GB2329082A

GB2329082A - Multiplexed power control system for a motor vehicle; load shedding

Info

Publication number: GB2329082A
Application number: GB9818615A
Authority: GB
Inventors: Hans-Georg Weil
Original assignee: Sumitomo Electric Bordnetze GmbH
Current assignee: Sumitomo Electric Bordnetze GmbH
Priority date: 1997-08-28
Filing date: 1998-08-26
Publication date: 1999-03-10
Anticipated expiration: 2018-08-26
Also published as: FR2767761A1; GB2329082B; FR2767761B1; DE19739410C1; GB9818615D0

Abstract

In order to optimize the conductor cross-section of the power supply line 32 in a sub-region of a motor vehicle having a power-multiplex power distribution and control system, not only loads which are sensitive to a voltage drop (such as various rear lights 11 to 16), but also one or more loads which are tolerant of a voltage drop (such as a rear window heater 17, or wiper motor) are connected downstream of a non-central control unit 26 coupled to the power line 32 and to a data line 31. The cross-section of the power line 32 is such that the maximum voltage drop permissible on the line is not exceeded when all the lights 11 to 16 are operated simultaneously. A programmed controller module (33, Fig.3) associated with the control unit 26, or with a central control unit (2, Fig. 1) monitors the total power requirement currently called for by all the loads connected to control unit 26. If that power requirement is such that the maximum voltage drop on line 32 would be exceeded, one or more of the voltage drop tolerant loads 17 are controlled to reduce the total power requirement. The reduction may be achieved by turning off a voltage drop tolerant load 17 or using a pulse width modulator to operate the load 17 at reduced power.

Description

2329082 ELECTRICAL CIRCUIT ARRANGEMENT The invention relates to an

electrical circuit arrangement particularly for use in the configuration of loads, control units and power-supply lines of an on-board system of a motor vehicle, in a sub-region of an on- board system that is equipped with a powermultiplex system.

The increase in electrical and electronic components in a motor vehicle and the associated increase of line connections can only be handled sensibly by using a multiplex system, which has inter alia a data bus and a power bus, in which case the various electrical and electronic components are activated by way of the common data bus and are supplied with power by way of the common power bus.

Such a power-multiplex system consists of: a comparatively large number of non-central control units, so-called power-multiplex modules; connecting lines having two energy cores and two data cores; an energy store; and the electrical and electronic components, that is, the loads. The electrical and electronic components are then combined to form groups, for example,light--ng in the front region", "lighting in the rear region", "components of the driver's door,, "components of the front seat passenger's door" and such like. Control signals delivered to the data bus activate ',he power loads and trigger certain functions, such as the switching on and off of motors or the switching on or off of lights or heating systems (Journal 0METALL11, 1993, part 1, pages 41 to 45) If applicable, a central control unit can be provided th.t is higher ranking than the non-central control units.

The use of a power-multiplex system results in a reduction in the outlay on cabling and associated weight. For example, the power bus, given a corresponding division of the electrical and electronic is components among the individual non-central control units/modules, can be designed so as to have a uniform conductor cross section of 2.5 MM2 which, when taking the maximum permissible current loading into consideration, renders possible a continuous current of 16A (at 12V) for each module WDIBerichte No. 1009, 1992, pages 121 to 136).

When dimensioning the conductor cross section of the individual connecting lines, it is also to be taken into consideration inter alia that for certain loads, such as in particular the lights, the voltage drop between the energy source/battery and the loads must be maintained at a value that is fixed by relevant regulations, so that the required light intensity is attained. For these loads which are sensitive to a voltage drop, the conductor cross section of the power supply line leading to the non-central control unit is therefore over-dimensioned with regard to the maximum current permissible. It is therefore usual to activate voltage-sensitive loads, such as in particular lights, and loads which are tolerant of a voltage drop, such as for example motors and heating systems, by way of different supply lines and non-central control units/power-multiplex modules respectively. with regard to the activation of motors it is known in this connection that the motor speed can be controlled by clocking the direct voltage that is applied, i- which case a pulse duty factor of 0 - 100 % can be covered by means of so-called PWM timers (journal "Design + ElektronikIl, part 24 of 26.11.1996, pages 22 to 24).

The present invention sc.eks to improve the optimization of the conductor cross section of the powe r supply line required in a sub-region of a motor vehicle on-board system.

According to the present invention, there is provided a circuit arrangement for a sub-region of a motor vehicle on-board system, comprising at least one non-central control unit for coupling loads, including loads which are sensitive to a voltage drop and loads which are tolerant of a voltage drop, which are connected downstream thereof with a common power supply line of a power multiplex system, the electrical cross section of the common power supply line being adapted to the maximum voltage drop permissible for the common operation of the loads which are sensitive to a voltage drop, wherein a device is provided with which the current flow on the common power supply line can be adapted to the maximum voltage drop permissible by monitoring the voltage drop on this line and by activating the loads which are tolerant of a voltage drop in a variable manner.

The configuration of the circuit arrangement provided in accordance with the invention is based on the fact that, as a rule, in any particular subregion of an on-board system only a subset of the voltagesensitive loads are in operation at the same time and that in this state a portion of the power provided for the voltage-sensitive loads can be fed to the loads which are tolerant of a voltage drop. A typical example of this is the rear region of a passenger car which has the rear lights, the numberplate light, the brake lights, the indicators, the reversing light and the fog tail light, on the one hand, and the rear window pane heating system and the wiper motor, on the other hand.

The application of the invention in one particular embodiment of the invention makes it possible to use one single power supply line with a conductnr cross section of 2.5 MM2 in a sub-region of a vehicle onboard system instead of two power supply lines each with, for example, a conductor cross section of 2.5 or instead of a power supply line with a conductor MM2 is cross section of 4 mmI, this resulting in savings in terms of material and weight and also in structural space and greater ease of line-harness handling.

The device provided in accordance with the invention for variable activation of the loads which are tolerant of a voltage drop can be accommodated in a central control unit of the power-multiplex system - if present - or in the non-central control unit (powermultiplex module) responsible for the sub-region in consideration. This - correspondingly programmed electronic device monitors the power requirement currently called for in the sub-region, calculates the voltage drop connected therewith and compares this with the maximum voltage drop permitted. As a function of the result of this comparison, one or more loads which is/are tolerant of a voltage drop are then temporarily rejected or activated with a reduced or, if applicable, full power input. So-called PWM timers which render possible any clocking of the current fed to the load that is tolerant of a voltage drop can preferably be used for this.

For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 in a diagrammatic representation shows the arrangement of a power-multiplex system in a motor vehicle; Figure 2 shows a non-central control unit, which is coupled with a combined power and data bus, with loads connected downstream thereof; and Figure 3 shows a flow chart for the sequence of decisions relating to the activation of loads which are tolerant of a voltage drop.

According to Figure 1, a passenger car 1 has a power-multiplex system associated with it that consists of a central control unit 2, the data and power bus 3 and the non-central control units 21 to 27 which are coupled with the data power bus.

According to Figure 2, a plurality of loads which are the number-plate light 11, the rear light 12, the brake light 13, the reversing light 14, the indicator 15, a third brake light 16 and the rear window pane heating system 17 are connected downstream of the noncentral control unit, a socalled power-multiplex module 26 which is connected to the two-core data line 31 and the two-core power supply line 32.

The loads 11 to 16 are so-called voltage-sensitive loads. with regard to these loads, the electrical cross section of the power supply line 32 is dimensioned in such a way that the maximum voltage drop permissible on the power supply line 32 is not exceeded when all the lights are operated simultaneously. The rear window pane heating system 17 is a load that is tolerant of a voltage drop and which therefore, given a maximum voltage drop on the power supply line 32, can be activated at a different current intensity.

Associated either with the non-central control unit 26 or tne central control unit 2 there is a programmed controller module 33 which in accordance with Figure 3 in a memory S records the requirpments or demands on the data and line bus 3 that are made of the loads 11 to 17 (on, off) and calculates the sum of the power required and then in a comparator V checks the power required in total with regard to the permissible voltage drops and permissible current intensity on the power bus 32. If the test result is positive, the load or loads which is/are tolerant of a voltage drop is/are activated by way of a switch E. If the result is negative, the power which is requested is reduced to -6 the total tolerable value by way of a dimmer D formed as a PWM timer by activating in a clocked manner or by completely switching off one or more loads which are tolerant of a voltage drop.

is

Claims

1. Circuit arrangement for a sub-region of a motor vehicle on-board system, comprising at least one non-central control unit for coupling loads, including loads which are sensitive to a voltage drop and loads which are tolerant of a voltage drop, which are connected downstream thereof with a common power supply line of a power multiplex system, the electrical cross section of the common power supply line being adapted to the maximum voltage drop permissible for the common operation of the loads which are sensitive to a voltage drop, wherein a device is provided with which the current flow on the common power supply line can be adapted to the maximum voltage drop permissible by monitoring the voltage drop on this line and by activating the loads which are tolerant of a voltage drop in a variable manner.

The circuit arrangement as claimed in claim 1, wherein the device carries out the steps of: monitoring the operation of the loads; calculating the sum of the power requested by the loads; comparing the total power requested with the permissible voltage drop and permissible current density on the power bus; and reducing the total power requested by operating in a clocked manner or completely switching off oile or more loads which are tolerent of voltage drop, if the requested power exceeds the available power.

3. Circuit arrangement according to claim 1, wherein a PWM timer is provided for the variable activation of the loads which are tolerant of a voltage drop.

4. Circuit arrangement according to claim 1, 2 or 3, wherein the lights in the rear region of a passenger car constitute the loads which are sensitive to a voltage drop and the rear window pane heating system constitutes the load which is tolerant of a voltage drop.

5. A circuit arrangement substantially as herein described, with reference to the accompanying drawings.

6. A motor vehicle incorporating a circuit arrangement as claimed in any preceding claim.