INTEGRATED CIRCUIT FOR AIR CONDITIONING SYSTEMS

Description

[0001] Implementation and realization methods of the invention relate to integrated circuits, in particular those used for conditioning an oscillating analog signal comprising a succession of damped oscillations.

[0002] We know of integrated circuits comprising processing units configured to process oscillating analog signals comprising a succession of oscillations with an amplitude decreasing over time.

[0003] For example, flow meters are known to include a processing unit configured to determine a fluid flow rate from oscillating analog signals generated by inductive-capacitive sensors, also referred to as "LC sensors", used in combination with a wheel placed in a fluid flow and having at least one conductive portion.

[0004] LC sensors include, among other things, a capacitor and an inductor connected in parallel, and are connected to input / output cells linked to the processing unit.

[0005] These LC sensors generate oscillating analog signals consisting of a series of damped oscillations. These oscillating analog signals are transmitted to the processing unit via the integrated circuit's input / output cells. The processing unit is then configured to determine the fluid flow rate from the oscillating analog signals generated by the LC sensors.

[0006] However, these oscillating analog signals may have the disadvantage of including initial oscillations of high amplitudes which can lead to failure of the electronic components of the processing unit.

[0007] To address this drawback, known solutions involve limiting the voltage supplied to the LC sensor to compensate for the overvoltage resulting from the initial oscillations. This limitation imposes an additional constraint on the flowmeter design and restricts the flexibility of having alternative functionalities for input / output cells with different supply power ranges.

[0008] Another solution is to use diodes for protection against electrostatic discharge (in English). « electrostatic discharge diodes ", better known by the acronym " ESD diodes » However, such a solution is costly.

[0009] US 6 420 873 B1 generally presents magnetic resonance imaging equipment, and more specifically a process for reducing transient noise that interferes with the desired signal and can decrease the quality of the image produced.

[0010] US 2 551 529 A relates to an electronic device for analyzing the distribution of electrical pulses, and more particularly to a differential pulse amplitude selector or discriminator, designed to determine how many pulses, possibly of random value, occur within a predetermined amplitude range.

[0011] US 3,133,205 A discloses a transistorized circuit that delivers an output pulse only when the amplitude of an input pulse lies between two defined limits. This type of circuit is commonly used in pulse amplitude monitoring systems and in test equipment as a pulse height analyzer.

[0012] Therefore, there is a need to be able to offer a solution that reduces or even eliminates the risk of failure of electronic components in a processing unit, resulting from oscillating analog signals including initial oscillations of high amplitude.

[0013] More specifically, there is a need to be able to offer such a solution which does not have the disadvantages of the aforementioned known solutions.

[0014] According to one aspect, an integrated circuit is proposed for conditioning an oscillating analog signal comprising a succession of damped oscillations, the integrated circuit comprising an input / output cell including: a first port configured to receive said oscillating analog signal, called input signal, a second port configured to deliver an analog output signal from the input signal, control means coupled between the first port and the second port and configured to suppress at least the first oscillation from the input signal so as to deliver in the output signal oscillations of the input signal having an amplitude less than a first threshold, for example 5V.

[0015] The output of the integrated circuit can in particular be connected to a processing unit so as to be able to transmit to the latter the oscillating analog signal delivered by the second port.

[0016] The first threshold is then advantageously compatible with correct operation of the processing unit connected to the second port, i.e. compatible with a maximum voltage level tolerable by the processing unit.

[0017] Such an integrated circuit prevents the transmission of oscillations with an amplitude, typically a peak-to-peak voltage level, exceeding the threshold, to the processing unit. These oscillations could indeed cause the processing unit to fail if transmitted. Thus, such an integrated circuit reduces or even eliminates the risk of processing unit failure.

[0018] Preferably, the integrated circuit further includes said processing unit connected to the second port, the first threshold being compatible with a maximum voltage level tolerable by the processing unit.

[0019] Advantageously, the integrated circuit further includes a main control unit. Moreover, the control means include a switch connected between the first and second ports, the switch being controllable by the main control unit. The control means further include an auxiliary control unit configured to temporarily take control of the switch in place of the main control unit so as to allow the suppression of at least the first oscillation of the input signal.

[0020] The switch transmits the input signal to the processing unit. The main control unit is normally configured to control the switch with a command signal. However, the auxiliary control unit is configured to temporarily take control of the switch to suppress at least the first oscillation of the input signal, regardless of the command signal from the main control unit.

[0021] The I / O cell including the control means can then be designed from a conventional I / O cell in which the auxiliary control unit is added.

[0022] Preferably, the switch is configured to operate in the presence of one or more oscillations of the input signal having an amplitude greater than or equal to said first threshold, and having a first terminal connected to the first port and a second terminal connected to the second port, the switch being controllable: ∘ either in a closed state electrically connecting the first port to the second port, ∘ or in an open state disconnecting the first port from the second port.

[0023] In addition, the auxiliary control unit is configured to: • maintain the switch in an open state during the first oscillation of the input signal and possibly one or more oscillations directly following the first oscillation, then • allow the switch to toggle to a closed state.

[0024] Specifically, the auxiliary control unit forces the switch to an open state during the first oscillation(s) of the input signal. This prevents the transmission of these oscillations to the second port of the integrated circuit. Furthermore, by allowing the switch to flip to a closed state after at least one oscillation, the auxiliary control unit enables the transmission of subsequent oscillations of the analog input signal to the second port of the integrated circuit.

[0025] Thus, the auxiliary control unit makes it possible to suppress the first oscillation(s) of the input signal so as to deliver in the output signal oscillations of the input signal having an amplitude less than a threshold.

[0026] In an advantageous embodiment, the input / output cell further includes a converter, or shaping circuit, configured to convert the oscillating analog signal into a square wave signal and to deliver this square wave signal to said auxiliary control unit.

[0027] In an advantageous embodiment, the converter includes a Schmitt flip-flop.

[0028] In an advantageous embodiment, the auxiliary control unit includes a counter configured to count a defined number of square wave edges from a first square wave edge, the auxiliary control unit being configured to allow a switch to a closed state when the counter reaches the defined number of rising edges by the main control unit.

[0029] Thus, the counter allows counting the number of oscillations that should not be transmitted at the output of the input / output cell.

[0030] Alternatively, a timing circuit can be used instead of a counter to determine when to switch the switch to a closed state to transmit the oscillations to the second port of the input / output cell.

[0031] In an advantageous embodiment, the integrated circuit further includes said processing unit connected to the second port of the integrated circuit and configured to count the number of oscillations of the output signal having an amplitude greater than a second threshold less than the first threshold.

[0032] From another perspective, a system is proposed that includes: a capacitive inductive sensor, an integrated circuit as described previously whose first port is connected to the capacitive inductive sensor, the capacitive inductive sensor being adapted to deliver said oscillating analog signal after an excitation phase triggered by the integrated circuit.

[0033] According to another aspect, a flow meter is proposed comprising a system as described previously.

[0034] According to another aspect, a conditioning method for an oscillating analog signal comprising a succession of damped oscillations is proposed, a method in which at least the first oscillation of the oscillating analog signal is suppressed and the other oscillations of the oscillating analog signal having an amplitude less than a first threshold are delivered in an output analog signal.

[0035] Other advantages and features of the invention will become apparent upon examination of the detailed description of implementation and embodiments, which are by no means limiting, and the accompanying drawings in which: [ Fig. 1 ], [ Fig. 2 ], [ Fig. 3 ], [ Fig. 4 ] schematically illustrate modes of embodiment and implementation of the invention.

[0036] There figure 1 represents a SYS system according to an embodiment of the invention. The system includes a capacitive inductive sensor, called an LC sensor, and an integrated circuit IC comprising an input / output cell IO, a main control unit UPC and a processing unit UT.

[0037] The UT processing unit is configured to tolerate a maximum voltage threshold. For example, the UT processing unit can be configured to process signals with a maximum voltage amplitude of 5V.

[0038] The LC sensor comprises an inductance Ls and a capacitance Cs mounted in parallel.

[0039] The I / O cell includes a first PAD port to which the LC sensor is connected.

[0040] The I / O cell includes a first protection diode DD1 with an input connected to the first PAD port and an output connected to a power supply terminal intended to receive a supply voltage VDD. The I / O cell also includes a second protection diode DD2 with an input connected to ground (GND) and an output connected to the first PAD port.

[0041] The input / output cell also includes a second ANA port to which the UT processing unit is connected.

[0042] The IO input / output cell, which is a bidirectional cell, also includes an ENIN input, an IN output (although being an output, it is designated by the reference IN due to its placement relative to the main control unit UPC), an RDY output, an LPSMODE input, an ENANA input, an ENOUT input and an OUT input (although being an input, it is designated by the reference OUT due to its placement relative to the main control unit UPC).

[0043] The IO input / output cell further includes an INT switch having a first terminal connected to the first PAD port and a second terminal connected to the second ANA port.

[0044] The INT switch can be controlled in a closed state, electrically connecting the first PAD port to the second ANA port. The INT switch can also be controlled in an open state, disconnecting the first PAD port from the second ANA port. Specifically, the signal delivered by the UPC main control unit to the ENANA input controls the INT switch.

[0045] The INT switch can be, for example, a transistor or a thyristor. Specifically, the INT switch is configured to tolerate a signal with an amplitude exceeding the maximum voltage threshold tolerated by the processing unit. For example, the INT switch is tolerant of voltages above 5V.

[0046] The input / output cell IO also includes a converter, or shaping circuit, CO, a buffer circuit TP and an auxiliary control unit UC configured to control the switch INT.

[0047] The CO converter has an input electrically connected to the first PAD port and an output connected to an LPSIN input of the auxiliary control unit (UC). This CO converter is powered by the VDD voltage. The CO converter also has a port connected to ground. The CO converter is suitable for generating a square wave output from an oscillating analog input signal. Preferably, the CO converter is a Schmitt flip-flop.

[0048] The UPC main control unit is configured to deliver a signal to the ENIN input to enable or disable the CO converter.

[0049] The square wave signal at the output of the CO converter can be transmitted to the IN output so that it can be processed by the main control unit UPC.

[0050] The CO converter has two functions. The first, conventional function is to shape a distorted (or noisy) square wave signal from outside the integrated circuit; this shaped signal is then sent to the IN output of the input / output cell. The second function is to convert an oscillating signal from the LC sensor into a square wave signal. This second function will be described in detail later.

[0051] The signal delivered to the LPSMODE input enables the auxiliary control unit UC to be activated.

[0052] The auxiliary control unit UC includes a CPT counter adapted to count a number of rising edges of the square wave signal delivered by the CO converter to the LPSIN input of the auxiliary control unit UC.

[0053] The auxiliary control unit UC is configured to receive the signal delivered by the main control unit UPC at the ENANA input of the input / output cell.

[0054] More specifically, the auxiliary control unit UC is configured to allow control of the INT switch by the ENANA signal or to maintain the INT switch in an open state by delivering an LPENANA control signal.

[0055] In particular, the auxiliary control unit UC is configured to deliver an LPENANA control signal when the CPT counter has not yet reached a predetermined number n.

[0056] The auxiliary control unit (UC) also includes an input configured to receive a signal from the ENOUT input. This signal can be output by the main control unit (UPC) to activate or deactivate the TP buffer circuit.

[0057] The auxiliary control unit (UC) also includes an output connected to the RDY output of the IO input / output cell. The UC is thus configured to send a signal to the main control unit (UPC) when the counter reaches the predetermined number n. The UC therefore indicates that the main control unit can control the switch via the LPENANA signal.

[0058] The TP buffer circuit has an input configured to receive a signal delivered to the OUT input of the IO input / output cell by the UPC main control unit, and an output configured to deliver a signal to the first PAD port of the IO input / output cell.

[0059] The TP buffer circuit also includes an input configured to receive the signal delivered by the main control unit via the ENOUT input of the IO input / output cell. This signal enables or disables the buffer circuit.

[0060] The TP buffer circuit is powered by the VDD voltage. The TP buffer circuit also has a port connected to ground (GND).

[0061] The TP buffer circuit is configured to allow the triggering of an excitation phase of the LC sensor. During this excitation phase, the first PAD port is pulled to 0 Volts by setting the ENOUT signal to 0 to activate the TP buffer circuit and setting the OUT input to 0.

[0062] At the end of the excitation phase, the ENOUT signal is set to 1 to disable the TP buffer circuit. The first PAD port is then not pulled to 0 or 1 by the TP buffer circuit. The LC sensor then outputs an analog signal consisting of a series of damped oscillations.

[0063] There figure 2 represents a method of implementing a conditioning process according to the invention.

[0064] In step 20, the oscillating electrical signal delivered by the LC sensor is transmitted to the first PAD port of the IO input / output cell.

[0065] This oscillating electrical signal, called the input signal, then arrives at the input of the CO converter. The CO converter converts the oscillating input signal into a square wave signal. This square wave signal is then transmitted to the LPSIN input of the auxiliary control unit (ACU).

[0066] In step 21, at least the first oscillation of the input signal is suppressed so as to deliver in the output signal the other oscillations of the input signal.

[0067] Specifically, the CPT counter of the auxiliary control unit (ACU) counts the rising edges of the square wave signal, which represent the oscillations of the input signal, until it reaches a predefined number n. During these n oscillations, the ACU outputs an LPENANA signal to keep the INT switch open, preventing the transmission of these n oscillations to the processing unit (PU). When the CPT counter reaches this predefined number n, the ACU outputs an RDY signal to the main control unit, allowing the INT switch to be controlled by the signal delivered by the main control unit (MCU) to the ENANA input. The signal delivered to the ENANA input can then close the INT switch. Subsequent oscillations of the oscillating analog signal delivered by the LC sensor are then transmitted to the processing unit (PU) in step 22.

[0068] In particular, the number n of oscillations is defined as a function of the maximum voltage threshold S1 that can be tolerated by the processing unit UT.

[0069] Thus, the auxiliary control unit UC allows, by controlling the switch INT in an open state during the first n oscillations, to transmit to the processing unit UT only the oscillations of the input signal having an amplitude below the threshold S1.

[0070] In particular, these n oscillations could have an amplitude that could cause the electronic components of the processing unit (PU) to fail if they were transmitted to the PU. For example, these n oscillations could have an amplitude greater than 5V, while the PU has a maximum voltage threshold of 5V.

[0071] By preventing the transmission of these n oscillations to the processing unit UT, the auxiliary control unit UC helps to protect the processing unit UT against oscillations with an amplitude that could cause a failure of the processing unit UT.

[0072] In particular, the auxiliary control unit (UC) can, for example, be configured to suppress only the first oscillation, or the first two oscillations, or even the first three oscillations of the input signal. In other words, n can be equal to 1, 2, or 3, for example.

[0073] The IO input / output cell can be made from a conventional input / output cell in which the auxiliary control unit UC as well as the LPSMODE input and the RDY output are added.

[0074] There figure 3 illustrates a chronogram representing the implementation of a process according to an embodiment of the invention.

[0075] Curve 10 represents the signal delivered to the LPSMODE input.

[0076] Curve 11 represents the signal delivered at the ENOUT input.

[0077] Curve 12 represents the signal delivered by the LC sensor on the first PAD port.

[0078] Curve 13 represents the signal delivered to the LPSIN input of the auxiliary control unit UC.

[0079] Curve 14 represents the value of the CPT counter of the auxiliary control unit UC.

[0080] Curve 15 represents the signal delivered at the RDY input.

[0081] Curve 16 represents the LPENANA signal delivered by the auxiliary control unit UC.

[0082] Curve 17 represents the signal delivered at the ENANA input.

[0083] Curve 18 represents the signal delivered by the ANA output.

[0084] In this implementation of the process, the auxiliary control unit UC is configured to allow the switch INT to switch to a closed state after three oscillations of the oscillating analog signal delivered by the LC sensor ( n is therefore predefined at 3).

[0085] Furthermore, in this implementation, the signals delivered to the ENIN, ENANA and ENOUT inputs as well as the LPENANA signal are active low-state control signals, here at 0.

[0086] At step T0, the signal delivered to the LPSMODE input is 0. The auxiliary control unit UC is therefore deactivated. The ENOUT, LPENANA, and ENANA signals are all 1, so the auxiliary control unit UC is deactivated and the INT switch is open. The RDY signal is 0. The LC sensor is not outputting any signal. Furthermore, the ENIN signal (not shown) is 0, thus activating the CO converter.

[0087] At step T1, the signal delivered to the LPSMODE input is set to 1. The auxiliary control unit UC is activated. The voltage at the first PAD port of the input / output cell IO is pulled to Vmid where Vmid = VDD / 2. In particular, the voltage Vmid is imposed by a circuit not shown in the diagram. figure 1 .

[0088] In step T2, the signal delivered to the ENOUT input is set to 0 to activate the TP buffer circuit. The OUT input signal (not shown) is 0. The voltage at the first PAD port of the IO input / output cell is pulled to 0 V. This phase corresponds to the LC sensor excitation phase. The auxiliary control unit UC sets the LPENANA signal to 1 to force the switch into an open state. The INT switch can no longer be controlled by the ENANA signal. The signal delivered to the RDY input goes high to indicate to the main control unit UPC that the switch is open and cannot be controlled by the ENANA signal.

[0089] At step T3, the ENOUT signal is set to 1, marking the end of the excitation phase. The LC sensor then outputs the oscillating analog input signal to the first PAD port. This analog signal consists of a series of damped oscillations. The first oscillation is converted into a square wave signal (LPSIN) by the CO converter. The CPT counter counts the first rising edge on the LPSIN signal. The INT switch is forced to an open state by the LPENANA signal, which is held at 1, while the ENANA signal is ignored. Thus, this first oscillation is not transmitted to the ANA output of the input / output cell.

[0090] At step T4, a second rising edge on the LPSIN signal is counted by the CPT counter. The INT switch is held in an open state by the LPENANA signal, which is at 1. The second oscillation is not transmitted to the ANA output of the input / output cell.

[0091] At step T5, a third rising edge on the LPSIN signal is counted by the CPT counter. The CPT counter then reaches the predefined number n of oscillations that should not be transmitted to the processing unit UT. This ensures that subsequent oscillations will have an amplitude below the threshold S1. The INT switch is held in an open state by the LPENANA signal. The third oscillation is not transmitted to the ANA output of the input / output cell.

[0092] At step T6, the LPENANA signal goes low. The INT switch is then no longer forced into an open state by the LPENANA signal and becomes controllable again by the signal delivered to the ENANA input. Since the signal delivered to the ENANA input is low, the switch toggles to a closed state. The auxiliary control unit sets the signal delivered to the RDY output to low to indicate to the main control unit that the switch can be controlled by the ENANA signal.

[0093] With the INT switch in the closed state, subsequent oscillations of the input signal are transmitted to the UT processing unit. The CPT counter is reset to 0. The RDY signal is set to 0.

[0094] At step T7, the LPSMODE signal is set to 0.

[0095] The SYS system described above can be used in a flow meter. Specifically, in such a flow meter, the LC sensor is used in combination with an impeller having at least one conductive portion and at least one non-conductive portion. The impeller is placed in a fluid flow so that it can be driven into rotation by the flow. The LC sensor, on the other hand, is fixed. The LC sensor generates oscillating analog signals. These oscillating analog signals are damped to varying degrees depending on the relative position of the LC sensor with respect to the conductive portion.

[0096] For example, the figure 4This shows two oscillating analog signals, SGN1 and SGN2, that can be generated by the LC sensor. The first signal, SGN1, is obtained when the LC sensor is near a conductive part of the wheel. The second signal, SGN2, is obtained when the LC sensor is near a non-conductive part of the wheel. It can be observed that the first signal, SGN1, is more damped than the second signal, SGN2.

[0097] The UT processing unit is configured to determine fluid flow rate from the wheel's rotational speed. The wheel's rotational speed is determined by analyzing the damping of oscillating analog signals generated by the LC sensor.

[0098] In particular, the relative position of the wheel with respect to the LC sensor is determined by counting the number of oscillations of the output signal transmitted to the processing unit UT that have an amplitude greater than a threshold S2. Determining the relative position of the LC sensor with respect to the conductive portion of the wheel at different times allows the rotational speed of the wheel and therefore the fluid flow rate to be deduced.

[0099] The processing unit UT thus counts the oscillations of the signal generated by the LC sensor with an amplitude between the threshold S1 and the threshold S2, the oscillations with an amplitude greater than S1 having been suppressed by the input / output cell IO.

[0100] It should be noted that suppressing the first oscillation(s) of the input signal has a negligible effect on determining the fluid flow rate. Indeed, approximately one hundred oscillations are typically taken into account when calculating the flow rate.

[0101] The general operation of such a flow meter is well known to those skilled in the art and is described in particular in note AN4636 entitled "Demonstration of LC sensor for gas or water metering based on STM32L073Z-EVAL and STM32L476RG-NUCLEO boards" published in September 2017 by STMicroelectronics and available on the website: https: / / www.st.com / content / ccc / resource / technical / document / application_note / 18 / 14 / 02 / 2d / dd / 8f / 4c / 93 / DM00151831.pdf / files / DM00151831.pdf / jcr:content / translations / en.DM00151831.pdf.

[0102] Of course, the present invention is susceptible to various variations and modifications which will become apparent to those skilled in the art. For example, as a variation of the CPT counter of the auxiliary control unit UC, it is possible to provide a timing circuit allowing the suppression of at least the first oscillation of the input signal so as to deliver in the output signal oscillations of the input signal having an amplitude below a threshold.

[0103] Furthermore, it is advantageous to double the CO converter. Two converters are then used in parallel. By doubling the CO converter, it is possible to increase the hysteresis in such a way as to immunize the signal delivered at the input of the auxiliary control unit (UC) from noise on the power supply of each CO converter.

Claims

1. An integrated circuit for conditioning an analogue oscillating signal comprising a succession of damped oscillations, the integrated circuit comprising an input / output (IO) cell including: - a first port (PAD) configured to receive said oscillating analogue signal, so-called the input signal, - a second port (ANA) configured to deliver an analogue output signal from the input signal, characterised by - control means including a switch connected between the first port and the second port, and configured to remove at least the first oscillation from the input signal so as to produce, in the output signal, oscillations of the input signal having an amplitude below a first threshold.

2. The integrated circuit according to claim 1, further comprising a processing unit (UT) connected to the second port, the first threshold being compatible with a maximum voltage level that the processing unit can tolerate.

3. The integrated circuit according to any one of claims 1 or 2, further comprising a main control unit (UPC) and wherein the control means include: - the switch controllable by the main control unit (UPC), - an auxiliary control unit (UC) configured to temporarily take control of the switch (INT) in place of the main control unit (UPC) so as to enable said suppression of at least the first oscillation from the input signal.

4. The integrated circuit according to claim 3, wherein - the switch (INT) is configured to operate in the presence of one or more oscillations of the input signal having an amplitude greater than or equal to said first threshold, and having a first terminal connected to the first port (PAD) and a second terminal connected to the second port (ANA), the switch being controllable: ∘ either in a closed state electrically connecting the first port (PAD) to the second port (ANA), ∘ or in an open state disconnecting the first port (PAD) from the second port (ANA), and - the auxiliary control unit (UC) is configured to: o hold the switch (INT) in an open state during the first oscillation of the input signal and possibly one or more oscillations directly succeeding the first oscillation, and then o allow the switch (INT) to be switched to a closed state.

5. The integrated circuit according to any one of claims 3 or 4, wherein the input / output cell further comprises a converter (CO) configured to convert the oscillating analogue signal into a square-wave signal and to deliver this square-wave signal to said auxiliary control unit (UC).

6. The integrated circuit according to claim 5, wherein the converter (CO) comprises a Schmitt trigger.

7. The integrated circuit according to any one of claims 3 to 6, wherein the auxiliary control unit (UC) comprises a counter (CPT) configured to count a defined number of edges of the square-wave signal from a first edge of the square-wave signal, the auxiliary control unit (UC) being configured to enable the switch (INT) to be switched to a closed state when the counter (CPT) reaches the defined number of rising edges.

8. The integrated circuit according to one of claims 2 to 7 taken in combination with claim 2, wherein the processing unit (UT) connected to the second port of the integrated circuit (ANA) is configured to count the number of oscillations of the output signal having an amplitude greater than a second threshold lower than the first threshold.

9. A system comprising: - an inductive capacitive sensor (LC), - an integrated circuit (IC) according to any one of claims 1 to 8, the first port of which is connected to the inductive capacitive sensor, the inductive capacitive sensor (LC) being adapted to deliver said oscillating analogue signal after an excitation phase triggered by the integrated circuit (IC).

10. A flowmeter comprising a system according to claim 9.

11. A method for conditioning an oscillating analogue signal comprising a succession of damped oscillations, in which method at least the first oscillation of the oscillating analogue signal is suppressed (21), by controlling a switch, and the other oscillations of the analogue oscillating signal having an amplitude below a first threshold are output in an analogue signal.