DE102014219238A1 - Overcurrent detection in the current sensor with Hall sensor - Google Patents

Abstract

The invention relates to a method for measuring an electric current (20) in a vehicle, comprising detecting a voltage drop (42) on a conductor (28) through which the current to be measured (20), detecting an electric current to be measured (20 ) generating a measured value (26) for the current to be measured (20) based on the detected voltage drop (42) and the detected magnetic field (64).

Description

The invention relates to a method for detecting a current, a control device for carrying out the method and a current sensor with the control device.

From the DE 10 2011 078 548 A1 is a current sensor with a measuring shunt known through which a current to be measured is performed. A voltage drop is detected at the measuring shunt, wherein a signal processing device determines the current to be measured from the voltage drop as well as the material properties and geometric dimensions of the measuring shunt.

The current sensor is used in a vehicle, for example for monitoring the charge level of the vehicle battery. For reasons of safety, the current sensor should be equipped with self-monitoring in the context of which faults, such as an overcurrent, can be detected. In a conventional current sensor equipped with self-monitoring, the voltage drop in a second signal path independent of the signal processing means is compared with a predetermined voltage level and, if the voltage drop exceeds the predetermined voltage level, decided on the fault to be detected.

It is an object of the present invention to improve the known current measurement.

The object is solved by the features of the independent claims. Preferred developments are the subject of the dependent claims.

According to one aspect of the invention, a method of measuring a current includes steps of detecting a voltage drop across a conductor through which the current to be measured, detecting a magnetic field generated from the current to be measured around the conductor, and outputting a measurement value for the current to be measured based on the current detected voltage drop and the detected magnetic field.

The specified method is based on the consideration that the above-mentioned, independent of the signal processing device signal path to provide self-monitoring requires a high technical complexity of redundancy, which is reflected in particular in a large number of electronic components by redundant comparators. These redundant electronic components not only require a lot of space but are also relatively expensive.

Here, the specified method attacks with the suggestion that the signal path independent of the signal processing means does not already lead via the detection of the voltage drop but via the detection of a magnetic field caused by the current to be measured. In this way, cost-effective magnetic field sensor elements, such as Hall sensor elements can be used for self-monitoring of the current sensor, which can be realized much cheaper and more space-saving.

Magnetic field sensor elements can already be configured by the manufacturer so that they output the measured values digitally. This has the advantage that the predetermined voltage level necessary for the self-monitoring of an overcurrent can likewise be digitally predefined and compared directly with the output from the magnetic field sensor element. In contrast to the above-mentioned self-monitoring, in the context of which the predetermined voltage level usually via a pulse width modulation or similar. must be generated, the complexity of a current sensor using the specified method can be significantly reduced in the specified method. This is also noticeable in the response times, which could be reduced from the current approx. 20 ms with changes in the current to be measured to less than 10 μs.

In addition, the measured value for the current to be measured can be determined completely independently of the voltage drop at the measuring shunt from the detected magnetic field. This principle can be applied even if all electrical components are interconnected on a common circuit board. This significantly increases the reliability and reliability of a current sensor applying the specified method. The reliability is also particularly high because no sensor element with high-voltage-carrying parts needs to be brought into contact with the detection of the voltage drop at the measuring shunt during the detection of the magnetic field. Depending on the used magnetic field sensor element for detecting the magnetic field of the measured value for the current to be measured can be arbitrarily analog or digital, each output stepwise or continuously.

In addition, the magnetic field sensor elements used are usually already calibrated by the manufacturer and can be installed directly in a current sensor performing the specified method. A calibration by the manufacturer of the current sensor is no longer necessary, which manifests itself in reduced cycle times in the production of the current sensor.

Further, magnetic field sensor elements also have a higher temperature stability, whereby the self-monitoring of the current sensor can be realized particularly reliable.

When outputting the measured value for the current to be measured, other quantities can also be recorded and taken into account. For example, in the context of an electrical conductor in the form of an active measuring shunt, the voltage drop across the active measuring shunt and its control can be detected, which is necessary to keep the voltage drop across the measuring shunt constant. This control, for example in the form of a drive signal can then also be taken into account in the output of the measured value.

In a development of the specified method, the measured value for the current is determined based on the detected voltage drop, and the thus determined measured value is output based on a comparison with the detected magnetic field. The comparison in the specified method can, for example, serve as a verification as to whether the current to be measured is detected correctly by the measuring shunt. The verification can be arbitrary and is not limited to a particular method.

In an additional development of the specified method, the comparison with the detected magnetic field includes a plausibility check of the measured value based on the detected magnetic field. A plausibility check should be understood to mean a method in which the measured value for the current to be measured is checked by way of a rough estimate as to whether the measured value can be acceptable, reasonable and / or comprehensible or not. As a basis for this plausibility check, therefore, the detected magnetic field need not be detected with very low tolerances, but it must only provide a sufficient basis for ever being able to determine whether or not the measured value determined based on the voltage drop can be correct. In this way, low-cost electronic components can be used to detect the magnetic field, which reduce the cost of a current sensor executing the specified method.

In a particular development of the specified method, the plausibility check fails if a current value resulting from the detected magnetic field exceeds a predetermined value. As part of this plausibility check, a measurement is detected with the current sensor performing the specified method in a measuring range for which the current sensor is not designed, and the correctness of the current values determined based on the voltage drop can no longer be assumed to be ensured.

In such a case, for example, an error may be output that may then indicate, for example, an overcurrent. The particular advantage of the specified method is that the error detection and forwarding to a higher-level signal processing device can take place via a signal path that is completely different from the measured value acquisition.

According to a further aspect of the invention, a control device is set up to carry out a method according to one of the preceding claims.

In a development of the specified control device, the specified device has a memory and a processor. The specified method is stored in the form of a computer program in the memory and the processor is provided for carrying out the method when the computer program is loaded from the memory into the processor.

According to a further aspect of the invention, a computer program comprises program code means for performing all the steps of one of the specified methods when the computer program is executed on a computer or one of the specified devices.

In accordance with another aspect of the invention, a computer program product includes program code stored on a computer-readable medium and, when executed on a data processing device, performs one of the specified methods.

According to a further aspect of the invention, a current sensor for detecting a current comprises an electrical conductor through which the current to be detected can flow, a first sensor element for detecting a voltage drop across the electrical conductor, a second sensor element for detecting a magnetic field that can be built up around the electrical conductor, and one of the stated control devices for determining the current based on the voltage drop and the magnetic field.

The second sensor element for detecting the magnetic field can in principle be of any desired design. For cost reasons, the second sensor element should be a Hall sensor in a development of the specified sensor.

In another embodiment of the specified sensor, a distance between the first sensor element and the second Sensor element falls below a predetermined distance. The predetermined distance should be chosen such that both sensor elements are positioned as close as possible to each other, so that both sensor elements actually measure the same current and not, for example, structural differences in the measurement shunt lead to different measurement results.

In a particular embodiment of the specified sensor, a measurement tolerance of the second sensor element may be greater than a measurement tolerance of the first sensor element. In this way, inexpensive electronic components can be used for the second sensor element relative to the first sensor element, whereby the manufacturing cost of the specified sensor can be reduced.

According to another aspect of the invention, a vehicle includes one of the specified sensors.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which will be described in connection with the drawings, wherein:

1 a schematic diagram of a vehicle with an electric drive;

2 a schematic diagram of a current sensor for the vehicle of 1 ;

3 a schematic diagram of an alternative current sensor for the vehicle of 1 ;

4 a schematic view of a control circuit for controlling the current sensor 3 .

5 a schematic view of the extended by a Hall element current sensor of 2 , and

6 a schematic view of a Plausibilisierungseichrichtung to plausibility one with the current sensor of 5 show measured value.

In the figures, the same technical elements are provided with the same reference numerals and described only once.

It will open 1 Reference is made to a schematic diagram of a vehicle 2 with an electric drive 4 shows.

In the context of the embodiment, the vehicle 2 exemplarily have a front wheel drive, in which the electric drive 4 includes an electric motor 6 Includes, via a drive shaft 8th the front wheels 10 of the vehicle 2 drives. The rear wheels 12 of the vehicle 2 are therefore freewheeling wheels.

The electric motor 6 of the electric drive 4 is in the present embodiment via an electrical converter 14 in a known manner from a vehicle battery 16 with electrical energy 18 provided. This is the vehicle battery 16 an electric current 20 then, via the converter 14 controlled by a motor control 22 trained control device in the for driving the electric motor 6 suitable electrical energy 18 is converted. The engine control system controls this 22 the converter 14 with known control signals.

For the fulfillment of various tasks, such as the charge management of the vehicle battery 16 must the engine control 22 via a current sensor 24 from the vehicle battery 16 discharged electric power 20 to capture.

In the present embodiment, the current sensor 24 a reading 26 out, that of the vehicle battery 16 discharged electric power 20 describes and thus in a predetermined manner depends on this. This is the purpose of the following 2 be explained in more detail, in which the current sensor 24 is shown in a schematic diagram.

The current sensor 24 has a measuring shunt in the present embodiment 28 on, which is formed of a first electrically conductive material. The measuring shunt 28 can have two connection elements 30 from a second electrically conductive material in the electric drive 4 of the 1 be electrically integrated. The first electrically conductive material of the measuring shunt 28 may include, for example, manganin and with the two connecting elements 30 for example, be welded. The second electrically conductive material of the two connection elements 30 may include, for example, copper. The two connection elements 30 thus form a contact resistance between the remaining circuit elements of the electric drive 4 and the measuring shunt 28 ,

For measuring the electric current 20 points the current sensor 24 a first electrical connection 32 and a second electrical connection 34 on, over in the direction of the electric current 20 seen correspond to a first electrical potential 36 in front of the measuring shunt 28 and a second electrical potential 38 after this Shunt 28 can be detected. The two detected electrical potentials 36 . 38 In the present embodiment, a first sensor element in the form of a differential amplifier 40 fed. The differential amplifier 40 subtracts the two electrical potentials 36 . 38 from each other, thus forming a voltage drop 42 that with it over the measurement shunt 28 drops and gives that of this voltage drop 42 dependent measured value 26 in the form of an output signal. Based on the voltage drop 42 dependent measured value 26 can use it for example in the engine control 22 the electric current 20 in a manner known per se based on the electrical and geometric properties of the measuring shunt 28 be determined.

The measuring shunt 28 is in the current sensor 24 of the 2 designed as a passive measuring shunt. Alternatively, the measuring shunt 28 also be formed as an active measuring shunt, what in the context of 3 and 4 will be discussed in more detail.

The measuring shunt points as active measuring shunt 28 a first controllable switch 44 and a second controllable switch 46 in each case in the present embodiment, a not further referenced field effect transistor and an unspecified referenced freewheeling diode, which is connected in the forward direction from source to drain. Both controllable switches 44 . 46 are interconnected in anti-parallel.

In 3 is instead of the differential amplifier 40 as the first sensor element an evaluation circuit 48 shown. The evaluation circuit 20 controls the field effect transistors of the controllable switches 44 . 46 such that the voltage drop 42 over the measuring shunt 28 on a in 4 indicated setpoint 54 is held.

The evaluation circuit detects this 20 the voltage drop 42 over the measuring shunt 28 and controls the gates of the field effect transistors of the controllable switches 44 . 46 each with a control signal 50 so on, that voltage drop 42 above the in 4 shown control loop 52 on the setpoint 54 is held. Here are the control signals 50 , like in the DE 10 2011 078 548 A1 shown, depending on the electric current to be measured 20 , Therefore, if this dependence in the evaluation circuit 48 is deposited, the measured value 26 for the electric current 20 directly from the control signals 50 be derived when the voltage drop 42 to the setpoint 54 is regulated.

The control loop 52 includes in the present embodiment as a controlled system the measuring shunt 28 at which the voltage drop 42 is tapped. The voltage drop 42 is for example at a difference element 56 by subtraction the setpoint 54 faced with a control difference 58 results, the one in the evaluation circuit 48 arranged regulator 60 is output, which may be formed in a manner known to those skilled in the art. The regulator 60 then generates the control signals again 50 to the voltage drop 42 on the setpoint 54 to keep.

Further details about an active measuring shunt can be found in the already mentioned DE 10 2011 078 548 A1 be removed.

In the present embodiment, the electric current 20 be measured redundantly, which is exemplified below with reference to 5 is to be explained, in a perspective view of the measuring shunt 28 as a passive shunt for example the 2 shows. There are some elements of the 2 for the sake of brevity 5 not shown and must be replaced mentally. However, the following statements can also be applied 1: 1 to the active measuring shunt, for example the 3 and are therefore not limiting.

For redundant measurement of the electric current 20 is next to the first sensor element in the form of the differential amplifier 40 or the evaluation circuit 48 a second sensor element in the form of a Hall sensor 62 available, one of the electric current 20 generated magnetic field 64 should capture. Instead of the Hall element 62 It is also possible to use other magnetically sensitive sensors, such as an AMR element.

The Hall element 62 gives in the present embodiments one of the electric current 20 dependent redundant measured value 66 off, for example, together with the measured value 26 to an in 6 Plausibilisierungseinrichtung shown 68 can be issued.

The plausibility checker 68 could be in the current sensor 24 but also in the engine control 22 be integrated.

In the context of the present embodiment, the redundant measured value 66 for the electrical current of a test facility 70 supplied to the redundant measured value 66 with an error value 72 compares. This error value 72 For example, an upper limit for the electric current 20 be, from which an overcurrent through the current sensor 24 to be recognized. In this case, would in the test facility 70 determined if the redundant reading 66 the error value 72 in the form of the upper limit. If this is true, then the test device can 70 a control signal 74 be issued, with which a switch 76 in such a way that instead of the measured value 26 an error signal 78 , for example, from a memory 80 is issued.

The error signal 78 replaces the measured value 26 in the case of an error. Alternatively, but the measured value 26 and the error signal 78 be output together, so that the actual measured value of a combination of based on the voltage drop 42 determined measured value 26 and the error signal 78 results.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011078548 A1 [0002, 0045, 0047]

Claims (10)

Method for measuring an electric current ( 20 ) in a vehicle, comprising - detecting a voltage drop ( 42 ) at a current to be measured ( 20 ) conductors ( 28 ), - detecting an electric current to be measured ( 20 ) around the ladder ( 28 ) constructed magnetic field ( 64 ), - output a measured value ( 26 ) for the current to be measured ( 20 ) based on the detected voltage drop ( 42 ) and the detected magnetic field ( 64 ). Method according to claim 1, wherein the measured value ( 26 ) for the electric current ( 20 ) based on the detected voltage drop ( 42 ) and the measured value determined in this way ( 26 ) based on a comparison with the detected magnetic field ( 64 ) is output. Method according to claim 2, wherein the comparison with the detected magnetic field ( 64 ) a plausibility check ( 68 ) of the measured value ( 26 ) based on the detected magnetic field ( 64 ). Method according to claim 3, wherein the plausibility check ( 68 ) fails, if one of the detected magnetic field ( 64 ) resulting current value ( 66 ) a predetermined value ( 72 ) exceeds. Method according to claim 3 or 4, comprising: - issuing an error ( 78 ), in particular an overcurrent-indicating error, based on the failed plausibility check ( 68 ). Control device adapted to carry out a method according to one of the preceding claims. Current sensor ( 24 ) for detecting a current ( 20 ) comprising: - an electrical conductor ( 28 ), of the current to be detected ( 20 ) is flowed through, - a first sensor element ( 40 . 48 ) for detecting a voltage drop ( 42 ) on the electrical conductor ( 28 ), - a second sensor element ( 62 ) for detecting one around the electrical conductor ( 28 ) buildable magnetic field ( 64 ), and - a control device according to claim 6 for determining the current ( 20 ) based on the voltage drop ( 42 ) and the magnetic field ( 64 ). Current sensor ( 24 ) according to claim 7, wherein the second sensor element ( 62 ) is a Hall sensor. Current sensor ( 24 ) according to claim 7 or 8, wherein a distance between the first sensor element ( 40 . 48 ) and the second sensor element ( 62 ) falls below a predetermined distance. Current sensor ( 24 ) according to one of the preceding claims 7 to 9, wherein a measurement tolerance of the second sensor element ( 62 ) is greater than a measuring tolerance of the first sensor element ( 40 . 48 ).

Images