The invention relates to a driver device for electrically driving a motor for sliding a panel of an electric window or sliding roof of a vehicle, the driver device being provided with a supply circuit for generating a pulse-width modulated supply voltage for driving the motor with a variable speed.

When the pulse width of the supply voltage increases, the motor will start to rotate faster. Conversely, when the pulse width of the supply voltage decreases, the motor will start to rotate more slowly.

A disadvantage of the known system is that through the construction of the motor there is a capacitive coupling between the motor windings and the motor housing. Through this undesired parasitic capacity, a square-wave voltage on the winding is passed on to the motor housing, so that the motor housing starts to emit electromagnetic radiation. Such electromagnetic radiation is undesired for various reasons. For one thing, it pollutes the airwaves and also it involves a small energy loss. To keep the current in this parasitic capacity small, the switching frequency is preferably not too high. However, to prevent objectionable noises, the frequency is preferably well above 15 kHz, for instance at 20 kHz.

To prevent the motor housing from going to generate electromagnetic radiation, it has been proposed to ground the motor housing directly via a capacity. However, this entails the disadvantage that large currents start to flow through the capacity and hence also through the ground wire. This in turn has as a consequence that large interferences are generated in the current path leading from the driver device to the motor. Moreover, it is not always constructionally possible to ground the motor housing adequately.

With a pulse-width modulated supply voltage (PWM), each time, briefly, the full supply voltage is presented to the motor. Through practical limitations, this time cannot be chosen randomly small, so that the full supply voltage is presented for a certain minimal time. This also holds for the so-called soft start of the PWM, whereby an increasingly longer voltage pulse is presented to the motor. As long as the motor does not yet run, and no counter-voltage is generated by the motor, high current peaks can occur. The only current limitation is the resistance of the wiring and the internal motor resistance. In case of a short circuit of the wiring, this latter resistance is not present either, and the current can become still greater. The peak current in the motor circuit is much greater than the average current. As a result, it is possible that switching means of the supply circuit for generating the PWM break down.

A further disadvantage of the known device is that the current is provided to the motor in pulses, so that any measuring of the motor current for the purpose of, for instance, detecting a squeezing is not a simple direct current measurement.

The object of the invention is to provide a driver device which can give a solution to a number of the above-outlined problems.

To that end, the driver device according to the invention is characterized in that the driver device is further provided with a rectifier circuit which is connected on one side with the supply circuit for obtaining, on the basis of the pulse-width modulated supply voltage, a direct voltage whose magnitude is dependent on the pulse width of the supply voltage, and which is connected on the other side with the motor for driving the motor with the direct voltage, the speed of the motor being dependent on the magnitude of the direct voltage.

As the motor is supplied with a direct voltage instead of an alternating voltage, no current will flow in the parasitic capacity between the windings and the motor housing anymore. In the situation where the motor housing is grounded, no current flows through the ground wire and the capacity anymore; in the situation where the motor is floating, no alternating voltage will be induced on the housing, and the motor will not generate any electromagnetic radiation anymore. The alternating voltage in the form of the pulse-width modulated supply voltage is present only in the driver device. In practice, this means that the alternating voltage is present only on "the print" of the driver device. As in this way no radiation is emitted, it is possible to increase the modulation frequency substantially. Thus, the modulation frequency can be chosen to be, for instance, about 100,000 kHz. This in turn provides the advantage that in the driver device smaller anti-interference components can be used, as well as smaller coils and smaller capacitors in the supply circuit.

When a short circuit occurs in a supply line of the driver device to the motor, this has as a consequence that this will not lead to very large currents in the supply voltage circuit. In the case of a soft start, the direct voltage is built up slowly, so that when a motor jams, or in the event of a short circuit of the motor cable, the current too will run up gradually. The peak value of the current remains equal to the average current. By virtue of the invention, the loading of the components through which the motor current flows is much smaller. The average current is measured, and when a particular threshold value is exceeded, the supply is cut off. Should this current limitation fail to function, there is always the main fuse of the car which will blow to prevent damages to the supply circuit.

In particular, it holds that the rectifier circuit is provided with a lowpass filter for smoothing the pulse-width modulated supply voltage.

Preferably, it holds here that the pass filter comprises at least one coil which is connected in series with the motor.

Also, it preferably holds that the pass filter comprises at least one capacitor which is connected in parallel with the motor.

In the event of a short circuit or at high currents through the motor when it has just been started, the capacitor will discharge and there will be a low direct voltage on this smoothing capacitor, so that the motor peak current is virtually equal to the average current.

A further advantage of the driver device according to the invention is that the motor can be placed freely. The motor does not need to be grounded, but may be grounded. In any case, grounding and cabling no longer have any influence on the interference behavior as a result of electromagnetic radiation, since the motor is driven with the direct voltage.

The invention further relates to an assembly of a slidable panel for a vehicle, such as an electric window or a sliding roof, at least one motor for driving the panel and a driver device as described above.

The invention will be further elucidated with reference to the drawing.

In the drawing:

• Fig. 1 shows a possible embodiment of a known driver device; and
• Fig. 2 shows a possible embodiment of a driver device according to the invention.

In Fig. 1 reference numeral 1 designates a driver device for electrically driving a motor 2 for sliding a panel of an electric window or sliding roof of a vehicle. The driver device is provided with a supply circuit 4 having input terminals 6 to which a direct voltage of the vehicle is applied. The supply circuit 4 further comprises output terminals 7. The motor 2 is connected via a supply line 8 with the output terminals 7 of the supply circuit 4. The supply circuit 4 comprises a smoothing capacitor 10 which is connected in parallel with the input terminals 6. Furthermore, the supply circuit 4 comprises a coil 11 and a capacitor 12 for suppressing interferences. The capacitor 12 provides that a stable direct voltage is presented to an input 14 of a switching means 16. The supply circuit 4 furthermore comprises a control device 18, known per se, which switches the switching means 16 repetitively on and off for obtaining a pulse-width modulated supply voltage on an output terminal 20 of the switching means 16. Thus, on the output terminal 20 of the switching means 16 there is a pulse-width modulated square-wave voltage of, for instance, 12 Volts. The supply circuit 4 is further provided with a flyback diode 22, which is included to offer a current path for the flyback current pulses of the motor, so that no high voltage peaks arise.

The driver device known per se as described up to this point works as follows.

To the input terminals 6, for instance a supply voltage of 12 Volts is applied. The control device 18 opens and closes the switching means 16, for instance with a frequency of 20,000 kHz. In doing so, the control device 18 varies the period during which the switching means 16 is closed. Thus arises a pulse-width modulated supply voltage on the output terminal 20 of the switching means 16. This pulse-width modulated supply voltage is applied to the motor 2 via the output terminals 7 and the supply line 8. As a result, the motor 2 will start to run. The speed at which the motor 2 runs depends on the pulse width modulation. When the width of the pulse increases, the motor will start to rotate faster because then more energy is supplied to the motor 2. Conversely, when the width of the pulse decreases, the motor will start to run more slowly. Because in this example there will be a 12 V square-wave voltage on a motor housing of the motor 2, this will start to radiate. To prevent this, in this example the motor housing has been grounded, and the 12 V square-wave voltage present on the motor winding is also present on a parasitic coupling capacity 24 to earth. This has as a result that large currents will start to flow through the capacitor 24. These large currents have an influence on and cause interferences in the supply circuit 4. For that reason the supply circuit 4 is further provided with a coil 28 to suppress these interferences. When a short circuit occurs in the wiring 10, this has as a consequence that a very large current starts to flow through inter alia the switching means 16, so that this may be damaged. Also, the motor 2 can cause very large currents through the switching means when the motor has just been started. The device may further be provided with a second switching means 30 in the form of a relay for reversing the polarity of the voltage supplied to the motor, enabling the direction of rotation of the motor 2 to be set. Also the second switching means 30 may become damaged for the same reasons as indicated above for the first switching means.

In the device according to Fig. 2 according to the invention, parts corresponding to Fig. 1 have been provided with the same reference numerals. The driver device according to Fig. 2 is further provided with a rectifier circuit 32 which is connected on one side with the supply circuit 4 for obtaining, on the basis of the pulse-width modulated supply voltage on the output terminals 7, a direct voltage on output terminals 34 of the rectifier circuit 32. The motor 2 is connected with the output terminals 34 of the rectifier circuit 32. The direct voltage on the output terminals 34, which direct voltage is applied to the motor, has a magnitude which is dependent on the pulse width of the supply voltage. The motor 2 is thus driven with a direct voltage, while the speed of the motor is dependent on the magnitude of the direct voltage.

In this example, the rectifier circuit 32 is provided with a diode 33, a coil 36 and a capacity in the form of a capacitor 38. The capacitor 38 is connected in parallel with the motor 2. The coil 36 is connected in series with the motor 2. The coil 36 and the capacitor 38 form a low pass filter for smoothing, and rectifying, the pulse-width modulated supply voltage. When the pulse width of the supply voltage signal on the output terminals 7 increases, the magnitude of the direct voltage on the output terminals 34, with which the motor 2 is coupled, will increase. As a result, the motor 2 will start to run faster. Conversely, when the pulse width on the output terminals 7 of the supply circuit 4 decreases, the magnitude of the direct voltage on the output terminals 34 of the rectifier circuit will decrease, so that the motor will start to run slower.

Because presently no alternating voltage is supplied to the motor 2, it cannot start to radiate electromagnetically. This has as a consequence that the capacitor 24 can be omitted. Now that the capacitor 24 has been omitted, the coil 28 in the supply circuit 4 can also be omitted. Further, the flyback diode 22 can be omitted now that the flyback pulses are fed back via the rectifier 32. This is because no interferences need to be suppressed that have been caused by the capacitor 24. Since the alternating voltages and alternating currents occur exclusively in the driver circuit 1 and the rectifier circuit 32 and not on the supply lines 8 of the motor 2 and the motor 2 proper, the drawback that electromagnetic radiation may be emitted is no longer present. This means that the modulation frequency of the signal on the output terminals 7 can be raised to, for instance, 100 kHz. This in turn has as a consequence that components such as coils and capacitors (10, 11, 12) can be chosen to be small. Also, the coil 36 and the capacitor 38 can be chosen to be small, due to the relatively high frequency. The high-frequency portion of the driver device 1, viz. the supply circuit 4 and the rectifier circuit 32, can be provided at one point. The supply line 8 and the motor 2 located outside the point only carry a direct voltage, which strongly limits the emission of radiation.

When a short circuit occurs in, for instance, the supply line 8, so that the terminals 34 are connected with each other, the capacitor 38 will discharge. The result is that in the event of such a short circuit, much smaller currents will start to flow through the switching means 16 than in the event of such a short circuit in the known device according to Fig. 1. Also when the motor 2 has been started, large current peaks through the switching means 16, as well as through any relay 30, will remain absent in that the capacitor 38 can supply the briefly required greater current through the motor 2.

In the event of a complete short circuit, this will presently be obviated in that a fuse of the car's supply circuit that supplies voltage to the input terminals 6, blows.

Further, the capacity 38 has as a result that all peaks in the current supply needed by the motor 2, for instance when starting the motor but also when the panel jams so that the motor 2 is driven, are drawn largely from the capacitor 38 instead of from a battery of the car.

The device according to Fig. 2 can preferably be further provided with a detection device 40, which detects current peaks through the motor 2 in order to detect the jamming of the slidable panel or the fact that the slidable panel is squeezing something or somebody. When the panel 2 jams, the motor 2 will have to provide a greater couple. This has as a result that the current flowing through the motor will increase, which can be detected with the aid of the detection device 40. The detection device 40 can then cut off the current supply to the motor 2 in a known manner, or provide for the inversion of the direction of rotation of the motor 2 with the aid of relay 30 in order to remove the squeezing of something or somebody. The control device 18 here also controls the relay 30, and an output of the detection device 40 is connected with the control device 18. The advantage of the device according to Fig. 2 is that the increase of the (direct) current through the motor can be properly detected. In the device according to Fig. 1, an increase of a modulated current is involved, which can be carried out less accurately.

The invention is not limited in any way to the embodiments outlined hereinbefore. Thus, it is possible to use a rectifier circuit which is provided with more capacitors and/or coils. Also, a different type of supply circuit can be used for generating the pulse-width modulated supply voltage. Figs. 1 and 2 only show diagrammatic embodiments which may be realized differently in practice.

The modulation frequency of the supply voltage can for instance be greater than 15 kHz and preferably be between 80 and 120 kHz. However, higher or lower frequencies are also conceivable. Such variations are each understood to fall within the scope of the invention.