CONTROLLING A CONTACTLESS ENERGY TRANSMISSION BY MEANS OF A CHARACTERISTIC OF A RESONANT CIRCUIT

• US 20140097699A1
• Filed: 05/21/2012
• Published: 04/10/2014
• Est. Priority Date: 06/07/2011
• Status: Active Grant

• Current Assignee: Siemens Healthineers AG (Siemens AG)
• Original Assignee: Siemens Healthcare GMBH (Siemens AG)
• Inventors: Beyerlein, Walter, Hofmann, Florian, Henke, Stefan
• Granted Patent: US 9,715,962 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: A61B 6/56 Details of data transmission or power supply, e.g. use of slip rings
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention relates to a circuit for transmitting an input voltage (36) from an electrical energy source (64) in a stator (4, 55) to a load (70) within a device (6) movable relative to the stator (4, 55) comprising an control element (34) for converting an input voltage (36) into a transmission voltage (9), a resonant circuit (24) for receiving the transmission voltage (9), wherein the resonant circuit (24) contains a capacitor (22) and a primary winding (10) of a transformer (8) and the transformer (8) having the primary winding (10) and a secondary winding (12), wherein the primary winding (10) is provided for transmitting the transmission voltage (9) to the secondary winding (12) and the secondary winding (12) is provided for supplying the received transmission voltage (20) to the load (70). According to the invention, the actuator element (34) is provided for detecting the input voltage (36) and adjusting the frequency (27) of the transmission voltage (9) based on a control characteristic (45) in such a manner that the amplitude of the load voltage (20) dropping at the load (70) remains substantially constant, wherein in the control characteristic (45) the transmission ratio (25) of the resonant circuit (24) is plotted over the frequency (27) to be adjusted.

Claims

1. A circuit for transmitting an input voltage (36) from an electrical energy source (64) in a stator (4, 55) to a load (70) within a device (6) movable relative to the stator (4, 55), comprising:

an actuating element (34) for converting an input voltage (36) into a transmission voltage (9),

a resonant circuit (24) for receiving the transmission voltage (9), wherein the resonant circuit (24) contains a capacitance (22) and a primary winding (10) of a transformer (8), and

the transformer (8) comprising the primary winding (10) and a secondary winding (12), wherein the primary winding (10) is provided for transmitting the transmission voltage (9) to the secondary winding (12) and the secondary winding (12) is provided for delivering the received transmission voltage as an output voltage to the load (70),

wherein the actuating element (34) is provided for adjusting the frequency (27) of the transmission voltage (9) in such a manner that the transmission ratio (25) of the resonant circuit (24) remains essentially constant between the transmission voltage and the output voltage for a predetermined load range of values of.

2. The circuit as claimed in claim 1, wherein the actuating element (34) is configured for adjusting the frequency (27) of the transmission voltage (9) on the basis of a control characteristic (45) in which the transmission ratio of the resonant circuit (24) is plotted over the frequency (27) to be adjusted.

3. The circuit as claimed in claim 2, wherein a shape of the control characteristic (45) remains essentially constant within the predetermined load range.

4. The circuit as claimed in claim 2, comprising a device for detecting an input voltage (36) of the actuating element (34), wherein the actuating element (34) is configured for adjusting the frequency (27) of the transmission voltage (9) on the basis of the control characteristic (45) in such a manner that the output voltage (20) is independent of the input voltage.

5. The circuit as claimed in claim 1, wherein the capacitance (22) is connected in series with the primary winding (10) and the circuit (2, 60, 78) has a relief capacitance (56) which is connected in parallel with the primary winding (10).

6. The circuit as claimed in claim 1, wherein the actuating element (34) is provided for adjusting the frequency (27) within a predetermined frequency range (46).

7. The circuit as claimed in claim 6, wherein the capacitance (22) is selected in such a manner that the resonant frequency (31) of the resonant circuit (24) is outside the frequency range (46).

8. The circuit as claimed in claim 6, wherein the frequency range (46) is selected in such a manner that the control characteristic (45) comprises a fixed frequency (50) in which the transmission ratio (25) of the resonant circuit (24) is independent of an impedance of the load (70).

9. The circuit as claimed in claim 8, wherein the limit frequency of the frequency range (46) is the fixed frequency (50) toward the resonant frequency (31).

10. The circuit as claimed in claim 9, wherein the other limit frequency (52) of the frequency range (46) is selected from a second frequency range in which the transmission ratio (25) changes load-dependently within a transmission ratio range (54).

11. The circuit as claimed in claim 10, wherein the predetermined range states comprises load states during start-up of a load (70), connected to the circuit (2, 60, 78), in the movable device (6).

12. The circuit as claimed in claim 1, wherein the actuating element (34) is configured for calling up the control characteristic (45) from a memory (44).

13. The circuit as claimed in claim 12 comprising a write device (66) for storing values of the control characteristic (45) in the memory (44) on the basis of a measurement of the transmission ratio (25) of the resonant circuit (24).

14. The circuit as claimed in claim 13, wherein the write device (66) is configured for measuring the transmission ratio (25) on the basis of a step response.

15. The circuit as claimed in claim 13, wherein the write device (66) is configured for measuring the transmission ratio (25) at at least one point of the control characteristic (45) and for correcting the control characteristic (45) on the basis of the at least one measured point.

16. The circuit as claimed in claim 14, wherein the write device (66) for measuring the transmission ratio (25) is configured for measuring the zero transitions of the step response.

17. The circuit as claimed in claim 13, wherein the write device (66) is configured for measuring the transmission ratio (25) on the basis of a sweep of the frequency (27) of the transmission voltage (9).

18. The circuit as claimed in claim 17, which is designed to connect the resonant circuit (24) directly to an output of the circuit (2, 60, 78) during the sweep.

19. The circuit as claimed in claim 12 comprising a write device (66) for storing values of the control characteristic (45) in the memory (44) on the basis of a measurement of the phase difference between the transmission voltage (9) and the current (76) through the primary winding (10).

20. The circuit as claimed in claim 1 comprising a current measuring device for measuring a resonant circuit current (76) through the resonant circuit (24), wherein the actuating element (34) is configured for controlling the frequency (27) of the transmission voltage (9) in such a manner that the current (76) through the resonant circuit (24) does not exceed a predetermined value (88).

21. The circuit as claimed in one of the preceding claims comprising a voltage measuring device for measuring the load voltage (20), wherein the actuating element (34) is configured for controlling the load voltage (20) on the basis of the frequency (27) of the transmission voltage (9) in such a manner that the load voltage (20) follows a nominal voltage value (82).

22. The circuit as claimed in claim 21, wherein the voltage measuring device is arranged on the stator side (4) and has a data receiving device (72) for receiving the load voltage (20) from the movable device (6).

23. The circuit as claimed in claim 22 which is configured for starting the control of the load voltage (20) on the basis of the frequency (27) when the load voltage (20) is available at the data receiving device (72).

24. The circuit as claimed in claim 23 which is configured for ending the adjustment of the frequency (27) of the transmission voltage (9) on the basis of the control characteristic (45) when the control of the load voltage (20) has been started.

25. The circuit as claimed in claim 1 comprising an additional inductance (32) at the transformer (8) which is connected in series with the primary winding (10).

26. The circuit as claimed in claim 23, wherein the capacitance (22), the additional inductance (32) and the primary winding (10) are connected in series.

27. The circuit as claimed in claim 25 comprising a further resonant circuit (58) symmetric to the resonant circuit (24), which has a series circuit of a symmetry capacitance (22) corresponding to the capacitance (22) and a symmetry inductance (32) corresponding to the additional inductance (32), wherein the primary winding (10) is connected between the two resonant circuits (24, 58).

28. The circuit as claimed in claim 19, comprising a connection of interfering variables of the input voltage (36) via the control characteristic (45) for faster correction of the load voltage (20).

29. A tomograph, particularly a computer tomograph, for recording the spatial structure of an object arranged in an annular tunnel, wherein the annular tunnel rotates around a stator during the recording, comprising a circuit (2, 60, 78) as claimed in claim 1 for transmitting an input voltage (36) from an electrical energy source (64) to a load (70) within the annular tunnel.

30. A method for transmitting an input voltage (36) from an electrical energy source (64) in a stator (4) to a load (70) within a device (6) movable relative to the stator (4), comprising:

converting the input voltage (36) into a transmission voltage (9),

receiving the transmission voltage (9) with a resonant circuit (24) which contains a capacitance (22) and a primary winding (10) of a transformer (8),

transmitting the transmission voltage (9) to a secondary winding (12) of the resonant circuit (24),

delivering the transmission voltage (9) received by the secondary winding (12) to the load (70), and

adjusting the frequency (27) of the transmission voltage (9) in such a manner that the transmission ratio (25) of the resonant circuit (24) remains essentially constant for a predetermined range of values of a load which can be connected to the secondary winding (12) so that the transmission ratio (25) of the resonant circuit (24) is independent of the load within the predetermined range of values.