start occurs.

[0027] The LDC 10 may be disposed between the main battery 20 and the auxiliary battery 30. The auxiliary battery 30 may be a battery that outputs a relatively low voltage compared to the voltage output by the main battery 20, and the relatively low voltage is used to provide power to various electrical loads 50 of vehicle applications. The main battery 20 may be a battery that outputs a relatively high voltage compared to the voltage output by the auxiliary battery 30, and the relatively high voltage is used to provide power to a driving motor that drives the vehicle. The LDC 10 may step down the high voltage power of the main battery 20 to output low voltage power.

[0028] The LDC 10 may be connected to the auxiliary battery 30 and the electrical load 50, including but not limited to the starter motor, at one node using a component such as a junction box 60. That is, the output voltage and output current of the LDC 10 may be provided as a charging voltage and a charging current of the auxiliary battery 30 through the junction box 60, and may also be provided as power for the electrical load 50. The power stored in the auxiliary battery 30 may also be provided to the electrical load 50 through the junction box 60.

[0029] The voltage sensor 40 may be a component for generating a voltage detection value obtained by detecting the voltage of the auxiliary battery 30. The voltage sensor 40 may employ various known sensors. Figure 1 An example of applying an intelligent battery sensor (IBS) as a voltage sensor is shown.

[0030] The controller 100 may be a microcontroller including a processor and a memory. The processor is used to execute a control algorithm for implementing various embodiments of the present invention. The memory is implemented as a non-transitory computer-readable medium, for example, to store various information required by the control algorithm.

[0031] The controller 100 can generate an output voltage command (which is used to control the output voltage of the LDC 10), and can generate a pulse width modulation (PWM) signal (which is used to drive a switching device in the LDC 10), and can also output the PWM signal to the LDC 10 so that the LDC 10 can output a voltage corresponding to the output voltage command.

[0032] PWM control of the switching device of the LDC 10 may correspond to a known technology in the field of converters, and a PWM integrated circuit (IC) for generating a PWM signal may be presented in the form of a commercial product, and thus, a detailed description thereof is omitted.

[0033] Specifically, various embodiments of the present invention relate to a scheme for adjusting the output voltage of the LDC 10 (i.e., the output voltage command of the LDC 10) when a cold start occurs in which a voltage sag is maintained for a relatively long time, with respect to the starter motor 50, which is one of the electrical loads connected to the auxiliary battery 30, causing the voltage of the auxiliary battery 30 to drop during the engine start of the hybrid vehicle. For the engine start at a lower temperature, it may take longer than the engine start at a higher temperature. Therefore, when a cold start occurs and the starter motor 50 is running, the time for the auxiliary battery 30 to maintain a voltage lower than a preset value may be extended. According to various embodiments of the present invention, when such a cold start occurs, a safe vehicle state can be maintained by appropriately adjusting the output voltage command of the LDC 10.

[0034] Through the description of the method of controlling a low voltage DC-DC converter (LDC) according to an embodiment of the present invention, the operation and effects of the control system of the low voltage DC-DC converter of a vehicle according to an embodiment of the present invention having the aforementioned configuration will be more clearly understood.

[0035] Figure 2 is a flowchart illustrating a method of controlling an LDC of a hybrid vehicle according to an embodiment of the present invention. Figure 3 is a graph showing an example of an output voltage command of an LDC adjusted according to a detected voltage of an auxiliary battery in a system and method for controlling an LDC of a hybrid vehicle according to an embodiment of the present invention.

[0036] Reference Figure 2 In the method of controlling the LDC of a hybrid vehicle according to an embodiment of the present invention, when vehicle starting begins (S11), the controller 100 can determine whether a cold start occurs based on the size and change rate of the detection value obtained by detecting the voltage of the auxiliary battery 30 by the voltage sensor 40 (S12).

[0037] More specifically, in step S12, when the detected value of the voltage of the auxiliary battery 30 (which is detected by the voltage sensor 40) decreases at a rate greater than a preset reference change rate per unit time, and the detected voltage of the auxiliary battery 30 remains at a preset reference value or lower for a preset reference time or longer, the controller 100 can determine that a cold start has occurred.

[0038] In step S12, when it is determined that a cold start has occurred, the controller 100 may set the output voltage command of the LDC 10 to a value substantially the same as the detected value of the voltage of the auxiliary battery 30, which is detected by the voltage sensor 40. In this way, when a cold start occurs, overcurrent generated by suddenly applying a high voltage to the auxiliary battery 30 having a low voltage by the LDC 10 can be prevented, thereby protecting the auxiliary battery 30.

[0039] Reference Figure 3 , from time T 0 To time T 1 , the controller 100 can determine whether a cold start has occurred, and at time T 1 An output voltage command of the LDC 10 that is substantially the same as the voltage of the auxiliary battery 30 may be generated.

[0040] Here, when the output voltage command is substantially the same as the voltage of the auxiliary battery, it does not mean that the output voltage command completely corresponds to the voltage of the auxiliary battery in terms of value, but rather means that the output voltage command is a value within a specific range around the voltage of the auxiliary battery, which can achieve an effect equivalent to that to be achieved by generating the output voltage command as a value completely corresponding to the voltage of the auxiliary battery. In one example, the specific range may be a preset range or a default range.

[0041] Subsequently, in step S13, after setting the output voltage command of the LDC 10 to the same value or substantially the same value as the detected value of the voltage of the auxiliary battery 30 (which is detected by the voltage sensor 40), the controller 100 may check whether the detected value of the voltage of the auxiliary battery 30 increases or decreases (S14).

[0042] When the detected voltage of the auxiliary battery 30 decreases, although not shown, it can be determined whether an overcurrent is generated by a current sensor installed at the output terminal of the LDC 10 (S15), and when an overcurrent is generated, the output current of the LDC 10 can be reduced by derating the operation of the LDC 10 (S16), thereby protecting the auxiliary battery 30.

[0043] In step S15, when the LDC 10 does not output an overcurrent, the output voltage command set in step S13 may be maintained (S17).

[0044] In step S14 , when the detected voltage of the auxiliary battery increases, the controller 100 may compare the voltage command of the LDC 10 with the detected value of the voltage output by the voltage sensor 40 ( S18 ).

[0045] As a result of the comparison of step S18, when the output voltage command of the LDC 10 is less than or equal to the detected value of the voltage of the auxiliary battery 30, the output voltage command of the LDC 10 may be increased at a preset first change rate "slope B" per unit time (S19).

[0046] As a result of the comparison in step S18, when the output voltage command of the LDC 10 is greater than the detected value of the voltage of the auxiliary battery 30, the output voltage command may be increased at a preset second change rate “slope A” per unit time, the value of the second change rate “slope A” being smaller than the first change rate “slope B” per unit time (S20). The output voltage commands of step S19 and step S20 may be expressed as Figure 3 Time T 1 With T 4 between.

[0047] Here, the first change rate "slope B" per unit time may be a significantly larger change rate per unit time of approximately 5V per second, while the second change rate "slope A" per unit time may be a smaller change rate per unit time of less than 1V per second.

[0048] That is, according to the embodiment of the present invention, when the output voltage command of the LDC 10 is less than the detected value of the voltage of the auxiliary battery 30, the controller 100 may set a larger rate of change per unit time of the voltage command so as to quickly supply power to the auxiliary battery 30 from the LDC 10. When the output voltage command of the LDC 10 is greater than the detected value of the voltage of the auxiliary battery 30, the change in the output voltage command of the LDC 10 may be set to be lower so that the difference with the voltage of the auxiliary battery 30 does not increase, thereby preventing the dimming phenomenon of the headlights from occurring when the voltage of the headlights of the vehicle applied to the electrical load 50 suddenly changes.

[0049] Subsequently, contrary to the judgment performed in step S12, when the detected value of the voltage of the auxiliary battery 30 (which is detected by the voltage sensor 40) decreases at a rate less than a preset reference change rate per unit time, and the detected voltage of the auxiliary battery 30 maintains a preset reference voltage or more for a preset reference time or longer, the controller 100 can determine that the cold start is over and can end the control through the above steps S13 to S20 (S21).

[0050] Of course, the preset reference change rate per unit time, the preset reference time, and the preset reference voltage applied in step S21 may have values ​​different from those in step S12 to determine the end of the cold start.

[0051] As described above, according to various embodiments of the present invention, even in the case where the voltage of the auxiliary battery changes suddenly when a cold start occurs, overcurrent can be prevented from occurring by stably controlling the output of the low voltage DC-DC converter (LDC), and while changing the output voltage command of the LDC in consideration of the change in the voltage of the auxiliary battery when a cold start occurs, the output of the LDC can be adjusted, so that power can be smoothly supplied to the auxiliary battery and the dimming phenomenon of the vehicle's headlights can be prevented.

[0052] A system and method for controlling a low voltage DC-DC converter (LDC) of a hybrid vehicle can stably control the output of the LDC even when the voltage of an auxiliary battery suddenly changes when a cold start occurs, thereby preventing overcurrent from being generated.

[0053] In addition, the system and method for controlling the LDC of a hybrid vehicle can adjust the output of the LDC while changing the output voltage command of the LDC in consideration of the change in battery voltage when a cold start occurs, thereby preventing the vehicle's headlights from dimming.

[0054] Those skilled in the art will appreciate that the effects that can be achieved by the present invention are not limited to the effects that have been specifically described above, and other advantages of the present invention will be more clearly understood through the detailed description.

[0055] Although the exemplary embodiments of the present invention have been described above with reference to the accompanying drawings, it will be understood by those skilled in the art that the present invention may be implemented in various other embodiments without changing the technical concept or features of the present invention.

Claims

1. A system for controlling a DC-DC converter of a hybrid vehicle, the system include: Main battery; A DC-DC converter configured to step down and output the voltage of the main battery; an auxiliary battery connected to the output of the DC-DC converter; a voltage sensor configured to detect a voltage of the auxiliary battery; as well as a controller configured to determine whether a cold start of the hybrid vehicle occurs based on a detection value of a voltage of the auxiliary battery detected by the voltage sensor, and to adjust the DC-DC converter based on the detection value when a cold start of the hybrid vehicle occurs; Wherein, the controller is configured to: when it is determined that a cold start has occurred, adjust the output voltage of the DC-DC converter by setting the output voltage command of the DC-DC converter to a value substantially the same as the detection value; Wherein, the controller is configured as follows: when it is determined that a cold start has occurred, in a state where the detection value is increased, when the output voltage command is less than or equal to the detection value, the output voltage command of the DC-DC converter is increased at a preset first change rate per unit time; in a state where the detection value is increased, when the output voltage command of the DC-DC converter is greater than the detection value, the output voltage command is increased at a preset second change rate per unit time, and the value of the preset second change rate per unit time is less than the value of the first change rate per unit time.

2. The system for controlling a DC-DC converter of a hybrid vehicle according to claim 1, in, The controller determines that a cold start has occurred when the detection value decreases at a rate greater than a preset reference change rate per unit time and the detection value maintains a preset reference voltage or lower for a preset reference time or longer.

3. The system for controlling a DC-DC converter of a hybrid vehicle according to claim 1, in, The controller is configured to, when it is determined that a cold start has occurred, derate the DC-DC converter when the DC-DC converter outputs an overcurrent greater than a preset reference value in a state where the detection value is reduced.

4. The system for controlling a DC-DC converter of a hybrid vehicle according to claim 1, in, The controller is configured to maintain an output voltage command of the DC-DC converter when the detection value decreases and the DC-DC converter does not output an overcurrent greater than a preset reference value when it is determined that a cold start has occurred.

5. The system for controlling a DC-DC converter of a hybrid vehicle according to claim 1, in, The DC-DC converter is a low voltage DC-DC converter.

6. A method of controlling a DC-DC converter of a hybrid vehicle, the DC-DC converter being configured to step down a voltage of a main battery and output the stepped-down voltage to an auxiliary battery and an electrical load, the method include: determining whether a cold start of the hybrid vehicle occurs based on a detection value obtained by detecting a voltage of the auxiliary battery and a rate of change of the detection value; a first regulating operation, wherein, when it is determined that a cold start has occurred, an output voltage command of the DC-DC converter is set to a value substantially the same as the detection value, thereby regulating the output voltage of the DC-DC converter; a second adjustment operation, wherein the output voltage command is adjusted based on whether the detection value increases or decreases and a comparison result between the detection value and the value of the output voltage command, thereby adjusting the output voltage of the DC-DC converter; Among them, the first adjustment operation includes: when the detection value is increased, when the output voltage command is less than or equal to the detection value, increasing the output voltage command of the DC-DC converter at a preset first change rate per unit time; when the detection value is increased, when the output voltage command of the DC-DC converter is greater than the detection value, increasing the output voltage command at a preset second change rate per unit time, and the value of the preset second change rate per unit time is less than the value of the first change rate per unit time.

7. The method according to claim 6, in, Determining whether a cold start occurs in the hybrid vehicle includes determining that a cold start occurs when the detection value decreases at a rate greater than a preset reference change rate per unit time and the detection value maintains a preset reference voltage or lower for a preset reference time or longer.

8. The method according to claim 6, in, The second adjustment operation includes: when the DC-DC converter outputs an overcurrent greater than a preset reference value in a state where the detection value is reduced, de-rating the DC-DC converter.

9. The method according to claim 6, in, The second adjustment operation includes maintaining the output voltage command when the DC-DC converter does not output an overcurrent greater than a preset reference value in a state where the detection value is reduced.

10. The method according to claim 6, in, The DC-DC converter is a low voltage DC-DC converter.

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