DE102015105087A1 - Electronic circuit for transmitting energy and measuring device comprising such - Google Patents

Abstract

The invention relates to an electronic circuit (1) for use in process automation, the electronic circuit (1) for transmitting energy between a first side having a first interface (23), and a second side having a first interface (23 ), wherein the first interface (23) and the second interface (24) are designed to transmit the energy, and wherein the first interface (23) and the second interface (24) as inductive Interfaces (L1, L2) are configured, comprising: the first interface (23); a class E amplifier (4), the class E amplifier (4) comprising the first interface (23); a DC-DC converter (5), the output of the DC-DC converter (5) being connected to the input of the class-E amplifier (4); and a controller (6) in a control circuit which controls constant power, with the power (P) which the class E amplifier receives at its input, as control variable (y), with a set power at the first interface (23). as a reference variable (w), and with the voltage (Vout) at the output of the DC-DC converter (5) as a manipulated variable (u). The invention further relates to a measuring device (20) comprising such a circuit (1).

Description

The invention relates to an electronic circuit for transmitting energy. The invention further relates to a measuring device comprising such a circuit.

The invention relates to the field of process automation.

The problem underlying the invention will be explained on the basis of energy and data transmission between a transmitter side (generally a higher-level unit) and a sensor side (generally a consumer).

Usually, a cable is connected to a transmitter for connection to a sensor. The connection cable to sensor often takes place via a plug connection, for example by galvanically decoupled, in particular inductive interfaces. Thus, contactless electrical signals can be transmitted. This galvanic separation has advantages in terms of corrosion protection, electrical isolation, prevention of mechanical wear of the plug, etc. By the Applicant such systems are sold under the name "Memosens".

The mentioned inductive interfaces are usually realized as a system with two coils, which are plugged into each other, for example by means of the addressed connector. Typically, both data (in both directions) and energy (from transmitter side to sensor side) are transmitted. The energy must be so high that a connected sensor is sufficiently supplied with energy and thus a permanent measuring operation is guaranteed.

The challenge of such non-contact energy and data transmission initially lies in the harsh operating and environmental conditions in the industrial environment. This requirement has the effect that the due to the environmental conditions (temperature, humidity, etc.) to be applied tolerance ranges for the components (inductances of the coils, etc.) are particularly large. For example, if assemblies are to be designed for typical temperatures at which medical equipment is sterilized (typically above 120 ° C), e.g. to reckon with considerably modified inductance values for the coils used in these assemblies at high temperatures.

Particularly noteworthy in terms of tolerances of the coupling transformer which inductively couples the coil on the transmitter side with the coil on the sensor side, or forms a transformer with these two coupled coils. In this coupling system, the mechanical pairing of the two partner coils is crucial and a large dispersion of the inductive coupling can lead to problems with the transmission behavior.

The core of the power supply is a class E amplifier. It converts a DC voltage into an AC current that flows through a first coil. Energy is supplied to the sensor via the second coil magnetically coupled to this coil. Ideally, the power output to the sensor is independent of the addressed component tolerances, the supply voltage and ambient conditions. This ensures that the sensor is fully functional at all times. If the power output fluctuates, this has negative consequences for the entire measuring point. If it is too low, the power supply of the sensor is no longer secured and a measurement can no longer be performed. If it is too high, the power consumption, ie the power which has to be provided on the transmitter side, increases. Excessive power consumption can endanger the safe power supply of the connected transmitter. This is especially relevant for two-wire devices, but also for four-wire devices.

In the still unpublished DE 10 2014 101 502 a solution by means of a power control by changing the clock frequency is described. However, clock frequency and power output behave non-linearly to each other, which may possibly lead to problems.

An alternative solution to stabilize the output is a linear regulator that makes the power output independent of the supply voltage. In addition, components that are advantageous for a constant power output can be selected for the class E amplifier. A change or even a regulation by means of changing the operating voltage of the class-E amplifier is not possible, since the output voltage of a linear regulator is usually not changeable. Although linear regulators are available with variable output voltage, but then reduced with reduced output voltage of the linear regulator and the efficiency of the circuit accordingly. However, a constant efficiency is a prerequisite for a constant power consumption.

Despite the use of a linear regulator, the power output still varies considerably. Depending on component tolerances and environmental conditions, the power output may change up to two times. Therefore, a connected sensor under all possible environmental conditions ultimately only a minimal Guaranteed performance, which can be transmitted safely. However, the energy source, such as the transmitter, must provide the maximum possible energy with a sufficiently large buffer. This is not optimal for the transmitter or the sensor.

The invention has for its object to ensure a low-energy, but safe energy transfer from a first page to a second page.

The object is achieved by an electronic circuit wherein the electronic circuit for transmitting energy between a first side with a first interface, and a second side with a, corresponding to the first interface, second interface is configured, wherein the first interface and the second Interface for transmitting the energy are designed, and wherein the first interface and the second interface are designed as inductive interfaces, comprising: the first interface; a class E amplifier; wherein the class E amplifier comprises the first interface, a DC-DC converter; wherein the output of the DC-DC converter is connected to the input of the class-E amplifier; and a controller in a closed-loop control circuit, with the power that the class-E amplifier receives at its input, as a controlled variable, with a setpoint power at the first interface as a command, and with the voltage at the output of the DC-DC converter as manipulated variable.

By using a DC-DC converter with adjustable output voltage, and the control to constant power with this output voltage as a control variable in the control loop, the efficiency of the circuit remains approximately constant, regardless of the level of the output voltage. The DC-DC converter converts a DC voltage supplied to the input into a DC voltage with a higher, lower or inverted voltage level.

If the measured power is used as a controlled variable, it is possible to correct the inevitable tolerances of the interfaces themselves, the positioning of the interfaces to each other and the disturbances in the environment.

In a further preferred embodiment, the electronic circuit also transfers digital data between the first page and the second page, and the first interface and the second interface are configured to transmit the data, the electronic circuit transferring the digital data by amplitude shift keying. As a result, a common circuit for energy and data transmission can be used and thus costs and space consumption can be reduced.

Preferably, the DC-DC converter modulates the digital data to its output. Again, no additional space is needed. In addition, high efficiencies can be achieved.

Alternatively, the class-E amplifier includes a load modulation circuit that modulates the digital data. This type of circuit is easy to implement and a common procedure.

In an advantageous embodiment, the setpoint power at the first interface is made variable as a reference variable. Thus, on the second page different consumers can be connected, each of which can consume different power. For example, a turbidity sensor as a consumer on the second side needs more power than a pH sensor. If a corresponding consumer is detected, the specifically required power is made available and the reference variable is varied accordingly.

Furthermore, the reference variable power can also be influenced by other parameters and thereby changed. To call here is the ambient temperature. For example, the temperature response of the class-E amplifier or the entire circuit can be compensated.

As mentioned, component tolerances can also be compensated. Between the first and second interface inevitably creates an air gap, which reduces the coupling. This negative effect can be largely compensated by the power control.

Furthermore, the reference variable can be adjusted depending on the operating mode of a consumer connected to the second side. One operating mode "Clear memory", "Change firmware", etc. For example, it may require more power.

The object is further achieved by the use of an electronic circuit as described above in process automation.

The object is further achieved by a process automation measuring device comprising an electronic circuit as described above.

In an advantageous embodiment, the measuring device comprises a higher-level unit, in particular a transmitter, and a consumer, in particular a sensor, wherein the parent unit is connected to the consumer via the first interface and the second interface.

Preferably, the command variable is variable and the target power at the first interface is adjustable by the parent unit.

In an advantageous development, the reference variable is adjustable depending on the type of consumer, ambient temperature, component tolerances, and / or the size of an air gap between the first interface and the second interface.

The object is further achieved by the use of a measuring device as described above in process automation.

The invention will be explained in more detail with reference to the following figures. Show it

1 the measuring device according to the invention,

2a the electronic circuit according to the invention, and

2 B the electronic circuit according to the invention in one embodiment.

In the figures, the same features are identified by the same reference numerals.

First, to a meter 20 be received in which the electronic circuit according to the invention can be applied. This is in 1 shown. Via an interface 24 a sensor communicates 22 ( "Sensor side 3 ") With a transmitter 21 ( "Transmitter side 2 "). At the transmitter 21 is a cable 25 provided, at the other end to the first interface 24 complementary interface 23 is provided. The interfaces 23 . 24 are designed as galvanically isolated, in particular as inductive interfaces which can be coupled to one another by means of a mechanical plug connection. The mechanical connector is hermetically sealed, so that no liquid, such as the medium to be measured, air or dust can penetrate from the outside.

About the interfaces 23 . 24 be data (bidirectional) and energy (unidirectional, ie from transmitter 21 to sensor 22 ) Posted. The measuring device 20 is mainly used in process automation. At the sensor 20 it is therefore about a pH, redox potential, also ISFET, temperature, conductivity, pressure, oxygen, in particular dissolved oxygen, or carbon dioxide sensor; an ion-selective sensor; an optical sensor, in particular a turbidity sensor, a sensor for optically determining the oxygen concentration, or a sensor for determining the number of cells and cell structures; a sensor for monitoring certain organic or metallic compounds; a sensor for determining a concentration of a chemical substance, for example a particular element or a particular compound; or a biosensor, eg a glucose sensor.

The circuit according to the invention with the reference numeral 1 can do both in the transmitter 21 yourself, in the cable 25 or in the sensor 22 be placed. Preferably, the electronic circuit is located in the transmitter 21 or in the cable 25 ,

The circuit according to the invention in its entirety has the reference numeral 1 and is in a schematic overview in 2a and 2 B shown. The circuit 1 is located on the transmitter side 2 , The transmitter side 2 is with the sensor side 3 , about the already mentioned first interface 23 and the second interface 24 connectable.

The electronic circuit 1 includes the following components: Voltage source VCC, DC-DC converter 5 , Controller 6 , Class E amplifier 4 , A DC-DC converter is also called a DC-DC converter.

The transmitter 21 includes the voltage source VCC, the voltage to the DC-DC converter 5 supplies. The output of the DC-DC converter 5 is with the input of the class-E amplifier 4 connected. The regulator 6 regulates the output voltage of the DC-DC converter 5 ,

The class E amplifier 4 comprises at least the components L1, L3, C1, C2 and T1. In the example shown, a field effect transistor which is driven with a frequency f. used. A person skilled in the art is also able to use bipolar transistors or other switching means. The class E amplifier 4 Converts a DC voltage at its input into an AC current that flows into the coil L1. Energy is supplied to the sensor via the second coil L2 magnetically coupled to this coil L1 22 ,

For data transfer, data is modulated. This is done by switchable load modulation circuit 7 represented in 2a , The load network is symbolized by a resistor. The load modulation circuit 7 is switched by a suitable switching means, such as a transistor ö.ä. The switching means is symbolized by a switch. The load modulation circuit 7 is connected to ground or to the supply voltage VCC (not shown).

Alternatively, a gain using DC-DC converter 5 to be used, see 2 B , In this case, for example, the data signal is converted such that a smaller gain (small output signal) corresponds to a digital "0"; a larger gain (larger output signal) corresponds to a digital "1". As a further alternative, an amplifier, as described in the German patent application DE 10 2012 110 310 will be used. The modulation of the voltage at the first coil L1 via a power source as an amplifier with a logic level-dependent output voltage has the advantage that better efficiencies can be achieved than with alternative modulation methods, such as a resistive damping of the first coil L1, and that with this method the influences of Exemplary scatters are less. If, for example, a 10% modulation amplitude is required, this can be achieved with a 10% reduction in the DC input voltage, independent of specimen scattering of the components.

By using a DC-DC converter 5 with adjustable output voltage through the regulator 6 remains the efficiency of the circuit 1 approximately constant, regardless of the magnitude of the output voltage. The result is a control loop with the following time-dependent variables: Command value w (setpoint) is the setpoint power, that of the Class E amplifier 4 which is multiplied by the efficiency of the Class E amplifier 4 is transmitted to the second coil L2. Controlled variable y is the actual power that the class E amplifier 4 receives. This is the product of a current and voltage measurement at the input of the class E amplifier 4 , symbolized by the reference P. Manipulated variable u is the output voltage of the DC-DC converter 5 ,

An essential feature of this regulation is that the value of the power is determined by a measuring circuit and, in the case of deviation e, is restored from its desired value w with e = w-y by corresponding interaction.

This includes the electronic circuit 1 a measuring circuit (not shown in detail, symbolized by the reference numeral P), which measures the power, ie in particular the current and voltage levels. The measuring circuit outputs the value of the measurement to a data processing unit. It is conceivable that the measuring circuit or only parts of the measuring circuit are realized in the data processing unit, in particular, the calculation of the power in the data processing unit can be done. The data processing unit can be used as a microcontroller, microprocessor or similar. be designed. The data processing unit must be able to receive and send signals, execute (control) algorithms and deliver appropriate control signals. The data processing unit is about part of the transmitter 21 ,

The reference variable w power is variably adjustable, for example by the transmitter 21 , Different sensors consume different power, for example, a turbidity sensor needs more power than a pH sensor. Detects the transmitter 21 a sensor, the required power is made available for the corresponding sensor and the reference variable w is varied accordingly. This is possible with four-wire transmitters, such as those sold by the applicant under the name "Liquiline CM44". However, two-wire transmitters, such as those marketed by the applicant under the name "Liquiline CM42", can also operate several sensors simultaneously, alternately or one after the other by reducing the power to be transmitted.

Furthermore, the reference variable w power can also be influenced by other parameters. To call here is the ambient temperature. For example, the temperature response of the Class E amplifier 4 or even the whole circuit 1 be compensated. This is preceded by the temperature behavior of the class-E amplifier 4 recorded and adjusted the reference variable depending on the temperature profile.

As mentioned, the two sides 2 and 3 coupled together by means of a mechanical connector. The coils L1 and L2 inevitably create an air gap, which may vary depending on the sensor and which changes and reduces the coupling between the coils L1 and L2. This undesirable behavior can also be compensated accordingly by the regulation.

The command variable w can also vary depending on the operating mode of the sensor 22 to be set differently. One operating mode "Clear memory", "Change firmware", etc. For example, it may require more power.

Typically, data is not sent continuously. On the other hand, the sensor 22 continuously supplied with energy. During data transmission, no reliable control of the power is possible. One possible measure is then to make no adjustments to the performance for the duration of the data transmission and to make no performance measurements. Another advantage of this method is that it can be ruled out that during an ongoing communication by a control intervention an undesirable amplitude modulation takes place, which could be erroneously interpreted as a level change.

LIST OF REFERENCE NUMBERS

1

 Electronic switch

2

 transmitter side

3

 sensor side

4

 Class E amplifier

5

 DC-DC converter

6

 regulator

7

 Load modulation circuit

20

 gauge

21

 transmitter

22

 sensor

23

 interface

24

 interface

25

 electric wire

e

 deviation

f

 Frequency for T1

u

 manipulated variable

w

 command variable

y

 controlled variable

C1

 capacitor

C2

 capacitor

L1

Coil, corresponds 23

L2

Coil, corresponds 24

L3

 Kitchen sink

T1

 transistor

P

Power measurement at the input of 5

VCC

 supply voltage

Vout

Output voltage of 5

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014101502 [0009]
• DE 102012110310 [0042]

Claims (10)

Electronic switch ( 1 ) for use in process automation, wherein the electronic circuit ( 1 ) for transferring energy between a first page having a first interface ( 23 ), and a second page with a, to the first interface ( 23 ), second interface ( 24 ), the first interface ( 23 ) and the second interface ( 24 ) are configured for transmitting the energy, and wherein the first interface ( 23 ) and the second interface ( 24 ) are designed as inductive interfaces (L1, L2), comprising - the first interface ( 23 ), - a class E amplifier ( 4 ), the class E amplifier ( 4 ) the first interface ( 23 ), - a DC-DC converter ( 5 ), wherein the output of the DC-DC converter ( 5 ) with the input of the Class E amplifier ( 4 ), and - a controller ( 6 ) in a control circuit that controls constant power, with the power (P) that the class-E amplifier receives at its input, as a controlled variable (y), with a nominal power at the first interface ( 23 ) as a reference variable (w), and with the voltage (Vout) at the output of the DC-DC converter ( 5 ) as manipulated variable (u). Electronic switch ( 1 ) according to claim 1, wherein the electronic circuit ( 1 ) also transfers digital data between the first page and the second page and the first interface ( 23 ) and the second interface ( 24 ) are configured for transmitting the data, wherein the electronic circuit ( 1 ) transmits the digital data by means of amplitude shift keying. Electronic switch ( 1 ) according to claim 2, wherein the DC-DC converter ( 5 ) modulates the digital data to its output. Electronic switch ( 1 ) according to claim 2, wherein the class E amplifier ( 4 ) a load modulation circuit ( 7 ) which modulates the digital data. Electronic switch ( 1 ) according to at least one of claims 1 to 4, wherein the setpoint power at the first interface ( 23 ) is configured variably as a reference variable (w). Use of an electronic circuit according to one of claims 1 to 5 in process automation. Measuring device ( 20 ) of process automation, comprising an electronic circuit ( 1 ) according to at least one of claims 1 to 5. Measuring device ( 20 ) according to claim 7, wherein the measuring device ( 10 ) a higher-level unit, in particular a transmitter ( 21 ), and a consumer, in particular a sensor ( 22 ), wherein the superordinate unit with the consumer via the first interface ( 23 ) and the second interface ( 24 ) connected is. Measuring device ( 20 ) according to one of claims 7 or 8, wherein the reference variable (w) is variable and the desired power at the first interface ( 23 ) by the superordinate unit ( 21 ) is adjustable. Measuring device ( 20 ) according to one of claims 7 to 9, wherein the reference variable (w) is adjustable between the first interface and the second interface, depending on the type of consumer, ambient temperature, component tolerances, and / or the size of an air gap.

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