FR2832219A1 - Testing of the operation of power electronic stages, such as FET switches, using a single microcomputer testing device that is able to detect and classify shorts to earth and the power supply voltage as well as a cable breakage - Google Patents

Abstract

Method for testing the functioning of an electrical power stage (4) and for detection of a short-circuit in the power stage relative to the power supply voltage or relative to earth and for detection a cable breakage. The electrical power stage or load is a switch controlled by a microcomputer (1) via a command bus (6). The power stage is linked to a digital diagnostic port (12) of the microcomputer and fault states are recognized by reading of the states of the diagnostic port and be reading the charge state of a memory element (7). The invention also relates to a corresponding circuit for implementation of the inventive method.

Description

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Technical area
The present invention relates to a method for diagnosing or controlling the operation of an electrical power stage and detecting a short circuit of the power stage, with respect to the supply voltage, with respect to the earth. and at a cable break, the electrical consumer and a switching element associated therewith are controlled by a microcomputer (pC) by a control line.

 In the known solutions for diagnosing semiconductor power stages, for example a power stage comprising discrete FET field effect transistors, the voltage applied instantaneously to the power stages (drain / source voltage) is applied to these stages. which is registered by an analog port and is transformed into a numeric value.

State of the art
According to the document EP-0-516 633 BI, a method and a device for monitoring the operation of an electrical consumer are known. By comparing a signal used to control the consumer and a feedback signal applied to the control circuit, the operation of an electrical consumer controlled by the control circuit is monitored. The feedback signal is influenced by an RC element connected between the supply voltage and the ground. In order to detect a short circuit of the consumer with respect to the ground, with respect to the power supply voltage or a line break between the control circuit and the consumer, at least one time-phased comparison interrogation is carried out during and after the switching event applied to the consumer.

Presentation of the invention
The present invention relates to a method of the type defined above, characterized in that the electrical power stage is connected to a digital diagnostic port of the microcomputer, and the states of defects are recognized by reading the states of the diagnostic port. at the output of the electrical switching element and by reading the state of charge of a memory element. So thanks to the solution according to

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l'invention on développe un concept de diagnostic qui contourne l'exploitation analogique par un port séparé, réservé analogique/numérique, et exploite directement l'information drain/source au niveau du port numérique.

the invention develops a diagnostic concept that bypasses analog operation by a separate port, reserved analog / digital, and directly exploits the drain / source information at the digital port.

The method according to the invention makes it possible to determine the cases of error necessary for the diagnosis of the power stage, namely the short-circuit with respect to the supply voltage, the short-circuit to the ground and the cutoff of cable, and that with a reduced number of components on the power stage. To diagnose the three error cases mentioned above, only a digital port that has input / output functionality is required. This has the advantage of releasing on the microprocessor a valuable analog / digital port, which greatly expands the branching variants of the microcomputer (uC).

If the detection of the fault state "short circuit to the supply voltage" when the electrical switching element is in the connected state is by reading the high level status of the diagnostic port, advantageously the electrical consumer is connected in its connection state by the switching element during the reading.

If the detection of the "short circuit to ground" fault state occurs in the cut-off state of the electrical switching element by reading a "low level" state of the diagnostic port, advantageously the electrical consumer is connected by the switching element when playing in its cut state.

If the detection of the fault state "cable cut" is done by a combined operation of the evolution of the level of the states of the diagnostic port and their evolution over time, advantageously during the first reading of the state "low level" of the diagnostic port, in the state of cut of the electrical consumer and after a waiting time Tl = 3 x R2 x Cl, one reads again the state "high level" of the port of diagnosis and one detects the fault state "cable cut".

If, in order to detect the fault state "cable cut" for an intact state of the system, the capacitor CI is loaded according to the state "high level" of the port of the diagnosis and the port of the diagnosis is read, from

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 preferably after the first reconfiguration of the digital diagnostic port after a time t2 = f (R1, R2, C1) a second reconfiguration of the digital diagnostic port on "input" and when reading a "low level" state from the diagnostic port, the fault state "cable cut-off" is recognized, and when reading the "high level" status of the diagnostic port it is concluded that the system is operating correctly.

d'attente TI > 3 x RI x Cl, on fait une re-configuration du port de diagnostic numérique sur"entrée"et on lit l'état du port numérique du condensateur. Dans ce cas lors de la lecture de l'état"niveau haut"du port de diagnostic on conclut à l'état de défaut"coupure de câble", ou alors lors de la lecture de l'état"niveau bas"du port numérique on conclut à l'état de défaut"court circuit à la masse". If for the detection of the fault state "cable cut" is made a re-configuration of the digital diagnostic port of the microcomputer on "output: up", then for example after a time

Wait time TI> 3 x RI x Cl, the digital diagnostic port is reset to "input" and the state of the capacitor digital port is read. In this case, when reading the "high level" status of the diagnostic port, it is concluded that the fault condition is "cable cut", or else when reading the "low level" status of the digital port. we conclude in the state of default "short circuit to ground".

 The invention also relates to the implementation of the method, a circuit characterized in that it comprises a microcomputer controlling by a digital port a switching element which switches the electrical consumer, a capacitor CI and a protection resistor RI and a lift resistor R2, and the electrical consumer is connected to a digital diagnostic port of the microcomputer.

 On another characteristic of the circuit it comprises a microcomputer controlling by a digital port a switching element switching the electrical consumer, a capacitor C1 and a protection resistor RI, and the electrical consumer is connected by a digital diagnostic port of the microcomputer.

drawings
The present invention will be described in more detail below with reference to the accompanying drawings in which: FIG. 1 shows a circuit with a diagnostic path for different cases using an analog / digital converter,

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 FIG. 2 shows a circuit using a digital port with an I / O input / output function as a diagnostic port; FIG. 3 shows a circuit variant optimized for components for the circuit of FIG. 2; FIG. 4 shows the execution of a diagnosis using the circuit of FIG. 2; FIG. 5 shows an extension of the diagnosis flow of FIG. 4; FIG. 6 shows the execution of a diagnosis using the FIG. circuit of Figure 3.

Description of the embodiments
Figure 1 shows a circuit representing the signal scheme for diagnosing the error states of a power stage using the port of an analog / digital converter.

 According to the circuit of FIG. 1 of a microcomputer (uC), the line connected to an analog ratio 2 comprises a protection resistor 9 (RI). A power stage transistor 4 is controlled by a digital port 3 and a control line 6; the control line 6 is connected to the base 5 of the transistor 4 forming the power stage. In this embodiment, the transistor 4 of the power stage replaces a power stage that switches an external load. Instead of the transistor 4 represented here, it is also possible for this power stage transistor to have an MOS-FET transistor or an integrated power stage in the form of an integrated circuit IC. Depending on the electronic component 4 used, the reference 5 designates either the base of the transistor as indicated either a gate of a MOS-FET transistor or a control pin of a power stage integrated circuit without proper diagnosis. In the embodiment shown, it is a power stage transistor 4 whose base of the transistor carries the reference 5.

 In general, a connection capacitor 7 (Cl) is associated with the connector 13 of the control apparatus to improve the protection against EMV electromagnetic interference.

 A support capacitor 8 (C2) is associated with the protection resistor 9 (RI). The resistor (9) (RI) and the capacitor of

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 Support 8 (C2) is a low pass filter for eliminating spurious signals. In addition, the support capacitor 8 (C2) acts in the sense of stabilization on the analog voltage and improves the accuracy of the result of the conversion. The resistor (RI) carries the reference 9 constitutes at the same time a protection resistor while the resistors 10 and 11 (R2, R3) placed behind the protection resistor 9 (RI), are necessary for the diagnosis of the cable break . The resistors 10 (R2) and 11 (R3) form a voltage divider for the supply voltage Vx. The voltage 14 which is established is a diagnostic value corresponding to the cable cut error situation.

 The diagnostic function of this circuit will be described below: To diagnose the case of a short-circuit fault at the supply voltage, a high level is established when the power stage is connected via the device connector. 13. The fault is recognized by reading the analog value when power stage 4 is connected. The short-circuit ground fault case is diagnosed in that it is set low on the connector 13 of the apparatus when the power stage 4 is cut. The fault is recognized when the power stage 4 is cut by the reading of the analog value. The cable cutoff fault case is recognized when the power stage 4 is cut, by reading the analog value. The value U is defined by the division ratio of the resistors 9, i.e. the resistors (R1, R2); this value is generally between OV and Vx. Recognition of this signal voltage that is to say the diagnosis of a cable cut is possible exclusively using a port A / D converter (analog / digital) 2 of the microcomputer 1.

 Figure 2 shows an alternative embodiment of a digital diagnostic port circuit instead of the A / D converter port of the microcomputer (pC).

 The circuit according to FIG. 2 comprises a microcomputer (uC) 11 which comprises a digital diagnostic port 12 as well as a digital port 3. In the diagnostic line there is a protection resistor 9 (RI); by the command line 6 from the digital port

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teur 7 (Cl) auquel est associé l'appareil de commande ou le connecteur 13 de l'appareil de commande. that 3 one controls the base 5 of the transistor 4 (Tl) constituting the power stage. The circuit further comprises a connection capacitor

7 (Cl) with which is associated the control unit or the connector 13 of the control unit.

 Connector capacitor 7 (Cl) is used in the diagnosis method described for diagnostic purposes. The circuit further comprises, according to the first variant, a resistor 10 for diagnosing the cable break. Resistor R2 with reference numeral 10 is also referred to as lift resistor to Vx.

 Figure 3 shows a second component optimized circuit with a digital diagnostic port 12 on the microcomputer 2 as a diagnostic input.

 The circuit of FIG. 3 essentially corresponds to the circuit already shown in FIG. 2, with the difference, however, that the variant of the circuit of FIG. 3 does not include a lifting resistor 10 (R2). According to this second embodiment of the circuit, an additional component is saved in the form of a resistor.

 The representation of FIG. 4 corresponds to the execution of a diagnosis with the circuit of FIG. 2.

Figure 4: Diagnosis table and flow diagram.

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Reference 22 designates the low level of the diagnostic port while reference 23 designates its high level.

 According to the diagnostic flow diagram according to FIG. 4, a fault state 28 is detected short circuit to the voltage

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 by the level of diagnosis 23 that is established. The fault is recognized by reading the status of the diagnostic port when the connected electrical consumer 15 is in the branch state 20 of the power stage in the control apparatus. A short-circuit ground fault condition is recognized in that a low level 22 is set on the connector 13 of a cutoff state 21 at the power stage 4. The fault is recognized by the reading of the state of the diagnostic port 22 when the power stage 4 is cut off. If in cut state 21 of power stage 4 there is a high level 23 on the diagnostic port, this is interpreted as corresponding to a correct state of system 27.

 The recognition of the state of failure of cable cut is done by a combined operation of the diagnostic port levels 22 or 23 and the chronology of this level. When the electrical consumer is connected, the capacitor 7 (Cl) of the circuit of FIG. 2 is discharged by the connected power stage. It is established a low level 22 on the diagnostic port 12. After the power stage is cut off, for the case of ground short-circuit fault, a low level 22 permanently applied is established. The state of the respective diagnostic port 22 or 23 is read directly after the cut-off 21 of the power stage 4. When a low level 22 is used, it is necessary that in the next step 25 a distinction is made between the state fault 30 short circuit to ground and fault state 29 cable break. In the presence of the fault state 29, the capacitor 7 (Cl) is charged by the lifting resistor 10 according to the time constant T1 = R2Cl.

After the duration T1 (that is 3xR2xCl), it is possible to read in the state of failure 29 cable cut by the digital diagnostic port 12 of the microcomputer 1, a high level 23. In the third state of ground short-circuit fault diagnostic port signal level remains low 22.

 The circuit of FIG. 2 also makes it possible to carry out a diagnosis according to the flowchart shown in FIG. 5. In order to recognize the state of fault 29 cable break, the diagnosis is made as follows:

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Après le temps T2 supérieur à 5xR1xC 1 ou pour un sys- 1-P tème 27 intact, la résistance de relevage 10 (R2) permet de charger directement par le consommateur électrique ou dans l'état de défaut 28 court-circuit à la tension d'alimentation le condensateur 7 (Cl) au niveau haut 23. Cet état de niveau haut 23 est enregistré par le port de diagnostic numérique 12 du micro ordinateur 1. Dans l'étape suivante du procédé, le port de diagnostic numérique 12 est soumis à une transformation de configuration 34 sur la sortie bas. La résistance de protection 9 (RI) est traversée par un courant appliqué au port de diagnostic numérique 12 du micro ordinateur 1. À la fin de la durée 35, (T2), qui dépend du dimensionnement de la résistance de protection 9 (RI), de la résistance de relevage (R2) et du dimensionnement du condensateur 7 (Cl), le port de diagnostic 12 est soumis à une nouvelle reconfiguration 36 à l'entrée. Dans l'étape qui suit directement, le potentiel est lu sur le port de diagnostic 12 pour être exploité. En cas d'état correct du système 27, après une reconfiguration 36, on a toujours un niveau haut 23 comme signal de diagnostic sur le port de diagnostic numérique 12. La sortie bas du port de diagnostic numérique 12 pendant la reconfiguration 34 pour le courant arrivant dans le port de diagnostic numérique 12 est injecté par la tension de batterie appliquée au branchement du consommateur électrique 15. La charge du condensateur 7 (Cl) reste ainsi conservée et est appliquée par le seuil de reconnaissance du niveau haut 23 du port de diagnostic numérique 12. On reconnaît l'état du système en ordre 27.

After the time T2 greater than 5xR1xC 1 or for an intact system 27, the lifting resistor 10 (R2) makes it possible to charge directly by the electrical consumer or in the state of default 28 short circuit to the voltage This high level state 23 is recorded by the digital diagnostics port 12 of the microcomputer 1. In the next step of the method, the digital diagnostic port 12 is subjected to a high level state 23. at a configuration transformation 34 on the low output. The protection resistor 9 (RI) is traversed by a current applied to the digital diagnostic port 12 of the microcomputer 1. At the end of the duration 35, (T2), which depends on the dimensioning of the protection resistor 9 (RI) , of the lifting resistor (R2) and the dimensioning of the capacitor 7 (Cl), the diagnostic port 12 is subjected to a new reconfiguration 36 at the input. In the step that follows directly, the potential is read on the diagnostic port 12 to be exploited. In case of correct state of the system 27, after a reconfiguration 36, there is always a high level 23 as a diagnostic signal on the digital diagnostic port 12. The low output of the digital diagnostic port 12 during the reconfiguration 34 for the current arriving in the digital diagnostic port 12 is injected by the battery voltage applied to the connection of the electrical consumer 15. The charge of the capacitor 7 (Cl) thus remains and is applied by the recognition threshold of the high level 23 of the diagnostic port 12. The state of the system is recognized in order 27.

 On the contrary, if the fault state 29 is cut off, the capacitor 7 (Cl) of the circuit of FIG. 2 discharges via the pin of the port. After a finite period, a voltage is established across the capacitor 7 (Cl) depending on the voltage ratio of the divider formed by the protection resistor 9 (RI) and the resistor 10 (R2) and the fall The dimensioning of the protection resistor 9 (RI) must be chosen so that a voltage is established on the capacitor 7 (Cl) situated below the threshold of the low level characteristic. digital diagnostic port 12. Directly after reconfiguration 36 of the digital diagnostic port 12 from

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   output: low at the input, this low level 22 can be read and the second fault state 29 cable cut can be recognized.

 In operation of dynamically varying signals it is necessary to select a time constant of appropriate size for capturing the evolution of the signal or voltage levels in time frames predetermined by the program. The large sizing values for the lift resistor 10 (R2) and the capacitor 7 (Cl) must be selected.

signaux 22, 23. Après un temps de décharge fini 35 (T2) on peut avoir le niveau de tension du condensateur 7 (Cl) directement après la reconfi- guration 34 sur 36 du port de diagnostic numérique 12. Un autre avantage est le diagnostic de l'étage de puissance pendant le cycle de fonctionnement par la répétition de l'opération de diagnostic décrite sans avoir à brancher et à couper le consommateur électrique. The advantage of this diagnostic process lies in the almost time-independent operation for the levels of

22, 23. After a finite discharge time (T2), the capacitor 7 (Cl) voltage level can be directly after reconfiguration 34 of 36 of the digital diagnostic port 12. Another advantage is the diagnosis. of the power stage during the operating cycle by repeating the described diagnostic operation without having to connect and cut the electrical consumer.

 Figure 6 shows the execution of a diagnosis using the circuit of Figure 3 without the lifting resistor.

 The short-circuit fault diagnosis for the supply voltage and ground fault condition are in the same way as for the circuit of FIG. 2 and in connection with the circuit. the diagnostic steps according to Figures 4 and 5.

 The distinction between the state of failure of the cable cut-off and the short-circuit ground fault state is made according to the method described hereinafter. The electrical consumer being connected, the capacitor 7 (Cl) discharges through the power stage 4, connected. It is thus established on the digital diagnostic port 12, a low level 22.

After switching off the electrical consumer 15 or in the state of failure 30 short circuit to ground a permanent low level 22 is established. Relative to this, in the state of failure 28 short circuit to the supply voltage or for an intact state 27 will have on the digital diagnostic port 12 immediately a high level 23. On the contrary because of the diagnostic port 12 of the microcomputer 1 (pC) there will be a low level 22 in the cut state 21, so that in a second step of the method an analysis of the state of de-

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 must be shorted to the ground of the fault condition 28 cable cut II. For diagnosis of the fault state 29 cable cutoff is connected the digital diagnostic port 12 of the microcomputer 1 by a reconfiguration 31 on output: high. In the presence of a fault condition 29, the capacitor 7 (Cl) is charged with the current controlled by the microcomputer 1.

 At the end of the duration T3 = f (R1, C1 and iuC), which is a function of the protection resistor 9, the capacitor 7 and the capacity of the pilot port of the microcontroller, and which corresponds as a first approximation to the copied relationship T3> R1xC1, the capacitor 7 (Cl) is charged to a high level 23. Then 32 is reconfigured the digital diagnostic port 12 on the microcomputer 1, to pass on input and the high level 23 of the capacitor 7 (Cl ) can be read.

This chronological evolution of the voltage on the capacitor 7 (Cl) is established exclusively in the context of the state of failure 29 cable cut.

 On the other hand if after the time T3, there is a low level 22 on the digital diagnostic port 12 of the microcomputer, it is the state of failure 30 short circuit to ground.

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 NOMENCLATURE 1 PC microcomputer 2 Analog / digital port 3 transistor control port 4 Tl transistor power stage 5 transistor base 6 Control line 7 capacitor (EMV) Cl.

8 support capacitor C2 9 protection resistor RI 10 lift resistor R2 for cable cut diagnostic 11 resistor R3 for cable cut diagnostic (voltage divider with R2) 12 digital diagnostic port 13 device collector control ; connection 14 voltage on the voltage dividers 15 electrical consumer 20 connection status of the electrical power stage 21 state of failure of the electrical power stage 22 low level signal-diagnostic port 12 23 high-level signal port diagnostic 12 24 time constant tl R2 x Cl 25 branch 26 time period T1> 3 x R2 x Cl 27 system status in order 28 fault status-i short circuit at supply voltage 29 fault condition: power failure fault condition: shorted to earth 31 reconfiguration of the diagnostic port output: up 32 reconfiguration of the diagnostic port input 33 waiting time T2> 5 x RI x CI 34 reconfiguration of the diagnostic port output: low 35 period of time t2 = F (R1, R2, C2) reconfiguration of the entered diagnostic port

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 37 control of passage of the power stage from the on position to the off position by the control line 6.

38 condition of passage of the power stage from the off position to the on position by the control line 6.

Claims (15)

 1) A method of controlling the operation of an electrical power stage (4) and detecting a short circuit of the power stage (4), with respect to the supply voltage (28), by in relation to the ground (30) and to a cable break (29), the electrical consumer and a switching element (4) associated therewith are controlled by a microcomputer (1) (pC) by a control line (6), characterized in that the electrical power stage (4) is connected to a digital diagnostic port (12) of the microcomputer (1), and the fault states (28, 29, 30) are recognized by reading the states of the diagnostic port (22,23) at the output of the electrical switching element and reading the state of charge of a memory element (7).  2) Method according to claim 1, characterized in that the detection of the fault state (28) "short circuit to the supply voltage" when the electrical switching element (4) is in the connected state (20) is by reading the high level state (23) of the diagnostic port.  3) Method according to claim 2, characterized in that the electrical consumer (15) is connected in its branch state (20) by the switching element (4) during reading.  4) Method according to claim 1, characterized in that the detection of the state of failure (30) "short circuit to ground" is in the state of cutoff (21) of the electrical switching element ( 4) by reading a "low level" state (22) from the diagnostic port.  5) Method according to claim 4, characterized in that <Desc / Clms Page number 14>  the electrical consumer (15) is connected by the switching element (4) during playback in its off state (21).  6) Method according to claim 1, characterized in that the detection of the state of failure (29) "cable cut" is by a combined operation of the evolution of the state level (22,23) of the port of diagnosis and their evolution over time.  7) Method according to claim 6, characterized in that during the first reading of the state "low level" (22) of the diagnostic port, in the state of cutoff (21) of the electrical consumer (15) and after a waiting time (26) Tl = 3 x R2 x C1, the "high level" state (23) of the diagnostic port is read again and the fault condition (29) "cable cut" is detected .  8) Method according to claim 1, characterized in that for detecting the state of failure (29) "cable cut" for an intact state (27) of the system, the capacitor (7) C1 is loaded according to the state " high level "(23) of the port of diagnosis and read the port of the diagnosis (12).  9) Method according to claim 8, characterized in that after the first reconfiguration (34) of the digital diagnostic port (12) after a time t2 = f (RI, R2, Cl) is made a second reconfiguration (36) of the port digital diagnostic device (12) on "input" and when reading a "low level" state (22) of the diagnostic port the fault state (29) "cable cut" is recognized, and during the reading of the "high level" status (23) of the diagnostic port it is concluded that a system is operating correctly (27). 10) Method according to claim 1, characterized in that <Desc / Clms Page number 15>  for the detection of the fault condition (29) "cable cut" is made a re-configuration (31) of the digital diagnostic port (12) of the microcomputer (1) on "output: high". 11) Method according to claim 10, characterized in that

 after a waiting time T1> 3 x RI x C1, the digital diagnostic port (12) is re-configured (32) to "input" and the state (22, 23) of the digital port of the capacitor (7). 12) Method according to claim 11, characterized in that when reading the state "high level" (23) of the diagnostic port is concluded in the state of fault (29) "cable cut". 13) Method according to claim 11, characterized in that

 when reading the "low level" state (22) of the digital port, it is concluded that the fault state (30) is "short circuit to earth". 14) Circuit for carrying out the method according to claims 1 to 9, characterized in that it comprises a microcomputer (1) controlling by a digital port (3) a switching element (4) which switches the consumer an electric capacitor (15), a capacitor (7) CI and a protection resistor (9) RI and a lifting resistor (10) R2, and the electrical consumer (13) is connected to a digital diagnostic port (12) the microcomputer (1). 15) Circuit for carrying out the method according to claims 1 to 5 and 10 to 13, characterized in that it comprises a microcomputer (1) controlling by a digital port (3) a switching element (4) switching the consumer <Desc / Clms Page number 16>  an electrical capacitor (15), a capacitor (7) CI and a protection resistor (9) RI, and the electrical consumer is connected via a digital diagnostic port (12) of the microcomputer (11).