DE102022129340B3 - CIRCUIT WITH AN OSCILLATING CIRCUIT FOR CONTROLLING AN ACTUATOR FOR DRIVING AN VIBRATIONAL MOVEMENT IN A MEMS - Google Patents

Abstract

Various circuits for controlling an actuator for driving an oscillatory movement of at least one movable component of a micro-electromechanical system, MEMS, as well as a MEMS equipped with such a circuit are described. The circuits have at least one MEMS capacitance, which is designed as a component of an actuator in such a way that it forms a component of an electro-mechanical converter of the actuator, the converter being configured to convert electrical energy stored in the MEMS capacitance into at least one mechanical one Size to drive a movement of the actuator. The circuits contain a step-up circuit for generating a charging voltage for direct, capacitive-unbuffered charging of the MEMS capacity and/or a pauseable resonant circuit with the MEMS capacitance as resonant circuit capacity.

Description

The present invention relates to a circuit for controlling an actuator, in particular a MEMS actuator, for driving an oscillatory movement in a micro-electromechanical system (MEMS), as well as a MEMS equipped therewith. The circuit has a resonant circuit with a variable oscillation period. The MEMS can in particular be a microscanner system with a deflection element (mirror) arranged to oscillate, the actuator being set up to drive an oscillation movement (oscillation) of the deflection element.

Many MEMS, i.e. systems with several components, the dimensions of which are typically in the range of 1 µm to 100 µm, with the MEMS themselves typically each having dimensions in the range of about 10 µm to a few millimeters, have movable mechanical parts that are used can be driven with electrical energy, so that a microscopic machine is present as an electromechanical system.

Mass elements of MEMS arranged to oscillate, in particular deflection elements of microscanners, can be made to oscillate in various ways. However, this always requires a driving force that is able to deflect the deflection element (e.g. mirror plate) from its rest position. One or more actuators are typically used as drives for MEMS (in particular small microphones, loudspeakers or gyroscopes, microscanners or microscanner systems having several microscanners) which provide such force, which operate according to an electrostatic, electromagnetic, piezoelectric, thermal or another actuator principle or according to a mixed form operated by two or more such actuator principles.

The term “MEMS actuator”, as used herein, is to be understood in particular as an actuator that can convert electrical and/or magnetic energy into mechanical energy and/or vice versa, and for this purpose uses a MEMS or is itself a component thereof , especially as this itself or as a component of it. Such a MEMS actuator can in particular be designed so that it works based on the direct or inverse piezoelectric effect. As far as an “actuator” is referred to herein, this can always be in particular a MEMS actuator.

In the case of microscanners, which in technical language are also referred to as “MEMS scanners”, “MEMS mirrors” or “micro mirrors” or in English in particular as “microscanners” or “micro-scanning mirrors” or “MEMS mirrors”, These are specifically MEMS or, more precisely, micro-opto-electro-mechanical systems (MOEMS) from the class of micromirror actuators for the dynamic modulation of electromagnetic radiation, especially visible light. Depending on the design, the modulating movement of an individual mirror can be translational or um At least one axis takes place rotationally. In the first case, a phase-shifting effect is achieved, in the second case, the deflection of the incident electromagnetic radiation is achieved. Microscanners are also considered in which the modulating movement of an individual mirror, at least also, takes place rotationally. In contrast to mirror arrays , in which the modulation of incident light occurs via the interaction of a large number of individual small mirrors on a single MEMS component, the modulation in microscanners is typically generated via a single mirror per MEMS component (microscanner).

Microscanners can therefore be used in particular to deflect electromagnetic radiation in order to modulate an incident electromagnetic beam with respect to its deflection direction by means of a deflection element (“mirror”). This can be used in particular to effect a Lissajous projection of the beam into an observation field or projection field. For example, imaging sensory tasks can be solved or display functionalities can be implemented. In addition, such microscanners can also be used to irradiate materials in an advantageous manner, in particular for their processing. Possible other applications are in the area of lighting or illuminating certain open or closed rooms or areas of space with electromagnetic radiation, for example in the context of headlight applications.

In many cases, microscanners have a mirror plate (“mirror”) as a deflection element, which is suspended laterally on elastically stretchable springs. A distinction is made between single-axis mirrors, which should preferably only be suspended so that they can rotate about a single axis, from two-axis and multi-axis mirrors, in which rotations, in particular rotational oscillatory movements, about a corresponding number of different axes are possible, in particular simultaneously.

A microscanner system for deflecting an electromagnetic beam can therefore in particular have a two-axis microscanner, i.e. a microscanner with two different non-parallel, in particular mutually orthogonal, oscillation axes or a combination of several individual, in particular two, single-axis microscanners, which are arranged in such a way that the Incident beam can be deflected one after the other by the various individual microscanners of the microscanner system in order to generate a two-dimensional deflection pattern, in particular a Lissajous figure. In a microscanner system with a combination of two or three single-axis microscanners, their non-parallel oscillation axes can lie orthogonally to one another, in particular in pairs.

Especially in so-called Lissajous microscanners or Lissajous microscanner systems, two non-parallel, in particular mutually orthogonal, oscillation axes are operated simultaneously, in particular in resonance, in order to generate a trajectory of the radiation deflected by the deflection element in the form of a Lissajous figure. In this way, large amplitudes can be achieved in both axes.

From the EP 2 514 211 B1 Such a deflection device for a projection system for projecting Lissajous figures onto an observation field is known, which is designed to deflect a light beam, in particular a laser beam, around at least a first and a second deflection axis for generating Lissajous figures.

Electrostatic, electromagnetic, piezoelectric, thermal and other actuator principles are typically used as drives for MEMS, such as in particular small microphones, loudspeakers or gyroscopes, and in particular for microscanners or microscanner systems. Especially with piezoelectric actuators (“piezoactuators”), a piezoelectric material is deformed in an electric field generated by an (electrical) capacitance using the inverse piezoelectric effect depending on the strength of the field. If the field is variable over time, in particular due to a variable voltage applied to the capacitance, this results in a variable deformation of the piezo material that can be controlled by the field variation and is used as a small motor to drive a mechanical movement, especially in microscanners, an oscillatory movement of the mirror can be.

However, particularly in the case of resonantly operated, oscillatory MEMS components, such as the deflection element in a microscanner, the actuator(s) are often not strong enough overall to control the oscillatory MEMS component within the scope of a single activation of the actuator(s). to statically deflect it to a target amplitude desired during operation. In order to still achieve the target deflection, the at least one actuator, in the case of a piezo actuator its piezoelectric material, must be subjected to a periodic alternating voltage whose frequency corresponds at least to a good approximation, ideally exactly, to the mechanical resonance frequency of the oscillatory MEMS component. This then results in small driving forces that always occur at the right time, which after a certain time are able to significantly oscillate the mechanical oscillator formed by the oscillatory MEMS component and its suspension or bearing and thus gradually “charge” it with mechanical energy. until the target amplitude is reached (and can possibly be maintained over a longer period of time).

From an electrical point of view, this drive process in a capacitive actuator, in particular a piezo actuator, corresponds to a constant recharging of its capacitor. Especially in the case of a microscanner with a piezoelectric drive, the amplitude of the alternating voltage across the capacitor of the piezoelectric actuator significantly influences the scanning angle (target amplitude) of the microscanner that is established or is maximum achievable in the steady state.

Particularly when a MEMS is to be used in a device that only has a very limited amount of electrical energy or electrical power available to supply energy during operation, such as in a battery-operated, in particular portable device (e.g. in a mobile, in particular portable End device, e.g. smartphone, or a so-called “wearable”, or AR/VR glasses or a MEMS integrated into clothing) is usually the case, energy-efficient drives for the MEMS are advantageous or even necessary in order to last as long as possible, especially one To enable the devices to have a sufficiently long, self-sufficient service life depending on the application.

In order to reduce the power consumption of the MEMS, it is therefore desirable to make the recharging processes on the actuator capacitor as efficient as possible. So the resulting total leis The power consumption for driving the MEMS can be minimized and, in particular, the service life of the battery(s) or rechargeable batteries can be increased.

In addition, the voltage level available to the device, in particular a battery voltage, is often below a voltage level required by the actuator, so that a voltage conversion is required to achieve it.

Out of FR 2 829 314 A1 a device and a method for controlling an electronically controlled piezo actuator, in particular a piezoelectric stepped fuel injection nozzle, are known, which is controlled by the electronic injection computer of an internal combustion engine in a motor vehicle.

Out of US 2005/0029905 A1 a device for controlling a piezoelectric ultrasonic actuator is known, which is monitored electronically by a computer that controls a direct current voltage source. The device comprises a DC-DC converter which is powered by the voltage source and delivers, at least at the output, a DC voltage between two end terminals, to which at least one arm is connected in parallel, which consists of two alternately controllable, series-connected bridge switches and whose center alternates with the two Output terminals of the DC-DC converter are connected by a load which consists of at least one actuator connected in series with a resonant inductance.

Out of WO 2003/038918 A2 For ultrasonic-piezoelectric injectors for fuel injection in a motor vehicle heat engine, a device and a method that can be carried out with it for controlling at least one piezoelectric ultrasonic actuator are known, which is electronically monitored by a control computer and a DC voltage source. The device comprises a DC/AC voltage converter amplifier fed by the DC voltage source, which consists of a bridge or push-pull circuit, the high voltage output of which is connected to a resonant circuit which consists of the actuator and a resonant inductor, the converter consisting of a connection with at least one Transformer exists, whose primary winding is connected to the voltage source via at least one controllable switch and whose only secondary winding supplies a high-voltage and high-frequency alternating signal that excites the piezoelectric actuator.

Out of DE 198 54 789 A1 A method and a device for charging and discharging a piezoelectric element are described. The method and the device are characterized in that the charging current charging the piezoelectric element or the discharge current discharging the piezoelectric element9 is set taking into account the capacity of the piezoelectric element. This means that the charging and discharging of piezoelectric elements can be carried out as quickly and widely as desired under all circumstances.

Out of DE 101 02 286 A1 a circuit arrangement for controlling piezoelectric materials to generate high voltage and generate waveforms is known. It consists of a voltage source, a coil with an electronic switch and a diode, with at least 4 electronic switches arranged between two connection points in the form of a bridge circuit and a piezo element connected between the bridge balancing points and at least one current sink each arranged in parallel with two electronic switches.

Out of DE 10 2013 208 870 A1 a circuit for bipolar charge recovery of a piezoelectric or electrostatic drive is known, in which a piezo actuator is connected in series with a coil. A first connection of the piezo actuator is connected to a first switch and a second switch, with a first connection of the coil being connected to a third switch and a fourth switch. A second connection of the piezo actuator is connected to a second connection of the coil, with the first switch and the third switch being connected to a first connection of a power supply. The second switch and the fourth switch are connected to a second connection of the power supply.

Out of US 2021/0099105 A1 A piezoelectrically driven MEMS pump is known.

It is an object of the present invention to provide an improved circuit for controlling an actuator for energy-efficient and/or space-saving driving of an oscillatory movement in a MEMS, as well as a MEMS, in particular a microscanner system, equipped with such a circuit.

The solution to this problem is achieved in accordance with the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the subclaims and/or the following description, which, for the sake of clarity, is structured into sections each introduced by a heading, but which is not to be construed as a restriction on the content of the text sections covered by it or of the figures described therein.

Terminology

The term “MEMS capacitance” as used herein is to be understood as meaning an electrical capacity, in particular a single electrical capacitor, which is at least partially designed and configured as a component of a MEMS actuator for the operation of the actuator to store the electrical energy used for its (proportional) conversion into mechanical energy, at least temporarily. In particular, such a MEMS capacitance can have a capacitor, in particular a plate capacitor, of a piezo actuator with a piezoelectric material as a dielectric. A MEMS capacitance can in particular be designed as an integrated component of a MEMS, in particular in such a way that the electrodes and the dielectric of the MEMS capacitance each form a layer of a layer sequence generated in or on a semiconductor substrate.

The term “controller” as used herein is understood to mean, in particular, a process or a device (control device) configured to carry out such a process, which is set up to control one or more components of a circuit, including in particular one or more of to control their switching devices in the sense of a control (“open-loop”) or regulation (“closed-loop”) via appropriate signals. In particular, it can be or have a computer program-controlled microcontroller or a hard-wired control circuit. Such a control device can in particular itself be part of the circuit.

The term “boost converter” or “step-up converter”, as used herein, is to be understood as meaning a form of a DC-DC converter that is configured to convert an input voltage into an output voltage during the conversion that the magnitude of the output voltage is greater than the magnitude of the input voltage. The term is not limited to a specific topology or type of such a DC-DC converter.

The term “switching device” as used herein is to be understood as meaning a circuit or component thereof which is or has at least one circuit or component acting as a switch. In particular, the switching device can have one or more switches. In particular, it can be implemented using one or more semiconductor components such as transistors or diodes. For example, a single transistor or a CMOS gate can act as a switch when controlled accordingly. A diode can also act as a switch, especially in the forward direction, if a voltage across it is either above its threshold voltage (in the forward direction) or below its breakdown voltage (in the reverse direction).

The term “capacitive-unbuffered”, as used herein, in relation to a current path is understood to mean that this current path is not buffered by a capacitance in the sense of a voltage buffer, in particular not in the sense of a buffer capacitor. There is therefore (apart from any parasitic capacitances) no capacitive component (in particular capacitor) for buffering (i.e. supporting) the input voltage or input current of a component or circuit part controlled via the current path, in particular the actuator. In particular, any remaining parasitic capacitance of the current path can be in the range of less than or equal to 40 pF, in particular less than or equal to 10 pF.

The term “power source” as used herein means an active two-terminal circuit that delivers an electrical current at its connection points. As an essential property, the strength of this current depends only slightly (“real” current source) or not at all (“ideal” current source) on the electrical voltage at its connection points.

wobei C die Kapazität und L die Induktivität des Schwingkreises sind. Beim realen Schwingkreis ist die Resonanzfrequenz aufgrund der ohmschen Verluste in den Widerständen R je nach Stärke dieser Dämpfung niedriger.The term “a resonance frequency related to a permanently closed state of the resonant circuit,” as used herein, is to be understood as meaning a resonant frequency of the resonant circuit that it has in the steady state when it is permanently closed, that is, at least beyond the transient process, ie in particular not through the first switching device is broken. In an ideal resonant circuit (ie when ohmic resistances R are negligibly small), the resonance frequency f ₀ is: $${\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="DE102022129340B3\_0015.png"\; state="\{\{state\}\}">f</figure-callout>}}_0=\frac{1}{2\pi \sqrt{LC}}$$

where C is the capacity and L is the inductance of the resonant circuit. In the real resonant circuit, the resonance frequency is lower depending on the strength of this damping due to the ohmic losses in the resistors R.

The term “up converter”, as used herein, is to be understood as meaning a voltage converter of any type and/or topology that generates an output voltage from an input voltage via voltage conversion or can generate it in at least one operating mode, so that the magnitude of the output voltage is greater than that Amount of input voltage. For this purpose, a step-up converter can in particular have one or more step-up converters and/or one or more charge pumps.

The terms “comprises,” “includes,” “includes,” “has,” “has,” “with,” or any other variation thereof, as may be used herein, are intended to cover non-exclusive inclusion. For example, a method or device that includes or has a list of elements is not necessarily limited to those elements, but may include other elements that are not expressly listed or that are inherent to such method or device.

Furthermore, unless expressly stated to the contrary, “or” refers to an inclusive or and not an exclusive “or”. For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present).

The terms “a” or “an” as used herein are defined to mean “one or more”. The terms “another” and “another” as well as any other variant thereof are to be understood in the sense of “at least one further”.

The term “configured” or “set up” to fulfill a specific function (and respective modifications thereof), as used here where applicable, is to be understood as meaning that a relevant device or component thereof already exists in a configuration or setting, in which it can carry out the function or at least it can be set - i.e. configurable - in such a way that it can carry out the function after the appropriate setting. The configuration can be carried out, for example, by appropriately setting parameters of a process flow or switches or the like to activate or deactivate functionalities or settings. In particular, the device can have several predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes.

The terms “first”, “second”, “third” and similar terms in the description and in the claims are used to distinguish between similar or otherwise identically named elements and are not necessarily used Description of a sequential, spatial or chronological order used. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein may operate in orders other than those described or illustrated herein.

Circuit with step-up converter (“first circuit”)

A first aspect of the solution presented here relates to a first circuit for controlling an actuator, in particular a MEMS actuator, for driving an oscillatory movement of at least one movable component of a micro-electromechanical system, MEMS. The first circuit can be used in particular to control an actuator for driving a mirror movement in a microscanner system.

It has a step-up converter circuit with an inductance (hereinafter referred to as “booster inductance” to distinguish it from other inductances mentioned below, in particular having one or more coils), an electrical MEMS capacitance and a switching device that can be controlled by a controller. The MEMS capacitance is designed as a component of an actuator in such a way that it forms a component of an electro-mechanical converter of the actuator, the converter being configured to convert electrical energy stored in the MEMS capacitance into at least one mechanical quantity to drive a movement of the actuator (particularly at least one component of it). The switching device is set up, depending on the control, to assume a first circuit configuration and sequentially, in particular alternating several times with the first circuit configuration, a second circuit configuration. In this case (i) in the first circuit configuration, a first current path is enabled through the booster inductance in order to cause an increasing current flow fed by a supply voltage through the booster inductance, and (ii) in the second circuit configuration (apart from possible parasitic capacitances ) capacitive-unbuffered second current path between a first pole of the booster inductance and the MEMS capacitance is activated in order to charge the MEMS capacitance to a first voltage by means of a current flow fed at least in part by the booster inductance (in particular as a current source), which amount is equal to or higher than the supply voltage.

The supply voltage can in particular be generated by the circuit itself or supplied to it externally.

In the first circuit, the electrical energy supplied via the second current path between a first pole of the booster inductance and the MEMS capacitance is available largely undiminished in order to increase the MEMS capacity of the actuator and thus its function by means of an at least partially determined by the booster Inductance fed current flow to charge and thus supply at a voltage level that is higher than the supply voltage. This with conventional step-up converters (cf. 1 and description of the figures) occurs so-called “capacitor paradox” or “two capacitor paradox”, which theoretically limits the efficiency to a maximum of 50% (see https://en.wikipedia.org/wiki/Two_capacitor_paradox), can be avoided here, since there is no need for a constellation with two capacitances that can be switched in parallel via a switch in the voltage amplification path of the step-up converter.

In this way, the first circuit results in a significantly reduced electrical power requirement for controlling the actuator, so that the first circuit including the actuator can also be used in particular in devices that only have a very limited amount of electrical energy or electrical power to supply energy operation is available.

Various exemplary embodiments of the first circuit are described below, each of which, unless this is expressly excluded or is technically impossible, can be combined in any way with each other and with the other aspects of the present solution described below.

In some embodiments, the control is unregulated. As a result, there is no regulation as part of the control, but only pure control (in the sense of “open loop”) without a control loop. Accordingly, the first circuit can be simplified compared to a regulated control, since in particular no controller and no feedback (control loop) are required and the circuit components required for this can therefore be omitted. This means that particularly space-saving solution variants can be implemented. This is possible in particular because in periodic operation, i.e. a periodic alternating change between the two circuit configurations of the switching device, the voltage across the MEMS capacitance is essentially, i.e. to a good approximation, as a linear function of the period duration or, more precisely, the duration of the first circuit configuration can be modeled. A pure control without regulation can also be sufficient for a sufficiently precise adjustment of the voltage across the MEMS capacitance and thus control of the actuator with good accuracy. In addition, energy losses associated with regulation are eliminated, so that the power consumption of the first circuit can be further reduced and its efficiency can be further increased.

In some embodiments, the switching device is further set up to repeatedly temporarily activate a third current path, in particular depending on the control, in such a way that the MEMS capacity can be repeatedly, at least partially, discharged via this third current path, in order to generate a supply voltage of the electromechanical converter that varies over time at the MEMS capacitance. The continuous switching and the resulting discharging can take place in particular periodically. By discharging, a state of charge of the MEMS capacitance can be established, which leads to a lower voltage across the MEMS capacitance and thus to a correspondingly lower input voltage at the actuator than in the charged state of charge (which is achieved during the second configuration of the switching device). In this way, the actuator can be switched at least between two states (charged/discharged), which correspond to two different mechanical states of the actuator via the electromechanical conversion. With an alternating, in particular periodic, change between the two charge states, a corresponding, in particular periodic, mechanical movement can be brought about on the actuator, which is used to drive a movement, in particular an oscillatory movement, in a MEMS (such as a mirror movement, in particular a mirror oscillation of a microscanner system). can be used.

In some embodiments, the third current path is led to a buffer capacity for buffering the supply voltage in order to transfer charge from the MEMS capacity into the buffer capacity when it is discharged. In this way, the charge introduced into the MEMS capacity when charging can be at least partially recovered and used for a subsequent further charging process. In this way, the power consumption of the first circuit can be further reduced and thus its efficiency and thus efficiency can be further increased. In this variant, the third current path is also referred to as the fourth current path to distinguish it from an alternative current path according to another variant for discharging without charge return or buffering.

In some embodiments, the switching device is further set up, in particular depending on the control, repeatedly and temporarily in a period of time in which the second current path is not activated, a fourth current path between the MEMS capacitance and one with an electrically opposite polarity to the first pole to unlock the second pole of the booster inductance in such a way that the MEMS capacitance is charged to a second voltage with a polarity opposite to the polarity of the first voltage. In this way, bipolar operation can be enabled, in which the polarity changes across the MEMS capacitance, in particular alternating. Accordingly, when using an actuator, such as a piezo actuator, which operates in a polarization-dependent manner, different actuator states can be brought about depending on, in particular in time with, the change in polarity of the voltage across the MEMS capacitance. With such a bipolar drive with positive and negative voltages, the power consumption can be halved again - compared to a unipolar drive - using only one positive and one negative voltage, if the same voltage amplitude (V _max - V _min ) is considered.

In some of these embodiments, the circuit device includes: (i) a first switch, S ₁ , for switching an electrical connection between the supply voltage and the second pole of the booster inductor; (ii) a second switch, S ₂ , electrically connected to the first pole of the booster inductance, for switching on or interrupting the first current path; (iii) a third switch, S ₃ , electrically connected to the first pole of the booster inductance, for switching on or interrupting the second current path; and (iv) a fourth switch, S ₄ , electrically connected to the second pole of the booster inductance and the MEMS capacitance, for switching on or interrupting the fourth current path. In this way, a bipolar implementation of the first circuit in the above-mentioned sense can be achieved in a very efficient, particularly component- and thus space- and energy-saving manner, using only four switches in the switching device.

The term “electrically connected” here means a direct electrical connection without any intermediate circuit components (i.e. components) or an indirect connection via one or more intermediate circuit components (i.e. components), e.g. resistors, whereby the connection in particular has the characteristics of a ( small) ohmic resistance R, e.g. with R < 10 Ω.

In some embodiments, the circuit further comprises a fifth switch, S ₅ , for switching on or interrupting a current path lying between the second pole of the inductor and ground.

1. (a) S₁ und S₂ geschlossen, S₃ und S₄ offen;
2. (b) S₁ und S₃ geschlossen, S₂ und S₄ offen;
3. (c) S₂ und S₃ geschlossen, S₁ und S₄ offen;
4. (d) S₁ und S₂ geschlossen, S₃ und S₄ offen;
5. (e) S₂ und S₄ geschlossen, S₁ und S₃ offen;
6. (f) S₂ und S₃ geschlossen, S₁ und S₄ offen.

In particular, according to some of the embodiments, the controller can be configured to gradually switch the circuit device into different switching states according to the following sequence offset, the sequence being run through at least once, preferably several times, in particular periodically:

1. (a) S ₁ and S ₂ closed, S ₃ and S ₄ open;
2. (b) S ₁ and S ₃ closed, S ₂ and S ₄ open;
3. (c) S ₂ and S ₃ closed, S ₁ and S ₄ open;
4. (d) S ₁ and S ₂ closed, S ₃ and S ₄ open;
5. (e) S ₂ and S ₄ closed, S ₁ and S ₃ open;
6. (f) S ₂ and S ₃ closed, S ₁ and S ₄ open.

In some of these embodiments, the first circuit has a buffer capacitance, in particular a capacitor, for capacitive buffering of the supply voltage. The sequence also has a further switching state (b1), which lies between the switching states (b) and (c) and is characterized in that S ₁ and S ₄ are closed and S ₂ and S ₃ are open. When discharging the MEMS capacity, charge can be transferred from the MEMS capacity to the buffer capacity in order to be available for another switching cycle without the corresponding amount of charge having to be made available from the supply voltage source. In this way, the power consumption is also reduced and the efficiency of the (bipolar) first circuit is further increased.

In some embodiments, the sequence has, in addition (to the states (a) to (f) and optionally also to (b1)), a further switching state (b2), which lies between the switching states (b) and (c), and is characterized thereby is that in it S ₂ and S ₄ are closed and S ₁ and S ₃ are open. When discharging the MEMS capacitance, charge from the MEMS capacitance can be passed through the booster inductance in order to at least partially charge it with energy (in its magnetic field) for another switching cycle, without the energy charging resulting from this current Booster inductance must subsequently be provided by the supply voltage source instead. In this way, the power consumption can also be reduced and the efficiency of the (bipolar) first circuit can be further increased.

In some embodiments, the sequence additionally has a further switching state (e1), which follows the switching state (g) and precedes the switching state (f) and which is characterized in that S ₄ and S ₅ are closed in it and S ₁ , S ₂ and S ₃ are open. This enables energy to be recovered even from negative voltages across the MEMS capacitance C _M (following switching state (e1)).

In some embodiments, the controller (more precisely, the corresponding control device) has a multi-stage delay chain and a multiplexer for tapping the respective output signals of the stages of the delay chain in a time-staggered manner in order to generate a time-variable control signal for controlling the switching device. The delay elements of the delay chain can in particular be made from standard cells or as specially defined (“customized”) analog components or circuit parts, with the required delay of the individual stages being the quotient of the maximum necessary switch-on time (duration of the first circuit configuration) and the number of levels can be calculated. The analog version would have the advantage that the delay time of each individual delay element can be set by setting a driver current for the delay elements (current control, cf. "current-starved" inverter), and thus for any MEMS capacitors (with different capacitance values and output voltages ) could be optimally adjusted.

In particular, according to some of these embodiments, the switching device can be controlled by means of the control signal in such a way that switching between the first switching configuration and the second switching configuration, or vice versa, can be effected by means of the control signal.

In this way, control for the circuit, in particular its switching device, can be implemented in a simple and energy-efficient manner.

Circuit with a pauseable resonant circuit (“second circuit”)

A second aspect of the solution relates to a second circuit for controlling an actuator, in particular a MEMS actuator, for driving an oscillatory movement of a mass element in a MEMS. The control can in particular be regulated or unregulated.

1. (i) einen elektrischen Schwingkreis, der eine erste Induktivität (nachfolgend zur Unterscheidung von anderen im weiteren genannten Induktivitäten als „Schwingkreis-Induktivität“ bezeichnet, insbesondere eine oder mehrere Spulen aufweisend), eine erste elektrische MEMS-Kapazität, und eine, insbesondere mittels eines Steuersignals, ansteuerbare erste Schalteinrichtung (nachfolgend auch als „Schwingkreis-Schalter“ bezeichnet) zum selektiven Unterbrechen bzw. Schließen des Schwingkreises in Abhängigkeit von einer Ansteuerung der ersten Schalteinrichtung enthält und eine auf einen dauerhaft geschlossenen Zustand des Schwingkreises bezogene Resonanzfrequenz aufweist; und
2. (ii) eine Steuerung zur Ansteuerung der ersten Schalteinrichtung.

This second circuit has:

1. (i) an electrical resonant circuit, which has a first inductance (hereinafter referred to as “resonant circuit inductance” to distinguish it from other inductors mentioned below, in particular having one or more coils), a first electrical MEMS capacitance, and one, in particular by means of one Control signal, controllable first switching device (hereinafter also referred to as “resonant circuit switch”) for selectively interrupting or closing the resonant circuit depending on a control of the first switching device and has a resonance frequency related to a permanently closed state of the resonant circuit; and
2. (ii) a controller for controlling the first switching device.

The controller is configured to temporarily switch the first switching device into a state during a respective oscillation period of the resonant circuit, when the voltage across the first MEMS capacitance reaches a maximum within the oscillation period, by means of a corresponding control, in particular for a certain portion of the oscillation period by interrupting the resonant circuit in order to bring about an actual oscillation frequency of the resonant circuit that is smaller than the resonance frequency. With the second circuit, the effective oscillation frequency of the resonant circuit can be variably adjusted using the first switching device. The temporary interruption of the oscillating circuit causes a corresponding pausing of the electrical oscillation in the oscillating circuit (“paused oscillating circuit”), which leads to an effective oscillation frequency below the resonance frequency of the oscillating circuit (in a permanently closed state).

The lower effective oscillation frequency can thus be achieved without having to increase the values of the (first) MEMS capacitance C or the (first) inductance L in accordance with relationship (1) (see “Termology” section above). If oscillatory components of a MEMS cannot or should not exceed a certain upper limit frequency with regard to their oscillation frequency, then with the help of the above-mentioned concept of the pauseable oscillating circuit, effective oscillation frequencies can be achieved, in particular also set variably, which are at or below the limit frequency, although values for C and L are used, from which a resonance frequency f ₀ above the cutoff frequency results from relationship (1). In particular, smaller and therefore space-saving inductors L and/or MEMS capacitances (in particular capacitive loads) C can be used and the space required for the circuit for controlling the actuator can be reduced or kept small.

The energy in the resonant circuit is therefore, at least largely, stored in the MEMS capacity in the form of electrical energy during the pause in the oscillation caused by the interruption until the oscillation is continued by closing the resonant circuit. This storage during the pause of the resonant circuit can be largely maintained over a long period of time, at least with a low-loss MEMS capacity, so that a correspondingly large range of values for the variable, adjustable effective oscillation frequency of the resonant circuit can be achieved without significant (particularly application-related) energy losses .

Furthermore, the energy periodically temporarily stored in the first inductance is used or used to reload the MEMS capacitance and thus to operate the actuator fed thereby, so that a particularly low-consumption (periodic) control of the actuator can be achieved. Due to its small space requirement and its high energy efficiency, the circuit is particularly suitable for use in mobile applications, especially in portable devices with small dimensions (e.g. in so-called “wearables”).

The possibility of being able to variably adjust the effective oscillation frequency for given values for C and L based on the control using the first switching device can also be used advantageously to compensate for component tolerances, especially in the context of mass production.

Various exemplary embodiments of the second circuit are described below, each of which can be combined in any way with each other and with the other aspects of the solution described herein, unless this is expressly excluded or is technically impossible.

In some embodiments, the MEMS capacitance is formed as part of the actuator such that it forms part of an electro-mechanical transducer of the actuator. The converter is configured to convert electrical energy stored in the MEMS capacitance into at least one mechanical quantity to drive a movement of the actuator. The actuator can in particular be a MEMS actuator, for example a piezo actuator. The voltage that drops across the MEMS capacitance as part of the electrical oscillation in the resonant circuit can therefore be made available to the actuator directly and without further capacitive buffering, so that a high level of efficiency of the second circuit can be achieved.

In some embodiments, the control circuit may in particular be configured to, in a respective oscillation period of the oscillation circuit, put the first switching device into a state in which it interrupts the oscillation circuit if the voltage across the MEMS capacitance within the oscillation period after a voltage occurring during the oscillation period Reloading of the MEMS capacity reaches a maximum in terms of amount. This ensures that the maximum available energy is used to reload the capacitor and the resonant circuit optimally reduces the total power consumption.

It can also be achieved in this way that the current in the inductance has reached a minimum or approaches zero and therefore no voltage peaks occur through the inductance.

In some embodiments, the resonant circuit has, in addition to the MEMS capacitance, a separately formed second MEMS capacitance with the same or different capacitance value (relative to the first MEMS capacitance). The MEMS capacitance and the second MEMS capacitance are connected in the resonant circuit in such a way that a first pole of the MEMS capacitance is electrically connected to a first pole of the second MEMS capacitance via at least one switch of the first switching device and the resonant circuit inductance and the respective second poles of the two MEMS capacitances are electrically connected to one another in such a way that they are kept at the same (constant or time-variable) electrical potential during operation of the resonant circuit.

In this way, voltages that are complementary to each other in terms of their sign can be tapped at the two MEMS capacitances. In order to achieve a desired difference voltage between the poles of this combination of MEMS capacitances that are furthest apart in terms of potential, it is therefore sufficient to charge the two individual MEMS capacitances to a lower voltage, since the two voltages add up. The above-mentioned principle of the pauseable resonant circuit remains, at least essentially, unaffected. Such a configuration can be used particularly advantageously to achieve a differential drive of an oscillatory MEMS, in particular a drive of an oscillatory movement of a deflection element of a microscanner.

Such a drive is particularly advantageous with regard to achieving the most uniform, smooth oscillation of the deflection element (mirror) of the microscanner and/or for reducing the power consumption. The second MEMS capacitance can then also be designed as a MEMS capacitance of a (in particular second) actuator and thereby form part of a converter that is configured to convert electrical energy stored in the second MEMS capacitance into at least one mechanical quantity to drive a movement of the actuator Actuator to convert.

In some embodiments, the second circuit further comprises a power supply circuit for temporarily supplying electrical energy to the resonant circuit. Despite the losses that are unavoidable in reality (e.g. due to heat development in parasitic, especially ohmic, resistances of the real circuit), radiation of electromagnetic waves at higher frequencies or friction in the MEMS or air friction from moving parts of the MEMS), a longer, in particular even Realize permanent operation of the MEMS in which the energy supply circuit can at least partially compensate for the energy losses. In this way, the energy in the oscillating circuit can be maintained or at least its degradation can be slowed down.

In some embodiments, the power supply circuit has a second switching device that is configured to have a first one depending on a control, in particular by the controller The th feed point for electrical energy is to be temporarily connected to the resonant circuit in order to supply the resonant circuit with electrical energy that is supplied or can be supplied at the first feed point. This means that the energy supply to the resonant circuit, in particular in order to initially oscillate it or to compensate for its energy losses in subsequent operation, can be precisely adjusted based on the control, in particular its time course can be optimized.

Specifically, according to some embodiments, the second circuit can be configured, in particular by means of a corresponding control, to temporarily close the second switching device in a respective oscillation period of the resonant circuit when the voltage across the MEMS capacitance reaches a maximum within the oscillation period and the same Polarity like a voltage provided by the power supply circuit at the first feed point. The MEMS capacity is recharged accordingly when it is currently maximally charged as part of the electrical oscillation that is already occurring in the resonant circuit, so that only an additional charge to fill the charge of the MEMS capacity to a target voltage needs to be supplied by the energy supply circuit. In the aforementioned case that a second MEMS capacitance is also provided in the resonant circuit, this can be implemented there accordingly, taking the opposite polarity into account.

In some embodiments, the second circuit is configured to temporarily connect the first feed point to the oscillating circuit in the respective oscillation period by means of the second switching device at a time before which two consecutive recharging processes of the MEMS capacity of the oscillating circuit have already taken place in the oscillation period, since last The first feed point was temporarily connected to the resonant circuit by means of the second switching device. This can be particularly advantageous with regard to an efficient and compact implementation, because it is then sufficient to provide only a single high-voltage source, either with positive or negative polarity of the output voltage. In particular, if such a high-voltage source has conventional coil-based step-up converters to increase the voltage, one coil can be saved on a circuit board. This can be an advantage, especially when implementing the circuit using an integrated circuit (IC, e.g. ASiC), where hardly any additional IC-external components are necessary.

In some embodiments, the second circuit is configured to temporarily electrically connect the first feed point to the resonant circuit in the respective oscillation period by means of the second switching device and thereby charge the MEMS capacitance while the first switching device is in a state in which it is Resonant circuit inductance electrically separates from the first feed point. The charging current coming from the first feed point is thus fed into the resonant circuit, more precisely into the MEMS capacity, while the resonant circuit is interrupted. The charging current is therefore essentially completely used, i.e. apart from any parasitic losses, to recharge the MEMS capacity, while the resonant circuit inductance remains de-energized at this point. In particular, a very quick and effective energy supply to the resonant circuit can be achieved to compensate for energy losses that have occurred.

In some embodiments, the second circuit is configurable such that the amount of electrical energy supplied to the resonant circuit in at least one oscillation period is adjustable. This can be achieved in various ways. For example, the duration of the recharging can be varied over time, the current strength of the recharging current can be adjusted (in particular by adjusting the voltage driving it) or the frequency at which recharging is adjusted, for example so that the recharging only occurs every mth period of the electrical Oscillation occurs in the resonant circuit, where m > 0 is a natural number.

The second circuit can be configured in particular in such a way that the amount of electrical energy supplied to the resonant circuit can be set individually for each oscillation period (e.g. by means of a control) or globally for all mth oscillation periods, where m > 0 is again a natural number .

In some embodiments, the energy supply circuit has an inductive coupling device, in particular an inductively coupled coil pair, for temporarily inductively feeding electrical energy into the resonant circuit. This can be provided in addition to or as an alternative to a wired power feed into the resonant circuit. So the power supply circuit, In any case, if there is no wired power supply, it must be galvanically decoupled from the resonant circuit.

In some embodiments, the energy supply circuit has a third switching device which is configured, depending on a control, to temporarily connect a second feed point for electrical energy to the resonant circuit in order to supply the resonant circuit with electrical energy that is supplied or can be supplied at the second feed point that the polarity of a first electrical supply voltage present at the first feed point is opposite to the polarity of a second electrical supply voltage present at the second feed point, thus enabling a bipolar energy supply to the resonant circuit.

The generation and/or feeding of the second supply voltage can in particular correspond to one or more of the supply voltage supplied to the first feed point, in particular be identical to it (except for the different polarity).

Combined circuit with step-up converter and pauseable resonant circuit

The aforementioned principles of the first circuit and the second circuit can also be used in combination as part of the solution.

According to a first approach, a circuit combined in this way results in particular in that, starting from the first circuit (in particular starting from one of its embodiments described here), a resonant circuit is or is further provided, which has a capacity that is at least partially determined by the MEMS circuit. Capacitance is defined, has a resonant circuit inductance and a controllable second switching device for selectively interrupting or closing the resonant circuit depending on a control of the second switching device. The resonant circuit has a resonance frequency related to a permanently closed state of the resonant circuit. In addition, the controller is further configured to control the second switching device in such a way that it temporarily opens the second switching device for a certain portion of the oscillation period during a respective oscillation period of the oscillating circuit, thereby causing an interruption of the oscillating circuit and thus an actual oscillation frequency of the oscillating circuit , which is smaller than the resonance frequency.

The circuit can in particular have any, in particular one or more, of the embodiments of the second circuit described herein.

The electrical oscillations generated in the resonant circuit thus lead to a time-varying, in particular alternating, charge and thus voltage of the MEMS capacity, so that the mechanical quantity for driving a movement of the actuator, to which the MEMS capacity belongs, also varies accordingly.

A circuit combined in this way also results, according to a second approach, in particular, in that, starting from the second circuit with a power supply circuit, this power supply circuit has a step-up converter which is configured to convert an input voltage applied at the feed point into a relatively higher output voltage in order to use the resonant circuit to supply this output voltage with electrical energy when the second switching device is in a state in which it temporarily electrically connects the feed point to the resonant circuit. In this way, a high-voltage source can be dispensed with and instead only a low-voltage source can be used to provide a supply voltage for the second circuit. The step-up converter can in particular have a step-up converter circuit according to the first circuit, the resonant circuit capacitance being at least partially formed by the MEMS capacitance of the step-up converter circuit.

The circuit can, in particular in the case of more than one feed point per feed point individually or identically, have each, in particular one or more, of the embodiments of the step-up converter circuit described herein from the first circuit as a step-up converter circuit.

MEMS, especially microscanner system

A third aspect of the present solution relates to a MEMS comprising: (i) a mass element configured to oscillate; (ii) an actuator for driving an oscillatory movement of the mass element; and (iii) a circuit according to the first aspect or the second aspect or a circuit combined therefrom, each for controlling the actuator in such a way that it is thereby caused to move the oscillatory mass element in an oscillatory movement.

The MEMS capacitance is designed as a component of the actuator in such a way that it itself forms a component of an electro-mechanical converter of the actuator, and the converter is configured to convert electrical energy stored in the MEMS capacitance into at least one mechanical quantity to drive a movement of the actuator in order to drive the oscillatory movement of the mass element.

In some embodiments, the MEMS has a microscanner system and the mass element is designed as an oscillatory configured deflection element of the microscanner system for deflecting electromagnetic radiation incident on the deflection element. In this way, a particularly energy-efficient drive of the movement, in particular of the deflection element, can be achieved, in particular for scanning an electromagnetic beam (e.g. laser beam).

The features and advantages explained in relation to the first and second aspects of the solution also apply accordingly to the microscanner system according to the third aspect of the solution.

Further advantages, features and possible applications of the present solution result from the following detailed description in connection with the figures.

• 1 als Ausgangspunkt für die Erläuterung der ersten Schaltung aus 2A: eine herkömmliche Schaltung zum Ansteuern eines kapazitiven Aktuators mit einem geregelten Hochsetzsteller;
• 2A eine erste beispielhafte Ausführungsform der ersten Schaltung, die ein unipolares Ansteuern des Aktuators ermöglicht;
• 2B einen Vergleich der Schaltungen aus den 1 und 2A;
• 3 ein Diagramm zur Darstellung eines zeitlichen Stromverlaufs durch die Induktivität der Schaltung aus 2A/2B bei deren Betrieb, während in der Induktivität die magnetische Energie aufgebaut wird;
• 4 eine beispielhafte Ausführung einer Steuerungseinrichtung zur Steuerung einer ersten Schaltung, insbesondere gemäß 2A.
• 5 eine zweite beispielhafte Ausführungsform der ersten Schaltung, die ein bipolares Ansteuern des Aktuators ermöglicht;
• 6 einen beispielhaften zeitlichen Verlauf der Konfiguration der Schalteinrichtung der Schaltung aus 5, insbesondere der Schaltzustände ihrer einzelnen Schalter; und
• 7 als Ausgangspunkt für die Erläuterung der zweiten Schaltung aus 8: eine herkömmliche Schaltung zur Ansteuerung eines MEMS-Aktuators zum Antrieb eines schwingungsfähigen MEMS, bei der ein Umladen einer MEMS-Kapazität des MEMS-Aktuators anhand einer Halbbrücke unter Verwendung zweier gegenpoliger Versorgungsspannungen erfolgt;
• 8 eine erste beispielhafte Ausführungsform der zweiten Schaltung, mit einem pausierbaren Schwingkreis sowie mit einer Hochspannungsquelle zur Bereitstellung einer Versorgungsspannung für die Schaltung;
• 9 eine qualitative Darstellung der Verläufe der Spannung an der MEMS-Kapazität des Schwingkreises und des von der Hochspannungsquelle zu liefernden Ladestroms bei der Schaltung aus 8;
• 10 eine zweite beispielhafte Ausführungsform der zweiten Schaltung mit einem pausierbaren Schwingkreis sowie mit einer über ein gekoppeltes Spulenpaar induktiv an den Schwingkreis gekoppelten Hochspannungsquelle zur Bereitstellung einer Versorgungsspannung für die Schaltung;
• 11 eine dritte beispielhafte Ausführungsform der zweiten Schaltung mit einem pausierbaren Schwingkreis sowie mit einer auf zwei separate MEMS-Kapazitäten aufgeteilten Schwingkreiskapazität;
• 12 eine erste beispielhafte Ausführungsform einer Schaltung, in der die Konzepte der ersten Schaltung und der zweiten Schaltung kombiniert sind, um eine Schaltung mit unipolarem Hochsetzsteller und pausierbarem Schwingkreis zu bilden;
• 13 eine zweite beispielhafte (bipolare) Ausführungsform einer Schaltung in der die Konzepte der ersten Schaltung und der zweiten Schaltung kombiniert sind, um eine Schaltung mit bipolarem Hochsetzsteller und pausierbarem Schwingkreis zu bilden; und
• 14 eine dritte beispielhafte (bipolare) Ausführungsform einer Schaltung in der die Konzepte der ersten Schaltung und der zweiten Schaltung kombiniert sind, um eine Schaltung zum differentiellen und bipolaren Ansteuern eines MEMS-Aktuators zu bilden.
• 15 eine beispielhafte Ausführungsform eines MEMS, hier speziell als Mikroscanner.

This shows:

• 1 as a starting point for explaining the first circuit 2A : a conventional circuit for driving a capacitive actuator with a regulated boost converter;
• 2A a first exemplary embodiment of the first circuit, which enables unipolar control of the actuator;
• 2 B a comparison of the circuits from the 1 and 2A ;
• 3 a diagram to show a current curve over time through the inductance of the circuit 2A /2B during their operation, while the magnetic energy is built up in the inductance;
• 4 an exemplary embodiment of a control device for controlling a first circuit, in particular according to 2A .
• 5 a second exemplary embodiment of the first circuit, which enables bipolar control of the actuator;
• 6 an exemplary time course of the configuration of the switching device of the circuit 5 , especially the switching states of their individual switches; and
• 7 as a starting point for explaining the second circuit 8th : a conventional circuit for controlling a MEMS actuator for driving an oscillatory MEMS, in which a MEMS capacity of the MEMS actuator is reloaded using a half bridge using two supply voltages of opposite polarity;
• 8th a first exemplary embodiment of the second circuit, with a pauseable resonant circuit and with a high-voltage source for providing a supply voltage for the circuit;
• 9 a qualitative representation of the curves of the voltage at the MEMS capacitance of the resonant circuit and the charging current to be supplied by the high-voltage source in the circuit 8th ;
• 10 a second exemplary embodiment of the second circuit with a pauseable resonant circuit and with a high-voltage source inductively coupled to the resonant circuit via a coupled pair of coils to provide a supply voltage for the circuit;
• 11 a third exemplary embodiment of the second circuit with a pauseable resonant circuit and with a resonant circuit capacity divided into two separate MEMS capacitances;
• 12 a first exemplary embodiment of a circuit in which the concepts of the first circuit and the second circuit are combined to form a circuit with a unipolar boost converter and a pauseable resonant circuit;
• 13 a second exemplary (bipolar) embodiment of a circuit in which the concepts of the first circuit and the second circuit are combined to form a circuit with a bipolar step-up converter and a pauseable resonant circuit; and
• 14 a third exemplary (bipolar) embodiment of a circuit in which the concepts of the first circuit and the second circuit are combined to form a circuit for differentially and bipolarly driving a MEMS actuator.
• 15 an exemplary embodiment of a MEMS, here specifically as a microscanner.

In the figures, the same reference numerals regularly designate the same, similar or corresponding elements (except in some cases when naming switching devices). Elements shown in the figures are not necessarily drawn to scale. Rather, the various elements shown in the figures are reproduced in such a way that their function and general purpose are understandable to those skilled in the art. Connections and couplings between functional units and elements shown in the figures can also be implemented as indirect connections or couplings, unless expressly stated otherwise. The control or control device can in particular be implemented using hardware, software or a combination of hardware and software.

Exemplary embodiments of the first circuit

• Die Schaltung 100 aus 1 entspricht einem typischen Aufbau eines asynchronen Hochsetzstellers (engl. DC/DC-Converter) aus dem Stand der Technik und wird hier zu Referenzzwecken erläutert, insbesondere um wichtige Unterschiede gegenüber lösungsgemäßen Schaltungen kenntlich zu machen.

Explanations of exemplary embodiments of the first circuit now follow, initially starting from the conventional circuit 100 1 is assumed:

• The circuit 100 off 1 corresponds to a typical structure of an asynchronous step-up converter (DC/DC converter) from the prior art and is explained here for reference purposes, in particular to highlight important differences compared to circuits according to the solution.

A voltage source provides a supply voltage Uv as a direct voltage and thus feeds an inductor (coil) L when a circuit is closed by the inductors. The resistance R _L represents the ohmic resistance of the inductance in the sense of an equivalent circuit and is not relevant in the context of further discussion of the circuit(s).

In a first phase of operation of the circuit, the circuit is closed by the inductance L by switching the field effect transistor T to conduction. This is done via a regulator Reg, which controls the transistor T accordingly via its gate. As the current flows through the inductance L, it creates a magnetic field in which energy provided by the supply voltage Uv is stored (in the form of magnetic energy).

If the transistor T is now switched off in a second phase by the controller Reg, the inductance L tries to maintain its magnetic flux despite the interruption of the previous circuit in accordance with Lenz's rule or the law of induction by inducing a voltage so that it The current generated thereby creates a magnetic field that counteracts the change in the magnetic flux. The induced voltage leads in particular to the diode D being switched in the forward direction above its threshold voltage and the generated current fed (at least in part in addition to the supply voltage Uv) from the magnetic field of the inductor L can flow into the buffer capacitance C, so that an output voltage is formed there U _A builds up above the buffer capacity C. The diode acts like a switch here.

The generation of the output voltage U _A is regulated, for which purpose a control loop with a voltage divider made up of resistors R ₁ and R ₂ and an operational amplifier OP is provided, the output of which is electrically connected to an input of the regulator Reg in order to close the control loop. To control the regulator Reg, the voltage occurring at the center tap of the voltage divider is compared with a fixed reference voltage V _ref using the operational amplifier OP and, depending on the result of the comparison, a variable frequency or a variable duty cycle (alternative German terms are “dust cycle” and “ Control level") of an output signal from the regulator Reg, with which the transistor T is controlled. This allows you to control the output voltage Design U _A on the buffer capacitor C to a substantially constant value, which depends in particular on the reference voltage V _ref .

The output voltage U _A can now be used as a driver voltage in order to activate an electrical connection to a MEMS actuator by closing a switch S ₁ in order to drive it. The MEMS actuator can - as shown - in particular have a MEMS capacitance C _M and in particular be a piezo actuator in which the MEMS capacitance C _M acts as a piezo element together with a piezo material arranged between its two electrodes of different poles. By means of a switch S ₂ connected in parallel to the MEMS capacitance C _M , the MEMS capacitance C _M can be discharged again, in particular to 0V. By appropriately controlling the switches S ₁ and S ₂ , an excitation frequency for the MEMS actuator can be determined with which the MEMS capacitance C _M oscillates back and forth between a charged and an uncharged state and accordingly switches the MEMS actuator into an oscillating one mechanical movement, which in turn can be used to drive a mechanical movement of another component. The switches S ₁ and S ₂ can in particular also be implemented by transistors.

The high voltage that can be generated by the circuit 100 can in particular be up to 200 V at a frequency of up to 100 kHz, so that the switches S ₁ and S ₂ must then be designed accordingly as high-voltage switches. If the buffer capacitance C is charged with a constant voltage source for the supply voltage Uv, as is the case with the circuit 100, the theoretical efficiency is due to the supply of the MEMS capacitance C _M from the buffer capacitance C and the resulting appearance of the so-called “capacitor -Paradoxes”, however, a maximum of only 50%. The remaining part of the applied energy occurs as power loss, in particular in the resistance of the (high-voltage) switch S1, the ohmic resistance RL of the coil and the supply lines as power loss.

• - Geringer Wirkungsgrad aufgrund des Kondensator-Paradoxons
• - Permanentes Schalten des Transistors T, zum Nachliefern der im Mittel verbrauchten Ladung zum periodischen Umladen der MEMS Kapazität C_M (Führt zu höherer Gesamtleistungsaufnahme durch Schaltverluste und kann außerdem zu Rauschen in anderen Schaltungsteilen führen)
• - Verhältnismäßig hohe Leistungsaufnahme aufgrund der permanenten Regelung der Ausgangsspannung
• - Großes Systemvolumen (Benötigt eine Regelung der Ausgangsspannung und einen Hochspannungsschalter S₁, was zu hohen Regel- und Schaltverlusten führt)
• - Hohe Schaltungskomplexität insgesamt
• - Benötigt analoge Baugruppen zur Gewährleistung der Regelstabilität des Hochsetzstellers
• - Benötigt einen Hochspannungsschalter S₁, welcher aufwendig aufgebaut werden muss (z.B. Bootstrap-Schaltung o.Ä.) und somit nicht energieeffizient ist.

Typical properties of such a conventional circuit 100 are therefore:

• - Low efficiency due to the capacitor paradox
• - Permanent switching of the transistor T, to replenish the average consumed charge for periodic recharging of the MEMS capacity C _M (leads to higher total power consumption due to switching losses and can also lead to noise in other circuit parts)
• - Relatively high power consumption due to the permanent regulation of the output voltage
• - Large system volume (Requires output voltage regulation and a high voltage switch S ₁ , which leads to high regulation and switching losses)
• - High overall circuit complexity
• - Requires analog modules to ensure the control stability of the boost converter
• - Requires a high-voltage switch S ₁ , which has to be constructed in a complex manner (e.g. bootstrap circuit or similar) and is therefore not energy efficient.

2A shows, on the other hand, a first exemplary embodiment 200 of a first circuit with which one or more of the aforementioned disadvantages can be reduced or even avoided. In 2 B is illustrated as part of a comparison 205 of the circuits 100 and 200, which circuit components can be saved in the circuit 200.

In contrast to circuit 100, the transistor T is no longer controlled by a controller (closed-loop) but by a controller (open-loop) Ctrl using a control signal Q and the charging current does not flow into a buffer capacity C, from which it then flows over time Subsequently, the MEMS capacitance C _M is charged, but rather it flows directly without capacitive buffering into the MEMS capacitance C _M of the actuator, in particular the MEMS actuator, in order to build up a drive voltage U _M above the MEMS capacitance C _M.

The MEMS capacitance C _M is designed as a component of the actuator, so that it forms a component of an electro-mechanical converter of the actuator, the converter being configured to convert electrical energy stored in the MEMS capacitance C _M into at least one mechanical quantity for driving a Movement of the actuator to convert. The actuator can in particular be a piezo actuator or piezo element, in which a piezoelectric material is arranged between the electrodes of the MEMS capacitance C _M in such a way that when an electrical voltage U _M occurs between the electrodes in the associated one electric field and deforms according to the inverse piezo effect, whereby electrical energy is converted into mechanical energy.

The circuit 200 has a switching device, which includes the transistor T, the diode D and the switch S _{2 '} . Optionally, this can already be done 1 known further switches S ₂ may be present in order to be able to optionally discharge the MEMS capacitance C _M directly to ground, in particular after energy recovery into a supply-side buffer capacitor C _B. Assuming that the supply voltage is x, for example 3V, then using the switch S ₂ an additional voltage change increased by x could be generated across the MEMS capacitance C _M. However, the switch S ₂ should only be closed for a short time in order to avoid “charging” the inductance L by a current fed from the supply voltage Uv. Alternatively, the supply voltage Uv can instead be decoupled from the inductance L during the discharge of the MEMS capacitance C _M by an optionally available further switch (not shown).

How in particular with regard to 2 B results, the circuit 200 has a significantly lower complexity compared to the circuit 100 with significantly higher efficiency, in particular due to the avoidance of the (high-voltage) switch S ₁ , the buffer capacitor C and the associated capacitor paradox as well as the control including the associated control loop with the voltage divider R ₁ , R ₂ , the operational amplifier OP, the regulator Reg and its switching frequency generation function for the transistor T.

• Ist der Transistor T mittels einer entsprechenden Ansteuerung durch die Steuerung Ctrl durchgeschaltet („erste“ Schaltungskonfiguration), so ist dadurch ein erster Strompfad durch die Induktivität L freigeschaltet, um einen von der Versorgungsspannung Uv gespeisten ansteigenden Stromfluss durch die Induktivität L zu bewirken. Dabei steigt der Strom durch die Induktivität L (zunächst näherungsweise linear) an. Der Widerstand R_L soll hierbei (im Sinne eines Ersatzschaltbilds) den Wicklungswiderstand der Induktivität L (Spule) repräsentieren.

How the circuit works 2A /2B can be described as follows:

• If the transistor T is switched on by means of a corresponding control by the control Ctrl (“first” circuit configuration), a first current path through the inductance L is thereby enabled in order to cause an increasing current flow through the inductance L, fed by the supply voltage Uv. The current increases through the inductance L (initially approximately linearly). The resistance R _L should represent (in the sense of an equivalent circuit) the winding resistance of the inductor L (coil).

After the time t _L , the transistor T is switched off (“second” circuit configuration), so that a capacitive-unbuffered second current path between a first pole of the inductance L and the MEMS capacitance C _M is enabled, via which the MEMS capacitance C _M is charged directly by means of a current flow fed at least in part by the inductance L through the diode D, which is then polarized in the forward direction, to a first voltage which is equal to or higher in magnitude than the supply voltage Uv. The magnetic energy stored in the inductance L is broken down and directly converted into the electrical energy that builds up in the MEMS capacitance C _M.

If you look at the time profile 300 of the current flowing through the inductor L during the first circuit configuration, this can be seen, as in 3 illustrated by the following relationship: $$I\left(t\right)=I_0\left(1-e^{-\frac{R}{L}t}\right)$$

Here, R corresponds to the sum of the parasitic series resistances of the inductance L and the track resistance of the switched-on transistor T (the intervening conductor tracks are idealized here as having only a negligible resistance) and Uv is again the supply voltage, which at the same time corresponds to the voltage drop across this series circuit. I ₀ is a maximum current intensity (limit current) to which the charging current I(t) asymptotically approaches over time. The limit current is calculated as: $$I_0=\frac{U_v}{R}$$

To simplify equation (2), it can be linearized at the origin at time t = 0 by its derivative: $$\frac{dI\left(t\right)}{dt}=\frac{I_{0}R}{L}{e}^{-\frac{R}{L}t}$$

At time t = 0 this relationship simplifies to: $$\frac{dI\left(0\right)}{dt}=\frac{I_{0}R}{L}$$

By inserting (3) into (5), the linearization at time t _L , at which the switch to the second circuit configuration occurs, results in the current I through the inductance: $$I\left(t_L\right)\approx \frac{U_v}{L}{t}_L$$

The stored energy E in the inductance L at time t = t _L results from: $$E_L\left(t_L\right)=\frac{1}{2}L{I}^2\left(t_L\right)$$

Correspondingly, the energy E _M of the MEMS capacitance C _M applies, where U _M is the capacitor voltage above C _M : $$E_M=\frac{1}{2}{C}_{\mathrm{<figure-callout\; id="2"\; label="M\; U\; M"\; filenames="DE102022129340B3\_0012.png,DE102022129340B3\_0014.png"\; state="\{\{state\}\}">M</figure-callout>}}{U}_M^{}{}_2^{}$$

If you equate the two equations (7) and (8) and replace I(t _L ) with the expression from equation (6), this results in the voltage U _M , to which the MEMS capacitance C _M due to the energy transfer is charged by the inductance L, to: $$U_M\approx \sqrt{\frac{1}{L{C}_M}}{U}_v{t}_L$$

The voltage U _M across the MEMS capacitance C _M scales to a good approximation proportionally to the time period in which the transistor is switched on, also proportionally to the supply voltage Uv, and root-shaped to the reciprocal of values for the inductance L and the MEMS Capacity C _M . This approximation is particularly valid if the sum of all parasitic resistances (e.g. series resistance of the coil, series resistance of the MEMS capacitance C _M and track resistances) are comparatively small in absolute terms. Otherwise, these ultimately led to a lower charging voltage of the MEMS capacitance C _M , since the energy stored in the coil is not only transferred to the MEMS capacitance, but is also partially converted into heat.

The voltage U _M across the MEMS capacitance C _M can therefore be viewed at least approximately as a linear function of the time period t _L. Since all components within the circuit, in particular L and C _M , are known, the output voltage U _M can be set solely via the controllable switch-on time t _L of the transistor T. As a result, the regulator Reg can be omitted, which leads to a significant simplification of the circuit 200 compared to the conventional circuit 100.

The switch S ₂ for discharging the MEMS capacity C _M can either be corresponding 1 be connected in parallel to C _M (third current path) or - as shown - in a fourth current path leading back to the supply voltage source (then referred to as switch S _{2 '} to identify this different arrangement). The supply voltage source (but not the second current path between inductance and MEMS capacitance C _M ) is buffered via a buffer capacitor C _B in which the charges flowing back via the switch S _{2 '} when C _M is discharged are temporarily stored and reused for a further activation cycle of the actuator can be. In this way, the efficiency of the circuit 200 can be further increased.

4 shows an exemplary embodiment 400 of the control device Ctrl for controlling a circuit according to the solution, in particular according to 2A . It serves to control the switch-on time or duration of the transistor T and thus also the output voltage U _M and is equipped with a delay chain 405 realized with several delay elements 405-1, ..., 405-n connected in series, a multiplexer 410 and a flip-flop.

In the present example, n = 255 is chosen. The delay elements 405-1,...,405-255 can be made from standard cells or “customized”, especially application-specific, using analog circuit technology. The required delay time for each individual delay element can be calculated from the quotient of the maximum required switch-on time and the number of delay elements. In the example, for the sake of simplicity, the same delay period of 8 ns was selected for all delay elements 405-1,...,405-255.

An analogue version has the particular advantage that the delay time of each individual delay element can be set individually via current control and can therefore be optimally adjusted for any MEMS capacitors (with different capacitance values and output voltages).

Each clock of a clock signal CLK applied to the control device 400 is thus divided equally according to the number of delay elements 405-1,...,405-255.

By means of a selection signal SEL applied to the multiplexer 410, the desired stage of the delay chain can be selected, which is output to the R input of the RS flip-flop 415. If the clock signal CLK is at level “1” or “high”, the output signal Q (e.g. with level “1”) switches the transistor T conductive. However, as soon as the output signal of the multiplexer 410 subsequently changes (for example to level “1”) according to the selected delay, the output signal Q changes in such a way (for example to level “0”) that the transistor T is blocked. By selecting the delay using the selection signal SEL, the time period t _L can be set during which the inductance L is “charged” with magnetic energy. Since the level of the voltage U _M across MEMS capacitance C _M in turn depends on the time period t _L , the level of the voltage U _M and thus the activity of the actuator can be controlled using the selection signal SEL.

In 5 a circuit 500 for bipolar control of an actuator with a controlled step-up converter is shown as a second exemplary embodiment.

In the circuit 500, which represents a modification or further development of the circuit 200, the switching device is further set up, repeatedly and temporarily in a period in which the second pole lying between a first pole of the inductance L and the MEMS capacitance C _M Current path is not activated, a fourth current path between the MEMS capacitance and a second pole P ₂ of the inductance L, which is electrically opposite in polarity to the first pole P ₁ , is to be activated in such a way that the MEMS capacitance C _M is switched to a second voltage with a polarity of the first voltage of opposite polarity is charged.

For this purpose, the switching device of the circuit 500 has four switches S ₁ to S ₄ . The switch S ₁ lies in the current path between the supply voltage Uv and the second pole P ₂ of the inductance L. The switch S ₂ lies in the first current path between the first pole P ₁ of the inductance L and ground. He can in particular - as in 2A - be realized by a transistor T (or several transistors and / or diodes). The same applies to all other switches. The third switch S ₃ is located in the second current path between the first pole P ₁ of the inductance L and the MEMS capacitance C _M. The fourth switch S ₄ is located in a further (“fourth”) current path between the MEMS capacitance C _M and the supply voltage Uv or its buffer capacitor C _B and corresponds to the switch S _{2 '} 2 B .

Optionally, a further switch S ₅ can be provided between the second pole P ₂ and ground.

The functionality of circuit 500 is in 6 based on the time course 600 of the configuration of the switching device of the circuit 500, in particular the switching states of its individual switches S ₁ to S ₄ .

The switching states of the switching device are gradually set into different switching states by a control (not shown) over time in accordance with the following sequence with the successive time intervals t ₀ to t ₆ , where in the diagrams “1” is a closed switch and “0” is a closed switch indicates that the switch is open and the sequence is run through at least once: time interval AROUND _​ S1 _​ S2 _​ S3 _​ S4 _​ before t ₀ Idle 0 0 0 0 _t0 0 (charging coil) 1 1 0 0 _t1 +V 1 0 1 0 Idle 0 0 0 0 _t2 +V↦V ₁ 1 0 0 1 _t3 +V ₁ ↦0 0 1 1 0 Idle 0 0 0 0 _t4 0 (charging coil) 1 1 0 0 _t5 -V 0 1 0 1 Idle 0 0 0 0 _t6 -V↦0 0 1 1 0

In 6 a special case is shown in which this sequence is repeated periodically (the transitions between the successive periods P are marked by vertical dashed lines). As shown in the table (but in 6 not illustrated), after each charge or discharge of the MEMS capacitance C _M , a rest state is established in which all switches are open (“idle” state) and until a point in time at which the inductor L has to be charged again the MEMS capacitance C _M is “floating”, meaning that it itself does not have a defined electrical potential due to the lack of a connection to a defined electrical potential. This serves to prevent the charge stored in the MEMS capacitance C _M during charging from flowing away again, in particular towards the supply source, or the MEMS capacitance C _M that has just been discharged from being (partially) charged again immediately. Conversely, this also means that the control device should be designed in such a way that the relevant switch or switches (eg S ₃ ) are opened immediately as soon as the energy of the coil has been completely used up. Alternatively, this function can be taken over by a corresponding design of the switch itself.

Before the time interval t ₀ , all switches are open (“idle” state) and the MEMS capacitance C _M therefore has no defined electrical potential (floating). In the time interval t ₀ , the “first” circuit configuration is present in which only the switches S ₁ and S ₂ are closed, so that the first current path is closed by the inductance L and due to a current fed by the supply voltage Uv along the first current path in the Inductance L creates a magnetic field with the associated magnetic energy. The coil is thus “charged” with energy.

During the transition to the subsequent time interval t ₁ , with switch S ₁ still closed, switch S ₂ is opened and switch S ₃ is closed instead, so that a "second" circuit configuration is then present in which the second current path extends from a first pole of the inductor L via the closed switch S ₃ up to the MEMS capacitance C _M is enabled, so that the magnetic energy now stored in the inductance L causes a current flow along the second current path, by means of which the MEMS capacitance C _M is charged to the positive voltage U _M = +V becomes.

This is followed by a (not in 6 illustrated) Idle state, in which all switches are open to prevent the charge now stored in the MEMS capacitance C _M from flowing back to the voltage source for the supply voltage U _V.

In the subsequent time interval t ₂ (which is optional), the switch S ₃ is opened again and the switch S ₄ is closed instead, so that a further current path is activated via the switch S ₄ (corresponds in particular to the claimed "fourth" current path), via which the MEMS capacity C _M is at least partially discharged into the buffer capacity C _B (for buffering the supply voltage Uv) to a lower voltage U _M = +V ₁ . “Charge recycling” can be carried out in the sense that part of the charge of the buffer capacitance C _B can be used again for the next build-up of a magnetic field in the inductance L and so the efficiency of the circuit 500 can be increased.

Alternatively, by closing the switches S ₂ and S ₄ with the switches S ₁ and S ₃ open, charge recovery from the MEMS capacitance C _M can be used directly by causing a corresponding current through the inductance L to build up magnetic energy in the inductance L ( not illustrated).

In the time interval t _3, only the switches S ₂ and S ₃ are closed, so that the MEMS capacity C _M can be completely discharged to ground (this step can be omitted in the aforementioned alternative, since the MEMS capacity C _M is already there in the time interval t ₂ is discharged).

It follows again (not in 6 illustrated) “Idle state in which all switches are open to prevent the MEMS capacity C _M from being (partially) charged again in an uncontrolled manner.

During the subsequent time interval t _4, only the switches S ₁ and S ₂ are closed, so that, as in the time interval t ₀ , the inductance is charged with magnetic energy via the first current path. The current flow through the inductance L is fed from the supply voltage Uv and proportionally from the buffer capacitance C _B.

In the time interval t _5, with the switch S ₂ still closed, the switch S ₁ is opened and the switch S ₄ is closed, so that charge flows from the MEMS capacitance C _M via S4 through the inductance L and via S ₂ , due to the tendency of the inductance L, to maintain the original current flow through it (Lenz's rule), the current flow stops until the MEMS capacitance C _M is charged to a negative voltage value, the amount of which in particular corresponds to the positive voltage value +V and is therefore at -V can.

It follows again (not in 6 illustrated) Idle state, in which all switches are open to prevent the charge now stored in the MEMS capacitance C _M from flowing back to the voltage source for the supply voltage Uv.

Finally, in the time interval t ₆ only the switches S ₂ and S ₃ are closed again, so that the MEMS capacitance C _M can be completely discharged to ground to 0V. A new cycle can then take place with the sequence running through again.

The optional switch S ₅ can be used in particular as follows in order to be able to recover charges at negative voltages, analogous to the previously described charge recovery with positive voltages: If the MEMS capacitance C _M is to be discharged from -V to 0, for example, S ₅ and S ₃ are closed. Now a current builds up again in the inductor L.

If the MEMS capacitance C _M is empty, S ₅ and S ₃ can be opened immediately and S ₁ and S ₂ can be closed instead in order to allow the current in the inductance L to increase further. Then everything takes the further course described above.

Exemplary embodiments of the second circuit

• Die Schaltung 700 aus 7 stellt eine sogenannte Halbbrückenschaltung dar. Sie verfügt über zwei Versorgungsspannungsquellen 705 und 710, die zueinander komplementäre Spannungen liefern. Der zentrale Schaltungsast der Schaltung 700 weist eine mittels der Halbbrückenschaltung zu treibende Komponente auf, im vorliegenden Beispiel einen kapazitiven MEMS-Aktuator, wie etwa einen Piezoaktor. Die MEMS-Kapazität des MEMS-Aktuators ist hier als C_M bezeichnet. Ein in der Realität auftretender Ohm'scher Widerstand des zentralen Schaltungsasts ist, hier im Sinne eines Ersatzschaltbilds, durch den Widerstand R repräsentiert, der im Rahmen der weiteren Erläuterungen jedoch keine Rolle spielt.

Further explanations of exemplary embodiments of the second circuit now follow, initially starting from the conventional circuit 700 7 is assumed:

• The circuit 700 off 7 represents a so-called half-bridge circuit. It has two supply voltage sources 705 and 710, which supply complementary voltages to one another. The central circuit branch of the circuit 700 has a component to be driven by means of the half-bridge circuit, in the present example a capacitive MEMS actuator, such as a piezo actuator. The MEMS capacity of the MEMS actuator is referred to here as C _M. An ohmic resistance of the central circuit branch that occurs in reality is represented, here in the sense of an equivalent circuit diagram, by the resistor R, which, however, plays no role in the further explanations.

Furthermore, the circuit has two switching devices 715 and 725, which can each be controlled by an assigned control voltage source 720 or 730 of variable control voltage, so that depending on this respective control voltage, the switching device (e.g. switch or switching transistor) 715 or 725 assigned to it Current path between the assigned supply voltage source 705 or 715 and the MEMS capacitance C _M continuously switches or interrupts. By alternating temporary continuous switching of the two current paths through the switching devices 715 and 725 The MEMS capacitance C _M can therefore be alternately charged to a positive or a negative voltage V+ or V-, whereby the MEMS actuator can execute or drive a corresponding alternating movement.

durch die Versorgungsspannungsquellen 705 und 710 aufgebracht werden.However, this type of circuit is not very energy efficient. On average, the circuit 700 must have the total power during operation $$P_{tOtal}=C_M\cdot {\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="DE102022129340B3\_0012.png,DE102022129340B3\_0014.png"\; state="\{\{state\}\}">U</figure-callout>}}^2\cdot f$$

are applied by the supply voltage sources 705 and 710.

Here C _M describes the capacitance value of the MEMS capacitance, U the peak-to-peak voltage across the MEMS capacitance and f the frequency of the resulting square-wave voltage. In the example of a microscanner as MEMS with a typical MEMS capacity of its actuator for driving the deflection element of 100 pF, a voltage swing of 200 V (±100 V) and a frequency of 25 kHz, this would result in a theoretical power consumption of 100 mW.

A first reason for the rather low energy efficiency of the circuit 700 is that due to the so-called “capacitor paradox” or “two-capacitor paradox” that occurs here and is known from general circuit technology (see https://en.wikipedia .orq/wiki/Two capacitor paradox) at least 50% of the power consumed when charging or recharging the MEMS capacity C _M is converted directly into heat. This is also the case if the line resistance (e.g. also R) becomes infinitesimally small.

A second reason is that the remaining portion of the supplied power is required to build up the different energy levels in the MEMS capacity C _M , ie for the alternating recharging, although charge flowing out of the MEMS capacity C _M during recharging is counteracted Mass or through the voltage sources is derived without being recovered for further use.

8th shows a first exemplary embodiment 800 of the second circuit, which enables bipolar control of the actuator, more precisely the MEMS capacitance C _M . However, a single supply voltage source 805 is sufficient here, the structure of which can correspond in particular to the supply voltage source 705 and supplies a DC voltage as the supply voltage Uv of the circuit 800, in particular at a feed point E ₁ . Typically, given the voltage requirement of the actuator, this is a high-voltage source (in the present context, a voltage source that can deliver a supply voltage that is above the typical supply voltages of logic circuits, in particular semiconductor circuits). In terms of magnitude, the supply voltage can in particular be greater than 10 V, in particular also at or above 100 V.

Instead of the second supply voltage source 710, the circuit 800 contains an inductance Ls (“resonant circuit inductance”), which forms a resonant circuit together with the MEMS capacitance C _M (and R) and a switching device 825. The switching device 825 can in particular correspond in structure to one of the switching devices 715 and 725 described above. The resonant circuit can be electrically connected via a switching device 815 to the feed point E ₁ fed by the supply voltage source 805 in order to transfer electrical energy from the supply voltage source 805 into the resonant circuit when the switching device 815 is closed.

If the switching device 825 were not present or permanently closed, then the oscillation frequency of the oscillating circuit would be given by its resonance frequency f ₀ , which is determined by the values of C _M and Ls according to relationship (1) (see above).

Especially in the case of microscanners, typical resonance frequencies of deflection elements (mirror plates) are in the range of up to a maximum of 100 kHz. The capacity of the piezoelectric material is typically in a range of up to approximately 150 pF. First and foremost, one could now choose a coil with a suitable inductance value as the resonant circuit inductance Ls, so that the resonant frequency f ₀ of the electrical resonant circuit corresponds exactly to the resonant frequency of the deflection element.

However, it turns out that according to the relationship (1), solved for L, impractically large inductance values result: $$L_S=\frac{1}{{\left(2\pi f_0\right)}^2\cdot C_M}=\frac{1}{{\left(2\pi \cdot 100kH\mathrm{e.g}\right)}^2\cdot 150pF}=16.9mH$$

However, such large inductance values for Ls in conjunction with small winding resistances would take up a lot of space and would therefore be unfavorable in products in which the smallest possible design of the MEMS is important, such as AR/VR glasses. The smaller the resonance frequency f ₀ and/or the value for C _M is specified, the larger the necessary inductance Ls becomes. At f ₀ = 30 kHz and C _M = 100 pF, Ls would already have a value of almost 300 mH.

If Ls has to be kept small, especially for reasons of space, a circuit implementation with a classic, permanently closed resonant circuit is therefore unfavorable or even impossible.

As in 9 illustrated using the current and voltage curves 900 on the MEMS capacitance C _M , the operation of the circuit 800 can therefore take place in particular as follows, with a controller (not shown), such as a computer program-controlled microcontroller or a hard-wired control circuit, for controlling the switching devices is used: First, with the switching device 815 closed and the switching device 825 open at the same time, a current path from the supply voltage source 805 is activated via the initially uncharged MEMS capacitance C _M in order to charge the MEMS capacitance C _M for the first time using a charging current I from the supply voltage source 805 Load voltage level +V. If the charging time is sufficient, the voltage across the MEMS capacitance C _M rises to the level of the supply voltage +V = Uv (see detail section from 9 ). The resonant circuit is now supplied with energy and begins to oscillate in the sense of a damped oscillation after the switching device 815 is opened and the switching device 825 is closed. However, this oscillation is modulated and thus changed to a lower oscillation frequency by opening the switching device 825 for a certain portion of the oscillation period in each oscillation period when the voltage U _M at the MEMS capacitance C _M just reaches a maximum and thus The energy present in the resonant circuit, which oscillates back and forth between C _M and Ls, is currently, at least largely, stored as electrical energy in C _M. The time portion of the oscillation period can in particular be approximately 50%, i.e. correspond to approximately half the period duration. More precisely, it would be 50% minus the time that the resonant circuit needs to reload between two voltage levels.

In the meantime, energy lost in the resonant circuit, in particular on the resistor R and the lines due to, in particular ohmic, losses (hence damped oscillation), can now be done by regularly temporarily closing the switching device 815 and opening the switching device 825 by recharging C _M with a temporary charging current I can be compensated. This recharging preferably takes place when the voltage U _M across the MEMS capacitance C _M has just reached its maximum value in the current oscillation period. However, this does not necessarily have to be done in every oscillation period or after every reloading. Rather, it is also possible to reload only after multiple reloading in the meantime or only after several oscillation periods, for example every mth time, with m ∈ ℕ, for example with m = 2.

Recharging can generally take place both with a positively polarized high-voltage source at times when the resonant circuit is paused and the voltage across the MEMS is currently at its maximum, as well as with a negatively polarized high-voltage source at times when the resonant circuit is paused and the voltage across the MEMS capacitance C _M is just minimal. In this case there is a somewhat more uniform voltage signal across the MEMS capacitance C _M .

The resonant circuit is therefore paused regularly in order to maintain its oscillation frequency fs, which is compared to the resonant frequency f ₀ of the resonant circuit (in the permanently closed case) determined by the values of C _M and Ls according to relationship (1) (see above). is reduced, and on the other hand to recharge the energy lost during the electrical oscillation.

A significant advantage of this circuit is that due to the direct feeding of the supply voltage Uv into the MEMS capacitance C _M , the disadvantageous effect of the capacitor paradox can be reduced based on the principle of staged, in particular adiabatic, charging and line losses can be reduced. In addition, the charges that flow when C _M is reloaded no longer simply have to be diverted to ground, but are still available for the continued electrical oscillation in the resonant circuit. This results in a higher efficiency and therefore a higher energy efficiency than with the 700 circuit 7 to reach.

In addition, the values of C _M and Ls can be chosen to be smaller than would be required in the case of a classic resonant circuit to achieve the desired oscillation frequency f _S. In this way, particularly space-saving circuit implementations can be achieved and dependencies on component tolerances can also be eliminated.

10 illustrates a second exemplary embodiment 1000 of the second circuit, with a pauseable resonant circuit and with a high-voltage source 1005 inductively coupled to the resonant circuit via a coupled coil pair to provide a supply voltage Uv for the circuit 1000. The voltage source 1005 can alternatively, depending on the turns ratio of the coil pair, also be a low voltage source.

Specifically, the circuit 1000 has two galvanically decoupled circuit parts, preferably including decoupled first and second masses 1045 and 1050, which are inductively coupled via a pair of coils consisting of a first coupling coil L _V and a second coupling coil L _S. The second coupling coil L _S also represents the resonant circuit inductance of the resonant circuit. The coupling coils also each have an ohmic resistance R _V or R _S , which is shown here in the sense of an equivalent circuit diagram.

The first circuit part has a circuit loop which, in addition to the high voltage source 1005 and the first coupling coil Lv (with Rv), also contains a first switching device 1015 with an assigned control voltage source 1020 for its time-variable control. Depending on the current switching state of the switching device 1015, the loop and thus the current path through the first coupling coil Lv is closed or interrupted, so that the inductive effect of the first coupling coil L _V and thus an inductive energy transfer to the second coupling coil Ls im is via the control voltage source 1020 Oscillating circuit can be controlled.

In addition to the second coupling coil Ls provided as a resonant circuit inductance, the resonant circuit in turn has the MEMS capacitance C _M of a MEMS actuator to be controlled (along with its ohmic resistance R) and a second switching device 1025 with an assigned control voltage source 1030 for its time-variable control. According to the switching device 825 8th , the resonant circuit can be paused with the second switching device 1025.

In addition, the resonant circuit also has a circuit branch connected in parallel to the second switching device 1025 with a diode D and a third second switching device 1035 with an assigned control voltage source 1040 for its time-variable control.

If the switching devices 1015 and 1035 are open so that they interrupt the current paths running through them, while the switching device 1025 is closed, the resonant circuit is closed and “oscillates”. However, if the resulting energy losses are to be compensated for (cf. 9 ), then the switching devices 1015 and 1035 are closed and the switching device 1025 is opened.

Now, by a single current pulse (or by several consecutive current pulses with corresponding multiple closing and opening of the switching device 1015, a time-variable current, in particular alternating current, can be generated through the first coupling coil L _V , which generates an induction current in the second through inductive energy transfer via the pair of coils Circuit part causes, which runs via the switching device 1035 and is rectified via the diode D. The MEMS capacitance C _M can thus be recharged with direct current (which can be variable over time). This takes place during a period of time in which the from the previous oscillation The voltage U _M resulting in the resonant circuit is maximum over the MEMS capacitance C _M and has the same pole as the induction voltage generated in the second coupling coil L _S. If the direction of the diode is reversed, there is an analogous possibility of “recharging” the resonant circuit. when the voltage across the MEMS capacitance is just minimal. An additional current path also offers the possibility of bipolar recharging.

Instead of the DC voltage source 1005, an AC voltage source can also be used, so that the generation of DC pulses to generate a time-varying current through the first coupling coil L _V can be omitted.

11 illustrates a third exemplary embodiment 1100 of the second circuit with a pauseable resonant circuit, which consists of the circuit 800 8th emerges from the only swing there circuit capacity and at the same time MEMS capacity C _M is divided into two separate MEMS capacities C _M1 and C _M2 . In the circuit 1100, for comparison with the circuit 800, the supply voltage source 1105 corresponds to the supply voltage source 805, and the switching devices 1115 and 1125 (with associated control voltage sources 1120, 1130) correspond to the switching devices 815 and 825 (with associated control voltage sources 820 and 830, respectively) .

Due to the division of the resonant circuit capacitance between the two separate MEMS capacitances C _M1 and C _M2 in the arrangement shown, in which the resonant circuit inductance LS and the switching device 1125 are connected between the two MEMS capacitances C _M1 and C _M2 During (pauseable) oscillation of the resonant circuit, voltages U _M1 and U _M2 occur at the MEMS capacitances C _M1 and C _M2 , which are out of phase with one another and can have the same amplitude, especially with the same capacitance values. The MEMS capacitances C _M1 and C _M2 can in particular be part of the same MEMS actuator, so that a differential drive is possible. For example, the MEMS capacitances C _M1 and C _M2 can each be configured as part of a piezo actuator in such a way that they cause piezoelectric forces acting in opposite directions, in particular 180° out of phase.

Exemplary embodiments for a combination of first circuit and second circuit

As already mentioned, the previously introduced circuit types “first circuit” and “second circuit” can also be advantageously combined. While the first circuit in particular makes it possible to provide the high voltages required for the operation of actuators, in particular MEMS actuators, even without using a high-voltage source as such, and instead a low-voltage source, which can in particular be provided by a primary battery or secondary battery of a mobile device , the second circuit allows, in particular, a space-saving design of the circuit. In addition, both circuits serve to increase energy efficiency.

12 illustrates a first exemplary embodiment 1200 of such a combined circuit for controlling an actuator, in particular a MEMS actuator, for driving an oscillatory movement in a MEMS.

The circuit 1200 can be a further development or variant of the first circuit 2A are considered, so that only the differences will be discussed below.

A significant difference is that in the circuit 1200, according to the concept of the second circuit, a pauseable resonant circuit with the MEMS capacitance C _M is included as the resonant circuit capacity. The resonant circuit also contains a resonant circuit inductance Ls and a switching device S ₇ for temporarily interrupting (pausing) the resonant circuit.

To recharge the MEMS capacitance C _M , when it has reached its maximum voltage value within the current oscillation period, the resonant circuit is interrupted (paused) by means of the switching device S ₇ and by closing the further switching device S ₆ , a current path is created between the in the left part of the 12 shown boost converter circuit and the resonant circuit, in particular the MEMS capacitance C _M , closed.

The resonant circuit can therefore be supplied with energy solely by means of a low-voltage source to provide the supply voltage Uv, without the need for a high-voltage source.

The feedback loop via the switching device S _{2 '} and the buffer capacity C _B from the circuit 200 2A can also be eliminated because the energy in the resonant circuit is essentially preserved apart from the typical, especially ohmic, losses, so that buffering is no longer necessary.

13 illustrates a second exemplary embodiment 1300 of a combined circuit for controlling an actuator, in particular a MEMS actuator, for driving an oscillatory movement in a MEMS.

The circuit 1300 can be a further development or variant of the first circuit 5 are considered, so that only the differences will be discussed below.

A significant difference is that the circuit 1300 again contains a pauseable resonant circuit with the MEMS capacitance C _M as the resonant circuit capacity and a resonant circuit inductance Ls as well as a switching device S ₇ for temporarily interrupting (pausing) the resonant circuit.

To recharge the MEMS capacitance C _M , on the one hand, when it has reached its maximum positive voltage value within the current oscillation period, the resonant circuit is interrupted (paused) by means of the switching device S ₇ and by closing at least one of the switching devices S ₃ and S ₄ Current path between the in the left part of the 13 shown boost converter circuit and the resonant circuit, in particular the MEMS capacitance C _M , closed. The step-up converter circuit is configured in such a way with regard to its switch positions (e.g.: S ₁ and S ₃ closed, S ₂ and S ₄ open, or: S ₁ and S ₄ closed, S ₂ and S ₃ open) that it supplies a supply voltage to the resonant circuit , or more precisely the MEMS capacitance C _M , which has the same pole as the (positive) voltage U _M across the MEMS capacitance C _M.

On the other hand, for (additional) recharging of the MEMS capacitance C _M when it has reached its maximum negative voltage value within the current oscillation period, the resonant circuit can be interrupted (paused) again by means of the switching device S ₇ and by closing at least one of the switching devices S ₃ and S _4, a current path between the step-up converter circuit and the resonant circuit, in particular the MEMS capacitance C _M , is closed. The step-up converter circuit is configured in such a way with regard to its switch positions (e.g.: S ₂ and S ₄ closed, S ₁ and S ₃ open, or: S ₂ and S ₃ closed, S ₁ and S ₄ open) that it supplies a supply voltage the resonant circuit, or more precisely the MEMS capacitance C _M , which has the same pole as the (negative) voltage U _M across the MEMS capacitance C _M.

In the circuit 1300, too, the resonant circuit can be supplied with energy solely by means of a low-voltage source to provide the supply voltage Uv, without the need for a high-voltage source. In addition, the buffer capacity C _B can also come out of the circuit 500 5 again eliminated, since the energy in the resonant circuit is essentially preserved apart from the typical, especially ohmic, losses, so that buffering is no longer necessary.

14 shows a third exemplary embodiment 1400 of a circuit in which the concepts of the first circuit and the second circuit are combined to form a circuit for bipolar and differential control of a MEMS actuator, in particular a microscanner.

In addition to an oscillating circuit 1425, which can be interrupted by means of a switching device 1405 and can therefore be paused, the circuit 1400 has two step-up converter circuits 1415 and 1420, which here each exemplify the concept of the circuit 13 correspond and which serve to provide two different-pole, boosted supply voltages +Uv or -Uv for the pauseable resonant circuit 1425, one each at an assigned feed point E ₁ or E ₂ .

The recharging of the MEMS capacitances C _M1 and C _M2 in turn preferably takes place when they have reached their absolute maximum voltage value, which has the same polarity as the assigned supply voltage, within the current oscillation period. The resonant circuit is temporarily interrupted (paused) by means of a switching device 1415 with an assigned control voltage source 1420. The first MEMS capacitance C _M1 is thus charged in a first polarity (+) while at the same time the second MEMS capacitance C _M2 is charged in a polarity (-) opposite to the first polarity. The functionality of the circuit is identical to that of each of the polarities 13 , whereby a further index 1 or 2 is introduced here in the reference numbers in order to distinguish the components of the two, in particular identically executable, boost converters 1415 and 1420.

The control of the circuit 1400 is designed such that while the step-up converters 1415 and 1420 are working, the switching device 1405 is open, so that both step-up converters 1415 and 1420, each individually, can work separately in order to increase the MEMS capacitances C _M1 and C Charge _M2 to opposite voltage levels. If the resonant circuit is then activated, both step-up converters 1415 and 1420 are placed in the “idle” state so that they do not impair the function of the then oscillating resonant circuit 1425.

In 15 A MEMS 1500 is shown schematically, which has a microscanner system with a microscanner 1501. The microscanner 1501 has a support structure 1505 made of a semiconductor substrate in the form of a frame (chip frame), which has a deflection element (mirror) 1510 on all sides surrounds, the base of which is made of the same semiconductor substrate as the support structure 1505. The deflection element 1510 is suspended from the support structure 1505 by means of one or more spring elements, in the present example these are the two spring elements 1515a and 1515b attached to opposite sides of the deflection element 1510. This suspension is designed so that the deflection element 1055 can oscillate rotationally at least about an oscillation axis. This oscillation axis runs along the (in the picture the 15 vertical) Straight through the two attachment points of the spring elements 1515a and 1515b on the deflection element 1510. With suitable excitation, it is also possible to create an oscillation about a second oscillation axis orthogonal to the first oscillation axis, in the image of the 15 i.e. to stimulate the horizontal axis of oscillation. In particular, to promote such a two-dimensional oscillation, instead of the suspension shown here with two opposite meander-shaped spring elements, differently shaped and arranged spring elements can also be provided, in particular several spiral-shaped ones.

On each of the spring elements 1515a and 1515b there is a piezo element 1520 or 1525, whereby these piezo elements differ in terms of their piezo material and their tasks.

The first piezo element 1520 serves as a piezo actuator to drive the oscillatory movement of the deflection element 1510 and is therefore designed as a dielectric based on a first piezo material, such as PZT, which has a particularly strong piezo effect. The electrodes of the piezo element 1520, which are separated from one another by the piezo material, also form the electrodes of its MEMS capacitance C _M . With a suitable choice of the spring strengths of the spring elements 1515a and 1515b, the first piezo element 1520 is therefore suitable for enabling large deflections and thus scanning angles of the microscanner 100, in particular up to ± 90° (optical scanning angle) or even more.

The second piezo element 1525, on the other hand, serves as a piezo sensor for measuring and thus determining the time-dependent position, i.e. H. specifically the orientation or phase position of the oscillation, of the deflection element 1510.

In 15 In addition, for both piezo elements 1520 and 1525, the corresponding connection lines 1535a, b and 1545a, b as well as connection pads (bond pads) 1530a, b and 1540a, b coupled thereto are used to establish a respective electrical connection with external drive or measuring electronics, for example via wire bonds, shown. It is also conceivable that, in addition to the two shown, further piezo elements are provided as piezo actuators or piezo sensors.

An SOI (Silicon-on-Insulator) substrate serves as the basis. A SiO ₂ or another electrical passivation is produced on this substrate, on which the piezoelectric layer stacks are applied. The piezoelectric layer stacks consist of a bottom electrode, usually metal, the piezoelectric material, and a top electrode, usually metal. In addition, further electrical passivation is used between the top and bottom electrodes to prevent electrical short-circuiting.

To control the first piezo element 1520 (and optionally to process measurement signals from the second piezo element 1525), the MEMS 1500 additionally has a circuit 1550 according to one of the aforementioned circuit-related aspects of the present solution, for example according to one of 8 or 10 to 14 . Depending on the circuit used, the piezo elements can be non-differential or differential.

REFERENCE SYMBOL LIST

100

conventional regulated boost converter circuit

200

First (unipolar) embodiment of a circuit according to the solution

205

Comparison of circuits 100 and 200

300

Time course of the current through the inductor L during the first circuit configuration

400

Embodiment of a control device Ctrl

405

Delay chain

405-x

Delay elements of the delay chain 405

410

multiplexer

415

RS flip flop

500

Second (bipolar) embodiment of a circuit according to the solution

600

Time course of the configuration of the switching device of the circuit 500

700

conventional half-bridge circuit

705, 710

Supply voltage sources

715, 725

Switching devices

720, 730

Control voltage sources

800

first exemplary embodiment of the second circuit

805

Supply voltage source

815, 825

Switching devices

820, 830

Control voltage sources

900

Current and voltage curves on the MEMS capacitance of the circuit 800

1000

second exemplary embodiment of the second circuit

1005

Supply voltage source

1015, 1025

Switching devices

1020, 1030

Control voltage sources

1035

further switching device

1040

Control voltage source for switching device 1035

1045

first mass

1050

second mass

1100

third exemplary embodiment of the second circuit

1105

Supply voltage source

1115, 1125

Switching devices

1120, 1130

Control voltage sources

1200

first exemplary embodiment of a combined circuit

1300

second exemplary embodiment of a combined circuit

1400

third exemplary embodiment of a combined circuit

1405

Switching device

1410

Control voltage source for switching device 1405

1415

first boost converter

1420

second boost converter

1425

oscillating circuit

1500

MEMS

1501

Microscanner

1505

Support structure (chip frame)

1510

Deflecting element (mirror)

1515a

first spring element

1515b

second spring element

1520

first piezo element, piezo actuator

1525

second piezo element, piezo sensor

15530a, b

Connection pads for the first piezo element

135a, b

Connection cables for the first piezo element

1540a, b

Connection pads for the second piezo element

1545a, b

Connection cables for the second piezo element

C

Buffer capacity in conventional circuit

CB

Buffer capacitor for supply voltage source

CM

MEMS capacity

CM1, CM2

separate MEMS capacities

Clk

Clock signal

Ctrl

Control or control device

D

diode

E1, E2

Electrical energy feed-in points

I

charging current

I0

Limit current

L

Inductance, especially booster inductance

L.S

Resonant circuit inductance, second coupling inductance

LV

first coupling inductance

OP

operational amplifier

P

Period or period duration

P1

first pole of inductance L

P2

second pole of inductance L

Q

Output signal from Ctrl

R, S

Inputs of the RS flip-flop 415

Reg

Regulator

R1, R2

Ohmic resistors that form voltage dividers

RL, RL1, RL2

Ohmic resistance of the assigned inductance L, L ₁ or L ₂

RS, RV

Ohmic resistances of the coupling inductances, in particular ohmic resistance in the resonant circuit according to the equivalent circuit diagram

S1 - S7

Switching devices, especially switching transistors

SEL

Selection signal

T

transistor

t

Time variable

t0,...,t6

Time intervals

UA

Voltage over buffer capacity C

AROUND

Voltage over MEMS capacity

UV

Supply voltage or supply voltage source

Vref

Reference voltage

+V, -V

alternating voltage levels of U _M

Claims (16)

Circuit for controlling an actuator for driving an oscillatory movement of a mass element in a MEMS, the circuit having: an electrical resonant circuit which contains a first inductance, a first electrical MEMS capacitance and a controllable first switching device for selectively interrupting or closing the resonant circuit depending on a control of the first switching device and has a resonance frequency related to a permanently closed state of the resonant circuit; and a controller for controlling the first switching device; wherein the controller is configured to temporarily put the first switching device into a state in which it interrupts the resonant circuit during a respective oscillation period of the resonant circuit, when the voltage across the first MEMS capacitance reaches a maximum within the oscillation period, by means of a corresponding control to cause an actual oscillation frequency of the resonant circuit that is smaller than the resonance frequency. Circuit after Claim 1 , wherein: the first MEMS capacitance is designed as a component of the actuator in such a way that it forms a component of an electro-mechanical converter of the actuator; and the converter is configured to convert electrical energy stored in the first MEMS capacitance into at least one mechanical quantity for driving movement of the actuator. Circuit according to one of the preceding claims, wherein the controller is configured, in a respective oscillation period of the oscillating circuit, to put the first switching device into a state in which it interrupts the oscillating circuit when the voltage across the first MEMS capacitance within the oscillation period after a while The recharging of the first MEMS capacity during the oscillation period reaches a maximum in terms of amount. Circuit according to one of the preceding claims, wherein: the resonant circuit has, in addition to the first MEMS capacitance, a second MEMS capacitance formed separately from the first MEMS capacitance; the first and the second MEMS capacitance are connected in the resonant circuit in such a way that a first pole of the first MEMS capacitance is electrically connected to a first pole of the second MEMS capacitance via at least one switch of the first switching device and the first inductance and the respective second poles of the two MEMS capacitances are electrically connected to one another in such a way that they are kept at the same electrical potential when the resonant circuit is in operation. Circuit according to one of the preceding claims, further comprising a power supply circuit for temporarily supplying electrical energy to the resonant circuit. Circuit after Claim 5 , wherein the energy supply circuit has a second switching device which is configured, depending on a control, to temporarily connect a feed point for electrical energy to the resonant circuit in order to supply the resonant circuit with electrical energy that is supplied or can be supplied at the feed point. Circuit after Claim 6 , wherein the circuit is configured to temporarily close the second switching device in a respective oscillation period of the resonant circuit when the voltage across the first MEMS capacitance reaches a maximum within the oscillation period and the same polarity as one of the energy supply circuit is available at the feed point has set voltage. Circuit after Claim 6 or 7 , wherein the circuit is configured to temporarily connect the feed point to the resonant circuit in the respective oscillation period by means of the second switching device at a time before which two successive recharging processes of the first MEMS capacity of the resonant circuit have already taken place in the oscillation period since the last by means of the second Switching device the feed point was temporarily connected to the resonant circuit. Circuit according to one of the Claims 6 until 8th , wherein the circuit is configured to temporarily electrically connect the feed point to the resonant circuit in the respective oscillation period by means of the second switching device and thereby charge the first MEMS capacitance while the first Switching device is in a state in which it electrically isolates the first inductance from the feed point. Circuit according to one of the Claims 5 until 9 , wherein the circuit is configurable such that the amount of electrical energy supplied to the resonant circuit in at least one oscillation period is adjustable. Circuit after Claim 10 , whereby the circuit can be configured in such a way that the amount of electrical energy supplied to the resonant circuit can be set individually for each oscillation period or globally for all m-th oscillation periods, where m > 0 is a natural number. Circuit according to one of the Claims 5 until 11 , wherein the energy supply circuit has an inductive coupling device for temporarily inductively feeding electrical energy into the resonant circuit. Circuit according to one of the Claims 5 until 12 , further comprising a step-up converter which is configured to convert an input voltage applied at the feed point into a relatively higher output voltage in order to supply the resonant circuit with electrical energy based on this output voltage when the second switching device is in a state in which it temporarily electrically connects the feed point to the resonant circuit. Circuit after Claim 13 , wherein: the step-up converter has a step-up converter circuit with a second inductance and a third switching device that can be controlled by the controller and a third MEMS capacitance, which is at least partially formed by the first and/or the second MEMS capacitance; wherein the third switching device is set up, depending on the control, to assume a first circuit configuration and sequentially subsequently a second circuit configuration, so that in the first circuit configuration a first current path through the second inductor is enabled in order to allow an increasing current flow fed by a supply voltage through the second inductor to effect, and in the second circuit configuration a capacitive-unbuffered second current path between a first pole of the second inductance and the third MEMS capacitance is activated in order to bring the third MEMS capacitance to a first voltage by means of a current flow fed at least in part by the second inductance to charge, which is equal to or higher than the supply voltage. MEMS, comprising: a mass element configured to oscillate; an actuator for driving an oscillatory movement of the mass element; and a circuit according to one of the preceding claims for controlling the actuator in such a way that it is caused to move the oscillatory mass element in an oscillatory movement; wherein the MEMS capacitance of the circuit is designed as a component of the actuator in such a way that it itself forms a component of an electro-mechanical converter of the actuator, and the converter is configured to convert electrical energy stored in the MEMS capacitance into at least one mechanical quantity for driving a movement of the actuator in order to drive the oscillatory movement of the mass element. MEMS Claim 15 , wherein the MEMS has a microscanner system; and the mass element is designed as a deflection element of the microscanner system configured to oscillate for deflecting electromagnetic radiation incident on the deflection element.

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