EP1915631A1

EP1915631A1 - Method and device for monitoring a first voltage value

Info

Publication number: EP1915631A1
Application number: EP06778094A
Authority: EP
Inventors: Winfried Hasenberg
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2005-08-01
Filing date: 2006-08-01
Publication date: 2008-04-30
Also published as: JP2009504044A; DE102005036047A1; CN101233418A; US20090195257A1; WO2007014945A1

Abstract

The invention relates to a method for monitoring a first signal voltage value (Us) which is producible by an electronic component (100), positioned within the range of a signal voltage (Usens) and is detectable by a measuring device (150) whose input voltage range is less than the range of a signal voltage (Usens), wherein a voltage divider (110, 111, 112) converts the signal voltage range into an input voltage range, the first voltage value is measured by the measuring device (150), an electrical resistance exhibiting component (120) is mounted at least partially in parallel to the voltage divider (110, 111, 112), a second voltage value is subsequently measured by the measuring device (150) and the inspection result is derived from the comparison of the first and second voltage value. The invention also relates to a device (110, 111, 112, 120, 121) comprising the voltage divider, switching means (121) and the electrical resistance exhibiting component (120), which is mountable at least partially in parallel to the voltage divider (110, 111, 112) with the aid of the switching means (121).

Description

Method and device for checking a first voltage value

The present invention relates to a method and a device for checking a first voltage value according to the preamble of claims 1 and 11.

State of the art

In the following, reference will be made essentially to motor vehicle construction, without the method being restricted to this application.

In modern times, microcontroller (μC) are increasingly used within electrical or electronic components or general circuits (eg motor control devices), which have an analog-to-digital converter (ADC), typically a multi-channel ADC with a reference voltage of 5 V. These ADCs are intended to receive analog voltages from, for example, sensors in a motor vehicle (motor vehicle) and to convert them into digital signals, which are then further processed. Therefore, sensors are typically designed for a 5V supply voltage. The analog output or sensor signal then includes z. For example, if the voltage measured by the ADC is in the low range, for example below 0.25V, or in the upper range, for example greater than 4.75V, this indicates one Error (open circuit, short circuit, ground fault, etc.).

Meanwhile, increasingly integrated circuits, such. As the mentioned microcontroller, are used, which require a supply voltage of only 3.3V. For the automotive industry, for example, the microcontroller TriCore TC1766 from Infineon can be cited here. As a result, only a 3.3V reference voltage is available to the internal ADCs, i. a conversion can only be done reliably in the range from 0 V to 3.3 V.

It has been found that this change does not impose any functional restrictions with regard to the diagnostic function of the passive sensors (eg NTCs, accelerator pedal potentiometer, etc.) if the sensor supply voltage is also changed to 3.3 V. In addition, analog, active sensors (eg pressure sensors) are also used. The reference and supply voltage of these sensors is production-related. Active 3.3V sensors are only offered by a few manufacturers at high prices. It is therefore not desirable to use these sensors.

Solutions are known to active 5 V sensors on a

3.3 V ADC to operate. DE 100 50 962 A1 shows a method in which five reference signals are used to determine a first signal as accurately as possible. This Driving requires a complicated and expensive circuit design.

In DE 102 32 361 Al a method for determining a signal voltage is described, in which by a periodic measurement of the signal potential and then comparing the same and a supply potential in each case with a ground potential, the signal voltage is determined. The implementation of this method requires many individual process steps.

Basically there is z. For example, it is possible to adapt the output signal to the measuring range of the 3.3 V ADC via a precision voltage divider. The accuracy of the measurement value acquisition is sufficient in many cases. However, by using a precision voltage divider, full diagnostic functionality of an OBD-II standard sensor is eliminated. As a rule, active sensors for signaling an interruption of the sensor mass have an internal pull-up resistor whose functionality is explained below with reference to FIG. 1a.

In the case of an interrupted sensor ground, a sensor signal of substantially 5 V will be present at the output of the sensor, which represents an implausible voltage value. A μC with integrated 5 V ADC connected to the sensor can detect this error and evaluate it via software. If, however, the sensor is connected to a μC with integrated 3.3 V ADC via a voltage divider, a voltage at the ADC input will occur at the sensor ground via the internal pull-up resistor of the sensor and via the resistors of the voltage divider plausible signal range and therefore not from the - A -

Software can be evaluated. The error is not recognized and a diagnosis is not possible.

In the prior art, to circumvent this problem, an additional 5V ADC, e.g. As a CY100, which is connected via a digital interface, such as SPI bus, with the μC. Disadvantages of this solution are, in particular, the additional costs for the 5 V ADC module. Furthermore, not all channels of the multi-channel ADC modules are usually used, which also represents a waste of resources. In motor vehicle construction, the use of the CY100 in motor control units due to the SPI bus (approximately 1 ms grid) limits the read-out speed of the ADC values, so that this module can not be used for safety-critical functions (eg rail pressure). The block additionally loads the SPI resources.

The problem therefore arises of providing a method and a device for improving the operation of components having an output voltage on components having an input voltage different from the output voltage.

According to the invention a method with the features of claim 1 and an apparatus with the features of claim 11 are proposed. Advantageous embodiments will become apparent from the dependent claims and the description below.

Advantages of the invention In the method according to the invention for checking a first voltage value of a signal voltage which can be output by a electronic component and is detectable by a measuring device having an input voltage range which is smaller than the signal voltage range, wherein a voltage divider transforms the signal voltage range into the input voltage range, If an initially first voltage value is measured by the measuring device, a component having an electrical resistance is at least partially connected in parallel to the voltage divider and then a second voltage value is measured by the measuring device. The result of the test can be derived from the comparison of the first and the second voltage value.

Advantageously, a fault of the electronic component is detected when the first one differs from the second voltage value by at least one predetermined threshold value.

The invention can be realized in particular by a series connection of a component having a resistance (resistance component) and a switch (eg MOSFET) which is connected in parallel with a (precision) voltage divider. The switch or the semiconductor is preferably controlled by the measuring device (eg μC). In particular, if the read-in first voltage value lies within a voltage range where it can not be unambiguously recognized as a valid or erroneous value, the resistance component is preferably switched at least partially in parallel with the voltage divider before a subsequent measurement of a second voltage value by the measuring device. The first voltage value can now be verified or checked by comparing the first and the second voltage value. If, for example, the first voltage value is a valid voltage value, the second voltage value will only be slightly different. On the other hand, in the event of a fault, ie, for example, in the event of an interruption of a ground, the electronic component with the parallel circuit of voltage divider and resistance component forms a new voltage divider. This creates a measurable change in voltage. An error can be clearly identified.

It is advantageous if, in the method according to the invention, an effective resistance of the voltage divider and of the at least partially parallel-connected component having an electrical resistance is substantially smaller than an electrical internal resistance of the electronic component. As a result, an easily detectable voltage change can be caused in the event of a fault.

In a preferred embodiment of the method according to the invention, the electronic component is designed as a sensor, in particular in a motor vehicle.

In a further preferred embodiment of the method according to the invention, the measuring device is designed as an analog-to-digital converter, in particular integrated into a microcontroller. Here, for example, the above mentioned TC1766 should be mentioned. It is understood that the

Measuring device can also be designed as an external analog-to-digital converter. It is expedient if, in the method according to the invention, the signal voltage range is formed essentially from 0 V to 5 V. This allows the advantageous use of the method for the mentioned 5 V components in electronics.

It is also advantageous if in the method according to the invention, the input voltage range is formed substantially from 0 V to 3.3 V. This allows the advantageous use of the method for the mentioned 3.3 V components in electronics.

It is advantageous if, in the method according to the invention, the component having an electrical resistance is designed as an ohmic resistor. An ohmic resistor is a simple, inexpensive and easy-to-use component that is particularly robust and reliable.

In a particularly advantageous manner, the inventive method can be used to determine a ground break.

Particularly preferred is the use of a method according to the invention in the field of motor vehicle construction.

According to the invention, a device is provided with a voltage divider, switching means and a component having an electrical resistance, wherein the component having an electrical resistance is at least partially switchable parallel to the voltage divider (110, 111, 112) by means of the switching means (121). In a preferred embodiment, the device according to the invention has comparison means for comparing a first and a second voltage value. In particular, this may be a named microcontroller.

Advantageously, the device according to the invention also features that correspond to preferred embodiments of the method according to the invention.

It is preferred if the device according to the invention is suitable for carrying out a method according to the invention.

In a preferred embodiment, the device according to the invention is provided in a motor vehicle.

A motor vehicle according to the invention is equipped with a device according to the invention.

The advantages of the said preferred embodiments of the method according to the invention and of the device according to the invention will now be described comprehensively below. They apply correspondingly for each embodiment.

The measure according to the invention overcomes the disadvantages of the prior art, for example, when operating active 5 V sensors on 3.3 V ADC inputs of modern microcontrollers. The inventive method no external 5V ADC modules must be used, resulting in a cost savings. Furthermore, the present invention allows the operation of active 5V sensors to microcontrollers with 3.3V ADC inputs with full scope of diagnosis, ie also in the prior art undetectable errors such. B. the interruption of the sensor mass are detected.

The solution described can be realized with a few low-cost components. The OBD II standard is advantageously fulfilled. Advantageously, the solution according to the invention has no appreciable influence on the accuracy of the measurement of a voltage value.

Voltage values of active sensors, in particular of safety-relevant character (eg pressure sensors in airbags), can be read in more quickly by a microcontroller than, for example, in the state of the art via the SPI interface of the CY100. The resources of the microcontroller are used more effectively.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below in detail with reference to the drawings.

figure description Figure Ia shows a schematic representation of a device in the prior art;

Figure Ib shows a schematic representation of a preferred embodiment of a device according to the invention; and

FIG. 2 shows a flow chart of a preferred embodiment of the method according to the invention.

FIG. 1 shows the connection of a sensor 100 to a microcontroller 150 in a motor vehicle in the prior art. The sensor 100 has a housing 101, which is indicated schematically by the dashed line. Furthermore, the sensor 100 has a terminal 102 for the supply voltage, in the case shown +5 volts, and a terminal 103 for the mass. The voltage range from 0 V to 5 V, which is represented by an arrow labeled Usens, is therefore available for a sensor or output voltage Us. The potential of the output voltage Us is represented by the arrow marked Us.

The sensor 100 has an output 104 at which the sensor signal Us is provided. The sensor is designed in a so-called pull-up-down circuit. In this circuit, the signal line is connected via resistors to the supply voltage and ground. In the illustration shown, a signal line 104a is connected to the supply voltage 5 V via a pump-up resistor 105 and to the ground 0 V via a pull-down resistor 106. The operation and purpose of such a circuit is well known to those skilled in the art and therefore will not be further elaborated here.

During operation, a sensor voltage in the range between approximately 0.5 V and approximately 4.5 V is available at the output 104 of the sensor 100. The microcontroller 150 has an input 151. In this example, the microcontroller has an input voltage range in the range of 0V to about 3.3V. For this reason, in the prior art, the sensor voltage Us output by the sensor 100 at the output 104 is adapted to the input voltage range of the microcontroller 150 via a voltage divider 110. The voltage divider 110 has two resistors 111 and 112, which have a value R1 and R2, respectively. Since the microcontroller 150 has a relatively high input resistance at its ADC input 151, in the present case the forms for the unloaded voltage divider can be used. Therefore, the input voltage U2 at the ADC input 151 of the microcontroller 150 is calculated to be:

U2 = Us * R2 / (R1 + R2)

If there is a malfunction of the sensor, for example due to an interrupted sensor mass at the connection 103, the sensor 100 loses its functionality. It then provides the output voltage +5 V at the output 104. In this case, a voltage U2 is present at the ADC input 151 of the microcontroller 150, which is calculated as:

U2 = 5V * R2 / (RA + R1 + R2)

U2 is therefore less than 3.3V, which is why microcontroller 150 can not detect a fault. It will now be shown with reference to FIG. 1b how this disadvantage is overcome by the measure according to the invention.

FIG. 1 b shows the schematic illustration from FIG. 1 a together with a resistor 120 and a switch 121. The resistor 120 is connected in series with the switch 121. Furthermore, the resistor 120 is connected to the output signal line 104a. The switch 121 is additionally connected to ground. In the illustrated open position of the switch 121, there are no changes to the behavior explained with reference to FIG. 1a.

In the illustrated circuit arrangement, a complete parallel connection of the resistor 120 to the voltage divider 110 is shown. According to the invention, a partial parallel connection would already be sufficient. In the example shown, this is to be understood in particular as meaning that the resistor 120 would be connected in parallel only to the resistor 111 or the resistor 112.

If the microcontroller 150 detects a voltage value U2 close to 3.3 V at the ADC input 151, it is not in a position to reliably detect an error. As already stated, this may be a regular output value of the sensor 100 or the output value of a defective sensor. The microcontroller 150 now actuates the switch 121, so that the signal line 104a is connected to ground via the resistor 120 and the switch 121. Furthermore, a parallel connection of the resistor 120 to the voltage divider 110 arises. Now two cases can be distinguished. If it is a regular output value of the sensor, no significant change in the voltage U2 will occur, since it is usually a working voltage source for a functioning sensor output. The voltage change will be the smaller, the smaller the internal resistance of this voltage source compared to the total resistance of the parallel-connected resistors Rl + R2 and R3.

In the exemplary error case, i. when the sensor ground is interrupted, the resistors 105, 111, 112 and 120 form an effective voltage divider system. The voltage U2 dropping across the resistor 112 is therefore measurably lower than 3.3 V. By means of this voltage change, the microcontroller 150 can detect a defective sensor and react accordingly.

FIG. 3 shows a preferred embodiment of the method according to the invention as a flow chart. The method starts in a step 200. In one step

201 is measured by the measuring device, such as an ADC, which is integrated in a microcontroller, a first voltage value. In a step 202, the microcontroller checks whether the measured first voltage value is in a voltage range that does not allow an accurate determination of an error. If, for example, a 5 V sensor is operated on a 3.3 V ADC in the form described above, it is advisable, for example, to use a voltage threshold of approximately 3 V. If the measured first voltage value is above 3 V, no definitive statement is possible as to whether it is a regular measured value or the output of a faulty sensor. If the measured first voltage value is below this predefinable voltage threshold value, then the process continues with method step 201. This is the regular operation.

If, in step 202, the measuring device detects a first voltage value which is above the predefinable voltage threshold value, a branch is made to a method step 203.

In step 203, an electrical resistance component, in particular an ohmic resistance, is connected in parallel with the voltage divider. In a subsequent step 204, a second voltage value is measured by the measuring device.

In a method step 205, the first and the second voltage value are compared. If there is no measurable difference between the first and the second voltage value, the parallel connection of the resistance component with the voltage divider is terminated in a method step 206 and the method is returned to method step 201. It is then a regular reading.

If a measurable difference between the first and the second voltage value is detected in method step 205, this is an indication for the measuring device that it is an irregular voltage value and thus the associated sensor is defective. Subsequently, a branch is made into a method step 207.

In method step 207, the defect of the sensor is signaled, for example, to a central control device (not shown). There are other ways to Reaction, e.g. As the logging in an in-vehicle protocol, the notification of the driver, for example by light or sound signal, etc. The method then ends in a step 208.

The described embodiments of the device according to the invention and of the method according to the invention make it possible to improve the operation of components having an output voltage on components having an input voltage which differs from the output voltage.

Claims

claims

1. A method for checking a first voltage value of a in a signal voltage range (Usens) lying, by an electronic component (100) can be output signal voltage (Us), by a measuring device

(150) having an input voltage range smaller than the signal voltage range (Usens) is detectable, wherein a voltage divider (110, 111, 112) transforms the signal voltage range into the input voltage range,

d a d u r c h e s e n c i n e s, d a s s

First, a first voltage value is measured by the measuring device (150), a component (120) having an electrical resistance is connected at least partially in parallel to the voltage divider (110, 111, 112), then a second voltage value is measured by the measuring device (150) and the result of the test is derived from the comparison of the first and second voltage values.

2. The method of claim 1, wherein an error of the electronic component (100) is detected when the first one of the second voltage value differs by at least a predetermined threshold.

3. The method according to claim 1 or 2, characterized in that an effective resistance of the voltage divider (110, 111, 112) and at least partially connected in parallel with an electrical resistance exhibiting component (120) is formed substantially smaller than an internal electrical resistance of the electronic component (100).

4. The method according to any one of the preceding claims, character- ized in that as an electronic component

(100) a sensor is used.

5. The method according to any one of the preceding claims, characterized in that as a measuring device (150), an analog-to-digital converter, in particular integrated in a microcontroller (150) is used.

6. The method according to any one of the preceding claims, characterized in that is used as the signal voltage range (Usens) substantially a range of 0 V to 5 V is used.

7. The method according to any one of the preceding claims, characterized in that as input voltage range substantially a range of 0 V to 3.3 V is used.

8. The method according to any one of the preceding claims, characterized in that as an electrical Resistance exhibiting component (120) an ohmic resistance (120) is used.

9. Use of a method according to any one of the preceding claims, for determining a ground breaking of the electronic component (100).

10. Use of a method according to any one of the preceding claims in the field of motor vehicle construction.

11. Device (110, 111, 112, 120, 121) with a voltage divider, switching means (121) and a component (120) having an electrical resistance,

d a d u r c h e s e n c i n e s, d a s s

the electrical resistance component (120) by means of the switching means (121) the voltage divider (110, 111, 112) is at least partially connected in parallel.

12. Device according to claim 11, characterized by comparison means (150) for comparing a first and a second voltage value.

13. The apparatus of claim 11 or 12, for carrying out a method according to any one of claims 1 to 10.

14. Device according to one of claims 11 to 13, characterized in that it is provided in a motor vehicle.

15. Motor vehicle with a device according to one of claims 11 to 14.