阅读说明：本技术 电磁阀的脉宽调制控制 (Pulse width modulation control of solenoid valve ) 是由 马库斯·法依诺伊尔 西蒙·卡斯特纳 丁可·贝格维奇 塞巴斯蒂安·弗朗克 于 2019-06-11 设计创作，主要内容包括：本发明涉及一种方法和一种开关电路,其用于对电磁阀的电磁驱动装置进行电子控制。开关电路设置用于为电磁驱动装置提供一个控制信号,该控制信号具有一个高电平和一个低电平。控制信号具有至少一个带有第一占空比<Image he="75" wi="398" file="DDA0002090089770000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>的第一时间间隔、带有第二占空比的可选的第二时间间隔和带有第三占空比的第三时间间隔,其中第一、第二和第三占空比小于1并且第一占空比大于第二占空比和第二占空比大于第三占空比。时间间隔的时间长度和占空比的大小构成为：电磁驱动装置在第一时间间隔中从第一运行状态转换到第二运行状态,可选地在第二时间间隔中保持在第二运行状态中并且在第三时间间隔中从第二运行状态转换到第一运行状态。(The invention relates to a method and a switching circuit for electronically controlling an electromagnetic drive of a solenoid valve. The switching circuit is arranged to provide a control signal to the electromagnetic drive means, the control signal having a high level and a low level. The control signal has at least one control signal with a first duty cycle A first time interval with a second duty cycle, an optional second time interval with a second duty cycle and a third time interval with a third duty cycle, wherein the first, second and third duty cycles are smaller than 1 and the first duty cycle is larger than the second duty cycle and the second duty cycleThe duty cycle is greater than the third duty cycle. The time length of the time interval and the size of the duty ratio are: the electromagnetic drive is switched from the first operating state to the second operating state in a first time interval, optionally remains in the second operating state in a second time interval and is switched from the second operating state to the first operating state in a third time interval.)

1. Switching circuit (100) for electronically controlling an electromagnetic drive of a solenoid valve, wherein the switching circuit (100) is provided for supplying a control signal to the electromagnetic drive, the control signal having a high level and a low level, and the control signal having at least one first time interval (IV1) with a first duty cycle (TV1), an optional second time interval (IV2) with a second duty cycle (TV2), and a third time interval (IV3) with a third duty cycle (TV3), wherein the first, second, and third duty cycles (TV1, TV2, TV3) are smaller than 1 and the first duty cycle (TV1) is larger than the second duty cycle (TV2) and the second duty cycle (TV2) is larger than the third duty cycle (TV3), and the time length of the time intervals and the size of the duty cycles are configured such that: the electromagnetic drive is switched from the first operating state to the second operating state in a first time interval (IV1), optionally remains in the second operating state in a second time interval (IV2) and is switched from the second operating state to the first operating state in a third time interval (IV 3).

2. The switching circuit (100) of claim 1, wherein the switching circuit is arranged for providing the control signal in dependence on a relation, in particular a logical and relation, of the first pulse width modulated (PWM-) signal (PWM1) and the second pulse width modulated (PWM-) signal (PWM 2).

3. The switching circuit (100) as claimed in claim 2, wherein the first pulse width modulated signal (PWM1) is provided for providing a first time interval (IV1) with a first duty cycle (TV1) and in particular for providing a second time interval (IV2) with a second duty cycle (TV 2).

4. The switching circuit (100) according to claim 2 or 3, wherein the second pulse width modulated signal (PWM2) is arranged to provide a third time interval (IV3) with a third duty cycle (TV 3).

5. The switching circuit (100) of any one of claims 2 to 4, wherein the switching circuit comprises an AND gate (150) arranged to combine the first pulse width modulated signal (PWM1) and the second pulse width modulated signal (PWM2) into the control signal according to a logical AND relationship.

6. The switching circuit (100) of claim 5, wherein the switching circuit comprises a transistor (160) coupled to the electromagnetic drive and receiving a control signal from an AND gate (150) for controlling the electromagnetic drive with the control signal.

7. The switching circuit (100) according to any one of claims 2 to 6, wherein the switching circuit comprises a signal processing unit (140), in particular a microprocessor, which is arranged for providing the first pulse width modulated signal (PWM 1).

8. The switching circuit (100) of claim 7, wherein the signal processing unit comprises a first and/or a second discrete circuit arranged for providing the first and/or the second pulse width modulated signal (PWM1, 2).

9. The switching circuit (100) of claim 8, wherein the switching circuit is arranged to detect a supply level of a supply Voltage (VS) of the electromagnetic drive and to adjust one, more or all duty cycles (TV1, TV2, TV3) of the control signal based on the detected supply level.

10. The switching circuit (100) of claim 1, wherein the switching circuit is located in a position adjuster or a positioning device.

11. Method for controlling an electromagnetic drive for a solenoid valve, comprising: providing a control signal for operating an electromagnetic drive, wherein the control signal has a first time interval (IV1), an optional second time interval (IV2) and a third time interval (IV3) which are directly consecutive in time to one another, wherein the first time interval (IV1) has a first duty cycle (TV1), the optional second time interval (IV2) has a second duty cycle (TV2) and the third time interval (IV3) has a third duty cycle (TV3), wherein the duty cycles in the first, second and third time intervals (IV1, IV2, IV3) are smaller than 1, and the first duty cycle (TV1) is larger than the second duty cycle (TV2) and the second duty cycle (TV2) is larger than the third duty cycle (TV3), and the method further comprises: adjusting the first time interval (IV1) and the first duty cycle (TV1) in such a way that the electromagnetic drive is switched from the first operating state to the second operating state; optionally adjusting the second time interval (IV2) and the second duty cycle (TV2) such that the electromagnetic drive remains in the second operating state; and the third time interval (IV3) and the third duty cycle (TV3) are set in such a way that the electromagnetic drive is switched from the second operating state to the first operating state.

12. The method of claim 11, wherein the third time interval (IV3) has a duty cycle of zero.

13. A method according to claim 11 or 12, wherein the first operating state of the electromagnetic drive is a closed operating state of the solenoid valve and the second operating state is an open operating state of the solenoid valve.

14. The method according to any one of claims 11 to 13, comprising: the supply level of the electromagnetic drive is detected and the first duty cycle (TV1) and/or the second duty cycle (TV2) is adjusted based on the detected supply level (VS).

Technical Field

The invention relates to a switching circuit and a method for controlling an electromagnetic drive of a solenoid valve, in particular for controlling with a pulse width modulation signal.

Background

Solenoid valves with electromagnetic drives are used in many ways. This has, for example, a pilot-operated solenoid valve which is used in the control pushbutton (Steuerkopf) and supplies a certain pressure to the input of the main valve. Pilot-operated solenoid valves, for example, can control the air required to open and close a process control valve (Prozessventil). The electromagnetic drive of the solenoid valve typically comprises an armature and a coil, which is controlled, for example, by means of a pulse-width-modulated control signal.

Disclosure of Invention

The object of the invention is to improve the control of a solenoid valve with an electromagnetic drive in view of power consumption and complexity compared to the prior art.

According to one aspect, a switching circuit is provided for electronically controlling an electromagnetic drive of a solenoid valve (a solenoid valve is also provided). The switching circuit is arranged to provide the electromagnetic drive with a control signal having a high level (on-level) and a low level (off-level) or alternating between a high level and a low level. The control signal has at least one first time interval with a first duty cycle, an optional second time interval with a second duty cycle and a third time interval with a third duty cycle.

In the present case, the duty cycle is the ratio of the on-time (AN-Zeit) (the duration or time span of the signal at high level) to the sum of the off-time (AUS-Zeit) (the duration or time span of the signal at low level) and the on-time. The sum of the on-time and the off-time may correspond to the period or fundamental frequency of the control signal, as is common in pulse modulated signals (PWM signals), for example. The first time interval, as an alternative the second time interval and the third time interval are advantageously temporally successive, particularly advantageously directly successive, with one another. Further, the first, second and third duty cycles are less than 1. In other words, the signal transitions from a high level to a low level or remains completely zero at least once during the time interval. The first duty cycle is greater than the second duty cycle and the second duty cycle is greater than the third duty cycle. The duration of the time interval and the size of the duty cycle are advantageously configured such that: the electromagnetic drive is switched from the first operating state to the second operating state in a first time interval, remains in the second operating state in a selectable second time interval and is switched from the second operating state to the first operating state in a third time interval. From the above viewpoint, many advantages can be achieved. The supply level can first be adjusted by selecting the duty cycle, which is in the form of an average or time-averaged level for the electromagnetic drive. When the electromagnetic drive is in the second operating state, the energy consumption or the power consumption of the electromagnetic drive can be reduced, and the solenoid valve can be switched in a targeted manner between the first and the second operating state without additional intermediate states having to be provided between the operating states.

The control signal may advantageously be a relation of pulse width modulated signals (PWM signals), particularly advantageously a relation of two pulse width modulated signals. The relationship may advantageously be a logical and relationship. The control signal may accordingly comprise first and second signal portions. The first and second signal portions may be provided by a first pulse width modulated signal and a second pulse width modulated signal, respectively, which are combined accordingly.

The first pulse width modulated signal may have a first fundamental frequency and the second pulse width modulated signal may have a second fundamental frequency. The first fundamental frequency may advantageously be greater than the second fundamental frequency. The first fundamental frequency and the first duty cycle can advantageously be so large that the electromagnetic drive can be switched from the first operating state into the second operating state. The first fundamental frequency and the second duty cycle can advantageously be so large that the electromagnetic drive can be kept in the second operating state.

The first fundamental frequency may also be, for example, a multiple of a positive integer of the second fundamental frequency.

The second pulse width modulated signal may also be set independently of the ratio of the first fundamental frequency to the second fundamental frequency as: the off-time(s) of at least the second pulse width modulated signal are longer than the off-time(s) of the first pulse width modulated signal. Not only the on-time(s), but also the off-time(s) of the second pulse width modulated signal can be advantageously longer than the on-time(s) and the off-time(s) of the first pulse width modulated signal.

The first pulse width modulated signal may be arranged for providing a first time interval with a first duty cycle and for providing an optional second time interval with a second duty cycle.

The second pulse width modulated signal may be arranged to provide a third time interval with a third duty cycle. The second pulse width modulated signal may be an adjustment amount for the solenoid valve.

The second pulse width modulation signal may be set to: the solenoid valve is always fully opened and fully closed and thus a certain target position of the solenoid valve is adjusted in average time.

The third duty cycle may advantageously be zero. The second time interval may advantageously be mandatory, i.e. not optionally.

The switching circuit may be provided for combining and combining the first pulse width modulated signal and the second pulse width modulated signal into a single or the control signal depending on or by means of a relationship, in particular a logical relationship and in particular a logical and relationship. The following applies here, in accordance with the principle of the relationship: the level of the control signal for the electromagnetic drive is at a high level (on level) only if both the first pulse width modulated signal and the second pulse width modulated signal are at a high level.

In one design, the switching circuit can accordingly comprise an and gate or a circuit or a plurality of gate circuits with equal functionality. The and gate or equivalent circuit may then take the first and second pulse width modulated signals and logically and them.

In addition, the switching circuit may further include a transistor coupled to the electromagnetic drive. The output of the and gate or of the equivalent circuit can then be output, for example, to a transistor, which is coupled to the electromagnetic drive in such a way that the electromagnetic drive is controlled by the output signal or by a control signal via the transistor.

The switching circuit may comprise a microprocessor. The first pulse width modulated signal or the second pulse width modulated signal may be provided by a microprocessor. The first or second pulse width modulated signal may also be provided by a separate circuit.

The switching circuit can be designed to detect a supply level of a supply voltage of the electromagnetic drive. In particular, the switching circuit may be configured to adjust one, more or all duty cycles of the control signal in dependence on this supply level. For this purpose, the switching circuit may comprise, for example, an analog-digital converter which is coupled to the supply voltage for detecting the supply voltage level and outputs digital data to the microprocessor in order to adjust one or more duty cycles, in particular the first and/or second duty cycles.

The switching circuit may be located in a position regulator or positioning device (positioner).

The positioning device or the position regulator may be arranged on or in the solenoid valve.

A method for controlling an electromagnetic drive of a solenoid valve is also provided. Accordingly, a control signal for operating the electromagnetic drive is provided, wherein the control signal has a first time interval, optionally a second time interval and a third time interval, which are advantageously directly consecutive in time to one another. The first time interval has a first duty cycle, the second time interval has a second duty cycle and the third time interval has a third duty cycle, wherein the duty cycles in the first, second and third time intervals are less than 1, and the first duty cycle is greater than the second duty cycle and the second duty cycle is greater than the third duty cycle.

The first time interval and the first duty cycle can be set such that the electromagnetic drive switches from the first operating state to the second operating state. The selectable second time interval and the second duty cycle can be set in such a way that the solenoid drive or the solenoid valve remains in the second operating state. The third time interval and the third duty cycle can be set such that the electromagnetic drive or the solenoid valve is switched from the second operating state to the first operating state.

The third duty cycle may be zero. In other words, the control signal may be turned off and maintained or continuously have a low level in the third interval.

The first operating state of the electromagnetic drive may be a closed operating state of the solenoid valve and the second operating state may be an open operating state of the solenoid valve. In another embodiment, this can also be reversed. Advantageously, however, the first and second operating states relate to a complete opening or a complete closing of the valve.

According to a further aspect, the supply level of the electromagnetic drive may be detected and the first duty cycle and/or the second duty cycle may be adjusted based on the detected supply level. In this way, the necessary, time-averaged voltage at the electromagnetic drive can always be ensured.

Drawings

Further advantageous aspects and features of the invention are explained with the aid of the following description of an embodiment with reference to the drawings, in which:

FIG. 1 is a simplified schematic voltage-time diagram including three pulse width modulated signals, an

FIG. 2 is a simplified schematic voltage-time diagram including three pulse width modulated signals having temporally different duty cycles of the respective signals, an

Fig. 3 is a simplified schematic circuit diagram of a switching circuit for providing control signals for an electromagnetic drive of a solenoid valve.

Detailed Description

Fig. 1 shows a simplified schematic voltage-time diagram comprising a first, a second and a third pulse width modulated Signal (PWM-Signal) PWM1, PWM2, PWM 3. The third pulse width modulation signal PWM3 is used as a control signal for controlling the electromagnetic drive of the solenoid valve in the first embodiment. The electromagnetic drive includes an electromagnetic coil that operates based on a control signal. The first pulse width modulation signal PWM1 is used as an operating parameter including supply voltage adaptation, and the second pulse width modulation signal PWM2 is used as a regulating variable for the electromagnetic drive. The third pulse width modulated signal PWM3 is a combination of the first pulse width modulated signal PWM1 and the second pulse width modulated signal PWM2 generated according to the principle of the and relation. The following applies here: the level of the third pulse width modulation signal PWM3 or the level of the control signal for the electromagnetic drive device is at a high level (on level) only when not only the first pulse width modulation signal PWM1 but also the second pulse width modulation signal PWM2 are at a high level at the same time. The control signal or third pulse width modulated signal PWM3 includes all the advantageous characteristics of the first and second pulse width modulated signals PWM1 and PWM 2.

In the voltage-time diagram, time is plotted on the abscissa and voltage is plotted on the ordinate. The uppermost signal constitutes the first pulse width modulated signal PWM 1. The time span between the time points T0PWM1 and T1PWM1 is the period time T1 of the first pulse width modulation signal PWM 1. The period time T1 includes one complete period, i.e., the sum of the on time and the off time. The reciprocal of the cycle time T1 is the fundamental frequency F1. The on-time T1EIN corresponds to the time span between time T0PWM1 and T01PWM1, and the off-time T1AUS corresponds to the time span between time T01PWM1 and T1PWM 1. During the on-time T1EIN, the pulse width modulated signal PWM1 is High, that is, the amplitude or level is High (High). During the off-time T1AUS, the pulse width modulated signal PWM1 is Low, that is, the amplitude or level is Low (Low). The ratio of the on-time T1EIN to the period time T1 corresponds to the first duty cycle TV 1. According to the present embodiment, the TV1 is for example 50% in the case of the first pulse width modulated signal PWM 1. The first pulse width modulation signal PWM1 acts on a suitable, time-averaged supply voltage for the solenoid coil.

The supply voltage of the solenoid coil can either be different as a result of the nominal supply voltage of the supply device or can be subject to fluctuations during operation of the solenoid valve. Via the first duty cycle TV1, the voltage of the power supply can be matched to the voltage required at the solenoid coil. For example, with a 50% duty cycle, the initial input voltage of 24V can be reduced to an effective (time-averaged) input voltage of 12V, which is applied to the solenoid coil. The current through the coil decreases as the effective voltage Ueff over the electromagnetic coil decreases. A reduction in the effective applied voltage Ueff and a concomitant reduction in the strength of the applied current leads in particular to a reduction in the electrical power to be applied to operate the coil (reduction in the power loss). The first duty cycle TV1 is always less than 1 and therefore has a finite off-time T1 AUS.

The first fundamental frequency F1 of the first pulse width modulated signal PWM1 is obtained from the inverse of the period time T1. The first duty cycle TV1 is selected such that sufficient power is available for the electromagnetic drive to switch from the first operating state to the second operating state. In the present case, this is the change in position of the armature of the electromagnetic drive from the non-attracted position into the attracted position. If the armature is in the attracted position, for example, a process fluid flow (gas flow) can be provided. The solenoid valve can be in an open operating state. The electromagnetic drive is then in the second operating state.

The second pulse width modulated signal PWM2 constitutes the regulating variable of the electromagnetic drive. The adjustment determines the position of the armature and thus whether process fluid flow is provided. The second pulse width modulated signal PWM2 may in principle have a longer period time T2 than the first pulse width modulated signal PWM1 and thus a lower fundamental frequency F2 than the first pulse width modulated signal PWM 1.

The second pulse width modulation signal PWM2 can also be determined independently of the ratio of the fundamental frequencies F1 and F2 in such a way that at least the off-time(s) of the second pulse width modulation signal PWM2 is/are longer than the off-time(s) of the first pulse width modulation signal PWM 1. In addition, not only the on-time(s) T2EIN, but also the off-time(s) T2AUS can be longer than the on-time(s) and the off-time(s) of the first pulse width modulation signal PWM 1. The second fundamental frequency F2 and the duty cycle or the on-time T2EIN and the off-time T2AUS of the second pulse-width modulated signal PWM2 are selected as: the armature can be switched from an unabsorbed position into an absorbed position during the on time T2EIN and, if necessary, remains in the absorbed position, and can be switched back into the unabsorbed position during the sufficiently long off time T2 AUS. In the non-attracted position of the armature, the solenoid valve is in the closed operating state. The electromagnetic drive is in this case in the first operating state. Since the off-time T2AUS of the second pulse-width modulation signal PWM2 required for the armature to switch into the non-attracted position is relatively long, the second fundamental frequency F2 can be smaller than the first fundamental frequency F1 of the first pulse-width modulation signal PWM 1. The duty cycle of the second pulse width modulated signal PWM2 may always be less than 1. In principle, the off-time T2AUS is selected as: the solenoid valve can be switched from the second operating state (for example open) into the first operating state (closed). Furthermore, the on-time T2EIN is selected as: the solenoid valve can be switched from a first operating state (e.g., closed) into a second operating state (e.g., open) and can also be held in this second operating state if necessary.

The third pulse-width modulation signal PWM3 is a control signal for the electromagnetic drive and is formed by a combination of the logical and relationship of the first pulse-width modulation signal PWM1 as the first signal portion S1 and the second pulse-width modulation signal PWM2 as the second signal portion S2. The third pulse width modulated signal PWM3 comprises at least two associated time intervals, wherein these time intervals are referred to for consistency reasons as the first time interval IV1 and the third time interval IV 3. The first time interval IV1 accordingly possesses a first duty cycle TV1, while the third time interval IV3 possesses a third duty cycle TV 3.

The third pulse width modulated signal PWM3 has a third fundamental frequency F3, which coincides with the first fundamental frequency F1. The duty cycle may vary over time in the third pulse width modulated signal PWM 3.

In the first time interval IV1, the duty cycle corresponds to the first duty cycle. In a third time interval IV3, there is no on-time and the third duty cycle TV3 has a value of zero. The duration of the third time interval IV3 corresponds to or is determined by the off-time T2AUS of the second pulse-width-modulated signal PWM 2.

A voltage is applied to the solenoid coil during the on time T3EIN of the third pulse width modulation signal PWM3, while no voltage is present on the solenoid coil during the off times T3AUS1, T3AUS 2.

In a first time interval IV1, the electromagnetic drive is switched from the first operating state to the second operating state and remains in the second operating state. For example, a process fluid flow (gas flow) is thus provided and the solenoid valve is in the open operating state. In a third time interval IV3, the electromagnetic drive is switched from the second operating state to the first operating state and remains in the first operating state. The solenoid valve is thus closed. The off-time T3AUS2 of the third pulse width modulated signal PWM3 is long enough to ensure that the electromagnetic drive is able to switch from the second operating state to the first operating state.

Fig. 2 shows a simplified schematic voltage-time diagram comprising the first, second and third pulse width modulated signals PWM1, PWM2, PWM3 of the second embodiment.

In the first pulse width modulated signal PWM1, the duty cycle changes during the signal from an initial first duty cycle TV11 of, for example, 50%, to a changed duty cycle TV12 of 20%. By the duty cycle being reduced during the signal, the effective (time-averaged) voltage applied to the solenoid is reduced, whereby the current through the coil is reduced. The power loss can be reduced. After the armature has been switched from the non-attracted position into the attracted position, the duty cycle is reduced such that the power is sufficient to hold the armature in the attracted position. This corresponds to a second operating state of the electromagnetic drive, in which the solenoid valve is in the open operating state. In order to hold the armature in the attracted position, less power is required than for placing the armature from the non-attracted position into the attracted position.

The third pulse width modulated signal PWM3 here also forms the control signal and comprises three time intervals in the signal sequence with additional power reduction, namely a first time interval IV1 with a first duty cycle TV1, a second time interval IV2 with a second duty cycle TV2 and a third time interval IV3 with a third duty cycle TV 3.

The control signal or the third pulse width modulated signal PWM3 has a third fundamental frequency F3, which coincides with the first fundamental frequency F1. The first, second and third duty cycles of the pulse width modulated signal PWM3 take three values TV1, TV2 and TV 3. In the first time interval IV1, the first duty cycle TV1 of the pulse-width modulated signal PWM3 coincides with the initial duty cycle TV11 of the first pulse-width modulated signal PWM1 before the power reduction. The fundamental frequency F3 and the duty cycle TV1 are high enough to put the armature from the first position into the second position. The electromagnetic drive is thus switched from the first operating state to the second operating state and remains in the second operating state. The solenoid valve opens.

In a second time interval IV2, the second duty cycle TV2 of the pulse width modulated signal PWM3 coincides with the reduced duty cycle TV12 of the first pulse width modulated signal PWM1 after the power reduction. The fundamental frequency F3 and the second duty cycle TV2 are high enough to hold the armature in the second or attracted position. The electromagnetic drive is therefore maintained in the second operating state. The solenoid valve remains open.

The third time interval IV3 has no on-time and therefore has a duty cycle of zero. In a third time interval IV3, the electromagnetic drive is switched back from the second operating state to the first operating state. The solenoid valve closes. The duty cycle decreases from the first time interval towards the third time interval (TV1 > TV2 > TV3) and is always less than 1(TV1, TV2, TV3 < 1).

Fig. 3 shows a simplified schematic circuit diagram of an electronic circuit or switching circuit 100 of an electromagnetic drive for a solenoid valve (not shown). Only the solenoid 110 of the solenoid drive of the valve is shown in a simplified manner. The switching circuit is located in a position adjuster or positioning device 170. The position adjuster 170 may be housed in a housing along with one or more solenoid valves. The position regulator can be mounted on the side of the electromagnetic drive or on the drive. Solenoid 110-depending on the applied current-moves an armature (not shown) to open and close the solenoid valve. Solenoid coil 110 is coupled to a power supply 120. In order to determine the voltage VS of the power supply 120, the latter is coupled via a voltage divider 131, 130 to an electronic signal processing unit 140, for example a microprocessor. The actual value VS of the supply voltage is supplied as an analog signal to a signal processing unit 140 or microprocessor, for example, also as a discrete circuit, and is converted into a digital signal, for example, in an integrated analog-digital converter 141. The signal processing unit or microprocessor 140 provides a first pulse width modulated signal PWM1 on the first output 142 depending on the measured actual value VS of the voltage. The first duty cycle TV1 of the first pulse-width modulation signal PWM1 and/or the second duty cycle TV2 of the first pulse-width modulation signal PWM1 are determined by the signal processing unit or microprocessor 140 for the active level to be applied to the solenoid 110 by means of the measured voltage VS. The signal processing unit or microprocessor 140 furthermore provides a second pulse width modulated signal PWM2 at a second output 143. The second pulse width modulated signal PWM2 constitutes the regulating variable of the electromagnetic drive. Here, the second pulse width modulation signal PWM2 may be determined based on an external signal externally supplied to the signal processing unit or the microprocessor 140.

In one embodiment, the first and/or second pulse width modulation signals PWM1, PWM2 may also be provided by separate circuits.

Two output terminals 142, 143 of the signal processing unit or microprocessor 140 are connected to first and second input terminals 151, 152 of an and gate 150. The and gate 150 may be, for example, an integrated circuit. The first pulse width modulated signal PWM1 is correlated with the second pulse width modulated signal PWM2 via a logical and in the and gate 150. The output 153 of the and gate 150 provides the third pulse width modulated signal PWM 3. The third pulse width modulation signal PWM3 is a control signal for the electromagnetic drive of the valve or for the electromagnetic coil 110 of the electromagnetic drive. The output 153 of the and gate 150 is coupled to a transistor 160 or to a transistor 160. The transistor 160 is coupled to the solenoid 110. In the present case, the transistor channel is coupled between the electromagnetic coil 110 and ground. If the transistor is switched on, a current can flow through the solenoid 110 and the electric drive of the solenoid valve can change the operating state. In the present example, transistor 160 is an NPN bipolar transistor coupled to the coil with a collector and to ground with an emitter. Of course other transistor types are also contemplated. The current through electromagnetic coil 110 is controlled in this manner by switching transistor 160 on and off via third pulse width modulated signal PWM 3. The following is thereby achieved: in view of the current level of the supply voltage, the power reduction and the position of the valve, solenoid coil 110 is advantageously controlled by means of a control signal or pulse width modulation signal PWM 3.