Ultrasonic generator with variable pwm independent of supply voltage

Abstract

The present disclosure relates to an ultrasonic generator with variable PWM independent of the supply voltage, having a switching unit with an input for a supply voltage and an output for a switching voltage, a coupling element connected to the output, having a coupling output for a transducer voltage, a transducer for generating ultrasonic waves at a transmission power, a series circuit consisting of the input, the output and the switching element, wherein a control unit controls the switching element with a PWM signal having a pulse duty cycle, which is selected in dependence on a parameter related to the transmission power, such that the transmission power corresponds to a predetermined transmission rating independently of the value of the supply voltage. The ultrasonic boundary sensor and the ultrasonic reflection sensor have the ultrasonic generator. In a method for operating the ultrasonic generator, a transmission rating is set and the pulse duty cycle is selected on the basis of the parameter such that the transmission power corresponds to the transmission rating independently of the value of the supply voltage.

Description

Technical Field

[0001] The present invention relates to ultrasonic sensors, particularly ultrasonic transmitters thereof, and especially ultrasonic generators thereof. Background Technology

[0002] Ultrasonic sensors are known in practice and can be used in various ways. Therefore, a dual-material sensor is known, for example, from the product UDC-30GM-085-3E3 by the manufacturer Pepperl+Fuchs and the related datasheet "Pepperl+Fuchs, Dual Material Sensor UDC-30GM-085-3E3, 2020.05.19". This sensor is suitable for supply voltages between 18V and 30V.

[0003] Figure 1 A highly schematic circuit block diagram illustrates the principle structure of a sensor or a portion thereof, namely, an ultrasonic generator 2 according to the prior art, which is used to generate ultrasonic waves 4 in the form of ultrasonic signals from a supply voltage UV.

[0004] During sensor operation, the supply voltage UV is applied to input terminal 6, which, according to the manufacturer's specifications, should be between 18V and 30V in this example. In this example, the sensor operates at a constant 20V. Through the linear power supply 500, which is here an integrated linear voltage in-phase regulator, each permissible supply voltage UV between 18V and 30V is regulated to the same internal supply voltage UI, here 15V. Therefore, along with the internal supply voltage UI, a constant voltage exists for the following emitter stage:

[0005] The control unit 34, or computing unit, here a microcontroller, operates the switching element 32, here a semiconductor power switch, using a PWM signal 35 (PWM: Pulse Width Modulation). The PWM signal 35 has a 50% / 50% pulse duty cycle PP. That is, the period of the PWM signal 35 has an on-time Ton that is 50% of the period duration T and an off-time that is also 50% of the period duration T. The PWM signal 35 is therefore a control signal used to control the switching element 32 with a always fixed duty cycle of 50 / 50, regardless of which supply voltage UV between 18V and 30V is actually present at the input terminal 6.

[0006] The switching element 32 is connected in series with the transformer 14 or its primary terminal 20. A switching voltage US is applied to this series connection, and this switching voltage is generated based on the PWM signal 35 and the pulse voltage of the switching element 32 as a 0V / UI pulse. The transformer 14 converts the switching voltage US applied to the primary terminal 20 into a transducer voltage UW at its secondary terminal 22. The transducer 24, here a piezoelectric transducer, connected to the secondary terminal 22, operates at this transducer voltage UW. It generates and emits ultrasonic waves 4 or ultrasonic signals from the transducer voltage UW. Summary of the Invention

[0007] The objective of this invention is to propose improvements to this ultrasonic sensor.

[0008] This task is accomplished using an ultrasonic generator. Preferred or advantageous embodiments of the invention, as well as other categories of invention, are derived from the other claims, the following description, and the accompanying drawings.

[0009] This ultrasonic generator has an input terminal for the supply voltage. Therefore, during operation, a non-zero supply voltage is applied to the input terminal. The following interpretations concerning voltage, power, etc., should always be understood as assuming the ultrasonic generator is operating normally, i.e., that a voltage, current, etc., of a specified or permissible magnitude exists. The ultrasonic generator is therefore designed or configured to supply a DC voltage. This input terminal has two poles or contacts, terminals, etc., between which the supply voltage exists.

[0010] The ultrasonic generator includes a switching unit. This switching unit has an input terminal and an output terminal. Corresponding to the input terminal, the output terminal also has two poles, but it can also have multiple poles, especially three poles (e.g., push-pull operation, see below). The switching unit is configured to generate a switching voltage at the output terminal from the supply voltage at the input terminal. This switching voltage is a pulsed DC voltage, that is, a sequence of DC voltage pulses between the two poles of the output terminal, as will be further explained below.

[0011] The ultrasonic generator includes a coupling element. This coupling element has a coupling input terminal, which is connected one-to-one with an output terminal, or particularly two or more, especially three, poles. The coupling element also has a two-pole coupling output terminal. The coupling element is configured to map a switching voltage applied to the coupling input terminal to a transducer voltage applied to the coupling output terminal. In particular, the coupling element is a simple direct electrical connection: therefore, one pole of the coupling output terminal is directly electrically connected to one pole of the coupling input terminal. Therefore, the coupling element can be particularly degenerated into an infinitesimally small or "zero-position" element, thus the coupling output terminal can be said to be the output terminal of the switching unit, and the coupling unit can be considered to be eliminated.

[0012] This ultrasonic generator includes a transducer. The transducer has two input terminals, each connected one-to-one to a coupling output terminal. The transducer also has an output terminal. The transducer is configured to generate ultrasonic waves or ultrasonic signals from the transducer voltage at the input terminal and transmit them there. Therefore, the output terminal is the emission region of the ultrasonic transducer. During operation, the generated ultrasonic waves have a specific magnitude of emission power.

[0013] This switching unit comprises a circuit. The circuit includes, or is constituted by, an input terminal, an output terminal, and a series arrangement of switching elements. A "series arrangement" refers to electrical components connected in a row of wires, i.e., connected one after another. In this arrangement, the connection between adjacent individual components can also be designed as multi-wire or multi-pole, particularly two-pole. This is especially suitable for two-pole or two-wire connections between the output terminal and the switching element. The switching element may comprise one or more, particularly two, independent switches connected in parallel. The switching unit also includes a control unit that acts on or controls the switching element during operation.

[0014] This control unit is configured to control the switching element with a PWM (Pulse Width Modulation) signal having a pulse duty cycle during PWM operation. In the case of multiple switches, the PWM signal can thus contain multiple signal components, particularly in the case of only two switches, including two push-pull signal components, each used to control one of the switches, specifically one of the two push-pull switches. "Push-pull" here refers to PWM signals having the same pulse duty cycle but being 180° out of phase with each other and thus "push-pull". In the art, a switch being closed here means a "pulse" of the PWM signal, while a switch being open means a "discontinuity" in the PWM signal. A 100% pulse duty cycle here means a continuous pulse, i.e., a permanently closed switch; a 0% pulse duty cycle means a permanently closed discontinuity, i.e., an open switch. An X% pulse duty cycle means that the PWM signal is always a sequence of equal-length periods, each period containing X% of the duration of the closed switch (pulse), with the remainder being the duration of the open switch (discontinuity). The control unit also establishes a mechanism for selecting the pulse duty cycle of the PWM signal based on this parameter, ensuring that the transmit power corresponds to a predetermined transmit rating regardless of the supply voltage magnitude or value. This parameter is associated with the ultrasonic transmit power. This should mean that this association exists with or assumes the presence of a constant pulse duty cycle. In the case of multiple PWM signals, the pulse duty cycle then applies to all PWM signals. In the case of exactly two switches, the PWM signals are designed to be push-pull, i.e., the pulse duty cycle applies to two signals with a 180° phase shift.

[0015] In summary, in an implementation with exactly two switches and a transformer with a center tap, a push-pull output stage exists in the ultrasonic generator.

[0016] It is assumed here that the supply voltage fluctuates within a permissible or specified range, i.e., between a minimum and a maximum value. The minimum and maximum values ​​for the ultrasonic generator are, for example, set by the manufacturer based on design specifications, component load capacity, etc., for the ultrasonic generator. Therefore, the supply voltage should be within a permissible or specified range, for example, between 18V and 30V. The ultrasonic generator is designed for this voltage range. In the actual operation of the ultrasonic generator, the user selects a constant supply voltage within the permissible range, for example, a constant 20V.

[0017] Therefore, the same transmit rating is always obtained for different supply voltages. This applies to any but fixed voltage, i.e., a voltage that is constant over time, as well as a voltage that fluctuates over time. In other words, the transmit rating can therefore be set arbitrarily (within the specified range) but fixedly. Thus, regardless of the applied voltage (within the permissible voltage range), the transmit power remains constant. "Constant" here means including possible tolerances, such as compliance with the rating plus / minus deviation or tolerance, for example 1%, 2%, 5%, 10%, 20%, etc., depending on the desired accuracy of the transmit power to be complied with.

[0018] Ultrasonic generators, especially transmitter transducers or transmitter-receiver transducers used in ultrasonic sensors or combined ultrasonic transmitter-receiver transducers.

[0019] Predetermined emission ratings can also be changed or altered during ultrasonic emission, particularly in the form of ultrasonic pulse packets. This can be achieved, in particular, by changing the predetermined emission ratings (during the pulse packet variation). Therefore, the selected pulse duty cycle generally also changes during pulse packet emission (e.g., assuming the supply voltage remains constant).

[0020] Alternatively or additionally, the ultrasonic generator, particularly the control unit, can also be configured to operate only intermittently, as described so far, i.e., according to the core aspect of the invention: "selecting the pulse duty cycle according to parameters such that..."; then, during other time periods, the ultrasonic generator operates in a conventional manner (i.e., not according to the aspects of the invention described above), thereby permanently setting the selectable pulse duty cycle. Thus, for example, the following objectives can be achieved:

[0021] For example, the first 10 pulses of the burst packet are generated with a fixed pulse duty cycle (e.g., 50%), and then other pulses or remaining pulses are generated according to aspects of the invention, i.e., the pulse duty cycle is determined based on the parameter, which may, for example, lead to a reduction to 25%.

[0022] Therefore, one aspect of the invention is to operate the ultrasonic transducer or control unit "in accordance with the core of the invention" during certain time periods, as described above, and to operate the ultrasonic transducer or control unit "not in accordance with the core of the invention" (i.e., not according to the above aspects of the invention) during other time periods. In this embodiment, the ultrasonic transducer is thus configured for such selective or optional alternating operation.

[0023] This invention is based on the following considerations:

[0024] The transmitting power of the ultrasonic generator in an ultrasonic sensor, and consequently the received amplitude of the receiver, should not depend on the supply voltage of the sensor or generator. It is also desirable to reduce power losses in the sensor or transmitter. This extends the sensor's lifespan and results in less heat transfer within the sensor, thus reducing temperature drift of its components, particularly the transducer. Consequently, the sensor's system performance is improved.

[0025] This invention is based on the concept that the emitted sound of the improved ultrasonic generator, compared to existing technologies, should also be independent of the sensor's power supply voltage. To achieve voltage-independent acoustic power in the sensor, linear power supplies have been used to date (see again for details). Figure 1 The power supply always maintains the same internal supply voltage (“UI”) as the basis for the switching voltage, i.e., as the “supply voltage for the emitter stage”. This voltage is determined by common requirements for linear power supplies (minimum voltage drop), such as 15V, and is lower than the minimum or lowest required supply voltage, such as 18V for the permissible or specified supply voltage between 18V and 30V. Therefore, the power supply always generates a corresponding power loss in the sensor. Overvoltages (e.g., 3V between UI = 15V and UV = 18V, or up to 15V between UI = 15V and UV = 30V) are converted into heat in the power supply along with the flowing current.

[0026] The present invention, or its proposed implementation, is based on the concept of controlling the transducer's transmit power by adjusting the pulse length (the pulse portion of the pulse duty cycle) of a control signal (from the control unit to the switch) according to the supply voltage. Therefore, the constant 50% pulse duty cycle associated with a fixed internal supply voltage UI is eliminated.

[0027] Not only in boundary sensors as described above, but also in ranging ultrasonic sensors, there is a corresponding requirement that the echo voltage should be independent of the supply voltage. Therefore, this invention can be used in all sensors with a transformer output stage. That is, this invention can also be used in ranging ultrasonic sensors with a transformer output stage, since the transformer output stage is designed to have the proposed ultrasonic generator.

[0028] According to the present invention, power control of the transmitter transducer, independent of the supply voltage, is thus achieved by PWM control.

[0029] According to the present invention, power loss is reduced because the linear in-phase regulator, which is associated with losses, is no longer needed. Furthermore, since the linear in-phase regulator and its wiring components can be omitted, the number of components is reduced, and consequently, the component cost is lowered.

[0030] Therefore, according to the present invention, it is no longer as described above. Figure 1 Instead of operating with a fixed 50% pulse duty cycle as described in existing technology, it operates with a variable pulse duty cycle, wherein the value is selected in relation to the parameters, particularly the supply voltage at the input (see below). Therefore, a constant output power for transmitting ultrasonic waves can be obtained within tolerance.

[0031] A recognized drawback is that, compared to the aforementioned prior art, more components must be designed for a higher supply voltage range. This is because there is no longer a single circuit area (in...) Figure 1 In the UI (right side), the supply voltage is safely reduced to a lower value via the power supply. Relatedly, the size of existing transformers may now need to be set slightly larger. Furthermore, in a preferred embodiment (see below, Supply Voltage Detection), the sensor's supply voltage must be measured periodically. A relatively high computational load on the CPU is also required to determine or adjust the pulse duty cycle. However, as mentioned above, this is acceptable for reducing power consumption and component count, leading to the advantages described above.

[0032] In a preferred embodiment, the coupling element is a transformer. The coupling input is specifically the primary terminals of the transformer, consisting of two, three, or more poles. The coupling output is the secondary terminals of the transformer, which is configured to convert the switching voltage applied to the primary terminals into a transducer voltage at the secondary terminals. In particular, the transformation includes step-up, for example, from about 15V to about 300V. The aforementioned voltage “mapping” is thus performed via “transformation.”

[0033] With the appropriate transformer, it is possible to operate with a lower supply voltage while still obtaining a high voltage for the transducer.

[0034] In a preferred embodiment, the parameter is a transducer voltage value or amplitude, or a value related to it. The control unit is configured to select the pulse duty cycle in such a way that the parameter is adjusted to a predetermined voltage rating by means of control rules. That is, as a result of the adjustment, the transmit power corresponds to the transmit rating. In particular, a control circuit is established here whereby the transducer voltage forms a controlled variable, the voltage rating is a reference variable, and the pulse duty cycle is the manipulated variable.

[0035] The above description also applies to voltage ratings, meaning that for variable, different supply voltages, it can always be selected as the same ("any but fixed"). In this respect, the transducer voltage can be adjusted. Because the transducer is only arranged downstream (with any tolerances, such as temperature drift), the power of the emitted ultrasonic waves can be adjusted very precisely as needed, thus allowing the emitted power to be determined with particularly small tolerances.

[0036] In an alternative implementation, the parameter is a supply voltage value or a related value. The control unit is configured to change the pulse duty cycle in such a way that the parameter is mapped to the pulse duty cycle according to a configurable mapping rule. As a result of this measure, the transmit power then corresponds to the transmit rating.

[0037] This implementation is based on the following assumptions: in a given ultrasonic generator, there exists a sufficiently precise or reproducible relationship between the supply voltage and the generated ultrasonic energy, where the pulse duty cycle remains constant, thus ensuring the required correlation. It is also assumed that changing the pulse duty cycle alters the transmitted power. Therefore, values / parts of the mapping rule can be generated, for example through calculation, simulation, or experimentation, because a specific pulse duty cycle is determined for a given supply voltage value to produce a specific transmitted power. By determining corresponding duty cycle values ​​for multiple different supply voltages, mapping rules of arbitrary precision can be generated, or fine-grained classifications can be applied to different supply voltages.

[0038] Therefore, according to this embodiment, there is simple control rather than ultrasonic power adjustment. Consequently, after fixing a certain current pulse duty cycle, this typically results in the tolerance of the desired ultrasonic power being greater than the tolerance specified above. Here, fluctuations in the performance of the ultrasonic generator components cause inaccuracies. Not only the transducer, but also the transformer, for example, due to temperature drift, leads to inaccuracies or tolerances in the final actual emitted ultrasonic power.

[0039] Transfer functions and / or lookup tables are particularly well-suited as mapping rules.

[0040] Compared to regulation, this is tolerable given the overall simplicity of the control design. For example, for transducer voltages in the high-voltage range (e.g., several hundred volts, around 300V), there are further advantages if this voltage is generated from a lower switching voltage (e.g., 15V) via a transformer. This avoids the problems associated with measuring / processing / feedback high transducer voltages to the computational unit on the low-voltage side.

[0041] In a preferred embodiment, the control unit is configured to decrease the pulse duty cycle when the magnitude or value of the supply voltage increases and increase the pulse duty cycle when the magnitude or value of the supply voltage decreases. Therefore, the increase in input power (theoretically with the same pulse duty cycle) as the voltage increases becomes increasingly limited in order to achieve the desired constant ultrasonic output power.

[0042] In a preferred embodiment, the control unit is configured to select a pulse duty cycle between 0.1% and 65%, particularly between 1% and 50%. Alternatively or additionally, the ultrasonic generator is configured to supply a voltage between 15V and 50V, particularly between 18V and 30V. Alternatively or additionally, the ultrasonic generator is configured to switch a voltage in the range of 5V to 30V, particularly 15V, with a tolerance range of 10%. Utilizing an appropriate pulse duty cycle within this range, particularly good results can be obtained regarding ultrasonic wave generation, and the ultrasonic generator is designed for practically common voltage ranges, with the corresponding voltage. This appropriate "configuration" of the control unit or ultrasonic generator is achieved, in particular, by selecting the permissible voltage range / load range suitable for the components or contained components of the load. This selection is made, in particular, by the manufacturer / designer of the specific ultrasonic generator, and depends especially on the application, etc.

[0043] In a preferred embodiment, the switching unit includes a measuring unit connected to the control unit. It is then used to determine the parameters or related values, particularly the supply voltage or transducer voltage as parameters. It may also be used to transmit these values ​​to the control unit. The control unit then processes the determined parameters to determine a suitable pulse duty cycle.

[0044] In a preferred variant of this embodiment, the control unit includes a measurement unit. This control unit is particularly designed as an integrated microcontroller with measurement capabilities or containing such a microcontroller. This further reduces the number of components.

[0045] In a preferred embodiment, the control unit comprises a microcontroller or such a microcontroller, particularly a microcontroller having an integrated measurement unit as described above.

[0046] In a preferred embodiment, the switching element is an electronic switch, which in particular comprises a power transistor or a power transistor. This results in a generator that is particularly wear-free.

[0047] In a preferred embodiment, the ultrasonic generator does not include a power supply. In this case, "power supply" specifically refers to a switching power supply or a component for voltage stabilization. The latter component specifically refers to an in-phase regulator or voltage regulator (fixed or variable), especially an integrated voltage regulator IC. The corresponding power supply is therefore generally unnecessary outside the ultrasonic generator, as it is designed for a correspondingly wide range of supply voltages (e.g., the commonly mentioned 18V to 30V). These components are only needed when generating the supply voltage (especially when multiple devices, modules, etc., share the same supply voltage, and the ultrasonic generator is just one of them).

[0048] The objective of this invention is also accomplished by an ultrasonic boundary sensor according to claim 12. It includes a transmitting portion for emitting ultrasonic waves and a receiving portion for receiving at least one portion of the emitted ultrasonic waves. The transmitting portion includes an ultrasonic generator according to the invention for generating ultrasonic waves.

[0049] The ultrasonic boundary sensor and at least some possible implementations thereof, as well as their respective advantages, have been described in accordance with the meaning of the ultrasonic generator of the present invention.

[0050] In a preferred embodiment, the ultrasonic boundary sensor is a dual-material sensor, particularly a dual-plate sensor. This invention is particularly advantageous for such sensors because the ultrasonic output power can be maintained at the desired rated value in a particularly advantageous manner.

[0051] The objective of this invention is also accomplished by an ultrasonic reflection sensor having an ultrasonic generator according to the invention for generating ultrasonic waves to be emitted. The transducer in this ultrasonic generator is also designed to receive at least a portion of the reflected ultrasonic waves. Therefore, this invention can also be used with ultrasonic reflection sensors, particularly ranging ultrasonic sensors.

[0052] The ultrasonic reflection sensor and at least a portion of its possible implementations and their respective advantages have been described in relation to the ultrasonic generator of the present invention.

[0053] The objective of this invention is also accomplished by a method of operating the ultrasonic generator of this invention, wherein the following is performed: setting the emission rating. As described above, tolerances, i.e., typically the range of ratings, are set. A supply voltage is applied to the input. The control unit controls the switching element with a PWM signal having a pulse duty cycle in PWM operation, while selecting the pulse duty cycle based on parameters related to the ultrasonic emission power, so that the emission power corresponds to the emission rating regardless of the magnitude or value of the supply voltage.

[0054] The method and at least some of its possible implementations and respective advantages have been explained in relation to the ultrasonic sensor of the present invention. Attached Figure Description

[0055] Other features, effects, and advantages of the present invention are derived from the following description and accompanying drawings of preferred embodiments of the invention, which are illustrated herein by way of schematic schematic diagrams:

[0056] Figure 1 A circuit block diagram of an ultrasonic generator according to the prior art is shown.

[0057] Figure 2 A circuit block diagram of an ultrasonic generator with a transformer according to the present invention is shown.

[0058] Figure 3 The diagram illustrates the variation of the pulse duty cycle on the supply voltage according to the mapping rule.

[0059] Figure 4 A circuit block diagram of an ultrasonic generator according to the present invention without a transformer is shown.

[0060] Figure 5 A circuit block diagram of an ultrasonic generator according to the present invention, having a push-pull output stage, is shown.

[0061] List of reference numerals

[0062] 2. Ultrasonic generator

[0063] 4. Ultrasound

[0064] 6 Input terminals

[0065] 8 Switching Units

[0066] 10 Output terminals

[0067] 12 Coupling elements

[0068] 14 Transformers

[0069] 16 Coupled Input Terminal

[0070] 18 Coupled output terminal

[0071] 20 Primary Terminals

[0072] 22 secondary terminals

[0073] 24 transducers

[0074] 26 Transducer Input Terminal

[0075] 28 Transducer output terminal

[0076] 30 Circuits

[0077] 32 Switching elements

[0078] 34 Control Unit

[0079] 35 PWM signal

[0080] 37 Intermittent

[0081] 38 pulses

[0082] PWM signals of 39a and 39b

[0083] 40 units of measurement

[0084] 42 Mapping Rules

[0085] 44 Adjustment Rules

[0086] 500 power supply

[0087] UV power supply voltage

[0088] UI internal power supply voltage

[0089] W value

[0090] US switching voltage

[0091] UW transducer voltage

[0092] PS transmit power

[0093] PP pulse duty cycle

[0094] K parameters

[0095] SS emission ratings

[0096] US voltage rating

[0097] T-cycle duration

[0098] Ton connection time

[0099] BT tolerance range Detailed Implementation

[0100] Figure 2 With Figure 1 The corresponding view shows a circuit block diagram of an ultrasonic generator 2 according to the present invention, which is used to generate an ultrasonic signal 4 in the form of an ultrasonic wave from a supply voltage UV. In this example, the supply voltage UV can be assumed to be a value between 18V and 30V. The ultrasonic generator 2 is designed for this voltage range. In the present case, the value W of the supply voltage UV is constant at 20V. The ultrasonic generator 2 has two input terminals 6 to which the supply voltage UV is applied or will be applied during operation.

[0101] The ultrasonic generator 2 includes a switching unit 8 having an input terminal 6 and a two-pole output terminal 10. As will be further explained below, the switching unit 8 generates a pulsed switching voltage US from the supply voltage UV, which alternates in pulse form between 0V and the supply voltage UV (here, 20V) and is applied between its poles to the output terminal 10.

[0102] The ultrasonic generator 2 includes a coupling element 12 having a two-pole coupling input terminal 16 and a two-pole coupling output terminal 18. The coupling input terminal 16 is connected to the output terminal 10. The coupling element 12 is here a transformer 14, with its primary terminal 20 being the coupling input terminal 16 and its secondary terminal 22 being the coupling output terminal 18. The transformer 14 here converts the 0V / 20V switching voltage US between the two poles of the coupling input terminal 16 into a boost-converted transducer voltage UW, and an AC voltage, for example, with an amplitude of 300V, between the two poles of the coupling output terminal 18.

[0103] The ultrasonic generator 2 includes a transducer 24, here a piezoelectric transducer, having a bipolar transducer input terminal 26 and a transducer output terminal 28. The transducer input terminal 26 is connected to the coupling output terminal 18. The transducer 24 generates ultrasonic waves 4 from the transducer voltage UW at the transducer input terminal 26, which are output through the transducer output terminal 28. The ultrasonic waves 4 here have a transmission power PS.

[0104] The switching unit 8 has a circuit 30. It comprises, in series, an input terminal 6, an output terminal 10, and a switching element 32, which is a semiconductor power switch. The switching unit 8 includes a control unit 34, which is a microcontroller, configured as follows:

[0105] The control unit controls the switch 32 with a PWM signal 35 during PWM operation, that is, it alternately turns the switch on during the intervals 37 and turns it off during the pulses 38 of the PWM signal 35. This results in an alternating application of 0V or the supply voltage UV, i.e., 20V, to the output terminal 10. Here, the control unit 34 selects the pulse duty cycle PP of the PWM signal 35 based on the parameter K, which is the value W of the supply voltage UV. Assuming the pulse duty cycle PP is constant, the parameter K is related to the transmit power PS, because the latter increases as the value W of the supply voltage UV increases, and vice versa. This selection is performed according to mapping rule 42.

[0106] and Figure 1 The relevant description applies accordingly to the pulse duty cycle PP in the PWM signal 35. However, the pulse duty cycle is no longer fixed at 50%, but is variably selected by the control unit 34, here ranging from 17% to 49%, as described below. That is, the on-time Ton of pulse 38 is between 17% and 39% of the cycle duration T, with the remaining cycle duration T consisting of interruptions 37.

[0107] Figure 3 Mapping rule 42 is shown. Mapping rule 42 assigns each value of parameter K ( Figure 4 The horizontal axis (K) represents the supply voltage value between 15V and 30V, where a pulse duty cycle PP (Y) is assigned. This mapping rule is chosen such that for each time parameter K is assigned to the pulse duty cycle PP, a transmit power PS corresponding to a specified transmit rating SS (here, the allowable tolerance range BT) appears. Therefore, an exemplary variation of the transmit power PS with respect to parameter K is also shown in the figure, where the transmit power PS is normalized to the transmit rating SS (“1” in the figure). The tolerance range BT is ±7.5% of the transmit rating, or a total of 15% (“0.15” in the figure).

[0108] Figure 2 The following is also shown: The transmitted power PS is symbolically shown to follow the transmitted rating SS in relation to the parameters. To determine parameter K, the ultrasonic generator 2 includes a measuring unit 40, here a voltmeter for the supply voltage UV or its value W. In an alternative embodiment (not shown), the measuring unit 40 (in the form of a microcontroller) is integrated into the control unit 34, such that the microcontroller has voltage measurement functionality or a corresponding module. The value pairs of mapping rule 42 ( Figure 3 The curve variation process in the curve, where K is assigned to PP, is chosen such that there exists a constant (i.e., within the tolerance range BT) ultrasonic wave transmission power PS for all values ​​of parameter K. In this sense, the transmission power PS, or its value, then always corresponds to the transmission rating SS (with a value of "1" within the tolerance range of "0.15").

[0109] Figure 2 An alternative embodiment of the ultrasonic generator 2 is also shown in dashed lines. Here, the value W of the transducer voltage UW, rather than the value of the supply voltage UV, is selected as parameter K. The measurement or determination of the characteristic value W by the measuring unit 40 is shown in a very simplified manner, without, for example, converting the voltage level from approximately 300V to the low-voltage side of approximately 15V. Instead of using mapping rule 42, this characteristic value is now processed according to adjustment rule 44. In this case, the characteristic value K is adjusted by adjusting the pulse duty cycle PP to a predetermined voltage rating US, which corresponds to the desired transmission rating SS of the transmission power PS.

[0110] Figure 4 An alternative embodiment of the ultrasonic generator 2 is shown, in which the transformer 14 is not provided. Therefore, the coupling element 12 is designed to be directly connected between the two poles of the output terminal 10 or coupling input terminal 16 and the transducer input terminal 26 or coupling output terminal 18. Therefore, the transducer voltage UW is the same as the switching voltage US. Here, the direct connection is designed to be very small and therefore can be omitted in principle, such as... Figure 4 As detailed above. In other words, transducer input 26 is therefore directly connected to output 10 because coupling element 12 has degenerated into a zero-position element, and coupling terminals 16 and 18 effectively disappear or coincide with output 10 and transducer input 26 (the actual disappearance is due to...). Figure 4 The brackets shown indicate ().

[0111] In order to obtain the transducer voltage UW within the desired range of approximately 300V, in Figure 4 The circuit uses a supply voltage UV of approximately 300V, which is then directly switched to a switching voltage US in pulse form. Therefore, the entire ultrasonic generator 2 is correspondingly... Figure 2 The ultrasonic generator 2 operates at a relatively high voltage.

[0112] Figure 5Another alternative embodiment of the ultrasonic generator 2 is shown. Here, the coupling element 12 or transformer 14 is designed with a center tap on the input side. Therefore, the output terminal 10 and the coupling input terminal 16 or primary terminal 20 are designed to be three-pole, instead of two-pole in the example above. The connection from the output terminal 10 to the switching element 32, which was previously present in a series arrangement, is now implemented in a two-pole form via two connecting lines. The switching element 32 contains two separate switches, each serving one of the two terminals from the output terminal 10, that is, returning it to the supply voltage UV in a switching manner. The control unit 34 now generates a PWM signal 35 in the form of two push-pull PWM partial signals 39a and 39b. Here, the pulse duty cycle is the same in the case of the two partial signals 39a and 39b. Partial signal 39b exists as a 180° phase-shifted partial signal 39a.

Claims

1. An ultrasonic generator (2) having: - Input terminal (6) for supply voltage (UV) in DC voltage form. - A switching unit (8) having the input terminal (6) and the output terminal (10), the switching unit being configured to generate a switching voltage (US) at the output terminal (10) from the supply voltage (UV) at the input terminal (6). - A coupling element (12) is connected to the output (10) with its coupling input (16) and has a coupling output (18) and is configured to map the switching voltage (US) applied to the coupling input (16) to the transducer voltage (UW) at the coupling output (18). - A transducer (24), which has its transducer input (26) connected to the coupling output (18) and has a transducer output (28) and is configured to generate ultrasonic waves (4) at the transducer output (28) by the transducer voltage (UW) and emit them there, wherein, The generated ultrasonic waves (4) have a transmission power (PS) during operation. - The switching unit (8) includes a circuit (30) having the input terminal (6), the output terminal (10) and the switching element (32) arranged in series, and the switching unit (8) includes a control unit (34). - Wherein, the control unit (34) is configured to control the switching element (32) with a PWM signal (35) having a pulse duty cycle (PP) in PWM operation and simultaneously select the pulse duty cycle (PP) of the PWM signal (35) based on a parameter (K) related to the transmitted power (PS) of the ultrasonic wave (4), such that the transmitted power (PS) corresponds to a predetermined transmitted rating (SS) independently of the value (W) of the supply voltage (UV), and - Wherein, the parameter (K) is the value (W) of the supply voltage (UV), and the control unit (34) is configured to select the pulse duty cycle (PP) such that the parameter (K) is mapped to the pulse duty cycle (PP) according to a predetermined mapping rule (42), thereby the transmit power (PS) corresponds to the transmit rating (SS).

2. The ultrasonic generator (2) according to claim 1, characterized in that, The coupling element (12) is a transformer (14), and the coupling input terminal (16) is the primary terminal (20) of the transformer (14), and the coupling output terminal (18) is the secondary terminal (22) of the transformer (14), and the transformer (14) is configured to convert the switching voltage (US) applied to the primary terminal (20) into the transducer voltage (UW) at the secondary terminal (22).

3. The ultrasonic generator (2) according to claim 1 or 2, characterized in that, The parameter (K) is the value (W) of the transducer voltage (UW), and the control unit (34) is configured to select the pulse duty cycle (PP) such that the parameter (K) is adjusted to a predetermined voltage rating (US) by means of the adjustment rule (44) to adjust the pulse duty cycle (PP), thereby the transmit power (PS) corresponds to the transmit rating (SS).

4. The ultrasonic generator (2) according to claim 1, characterized in that, The control unit (34) is configured to decrease the pulse duty cycle (PP) when the value (W) of the supply voltage (UV) increases, and increase the pulse duty cycle (PP) when the value (W) of the supply voltage (UV) decreases.

5. The ultrasonic generator (2) according to claim 1, characterized in that, The control unit (34) is configured to select the pulse duty cycle (PP) between 0.1% and 65%, and / or the ultrasonic generator (2) is configured to provide a supply voltage (UV) between 15V and 50V, and / or the ultrasonic generator (2) is configured to provide a switching voltage (US) between 5V and 30V.

6. The ultrasonic generator (2) according to claim 1, characterized in that, The switching unit (8) includes a measuring unit (40) connected to the control unit (34) for determining the parameter (K).

7. The ultrasonic generator (2) according to claim 6, characterized in that, The control unit (34) includes the measurement unit (40).

8. The ultrasonic generator (2) according to claim 1, characterized in that, The control unit (34) includes a microcontroller.

9. The ultrasonic generator (2) according to claim 1, characterized in that, The switching element (32) is an electronic switch.

10. The ultrasonic generator (2) according to claim 1, characterized in that, The ultrasonic generator (2) does not include a power supply (500).

11. An ultrasonic boundary sensor having a transmitting portion for emitting ultrasonic waves (4) and a receiving portion for receiving at least a portion of the emitted ultrasonic waves (4), wherein, The transmitting part includes an ultrasonic generator (2) according to any one of claims 1 to 9 for generating ultrasonic waves (4).

12. The ultrasonic boundary sensor according to claim 11, characterized in that, The ultrasonic boundary sensor is a dual-chip sensor or a dual-material sensor.

13. An ultrasonic reflection sensor comprising an ultrasonic generator (2) according to any one of claims 1 to 9 for generating ultrasonic waves (4) to be emitted, wherein, The transducer (24) is also designed to receive at least a portion of the reflected ultrasonic waves (4).

14. A method of operating an ultrasonic generator (2) according to any one of claims 1 to 10, wherein: - Set the transmit rating (SS). - Apply the supply voltage (UV) at the input terminal (6), and - The control unit (34) controls the switching element (32) with a PWM signal having a pulse duty cycle (PP) in PWM operation, and at the same time selects the pulse duty cycle (PP) based on a parameter (K) related to the transmission power (PS) of the ultrasonic wave (4) such that the transmission power (PS) corresponds to the transmission rating (SS) independently of the value (W) of the supply voltage (UV).

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