EP1787372A1

EP1787372A1 - Circuit arrangement for the protection of a conductor element against overload

Info

Publication number: EP1787372A1
Application number: EP05759924A
Authority: EP
Inventors: Rolf Wagemann
Original assignee: Intedis GmbH and Co KG
Current assignee: Intedis GmbH and Co KG
Priority date: 2004-08-13
Filing date: 2005-06-15
Publication date: 2007-05-23
Also published as: CN101036274A; JP2008512071A; WO2006015566A1; DE102004039601B3

Abstract

The invention relates to a circuit arrangement (01, 15, 21), for the protection of a conductor element (02), in particular, a planar conductor, in a motor vehicle against overload, comprising a first measuring body (06), by means of which the temperature, or a measured value correlated to the temperature, may be directly or indirectly measured on or in a measuring section (11) of the conductor element (02) and an actuator (03), by means of which the power supply to the conductor element may be reduced, in particular, switched off. The temperature or a measured value correlated to the temperature on or in a reference section (07) of the conductor element (02) may be directly or indirectly measured, by means of a second measuring body (05), whereby the reference section (07) of the conductor element (02) has the same current flow as the measuring section (11) and the measured results from the first measuring body (06) and the second measuring body (05) can be directly or indirectly compared in a comparator element (04) and the actuator (03) controlled depending on the result of said comparison.

Description

Circuit arrangement for protecting a conductor element against overcurrent

The invention relates to a circuit arrangement for protecting a

Conductor element against overcurrent according to the preamble of claim 1.

Generic circuit arrangements are used in motor vehicle construction in order to protect the lines of the vehicle electrical system against an inadmissibly high current load, by means of which the lines are excessively heated. Such overcurrents can occur, for example, when there is a short circuit in the electrical system.

To protect the on-board network against overcurrents, fuses are known from the prior art, which fuses are switched into the corresponding line to be protected, a fusible link melting in the fuse at an excessive current load due to the heating occurring thereby and the fuses in this way Power supply interrupts. A disadvantage of these fuses is that they react very slowly, so that in particular the protection of sensitive electronic components is not reliably guaranteed. Furthermore, electronic monitoring sensors are known from the prior art with which the temperature can be measured at one point of the line to be protected, wherein when exceeding a certain temperature or when exceeding another, correlated with the temperature of the conductor element Messwer¬ tes Power supply is switched off or reduced by a suitable actuator.

A disadvantage of these known circuit arrangements is that the ambient temperature in or on the vehicle is included in the measurement result as a disturbance variable, and thus in each case different switch-off results are achieved at different ambient temperatures. Accordingly, the vehicles equipped in this way would have to be tuned differently depending on the particular field of use and the average ambient temperature to be expected there, which represents a considerable additional expense.

Based on this prior art, it is therefore an object of the present invention to propose a new circuit arrangement for the protection of conductor elements in the motor vehicle.

This object is achieved by a circuit arrangement according to the teaching of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the basic idea that the temperature or a temperature-correlated measured value not only in a measuring section, but also in a suitable

Reference section is measured. These two measurement results from the measurement section and the reference section are forwarded directly to a comparator element after a suitable intermediate processing step and compared there with each other. The actuator for reducing or switching off the power supply is then controlled depending on the comparison result. Since the influences of the ambient temperature both in the measured value from the measuring section and in the measured value from the reference section, this influence can be eliminated when comparing the two measured values in the comparator element. The control of the actuator for Verrin¬ delay or shutdown of the power supply thus takes place only on the basis of the relative comparison of the measured values in the measuring section and reference section.

The design of the conductor element in the measuring section or in the reference section is basically arbitrary. According to a preferred embodiment, however, the reference section should have a different cross section, in particular a different width, than the measuring section. It is thereby achieved that the increase in the current flow in the conductor element causes in each case different temperature changes in the measuring section or reference section. These different temperature change coefficients can be advantageously utilized in the evaluation of the measurement results in the comparator element.

According to a preferred embodiment s form, the conductor element in

Reference section on a much larger cross-section than in Messab¬ section on. In particular, the reference section should be at least twice as wide as the measuring section. In this way, the conductor element in the reference section only experiences a relatively slight increase in temperature when the current flow increases, whereas the temperature curve in the measuring section of the conductor element increases much more steeply. Exact intersections between the measuring curves can be defined by means of these greatly differing gradient coefficients of the measuring curves, with a switching operation of the actuating element then being able to take place at the intersection of the measuring curves. The direct temperature measurement in the measuring section or reference section is relatively complicated and heavily faulty. According to a first embodiment of the invention, it is therefore proposed, instead of the temperature in the measuring section or reference section in each case, to measure the voltage dropping between two measuring points in the measuring section or between two measuring points in the reference section as measured values. It is known that the electrical resistance of a conductor element depends on the temperature of the conductor element. The voltage dropping between two measuring points on a conductor element thus correlates with the temperature of the conductor element. If the temperature rises in the conductor element, the electrical resistance increases, as a result of which a higher voltage drops between the two measuring points.

By suitable choice of the geometry of the conductor element in the measuring section and in the reference section, the circuit arrangement can

Measurement of the voltage drop between two measuring points in Messab¬ section or in the reference section to be calibrated to a desired measuring range. If the ratio of the distance between the measuring points in the reference section to the distance between the measuring points in the measuring section is selected such that it corresponds to the ratio of the cross section of the conductor element in the reference section to the cross section of the conductor element in the measuring section, it is achieved that, despite the different Cross-sections of the Leiterele¬ ment in the measuring section and in the reference section between the respective measuring points in the measuring section or in Referenzab¬ cut at normal temperature of the conductor element which drops approximately equal voltage.

By further processing the measuring signals by means of an amplifier, the measuring signals can also be calibrated to a desired level of the signal strength. It is particularly advantageous if the two initially approximately equal measurement signals by choice different amplification factors are brought to different Signalni¬ veaus, so that when the conductor element heats up, an intersection between the signal curves can result. Such an intersection can be evaluated with relatively simple means and then used to control the actuator to influence the power supply. As amplifiers in this sense, it is also possible to use components with a negative amplification factor, for example electrical resistors.

As an alternative to calibrating the measurement signals to different signal levels by using amplifiers, this can also be achieved by selecting a corresponding ratio of the distance between the measurement points in the reference section to the distance between the measurement points in the measurement section. If the ratio of the distance between the measuring points in the reference section to the distance between the measuring points in the measuring section differs from the ratio of the cross section of the conductor element in the reference section to the cross section of the conductor element in the measuring section, this results in a corresponding difference in the signal levels.

As an alternative to measuring the voltage dropping in the measuring section or reference section, it is also possible to use a circuit arrangement designed in the manner of a bridge circuit for comparing voltage potentials.

To form the bridge circuit, a series circuit of a first resistor and a second resistor can be connected in parallel with the series connection of reference section and measuring section. Between a first contact point, which is located between the reference section and the measuring section, and a second contact point, which is located between the first resistor and the second resistor, a connecting line is connected, which serves as a measuring bridge. The comparator element is switched into the connecting line, so that in the ratorelement the voltage potential at the first contact point with the voltage potential at the second contact point relative to a Referenz¬ potential, for example, the vehicle mass, can be compared. By suitable dimensioning of the two resistors, which are connected in parallel to the reference section and measuring section, it is possible to detune this measuring bridge in such a way that the voltage potentials at the two contact points slowly approach each other as the temperature in the conductor element increases. As soon as the voltage potentials at both contact points are the same, this can be evaluated as a switching point at which the actuator reduces or shuts off the power supply to the conductor element.

The two resistors in the measuring bridge can be formed by suitable components, for example SMD resistors. According to a preferred embodiment, however, it is provided that the first resistor is formed by a third portion of the conductor element whose cross section corresponds to the measuring section and the second resistor is formed by a fourth portion of the conductor element whose cross section corresponds to the reference section. As a result of this double evaluation of the temperature influence on the conductor element in the reference section or measuring section, an improved resolution of the measuring signals can be achieved.

The circuit arrangement according to the invention offers a particular advantage in that the relevant elements can be formed by a flat conductor track itself. If necessary, electrical or electronic components can additionally be contacted on the flat conductor track in order to construct the circuit arrangement.

The circuit arrangement according to the invention is explained by way of example with reference to schematically illustrated embodiments. Show it:

1 shows a first embodiment of a circuit arrangement in a schematic view from above.

FIG. 2 shows the measurement signal course of the circuit arrangement according to FIG. 1 at low currents; FIG.

Fig. 3 shows the measurement signal waveform of the circuit according to

Fig. 1 at medium currents;

4 shows the measurement signal course of the circuit arrangement according to FIG

Fig. 1 at high currents;

5 shows a second embodiment of a circuit arrangement in a schematic view from above;

6 shows a third embodiment of a circuit arrangement in a schematic view from above;

In Fig. 1, a first embodiment 01 of a circuit arrangement for protecting a flat conductor 02 is shown from overcurrents. Of the

Flat conductor 02 is formed by a copper layer laminated onto a carrier foil and is shown only in the hatched area corresponding to its actual geometric shape. The other lines in the circuit 01 are only schematically indicated by connecting lines, but can also be formed by Flachlei¬ terelementen.

The flat conductor 02 is preceded by an actuator 03, which is controlled by a comparator 04. About the flat conductor 02, a downstream load 24 is supplied with electrical energy. Depending on the output signal of the comparator element 04, the power supply to the flat conductor 02 can be switched off by opening the actuator 03. In the circuit arrangement 01, a measuring element 05a and a measuring element 06a are furthermore provided. With the measuring element 05a, the voltage dropping in a reference section 07 between two measuring points 08 and 09 can be measured as the measured variable correlating with the temperature in the reference section 07. With the measuring element 06a, the voltage 14 between two measuring points 12 and 13 can be measured in a measuring section 11, which has a cross section corresponding to the usual configuration of the flat conductor 02.

The reference section 07 has twice the width of the measuring section 11 and heats up correspondingly weaker than the measuring section 11 due to this higher line cross section. To compensate for the lower resistance due to the larger cross section in the reference section 07, the distance between the measuring points 08 and 09 at the reference section 07 is double as large as the distance between the measuring points 12 and 13 in the measuring section 11. In the normal temperature range with only very moderate heating of the flat conductor 02, therefore, approximately equal voltages 10 and 14 fall in the reference section 07 and in the measuring section 11. The voltage drop 10 measured by the measuring element 05a is forwarded without amplification to the first input of the comparator element 04. The voltage drop 14 in the measuring section 11 is amplified in the measuring element 06 by means of a suitable amplifier with a gain factor of 0.8 and then forwarded to the second input of the comparator 04. The function of the circuit arrangement 01 for evaluating the measured values by the comparator element 04 and the control of the actuator 03 dependent thereon will be explained below with reference to the measurement signal profiles in FIGS. 2, 3 and 4.

FIG. 2 schematically shows the measurement signal profile at the two inputs of the comparator element 04 when the flat conductor 02 is loaded with small currents. With these small currents, the flat conductor 02 heats up neither in the reference section 07 nor in the measuring section 11, so that the voltage drop in the reference section 07 and in the measuring section 11, that is to say the falling voltages 10 and 14, remain the same during the load duration. Due to the different reinforcements in the measuring elements 05 and 06, the voltage drop 14 is reduced to an 80% level of the voltage drop 10.

In Fig. 3, the waveform at medium current in the flat conductor 02 is shown. The flat conductor 02 already heats up considerably in the thinner measuring section 11 at this current intensity, whereas the flat conductor 02 in the reference section 07 still does not undergo a substantial increase in temperature due to the greater width. For the decreasing voltages 14 and 10, this means that the voltage drop 10 in the reference section 07 does not change due to the lack of temperature increase, whereas the voltage drop in the measuring section 11 increases significantly with increasing load duration due to the temperature increase. At time U, the magnitude of the voltage drop 14 amplified by the factor 0.8 coincides with the magnitude of the voltage drop 10 in the reference section 07. This conformity of the measuring signals present at the inputs of the comparator element 04 is evaluated by the comparator element 04 as a switching point, and the actuator 03 is actuated upon reaching this switching point for switching off the power supply.

FIG. 4 shows the measurement signal course 10 and 14 for large currents. For large currents, the flat conductor 02 heats up both in the measuring section 11 and in the reference section 07, wherein the heating in the reference section 07 is slower and with a smaller gradient than the heating in the measuring section 11 due to the larger cross section. This means for the two measuring signal curves in that the curve of the voltage drop 10 increases with a slope factor smaller than the voltage drop measurement curve 14. Thus, there continues to be an intersection for the two curves at time t ₂ , the is again evaluated as a switching point for switching off the actuator 03.

In Fig. 5, a second embodiment 15 of a circuit arrangement is shown schematically, which in turn can be used to protect the flat conductor 02 against overcurrents. In this embodiment, the two measuring elements 05b and 06b are formed by a bridge circuit, which will be explained below.

On the flat conductor 02, in turn, a reference section 07 is provided with double the width and a measuring section 1 1 with a normal width. Parallel to the series circuit of reference section 07 and measuring section 1 1, a series circuit of a first resistor 16 and a second resistor 17 is connected. Two sections 18a and 18b of a connecting line 18 connect the two inputs of the comparator element 04 to a first contact point 19 between the reference section 07 and the measuring section 11 and a second contact point 20 between the first resistor 16 and the second resistor 17 Connecting line 18 thus forms a measuring bridge with which the voltage potential at the first contact point 19 can be compared with the voltage potential 20 and evaluated. As a result, the two measuring elements 05b and 06b are formed by this bridge circuit for potential comparison.

By suitable dimensioning of the two resistors 16 and 17, this measuring bridge can be detuned in such a way that the voltage potentials at the two contact points 19 and 20 coincide in terms of magnitude when reaching a certain temperature in the flat conductor 02. This match is detected in the comparator 04 and then the actuator 03 is switched.

FIG. 6 shows a third embodiment 21 of a circuit arrangement according to the invention. Also in the embodiment 21, the two measuring members 05c and 06c are of a bridge circuit formed for potential comparison. The function of this circuit arrangement 21 thus corresponds essentially to the circuit arrangement 15, but the two resistors 16 and 17 are formed by two further sections 22 and 23. The design of the third section 22 corresponds to the shape of the measuring section 11, and the shape of the fourth section 23 corresponds to the shape of the reference section 07.

Claims

claims

1. Circuit arrangement (01, 15, 21) for protecting a conductor element (02), in particular a flat conductor, in a motor vehicle against overcurrent with a first measuring element (06), with the temperature or a correlated with the temperature reading on or in egg A measuring section (11) of the conductor element (02) can be measured indirectly or indirectly, and with an actuator (03) with which the current supply to the conductor element (02) can be reduced, in particular switched off, thereby calibrating et that with a second measuring element (05) the temperature or a correlated with the temperature reading on or in a Referenz¬ section (07) of the conductor element (02) is directly or indirectly measurable, wherein the reference portion (07) of the conductor element

(02) flows through the same flow as the measuring section (11), and wherein the measurement results of the first measuring element (06) and the second measuring element (05) can be compared directly or indirectly in a comparator element (04), and wherein the actuator ( 03) is controllable in dependence on the comparison result.

2. Circuit arrangement according to claim 1, characterized ekennz ei chnet, that the conductor element (02) in the measuring section (11) has a different cross-section, in particular a different width, as in Referenzab¬ section (07).

3. A circuit arrangement according to claim 2, characterized gekennzei chn et, that the conductor element (02) in the reference section (07) has a wesent¬ Lich larger cross section than in the measuring section (11), in particular in the reference section (11) is at least twice as wide ,

4. Circuit arrangement according to one of claims 1 to 3, characterized ekennz ei chnet, that the first measuring element (05) is designed in the manner of a voltage measuring element, with which between two measuring points (12, 13) in the measuring section (11) of the conductor element (02) decreasing voltage (14) is measurable, and the second measuring element (06) is designed in the manner of a voltage measuring element with which the between two Mess¬ points (08, 09) in the reference section (07) of the conductor element (02 ) falling voltage (10) is measurable.

5. Circuit arrangement according to claim 4, characterized in that the ratio of the distance between the measuring points (08, 09) in the reference section (07) to the distance between the Meßpunk¬ th (12, 13) in the measuring section (11) the ratio of the cross section of Conductor element (02) in the reference section (07) corresponds to the cross section of the conductor element (02) in the measuring section (11).

6. Circuit arrangement according to claim 4 or 5, characterized gekennz egg chnet, that the measurement signal of the first voltage measuring element (06) before the comparison operation in the comparator (04) is amplified with a vorgege¬ surrounded first gain factor and / or the Mess¬ signal of the second voltage measuring element (05) is amplified before comparison operation in the comparator element (04) with a predetermined second amplification factor.

7. Circuit arrangement according to claim 6, characterized gekennz ei CHnet, that the first amplification factor and the second amplification factor are different.

8. Circuit arrangement according to claim 4, characterized ek ennz ei chnet, that the ratio of the distance between the measuring points (08, 09) in the reference section (07) to the distance between the Meßpunk¬ th (12, 13) in the measuring section (11) itself from the ratio of the cross section of the conductor element (02) in the reference section (07) to

Cross section of the conductor element (02) in the measuring section (11) underside separates.

9. Circuit arrangement according to one of claims 4 to 8, characterized g ek ennzei chn et that the comparator (04) controls the actuator, in particular the power supply turns off when the two Differenzspannun¬ conditions are equal.

10. Circuit arrangement according to claim 1, characterized in that the first measuring element (05) and the second measuring element (06) are formed by a bridge circuit.

11. Circuit arrangement according to claim 10, characterized in that a series connection of a first resistor (16, 22) and a second resistor (parallel to the series connection of reference section (07) of the conductor element (02) and measuring section (11) of the conductor element (02) 17, 23) is connected, wherein between a first contact point (19) which is arranged between reference portion (07) and measuring section (11), and a second contact point (20) between the first resistor (16, 22) and second Wider - Stand (17, 23) is arranged, a connecting line (18) as

Measuring bridge is provided, and wherein the comparator element (04) in the connecting line (18) is connected, and wherein Kompa¬ ratorelement (04) the voltage potential at the first contact point (19) with the voltage potential at the second contact point (20) are compared can.

12. Circuit arrangement according to claim 11, characterized in that the reference section (07) passes directly into the measuring section (11) and the first contact point (19) is arranged at the transition between reference section (07) and measuring section (11).

13. Circuit arrangement according to claim 11 or 12, characterized in that the first resistor is formed by a third section (22) of the conductor element (02) whose cross-section corresponds to the measuring section (11) of the conductor element (02), and the second resistance is formed by a fourth section (23) of the conductor element (02) whose cross-section corresponds to the reference section (07) of the conductor element (02).

14. Circuit arrangement according to claim 13, characterized in that the length of the third section (22) corresponds to the length of the measuring section (11) and the length of the fourth section (23) corresponds to the length of the reference section (07) ,

15. Circuit arrangement according to claim 13, characterized in that the length of the third section (22) and the length of the measuring section (11) do not correspond in each case to the length of the fourth section (23) and the length of the reference section (FIG. 07).

16. Circuit arrangement according to one of claims 13 to 15, characterized g ekennzei chn et, that the third section (22) passes directly into the fourth section (23) and the second contact point (20) at the transition between see third section (22) and fourth section (23).

17. Circuit arrangement according to one of claims 1 to 16, characterized gek ennz ei chn et, that the first measuring element (06) and / or the second measuring element (05) and / or the comparator element (04) and / or the actuator (02) of flat conductor tracks (02) and on the flat conductor tracks (02) kon¬ taktierten electrical or electronic components are formed.

18. Circuit arrangement according to one of claims 1 to 17, characterized ekennz eichennz that the conductor element (02), in particular the flat conductor, on a

Support material, in particular a carrier film or a circuit board, is arranged.

19. Circuit arrangement according to one of claims 1 to 18, characterized in that the conductor element (02), in particular the flat conductor, zen by etching or punching a metal layer, in particular a copper layer is prepared.