DE102019208587A1 - Control circuit, parking lock system and motor vehicle - Google Patents

Abstract

The invention relates to a control circuit (1) for controlling a power supply for operating an inductive load (2) of a motor vehicle (3), having a PWM generator (4) for generating a clocked control signal modulated in a pulse width with a first generator channel (5) and a second generator channel (6), a filter device (7) for filtering the control signal and a circuit output (8) with a first circuit channel (9) and a second circuit channel (10) for electrically coupling the inductive load (2) to the control circuit ( 1), the filter device (7) being arranged between the PWM generator (4) and the circuit output (8). According to the invention, the filter device (7) is designed as an LCR filter device. The invention also relates to a parking lock system (19) for a motor vehicle (3) and a motor vehicle (3) with a parking lock system (19).

Description

The present invention relates to a control circuit for controlling a power supply for operating an inductive load of a motor vehicle. The invention also relates to a parking lock system for a motor vehicle and a motor vehicle with a generic parking lock system.

In motor vehicles there are a number of electromechanical systems, such as, for example, electric parking locks, which can be operated by means of a control circuit designed for this purpose. Electric parking locks have an electrically operated parking lock actuator which is designed to block a transmission, an axle or the like of the motor vehicle and thus to activate or deactivate the parking lock. In motor vehicles with an integrated electrical parking lock actuator, an electromagnet designed as a holding magnet for holding the parking lock actuator in a position, such as a locking position or a release position, can be controlled by means of a control circuit. For reasons of functional reliability, the holding magnet is controlled by a remote external control unit (referred to as selector lever in the following text). Due to the separation between the holding magnet and the control circuit, an on-board power supply line is required to connect the two components.

In order to ensure an acceptable power loss in the electromagnet as well as a tightening force independent of the electrical system voltage of the vehicle electrical system, a direct electrical coupling of the electromagnet with the electrical system is avoided. Instead, the electromagnet is operated with a constant current. Such an energy supply to the electromagnet is implemented, for example, by means of a control device with a clocked voltage signal, the pulse width of which is modulated. This is also referred to as pulse width control or PWM control. Using this method, the voltage on the electromagnet can be controlled by means of the control device and the current through the electromagnet can be regulated by means of a superordinate regulation by the control device.

Parking lock actuators are usually installed near the interior of the motor vehicle, for example under the center shelf. In order to avoid disturbing noises for the occupants of the motor vehicle, a PWM frequency above the hearing limit is used.

The problem here is that electrical leads between the parking lock actuator and the selector lever can be several meters long. Due to a PWM frequency above 16 kHz, the electrical supply line and also parts of the parking lock actuator emit the PWM frequency and the associated harmonics electromagnetically. This can lead to interference with other electrical systems of the motor vehicle or a violation of the EMC limit values to be observed.

Disturbances in the lower radio band close to the PWW (100kHz - 150kHz) are to be viewed critically because they can influence the availability of the "Keyless Entry & Start System", which also operates in the long wave range, for wireless engine start release.

One way of eliminating these problems is to use an alternative control technology that supplies the electromagnet with a purely controllable DC voltage. Alternatively, additional shielding of the on-board network cabling can be provided. Both measures lead to an increase in component costs or assembly costs and thus an increase in the production costs of the motor vehicle. Conventional EMC interference suppression measures in the control electronics are generally less suitable for suppressing low-number harmonics or they may increase the power loss in the control circuit (switching losses).

From the DE 10 2011 113 975 A1 there is known a control circuit for a motor vehicle for controlling the supply of power to an inductive load. Interference signals are to be filtered out of a clocked power signal by means of an LCD filter device arranged on the control circuit. The DE 10 2016 105 493 A1 discloses a control circuit having a filter device in which a capacitor and a coil are connected in series. Diodes are also required in this control circuit. A disadvantage of these control circuits is the use of complex diodes which, for example, lead to increased production costs.

It is therefore the object of the present invention to eliminate or at least partially eliminate the disadvantages described above in a control circuit of a parking lock system and of a motor vehicle. In particular, it is an object of the present invention to provide a control circuit To create parking lock system and a motor vehicle that can be produced in a simple and inexpensive manner and / or avoid or at least reduce interference with other technical vehicle systems.

The above problem is solved by the patent claims. Accordingly, the object is achieved by a control circuit for controlling a power supply for operating an inductive load of a motor vehicle with the features of independent claim 1, by a parking lock system for a motor vehicle with the features of independent claim 8 and by a motor vehicle with the features of independent claim 10 solved. Further features and details of the invention emerge from the subclaims, the description and the drawings. Features and details that are described in connection with the control circuit according to the invention naturally also apply in connection with the parking lock system according to the invention and the motor vehicle according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is or can always be made to each other.

According to a first aspect of the invention, the object is achieved by a control circuit for controlling a power supply for operating an inductive load of a motor vehicle. The control circuit has a PWM generator for generating a clocked control signal modulated in a pulse width with a first generator channel and a second generator channel, a filter device for filtering the control signal and a circuit output with a first circuit channel and a second circuit channel for electrically coupling the inductive load to the Control circuit on. The filter device is arranged between the PWM generator and the circuit output. According to the invention, the filter device is designed as an LCR filter device.

The PWM generator is designed to generate a clocked voltage signal, in particular with a relatively low impedance, with a modulated pulse width. To output the voltage signal, the generator has two generator channels, namely the first generator channel and the second generator channel. The first generator channel and the second generator channel are preferably electrically coupled to one another via a diode (in the function of a freewheeling diode for the activated inductance and the LCR filter network). The generator channels can be designed as a push-pull output stage, but also as a single output stage in which one of the generator channels has a fixed potential (e.g. electrical system potential or ground).

To connect the inductive load, the control circuit has two circuit channels, namely the first circuit channel and the second circuit channel. It can be provided that the second generator channel is electrically coupled directly to the second circuit channel.

The first circuit channel is preferably electrically coupled to the second circuit channel by means of the filter device. In addition, the first generator channel is preferably electrically coupled to the first circuit channel by means of the filter device. In addition, the filter device is designed as an LCR filter device. This means that the filter device has at least one inductance such as a coil, at least one capacitance such as a capacitor and at least one resistance such as an ohmic resistance.

The control circuit according to the invention is particularly suitable when an inductive load is to be controlled via a PWM signal. This is a compromise between a real DC voltage control (such as a DCDC converter) and the control of the inductive load with a pure square-wave voltage, i.e. an unfiltered signal.

When controlling inductive loads by means of a square-wave signal, the current is usually already sufficiently smoothed over the inductance, with the control voltage on the supply line changing in time with the PWM frequency. The inductance as a signal sink has a significant resistance for the PWM frequency and the higher harmonics. Effective smoothing of the output voltage using a simple additional inductance is often difficult because, due to the high resistance of the signal sink, this would have to be in the order of magnitude of the inductance to be controlled and thus possibly become excessively large. Pulse shaping of the square-wave signal of the generator can be achieved by means of the proposed filter device, it being possible to use a relatively small inductance.

By setting the natural resonance of the network to a frequency below the actual PWM frequency, both the actual fundamental wave and the harmonics of the PWM signal can be attenuated. The intrinsic attenuation or quality of the network can thus be adapted in such a way that when the PWM modulation, for example through control processes, does not lead to inadmissible transient processes. In this way, impermissible excessive voltage increases or negative voltages at the output of the network can be avoided.

A frequency response of the network can be represented as follows: $$G\left(\omega \right)=\frac{\frac{1}{j\omega \mathrm{C.}}+\mathrm{R.}}{\mathrm{R.}+j\omega \mathrm{L.}+\frac{1}{j\omega \mathrm{C.}}}$$

The amplitude response then results from: $$\mathrm{A.}\left(f\right)=\sqrt{\frac{1+{\left(2\pi f\mathrm{R.}\mathrm{C.}\right)}^2}{{\left(1+{\left(2\pi f\right)}^2\mathrm{L.}\mathrm{C.}\right)}^2+{\left(2\pi f\mathrm{R.}\mathrm{C.}\right)}^2}}$$

The internal attenuation of the pure LCR filter network is calculated as follows: $$\mathrm{D.}=\frac{1}{2}{\mathrm{<figure-callout\; id="0"\; label="R.\; N"\; filenames="DE102019208587A1\_0006.png"\; state="\{\{state\}\}">R.</figure-callout>}}_N\sqrt{\frac{{\mathrm{C.}}_N}{{\mathrm{L.}}_{\mathrm{R.}}}}$$

The resonance frequency at which the maximum amplitude increase occurs is calculated as: $$f_r={\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="DE102019208587A1\_0006.png"\; state="\{\{state\}\}">f</figure-callout>}}_0\frac{1}{2\mathrm{D.}}\sqrt{\sqrt{\mathrm{8th}{\mathrm{D.}}^2+1}-1=}\frac{1}{2\pi {\mathrm{C.}}_{\mathrm{<figure-callout\; id="0"\; label="N\; R.\; N"\; filenames="DE102019208587A1\_0006.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{R.}}_N{0}_{}}\sqrt{\sqrt{2{\mathrm{<figure-callout\; id="0"\; label="R.\; N"\; filenames="DE102019208587A1\_0006.png"\; state="\{\{state\}\}">R.</figure-callout>}}_N{}^2\frac{{\mathrm{C.}}_N}{{\mathrm{L.}}_N}+1}-1}\text{With}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="DE102019208587A1\_0006.png"\; state="\{\{state\}\}">f</figure-callout>}}_0=\frac{1}{2\pi \sqrt{{\mathrm{L.}}_N{\mathrm{C.}}_N}}$$

The design is preferably carried out in such a way that the amplitude resonance is so far below the PWM frequency that the fundamental wave of the PWM is already attenuated. The harmonics of the PWM frequency can be attenuated more strongly in accordance with the transfer function. In addition, such a design is preferred that the frequency band is attenuated as evenly as possible. This can be ensured by a corresponding self-damping of the LRC network and a suitably large distance between the PWM frequency and the resonance frequency.

In a preferred design, the inductance is 470 μH, the capacitance is 470 nF and the resistance is 2.2 Ω. This results in a resonance frequency of 10.695 kHz. The inductive load or the actuator for this design case has an inductance of 70 mH and a resistance of 5.4 Ω. It is controlled with a PWM frequency of 20 kHz, a voltage of 12 V and, in stationary operation, with a pulse rate of approx. 36%. As a result, the PWM frequency in the fundamental wave is attenuated by approx. 8 dB and the harmonics in the range between 100 kHz and 150 kHz by approx. 40 dB.

A control circuit according to the invention has the advantage over conventional PWM control circuits that a control signal for controlling an inductive load can be provided with simple means and in a cost-effective manner, which causes significantly less interference in other electrical systems of a motor vehicle than control signals of conventional control circuits with square-wave signals . This is achieved by largely loss-free, sinusoidal-like pulse shaping of the original square-wave signal, which has attenuated harmonics and a damped fundamental frequency compared to a corresponding square-wave signal.

According to a preferred further development of the invention, it can be provided in a control circuit that an inductance input of an inductance of the filter device is electrically coupled to one end of the first generator channel, and that an inductance output of the inductance is connected via a series connection of a capacitance of the filter device and a first resistance of the filter device is electrically coupled to the second generator channel. It is preferred here that the inductance output of the inductance is electrically coupled directly to the first circuit channel. Preferably the second is Generator channel electrically coupled directly to the second circuit channel. Such a filter device can be produced with simple means and in a cost-effective manner and is designed to ensure particularly advantageous damping of the fundamental wave.

It is preferred according to the invention that the inductance is connected in parallel with a second resistor of the filter device. A second resistor has the advantage that it provides additional damping of high-frequency natural oscillations, which are based on a non-ideal inductance, with simple means and in a cost-effective manner.

More preferably, the second resistor has an impedance that is greater than an impedance of the first resistor. The impedance of the second resistor is preferably at least twice as great, particularly preferably at least four times as great as the impedance of the first resistor. A second resistor designed in this way has the advantage that a negative impairment of the useful signal attenuation by the second resistor is reduced all the more, the larger the second resistor is designed.

In a particularly preferred embodiment of the invention, it can be provided in a control circuit that a capacitance input of the capacitance is electrically coupled to the inductance output of the inductance, and that a resistance output of the first resistor is electrically coupled to the second generator channel. This has the advantage that a control circuit is provided with simple means and in a cost-effective manner, by means of which a particularly advantageous attenuation of the PSM signal can be achieved.

The inductance output is preferably electrically coupled to the first circuit channel and the resistance output is electrically coupled to the second circuit channel. This has the advantage that a control circuit is provided with simple means and in a cost-effective manner, by means of which a particularly advantageous attenuation of the PSM signal can be achieved.

According to a preferred embodiment of the invention, the filter device is designed such that an amplitude resonance of the filter device is below a PWM frequency of the PWM generator. In this way, an advantageous attenuation of the fundamental wave and the near harmonics of the PWM signal is improved with simple means and in a cost-effective manner.

According to a second aspect of the invention, the object is achieved by a parking lock system for a motor vehicle. The parking lock system has a parking lock actuator and a holding magnet for holding the parking lock actuator in one position. According to the invention, the parking lock system has a control circuit according to the invention for controlling a power supply for operating the holding magnet. The parking lock actuator is preferably adjustable between a locking position and a release position. In the blocking position, for example, a gear wheel of a transmission and / or a wheel of the motor vehicle can be blocked. In this way, unintentional rolling of the motor vehicle can be prevented. In the release position, for example, the gear wheel or the wheel is released by the parking lock actuator. In the release position, the motor vehicle is ready to drive.

The parking lock system described results in all the advantages that have already been described for a control circuit according to the first aspect of the invention. Accordingly, the parking lock system according to the invention has the advantage over conventional parking lock systems that a control signal with a damped fundamental wave and damped near harmonics for controlling an inductive load can be provided with simple means and in a cost-effective manner, which significantly less interference with other electrical systems of a motor vehicle caused as control signals of conventional parking lock systems.

The parking lock system particularly preferably has an actuator control circuit different from the control circuit for operating the parking lock actuator. This has the advantage that security of the parking lock system is improved.

• 1 einen Schaltplan einer bevorzugten Ausführungsform eines erfindungsgemäßen Parksperrensystems,
• 2 in einem Diagramm eine Amplitudenfunktion einer bevorzugten Auslegung des erfindungsgemäßen Parksperrensystems, und
• 3 in einer Seitenansicht eine bevorzugte Ausführungsform eines erfindungsgemäßen Kraftfahrzeugs.

A control circuit according to the invention, a parking lock system according to the invention and a motor vehicle according to the invention are explained in more detail below with reference to drawings. They each show schematically:

• 1 a circuit diagram of a preferred embodiment of a parking lock system according to the invention,
• 2 in a diagram an amplitude function of a preferred design of the parking lock system according to the invention, and
• 3 in a side view a preferred embodiment of a motor vehicle according to the invention.

Elements with the same function and mode of operation are in the 1 to 3 each provided with the same reference numerals.

In 1 Figure 3 is a circuit diagram of a preferred embodiment of a parking lock system according to the invention 19th for a motor vehicle 3 (see. 3 ) shown schematically. The parking lock system 19th has a parking lock actuator 20th for fixing a component of a drive system of the motor vehicle 3 such as a gear wheel, a wheel axle or the like, and an actuator control circuit 22nd to control the parking lock actuator 20th on. Furthermore, the parking lock system 19th one as a holding magnet 21st trained inductive load 2 for fixing the parking lock actuator 20th in one position and a control circuit 1 to control the inductive load 2 on.

The control circuit 1 has a PWM generator 4th for generating a PWM voltage and a filter device 7th to filter the PWM voltage. In this embodiment there are three alternative embodiments of the PWM generator 4th shown side by side, only each of these embodiments for realizing the PWM generator 4th sufficient. The PWM generator has a first generator channel as outputs 5 and a second generator channel 6th on. The first generator channel 5 is with an inductance input 11 an inductance 12 the filter device 7th electrically coupled. An inductance output 13th the inductance 12 is with a first circuit channel 9 a circuit output 8th the control circuit 1 as well as a capacity input 17th a capacity 14th the filter device 7th electrically coupled. The capacity 14th is having an initial resistance 15th connected in series with a resistor output 18th with the second generator channel 6th and a second circuit channel 10 of the circuit output 8th is electrically coupled. The inductance 12 is with an optional second resistor 16 connected in parallel. The first circuit channel 9 and the second circuit channel 10 are for controlling the inductive load 2 electrically coupled with this.

2 shows an amplitude function of a preferred design of the parking lock system according to the invention schematically in a diagram. This diagram is a preferred design of the control circuit 1 where the inductance is 470 µH, the capacitance is 470 nF, the first resistor is 2.2 Ω and the resonance frequency is 10.695 kHz. An inductance of the inductive load 2 is 70 mH, and a resistance of the inductive load 2 is 5.4 Ω. The PWM generator 4th is designed to generate a PWM frequency of 20 kHz with a PWM voltage of 12 V and in stationary operation with a pulse width of about 36%. As can be seen from the diagram, the PWM frequency is determined by means of the filter device 7th attenuated in the fundamental wave by approx. 8 dB. The harmonics in the range between 100 kHz to 150 kHz are filtered using the filter device 7th attenuated by about 40 dB.

In 3 is a preferred embodiment of a motor vehicle according to the invention 3 shown schematically in a side view. The car 3 has a parking lock system according to the invention 19th on, which in this example is used to lock a front wheel or the two front wheels of the motor vehicle 3 is trained.

List of reference symbols

1

Control circuit

2

inductive load

3

Motor vehicle

4th

PWM generator

5

first generator channel

6th

second generator channel

7th

Filter device

8th

Circuit output

9

first circuit channel

10

second circuit channel

11

Inductance input

12

Inductance

13

Inductance output

14th

capacity

15th

first resistance

16

second resistance

17th

Capacity input

18th

Resistance output

19th

Parking lock system

20th

Parking lock actuator

21st

Holding magnet

22nd

Actuator control circuit

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102011113975 A1 [0008]
• DE 102016105493 A1 [0008]

Claims (10)

Control circuit (1) for controlling a power supply for operating an inductive load (2) of a motor vehicle (3), having a PWM generator (4) for generating a clocked control signal modulated in a pulse width with a first generator channel (5) and a second generator channel (6), a filter device (7) for filtering the control signal and a circuit output (8) with a first circuit channel (9) and a second circuit channel (10) for electrically coupling the inductive load (2) to the control circuit (1), wherein the filter device (7) is arranged between the PWM generator (4) and the circuit output (8), characterized in that the filter device (7) is designed as an LCR filter device. Control circuit (1) after Claim 1 , characterized in that an inductance input (11) of an inductance (12) of the filter device (7) is electrically coupled to one end of the first generator channel (5), and that an inductance output (13) of the inductance (12) via a series connection of a Capacitance (14) of the filter device (7) and a first resistor (15) of the filter device (7) is electrically coupled to the second generator channel (6). Control circuit (1) after Claim 2 , characterized in that the inductance (12) is connected in parallel with a second resistor (16) of the filter device (7). Control circuit (1) after Claim 3 , characterized in that the second resistor (16) has an impedance which is greater than an impedance of the first resistor (15). Control circuit (1) according to one of the Claims 2 to 4th , characterized in that a capacitance input (17) of the capacitance (14) is electrically coupled to the inductance output (13) of the inductance (12), and that a resistance output (18) of the first resistor (15) is connected to the second generator channel (6) is electrically coupled. Control circuit (1) after Claim 5 , characterized in that the inductance output (13) is electrically coupled to the first circuit channel (9) and the resistance output (18) is electrically coupled to the second circuit channel (10). Control circuit (1) according to one of the preceding claims, characterized in that the filter device (7) is designed such that an amplitude resonance of the filter device (7) is below a PWM frequency of the PWM generator (4). Parking lock system (19) for a motor vehicle (3), comprising a parking lock actuator (20) and a holding magnet (21) for holding the parking lock actuator (20) in one position, characterized in that the parking lock system (19) for controlling a power supply for operating the Holding magnet (21) has a control circuit (1) according to one of the preceding claims. Parking lock system (19) according to Claim 8 , characterized in that the parking lock system (19) for operating the parking lock actuator (20) has an actuator control circuit (22) different from the control circuit (1). Motor vehicle (3) with a parking lock system (19), characterized in that the parking lock system (19) as a parking lock system (19) according to Claim 8 or 9 is trained.

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