System and method for controlling a temperature

Abstract

The present invention relates to a system (100) for controlling a temperature, the system (100) comprising: a temperature sensor module (10), which is configured to measure a temperature value; a microcontroller module (20), which is coupled to the temperature sensor module (10) and which is configured to generate AC heating pulse signals by separate sequential code steps based on the measured temperature value; a coupling module (30) which is coupled to the microcontroller module (20) and which is configured to transform the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components; and a heating module (40) which is coupled to the coupling module (30) and which is configured to generate heat according to the transformed AC heating pulse signals.

Claims

1. A system for controlling a temperature for skin heating, the system comprising: a temperature sensor module, which is configured to measure a temperature value of the skin to be heated; a microcontroller module, which is coupled to the temperature sensor module and which is configured to compare a desired temperature and the measured temperature value and to generate AC heating pulse signals by separate sequential code steps based on the temperature comparison, wherein every single AC heating pulse signal requires the execution of distinct code steps by the microcontroller module; a coupling module, which is coupled to the microcontroller module and which is configured to transform the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components, wherein the transfer function is lower than 0.1 for the DC signal components; a heating module, which is coupled to the coupling module and which is configured to generate heat according to the transformed AC heating pulse signals in the form of heating pulses of a time interval between 1 s and 500 ms; and a memory module, which is coupled to or included in the microcontroller module and which is configured to store the code steps used by the microcontroller module.

2. The system according to claim 1, wherein the microcontroller module is a multi-core or a single-core processor and is configured to be operated in sequential processing.

3. The system according to claim 1, wherein the coupling module is configured to attenuate the DC signal components to a value of less than 4% of an input DC signal component, to a value of less than 2% of an input DC signal component, or to a value of less than 0.5% of an input DC signal component.

4. The system according to claim 1, wherein the microcontroller module is configured to generate the AC heating pulse signals based on the temperature comparison using a duty-cycle modulation.

5. The system according to claim 4, wherein the microcontroller module is configured to calculate an amount of requested thermal energy based on the temperature comparison, and control the duty cycle of the generated AC heating pulses based on the calculated amount of requested thermal energy.

6. The system according to claim 1, wherein the microcontroller module is configured to generate a period time of the AC heating pulse signals based on the temperature comparison using a frequency modulation.

7. The system according to claim 6, wherein the microcontroller module is configured to: calculate an amount of requested thermal energy based on the temperature comparison, and control the period time of the generated AC heating pulses based on the calculated amount of requested thermal energy.

8. The system according to claim 7, wherein the microcontroller module is configured to control a frequency or an amplitude of the generated AC heating pulse signals.

9. The system according to claim 1, wherein the heating module is a resistive element or a resistor.

10. The system according to claim 1, wherein the coupling module is a capacitor or an inductor or a transformer.

11. The system according to claim 1, wherein the coupling module comprises a driver circuit.

12. The system according to claim 1, wherein the microcontroller module comprises an analogue input, to which the temperature sensor module is coupled to.

13. A medical system comprising a system according to claim 1.

14. The system according to claim 1, wherein the time interval of the heating pulses is between between 2 s and 30 ms.

15. A method for controlling a temperature for skin heating, the method comprising the steps of: measuring a temperature value of the skin to be heated by means of a temperature sensor module; comparing a desired temperature and the measured temperature value and generating AC heating pulse signals by separate sequential code steps based on the temperature comparison by means of a microcontroller module, wherein every single AC heating pulse signal requires the execution of distinct code steps by the microcontroller module, and wherein the code steps are stored in a memory module which is coupled to or included in the microcontroller module; transforming the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components by means of a coupling module, wherein the transfer function is lower than 0.1 for the DC signal components; and generating heat according to the transformed AC heating pulse signals by means of a heating module in form of heating pulses of a time interval between 1 s and 500 ms.

16. The system according to claim 14, wherein the time interval of the heating pulses is between 5 s and 100 s.

17. The method according to claim 15, wherein the time interval of the heating pulses is between between 2 s and 30 ms.

18. The method according to claim 17, wherein the time interval of the heating pulses is between 5 s and 100 s.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic diagram of a system for controlling a temperature according to an exemplary embodiment of the present invention;

(2) FIG. 2 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention;

(3) FIG. 3 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention;

(4) FIG. 4 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention,

(5) FIG. 5 shows a voltage versus time diagram for explaining the present invention;

(6) FIG. 6 shows a voltage versus time diagram for explaining the present invention,

(7) FIG. 7 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention;

(8) FIG. 8 shows a schematic diagram of a medical system according to an exemplary embodiment of the present invention; and

(9) FIG. 9 shows a schematic diagram of a flowchart of a method for controlling a temperature according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(10) The illustration in the drawings is purely schematical and does not intend to provide scaling relations or size information. In different drawings or figures, similar or identical elements are provided with the same reference numerals. Generally, identical parts, units, entities or steps are provided with the same reference symbols in the description. FIG. 1 shows a schematic diagram of a system for controlling a temperature according to an exemplary embodiment of the present invention.

(11) A system 100 for controlling a temperature may comprise a temperature sensor module 10, a microcontroller module 20, a coupling module 30, and a heating module 40.

(12) The temperature sensor module 10 may be configured to measure a temperature value.

(13) The microcontroller module 20 may be coupled to the temperature sensor module 10 and may be configured to generate AC heating pulse signals by separate sequential code steps based on the measured temperature value.

(14) The coupling module 30 may be coupled to the microcontroller module 20 and may be configured to transform the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components.

(15) The microcontroller module 30 may be configured to control the amplitudes of the generated AC heating pulse signals using a digital-to-analogue converter. The heating module 40 may be coupled to the coupling module 30 and may be configured to generate heat according to the transformed AC heating pulse signals.

(16) A micro controller (or microprocessor, P) used as the microcontroller module 20 may comprise an analog input 22 coupled to a temperature sensor used as the temperature sensor module 10 and a digital output capacitive used as the coupling module 30 may be coupled to a heater resistor used as the heating module 40. A software control loop may generate heating pulses which result in an AC current into the heater. The heater may comprise any dissipative component, e.g. a resistor, or a semiconductor etc. The AC coupling may be achieved via a capacitor or inductively via a transformer.

(17) The system 100 for controlling a temperature may further comprise to a user-interface for setting the desired temperature and communicating status/errors to the user.

(18) To deliver sufficient output current, a power driver comprising two switching FET's may be added. The temperature sensor may be a NTC, PTC, thermo-couple, semiconductor or any other temperature dependent device. The total circuit may be operating on one single supply voltage, e.g. 5 Volt.

(19) The control algorithm inside the micro controller may take care of: 1. Voltage to temperature conversion of the temperature sensor signal 2. Generation of an error signal, being the difference between a desired temperature set-point and the actual temperature. 3. Loop filtering 4. Generation of heating pulses 5. Modifying the duty-cycle or the frequency of said heating pulses in response to the output of the loop filter. 6. Safety measures to prevent overheating on basis of e.g. power output during a time interval, temperature sensor out-of-range, temperature difference between two temperature sensors out of range, ADC failure by checking the absence of sample jitter or similar.

(20) Advantageously, an occurring hardware failure of the switching FET's may increase the supply current, but will not generate dissipation in the heater.

(21) FIG. 2 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention.

(22) Contrary to FIG. 1, in FIG. 2, a further exemplary embodiment of the present invention is shown. The driver circuitry may be extended to an H-bridge. This may double the voltage and may increase the required impedance levels for achieving the same output power with a factor of four and consequentially a four times smaller capacitor, or four times slower heating pulses, which implies that a slower microprocessor may be required.

(23) Two temperature sensors, Negative Temperature Coefficient Thermistors, NTC, e.g. NTC1 and NTC2 may be applied for safety (redundancy) reasons and may be set to determine the heat-flux from the heater into the skin. ADC input A2 may be utilized for normalization of the temperature measurement. The normalization may allow compensating for any supply voltage fluctuations. The analogue input signals are first voltage-divided in order to fit well within the analogue input range of the on-chip ADC.

(24) The dissipated power in the heater is calculated from the supply voltage and the average voltage-drop across sensing resistor Rs. Obviously; said power must be corrected for the power loss in the switching field-effect transistor's, FET.

(25) FIG. 3 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention.

(26) Contrary to FIG. 1 and to FIG. 2, a further exemplary embodiment of the present invention in FIG. 3 shows the heater inductively coupled to the driver circuitry. The transformer may be part of the sensor head or be part of a disposable plaster comprising the sensor spot in order to enable e.g. the positioning of the heater closely to the skin to avoid thermal gradients.

(27) FIG. 4 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention.

(28) According to the exemplary embodiment of the present invention as shown in FIG. 4, the two NTC's and the heater are located in the probe-head, which is connected via an approximately 1 meter long cable, for instance 1 m+/0.2 m, to the electronics. To avoid any Electromagnetic compatibility, EMC, issues, proper de-coupling may be added. Both branches of the H-bridge may be controlled in anti-phase in such a way that the resulting heater voltage shows as depicted in the next Figure.

(29) FIG. 5 shows a voltage versus time diagram for explaining the present invention. In FIG. 5, a heating wave of a period of 40 s is shown. The 0 Volt stairs are dictated by the practical limitation of the software library. This limits the maximum attainable power. The amplitude of the AC signal is 5 Volts.

(30) FIG. 6 shows a voltage versus time diagram for explaining the present invention. In FIG. 6, continuously repeated cycles through a loop are shown, where a fixed 95% of the loop period is reserved for heating waves. The actual number of heating waves may be adapted to the needs of the temperature controller. In order to keep the total number of waves constant, zero-energy padding waves are added. In FIG. 6, a heating wave of a period of 77 ms is shown, corresponding to 13 Hz.

(31) FIG. 7 shows a schematic diagram of a system for controlling a temperature according to a further exemplary embodiment of the present invention.

(32) A system 100 for controlling a temperature may comprise a temperature sensor module 10, a microcontroller module 20, a coupling module 30, and a heating module 40.

(33) The temperature sensor module 10 may be configured to measure a temperature value.

(34) The microcontroller module 20 may be coupled to the temperature sensor module 10 and may be configured to generate AC heating pulse signals based on the measured temperature value.

(35) The microcontroller module 20 may be coupled to additional communication means (not drawn) for control and monitoring.

(36) The coupling module 30 may be coupled to the microcontroller module 20 and may be configured to transform the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components.

(37) The heating module 40 may be coupled to the coupling module 30 and may be configured to generate heat according to the transformed AC heating pulse signals.

(38) The coupling module 30 may be configured to provide a higher order high-pass filter or band-pass filter. In this way the output power is more strongly decreased when the period of the heating waves deviates (for instance the period of the heating wave may increase or decrease) from its intended value, which may happen due to software interrupts, software flaws or changes in processor clock frequency or execution time. The higher order high-pass filter or band-pass filter advantageously provides an even more robust and safe operation of the system.

(39) Possible parameters used for the electrical components of the system for controlling a temperature and possible parameters for current, frequencies and voltages are the following:

(40) R heater of 16.5 Ohm, U.sub.peak of 4.4 V, I.sub.peak of 0.27 A, heating wave duty cycle of 0.75, control-loop duty cycle of 0.95, RMS heating power of 836 mW, T.sub.instru. (time period used for instructions) of 5 s, number of instructions per heating wave of 8, a heating wave period of 8 times 5s, e.g. 40 s, corresponding to 25 kHz, =4*T.sub.HWP of 160 s, wherein is a characteristic time period, and a coupling capacitor of 10 F.

(41) At maximum (95% duty cycle) 836 mW heating power can be generated into a 16.5 heater. The time constant of the AC coupling is chosen to be 4 times the loop period; hence the required coupling capacitor is 10 F. To safe-guard shortage of the coupling capacitor, a series arrangement of at least two 20 F capacitors can be applied.

(42) FIG. 8 shows a schematic diagram of a medical system according to an exemplary embodiment of the present invention.

(43) A medical system 200 may comprise a system 100 for controlling a temperature. The medical system 200 may be a system for measuring CO.sub.2blood gas level or an arterial blood gas analyser. The medical system 200 may be wear-able, preferably cable-less.

(44) FIG. 9 shows a schematic diagram of a flowchart of a method for controlling a temperature according to an exemplary embodiment of the present invention.

(45) The method for controlling a temperature may comprise the following steps of:

(46) As a first step of the method, measuring S1 a temperature value by means of a temperature sensor module 10 may be performed.

(47) As a second step of the method, generating S2 AC heating pulse signals by separate sequential code steps based on the measured temperature value by means of a microcontroller module 20.

(48) As a third step of the method, transforming S3 the generated AC heating pulse signals into transformed AC heating pulse signals using a transfer function which is substantially zero for DC signal components by means of a coupling module 30.

(49) As a fourth step of the method, generating S4 heat according to the transformed AC heating pulse signals by means of a heating module 40.

(50) The steps of the method may be iteratively or recursively repeated.

(51) It has to be noted that embodiments of the present invention are described with reference to different subject-matters. In particular, some embodiments are described with reference to method type claims, whereas other embodiments are described with reference to the device type claims.

(52) However, a person skilled in the art will gather from the above and the foregoing description that, unless otherwise notified, in addition to any combination of features belonging to one type of the subject-matter also any combination between features relating to different subject-matters is considered to be disclosed within this application. However, all features can be combined providing synergetic effects that are more than the simple summation of these features.

(53) While the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the present invention is not limited to the disclosed embodiments.

(54) Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

(55) In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.