Transformerless control of an ultrasonic transducer with only one external energy storage device

Abstract

Driver stage for controlling a first ultrasonic transducer (TD1), comprising a first charge pump (CP1) and a first switch (SW1) with at least one first and one second connection and a second switch (SW2) with at least one first and one second connection and a third switch (SW3) with at least one first and one second connection and a fourth switch (SW4) with at least one first and one second connection and a fifth switch (SW5) with at least one first and one second connection and a first capacitor (C1) with a positive terminal (C1P) of the first capacitor (C1) and with a negative terminal (C1N) of the first capacitor and a first signal connection (DRV1) and a first node (K1) and a second node (K2) and a third node (K3) and a first reference potential (GND1), wherein the first charge pump (CP1) is connected to the first terminal of the second switch (SW2) and wherein the second terminal of the second switch (SW2) at the first node (K1) is connected to the first terminal of the first switch (SW1) and to the positive terminal (C1P) of the first capacitor (C1) and wherein the second terminal of the first switch (SW1) is connected to the first reference potential (GND1) and wherein the second terminal of the fifth switch (SW5) at the second node (K2) is connected to the first signal terminal (DRV1) and to the first terminal of the third switch (SW3) and wherein the second terminal of the third switch (SW3) at the third node (K3) is connected to the first terminal of the fourth switch (SW4) and to the negative terminal (C1N) of the first capacitor (C1) and wherein the second terminal of the fourth switch (SW4) is connected to the first reference potential (GND1) and wherein the first signal terminal (DRV1) is connected to a signal terminal (STD1) of the first ultrasound transducer (TD1) and wherein a ground connection (MTD1) of the first ultrasound transducer (TD2) is connected to the first reference potential (GND1), characterized by that the second terminal of the second switch (SW2) is connected to the first terminal of the fifth switch (SW5).

Description

Field of invention

[0001] The invention relates to an improved driver stage for transformerless control of an ultrasonic transducer, in which an external storage capacity and a connection can be saved compared to the prior art. General introduction

[0002] Ultrasonic measurement systems are often used in the state of the art (SdT) for obstacle detection and distance determination in parking assistance systems, but also for person detection, for example, in rooms, and in industrial applications, such as level monitoring. For this purpose, an ultrasonic transmitter emits an ultrasonic signal. When reflected from an object, the reflected signal can be detected by an ultrasonic receiver. The distance between the transmitter and the object can be determined using a time-of-flight measurement. The same ultrasonic transducer can serve as both transmitter and receiver.

[0003] Especially for use in parking assistance systems in motor vehicles, the production of ultrasonic measuring systems must be as cost-effective as possible, since new vehicles tend to have several ultrasonic measuring systems installed. State of the art

[0004] Circuits for controlling piezoceramic ultrasonic transducers are well known in the state of the art. Fig. 1 describes a transformerless driver stage for driving an ultrasonic transducer with alternating positive and negative operating voltage. First, Fig. 1. In the following, similar functional elements are designated with numbers such as "first," "second," "third," etc., for easier differentiation. These numbers are therefore to be understood as part of the functional element name. Please refer to the list of reference symbols.

[0005] Fig. Figure 1 shows a transformerless control of an ultrasonic transducer according to the prior art (SdT). A second driver stage (TR2) comprises a circuit for transformerless control of a second ultrasonic transducer (TD2) within a second integrated circuit (IC2). A second capacitor (C2) and a third capacitor (C3) are also required to control the second ultrasonic transducer (TD2). The second capacitor (C2) and the third capacitor (C3) are external circuit components.

[0006] First, the structure of the control within the second integrated circuit (IC2) is described.

[0007] The second integrated circuit (IC2) includes four terminals for connecting internal circuitry to external components. These terminals are a second operating voltage potential terminal (VDRV2), a second signal terminal (DRV2), a positive terminal (C3P) of the third capacitor (C3), and a negative terminal (C3N) of the third capacitor.

[0008] The second integrated circuit (IC2) further comprises a second charge pump (CP2), a sixth switch (SW6), a seventh switch (SW7), an eighth switch (SW8), a ninth switch (SW9), and a tenth switch (SW10). Each of these switches has a first terminal and a second terminal.

[0009] The second charge pump (CP2) is connected at a fifth node (K5) to the terminal of the second operating voltage potential (VDRV2) and to the first terminal of the tenth switch (SW10) and to the first terminal of the seventh switch (SW7).

[0010] The second terminal of the tenth switch (SW10) is connected at a sixth node (K6) to the first terminal of the eighth switch (SW8) and to the second signal terminal (DRV2).

[0011] The second terminal of the seventh switch (SW7) is connected at a fourth node (K4) to the first terminal of the sixth switch (SW6) and to the positive terminal (CP3) of the third capacitor (C3).

[0012] The second terminal of the eighth switch (SW8) is connected at a seventh node to the first terminal of the ninth switch (SW9) and to the negative terminal (CN3) of the third capacitor (C3).

[0013] The second terminal of the sixth switch (SW6) and the second terminal of the ninth switch (SW9) are connected to a second reference potential (GND2) at an eighth node (K8).

[0014] The second capacitor (C2) has two terminals. The first terminal of the second capacitor (C2) is connected to the second operating voltage potential (VDRV2). The second terminal of the second capacitor is connected to the second reference potential (GND2).

[0015] The second signal terminal (DRV2) is connected to a signal terminal (STD2) of the second ultrasonic transducer (TD2).

[0016] A ground terminal (MTD2) of the second ultrasonic transducer (TD2) is connected to the second reference potential (GND2).

[0017] The second reference potential (GND2) is smaller than the second operating voltage potential (VDRV2) and preferably equal to 0 V.

[0018] The vehicle's electrical system typically only provides voltages in the range of 6 V to 12 V. To excite the second ultrasonic transducer (TD2) to oscillate, significantly higher voltages, on the order of more than 20 V, must be present at the signal terminal (STD2) of the second ultrasonic transducer (TD2). The internal structure of the second charge pump (CP2) is not relevant here. Corresponding circuits are known in the prior art (SdT). The function of the second charge pump (CP2) is to provide the high second operating voltage (VDRV2) required to excite the ultrasonic transducer from the electrical system voltage.

[0019] The control of the second ultrasonic transducer (TD2) as a transmitter comprises three phases and is described below. The first phase is only required initially at the start of transmission, while the second and third phases are repeated alternately throughout the entire transmission duration.

[0020] In the first phase, the seventh switch (SW7) and the ninth switch (SW9) are closed. The sixth switch (SW6), the eighth switch (SW8), and the tenth switch (SW10) are opened. The second charge pump (CP2) is now connected to the second operating voltage potential terminal (VDRV2) and to the positive terminal (C3P) of the third capacitor (C3). The negative terminal (C3N) of the third capacitor (C3) is connected to the second reference potential (GND2). The second capacitor (C2) and the third capacitor (C3) are charged.

[0021] In the second phase, the second ultrasonic transducer (TD2) is controlled with a negative voltage, i.e. the negative operating voltage stored in the capacitor C3 is applied to the signal terminal (STD2) of the second ultrasonic transducer (TD2). For this purpose, the sixth switch (SW6) and the eighth switch (SW8) are closed. The seventh switch (SW7), the ninth switch (SW9) and the tenth switch (SW10) are open. When the eighth switch (SW8) is closed, the negative terminal (C3N) of the third capacitor (C3) is connected to the signal terminal (STD2) of the second ultrasonic transducer (TD2). When the sixth switch (SW6) is closed, the positive terminal (C3P) of the third capacitor (C3) is connected to the second reference potential (GND2). Thus, in the second phase, the negative operating voltage is applied to the signal terminal (STD2) of the second ultrasonic transducer (TD2).

[0022] In the third phase, the second ultrasonic transducer (TD2) is controlled with a positive operating voltage, i.e. the positive operating voltage is applied to the signal terminal (STD2) of the second ultrasonic transducer (TD2). For this purpose, the seventh switch (SW7), the tenth switch (SW10) and the ninth switch (SW9) are closed. The sixth switch (SW6) and the eighth switch (SW8) are open. With the tenth switch (SW10) closed, the second signal terminal (DRV2) is connected to the terminal of the second operating voltage potential (VDRV2) and the output of the second charge pump (CP2). The positive second operating voltage (STD2) is therefore applied to the signal terminal (STD2) of the second ultrasonic transducer (TD2). The closed seventh switch (SW7) connects the positive terminal (C3P) of the third capacitor (C3) to the terminal of the second operating voltage potential (VDRV2).The closed ninth switch (SW9) connects the negative terminal (C3N) of the third capacitor (C3) to the second reference potential (GND2). Thus, the third capacitor is charged during the third phase.

[0023] The second capacitor (C2) is charged exclusively by the second charge pump (CP2). Theoretically, with the described state-of-the-art control (SdT), it is possible to simultaneously control the second transducer (TD2) and charge the second capacitor (C2). In practice, however, this is impractical and is not used. This raises the question of whether the second capacitor (C2) can be eliminated.

[0024] DE 10 2018 101 519 A1 discloses a driver stage for controlling a first ultrasonic transducer, comprising a first charge pump, a first switch with at least a first and a second terminal, a second switch with at least a first and a second terminal, a third switch with at least a first and a second terminal, a fourth switch with at least a first and a second terminal, a fifth switch with at least a first and a second terminal, a first capacitor with a positive terminal of the first capacitor and with a negative terminal of the first capacitor, a first signal terminal, a first node, a second node, a third node, and a first reference potential. The first charge pump is connected to the first terminal of the second switch. The second terminal of the second switch is connected to the first terminal of the first switch at the first node.The second terminal of the first switch is connected to the first reference potential. The second terminal of the fifth switch is connected at the second node to the first signal terminal and to the first terminal of the third switch. The second terminal of the third switch is connected at the third node to the first terminal of the fourth switch and to the negative terminal of the first capacitor. The second terminal of the fourth switch is connected to the first reference potential. The first signal terminal is connected to a signal terminal of the first ultrasonic transducer. A ground terminal of the first ultrasonic transducer is connected to the first reference potential.

[0025] A driver stage of the same type for controlling an ultrasonic transducer is also known from WO 2017 / 140 673 A1. Task

[0026] The proposal is therefore based on the object of creating a solution by modifying the switch arrangement within the driver stage, which allows for saving external capacitance. This object is achieved by a device according to claim 1 and a method according to claim 2. Solution to the task

[0027] The problem of eliminating the need for an external capacitance and thus also a connection, thus reducing costs, is solved according to the invention by using the external capacitance used to reverse the polarity of the voltage applied to the ultrasonic transducer as a power source. This approach is new to those skilled in the art and has not yet been used in the prior art.

[0028] The circuit design of a driver stage according to the invention is shown as an example in Fig. 2 shown.

[0029] A first driver stage (TR1) according to the invention for driving a first ultrasonic transducer (TD1) comprises a first charge pump (CP1), a first switch (SW1), a second switch (SW2), a third switch (SW3), a fourth switch (SW4), and a fifth switch (SW5). Each of these switches has at least a first and a second terminal.

[0030] The first driver stage (TR1) according to the invention also comprises a first capacitor (C1) with a positive terminal (C1P) of the first capacitor (C1) and with a negative terminal (C1N) of the first capacitor (C1) and a first signal terminal (DRV1) and a first node (K1) and a second node (K2) and a third node (K3) and a first reference potential (GND1).

[0031] The first charge pump (CP1) is connected to the first terminal of the second switch (SW2). The second terminal of the second switch (SW2) is connected at the first node (K1) to the first terminal of the first switch (SW1), to the positive terminal (C1P) of the first capacitor (C1), and to the first terminal of the fifth switch (SW5).

[0032] The second terminal of the first switch (SW1) is connected to the first reference potential (GND1).

[0033] The second terminal of the fifth switch (SW5) is connected to the first signal terminal (DRV1) and to the first terminal of the third switch (SW3) at the second node (K2).

[0034] The second terminal of the third switch (SW3) is connected at the third node (K3) to the first terminal of the fourth switch (SW4) and to the negative terminal (C1N) of the first capacitor (C1).

[0035] The second terminal of the fourth switch (SW4) is connected to the first reference potential (GND1).

[0036] The first signal terminal (DRV1) is connected to a signal terminal (STD1) of the first ultrasonic transducer (TD1). A ground terminal (MTD1) of the first ultrasonic transducer (TD2) is connected to the first reference potential (GND1).

[0037] The first reference potential (GND1) is preferably 0 V.

[0038] The voltage at the output of the first charge pump (CP1) is preferably more than 20 V.

[0039] The first charge pump (CP1) and the first switch (SW1) and the second switch (SW2) and the third switch (SW3) and the fourth switch (SW4) and the fifth switch (SW5) and the first node (K1) and the second node (K2) and the third node (K3) and the first signal output (DRV1) are preferably realized in a first integrated circuit (IC1).

[0040] The first capacitor (C1) and the first ultrasonic transducer (TD1) are not part of the first integrated circuit (IC1).

[0041] The first switch (SW1) and the second switch (SW2) and the third switch (SW3) and the fourth switch (SW4) and the fifth switch (SW5) are realized with microelectronic components, preferably with bipolar or field-effect transistors.

[0042] The first capacitance (C1) is a predominantly capacitive impedance.

[0043] A method for controlling the first ultrasonic transducer (TD1) to emit ultrasonic signals by the first driver stage (TR1) is performed in three phases. The last two phases can be repeated cyclically. The three phases are described below.

[0044] In the first phase, the first capacitor (C1) is charged to the output voltage of the first charge pump (CP1). For this purpose, the second switch (SW2) and the fourth switch (SW4) are closed. The closed second switch (SW2) connects the positive terminal of the first capacitor (C1P) to the output of the first charge pump (CP1). The closed fourth switch (SW4) connects the negative terminal (C1N) of the first capacitor (C1) to the first reference potential (GND1). The first switch (SW1), the third switch (SW3), and the fifth switch (SW5) are open.

[0045] In the second phase, the negative voltage of the first capacitor (C1) is applied to the signal terminal (STD1) of the first ultrasonic transducer (TD1). For this purpose, the first switch (SW1) and the third switch (SW3) are closed. The closed first switch (SW1) connects the positive terminal (C1P) of the first capacitor (C1) to the first reference potential (GND1). The closed third switch (SW3) connects the negative terminal (C1N) of the first capacitor (C1) to the first signal terminal (DRV1). The first signal terminal (DRV1) is connected to the signal terminal (STD1) of the first ultrasonic transducer (TD1). The second switch (SW2), the fourth switch (SW4), and the fifth switch (SW5) are open.

[0046] In the third phase, the positive voltage of the first capacitor (C1) is applied to the signal terminal (STD1) of the first ultrasonic transducer (TD1). For this purpose, the fourth switch (SW4) and the fifth switch (SW5) are closed. The closed fourth switch (SW4) connects the negative terminal (C1N) of the first capacitor (C1) to the first reference potential (GND1). The closed fifth switch (SW5) connects the positive terminal (C1P) of the first capacitor (C1) to the first signal terminal (DRV1). The first signal terminal (DRV1) is connected to the signal terminal (STD1) of the first ultrasonic transducer (TD1). The first switch (SW1), the second switch (SW2), and the third switch (SW3) are open.

[0047] The first phase is only necessary initially at the start of transmission, while the second and third phases are repeated alternately throughout the entire transmission period.

[0048] The first capacitor (C1) serves as the sole energy source for the ultrasonic transducer during the entire transmission process, since no connection to the first charge pump (CP1) is established after completion of the first phase.

[0049] The method for controlling a first ultrasonic transducer (TD1) for emitting ultrasonic signals by a driver stage can thus be briefly described as comprising a first phase for charging a first capacitor (C1) to the output voltage of the first charge pump (CP1), a second phase for applying the voltage of the first capacitor (C1) as a negative voltage to the first ultrasonic transducer (TD1), and a third phase for applying the voltage of the first capacitor (C1) as a positive voltage to the signal terminal (STD1) of the first ultrasonic transducer (TD1). The first phase is carried out only once at the beginning of the transmitting process. The second phase and the third phase are carried out alternately for the entire duration of the transmitting process. The transmitting processes can, in particular, also be repeated cyclically.The first phase following the first phase can be the aforementioned second phase or the third phase. After any cyclic repetition of the second and third phases, further phases can follow. These include, for example, a reception phase and, if necessary, an attenuation phase. These phases will not be discussed further here.

[0050] The device of the driver stage for controlling a first ultrasonic transducer (TD1) comprises, in brief, a first charge pump (CP1) or voltage source and a first capacitor (C1), first means (SW2, SW4) for charging the first capacitor (CP1) with electrical energy from the charge pump (CP1) or from the voltage source, and second means (SW1, SW3, SW4, SW5) for connecting the first capacitor (CP1) and the first ultrasonic transducer (TD1) with different polarities. The first means (SW2, SW4) do not charge the first capacitor (CP1) with electrical energy from the charge pump (CP1) or voltage source when the first capacitor (CP1) is connected to the ultrasonic transducer (TD1) via the second means (SW1, SW3, SW4, SW5), so that no interference occurs. This operation of the ultrasonic transducer only via the first capacitor (C1) without connection to another energy source is new to those skilled in the art. Advantage

[0051] Such an improved driver stage for controlling an ultrasonic transducer eliminates the need for an external capacitor and a connection pin on the driver stage's integrated circuit. This reduces system costs and simplifies the PCB layout. List of characters Fig. 1 shows an example of a transformerless control of an ultrasonic transducer according to the state of the art (SdT). Fig. 2 shows an example of a transformerless control of an ultrasonic transducer according to the invention with an improved switch arrangement within the integrated circuit compared to the prior art (SdT). Description of the figuresFigure 1

[0052] Fig. Figure 1 shows an example of a transformerless control of an ultrasonic transducer according to the prior art (SdT). A second driver stage (TR2) comprises a circuit for transformerless control of a second ultrasonic transducer (TD2) within a second integrated circuit (IC2). A second capacitor (C2) and a third capacitor (C3) are also required to control the second ultrasonic transducer (TD2). The second capacitor (C2) and the third capacitor (C3) are external circuit components.

[0053] First, the structure of the control within the second integrated circuit (IC2) is described.

[0054] The second integrated circuit (IC2) includes four terminals for connecting internal circuitry to external components. These terminals are a second operating voltage potential terminal (VDRV2), a second signal terminal (DRV2), a positive terminal (C3P) of the third capacitor (C3), and a negative terminal (C3N) of the third capacitor.

[0055] The second integrated circuit (IC2) further comprises a second charge pump (CP2), a sixth switch (SW6), a seventh switch (SW7), an eighth switch (SW8), a ninth switch (SW9), and a tenth switch (SW10). Each of these switches has a first terminal and a second terminal.

[0056] The second charge pump (CP2) is connected at a fifth node (K5) to the terminal of the second operating voltage potential (VDRV2) and to the first terminal of the tenth switch (SW10) and to the first terminal of the seventh switch (SW7).

[0057] The second terminal of the tenth switch (SW10) is connected at a sixth node (K6) to the first terminal of the eighth switch (SW8) and to the second signal terminal (DRV2).

[0058] The second terminal of the seventh switch (SW7) is connected at a fourth node (K4) to the first terminal of the sixth switch (SW6) and to the positive terminal (CP3) of the third capacitor (C3).

[0059] The second terminal of the eighth switch (SW8) is connected at a seventh node to the first terminal of the ninth switch (SW9) and to the negative terminal (CN3) of the third capacitor (C3).

[0060] The second terminal of the sixth switch (SW6) and the second terminal of the ninth switch (SW9) are connected to a second reference potential (GND2) at an eighth node (K8).

[0061] The second capacitor (C2) has two terminals. The first terminal of the second capacitor (C2) is connected to the second operating voltage potential (VDRV2). The second terminal of the second capacitor is connected to the second reference potential (GND2).

[0062] The second signal terminal (DRV2) is connected to a signal terminal (STD2) of the second ultrasonic transducer (TD2).

[0063] A ground terminal (MTD2) of the second ultrasonic transducer (TD2) is connected to the second reference potential (GND2). Figure 2

[0064] Fig.Figure 2 shows an example of a transformerless control of an ultrasonic transducer according to the invention with an improved switch arrangement within the integrated circuit compared to the prior art (SdT). This eliminates one connection of the integrated circuit and an external capacitance.

[0065] A first driver stage (TR1) comprises a circuit for transformerless control of a first ultrasonic transducer (TD1) within a first integrated circuit (IC1). A first capacitor (C1) is also required to control the first ultrasonic transducer (TD1). The first capacitor (C1) is an external circuit component.

[0066] First, the structure of the control within the first integrated circuit (IC1) is described.

[0067] The first integrated circuit (IC1) includes three terminals for connecting internal circuit components to external components. These terminals are a first signal terminal (DRV1) and a positive terminal (C1P) of the first capacitor (C1), and a negative terminal (C1N) of the first capacitor (C1).

[0068] The first integrated circuit (IC1) further comprises a first charge pump (CP1), a first switch (SW1), a second switch (SW2), a third switch (SW3), a fourth switch (SW4), and a fifth switch (SW5). Each of these switches has a first and a second terminal.

[0069] The first charge pump (CP1) is connected to the first terminal of the second switch (SW2).

[0070] The second terminal of the second switch (SW2) is connected at a first node (K1) to the first terminal of the first switch (SW1) and to the positive terminal (C1P) of the first capacitor (C1) and to the first terminal of the fifth switch (SW5).

[0071] The second terminal of the first switch (SW1) is connected to a first reference potential (GND1).

[0072] The second terminal of the fifth switch (SW5) is connected to the first signal terminal (DRV1) and to the first terminal of the third switch (SW3) at a second node (K2).

[0073] The second terminal of the third switch (SW3) is connected at a third node (K3) to the first terminal of a fourth switch (SW4) and to the negative terminal (C1N) of the first capacitor (C1).

[0074] The second terminal of the fourth switch (SW4) is connected to the first reference potential (GND1).

[0075] The first signal terminal (DRV1) is connected to a signal terminal (STD1) of the first ultrasonic transducer (TD1). A ground terminal (MTD1) of the first ultrasonic transducer (TD2) is connected to the first reference potential (GND1). List of reference symbols STD1 Signal connection (STD1) of the first ultrasonic transducer (TD1); STD2 Signal connection (STD2) of the second ultrasonic transducer (TD2); MTD1 Ground connection (MTD1) of the first ultrasonic transducer (TD1); MTD2 Ground connection (MTD2) of the second ultrasonic transducer (TD2); C1 first capacity; C1N negative terminal (C1N) of the first capacitor (C1); C1P positive terminal (C1P) of the first capacitor (C1); C2 second capacity; C3 third capacity; C3P positive terminal (C3P) of the third capacitor (C3); C3N negative terminal (C3N) of the third capacitor (C3); CP1 first charge pump; CP2 second charge pump; DRV1 first signal connection; DRV2 second signal connection; IC1 first integrated circuit; IC2 second integrated circuit; GND1 first reference potential; GND2 second reference potential; K1 first node; K2 second node; K3 third node; K4 fourth node; K5 fifth node; K6 sixth node; K7 seventh node; K8 eighth knot; SdT state of the art; SW1 first switch; SW2 second switch; SW3 third switch; SW4 fourth switch; SW5 fifth switch; SW6 sixth switch; SW7 seventh switch; SW8 eighth switch; SW9 ninth switch; SW10 tenth switch; TD1 first ultrasonic transducer; TD2 second ultrasonic transducer; TR1 first driver stage; TR2 second driver stage; VDRV2 Second operating voltage potential;

Claims

[1] Driver stage for controlling a first ultrasonic transducer (TD1), comprising a first charge pump (CP1) and a first switch (SW1) having at least a first and a second terminal and a second switch (SW2) having at least a first and a second terminal and a third switch (SW3) having at least a first and a second terminal and a fourth switch (SW4) having at least a first and a second terminal and a fifth switch (SW5) having at least a first and a second terminal and a first capacitance (C1) having a positive terminal (C1P) of the first capacitance (C1) and a negative terminal (C1N) of the first capacitance and a first signal connection (DRV1) and a first node (K1) and a second node (K2) and a third node (K3) and a first reference potential (GND1), wherein the first charge pump (CP1) is connected to the first terminal of the second switch (SW2) and wherein the second terminal of the second switch (SW2) at the first node (K1) is connected to the first terminal of the first switch (SW1) and to the positive terminal (C1P) of the first capacitor (C1) and wherein the second terminal of the first switch (SW1) is connected to the first reference potential (GND1) and wherein the second terminal of the fifth switch (SW5) at the second node (K2) is connected to the first signal terminal (DRV1) and to the first terminal of the third switch (SW3) and wherein the second terminal of the third switch (SW3) at the third node (K3) is connected to the first terminal of the fourth switch (SW4) and to the negative terminal (C1N) of the first capacitor (C1) and wherein the second terminal of the fourth switch (SW4) is connected to the first reference potential (GND1) and wherein the first signal terminal (DRV1) is connected to a signal terminal (STD1) of the first ultrasonic transducer (TD1) and wherein a ground terminal (MTD1) of the first ultrasonic transducer (TD2) is connected to the first reference potential (GND1), characterized by that the second terminal of the second switch (SW2) is connected to the first terminal of the fifth switch (SW5). [2] Method for controlling a first ultrasonic transducer (TD1) for emitting ultrasonic signals by a driver stage, comprising a first phase for charging a first capacitor (C1) to the output voltage of a first charge pump (CP1) by connecting a positive terminal (C1P) of the first capacitor (C1) to an output of the first charge pump (CP1) by closing a second switch (SW2) and by connecting a negative output (C1N) of the first capacitor (C1) to a first reference potential (GND1) by closing a fourth switch (SW4), while a first switch (SW1) and a third switch (SW3) and a fifth switch (SW5) are open and a second phase for applying the negative voltage of the first capacitor (C1) to a signal terminal (STD1) of the first ultrasonic transducer (TD1), by connecting the negative terminal (C1N) of the first capacitor (C1) to the signal terminal (STD1) of the first ultrasonic transducer (TD1) by closing the third switch (SW3) and by connecting the positive terminal (C1P) of the first capacitor (C1) to the first reference potential (GND1) by closing the first switch (SW1), while the second switch (SW2) and the fourth switch (SW4) and the fifth switch (SW5) are open and a third phase for applying the positive voltage of the first capacitor (C1) to the signal terminal (STD1) of the first ultrasonic transducer (TD1) by connecting the positive terminal (C1P) of the first capacitor (C1) to the signal terminal (STD1) of the first ultrasonic transducer (TD1) by closing the fifth switch (SW5) and by connecting the negative terminal (C1N) of the first capacitor (C1) to the first reference potential (GND1) by closing the fourth switch (SW4), while the first switch (SW1) and the second switch (SW2) and the third switch (SW3) are open, where the first phase is executed only once at the beginning of the sending process and whereby the second phase and the third phase are carried out alternately for the entire duration of the transmission process.

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