FR3075388A1 - SYSTEM AND METHOD FOR MEASURING VOLTAGE - Google Patents

Abstract

 The measurement system (104) comprises: - a reference voltage source (106); - a voltage measuring device (108); - a switch (126) designed to connect the input (110) of the voltage measuring device (108) alternately to the reference voltage source (106) and to the voltage source to be measured (102).  The voltage measuring device (108) comprising a memory (120) in which the reference voltage (V *) is stored, and being designed to: - control the switch (126) so as to connect the input (110) at the reference voltage source (106), then producing a measurement (V * M) of the reference voltage (V *); - control the switch (126) so as to connect the input (110) to the source of voltage to be measured (102), then produce a measurement (VM1) of the voltage to be measured (V); - determine a corrected measurement (VM2) of the voltage to be measured (V) from the reference voltage (V *) recorded in the memory (120), from the measurement (V * M) of the reference voltage (V *) and the first measurement (VM1) of the measured voltage (V).

Description

SYSTEM AND METHOD FOR MEASURING A VOLTAGE

TECHNICAL AREA

The present invention relates to a system and method for measuring a voltage, particularly applicable to the field of motor vehicles.

TECHNOLOGICAL BACKGROUND

It is known to measure a voltage supplied by a voltage source, such as a motor vehicle battery, using a voltage measurement device having an input connected to the voltage source. Such a voltage measurement device usually comprises a voltage divider connected to the input and having an output connected to an analog digital converter of a microcontroller carrying out the measurement.

The object of the invention is to improve the accuracy of the measurement.

SUMMARY OF THE INVENTION

To this end, a system for measuring a voltage to be measured provided by a voltage source to be measured is proposed, comprising:

- a reference voltage source designed to provide a reference voltage,

- a voltage measuring device having an input,

a switch designed to connect the input of the voltage measurement device alternately to the reference voltage source and to the voltage source to be measured, the voltage measurement device comprising a memory in which the reference voltage is recorded, and being designed for:

- control the switch so as to connect the input of the voltage measurement device to the reference voltage source, then produce a measurement of the reference voltage,

- control the switch so as to connect the input of the voltage measurement device to the voltage source to be measured, then produce a measurement of the voltage to be measured,

- determine a corrected measurement of the voltage to be measured from the reference voltage recorded in the memory, from the measurement of the reference voltage and from the first measurement of the measured voltage.

Thanks to the invention, it is possible to correct the variations over time of the gain of the measurement chain from the input of the voltage measurement device until the production of the voltage measurement.

Optionally, the switch is further designed to disconnect the voltage measuring device from both the reference voltage source and the voltage source to be measured so that the voltage measuring device receives a zero voltage, and the voltage measurement device is further designed to:

- control the switch so as to disconnect the voltage measuring device from both the reference voltage source and the voltage source to be measured, then produce a no-load voltage measurement, and the determination of the corrected measurement of the voltage to be measured is also obtained from the no-load voltage measurement.

Also optionally, the corrected measurement of the voltage to be measured is determined from the following formula:

V *

Vm2 ⁼ (Vmi ^- V _M0 ) 77T 77 7

Çv _M - v _M0 ;

where: V * is the reference voltage recorded in the memory, Vmo is the no-load voltage measurement, V * m is the reference voltage measurement, Vmi is the measurement of the voltage to be measured and Vm2 is the corrected measurement of the voltage to be measured.

Also optionally, the voltage measurement device includes a voltage divider designed to divide the voltage applied to the input.

Also optionally, the switch comprises a first controllable switch connected between the reference voltage source and the input and a second controllable switch connected between the voltage source to be measured and the input.

a motor vehicle is also proposed comprising:

- a voltage source to be measured designed to supply a voltage to be measured,

- a system for measuring the voltage to be measured according to the invention.

Also optionally, the voltage source to be measured comprises a battery.

also proposed is a method for measuring a voltage to be measured supplied by a voltage source to be measured, comprising:

- the control of a switch designed to connect an input of a voltage measuring device alternately to a reference voltage source supplying a reference voltage and to the voltage source to be measured, so as to connect the input of the voltage measurement device at the reference voltage source, then the production of a measurement of the reference voltage,

- control of the switch so as to connect the input of the voltage measurement device to the voltage source to be measured, then the production of a measurement of the voltage to be measured,

- the determination of a corrected measurement of the voltage to be measured from the reference voltage recorded in a memory, from the measurement of the reference voltage and from the first measurement of the measured voltage.

DESCRIPTION OF THE FIGURES

Figure 1 is an electrical diagram of an electrical system implementing a system according to the invention for measuring a voltage.

FIG. 2 is a block diagram illustrating the steps of a method according to the invention for measuring a voltage.

DETAILED DESCRIPTION

With reference to FIG. 1, an electrical system 100 implementing the invention will now be described. The electrical system 100 is for example intended to be integrated into a motor vehicle.

The electrical system 100 firstly comprises a voltage source to be measured 102 designed to present a voltage to be measured V, defined with respect to an electrical mass of the electrical system 100. The voltage source to be measured 102 is intended to supply devices of the motor vehicle and comprises for example a battery.

The electrical system 100 further comprises an electric motor 105 having several phases, as well as an inverter 107 connected between the voltage source to be measured 102 and the electric motor 105, in order to supply the electric motor 105 with phase voltages from the voltage to be measured V.

The electrical system 100 further includes a system 104 for measuring the voltage to be measured V.

The measurement system 104 firstly comprises a reference voltage source 106 designed to supply a reference voltage V *.

The measurement system 104 further includes a voltage measurement device 108 having an input 110. The voltage measurement device 108 is designed to provide a measurement of an input voltage applied to its input 110.

In the example described, the voltage measuring device 108 firstly comprises a voltage divider 112 connected to the input 110 to receive the input voltage and designed to multiply the input voltage by a factor A lower at 1, in order to obtain an output voltage Vs. The voltage divider 112 also has an output 114 designed to supply the output voltage Vs. In the example described, the voltage divider 112 has two resistors Ri, R ₂ connected between the input 110 and the electrical ground, and connected to each other at a midpoint forming the output 114. Thus, the factor A is worth:

r ₂ ^A “Ri + R ₂

In the example described, the voltage measuring device 108 further comprises a capacitor C connected between the output 114 of the voltage divider 112 and the ground so as to smooth the output voltage Vs of the voltage divider 112.

In the example described, the voltage measurement device 108 also includes a processing device 116, such as a microcontroller. The processing device 116 comprises an analog-digital converter 118 connected to the output 114 of the voltage divider 112 in order to digitize the output voltage Vs of the voltage divider 112. The processing device 116 further comprises an output 119, a memory 120 and a digital processor 122 connected to the analog-to-digital converter 118, to the output 119 and to the memory 120. In the memory 118 are stored the reference voltage V * and two sets of instructions 124, 125 intended to be executed by the processor digital 122 so that the latter implements the steps which will be described later, with reference to FIG. 2. The first set of instructions 124 is designed to provide a measurement Vm2 of the voltage to be measured V, this measurement being precise as will be explained later. The second set of instructions is designed to control the inverter 107 from, in particular, the Vm2 measurement in order to improve the performance of the electric motor 105.

The measurement system 104 further comprises a switch 126 designed to connect the input 110 of the voltage measuring device 108 alternately to the reference voltage source 106 so that the reference voltage V * is applied to the input 110 and to the voltage source to be measured 102 so that the voltage to be measured V is applied to the input 110. In the example described, the switch 126 comprises a first controllable switch 128 connected between the reference voltage source 106 and the input 110, and a second controllable switch 130 connected between the voltage source to be measured 102 and the input 110. The controllable switches 128, 130 respectively comprise, for example, transistors, such as insulated gate field effect transistors, more commonly called MOSFET (acronym for “Metal Oxide Semiconductor Field Effect Transistor”). Alternatively, bipolar transistors or micro-relays can be used.

With reference to FIG. 2, a method 200 for measuring the voltage to be measured V implemented by the measurement system 104 will now be described.

During a step 202, the digital processor 122, executing the instruction set 124, controls the switch 126 to open the controllable switches 128, 130 so as to disconnect the input 110 from the voltage measurement device 108 at the times from the reference voltage source 106 and the voltage source to be measured 102. Thus, the input 110 is free and the output 114 of the voltage divider 112 provides a zero output voltage Vs, which is received by the converter analog digital 118.

During a step 204, the digital processor 122, executing the instruction set 124, produces a so-called no-load measurement Vmo and stores it in memory 120. In theory, the no-load measurement Vmo should be zero. However, the analog to digital converter 118 generally has an offset (“offset” in English) which is found in the no-load measurement Vmo.

During a step 206, the digital processor 122, executing the instruction set 124, controls the switch 126 to close the first controllable switch 128 and open the second controllable switch 130, so as to connect the input 110 to the reference voltage source 106. Thus, the reference voltage V * is applied to the input 110.

During a step 208, the digital processor 122, executing the instruction set 124, produces a measurement V * m of the reference voltage V * and stores it in the memory 120. In theory, the measurement V * m should be equal to the reference voltage V *. However, this is not the case due to the offset of the analog to digital converter 118. In addition, the value of the resistors RI, R2 may drift depending on the ambient temperature, so that the factor A may have changed. Thus, in the example described, the measurement V * m is linked to the reference voltage V * by the following formula:

V * _m = AV * + V _mo

During a step 210, the digital processor 122, executing the instruction set 124, controls the switch 126 to open the first controllable switch 128 and close the second controllable switch 130, so as to connect the input 110 to the voltage source to be measured 102. Thus, the voltage to be measured V is applied to the input 110.

During a step 212, the digital processor 122, executing the instruction set 124, produces a measurement Vmi of the voltage to be measured V and stores it in the memory 120. In theory, the measurement Vmi should be equal to the voltage to be measured V. However, this is not the case because of the offset of the analog-digital converter 118 and of the drift of the factor A. Thus, in the example described, the measurement Vmi is linked to the voltage to be measured V by the following formula:

V mi ⁼ AV + V _M o

During a step 214, the digital processor 122, executing the instruction set 124, determines a corrected measurement Vm2 of the voltage to be measured V from the reference voltage V *, of the no-load measurement Vmo, of the measurement V * m of the reference voltage V * and of the measurement Vmi of the measured voltage V which are recorded in the memory 120. The corrected measurement Vm2 is intended to be more precise than the measurement Vmi. In the example described, the corrected measurement Vm2 is determined from the following formula, which results from the combination of the two previous formulas:

V *

Vm2 ⁼ (Vmi ^- V _mo ) —— - (v _M - v _Mo j

During a step 216, the digital processor 122, executing the instruction set 124, supplies the corrected measurement Vm2.

During a step 218, the digital processor 122, executing the instruction set 125, controls the inverter 107 on the basis in particular of the corrected measurement Vm2.

Preferably, the measurement steps 204, 208, 212 are carried out in a short time interval, so that the offset and the factor A remain substantially constant. This time interval depends on the thermal inertia of the electronic card on which the voltage measurement device 108 is placed. For example, in some cases, the time interval can be less than or equal to 1 s.

In addition, preferably, the method 200 is repeated during the operation of the motor vehicle, in order to know the evolution of the voltage to be measured V during this operation.

The present invention is not limited to the embodiment described above. It will in fact be apparent to those skilled in the art that modifications can be made to it.

In particular, the pairs of steps 202/204, 206/208 and 210/212 could be carried out in a different order than that described above.

Furthermore, in another embodiment, steps 202, 204 could be omitted. Thus, the corrected measurement Vm2 would be obtained without using a vacuum measurement Vmo. For example, the corrected measurement Vm2 could be obtained from the following formula:

V *

Vm2 ⁼ Vmi ^v M

In addition, the processing device 116 could be produced by one or more pre-wired electronic components which do not involve a computer program, for example by one or more reprogrammable integrated circuits, such as FPGAs. "Field-Programmable Gate 5 Array").

In addition, in another embodiment of the invention, the electrical system 100 includes a voltage source to be measured 102 and a DC / DC converter operating an energy transfer from a low voltage network (for example 12V) to a high voltage network (for example 48V). The voltage converter uses the measurement system 104 in order to provide a vehicle supervision unit with precise information on the voltage state of the battery, in this case the Vm2 measurement, and to allow the latter to whether to authorize the transfer of energy from one network to another (from the low voltage network to the high voltage network or vice versa).

Claims (9)

1. Measuring system (104) of a voltage to be measured (V) supplied by a source of voltage to be measured (102), comprising: - a reference voltage source (106) designed to supply a reference voltage (V *), - a voltage measuring device (108) having an input (110), - a switch (126) designed to connect the input (110) of the voltage measuring device (108) alternately to the reference voltage source (106) and to the voltage source to be measured (102), the voltage measurement (108) comprising a memory (120) in which the reference voltage (V *) is recorded, and being designed to: - control the switch (126) so as to connect the input (110) of the voltage measuring device (108) to the reference voltage source (106), then produce a measurement (V * m) of the voltage reference (V *), - control the switch (126) so as to connect the input (110) of the voltage measuring device (108) to the voltage source to be measured (102), then produce a measurement (Vmi) of the voltage to be measured ( V) - determine a corrected measurement (Vm2) of the voltage to be measured (V) from the reference voltage (V *) recorded in the memory (120), from the measurement (V * m) of the reference voltage (V *) and the first measurement (Vmi) of the measured voltage (V). 2. Measuring system (104) according to claim 1, wherein the switch (126) is further designed to disconnect the voltage measuring device (108) both from the reference voltage source (106) and from the voltage source to be measured (102) so that the voltage measuring device (108) receives zero voltage, and in which the voltage measuring device (108) is further designed to: - controlling the switch (126) so as to disconnect the voltage measuring device (108) from both the reference voltage source (106) and the voltage source to be measured (102), then produce a measurement of no-load voltage (Vmo), and in which the determination of the corrected measurement (Vm2) of the voltage to be measured (V) is carried out further from the no-load voltage measurement (Vmo). 3. Measuring system (104) according to claims 1 and 2 taken together, in which the corrected measurement (Vm2) of the voltage to be measured (V) is determined from the following formula: V * Vm2 ⁼ (Vmi ^- V _M0 ) 7777 7 T l ^v _M - v _Mo j where: V * is the reference voltage recorded in the memory (120), Vmo is the no-load voltage measurement, V * m is the measurement of the reference voltage, Vmi is the measurement of the voltage to be measured and Vm2 is the corrected measurement of the voltage to be measured. 4. Measuring system (104) according to any one of claims 1 to 3, in which the voltage measuring device (108) comprises a voltage divider (112) designed to divide the voltage applied to the input (110). 5. Measuring system (104) according to any one of claims 1 to 4, in which the switch (126) comprises a first controllable switch (128) connected between the reference voltage source (106) and the input (110) and a second controllable switch (130) connected between the voltage source at measure (104) and the input (110). 6. Motor vehicle comprising: - a voltage source to be measured (102) designed to supply a voltage to be measured (V), - a measurement system (104) of the voltage to be measured (V) according to any one of claims 1 to 5. 7. Motor vehicle according to claim 6, wherein the voltage source to be measured (102) comprises a battery. 8. Method for measuring (200) a voltage to be measured (V) supplied by a source of voltage to be measured (102), comprising: - the control (206) of a switch (126) designed to connect an input (110) of a voltage measuring device (108) alternately to a reference voltage source (106) supplying a reference voltage (V *) and to the voltage source to be measured (102), so as to connect the input (110) of the voltage measuring device (108) to the reference voltage source (106), then the production (208) a measurement (V * m) of the reference voltage (V *), - the command (210) of the switch (126) so as to connect the input (110) of the voltage measuring device (108) to the voltage source to be measured (102), then the production (212) of a measurement (Vmi) of the voltage to be measured (V), - determination (214) of a corrected measurement (Vm2) of the voltage to be measured (V) from the reference voltage (V *) recorded in a memory (120), of the measurement (V * m) of the reference voltage (V *) and the first measurement (Vmi) of the measured voltage (V). 1/1 Figure 1 100r- 104 Figure 2 FRENCH REPUBLIC irai - I NATIONAL INSTITUTE PROPERTY INDUSTRIAL PRELIMINARY SEARCH REPORT based on the latest claims filed before the start of the search National registration number FA 847198 FR 1762538 DOCUMENTS CONSIDERED AS RELEVANT Relevant claim (s) Classification attributed to the invention by ΙΊΝΡΙ Category Citation of the document with indication, if necessary, of the relevant parts US 2005/248351 Al (GRAF HANS-MICHAEL [DE]) November 10, 2005 (2005-11-10) * whole document * US 2007/176592 Al (HONDA KOUHEI [JP] AND AL) August 2, 2007 (2007-08-02) * abridged; Figures 1,3,6 * * paragraphs [0002], [0005] - [0007], [0022], [0033] - [0034], [0040] [0045], [0049], [0051], [0057 ] - [0061] US 4,243,975 A (MASUDA EIJI ET AL) January 6, 1981 (1981-01-06) * abridged; figures 1,3,8 * * column 2, line 65 - column 3, line 4 * column 3, line 44 66 * * column 9, line 62 62 * column 3, row column 10, row KR 2010 0057278 A (KOREA ELECTROTECH RES INST [KR]) May 31, 2010 (2010-05-31) * paragraphs [0029] - [0031], [0035]; figures 1-2 * 1-8 1-8 1-8 G01R19 / 00 G01R31 / 36 TECHNICAL AREAS SOUGHT (IPC) G01R EPO FORM 1503 12.99 (P04C14) CATEGORY OF DOCUMENTS CITED X: particularly relevant on its own Y: particularly relevant in combination with another document in the same category A: technological background O: unwritten disclosure P: intermediate document Research completion date September 17, 2018 Examiner Marie, Viktor T: theory or principle underlying the invention E: patent document with a date prior to the filing date and which was only published on that filing date or on a later date. D: cited in the request L: cited for other reasons &: member of the same family, corresponding document ANNEX TO THE PRELIMINARY RESEARCH REPORT RELATING TO THE FRENCH PATENT APPLICATION NO. FR 1762538 FA 847198 This appendix indicates the members of the patent family relating to the patent documents cited in the preliminary search report referred to above. The said members are contained in the computer file of the European Patent Office on the date dul / “09-Z018 The information provided is given for information only and does not engage the responsibility of the European Patent Office or the French Administration EPO FORM P0465 Patent document cited in the research report Publication date Patent family member (s) Publication date US 2005248351 Al 10-11-2005 DE 102004022556 B3 27-10-2005 FR 2869999 Al 11-11-2005 US 2005248351 Al 10-11-2005 US 2007176592 Al 02-08-2007 JP 4733530 B2 27-07-2011 JP 2007205725 A 16-08-2007 US 2007176592 Al 02-08-2007 US 4243975 A 06-01-1981 JP S5451454 A 23-04-1979 US 4243975 A 06-01-1981 KR 20100057278 A 31-05-2010 NONE