Field device with a switching converter circuit

• US 10,452,085 B2
• Filed: 06/05/2015
• Issued: 10/22/2019
• Est. Priority Date: 06/05/2014
• Status: Active Grant

• Current Assignee: Krohne Messtechnik GmbH & Co. KG
• Original Assignee: Krohne Messtechnik GmbH & Co. KG
• Inventors: Gerding, Michael, Ouzounis, Charalambos, Kaluza, Olaf
• Primary Examiner(s): McGue, Frank J
• Application Number:
  US14/731,578
• Publication Number:
  US 20150355652A1
• Time in Patent Office: 1,600 Days
• Field of Search: 342118
• CPC Class Codes: G01D 21/00 Measuring or testing not otherwise provided for
• CPC Class Codes: G01F 15/00 Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
• CPC Class Codes: G01F 23/00 Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01S 13/02 Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
• CPC Class Codes: G01S 13/08 Systems for measuring distance only indirect measurement G01S13/46
• CPC Class Codes: G01S 7/02 of systems according to group G01S13/00
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/155 using semiconductor devices only

Abstract

A field device (1) having a switching converter circuit (2) and a measuring circuit (3) for determining at least one measuring variable. The switching converter circuit (2) is supplied with electric power on the input side and the switching converter circuit (2) is connected to the measuring circuit (3) on the output side and the switching converter circuit (2) supplies the measuring circuit (3) with electric power.

The problems associated with changing interfering signals due to the switching converter circuit are reduced in that a load circuit (5) is actuated by a load control circuit (6) so that the output-side electric load at the switching converter circuit (2) does not fall below a minimum electric load.

Claims

1. A field device comprising:

a switching converter circuit and a measuring circuit for determining at least one measuring variable,

wherein the switching converter circuit is supplied with electric power on an input side and the switching converter circuit is connected to the measuring circuit on an output side and the switching converter circuit supplies the measuring circuit with electric power, and

wherein a load circuit including a resistive element is arranged at the output side of the switching converter circuit and is actuated by a load control circuit so that an output-side electric load at the switching converter circuit does not fall below a minimum electric load as a result of resistance applied by the resistive element.

2. The field device according to claim 1, wherein the minimum electric load is so large that the switching converter circuit continuously operates in PWM operation mode.

3. The field device according to claim 2, wherein the minimum electric load is so large that a burst-operating mode of the switching converter circuit is prevented.

4. The field device according to claim 1, wherein the minimum electric load corresponds to a maximum load of the measuring circuit.

5. The field device according to claim 4, wherein the minimum electric load corresponds to the maximum load of the measuring circuit in standard measuring operation.

6. The field device according to claim 1, wherein the load circuit is connected in parallel to the measuring circuit or the load circuit is implemented as part of the measuring circuit.

7. The field device according to claim 1, wherein the load circuit comprises at least one transistor that is actuated by the load control circuit.

8. The field device according to claim 1, wherein the load circuit and the load control circuit are implemented by at least one microcontroller, wherein electric power is used by actuating at least one I/O port of the microcontroller.

9. The field device according to claim 8, wherein electric power is used by driving a current over an electrical resistor to ground.

10. The field device according to claim 1, wherein the load control circuit actuates the load circuit in dependence on the operating mode of the measuring circuit by controlling, via the load control circuit, whether the resistive element is connected or disconnected from the output of the switching converter circuit.

11. The field device according to claim 10, wherein the field device is a radar measuring device for measuring distance and has at least one first operating mode for emitting and receiving HF radiation as well as for digitizing and storing the emitted and received HF radiation, and at least a second operating mode for evaluating the stored, digitized, emitted and received HF radiation, wherein the load control circuit actuates the load circuit in the first operating mode.

12. The field device according to claim 1, wherein the output-side electric load at the switching converter circuit is determined by detecting at least one electric parameter from the load control circuit and the load circuit is actuated by the load control circuit in dependence on the determined electric load, wherein the at least one electric parameter is the total driven current from the output side of the switching converter circuit.

13. The field device according to claim 1, wherein the at least one electric parameter is the total driven current from the output side of the switching converter circuit.

14. The field device according to claim 1, wherein the load circuit is configured to implement continual load adaptation in response to the load control circuit.