Control of an electric circuit in a motor vehicle

Abstract

A method (200) for operating an electrical vehicle circuit (115) of a motor vehicle (105) includes determining that a voltage of the vehicle circuit (115) drops below a predetermined threshold value while electric current from the vehicle circuit (115) flows through a consumer (130) on board the motor vehicle (105), lowering a voltage present at the consumer (130) in order to reduce the current flowing through the consumer (130), and successively raising the voltage present at the consumer (130).

Claims

1. A method (200) for operating an electrical vehicle circuit (115) of a motor vehicle (105), comprising: determining (205) that a voltage of the vehicle circuit (115) is below a predetermined threshold value while electric current from the vehicle circuit (115) flows through a consumer (130) on board the motor vehicle (105); lowering (210) a voltage present at the consumer (130) in order to reduce the current flowing through the consumer (130); and continuously raising (220) the voltage present at the consumer (130) at a predetermined rate of change.

2. The method (200) of claim 1, wherein the continuously raising (220) comprises continuously raising (220) the voltage present at the consumer (130) when the voltage of the vehicle circuit (115) is above the predetermined threshold value.

3. The method (200) of claim 1, wherein the continuously raising (220) comprises continuously raising (220) the voltage present at the consumer (130) from a value of about zero.

4. The consumer (200) of claim 1, wherein the continuously raising (220) comprises continuously raising (220) the voltage present at the consumer (130) until the current flowing through the consumer (130) reaches a predetermined value.

5. The method (200) of claim 1, wherein the continuously raising (220) comprises continuously raising (220) the voltage present at the consumer (130) only when the voltage of the vehicle circuit (115) is greater than the predetermined threshold value by a predetermined amount.

6. The method (200) of claim 1, wherein the continuously raising (220) comprises continuously raising (220) the voltage present at the consumer (130) at most to a predetermined value.

7. The method (200) of claim 1, wherein a maximum current flowing through the consumer (130) exceeds a predetermined value.

8. A control device (110) for an electrical vehicle circuit (115) of a motor vehicle (105), comprising: a voltage controller (150) for providing a voltage for a consumer (130) from the vehicle circuit (115); a scanning unit (140) for determining a voltage of the vehicle circuit (115); and a processing unit (135) configured for determining that the voltage of the vehicle circuit (115) has fallen below a predetermined threshold value, lowering the voltage provided to the consumer (130) in order to reduce a current flowing from the vehicle circuit (115) through the consumer (130), and continuously raising the voltage provided to the consumer (130) at a predetermined rate.

9. The control device (110) of claim 8, wherein the processing unit (135) configured for continuously raising the voltage provided to the consumer (130) when the voltage of the vehicle circuit (115) is above the threshold value.

10. The control device (110) of claim 8, further comprising an additional scanning unit (145) for determining the current flowing through the consumer (130).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Example aspects of the invention will now be described more precisely with reference to the attached figures, in which:

(2) FIG. 1 shows a system according to an example embodiment; and

(3) FIG. 2 shows a flow chart of a method according to an example embodiment.

DETAILED DESCRIPTION

(4) Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.

(5) FIG. 1 shows a system 100, which encompasses a motor vehicle 105 and a control device 110. An electrical vehicle circuit 115 is provided on board the motor vehicle 105, which is usually supplied from a chargeable energy accumulator 120 and/or a generator 125, which can be driven, for example, by a drive motor. The vehicle circuit 115 is configured for providing current of a predetermined voltage, the power supply voltage, to one or multiple consumers 130 on board the motor vehicle 105. The power supply voltage is usually a DC voltage having a nominal value of, for example, approximately twelve volts (12 V). A valid range of the power supply voltage can lie in a predetermined range around the nominal value, for example, approximately no less than eleven and eight-tenths of volt and no greater than twelve and three-tenths of volt (11.8 V-12.3 V). An undervoltage of the power supply voltage can be tolerated up to a predetermined threshold value, which is usually below the aforementioned range. If the power supply voltage should fall below the threshold value, it is provided to reduce an electrical load on the vehicle circuit 115. A typical threshold value in the case of a nominal power supply voltage of twelve volts (12 V) is approximately eleven volts (11 V).

(6) A consumer 130 represented by way of example can be controlled, by way of an open-loop system, with the aid of the control device 110, in that a voltage present at the consumer 130 can be changed. The consumer 130 has a voltage-dependent current draw and is usually configured for drawing a substantial amount of electrical energy from the vehicle circuit 115. The consumer 130 considered in this case is preferably not safety-critical; the motor vehicle 105 can therefore be safely operated even if the consumer 130 operates, at least briefly, only with reduced power or not at all. During normal operation, the consumer 130 is usually operated directly from the power supply voltage of the vehicle circuit 115. If the consumer 130 should internally require a voltage higher than the power supply voltage, it is assumed in this case that the consumer 130 includes an appropriate voltage converter (step-up converter).

(7) The control device 110 preferably includes a processing device 135, further preferably a first scanning unit 140 for scanning a voltage of the vehicle circuit 115, such as a voltage sensor, and/or a second scanning unit 145 for scanning a current flowing through the consumer 130, such as a current sensor. The control device 110 also includes a voltage controller 150, which is configured for controlling, by way of an open-loop system, a voltage present at the consumer 130 continuously or in discrete steps, in order to influence a current flowing through the consumer 130.

(8) It is provided that the control device 110 sharply reduces the voltage present at the consumer 130 as soon as the power supply voltage of the vehicle circuit 115 drops below an aforementioned, predetermined threshold value. Thereafter, the voltage at the consumer 130 is to be successively raised. However, the raising should take place only to the point at which one or multiple predetermined conditions are met. Such a condition can be that the power supply voltage is above a further predetermined threshold value, which can be slightly above the aforementioned threshold value. Another condition can be met, provided a current flowing through the consumer 130 does not exceed a predetermined threshold value. This threshold value can be determined as a function of the power supply voltage before or after the determination of the undervoltage.

(9) FIG. 2 shows a flow chart of a method 200 for the control, by way of an open-loop system, of a consumer 130, which is mounted on board a motor vehicle 130 and is supplied with electrical energy from a vehicle circuit 115. The method 200 can be carried out, in particular, with the aid of a control device 110.

(10) In a step 205, it can be determined that the voltage of a vehicle circuit 115 is below a predetermined threshold value. This is also referred to as an undervoltage of the vehicle circuit 115. If the power supply voltage of the vehicle circuit 115 is above the threshold value, the step 205 can be repeated any number of times.

(11) If the power supply voltage is below the threshold value, in a step 210, a voltage present at the consumer 130 can be reduced. The reduction preferably takes place by at least fifty percent (50%), preferably at least eighty percent (80%), and in a further preferred embodiment by one hundred percent (100%), i.e., corresponding to a shut-off of the consumer 130. After the reduction, a wait for a predetermined time can ensue before the next step is carried out. The predetermined time can be fixedly associated with the consumer 130. If multiple consumers 130 connected to the vehicle circuit 115 are controlled, by way of an open-loop system, in a way described herein, the predetermined times can be selected, in particular, to be different, so that the following steps can be carried out staggered in time for the various consumers 130.

(12) In a subsequent step 215, one or multiple criteria can be checked. The criterion indicates whether the voltage present at the consumer 130 can be raised or not. A possible criterion is met if the current flowing from the vehicle circuit 115 through the consumer 130 is below a predetermined threshold value. Another possible criterion is met if the voltage of the vehicle circuit 115 is above a predetermined threshold value, which can be above the threshold value in step 205.

(13) If at least one of the checked criteria is not met, the method 200 can end or start over from the beginning. Otherwise, if all criteria have been met, the voltage present at the consumer 130 can be raised in a step 220. The raising preferably takes place by a predetermined amount, which can be, for example, in the range of approximately a tenth of a volt (0.1 V). The voltage can also be continuously raised, for example, at a predetermined rate of change.

(14) In a step 225, a check can then be carried out to determine whether the voltage present at the consumer 130 has reached a predetermined value. This value can correspond, in particular, to the power supply voltage or can be below this by a predetermined amount. The value can also be fixedly predetermined, however. If the value has been reached, the power reduction of the consumer 130 can be considered to have ended. The method 200 can end or start over.

(15) Otherwise, if the voltage at the consumer 130 has not reached the value, the consumer 130 is operated further with reduced voltage and, therefore, with reduced current. In this case, the method 200 can return to step 215, in order to check a possible raising of the voltage. The method 200 can also return to the start, however, in order to check in advance whether another reduction of the voltage is necessary.

(16) Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.

REFERENCE NUMBERS

(17) 100 system 105 motor vehicle 110 control device 115 electrical vehicle circuit 120 energy accumulator 125 generator 130 consumer 135 processing device 140 first scanning unit (voltage of the vehicle circuit) 145 second scanning unit (current through the consumer) 150 voltage controller 200 method 205 determine undervoltage 210 lower voltage at the consumer 215 criterion met? 220 raise voltage 225 voltage normal?