DE102017121175A1 - Control circuit for driving an electric motor - Google Patents

Abstract

A control circuit (2) having at least two different interfaces (4, 5) for receiving control signals (18, 21), which are connected to a common control input (13), having a switching unit (9) for activating one of the interfaces ( 4.5), with a recognition unit (14) for detecting control signals (18, 21) valid for the interfaces (4, 5), with a control unit for processing the control signals (18, 21) of the active interface (4, 5) , and with a control output (16) to which a device (3) to be controlled by the control unit (2) can be connected, the detection unit (9) being designed to activate the interface (4, 5) for which valid ones Control signals (18,21) abut the control input (13).

Description

The invention relates to a control circuit having at least two different interfaces for receiving control signals, comprising a switching unit for activating in each case one of the interfaces with a control unit for processing the control signals of the active interface, and having a control output to which a device to be controlled by the control unit is connectable.

Such control circuits are used for example in motor vehicles for driving servomotors. Exemplary applications of actuators in motor vehicles are seat adjusters, air conditioning flap plates, headlight plates, grille flap regulators, window regulators and many more. As a rule, the control circuit is combined with the servomotor to form an actuator unit.

To transmit the control signals, for example "window open", the control circuit has an interface which can receive control signals in a format specific to this interface. The drive circuit further comprises a microprocessor or microcontroller, which converts this control signal into a control for the servo motor and outputs to a control output to which a servo motor is connected.

In older vehicles, the transmission of control signals via a pulse width modulation (PWM) interface takes place. The control commands are defined for example via the duty cycle. For example, a duty cycle of 10% to 20% may mean "window open" and a duty cycle of 70% to 80% "window closed".

In newer motor vehicles, control signals are transmitted via a Local Interconnect Network (LIN) interface. The LIN bus has the advantage over the PWM interface that many different actuators can be addressed via a common data line. The distinction is made by the transmission and evaluation of an address.

For an actuator unit to be universally applicable in motor vehicles, it is necessary that it has both a LIN and a PWM interface, which can be controlled via various connection contacts of a connector. This allows, for example, a mechanically identical actuator unit in different vehicle models that use different interfaces to use. In an actuator unit, therefore, the internal wiring must be done for both interfaces, whereby the actuator unit is more expensive and expensive.

Since only control signals can always be received and evaluated by an interface, the control circuit has a switching unit with which the respective valid interface can be activated. This switching unit can be switched externally, for example by a switch or a switching input. The control circuit can also have an automatic detection, which detects at which interface a signal is applied. Thereby, the used interface in each vehicle is simply defined and selected by the harness, or the wiring. Such automatic detection can be made very simple here, since there is practically no installation situation in a motor vehicle in which the connection contacts of both interfaces are connected.

The object of the invention is to provide a control circuit of the aforementioned type, which is easier and less expensive to produce and allows extended applications.

This object is achieved by a control circuit having the features of the main claim.

The invention provides a control circuit having at least two different interfaces for receiving control signals, wherein the control circuit comprises a switching unit for activating each one of the interfaces, and a control unit for processing the control signals of the active interface, and a control output to which a by the control unit to be controlled device is connected includes. At least two of the different interfaces are connected to a common control input. Furthermore, the control circuit has a detection unit for detecting control signals valid for the interfaces, and the detection unit is designed to activate the interface for which valid control signals are present at the control input.

Because at least two of the different interfaces are connected to a common control input in the control circuit according to the invention, for example, only one plug contact is necessary.

Any necessary external wiring, for example with a protection circuit for the interface, is thus only necessary once more. The drive circuit can thus be integrated more cost effectively in an actuator unit.

The control circuit according to the invention also has a detection unit for detecting valid control signals for the interfaces and the detection unit is designed to activate an interface with valid signals.

The detection unit is preferably designed such that it simultaneously monitors the control input for valid control signals for all existing interfaces.

In an alternative embodiment, a separate detection unit may be present for each interface, but these are each connected to the common control input.

In one, adapted in particular for motor vehicles embodiment of the invention, the control circuit has two interfaces, wherein the first interface is a PWM interface and the second interface is a LIN interface.

The detection of a valid signal can be done in many ways and is particularly dependent on the interface. Analog control signals could be recognizable, for example, by a certain voltage.

As a rule, however, the control signals transmit the control information in a digital form. The control signal is therefore usually a square wave signal. In an advantageous embodiment of the invention, the detection unit therefore has means for detecting the duty cycle and / or the frequency of the control signals at the control input. Certain interfaces sometimes require characteristic frequencies, so that the frequency of the control signal may be a feature of a valid signal.

Regardless of the frequency and the duty cycle of the control signal can be specified by the interface specification. Or the duty cycle is the control information, such as in a PWM interface. In both cases, the duty cycle is an important criterion for the validity of the control signal.

The detection unit may have hardware components for determining the frequency and / or the duty cycle. However, the implementation can be time-consuming and expensive.

It is therefore particularly advantageous if the drive circuit has a microprocessor, a microcontroller or at least one processor core which is designed and set up to execute an operating program. In this operating program, in addition to the implementation of the control signals, the detection of the control signals may also be implemented in software, at least in part.

For this purpose, it is expedient if the detection unit is coupled to the microprocessor and is adapted to send interrupt signals to the microprocessor as soon as the control signal specified events occur and can be reacted in the operating program of the microprocessor to these signals. In this way, the detection of a valid signal is carried out partly in the operating program and partly in hardware.

In particular, the detection unit may be designed to trigger an interrupt on rising edges of the control signal.

In one embodiment of the invention, the control circuit is designed as a motor controller for controlling an electronically commutated DC motor and has a full bridge circuit. The drive circuit is thus usable as a full motor controller without external components. It is irrelevant whether the full bridge is designed as H-bridge for DC motors, B6 bridge for various 3-phase motors or as a double H-bridge for example, stepper motors. The type of connected used engine is not relevant to the invention. In the following, the invention will be described by way of example with reference to a 3-phase brushless DC motor.

For driving a power motor, in particular in the case of an embodiment as an integrated circuit, there may also be an interface for driving the bridge switches of a full-bridge circuit.

The drive circuit may be constructed as an electronic circuit with discrete components. However, it may also have one or more integrated circuits. However, it is particularly advantageous if the drive circuit itself is formed as a whole as an integrated circuit and / or as a one-chip system (English system-on-a-chip, short SoC). In this way, all components and components important for the function can be combined and produced cost-effectively as a functional unit. In particular, this simplifies the use in an actuator unit, since in addition to the drive circuit only a few further components are required. An actuator unit can be designed to be particularly space-saving and inexpensive.

The switching unit for activating each interface can be an actual switch, with each of the control input can be connected to the respective interface. However, the switching unit can also be realized purely in the operating program, so that can be dispensed with additional hardware components. In this embodiment, the activation of an interface can be done simply by the control signals are interpreted differently, so be processed in another interface program.

The invention furthermore also includes an actuator unit, in particular an actuator for a motor vehicle, having a control circuit according to the invention and an electric motor connected to the control output.

In addition to the control circuit according to the invention, the invention also includes a method for detecting valid control signals, which is carried out in particular in a control circuit according to the invention.

This method according to the invention is characterized in particular by the recognition unit recognizing the validity of the control signals by evaluating the frequency and / or the duty cycle and activating the first interface to which a valid control signal is applied.

In particular, the monitoring of the various interfaces always takes place simultaneously. As soon as a signal valid for an interface has been detected, this interface is activated. Thus, the other interfaces are disabled and are no longer queried.

Preferably, the detection and activation of an interface takes place only once when setting up the control circuit or when switching. As a rule, no change of interfaces occurs during operation, so that this method does not entail any disadvantage. A permanent selection of the interface then takes place, for example, in the final configuration of the device to be controlled, for example an actuator, in production. Of course, for other applications, a different approach may be necessary or useful, so that the detection can also be repeated, for example, permanently or intermittently.

In an advantageous embodiment of the invention, the detection unit for detecting a PWM signal sends an interrupt signal to the microprocessor for each rising edge of the control signal, where it determines the frequency and the duty cycle in a PWM interrupt routine. Once a predetermined number of control signals are valid, the PWM interface is activated. For example, a control signal may be considered valid if the predetermined number of consecutive frequency and duty control signals are substantially identical. This means within a negligible tolerance. In particular, the predetermined number may be between two and six valid signals.

In a further advantageous embodiment of the invention, the recognition unit waits for recognition of a LIN signal from a valid LIN header and then starts via an interrupt signal in the microprocessor, a LIN interrupt routine in which first the address of the LIN signal is evaluated , If the address and a subsequent data packet are valid, the LIN interface is activated.

In a further advantageous embodiment, the recognition of the interface used also after a faulty communication, for example, a predetermined time without valid signals again activated. As a result, the system can automatically return to normal operation even with a temporary faulty or faulty detection of the interface and thus work self-healing.

The invention is described below with reference to preferred embodiments with reference to the accompanying drawings.

• 1 ein Prinzipschaltbild eines Aktuators mit einer Ansteuerschaltung nach dem Stand der Technik,
• 2 ein Blockschaltbild einer erfindungsgemäßen Ansteuerschaltung,
• 3 ein Blockschaltbild einer alternativen erfindungsgemäßen Ansteuerschaltung,
• 4 ein Impulsdiagramm eines PWM-Steuersignals,
• 5 ein Impulsdiagramm eines LIN-Steuersignals,
• 6 ein Blockschaltbild eines Aktuators mit einer erfindungsgemäßen Ansteuerschaltung und
• 7 ein Blockschaltbild eines Aktuators mit einer erfindungsgemäßen Ansteuerschaltung mit einem zusätzlichen Signaleingang.

It shows:

• 1 FIG. 2 is a block diagram of an actuator with a drive circuit according to the prior art, FIG.
• 2 a block diagram of a drive circuit according to the invention,
• 3 a block diagram of an alternative driving circuit according to the invention,
• 4 a timing diagram of a PWM control signal,
• 5 a timing diagram of a LIN control signal,
• 6 a block diagram of an actuator with a drive circuit according to the invention and
• 7 a block diagram of an actuator with a drive circuit according to the invention with an additional signal input.

In 1 is a block diagram of an actuator unit 1 shown in the prior art. This actuator unit 1 For example, it may be a flapper in an automobile. The actuator unit 1 has a control circuit 2 and an electric motor 3 over which an actuator, in the example about a climate flap or radiator flaps, are moved. The electric motor 3 may optionally have a gearbox to produce higher actuating forces or actuating speeds.

The control circuit 2 has two interfaces through which control signals can be received. In the example, the first interface is a PWM interface 4 and the second interface a LIN interface 5 ,

The actuator unit 1 has a plug connection 6 on, with four plug contacts 7 , A plug contact 7-3 is over a protection circuit 8th with the PWM interface 4 connected. A second plug contact 7-2 is via a second protection circuit 8th with the LIN interface 5 connected. The other two plug contacts 7-1 and 7-4 lead the operating voltage (plug contact 7-4 ) or ground (plug contact 7-1 ).

The control circuit 2 further has an automatic switching unit 9 on, which is designed to activate one of the interfaces. In an automobile, it is practically impossible for control signals to be applied to both signal plug contacts. The detection of the active interface is therefore simply based on an applied voltage or the application of a signal.

The protection circuit 8th prevents damage to the control circuit 2 , in particular the interface components, by possibly incorrect wiring or voltage spikes. The protection circuit 8th has, for example, capacitors 10 , which are installed as filter capacitors, protection diodes 11 , Ferrite cores FB , active level shifter WHEN , Transistors Q and possibly other components. It is important that the protective circuits 8th are necessary for both interfaces. The actuator unit 1 Therefore, in the prior art requires a lot of effort for external wiring of the control circuit 2 ,

The control circuit 2 further shows a microcontroller 12 to implement the control signals and to control the servomotor 3 on. The control circuit 2 also has a full bridge circuit 15 on, with the a three-phase DC motor 3 is controllable.

The 2 now shows a first exemplary embodiment of a control circuit according to the invention 2 , The control circuit 2 has a control input 13 on, to which a control signal can be connected, for example via a plug contact as in 1 shown. The control input 13 is with a switching unit 9 connected to which the control signal is selectively applied to one of the two interfaces in the microcontroller 12 realized, is connectable.

With the control input 13 is still a recognition unit 14 connected, which recognizes valid signals for the interfaces and the switching unit 9 controls.

A full bridge circuit 15 is through the microcontroller 12 controlled and with a control output 16 connected to the example, an electric motor to be controlled is connected.

The recognition unit 14 is in addition to the microcontroller 12 connected. On the one hand, you can use this connection in the operating program of the microcontroller 12 Interrupts are triggered and on the other hand information about the switching position of the switching unit 9 to the microcontroller 12 be transmitted.

The arrangement of the two interfaces in the microcontroller is only an example and therefore in no way limiting. It would also be possible to design the interfaces as separate interface units.

An alternative embodiment of the invention is in 3 shown in which no separate switching unit is present. Rather, here is the switching unit in the microcontroller 12 integrated. However, the control of the switching unit also takes place here via the detection unit 14 that with a switching input 17 of the microcontroller 12 connected is. In the example, the control circuit has 2 a PWM interface 4 and a LIN interface 5 ,

The detection of a valid PWM control signal takes place, for example, as described below. In 4 is an example of a PWM control signal 18 shown. The PWM signal 18 is subject to a PWM interface specification, as follows:

• PWM frequency:

- nominal frequency: 200 Hz - Min. Freq .: 165Hz ± 5Hz - Max. Freq .: 235Hz ± 5Hz

• Duty cycle:

- Minimum: 10% ± 2% - Maximum: 90% ± 2% - Actuator open: 10% to 35% (± 2%) - Actuator closing: 65% to 90% (± 2%) - Initialize: 35% to 65% (± 2%)

In the detection unit 14 for the PWM control signals, a rising edge 19 of the PWM control signal 18 recognized. At every rising edge 19 will give an interrupt signal to the microprocessor 12 Posted. There, a PWM interrupt routine is started to determine the frequency and the duty cycle.

For this purpose, for example, a counter is started with the interrupt, which is stopped at the next interrupt. By comparing the counter readings of the individual counter runs can be determined whether the frequency is in the valid range and also remains constant.

In addition, to determine the duty cycle, in each case at the falling edge 20 the current meter reading is stored. From the ratio of this counter value to the counter value at the end of the period T the duty cycle can be determined. This must be for a predetermined number of periods T be essentially identical. In the example, the control signal is valid when ten consecutive periods T valid and identical. A single period T is valid if the frequency and the duty cycle correspond to the specification given above.

The falling flank 20 can through the detection unit 14 be detected and reported with another interrupt. However, it can also be recognized within the interrupt routine.

In this example, the detection is performed by a combination of hardware (detection unit) and software (interrupt routine). Of course, the detection can be done completely in hardware, with special frequency counter and the like blocks are necessary.

Once the control signal at the control input 13 is detected as a valid PWM signal, is via the switching unit 9 the PWM interface 4 activated. This means that all other existing interfaces are disabled. In the example of 2 becomes the control input 13 over the switching unit 9 with the PWM interface 4 connected. In the example of 3 turns off the microcontroller 12 the PWM interface 4 internally.

The detection of a LIN signal 21 is also combined in the recognition unit in the example 14 and the microcontroller 12 , In 5 is exemplary and schematically a LIN signal 20 shown. The LIN protocol prescribes a specific structure of a signal, so that the recognition unit 14 in hardware is set up on it. At the beginning of a LIN signal 20 is a break field 22 which consists of at least 13 low bits followed by a high bit. This is followed by a sync field 23 on, which consists of an alternating sequence of low and high bits, a total of 8 bits. In the method according to the invention, at the end of the sync field 23 an interrupt signal to the microcontroller 12 which starts a LIN interrupt routine.

Following the sync field 23 in the LIN signal, the receiver address of the LIN control signal 20 in an ID field 24 which is also 8 bits long. This address is evaluated in the LIN interrupt routine. If the recipient address does not match the own address, the control signal is not intended for the own device and therefore does not need to be considered. Even if there is a technical LIN signal, it is not valid for your own device. If the address matches, however, the subsequent data of the data field will also be the same 25 evaluated. If the data contains a valid command, the LIN signal becomes 20 Total recognized as valid and the LIN interface 5 activated. Activation takes place analogously as described above for the PWM interface.

Indicates the control circuit 2 other interfaces, other methods and ways to detect a valid signal may be necessary or useful. Decisive for the invention is merely that the detection of the various interfaces takes place simultaneously, since only one control input 13 is available. Serial detection, where one signal from one interface is first tested and then tested against another interface, takes too long and would not be reliable.

The recognition unit can therefore be set up for different interfaces. But it can also be present for each interface a separate detection unit.

The 6 shows an actuator unit according to the invention 1 , which is a control circuit according to the invention 2 and otherwise essentially the 1 equivalent. At the plug connection 6 However, here is only a plug contact 7-2 busy. This plug contact 7-2 is also here via a protection circuit 8th with the control input 13 the control circuit according to the invention 2 connected. In an automobile, the plug contact may now receive a PWM control signal or a LIN control signal.

A key advantage of the invention, and common to all embodiments, is that the control circuit 2 to the outside only one control input 13 having. Compared to the state of the art here is now only a protection circuit 8th necessary. The actuator unit 1 This makes it easier and cheaper to carry out. And also more versatile.

Another advantage of the invention is that at the vacant plug contact 7-3 additional functions of an actuator unit 1 can be realized. In 7 is an actuator unit 1 shown, which is essentially the 6 equivalent. The free plug contact 7-3 is here, however, with an additional input 26 the control circuit 2 connected, giving additional information to the control circuit 2 can be transmitted. In the example is the plug contact 7-3 externally with a simple switch 27 busy.

LIST OF REFERENCE NUMBERS

1

actuator

2

control circuit

3

electric motor

4

PWM interface

5

LIN interface

6

Connectors

7

plug contacts

7-1

plug contact

7-2

plug contact

7-3

plug contact

7-4

plug contact

8th

protection circuit

9

switching unit

10

capacitor

11

diode

12

microcontroller

13

control input

14

recognizer

15

full bridge

16

control output

17

switching input

18

PWM control signal

19

rising edge

20

falling edge

21

LIN control signal

22

Break field

23

Sync field

24

Address field

25

Data field

26

entrance

27

switch

WHEN

Active level shifter

Department

Ferrite core (English ferrite bead)

Q

transistor

R

resistance

T

period

Claims (12)

Control circuit (2) having at least two different interfaces (4, 5) for receiving control signals (18, 21), with a switching unit (9) for activating in each case one of the interfaces (4, 5) with a control unit (12) for processing the control signals (18,21) of the active interface, and with a control output (16), to which a by the control unit (12) to be controlled device (3) can be connected, characterized in that at least two of the different interfaces (4,5 ), are connected to a common control input (13), that the control circuit (2) has a detection unit (14) for detecting valid for the interfaces (4,5) control signals (18,21), and the detection unit (9) thereto is designed to activate that interface (4,5) for which valid control signals (18,21) applied to the control input (13). Control circuit (2) after Claim 1 , characterized in that the first interface is a PWM interface (4,5). Control circuit (2) after Claim 1 or 2 , characterized in that the second interface is a LIN (Local Interconnect Network) interface (4,5). Control circuit (2) according to one of Claims 1 to 3 , characterized in that the detection unit (14) comprises means for detecting the duty cycle and / or the frequency of the control signals (18,21) at the control input (13). Control circuit (2) according to one of Claims 1 to 4 , characterized in that the drive circuit (2) has a microprocessor (12) as a control unit, which is designed and set up to execute an operating program. Control circuit (2) after Claim 5 characterized in that the recognition unit (14) is coupled to the microprocessor (12) and is adapted to send interrupt signals to the microprocessor (12) as soon as specified events occur in the control signal (18,21) and an operating program of the microprocessor (12) is adapted to respond to these interrupt signals. Control circuit (2) according to one of Claims 1 to 6 , characterized in that the control circuit (2) as a motor controller for controlling an electronically commutated DC motor (3) is formed and has a full bridge circuit (15) and / or a control output (16) for controlling an electric motor or a full bridge circuit. Control circuit (2) according to one of Claims 1 to 7 , characterized in that the control circuit (2) as an integrated circuit and / or as a SoC (system-on-a-chip) is formed. Actuator (1) with a drive circuit (2) according to one of Claims 1 to 8th and an electric motor (3) connected to the control output (16). Method for detecting a valid control signal by a control circuit (2) according to one of Claims 1 to 8th , characterized in that the detection unit (14) detects the validity of the control signals (18,21) by evaluating the frequency and / or the duty cycle and the first interface, at which a valid control signal is applied, is activated. Method according to Claim 10 , characterized in that the detection unit (14) for detecting a PWM signal (18) for each rising edge (19) and / or falling edge (20) of the PWM signal (18) an interrupt signal to the microprocessor (12 ) and there in a PWM interrupt routine the frequency and / or the duty cycle is determined and as soon as a predetermined number of periods (T) are valid, the PWM interface (4) is activated. Method according to Claim 10 or 11 , characterized in that the detection unit (14) for recognizing a LIN signal (21) waits for a valid LIN header and then via an interrupt signal in the microprocessor (12) starts a LIN interrupt routine, in the first the address (24) of the LIN signal (21) is evaluated and if the address and a subsequent data field (25) are valid, the LIN interface (5) is activated.

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