DEVICE FOR OPERATING AN ELECTRICAL CONSUMER, CONSUMER AND METHOD

Abstract

A device for operating an electrical consumer, in particular a solenoid valve, including at least one first circuit which encompasses an activatable first switch and a first freewheeling unit connected or connectable in parallel to the consumer, and including a control unit which is designed for activating the first switch in order to energize the consumer with a predefinable electric current with the aid of pulse width modulation. It is provided that the circuit encompasses at least one second switch and one second freewheeling unit, which is connected or connectable in parallel to the consumer, and that the control unit is designed for activating the second switch in a phase-shifted manner with respect to the first switch in order to energize the consumer.

Claims

1. A device for operating an electrical consumer, comprising: at least one first circuit which encompasses an activatable first switch and a first freewheeling unit connected or connectable in parallel to the consumer; and a control unit configured to for activate the first switch to energize the consumer with a predefinable electric current using pulse width modulation, wherein the first circuit includes at least one second switch and one second freewheeling unit, which is connected or connectable in parallel to the consumer, and wherein at the control unit is configured to activate the second switch, in a phase-offset manner with respect to the first switch, to energize the consumer.

2. The device as recited in claim 1, wherein the electrical consumer is a solenoid valve.

3. The device as recited in claim 1, wherein a diode is connected in series between the consumer and each of the first switch and the second switch.

4. The device as recited in claim 1, wherein the first freewheeling units and the second freewheeling unit each include an active freewheeling diode, respectively, of a MOSFET.

5. The device as recited in claim 1, wherein each of the first freewheeling unit and the second freewheeling unit is a passive freewheeling diode.

6. An electrical consumer, comprising: an electrical solenoid valve for a motor vehicle; and a device for operating an electrical solenoid valve, the device including: at least one first circuit which encompasses an activatable first switch and a first freewheeling unit connected or connectable in parallel to the electrical solenoid valve; and a control unit configured to for activate the first switch to energize the electrical solenoid valve with a predefinable electric current using pulse width modulation, wherein the first circuit includes at least one second switch and one second freewheeling unit, which is connected or connectable in parallel to the electrical solenoid valve, and wherein at the control unit is configured to activate the second switch, in a phase-offset manner with respect to the first switch, to energize the electrical solenoid valve.

7. The electrical consumer as recited in claim 6, wherein the electrical solenoid valve is a hydraulic valve.

8. A method for operating a device including at least one first circuit which encompasses an activatable first switch and a first freewheeling unit connected or connectable in parallel to the consumer, and a control unit configured to for activate the first switch to energize the consumer with a predefinable electric current using pulse width modulation, wherein the first circuit includes at least one second switch and one second freewheeling unit, which is connected or connectable in parallel to the consumer, and wherein at the control unit is configured to activate the second switch, in a phase-offset manner with respect to the first switch, to energize the consumer, the method comprising: activating the first switch and the second switch in a phase-shifted manner with respect to one another.

9. The method as recited in claim 8, wherein, at a beginning of an energizing process of the consumer, the first switch and the second switch are activated simultaneously and, as a time period increases, are activated in a manner offset with respect to one another in the phase.

10. The method as recited in claim 8, wherein the first switch and the second switch are activated at a different frequency to achieve the offset phase.

11. The method as recited in claim 8, wherein the first switch and the second switch are operated further at a same frequency upon reaching a phase shift of 180.

12. The method as recited in claim 8, wherein the first freewheeling unit and the second freewheeling unit connected in parallel are actively switched.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 shows a simplified representation of a device for operating an electrical consumer according to one exemplary embodiment.

[0018] FIG. 2 shows the switching states in a diagram.

[0019] FIG. 3 shows the device according to one further exemplary embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0020] FIG. 1 shows, in a simplified representation, a device 1 for operating an electrical consumer 2. In this case, the electrical consumer is a coil 3 of a solenoid valve (not represented here in greater detail), which is energizable in order to actuate the solenoid valve. Device 1 encompasses an application-specific circuit 4 (ASIC) which is activated with the aid of a control unit 5, which may also be a component of the ASIC or circuit 4, in order to actuate the solenoid valve or consumer 2.

[0021] Circuit 4 encompasses a first switch 6 and a second switch 7 which are actuatable with the aid of control unit 5 in order to connect consumer 2 to a DC voltage source U. Switches 6, 7 are connected in parallel to one another and in series to consumer 2. Optionally, a diode 8 or 9, for example, as a decoupling diode, is also connected in series between particular switch 6, 7, respectively, and the load or consumer 2. The diode ensures that a short circuit does not arise when one of the switches 6, 7 is closed and the other switch is open.

[0022] Moreover, circuit 4 encompasses a first freewheeling unit 10 and a second freewheeling unit 11, each of which is connected in parallel to consumer 2 or to the load of consumer 2. In this case, freewheeling unit 10 is connected between first switch 6 and first diode 8, and freewheeling unit 11 is connected between second switch 7 and second diode 9. According to the present exemplary embodiment, freewheeling units 10, 11 are designed as passive freewheeling diodes.

[0023] Therefore, circuit 4 encompasses two channels, via which consumer 3 is energizable. Switches 6, 7 may be actuated independently of one another with the aid of control unit 5.

[0024] In this case, control unit 5 is designed for activating switches 6, 7 in a phase-shifted manner with respect to one another in such a way that consumer 2 is uniformly energized at a high frequency. For this purpose, switches 6, 7 are operated at the same frequency, for example, 10 kHz, although with a phase shift of 180, as is to be explained in greater detail with reference to FIG. 2. In particular, switches 6, 7 are activated with a pulse width ratio reduced by 50%.

[0025] FIG. 2 shows, plotted in a diagram with respect to time t, switching states S6 and S7 of switches 6, 7 (1=on, 0=off), frequencies f.sub.1 and f.sub.2 at which switches 6, 7 are operated, as well as output current i of overall device 1, which benefits consumer 2.

[0026] Due to the fact that switches 6, 7 are jointly activated by control unit 5, the sampling frequencies of switches 6, 7 may be synchronized with one another. The desired phase shift is preferably achieved, in this case, due to the fact that the two switches 6, 7 start up synchronously at the beginning of the current build-up in the electrical load, but are operated for a short time at different frequencies as shown in FIG. 2, so that the phase shift continuously becomes greater. At point in time t.sub.1, at which the phase shift has reached 180, the two switches are operated further at the same frequency f.sub.1. Switching time t.sub.1 is preferably calculated according to the following relationship:

[00001]$t=\frac{1}{2}*\frac{1}{f_2-f_{2,\mathrm{start}}}$

where f.sub.1 is the frequency of switch 6 and f.sub.2,start is the initial frequency of switch 7, the following applying at the beginning: f.sub.2,start<f.sub.1. Frequency f.sub.2 is increased to frequency f.sub.1 at point in time t.sub.1.

[0027] As a result, consumer 2 is uniformly energized at point in time t.sub.1 and, in particular, noise development of circuit 4 is avoided.

[0028] While, according to the exemplary embodiment of FIG. 1, freewheeling units 10, 11 are designed as passive diodes 12, 13, it is provided according to a further exemplary embodiment that freewheeling units 10, 11 are designed as active freewheeling diodes 14, 15.

[0029] For this purpose, FIG. 3 shows, by way of example, device 1 which encompasses MOSFET switches 16, 17 instead of freewheeling diodes 12, 13, which are activated with the aid of control unit 5 and each include one of the freewheeling diodes 14, 15, respectively. The advantage of active freewheeling diodes 14, 15 is that the power loss of device 1 is reduced with respect to the preceding exemplary embodiment because, in the case of MOSFETs 16, 17, the voltage drop across freewheeling diodes 14, 15 is considerably less due to a low on-resistance. Diodes 8, 9 are preferably present in this case.

[0030] Due to advantageous device 1, it is made possible to double the maximum frequency of the pulse width modulation by providing second switch 7 and second freewheeling unit 11. As a result, it is possible, without a great amount of additional effort, to remove the actuating frequency and the associated vibrations from the range that is audible for a person.