Control Circuitry Comprising an Adjustable Capacitor

Abstract

A control circuitry (11) comprises an adjustable capacitor (C1), and a bias source (111) configured to apply a bias voltage (V2) to said adjustable capacitor (C1) to adjust a capacitance value of the adjustable capacitor (C1). Such a control circuitry may for example be part of a sealing device (1) to seal a medical tubing (2), the sealing device (1) comprising a receptacle (100) to receive said medical tubing (2), the receptacle (100) comprising an electrode arrangement for causing a heat action on the tubing (2).

Claims

1. Control circuitry (11), comprising an adjustable capacitor (C1), characterized by a bias source (111) configured to apply a bias voltage (V2) to said adjustable capacitor (C1) to adjust a capacitance value of the adjustable capacitor (C1).

2. Control circuitry (11) according to claim 1, wherein the bias voltage is a DC voltage or has the shape of a saw-tooth waveform, a square wave, a pulse-width modulated (PWM) waveform or an AC waveform.

3. Control circuitry (11) according to claim 1 wherein the bias source (111) is operatively connected to said adjustable capacitor (C1) to apply the bias voltage (V2) across the adjustable capacitor (C1).

4. Control circuitry (11) according to claim 1 wherein the bias source (111) is controllable to adjust the bias voltage (V2).

5. Sealing device (1) to seal a medical tubing (2), comprising a receptacle (100) to receive said medical tubing (2), the receptacle (100) comprising an electrode arrangement for causing a welding action on the tubing (2), characterized by a control circuitry (11) according to claim 1, the control circuitry (11) being operatively connected to the electrode arrangement of the receptacle (100), the control circuitry (11) comprising a generator device (110) to supply an electrical current to the electrode arrangement.

6. Control circuitry (11) according to claim 5, wherein the electrode arrangement comprises a pair of electrodes (101, 102) arranged to receive said medical tubing (2) therebetween.

7. Sealing device (1) according to claim 5 wherein the control circuitry (11) comprises a control device (112) to control the bias source (111).

8. Sealing device (1) according to claim 7, wherein the control device (112) is configured to automatically control the bias source (111) based on a measured capacitance value of the electrode arrangement.

9. Sealing device (1) according to claim 5 wherein the adjustable capacitor (C1) is arranged in a circuit path electrically in parallel to the electrode arrangement.

10. Sealing device (1) according to claim 5 wherein the control circuitry (11) comprises an inductor (L1) electrically connected to the adjustable capacitor (C1).

11. Sealing device (1) according to claim 5 wherein the generator device (110) is configured to supply an AC electrical current to the electrode arrangement.

12. Sealing device (1) according to claim 5 wherein the tubing (2) is a PVC tubing.

13. Method to operate a sealing device (1) to seal a medical tubing (2), comprising: receiving said medical tubing (2) in a receptacle (100), the receptacle (100) comprising an electrode arrangement for causing a welding action on the tubing (2), and supplying an electrical current to the electrode arrangement using a control circuitry (11) operatively connected to the electrode arrangement of the receptacle (100), the control circuitry (11) comprising an adjustable capacitor (C1) and a generator device (110), characterized by applying, using a bias source (111) of the control circuitry (11), a bias voltage (V2) to said capacitor (C1) to adjust a capacitance value of the capacitor (C1).

Description

[0033] The idea underlying the invention shall subsequently be described in more detail with respect to the embodiments shown in the figures. Herein,

[0034] FIG. 1 shows an example of a sealing device for receiving a medical tubing;

[0035] FIG. 2 shows a schematic drawing of a receptacle of the sealing device;

[0036] FIG. 3 shows a schematic drawing of a control circuitry of the sealing device;

[0037] FIG. 4 shows a graph of a change in the capacitance as a function of an applied DC bias voltage; and

[0038] FIG. 5 shows a schematic circuit diagram of a control circuitry comprising an adjustable capacitor and a bias source for applying a bias voltage to the adjustable capacitor for adjusting a capacitance value of the adjustable capacitor.

[0039] FIG. 1 shows, in a schematic drawing, an embodiment of a sealing device 1 serving to seal a medical tubing, such as PVC tubing, by welding. The sealing device 1 may in particular be used to seal a tubing used with medical containers, such as containers containing blood, plasma, platelet, blood component or another body fluid collection. By means of the sealing of a tubing a container may be prepared for transportation and handling, and contamination of contents of the container may be prevented.

[0040] The sealing device 1, as shown in FIG. 1, comprises a housing 12 and a sealing element 10 arranged on the housing 12. The sealing element 10 forms a receptacle 100, in which a tubing may be received in order to seal the tubing by welding.

[0041] The sealing element 10 is in operative connection with a control circuitry 11, which may be embodied to supply an alternating (RF) current to the sealing element 10 in order to provide for a sealing action on a tubing received in the receptacle 100, as shall be explained further below.

[0042] A display 13 may be arranged on the housing 12, the display 10 allowing for example to output information concerning a sealing process or to enter control commands.

[0043] Referring now to FIG. 2, the receptacle 100 in one embodiment comprises an electrode arrangement having, for example, a pair of electrodes 101, 102, which are arranged and configured to receive a tubing 2 therebetween such that, when the tubing 2 is placed in the receptacle 100, the tubing 2 is tightly held in between the electrodes 101, 102. The electrodes 101, 102 may for example be elastically biased, for example using mechanical spring elements, such that the tubing 2 is held in between the electrodes 101, 102 under an elastic pretensioning, ensuring a tight contact in between the electrodes 101, 102 and the tubing 2 therebetween.

[0044] As further visible from FIG. 2, the electrodes 101, 102 are in operative connection with the control circuitry 11, such that a supply current may be fed to the electrodes 101, 102 to perform a welding action on the tubing 2.

[0045] Referring now to FIG. 3, the control circuitry 11 in one embodiment comprises a generator device 110 in the shape of an RF generator, which is connected to the electrode arrangement of the receptacle 100 by means of a resonator circuit formed by an inductor L1 and a capacitor C1. The electrodes 101, 102 of the electrode arrangement of the receptacle 100 form a capacitance C2, which is arranged electrically in parallel to the capacitor C1, the inductor L1 being arranged in series to the parallel arrangement of the capacitor C1 and the electrode arrangement of the receptacle 100.

[0046] In operation, an alternating (RF) current is excited by means of the RF generator 110, the current being supplied to the electrode arrangement of the receptacle 100, such that a local heating and hence a welding of a tubing received on the receptacle 100 is caused.

[0047] To be able to efficiently supply an alternating current to a tubing received on the receptacle 100 for delivering welding energy to the tubing, the capacitance of the capacitor C1 should be matched to the inductance of the inductor L1. For this, the capacitor C1 is adjustable in its capacitance value, such that the capacitor C1 may be tuned in order to provide for an efficient (resonant) operation of the control circuitry 11.

[0048] In order to provide for an easy circuitry which may be operated in an automated fashion to adjust the capacitance value of the capacitor C1, it herein is proposed to adjust the capacitor C1 by applying a (DC) bias voltage to the capacitor C1 in order to cause a change of capacitance based on the so-called the DC-bias effect.

[0049] Generally, if a DC bias voltage is applied to a capacitor while at the same time applying an alternating (AC) signal to the capacitor, the capacitance of the capacitor is varied in dependence on the value of the applied bias voltage. In particular, with increasing bias voltage the capacitance may be reduced, as this is shown qualitatively in an example in FIG. 4, showing a change in capacitance (dC/C, in percent) on the vertical axis for different applied bias voltages as noted on the horizontal axis.

[0050] As visible from FIG. 4, in certain examples, by applying a suitable bias voltage a capacitance of the capacitor may be substantially reduced, e.g. by more than 80%.

[0051] This is used herein to adjust the capacitance of the capacitor C1 by applying a bias voltage V2 using a bias source 111, as this is shown in one embodiment in FIG. 5.

[0052] In the embodiment of FIG. 5, the capacitor C1 is divided into two capacitors C11, C12 arranged in series, wherein the bias voltage V2 is applied by the bias source 111 to terminals of the capacitor C12 to adjust the capacitance of the capacitor C12. The bias source 111 herein is connected to the capacitor C12 via a resistor R1 to apply the bias voltage V2 across the capacitor C12.

[0053] During operation, the control circuitry 11 is excited by applying an alternating (RF) voltage V1 by means of the generator device 110 in order to supply an alternating (RF) current to the electrodes 101, 102 of the electrode arrangement of the receptacle 100. The generator device 110 as well as the bias source 111 herein are controlled by a control device 112 in the shape of a microcontroller, the control device 112 in particular being configured to tune the capacitance value of the capacitor C12 during operation of the sealing device 1.

[0054] For this, the control device 112 may be configured to measure a resulting impedance of the control circuitry 11 during operation and to adjust the capacitor C12 to control the bias voltage V2 in order to suitably match the overall capacitance to the inductor L1.

[0055] Accordingly, a manual tuning of the capacitor C1, C12 is not necessary. The adjustment of the capacitor C1, C12 may be automated and thus may be performed automatically during operation of the sealing device 1 by the control device 112 in the shape of the microcontroller.

[0056] In particular, if during operation the electrodes 101, 102 of the receptacle 100 change their position with respect to one another, due to a welding action on a tubing 2, as shown in FIG. 2, a change in capacitance of the electrode arrangement of the receptacle 100 may be automatically compensated by adjusting the capacitance value of the capacitor C1, C12.

[0057] In addition, the sealing device 1 may be used together with different types of tubing, in particular tubing made from a PVC material as well as tubing made from another material and of different geometric dimensions, without having to take special measures to adjust the control circuitry 11 of the sealing device 1. Rather, during operation the control circuitry 11 may automatically be adjusted for providing for a sealing action on the tubing received in the receptacle 100 by suitably tuning the capacitor C1 in an automated, controlled fashion.

[0058] The embodiments as described herein are not to be understood as limiting for the invention. Rather, the invention may be implemented also in an entirely different fashion.

[0059] The sealing device may be stationary, a tubing having to be placed on a sealing element to perform a welding action on the tubing.

[0060] In another embodiment, the sealing device may be a handheld device, such that a user may place the sealing device on a tubing in order to perform a welding action on the tubing.

[0061] Although described above with reference to an embodiment of a sealing device, it shall be noted that a control circuitry as concerned herein may generally be part of any device which employs a capacitor arrangement including an adjustable capacitor, such as a device comprising a resonator circuit. For example, a control circuitry as described herein may generally be used in electronic devices such as a radio, a television, a mobile phone, or a satellite or in other devices including a resonator circuit.

LIST OF REFERENCE NUMERALS

[0062] 1 Sealing device [0063] 10 Sealing element [0064] 100 Receptacle [0065] 101, 102 Electrode elements [0066] 11 Control circuitry [0067] 110 RF generator device [0068] 111 Bias source [0069] 112 Control device (microcontroller) [0070] 12 Housing [0071] 13 Display [0072] 2 Medical tubing [0073] C1, C2 Capacitor [0074] C11, C12 Capacitor [0075] L1 Inductor [0076] R1 Resistance [0077] V1 Voltage [0078] V2 Bias voltage