FR2673307A1 - STATIC ELECTRONIC TYPE LIGHT WARNING DEVICE, IN PARTICULAR FOR THE CONTROL OF DIRECTION INDICATORS OF A MOTOR VEHICLE. - Google Patents

Abstract

This device comprises an oscillator (10) capable of providing at output a square wave control signal (A) and at least one static electronic power switch (30), preferably a TEC type transistor, which is interposed between a first terminal (2) intended to be connected to a supply voltage source and a second terminal (12) intended to be connected to the load (L) and which has a control input (1) controlled by the output of the oscillator (10). According to the invention, it further comprises first and second detector means (R6, R7, R5), able to detect respectively the intensity of the current flowing in operation in the electronic switch (30), and therefore of the current flowing in the load (L), and the voltage drop on the electronic switch (30), and a control circuit (20) which is interposed between the oscillator (10) and the electronic switch (30) and is coupled to these first and second detector means and which is capable of causing the blocking of the electronic switch (30) when the current flowing to the load (L) crosses a predetermined threshold and when the voltage at the terminals of this switch (30) crosses a predetermined value.

Description

A 2673307

  The present invention relates to a light warning device of the type

  electronic, in particular for controlling the direction indicators of a vehicle

car cule.

  More specifically, the subject of the invention is an electronic type light warning device, comprising an oscillator capable of providing a square wave control signal as an output and at least one static electronic power switch, preferably a transistor. of the field effect transistor type, TEC, which is interposed between a first terminal intended to be connected to a supply voltage source and a second terminal intended to be connected to

  1 o the load and which has a command input controlled by the output of the oscillator-

  reader. For the control of direction indicators / emergency stop, we use

  currently light warning devices of the electronic or electro- type

  mechanical, in all cases including an electromechanical switch for

  power, typically a relay, for piloting the lamps.

  Such devices generally work satisfactorily, but nevertheless have certain drawbacks, essentially linked to the presence of

  electromechanical type switches with movable switching contacts.

  Thus, these light warning devices generally have a useful life limited by the wear of the contacts, and unsatisfactory performance in the presence of vibrations or under conditions of high temperature. They are also generally poorly resistant in the event of accidental overloads and in

  operating in hostile atmospheres.

  More recently, it has been envisaged to produce light warning devices of the completely static electronic type, and therefore comprising (at least) a static electronic power switch. Such devices also have drawbacks. First, the voltage drop on the electronic switch output leads to a significant dissipation of power which is problematic in view of the very small overall dimensions which are usually imposed on light warning devices The light warning devices of static electronic type are also poorly resistant to overcurrents and there are the possibility that the electronic power switch may be damaged by an overload, even for only a few thousandths of a second In fact, in electrical installations used on board motor vehicles, protection against overcurrents t generally entrusted to fusible elements which have relatively long response times, of the order of a few seconds On the other hand, an overload or short-circuit state can occur quite easily in

such facilities.

  Static electronic flashing warning devices produced so far are also quite sensitive to overvoltages due to

  switching of inductive loads (e.g. the fan motor of the radiator)

  the wiper motor, etc.), which can reach peak values of, for example, 150 V or more, or when the on-board battery is disconnected opposite

  of the electrical installation, under the effect of which it can occur in the installation

  lation a voltage spike of notable duration and energy.

  The purpose of the present invention is to provide a light warning device.

  lo ous static electronic type which is free from the drawbacks indicated above

above.

  In accordance with the invention, this object is achieved by means of a device

  luminous weaver of electronic type, as indicated above, whose character

  main ristic lies in the fact that it comprises first and second detector means, capable of respectively recording the intensity of the current flowing in operation in the electronic switch, and therefore of the current flowing to the load, and the voltage drop on the electronic switch, and a control circuit which is interposed between the oscillator and the electronic switch and is coupled to these first and second detector means and which is capable of causing the blocking of the electronic switch when, in operation, the current flowing to the load crosses a predetermined threshold and when the voltage

  on this switch crosses a preset value.

  In a given embodiment, the control circuit comprises a transistor whose base-emitter junction is connected practically in parallel to the electronic switch and whose collector-emitter path is connected between the output of the oscillator and the ground, so that , when the electronic switch conducts the current, this transistor is liable to become conductive and block the electronic switch when the voltage on this electronic switch exceeds the preset value for a preset time and / or when the current flowing to the load crosses said threshold for a predetermined period of time and / or when the temperature of the electronic switch exceeds

a prefixed value.

  Other characteristics and advantages of the warning light device

  according to the invention will emerge from the detailed description which follows, carried out in

  with regard to the appended drawings provided solely by way of nonlimiting example and in which: FIG. 1 is a detailed electrical diagram of a light warning device, of static electronic type, in accordance with the invention and FIG. 2 is a diagram, partially a block diagram, of a variant of

  realization of the light warning device according to the invention.

  Referring to FIG. 1, a light warning device, of static electronic type, in accordance with the invention comprises an oscillator, generally designated by the reference 10, which is capable of supplying an output signal

piloting A with square wave.

  The output of oscillator 10 is connected to the input of a control circuit designated as a whole by the reference 20 The output of this circuit is connected to

  the gate electrode of a solid state electronic switch which, in reality

  sation presented by way of example in Figure 1, is constituted by a device to

  detection field effect transistor TEC 30.

  The oscillator 10 has a supply terminal 11 intended to be connected to a source of direct supply voltage, for example to the positive pole of the on-board battery of the motor vehicle. The control circuit 20 and the drain of the electronic switch 30 are also connected to this terminal 11 The source of this switch is connected to an output terminal 12 It is, during use, between this terminal and the earth that the load of the warning device is connected

  luminous, typically constituted by one or more lamps indicating

  motor vehicle steering / emergency stop switches One of these lamps is shown in FIGS. 1 and 2 and is designated by the reference mark L. In a manner known per se, the oscillator 10 comprises an integrated circuit IC (for example a device UAA 1041 produced and marketed by Motorola) to which are connected a resistor R 1 and a capacitor Ci which define the frequency of the signal A A calibrated resistor Rs is also connected to the integrated circuit IC, this calibrated resistor being traversed , in operation, by the current which, passing through the control circuit 20 and the electronic switch 30, supplies the load L. Two other resistors R 2 and R 3 are connected between inputs of the circuit

  integrated IC and respectively earth or output terminal 12.

  In a manner known per se, the oscillator 10 comes into operation under the effect of the connection of a load on the output terminal 12 of the warning device

  luminous Via the resistor Rs, the oscillator also detects the importance

  tance of this charge and produces a failure signaling frequency when the

  load is found to be less than a predetermined value.

  The control circuit 20 comprises a voltage booster, designated as a whole by the reference 21, which comprises a capacitor C 2 having an armature connected to the output of the oscillator 10 and its other armature connected to the cathode of a diode D 2, the anode of which is connected to the power supply terminal 11 via the resistor Rs of the oscillator 10 The output of the voltage booster 21 is connected to the emitter of a bipolar transistor T 1 , of the pnp type, via two resistors R 10 and R 8 The transistor TI has its collector connected to ground via a resistor R 4 and its base connected to the output terminal 12 by the intermediate of two resistors R 9 and R 5 A capacitor C 3 is connected between the base and the transmitter of T 1 A diode D 3 has its anode connected to the transmitter of Tl and its cathode connected to the supply terminal 2 of the circuit

command 20.

  A diode D 4 has its anode connected to the transmitter of T1 and its cathode connected to the output of the oscillator 10. Such a diode blocks the control circuit 20 when

  waveform A is at a "low" level.

  A Zener diode Z 1 has its anode connected to the collector of Dl and its cathode connected to that of D 3 In operation, this Zener diode serves as a voltage stabilizer and protects the control circuit 20 in the event of possible reversal of the

  supply voltage polarity.

  The control circuit 20 comprises a second bipolar transistor T 2, of the npn type, the collector of which is connected to the gate of the electronic switch 30 and to the output of the voltage booster 21 via the resistor R 10 La base of T 2 is connected to the mirror terminal of switch 30 via a

  resistor R 7 The emitter of this transistor is connected to the junction between the resistors

tances Rg and R 5.

  The main terminals of the control circuit 20 have been assigned the marks 1 to 6: terminal 1 represents the input of the square wave signal A emitted by the oscillator 10, terminal 2 is the power input, the terminal 3 is connected to the gate of the switch 30 and represents the output of the control circuit 20, the terminals 4

  and 5 represent detection inputs and are respectively connected to the resistors

  tances R 7 and R 5 and, finally, terminal 6 is connected to ground via the

resistance R 4.

  In the embodiment shown by way of example in FIG. 1, another resis-

  tance R 6 is arranged between the mirror terminal of switch 30 and the output terminal

  12 of the warning light device.

  In operation, when a load L is coupled to the output of the light-signaling device, the oscillator comes into operation and outputs the square wave signal A which, raised in amplitude by means of circuit 21, is applied to the gate of the electronic switch 30 This switch is alternately made conductive and blocked and, in the phases in which it is conductive, the current which passes through its drain-source path

  flows to the load via the output terminal 12.

  In normal operation, the transistor T 1 is blocked.

  If, in operation, the load L is short-circuited, the potential of terminal 5 of the control circuit decreases (naturally in the phases in which the electronic switch 30 is conductive) The potential difference between terminals 2 and 5 of the control circuit increases correspondingly With a certain delay time, coming from the time constant defined by the value of the resistance Rg and the capacitance of C 3, the difference of

  potential between the emitter and the base of Tl also increases correspondingly

  laying until T 1 becomes conductive, thus opening a path of

  current between the output of the voltage booster 21 and the ground The pilo signal

  tage is thus diverted from the grid of the electronic switch 30, which is thus blocked In addition, if the increment of the current passing through the output terminal 12 towards the load persists for a time less than the delay time defined by Rg and C 3, the transistor Tl remains blocked and it therefore does not intervene for

  block the electronic switch 30.

  Advantageously, the delay time introduced by R 9 and C 3 is correlated with the typical heating time of lamps L As is known, filament lamps cold absorb a current much greater than the current absorbed when hot Such greater absorption occurs, however, for an extremely short time from ignition The time constant introduced by Rg and C 3 therefore prevents the transistor T 1 from being blocked in the phase of ignition under the effect of greater absorption than lamps

normally present cold.

  If, in operation, the voltage between the drain and the source of the electronic switch 30 increases, the potential difference between terminals 2 and 5 of the

  control circuit increases correspondingly If the drain-

  source of this switch exceeds a preset value for a predefined time-

  finished, once again linked to the time constant defined by R 9 and C 3, the tran-

  sistor Tl in this case also goes from the blocked state to the conducting state, which

  deflects the control signal from the grid of the electronic switch 30.

  Since the emitter-base junction of T 1 is connected practically in parallel

  at the drain-source path of the electronic switch 30, the transistor Tl is suscep-

  tible of becoming conductive also in the case in which, during operation, the temperature of this electronic switch 30 increases excessively,

  by causing a corresponding variation in the transmitter / base voltage of T1.

  In operation, the voltage which is located at the terminals of the resistor R 6 is found to be indicative of the current passing through the load L In fact, as is known, a fraction of the total current passing through the detection TEC passes through its mirror terminal and, through R 6, reaches the load L The voltage drop across the terminals of R 6 is read by the control circuit 20 via the resistors R 5 and R 7 Thus, if in operation , the voltage between terminals 4 and 5 of the control circuit 20 begins to increase, the transistor T 2, by becoming more conductive, reduces the pilot current which passes to the gate of the commu-

  electronic timer 30, thereby achieving an effective action of limiting

  tation of the current sent to the load L.

  The warning light device, of static electronic type, described below

  above has many advantages.

  First, there is a small voltage drop on the electronic switch in the conduction phases. Power dissipation is therefore very limited and the device as a whole can be produced with extremely small dimensions, especially with regard to the components

  possibly giving off heat.

  The maximum current sent to the lamps is effectively limited, with a timed type control. This allows, as we have seen, to limit the initial "current shock" which exists in normal operation with filament lamps. that the useful life of such lamps is

increased accordingly.

  The device is blocked either in the event of an output overcurrent or in the event of an excessive voltage drop across the terminals of the electronic power switch. The device is also protected against reverse polarity of the

  supply voltage and in case of excessive temperature of the electric switch

tronic.

  As a whole, the light warning device creates disturbances

  radio at extremely reduced levels, while the pheno-

  typical scintillation leads between the contacts of electromechanical devices

  conventional light warning devices.

  Consequently, the light warning device as a whole is protected from all possible functional disadvantages and it has

  a useful life greater than that of conventional devices.

  Since the light warning device described above is completely static, it can be coated with insulating materials, such as

  resins and the like and, as a result, it is made unassailable by environmental agents.

  exterior and insensitive to the effects of mechanical stress.

  FIG. 2 represents an alternative embodiment in which, moreover, the oscillator 10 and the control circuit 20 have the same structure as that

  described with regard to the exemplary embodiment of FIG. 1.

  In this variant according to FIG. 2, instead of a device,

  sitive TEC detection, a TEC-MOS transistor, designated by the reference 300, the gate of which is connected to the output terminal 3 of the control circuit 20 by means of a resistor R 6, while its drain is connected to terminal 4 of the control circuit via a resistor R 7 and that its source is connected to terminal 5 of this control circuit via the resistor R 5 A Zener diode Z 2 is connected between the grid and the source of the TEC-MOS 300 in order to limit the voltage applied to the grid of this device. In this variant according to FIG. 2, unlike the solution represented in FIG. 1, the voltage between the drain and the source of the electronic switching device 300 and the intensity of the current sent to the load are recorded jointly by means of the reading of the existing voltage-between the terminals 4 and 5 of the control circuit Indeed, the voltage between these terminals is linked to tension existed nt between the drain and the source of the switch 300, which voltage is, in the conduction phases of this

  switch, proportional to the current flowing through this device.

  For the rest, the operating conditions of the version compliant with the

  Figure 2 are quite similar to those of the version according to Figure 1.

  The warning light device according to the invention can be produced either in the version in which the indicators on the right and left side of the motor vehicle are jointly controlled, or in the version in which, by means of the use of a plus large number of switches

  power, the right and left indicators are controlled separately.

  Of course, the principle of the invention still being valid, the forms of implementation and the particular features of implementation may be largely modified with regard to what has been described and shown simply

  non-limiting example, without thereby departing from the scope of the present invention.

Claims (10)

  1 electronic type light warning device, in particular for controlling the direction indicators (L) of a motor vehicle, comprising an oscillator (10) capable of outputting a square wave piloting signal (A) and at least one static electronic power switch (30; 300), preferably a TEC type transistor, which is interposed between a first terminal (2) intended to be connected to a supply voltage source and a second terminal (12) intended to be connected to the load (L) and which has a control input (1) controlled by the output of the oscillator (10), characterized in that it further comprises first and second detector means (R 6, R 7, R 5), capable of raising   respectively the intensity of the current flowing during operation in the commu-   electronic sensor (30; 300), and therefore of the current passing through the load (L), and the voltage drop on the electronic switch (30; 300), and a circuit   control (20) which is interposed between the oscillator (10) and the electro-switch   (30, 300) and is coupled to these first and second detector means and which is capable of causing the blocking of the electronic switch (30; 300) when, in   operation, the current passing to the load (L) crosses a predeter threshold-   mined and when the voltage across this switch (30; 300) crosses a preset value.   2 Device according to claim 1, characterized in that the control circuit (L) comprises a first transistor (Ti) whose base-emitter junction is connected practically in parallel to the electronic switch (30, 300) and whose collector path- transmitter is connected between the output of the oscillator (10) and ground, so that when the electronic switch (30, 300) conducts current, this transistor (Tl) is likely to become conductive and block the   electronic switch (30; 300) when the voltage on this electronic switch   pic (30; 300) exceeds the prefixed value for a preset time and / or when the current flowing to the load (L) crosses said threshold for a predetermined period of time and / or when the temperature of the electronic switch   (30; 300) crosses a prefixed value.   3 Device according to claim 2, characterized in that the first transistor (Tl) has its emitter connected to the supply terminal (2) via a diode (D 3).   4 Device according to claim 2, characterized in that the first transistor (Tl) are associated with delay means (R 9, C 3) capable of delaying its   passage from the blocked state to the conducting state.   Device according to claim 4, characterized in that the delay means comprise a capacitor (C 3) mounted in parallel with respect to the   emitter-base junction of the first transistor (Tl).   6 Device according to any one of claims 2 to 5, characterized   in that the control circuit (20) comprises means (T 2) for stabilization   of the current flowing in operation towards the load (L).   7 Device according to claim 6, characterized in that the current stabilization means comprise a second transistor (T 2) whose path   collector-emitter is connected between the control switch control input   tronic (30, 300) and the second terminal (12), while its base is connected to   second-means detectors (R 7, R 6).   8 Device according to any one of claims 2 to 7, characterized   in that the control circuit (20) has a first Zener diode (Zj), serving as a stabilizer of the supply voltage and protection against the reversal of polarity of this supply voltage, and a blocking diode (D 4)   of the control circuit (20) when the signal from the oscillator is at a low level.   9 Device according to claim 8, characterized in that a resistor (R 4) is interposed between the collector of the first transistor (Tl) and the ground and in that the Zener diode (Zl) is connected between the supply terminal (2) and the   collector of the first transistor (Tl).   Device according to any one of claims 1 to 9, characterized   in that the electronic switch is a device of the TEC detection type (30), the source and the mirror terminal of which are connected to the second terminal (12) which is intended to be connected to the load (L), a resistor (R 6) being interposed between the   mirror terminal of the switch (30) and the second terminal (12).   11- Device according to any one of claims 1 to 9, characterized   in that the electronic switch is a TEC-MOS device (300).   12 Device according to claims 7 and 11, characterized in that the second detector means comprise a resistor (R 7) connected between the   drain of the TEC-MOS device (300) and the base of the second transistor (T 2).   13 Device according to claim 11 or 12, characterized in that a   second Zener diode (Z 2) is placed between the grid and the source of the TEC- device MOS (300).