DE102015105434A1 - Drive device for an electric motor - Google Patents

Abstract

An electric motor drive apparatus (100), comprising: - electronic control means (20) for driving an output stage (40); and - a field-effect transistor (10) arranged in an electrical supply circuit of the drive device (100); - In which by means of the control device (20) in response to a drive state of the output stage (40) is adjustable in height electrical control voltage (USt) for a gate of the field effect transistor (10) can be provided; - Wherein the field effect transistor (10) with a first defined control voltage (USt) is switched through when the output stage (40) is driven; and - wherein the field effect transistor (10) with a second defined control voltage (USt), which is lower than the first defined control voltage (USt) is switched through when the output stage (40) is not driven.

Description

The invention relates to a drive device for an electric motor. The invention further relates to a method for driving an electric motor.

State of the art

Known electronic controllers use "reverse polarity protection" n-channel MOSFETs for an assembly function. A corresponding control signal must have at least one voltage potential of MOSFET source plus plateau voltage (typically 7V). This potential is generated by an active circuit, for example in the form of a charge pump, a boost converter, etc. Today's charge pumps usually generate about 12V control voltage at about 13 V supply voltage. The disadvantage can occur due to the permanent provision of reverse polarity protection increased power consumption of a control electronics.

Disclosure of the invention

It is therefore an object of the present invention to provide an improved drive apparatus for an electric motor.

• – eine elektronische Steuerungseinrichtung zum Ansteuern einer Endstufe; und
• – einen in einem elektrischen Versorgungskreis der Ansteuervorrichtung angeordneten Feldeffekttransistor;
• – wobei mittels der Steuerungseinrichtung in Abhängigkeit von einem Ansteuerzustand der Endstufe eine in der Höhe verstellbare elektrische Steuerspannung für ein Gate des Feldeffekttransistors bereitstellbar ist;
• – wobei der Feldeffekttransistor mit einer ersten definierten Steuerspannung durchschaltbar ist, wenn die Endstufe angesteuert ist; und
• – wobei der Feldeffekttransistor mit einer zweiten definierten Steuerspannung, die niedriger ist als die erste definierte Steuerspannung durchschaltbar ist, wenn die Endstufe nicht angesteuert ist.

According to a first aspect, the object is achieved with a drive device for an electric motor, comprising:

• - An electronic control device for driving an output stage; and
• A field effect transistor arranged in an electrical supply circuit of the drive device;
• - In which by means of the control device in response to a drive state of the output stage, a height-adjustable electrical control voltage for a gate of the field effect transistor is provided;
• - Wherein the field effect transistor can be switched with a first defined control voltage when the output stage is driven; and
• - Wherein the field effect transistor with a second defined control voltage, which is lower than the first defined control voltage is switched, if the output stage is not activated.

• – Erzeugen einer elektrischen Steuerspannung für den Feldeffekttransistor mittels der Steuerungseinrichtung, wobei mittels der Steuerungseinrichtung eine in der Höhe verstellbare elektrische Steuerspannung für ein Gate des Feldeffekttransistors bereitgestellt wird;
• – wobei der Feldeffekttransistor mit einer ersten definierten elektrischen Steuerspannung durchgeschaltet wird, wenn die Endstufe angesteuert wird; und
• – wobei der Feldeffekttransistor mit einer zweiten definierten elektrischen Steuerspannung, die niedriger ist als die erste definierte Steuerspannung, durchgeschaltet wird, wenn die Endstufe nicht angesteuert wird.

According to a second aspect, the object is achieved with a method for driving an electric motor by means of said drive device, comprising the steps:

• - Generating an electrical control voltage for the field effect transistor by means of the control device, wherein means of the control means an adjustable in height electrical control voltage for a gate of the field effect transistor is provided;
• - Wherein the field effect transistor is turned on with a first defined electrical control voltage when the output stage is driven; and
• - Wherein the field effect transistor with a second defined electrical control voltage, which is lower than the first defined control voltage, is turned on when the output stage is not driven.

Advantageously, can be achieved in this way that in a normal operation of the drive device of the field effect transistor remains permanently connected, wherein in the event that the output stage is not driven, the control voltage of the field effect transistor is defined set such that the field effect transistor is turned on with a minimum control voltage.

For the drive device, which may be arranged in a control unit of a motor vehicle, a power consumption can be reduced in this way, because a power consumption for generating the control voltage is minimized. As a result, a power module of the control unit can advantageously be made less powerful and, as a result, a CO ₂ emission of the motor vehicle can be reduced.

Advantageous developments of the drive device and the method are the subject of dependent claims.

An advantageous development of the drive device is characterized in that, in the event that the output stage is not driven, the control voltage is lowered defined by means of the control device, wherein a plateau value of the control voltage remains defined exceeded. For example, the electrical control voltage can be adjusted in this way from a level of about 12V above a level of the supply voltage to a level of about 7V above the level of the supply voltage. This is enough to just keep the field effect transistor turned on. Connected thereto can be realized for the drive device, a significant power savings.

A further advantageous development of the drive device is characterized in that the control voltage can be configured by means of the control device. In this way, for example, with values of a data sheet, the electrical control voltage can be adapted to a MOSFET type used for the field effect transistor.

A further advantageous development of the drive device is characterized in that the control voltage of the field effect transistor is controllable by means of the control device. This can be realized for example by means of two additional measuring inputs of the control device, at which an electrical voltage drop across the field effect transistor is determined. Thereby, a control of the control voltage can be achieved, whereby, for example, a balancing of temperature effects can be achieved.

A further advantageous development of the drive device is characterized in that a charge pump arranged within the control device can be used to generate the control voltage, wherein an electrical auxiliary voltage can be generated by means of the charge pump, by means of the semiconductor switching elements of the output stage can be controlled. In this way, a circuit part of the control device in the form of the charge pump can be dimensioned lower power, whereby a current consumption of the entire control device can be reduced.

A further advantageous development of the drive device is characterized in that the field effect transistor is of the same type as the semiconductor switching elements of the output stage. In this way, a variety of types of semiconductor devices used can be favorably reduced, whereby a cost-effective production of the drive device is supported.

The invention will be described below with further features and advantages with reference to two figures in detail. In this case, all disclosed features, regardless of their representation in the description and in the figures, as well as regardless of their relationship in the claims the subject of the invention. The figures are intended in particular for an explanation of the principles essential to the invention.

In the figures shows:

1 a block diagram of an embodiment of the drive device according to the invention; and

2 a basic sequence of an embodiment of the method according to the invention.

Description of embodiments

In 1 is an embodiment of a drive device 100 for an electric motor 200 shown.

The drive device 100 is electrically connected between an electrical supply voltage U and ground potential GND. The drive device 100 has an electronic control device 20 (For example, a bridge driver, English Motor Bridge Controller), which is an electrical control voltage U _St for one in the supply circuit of the drive device 100 arranged field effect transistor 10 provides. The field effect transistor 10 may be formed as an n-channel MOSFET having an integrated freewheeling diode (reverse diode), wherein an anode of the freewheeling diode is connected to the potential of the supply voltage U. With non-switched field effect transistor 10 becomes the controller 20 via the freewheeling diode of the field effect transistor 10 supplied with electrical energy. The freewheeling diode of the field effect transistor 10 serves as a polarity reversal protection diode for a power amplifier 40 , which makes it when switched through the field effect transistor 10 It is permanently possible that electric current can flow in both directions in the supply circuit.

Furthermore, by means of the freewheeling diode of the field effect transistor 10 a supply of the control device 20 ensured with electrical energy when the field effect transistor 10 is not switched through.

The control device 20 is provided, the power amplifier 40 with four semiconductor switching elements 41 .. .44 for the electric motor 200 head for. The four semiconductor switch switching elements 41 .. .44 are field effect transistors, preferably of the same type as the field effect transistor 10 , The final stage 40 in the form of an H-bridge with the four semiconductor switching elements 41 .. .44 takes control of an alternating forward / reverse rotation of the electric motor 200 , eg for use in a reversing wiper of a motor vehicle.

The final stage 40 can be controlled such that the connected to the supply voltage U semiconductor switching elements 41 . 42 each remain switched through, whereas the connected to the ground potential GND semiconductor switching elements 43 . 44 controlled clocked, causing a reversing operation of the electric motor 200 can be achieved. Advantageously, it is possible in this way, a mechanical linkage of a windshield wiper device with the electric motor 200 save.

By means of a clock 60 a clock signal is generated, wherein by means of the communication device 30 to the control device 20 a direction signal and a pulse width modulated signal are supplied. This allows externally a direction of rotation or a speed for the electric motor 200 be specified. The communication interface 50 (For example, a single-wire interface, which is preferably designed according to the LIN standard), is functional with the communication device 30 connected to control signals for the control of the electric motor 200 forward. The control device 20 and the communication device 30 may preferably be arranged in a single integrated microelectronic circuit package.

A communication device 30 connected to the control device 20 is functionally interconnected and the control device 20 each have a (not shown) Verpolschutzdiode upstream. Due to the fact that the field effect transistor 10 in the supply circuit before the control device 20 and in front of the communication device 30 is arranged, in the event that the field effect transistor 10 is not turned on, the communication device 30 overcome two electrical diode voltages.

However, this would have a violation of the so-called LIN specification (English: Local Interconnect Network) for a communication interface 50 result, which is why the field effect transistor 10 in a normal operation of the drive device 100 must be permanently switched through. Therefore, the field effect transistor becomes 10 switched by means of the control voltage U _St as soon as a communication of the communication device 30 with an electronic control unit (not shown).

In the communication device 30 is a software 70 deposited. The software 70 has two sections 70a . 70b on, with the section 70a a normal operation of the drive device 100 entails and the section 70b a so-called "low power mode" of the drive device 100 in which the power amp 40 is not driven.

This causes the communication device 30 in normal operation of the drive device 100 to the control device 20 issues a command to generate the control voltage U _St at a first elevated voltage level. In low-power mode 70b is from the communication device 30 to the control device 20 the command is given, the control voltage U _st of the field effect transistor 10 with a second, reduced voltage level.

Once the power amp 40 by means of the control device 20 is driven, the control voltage U _{St is set} to an elevated level, for example, to a voltage value at the source of the field effect transistor 10 plus a defined value of a plateau voltage U _P in the amount of about 12 V. As soon as the power amplifier 40 is no longer driven, causing the electric motor 200 is, the control voltage U _{St is} lowered to a minimum level, for example, to a voltage value at the source of the field effect transistor 10 plus a defined value of the plateau voltage U _P in the amount of about 7 V. The field effect transistor 10 should preferably be operated only briefly in linear operation, preferably always above the plateau voltage U _P.

In this way, when switched field effect transistor 10 a maximum power savings can be achieved because an electrical supply current I _S , for generating the control voltage U _St means of the control device 20 is required is minimized. It is in this way an optimization or reduction of the control voltage U _{St of} the field effect transistor 10 realized so that the field effect transistor 10 is still through.

This is due to a voltage potential at the gate of the field effect transistor 10 Which plus a defined plateau voltage U _P corresponds to the supply voltage U in the amount of about 7 V is reached. By reducing the control voltage U _St to the minimum, the power consumption in the necessary to generate the control voltage U _St circuit parts of the control device 20 reduced to a minimum in the form of a charge pump. One from the controller 20 Generated auxiliary voltage is for the provision of the control voltage U _St for the field effect transistor 10 and for providing the control voltages of the four semiconductor switching elements 41 . 42 . 43 . 44 intended.

So if the said control voltages from the control device 20 need not be generated, the generation of the auxiliary voltage within control device 20 also omitted and thus the current consumption of the control device 20 be reduced, whereby the control voltage U _St for the field effect transistor 10 can be lowered. In this way, the control device 20 and thus the entire drive device 100 effectively put in a power-saving mode. Reducing the control voltage U _St can reduce the power consumption of the control electronics as a result with the advantage of a CO ₂ reduction in the vehicle during a driving operation without active actuator function (eg wiping with front wiper drive).

In a variant of the drive device 100 may be provided to define electrical level of a control voltage U _St by means of a worst-case calculation with which the field-effect transistor 10 is safely switched through and the Verpolschutzfunktion the drive device 100 by means of the freewheeling diode of the field effect transistor 10 thus guaranteed.

As a further variant of the drive device 100 is conceivable, a voltage measurement over the field effect transistor 10 provided. The voltage measurement can, for example, at measuring points 11 . 12 be made, whereby an electrical voltage across the freewheeling diode of the field effect transistor 10 is determined. By means of the measured voltage, the control voltage U _{St can be} regulated, so that by means of the control device 20 the control voltage U _{St of} the field effect transistor 10 is always provided in sufficient amount. In this way it is possible to use the field effect transistor 10 with a control voltage U _St in a range between about 6 V and about 8 V durchzuschalten.

In the event that over the field effect transistor 10 no electrical voltage is measured, it means that the field effect transistor 10 is turned on and the control voltage U _{St is} sufficiently high. If, however, about 0.7 V at the freewheeling diode of the field effect transistor 10 fall, this means that the control voltage U _{St is} too low and must be increased to the field effect transistor 10 switch back through.

To realize the adjustable electrical control voltage U _St is in the control device 20 created a possibility to vary the height of the electric control voltage U _St in a range of, for example, about 6V to about 8V by software.

Further, the value of the control voltage U _St, for example, with the help of a corresponding data sheet simply to the type of field effect transistor of the field effect transistor used 10 be adjusted.

By means of the continuous voltage measurements, it is possible to detect whether the field effect transistor 10 when switched on, in a linear mode or in the off state. In this way, a control of the control voltage U _St can be realized. A maximum power reduction can be achieved by a permanent non-activation of the power amplifier 40 be reached, in which case the entire drive device 100 with the field effect transistor 10 permanently off.

A motor vehicle with activated front wiper has a compared to a total operating time of the motor vehicle of about 8500 hours short service life of about 800 hours. The predominant duration, however, is communication between the communication device 30 and a controller instead, the controller 20 is not needed if the windscreen wiper is not operated and thereby the power amplifier 40 not controlled. In this case, the control voltage U _St for the field effect transistor 10 lowered.

2 shows a schematic flow diagram of an embodiment of the method according to the invention.

In one step 300 is generating an electrical control voltage U _St for the field effect transistor 10 by means of the control device 20 carried out, wherein by means of the control device 20 an adjustable in height electrical control voltage U _St for a gate of the field effect transistor 10 provided.

In one step 310 becomes the field effect transistor 10 with a first defined control voltage switched through when the power amplifier 40 is controlled.

If, however, the power amplifier 40 is not driven, is in one step 320 the field effect transistor 10 with a second defined control voltage, which is lower than the first control voltage, switched through.

The decision about the setting of the control voltage U _St is made by the communication device 30 hit, the three states of the final stage 40 can recognize: for example, a normal operation (actuation of the electric motor 200 ) a pure communication operation of the communication device 30 with a control unit (without operation of the electric motor 200 ) and a sleep mode.

Preferably, the inventive method can be implemented as a software program, whereby a simple update or update or upgrade of the method is possible. The software program may, for example, in a Mikrorecheneinrichtung (not shown), in the control device 20 is arranged to be implemented.

In summary, the present invention proposes a drive device for an electric motor, by means of which it is advantageously possible, while maintaining a functionality, to significantly reduce an electrical power consumption of the drive device. Technically, this can be justified by the fact that a charge pump within the control device in a power-saving mode is not so highly stressed or can be dimensioned smaller, whereby the supply current I _S for the control device 20 and thus the entire drive device 100 is minimized.

Advantageously, it is possible in this way that in a purely communicating operation of the drive device 100 the current consumption can be limited to approx. 25 mA.

Although the invention has been described above with reference to specific embodiments, it is by no means limited thereto. The person skilled in the art will thus initially also realize embodiments which are not or only partially described without departing from the essence of the invention.

LIST OF REFERENCE NUMBERS

10

 Field Effect Transistor

11, 12

 measuring points

20

 control device

30

 communicator

40

 final stage

41 ... 44

 Semiconductor switching elements

50

 Communication Interface

60

 clock

70

 software

70a

 section

70b

 section

100

 driving

200

 electric motor

GND

 ground potential

I _S

 Current of the control device

U

 supply voltage

U _P

 plateau

U _St

 control voltage

Claims (10)

Drive device ( 100 ) for an electric motor ( 200 ), comprising: - an electronic control device ( 20 ) for driving an output stage ( 40 ); and - one in an electrical supply circuit of the drive device ( 100 ) arranged field effect transistor ( 10 ); - wherein by means of the control device ( 20 ) in dependence on a drive state of the output stage ( 40 ) a height-adjustable electrical control voltage (U _St ) for a gate of the field effect transistor ( 10 ) is available; - wherein the field effect transistor ( 10 ) is switchable with a first defined control voltage (U _St ) when the power amplifier ( 40 ) is controlled; and - wherein the field effect transistor ( 10 ) with a second defined control voltage (U _St ), which is lower than the first defined control voltage (U _St ) is switched through when the power amplifier ( 40 ) is not addressed. Drive device ( 100 ) according to claim 1, characterized in that in the event that the final stage ( 40 ) is not activated, the control voltage (U _St ) by means of the control device ( 20 ) defined is lowered, wherein a plateau value (U _P ) of the control voltage (U _St ) defined remains exceeded. Drive device ( 100 ) According to claim 1 or 2, characterized in that the control voltage (U _St) (by means of the control device 20 ) is configurable. Drive device ( 100 ) according to one of claims 1 to 3, characterized in that the control voltage (U _St ) of the field effect transistor ( 10 ) by means of the control device ( 20 ) is controllable. Drive device ( 100 ) according to any one of the preceding claims, characterized in that for generating the control voltage (U _St ) one within the control device ( 20 ) can be used, wherein by means of the charge pump, an electrical auxiliary voltage can be generated, by means of the semiconductor switching elements ( 41 . 42 . 43 . 44 ) of the final stage ( 40 ) are controllable. Drive device ( 100 ) according to claim 5, characterized in that the field effect transistor ( 10 ) of the same type as the semiconductor switching elements ( 41 . 42 . 43 . 44 ) of the final stage ( 40 ). Method for controlling an electric motor ( 200 ) by means of a drive device ( 100 ) according to one of the preceding claims, comprising the steps: - generating an electrical control voltage (U _St ) for the field effect transistor ( 10 ) by means of the control device ( 20 ), wherein by means of the control device ( 20 ) a height-adjustable electrical control voltage (U _St ) for a gate of the field effect transistor ( 10 ) provided; - wherein the field effect transistor ( 10 ) is switched through with a first defined control voltage (U _St ) when the power amplifier ( 40 ) is controlled; and - wherein the field effect transistor ( 10 ) with a second defined control voltage (U _St ), which is lower than the first defined control voltage (U _St ), is switched through when the power amplifier ( 40 ) is not controlled. Method according to claim 7, wherein in case the final stage ( 40 ) is controlled, the control voltage (U _St ) defined is lowered so that it assumes at least a defined value of a plateau voltage (U _P ), in the field effect transistor (U 10 ) remains switched through. Method according to claim 7 or 8, wherein one above the field effect transistor ( 10 ) falling voltage is determined, wherein by means of the determined voltage, a control of the control voltage (U _St ) by means of the control device ( 20 ) is carried out. Computer program product with program code means for carrying out the method according to one of claims 7 to 9, when it is on a electronic control device ( 20 ) or stored on a data medium.

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