Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
  • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
  • H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
  • H02H9/047—Free-wheeling circuits
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H11/00—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result
  • H02H11/002—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of inverted polarity or connection; with switching for obtaining correct connection
  • H02H11/003—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of inverted polarity or connection; with switching for obtaining correct connection using a field effect transistor as protecting element in one of the supply lines
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S388/00—Electricity: motor control systems
  • Y10S388/90—Specific system operational feature
  • Y10S388/903—Protective, e.g. voltage or current limit

Definitions

• the present invention relates to a control circuit for a direct current electric motor. It also relates to its application to a wiping system for vehicle windows.
• the other terminal of the DC motor is connected to the chassis or to the negative terminal of the DC power source.
• such a control circuit is generally supplemented by a second MOS transistor which is connected between the ground connected to the chassis on the one hand and the terminal of the electric motor which is connected to the aforementioned MOS transistor.
• This second MOS transistor is generally dimensioned to receive little current and it is activated, that is to say made conductive, only during the braking phase of the DC motor. In the rest of the operating time, the second MOS transistor is set to the high impedance state and sees no current, other than a leakage current, crossing its drain-source path.
• Such a control circuit must have high reliability.
• a reversal of the polarities applied to the electric motor control circuit can lead to the destruction of the circuit since, in order to lower the cost of such a circuit control, the second transistor activated during braking is a low power transistor.
• a failure of the protection device prevents the operation of the protected device even if the applied polarities are suitable.
• the present invention provides a remedy to these drawbacks of the state of the art in that it relates to a control circuit for a direct current electric motor, on a polarized direct voltage source, of the type comprising at least one controllable switch. connected to the hot spot of the electric motor and a braking circuit intended to exert a braking short circuit of the DC electric motor.
• the invention is characterized in that the control circuit comprises a low power component connected in series in the braking circuit which has a high impedance in the event of reverse polarity and a low impedance in the event of correct polarity.
• the invention then relates to a wiping system for vehicle windows which incorporates such a control circuit.
• FIG. 9 illustrates the diagram of a second embodiment of the present invention.
• FIG. 1 there is shown a conventional embodiment of a control circuit of a direct current electric motor particularly intended for application to a system for wiping vehicle windows.
• the control circuit essentially comprises two first M1 and a second M2 MOS FET type transistors which are connected in series between a positive supply terminal 1 and the electrical ground generally constituted by the chassis of the vehicle.
• the positive terminal of the battery or on-board network is connected to terminal 1 of the control circuit when the latter is in action.
• the two MOS transistors are of the same type.
• the source of the first upper transistor M1 is connected to the drain of the second lower transistor M2.
• the drain of the first upper transistor M1 is connected directly to terminal 1 of the control circuit while the common point between the first M1 and second M2 transistors is connected to a first supply terminal of the DC motor M.
• the other terminal of the DC motor M is connected to the ground or chassis of the vehicle.
• Each gate 2 and 3 of the transistors M1 and M2 is in turn connected to a control circuit, not shown, which makes it possible to decode the commands originating from the driving position of the vehicle.
• an output terminal of the control circuit is connected to the gate terminal 2 of the upper transistor M1 and is active when the motor M is to be started.
• MOS FET type transistors like the M1 and M2 transistors have an intrinsic diode formed between the drain and source connections. This anti-parallel diode of a MOS FET transistor is created during of the manufacturing of the transistor. All common MOS FET transistors have a parasitic diode and those which do not have one are produced according to a specific production process and are too expensive in most applications. In Figure 2, there is shown the detail of this arrangement.
• a MOS FET transistor 4 is shown with its gate electrode 5, its drain electrode 6 and its source electrode 7.
• the transistor shown is of the N channel MOS type 7.
• An anti-parallel diode 8 is formed during the manufacture of the transistor 4 so that its anode is connected to the source of the transistor 4 and so that its cathode is connected to the drain of transistor 4.
• this diode 8 operates in a parasitic manner. In particular, it tends to pass electrical energy in the source-drain path backwards from the normal circulation of charge carriers in the absence of control on the grid.
• the MOS FET transistor can easily be destroyed if the reverse current exceeds a certain threshold.
• the anti-parallel diodes D1 and D2 of the transistors M1 and M2 are conductive and are crossed by a strong current which is not limited by any load, and which is therefore destructive.
• the transistor M2 which is destroyed because it has a lower power sizing than the transistor M1, but one can also have a destruction of the transistor M1 if the transistor M2 has a short circuit during its destruction.
• the transistor M2 sees on its drain-source path a current opposite to the nominal direction of circulation of the charge carriers and is irretrievably destroyed if it is dimensioned, as is usual, only to effect the braking of the of the motor M.
• FIG. 4 a first means of protection against the inversion of the polarities is shown, taken from the aforementioned state of the art.
• the positive terminal of a polarized power source is connected to the anode of a protective diode 12 whose cathode is connected to the input terminal or hot spot which is intended to be connected to the positive terminal of supply of an electronic assembly to be protected 13.
• the other polarization terminal of the electronic assembly 13 is connected to ground 14.
• the protection diode 12 against reverse polarity introduces a voltage drop which can be detrimental to the proper functioning and, if it is destroyed, interrupts the supply of the electronic assembly.
• the positive power supply terminal 1 1 is transmitted to the positive input terminal of the electronic assembly 13 via the drain-source path of an N-channel MOS FET transistor which has a parasitic anti-parallel diode 16.
• the gate of the MOS FET transistor 17 is connected to a control signal 15, produced by the electronic assembly to be protected 13.
• Such a device makes it possible to reduce the voltage drop in normal operation by controlling the gate of transistor 17.
• the electronic assembly 13 loses its power supply, which can be damaging. Furthermore, the electronic assembly 13 to be protected must also be modified to generate a correct signal 15 for turning on the MOS FET transistor 17.
• FIG 6 there is shown another mode of protection against reverse polarity in the prior art.
• a protective diode 18 is connected between the cold spot of the electronic assembly 13 to be protected and the electrical ground of the device.
• This type of assembly suffers from two drawbacks caused first by the voltage drop introduced by the diode 18 in normal operation which places the cold point of the power supply of the electronic assembly 13 at a few volts above the electrical ground of the mounting.
• a MOS FET transistor 21 is placed by its drain-source path in reverse between the cold point of the electronic power supply 13 and the ground 14.
• the anti-parallel diode 20 of the MOS FET transistor 19 plays the same role as the diode 18 of the embodiment of FIG. 6. However, the voltage drop can be reduced by applying conduction in normal operation by the gate electrode 22 of the MOS FET transistor 21.
• FIG. 8 To remedy the aforementioned drawbacks of the state of the art and bring new advantages, the invention has been shown in a first embodiment in FIG. 8 and in a second embodiment in FIG. 9.
• transistors M1 and M2 are substantially identical to the transistors M1 and M2 of the assembly of FIGS. 1 and 3.
• the control circuit of the invention comprises a low power component M3 connected in series in the braking circuit.
• This component has a high impedance in the event of reverse polarity of the power supply to the control circuit and therefore of the motor and a low impedance in the event of correct polarity.
• the component M3 is a dipole, the low impedance state of which can be controlled by at least one electrode 26 connected to an armature braking control signal.
• the gate electrode 23 of the transistor M1 of the high power MOS FET type is directly controlled and placed in the active state when the motor M is to be started.
• the second M2 MOS FET transistor of reduced power is connected between the common connection point between the electric motor and the source of the transistor M1, and is, by its source, connected to an electrical dipole for protection against reverse polarity which has a low impedance.
• the control circuit is responsible for not activating the transistors M1 and M2 at the same time.
• the braking circuit when the braking circuit is activated by a pulse on the gate electrode 24 of the second transistor M2, the low power component 25 passes or remains in the state of low impedance and the braking current flows to ground through dipole 25.
• the control circuit of a DC electric motor is such that the low power component M3 is constituted by the antiparallel diode of a MOS FET transistor the source of which is connected on the one hand to the source of the transistor M2 and to the anode of its anti-parallel diode and the drain of which is connected to the cathode of the above-mentioned diode and to ground.
• the gate electrode of the MOS FET transistor 25 is directly connected to the control terminal of the braking circuit 24 so that when the polarity is suitable and the circuit is activated, the transistor 25 is crossed by the current from the transistor M2 .
• the dipole 25 passes or remains in the low impedance state.
• the transistor M3 has a high impedance because, in this case, its anti-parallel diode cannot be conductive, its cathode being connected to the positive terminal of the power source and the transistor M3 cannot be activated because the control circuit is reverse biased and is not functional.
• control circuit of an electric current motor continuous is such that the low power component M3 consists of a diode connected by its cathode to the normal ground of the power supply and the anode of which is connected to the source of the braking transistor M2.
• the gate of transistor M3 is not necessarily connected to the gate of transistor M2.
• the transistor M3 can be activated (on its gate) by a permanent direct voltage from the control circuit such as the regulated voltage of the control circuit for example, and therefore the transistor M3 is permanently on as long as the supply polarity is properly applied. It is the transistor M2 which authorizes the passage of the current in the branch M2-M3.
• This type of configuration has the advantage over the type of embodiment of the first embodiment shown in FIG. 8 of not preventing the use of the anti-parallel diode of the transistor M2 as a freewheeling diode when the load is inductive, which is the case with an electric motor as a charge.
• the electrode of gate of transistor 25 is not necessarily connected to terminal 24.
• Transistor 25 can be activated by an activation signal connected to its gate by a permanent DC voltage from the control circuit.
• the transistor 25 is crossed by the current from the transistor M2.
• the anti-parallel diode of transistor M3 blocks the flow of current, which prevents the circuit from operating.
• transistors M2 and M3 are connected to the same external control terminal intended to be connected to a control circuit (not shown) of the control circuit of the invention, it is very easy to mount the two transistors M2 and M3 on the same support, for example, braking circuit.
• a wiping system according to the invention can incorporate a half-bridge of the type of that of FIG. 8 which is connected directly to an electric wiping motor.
• a control circuit is added to connect the gate electrodes of transistors M2 and M3 of the braking circuit to a braking control terminal and the gate electrode of transistor M1 is connected to a motor start control terminal electric which can be a pulse control, or a periodic control voltage to control the electric motor in voltage regulation with pulses of width controlled by the control circuit according to setpoints (PWM mode).
• PWM mode setpoints
• the gates of the transistors M2 and M3 are not necessarily connected, but are connected to suitable control terminals of their control circuit.
• the control circuit produces a pulse command or a PWM command with width modulation using the diagram in FIG. 8
• a thyristor can be used in the case of a pulse command and replaces the transistors M2 and M3 .
• the absence of a freewheeling diode has a drawback.

Landscapes

• Control Of Direct Current Motors (AREA)
• Stopping Of Electric Motors (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=32799579

Family Applications (1)

Country Status (7)

Families Citing this family (9)

Family Cites Families (13)

• 2003
  • 2003-02-21 FR FR0302314A patent/FR2851698B1/fr not_active Expired - Fee Related
• 2004
  • 2004-02-12 EP EP04710343A patent/EP1595321A2/fr not_active Withdrawn
  • 2004-02-12 CN CNA2004800046989A patent/CN1751424A/zh active Pending
  • 2004-02-12 WO PCT/EP2004/001287 patent/WO2004075390A2/fr not_active Ceased
  • 2004-02-12 JP JP2006501813A patent/JP2006518980A/ja active Pending
  • 2004-02-12 BR BR0407023-2A patent/BRPI0407023A/pt not_active IP Right Cessation
  • 2004-02-12 US US10/545,698 patent/US7268508B2/en not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events