WO2021093351A1 - 流速侦测电路以及相关芯片以及流量计 - Google Patents

流速侦测电路以及相关芯片以及流量计 Download PDF

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Publication number
WO2021093351A1
WO2021093351A1 PCT/CN2020/101066 CN2020101066W WO2021093351A1 WO 2021093351 A1 WO2021093351 A1 WO 2021093351A1 CN 2020101066 W CN2020101066 W CN 2020101066W WO 2021093351 A1 WO2021093351 A1 WO 2021093351A1
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Prior art keywords
signal
transducer
time
flow rate
detection circuit
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PCT/CN2020/101066
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English (en)
French (fr)
Inventor
张鎔谕
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Shenzhen Goodix Technology Co Ltd
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Shenzhen Goodix Technology Co Ltd
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Priority to EP20774860.9A priority Critical patent/EP4043838A4/en
Priority to JP2020553540A priority patent/JP7026820B2/ja
Priority to US17/028,944 priority patent/US11512996B2/en
Publication of WO2021093351A1 publication Critical patent/WO2021093351A1/zh
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—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

Definitions

  • This application relates to a judgment circuit, and in particular to a flow rate detection circuit, related chips, and flow meters.
  • Ultrasonic flowmeter is a commonly used flowmeter. Flowmeters are widely used to detect the flow rate of fluids. Compared with other types of flowmeters, ultrasonic flowmeters have advantages in pressure loss, minimum detectable flow and In terms of installation cost and other aspects, they all have greater advantages, but the power consumption still needs to be reduced, and further improvement and innovation are needed.
  • One of the objectives of the present application is to disclose a judgment circuit, particularly a flow rate detection circuit, related chips and flow meters, to solve the above-mentioned problems.
  • An embodiment of the present application discloses a flow rate detection circuit, which is coupled to a first transducer and a second transducer outside the flow rate detection circuit, wherein the first transducer and the second transducer are The distance between the two transducers is greater than zero, and the fluid with a flow rate flows through the first transducer and the second transducer in sequence
  • the flow rate detection circuit includes: a transmitter coupled to The first transducer is used to provide a pre-signal and a main signal to the first transducer, and the first transducer converts the pre-signal and the main signal into a transducing signal for The second transducer, the second transducer converts the transducer signal into a receiving pre-signal and receiving a main signal to a receiver; and the receiver is coupled to the second transducer
  • the receiver includes: a pre-signal detection circuit for enabling the main signal processing circuit after receiving the reception pre-signal; and the main signal processing circuit for enabling the main signal processing circuit after being enabled The flow rate
  • An embodiment of the application discloses a chip.
  • the chip includes the aforementioned flow rate detection circuit.
  • An embodiment of the present application discloses a flow meter.
  • the flow meter includes the aforementioned chip.
  • the flow rate detection circuit disclosed in this application includes a receiver and a transmitter, and is used with a pair of transducers. During operation, one of the pair of transducers serves as the signal receiver, and the other as the signal transmitter.
  • the flow rate detection circuit can evaluate the time point when the transducer as the signal receiver receives the signal. Accordingly, the starting time point of enabling the receiver can be adjusted so that the starting time point is the same as the time point. Therefore, the receiver does not need to be kept in the enabled state all the time, so that the power consumption of the flow rate detection circuit when evaluating the flow rate can be reduced.
  • FIG. 1 is a schematic diagram of an embodiment in which the flow rate detection circuit of this application is applied to a flow meter.
  • FIG. 2 is a schematic diagram of the voltage waveform in the time domain related to the flow rate detection circuit of FIG. 1.
  • FIG. 3 is a block diagram of another embodiment of the flow rate detection circuit of this application.
  • FIG. 4 is a schematic diagram of the voltage waveform in the time domain related to the flow rate detection circuit of FIG. 3.
  • FIG. 5 is a schematic diagram of the voltage waveform in the time domain of the flow rate detection circuit according to another embodiment.
  • a device when a device is a rising edge triggered (active high), a signal is asserted and has a high logic value to activate the corresponding device. Otherwise, the signal is deasserted and has a low logic value to deactivate the corresponding device. However, when the device is a falling edge triggered (active low), the signal is validated and has a low logic value to activate the device, or the signal is disabled and has a high logic value to deactivate the device .
  • the flow rate of the fluid is measured by using a flow meter.
  • the flow meter includes at least a transmitter, a receiver, and a pair of transducers. During operation, one of the pair of transducers serves as the signal receiver, and the other as the signal transmitter. The receiver is enabled to evaluate the flow rate.
  • the receiver In order to accurately evaluate the flow rate, it must be ensured that the receiver receives a complete signal, that is, the signal is not truncated. In order to achieve this, one approach is to enable the receiver when the transmitter transmits a signal, but this approach runs counter to the purpose of reducing power consumption. Another approach is to pre-evaluate the maximum and minimum signal transmission time during the circuit design stage. Based on the maximum value and the minimum value, it is determined all possible time points at which the signal transmitted by the transmitter reaches the receiver. Based on all possible time points, the length of time for enabling the receiver is designed so that the receiver can receive a complete signal under all conditions, which will be described in detail in the comparative embodiment of FIG. 1 and FIG. 2. Since this implementation method needs to consider all possible time points, the time length is lengthened, which makes the power consumption of the flow meter inefficient. Conversely, if the length of time can not be lengthened, the power consumption can be made efficient.
  • the flow rate detection circuit of the present application can evaluate the time point when the signal transmitted by the transmitter reaches the receiver, so it is not necessary to consider all possible time points. Accordingly, the length of time for enabling the receiver does not need to be lengthened, so that the power consumption of the flow rate detection circuit is efficient, which will be described in detail in the embodiments of FIG. 3 and FIG. 4.
  • FIG. 1 is a schematic diagram of an embodiment in which the flow rate detection circuit 10 of this application is applied to a flow meter.
  • the flow rate detection circuit 10 is coupled to the first transducer 151 and the second transducer 152 outside the flow rate detection circuit 10.
  • a transducer is a device that converts one form of energy into another form. These energy forms may include electrical energy, mechanical energy, electromagnetic energy, light energy, chemical energy, sound energy, and thermal energy, etc. This application is not limited to many, and the transducer may include any device capable of converting energy.
  • the first transducer 151 and the second transducer 152 are installed in the pipeline 154, and the emission direction of the first transducer 151 faces the second transducer 152; the emission direction of the second transducer 152 faces First transducer 151.
  • the distance between the first transducer 151 and the second transducer 152 is L, and the distance L is greater than zero.
  • the fluid (for example, liquid or gas) having a flow rate V flows through the first transducer 151 and the second transducer 152 in sequence along the extension direction E of the pipeline 116.
  • the flow rate detection circuit 10 includes a first transmitter TX1, a first receiver RX1, a second transmitter TX2, and a second receiver RX2.
  • the first transmitter TX1 and the first receiver RX1 are coupled to the first transducer 151, and the second transmitter TX2 and the second receiver RX2 are coupled to the second transducer 152.
  • the first transmitter TX1 transmits the first transmission signal Se1 to the first transducer 151, and the first transducer 151 converts the first transmission signal Se1 into Transduction signal, and then transmit the energy conversion signal to the second transducer 152.
  • the second receiver RX2 receives the second received signal Sr2 from the second transducer 152.
  • the second transmitter TX2 is used as the starting point of the second type of signal transmission path, and the first receiver RX1 is used as the end point of the second type of signal transmission path. The process is similar to the signal transmission process of the first signal transmission path, and will not be repeated here.
  • the transmission time point of the first transmitter TX1 is regarded as the transmission time point of the first transducer 151;
  • the reception time point of the second transducer 152 is regarded as the reception time point of the second receiver RX2;
  • the transmission time point of the transmitter TX2 is regarded as the transmission time point of the second transducer 152;
  • the reception time point of the first transducer 151 is regarded as the reception time point of the first receiver RX1.
  • FIG. 2 only illustrates the operating principle of the flow rate detection circuit 10 related to the first signal transmission path.
  • FIG. 2 is a schematic diagram of a voltage waveform in the time domain related to the flow rate detection circuit 10 of FIG. 1.
  • the first transducer 151 is the signal transmitter and the second transducer 152 is the signal receiver. Accordingly, for the convenience of reading, the first transducer (TX) and the second transducer (RX) are shown in FIG. 2.
  • FIG. 2 shows waveforms 200, 202, 204, 206, and 208.
  • the waveform 200 represents the voltage waveform of the signal emitted by the first transducer 151, and the signal includes the main signal Sm.
  • the waveforms 202, 204, and 206 represent the voltage waveforms of the signals received by the second transducer 152 under different known operating environments.
  • the signals of the respective waveforms 202, 204, and 206 include the received main signal Smr, which corresponds to the main signal Sm, Wherein, the time length of the receiving main signal Smr is t RX , and there are different delay times between the receiving main signal Smr and the main signal Sm of the respective waveforms 202, 204, and 206.
  • the waveform 208 represents the voltage waveform of the signal used to enable the second receiver RX2, wherein the second receiver RX2 is enabled when the signal is at a high potential (high logic value).
  • the flow rate V is zero and the temperature is T1, where the temperature T1 is, for example, the highest temperature in the operating range of the flow meter. Since the flow rate V is zero, the signal transmission time of the signal in the fluid does not increase or decrease due to the flow rate V. In addition, the signal transmission time is also positively related to the temperature of the fluid as the signal transmission medium. Since the temperature T1 is the highest temperature, the signal transmission time does not increase due to the temperature T1.
  • This operating environment can be regarded as a standard operating environment, and the signal transmission time between the first transducer 151 and the second transducer 152 in the standard operating environment is the main signal Sm of the waveform 200 and The time difference between the received main signals Smr of the waveform 202 can be regarded as the reference time difference t DN .
  • the received main signal Smr arrives at the second receiver RX2 at time td.
  • the enable signal for enabling the second receiver RX2 is pulled to a positive edge at the time point td.
  • the reference time difference t DN and the time point td can be evaluated in the circuit design stage.
  • the flow rate V is maximum (labeled V MAX ) and the temperature is T1.
  • the signal transmission time of the signal in the fluid with the maximum flow rate V MAX is shorter than the signal transmission time when the flow rate V is zero.
  • the received main signal Smr of the waveform 204 reaches the second transducer 152 earlier than the main signal Sm of the waveform 202. That is, the first time difference ⁇ t dn is earlier than the time point td.
  • the signal transmission time in this operating environment can be regarded as the shortest signal transmission time.
  • the enable signal for enabling the second receiver RX2 is pulled to a positive edge at the time point (td- ⁇ t dn ).
  • the first time difference ⁇ t dn can be evaluated in the circuit design stage.
  • the flow rate V is zero and the temperature is T2, where the temperature T2 is lower than the temperature T1. Since the temperature T2 is lower than the temperature T1, the signal transmission time at the temperature T2 is longer than the signal transmission time at the temperature T1.
  • the received main signal Smr of the waveform 206 arrives at the second transducer 152 later than the main signal Sm of the waveform 202. That is, the second time difference ⁇ t dn_T is later than the time point td.
  • the signal transmission time in this operating environment can be regarded as the longest signal transmission time.
  • the enable signal for enabling the second receiver RX2 is pulled to a positive edge at the time point (td+ ⁇ t dn_T ).
  • the second time difference ⁇ t dn_T can be evaluated in the circuit design stage.
  • the waveforms 204 and 206 respectively represent the most early extreme situation and the most late extreme situation.
  • the time length of the signal enabling the second receiver RX2 is the same as the time length of the receiving main signal Smr as t RX , so that the second receiver RX2 can receive the complete receiving main signal.
  • Signal Smr the time difference between the actual operating environment and the operating environment of waveform 204.
  • the second receiver RX2 must be enabled for an additional length of time, that is, the first time difference ⁇ t dn to ensure that the second receiver RX2 can receive the complete The receiving main signal Smr.
  • the second receiver RX2 for another additional length of time, that is, the second time difference ⁇ t dn_T to ensure that the second receiver RX2 can receive To complete the received main signal Smr.
  • the total length of time that the second receiver RX2 needs to be enabled is the time length t RX , the first time difference ⁇ t dn and The sum of the second time difference ⁇ t dn_T.
  • the total time length is longer than the time length t RX of the main signal Sm.
  • FIG. 3 is a block diagram of another embodiment of the flow rate detection circuit 30 of this application.
  • the flow rate detection circuit 30 is similar to the flow rate detection circuit 10 of FIG. 1, the difference is that the flow rate detection circuit 30 includes a first transmitter TX11, a first receiver RX11, a second transmitter TX22 and a second receiver ⁇ RX22.
  • the first transmitter TX11 and the first receiver RX11 are coupled to the first transducer 151, and the second transmitter TX22 and the second receiver RX22 are coupled to the second transducer 152.
  • the first transmitter TX11 transmits the first transmission signal Se11 to the first transducer 151 on the first signal transmission path.
  • the first transmission signal Se11 includes a pre-signal and a main signal.
  • the first transducer 151 converts the first transmission signal Se11 into a conversion signal, and then transmits the conversion signal to the second transducer 152.
  • the second receiver RX22 receives the second received signal Sr22 from the second transducer 152.
  • the second received signal Sr22 includes the received preamble signal and the received main signal.
  • the second transmitter TX22 is used as the starting point of the second type of signal transmission path
  • the first receiver RX11 is used as the end point of the second type of signal transmission path. The process is similar to the signal transmission process of the first signal transmission path, and will not be repeated here.
  • the second receiver RX22 includes a pre-signal detection circuit 32 and a main signal processing circuit 34.
  • the main signal processing circuit 34 can be regarded as having the same function as the second receiver RX2 of FIG. 1. Therefore, the second receiver RX22 can be regarded as a combination of the second receiver RX2 of FIG. 1 and the additional pre-signal detection circuit 32.
  • the pre-signal detection circuit 32 is used to enable the main signal processing circuit 34 after receiving the reception pre-signal. That is to say, the start time point of enabling the main signal processing circuit 34 is determined by the pre-signal detection circuit 32, not based on the shortest signal transmission time and the longest signal transmission time described in the embodiment of FIG. The signal transmission time is determined, which is described in detail in the embodiment of FIG. 4. Therefore, the length of time for enabling the main signal processing circuit 34 does not need to add the first time difference ⁇ t dn and the second time difference ⁇ t dn_T .
  • the time length for enabling the main signal processing circuit 34 is longer than the total time length for enabling the second receiver RX2 (the total time length is the time length t RX , the first time difference ⁇ t dn and the second time difference The sum of ⁇ t dn_T ) is short. Therefore, the power consumption of the flow rate detection circuit 30 is more efficient than the power consumption of the flow rate detection circuit 10 of FIG. 1.
  • the main signal processing circuit 34 determines the flow rate V based on the received main signal after being enabled.
  • the main signal processing circuit 34 includes an analog front-end circuit, an analog-to-digital converter, and a judgment circuit.
  • the analog front-end circuit is used for receiving the main signal and outputting the analog signal to the analog-to-digital converter accordingly.
  • the analog-to-digital converter converts the analog signal into a digital signal, and outputs the digital signal to the judgment circuit, which judges the flow rate V based on the digital signal.
  • the front signal detection circuit 32 includes a detector 300 and a control unit 302.
  • the detector 300 is coupled to the second transducer 152 and used to detect and receive the pre-signal, and output an output signal Sd to the control unit 302 based on the detection result.
  • the detector 300 is a pulse wave detector. But this disclosure is not limited to this. In other embodiments, the detector 300 can also be provided as a corresponding detector depending on the type of the detected signal.
  • the detector 300 includes a comparator. The comparator judges whether the reception preamble signal is detected by comparing the reception preamble signal and the reference signal.
  • the control unit 302 is coupled between the detector 300 and the main signal processing circuit 34, and is used to output the enable signal EN to the detector 300, so that when the enable signal EN is asserted, the detector 300 Is enabled.
  • the control unit 302 receives the output signal Sd of the detector 300 and outputs the enable signal ENM to the main signal processing circuit 34. More specifically, the control unit 302 determines the time point to activate the enable signal ENM based on the detection result reflected by the output signal Sd.
  • the control unit 302 includes combinatorial logic. The working mechanism of the detector 300 and the control unit 302 will be described in detail in FIG. 4.
  • FIG. 4 is a schematic diagram of the voltage waveform in the time domain related to the flow rate detection circuit 30 of FIG. 3.
  • Figure 4 shows waveforms 400, 402, 404, 406, and 408.
  • the waveform 400 represents the voltage waveform of the first transmission signal Se11 transmitted by the first transmitter TX11, where the first transmission signal Se11 includes a main signal Smain and a preamble signal S pre , wherein the main signal Smain has a time length of Nmain, and the preamble signal S pre has a time length of Npre.
  • the first transmitter TX11 transmits the pre-signal S pre at the first time point t1, it transmits the main signal Smain after a decay time having at least a time length T gap.
  • both the main signal Smain and the pre-signal S pre are pulse wave signals, wherein the pulse wave signal includes at least one pulse wave.
  • the main signal Smain and the preamble signal S pre may be other suitable types of signals.
  • the waveform 402 represents the voltage waveform of the second received signal Sr22 received by the second receiver RX22.
  • the second received signal Sr22 includes the received pre-signal S pre ′ and the received main signal Smain ′. It can be seen from the waveform 402 that the reception pre-signal S pre ′ has been attenuated, and the attenuated reception pre-signal S pre ′ has an additional vibration part. Because of the attenuation time, the attenuated additional vibration part of the received pre-signal S pre ′ will not affect the received main signal Smain ′.
  • the waveform 404 represents the voltage waveform of the enable signal EN output by the control unit 302, wherein the detector 300 is enabled when the enable signal EN is at a high level.
  • the waveform 406 represents the voltage waveform of the output signal Sd output by the detector 300.
  • the waveform 408 represents the voltage waveform of the enable signal ENM output by the control unit 302, wherein the main signal circuit 34 is enabled when the enable signal ENM is at a high potential.
  • the first transmitter TX11 provides the pre-signal Spre at the first time point t1, and then transmits the main signal Smain to the first transducer 151 at the time point tmain after the decay time.
  • the second transducer 152 outputs the reception pre-signal Spre' and the reception main signal Smain'. It should be noted that the time length of receiving the preamble signal Spre' and the time length of receiving the main signal Smain' t RX can be evaluated in the circuit design stage.
  • the enable signal EN output by the control unit 302 is pulled to a positive edge after a standby time Ts/b with a time length from the first time point t1.
  • the detector 300 is enabled only after the standby time Ts/b with a length of time starts from the first time point t1, rather than being enabled from the first time point t1. Accordingly, the power consumption efficiency of the pre-signal detection circuit 32 can be further improved.
  • this disclosure is not limited to this. In other embodiments, the detector 300 can also be enabled from the first time point t1.
  • the detector 300 detects the reception pre-signal Spre' at a second time point t2.
  • the time point when the detector 300 detects the first pulse wave of the second received signal Sr22 is the second time point t2. Therefore, referring to the waveform 406, the output signal Sd output by the detector 300 starts to fluctuate at the second time point t2.
  • the control unit 302 estimates that the reception pre-signal Spre' arrives at the second receiver RX22 at the second time point t2 based on the output signal Sd.
  • the control unit 302 determines the time adjustment value based on the first time point t1 and the second time point t2, and enables the main signal processing circuit 34 based on the time adjustment value. In detail, the control unit 302 evaluates the evaluation time difference T tof between the first time point t1 and the second time point t2, where the evaluation time difference T tof is the actual signal transmission in the fluid during the operation of evaluating the flow rate V. time. It should be noted that although the evaluation time difference T tof is obtained by evaluating the pre-signal Spre instead of the main signal Smain, for the pre-signal Spre and the main signal Smain, the signal is in the fluid at the time of the operation of evaluating the flow rate V. The signal transmission time is the same.
  • the control unit 302 determines the time adjustment value according to the estimated time difference T tof and the reference time difference t DN.
  • the difference between the estimated time difference T tof and the reference time difference t DN means the difference between the signal transmission time at the time of the operation of evaluating the flow rate V and the signal transmission time under the standard operating environment.
  • the difference represents the time point when the received main signal Smain' arrives at the second receiver RX22 under the operation of evaluating the flow rate V, which is earlier or earlier than the standard arrival time point of the received main signal Smain' in the standard operating environment.
  • the amount of time late. Therefore, the difference is regarded as a time adjustment value.
  • the control unit 302 can estimate the time point when the received main signal Smain′ reaches the second receiver RX22 under the operation of evaluating the flow rate V based on the standard arrival time point and the time adjustment value. Next, the control unit 302 adjusts the starting time point t of enabling the main signal processing circuit 34 so that the starting time point t is the same as the estimated time point of reaching the second receiver RX22. That is to say, referring to the waveform 208, the control unit 302 pulls the enable signal ENM to a positive edge at the estimated time point when it reaches the second receiver RX22.
  • the length of time for enabling the main signal processing circuit 34 can be fixed to that of the received main signal Smain'
  • the time length t RX does not require additional consideration of the first time difference ⁇ t dn and the second time difference ⁇ t dn_T .
  • the time length during which the main signal processing circuit 34 is enabled is the same as the time length t RX during which the main signal Smain′ is received. Therefore, the length of time that the main signal processing circuit 34 is enabled is longer than the total length of time that the second receiver RX2 of FIG. 1 is enabled (the sum of the time length t RX , the first time difference ⁇ t dn and the second time difference ⁇ t dn_T ) short.
  • the second receiver RX22 additionally includes a pre-signal detection circuit 32.
  • the time length for enabling the main signal processing circuit 34 is shortened, and the shortened time length reduces the power consumption greater than the power consumption generated by the pre-signal detection circuit 32.
  • the pre-signal detection circuit 32 is not used to determine the flow rate, the circuit structure of the pre-signal detection circuit 32 is simple, and the power consumption generated by the pre-signal detection circuit 32 can be ignored. Therefore, the power consumption of the flow velocity detection circuit 30 of FIG. 3 of the present disclosure is lower than the power consumption of the flow velocity detection circuit 10 of FIG. 1.
  • the design of the standby time Ts/b will also consider the above-mentioned shortest signal transmission time and the above-mentioned longest signal transmission time.
  • the physical quantity of the fluid is a first value
  • the physical quantity of the fluid is a second value
  • Numerical value and the first flow time is shorter than the second flow time.
  • the first flow time is the aforementioned shortest signal transmission time
  • the second flow time is the aforementioned longest signal transmission time.
  • the physical quantity includes the temperature of the fluid or the flow rate V of the fluid. In some embodiments, the physical quantity includes a combination of the temperature of the fluid and the velocity V of the fluid.
  • the detector 300 in order to ensure that the pulse wave detected by the detector 300 is the first pulse wave of the pulse wave signal, it must be designed so that the standby time Ts/b is less than the fluid flow from the first transducer 151 to the second transducer.
  • the shortest time required by the energy converter 152 is the shortest transmission time mentioned above.
  • the detector 300 is not always kept in the enabled state. Therefore, the power consumption of the flow rate detection circuit 30 of FIG. 3 of the present disclosure is efficient.
  • this disclosure is not limited to this. In other embodiments, the detector 300 can always remain in the enabled state.
  • the power consumption of the pre-signal detection circuit 32 is negligible, because the detector 300 of the pre-signal detection circuit 32 is only used to detect the signal, not to determine the flow rate. Therefore, the circuit structure of the detector 300 is simple and has low power consumption. Even if the detector 300 is always kept in the enabled state, the power consumption of the flow velocity detection circuit 30 of FIG. 3 of the present disclosure is still lower than the power consumption of the flow velocity detection circuit 10 of FIG. 1.
  • the control unit 302 when the control unit 302 enables the main signal processing circuit 34, the control unit 302 disables the front signal detection circuit 32. In some embodiments, when the detector 300 detects the first pulse of the received pre-signal Spre' so that the control unit 302 enables the main signal processing circuit 34, the control unit can disable the detection ⁇ 300. Or, in some embodiments, it is desired to detect all pulse waves of the received pre-signal Spre'. To this end, the control unit further determines the end time point when the detector 300 is enabled. In detail, the control unit 302 determines the end of the detector 300 being enabled based on the longest time required for the fluid to flow from the first transducer 151 to the second transducer 152 (that is, the aforementioned longest transmission time) Point in time.
  • FIG. 5 is a schematic diagram of the voltage waveform in the time domain of the flow rate detection circuit according to another embodiment.
  • the voltage waveform diagram of FIG. 5 is similar to the voltage waveform diagram of FIG. 4, the difference is that the voltage waveform diagram of FIG. 5 includes a waveform 500.
  • the first transmitter TX11 sequentially transmits the preamble signal Spre and the reverse preamble signal Sbpre, and transmits the main signal Smain after the decay time, wherein the preamble signal Spre and the reverse preamble signal Sbpre have opposite phases .
  • the additional reverse pre-signal Sbpre helps to eliminate the extra vibration part of the pre-signal Spre.
  • the pre-signal Spre which eliminates the extra vibration part, cannot easily affect the main signal Smain.
  • the time for the magnitude of the received pre-signal Spre' as the preamble signal to return to zero can be reduced. Accordingly, the time length of the decay time can be further shortened, so that the working time of the first transmitter TX11 is reduced. Therefore, the power consumption of the flow rate detection circuit 30 can be further reduced.
  • the first transmitter TX11 transmits the main signal Smain immediately after transmitting the pre-signal Spre. If the quality factor of the first transducer 151 (or the second transducer 152) is very high, the received pre-signal Spre' as the preamble signal takes a long time to decay to a low level. Affect the received main signal Smain'. In order to avoid the occurrence of such a negative situation, it is necessary to increase the length T gap for a long time, thereby causing additional power consumption.
  • a chip includes the flow rate detection circuit 30.
  • the chip may be a semiconductor chip implemented in a different process.

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  • General Physics & Mathematics (AREA)
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Abstract

一种流速侦测电路（10,30），耦接于流速侦测电路（10,30）外部的第一换能器（151）及第二换能器（152），流速侦测电路（10,30）包括：发射器（TX11），耦接于第一换能器（151），并用以提供前置信号及主信号给第一换能器（151），第一换能器（151）将前置信号及所述主信号转换为换能信号给第二换能器（152），第二换能器（152）将换能信号转换为接收前置信号及接收主信号至接收器（RX22）；以及接收器（RX22），耦接于第二换能器（152），接收器（RX22）包括：前置信号侦测电路（32），用以在收到接收前置信号后才使能主信号处理电路（34）；以及主信号处理电路（34），用以在被使能后基于接收主信号判断流速。还提供一种芯片以及流量计。

Description

流速侦测电路以及相关芯片以及流量计 技术领域
本申请涉及一种判断电路，尤其涉及一种流速侦测电路以及相关芯片以及流量计。
背景技术
超声波流量计(ultrasonic flow meter)为常用的一种流量计，流量计广泛地应用在侦测流体的流速，相较于其他类的流量计，超声波流量计在压力损耗、最低可侦测流量及安装成本等方面，都占有较大的优势，但消耗功率仍有待降低，需要进一步改良及创新。
发明内容
本申请的目的之一在于公开一种判断电路，尤其涉及一种流速侦测电路以及相关芯片以及流量计，来解决上述问题。
本申请的一实施例公开了一种流速侦测电路，耦接于所述流速侦测电路外部的第一换能器及第二换能器，其中所述第一换能器和所述第二换能器之间的距离大于零，且具有流速的流体依序流经所述第一换能器和所述第二换能器，所述流速侦测电路包括：发射器，耦接于所述第一换能器，并用以提供前置信号及主信号给所述第一换能器，所述第一换能器将所述前置信号及所述主信号转换为换能信号给所述第二换能器，所述第二换能器将所述换能信号转换为接收前置信号及接收主信号至接收器；以及所述接收器，耦接于所述第二换能器，所述接收器包括：前置信号侦测电路，用以在收到所述接收前置信号后才使能主信号处理电路；以及所述主信号处理电 路，用以在被使能后基于所述接收主信号判断所述流速。
本申请的一实施例公开了一种芯片。所述芯片包括前述的流速侦测电路。
本申请的一实施例公开了一种流量计。所述流量计包括前述的芯片。
本申请所公开的流速侦测电路包括接收器及发射器，并且搭配一对换能器来使用。在操作时，所述对换能器的一者做为信号接收方，另一者做为信号发射方。所述流速侦测电路能够评估出做为信号接收方的换能器接收到信号的时间点。据此，能够调整使能所述接收器的开始时间点，以使所述开始时间点相同于所述时间点。因此，所述接收器不需要一直保持在使能状态，进而能够降低所述流速侦测电路在评估流速时的消耗功率。
附图说明
图1为本申请的流速侦测电路应用于流量计的实施例的示意图。
图2为相关于图1的流速侦测电路在时域中的电压波形示意图。
图3为本申请的另一流速侦测电路的实施例的方块示意图。
图4为相关于图3的流速侦测电路在时域中的电压波形示意图。
图5为另一实施例的流速侦测电路在时域中的电压波形示意图。
具体实施方式
在下文说明中，当一装置属于正缘触发(rising edge triggered；active high)，是使一信号生效(asserted)而具有高逻辑值，以启动该相应装置。反之，使该信号失效(deasserted)而具有低逻辑值，以停用该相应装置。然而当该装置属于负缘触发(falling edge  triggered；active low)时，系使该信号生效而具有低逻辑值，以启动该装置，或使该信号失效而具有高逻辑值，以停用该装置。
通常，通过使用流量计来量测流体的流速。所述流量计至少包括发射器、接收器以及一对换能器。在操作时，所述对换能器的一者做为信号接收方，另一者做为信号发射方。所述接收器被使能以评估所述流速。
为了准确地评估所述流速，必须确保所述接收器接收的是完整的信号，也就是所述信号没有被截断。为了达成此目的，一种作法是当所述发射器发射信号时，就开始使能所述接收器，但这种作法与降低消耗功率的目的相违背。另一种作法是在电路设计阶段时预先评估出信号传输时间的最大值及最小值。基于所述最大值及所述最小值，判断出所述发射器发射的信号到达所述接收器的所有可能的时间点。基于所有可能的时间点，来设计使能所述接收器的时间长度以使所述接收器在所有情况下都能够接收完整的信号，其将详细说明于图1及图2的比较实施例。由于这种实现方式需考虑到所有可能的时间点，因此所述时间长度被拉长，使得所述流量计的消耗功率没有效率。反之，若能够不拉长所述时间长度，就能够使消耗功率有效率。
本申请的流速侦测电路能够评估出所述发射器发射的信号到达所述接收器的时间点，因而不需要考虑所有可能的时间点。据此，使能所述接收器的时间长度不需要被拉长，进而使得所述流速侦测电路的消耗功率有效率，其将详细说明于图3及图4的实施例。
图1为本申请的流速侦测电路10应用于流量计的实施例的示意图。参照图1，流速侦测电路10耦接于流速侦测电路10外部的第一换能器151和第二换能器152。换能器是将一种形式的能量转化成另一种形式的器件。这些能量形式可能包括电能、机械能、电磁能、光能、化学能、声能和热能等，本申请并不多做限制，换能器可包括任何能够转化能量的器件。
第一换能器151和第二换能器152安装于管路154中，且第一换能器151的发射方向面对第二换能器152；第二换能器152的发射方向面对第一换能器151。第一换能器151和第二换能器152之间的距离为L，且距离L大于零。具有流速V的流体(例如液体或是气体)沿管路116的延伸方向E依序流过第一换能器151和第二换能器152。
流速侦测电路10包括第一发射器TX1、第一接收器RX1、第二发射器TX2及第二接收器RX2。第一发射器TX1及第一接收器RX1耦接于第一换能器151，以及第二发射器TX2及第二接收器RX2耦接于第二换能器152。
在评估流速V的操作中，在第一种信号传递路径上，第一发射器TX1发射第一发射信号Se1给第一换能器151，第一换能器151将第一发射信号Se1转换为换能信号，再将所述换能信号发射给第二换能器152。在第二换能器152将所述换能信号再度进行转换后，第二接收器RX2从第二换能器152接收第二接收信号Sr2。在第二种信号传递路径上，第二发射器TX2做为所述第二种信号传递路径的起始点，而第一接收器RX1做为所述第二种信号传递路径的终点，其信号传递过程类似于第一种信号传递路径的信号传递过程，于此不再赘述。
需注意的是，流速侦测电路10与第一换能器151及第二换能器152之间各自存在传输延时。所述传输延时引起的延时时间可在电路设计阶段被评估出来，并且在评估流速V时一并被考虑进去。但是，在本申请的下文中，为了能够清处理解及方便说明，不考虑所述延时时间。因此，第一发射器TX1的发射时间点视为是第一换能器151的发射时间点；第二换能器152的接收时间点视为是第二接收器RX2的接收时间点；第二发射器TX2的发射时间点视为是第二换能器152的发射时间点；以及，第一换能器151的接收时间点视为是第一接收器RX1的接收时间点。
流速侦测电路10的操作原理将详细说明于图2的实施例。此外，为了简洁，在图2中仅说明在流速侦测电路10相关于第一种信号传递路径的操作原理。
图2为相关于图1的流速侦测电路10在时域中的电压波形示意图。承如上述，由于图2讨论的是第一种信号传递路径，第一换能器151为信号发射方以及第二换能器152为信号接收方。据此，为了方便阅读，在图2中显示为第一换能器(TX)及第二换能器(RX)。
参照图2，图2显示波形200、202、204、206及208。波形200代表第一换能器151所发射的信号的电压波形，所述信号包括主信号Sm。波形202、204及206代表在不同的已知操作环境下第二换能器152所接收的信号的电压波形，其中各个波形202、204及206的信号包括接收主信号Smr，对应主信号Sm，其中，所述接收主信号Smr的时间长度为t RX，各个波形202、204及206的所述接收主信号Smr与主信号Sm之间存在不同的延时时间。波形208代表用于使能第二接收器RX2的信号的电压波形，其中所述信号在高电位(高逻辑值)时第二接收器RX2被使能。
参照波形202，在此操作环境中，流速V为零且温度为T1，其中温度T1例如是流速计的操作范围中的最高温度。由于流速V为零，信号在所述流体中的信号传输时间不因流速V增加或减少。此外，所述信号传输时间还正相关于做为所述信号的传输媒介的所述流体的温度。由于温度T1为最高温度，所述信号传输时间不因温度T1而增加。这种操作环境可视为是标准操作环境，并且在所述标准操作环境下的第一换能器151及第二换能器152之间的信号传输时间，也就是波形200的主信号Sm与波形202的所述接收主信号Smr之间的时间差，可视为是参考时间差t DN。此外，所述接收主信号Smr于时间点td抵达第二接收器RX2。为了使第二接收器RX2接收所述接收主信号Smr，参照波形208，将使能第二接收器RX2的使能信号于时间点td拉至正缘。参考时间差t DN及时间点td在电路设计阶段是可以被评估出来的。
参照波形204，在此操作环境中，流速V为最大(标记为V MAX)且温度为T1。信号在最大流速V MAX的流体中的信号传输时间比在流速V为零的信号传输时间短。比较波形202及204后也可以观察出，波形204的所述接收主信号Smr比波形202的主信号Sm更早到达第二换能器152。也就是，比时间点td提早了第一时间差△t dn。此操作环境下的信号传输时间可视为是最短信号传输时间。为了使第二接收器RX2接收所述接收主信号Smr，参照波形208，将使能第二接收器RX2的使能信号于时间点(td-△t dn)拉至正缘。第一时间差△t dn在电路设计阶段是可以被评估出来的。
参照波形206，在此操作环境中，流速V为零且温度为T2，其中温度T2低于温度T1。由于温度T2低于温度T1，信号在温度T2下的信号传输时间比在温度T1下的信号传输时间长。比较波形202及206后也可以观察出，波形206的所述接收主信号Smr比波形202的主信号Sm更晚到达第二换能器152。也就是，比时间点td晚到了第二时间差△t dn_T。此操作环境下的信号传输时间可视为是最长信号传输时间。为了使第二接收器RX2接收所述接收主信号Smr，参照波形208，将使能第二接收器RX2的使能信号于时间点(td+△t dn_T)拉至正缘。第二时间差△t dn_T在电路设计阶段是可以被评估出来的。
当操作环境只有温度及流速这两种变数时，波形204及206各自代表提早最多的极端情况及晚到最多的极端情况。在标准操作环境中，让使能第二接收器RX2的信号的时间长度相同于所述接收主信号Smr的时间长度为t RX，就能够让第二接收器RX2接收到完整的所述接收主信号Smr。但考虑到实际操作环境可能如同波形204的操作环境，因此必须使能第二接收器RX2额外的时间长度，也就是第一时间差△t dn，才能够确保第二接收器RX2能够接收到完整的所述接收主信号Smr。类似地，考虑实际操作环境可能如同波形206的操作环境，因此必须使能第二接收器RX2另一额外的时间长度，也就是第二时间差△t dn_T，才能够确保第二接收器RX2能够接收到 完整的所述接收主信号Smr。
总的来说，为了确保第二接收器RX2能够接收到完整的所述接收主信号Smr，第二接收器RX2需要被使能的总时间长度为时间长度t RX、第一时间差△t dn及第二时间差△t dn_T的总和。所述总时间长度比主信号Sm的时间长度t RX长。当使用具有所述总时间长度的信号使能第二接收器RX2时，可能会发生第二接收器RX2已经被使能但是主信号Sm还没抵达第二接收器RX2的情况。因此，消耗功率没有效率。
图3为本申请的另一流速侦测电路30的实施例的方块示意图。参照图3，流速侦测电路30类似于图1的流速侦测电路10，差别在于，流速侦测电路30包括第一发射器TX11、第一接收器RX11、第二发射器TX22及第二接收器RX22。第一发射器TX11及第一接收器RX11耦接于第一换能器151，以及第二发射器TX22及第二接收器RX22耦接于第二换能器152。
在评估流速V的操作中，在第一种信号传递路径上，第一发射器TX11发射第一发射信号Se11给第一换能器151。第一发射信号Se11包括前置信号及主信号。第一换能器151将第一发射信号Se11转换为换能信号，再将所述换能信号发射给第二换能器152。在第二换能器152将所述换能信号再度进行转换为第二接收信号Sr22后，第二接收器RX22从第二换能器152接收第二接收信号Sr22。第二接收信号Sr22包括接收前置信号及接收主信号。在第二种信号传递路径上，第二发射器TX22做为所述第二种信号传递路径的起始点，而第一接收器RX11做为所述第二种信号传递路径的终点，其信号传递过程类似于第一种信号传递路径的信号传递过程，于此不再赘述。
基于与图1及图2的实施例中提及的相同理由，在图3及图4的实施例中，为了能够清处理解及方便说明，不考虑流速侦测电路30与第一换能器151及第二换能器152之间各自存在的传输延时导 致的延时时间。
第二接收器RX22包括前置信号侦测电路32以及主信号处理电路34。主信号处理电路34可以被视为具有相同于图1的第二接收器RX2的功能。因此，第二接收器RX22可视为是图1的第二接收器RX2与额外的前置信号侦测电路32的组合。
前置信号侦测电路32用以在收到接收前置信号后才使能主信号处理电路34。也就是说，使能主信号处理电路34的开始时间点是由前置信号侦测电路32来决定，而不是基于图1的实施例所描述的基于所述最短信号传输时间及所述最长信号传输时间来决定，其详细说明于图4的实施例。因此，使能主信号处理电路34的时间长度不需要加入第一时间差△t dn及第二时间差△t dn_T。也就是说，使能主信号处理电路34的时间长度比使能第二接收器RX2的所述总时间长度(所述总时间长度为时间长度t RX、第一时间差△t dn及第二时间差△t dn_T的总和)短。因此，流速侦测电路30的消耗功率比图1的流速侦测电路10的消耗功率有效率。
主信号处理电路34在被使能后基于接收主信号判断流速V。在一些实施例中，主信号处理电路34包括模拟前端电路、模数转换器及判断电路。模拟前端电路用以接收所述主信号，并据以输出模拟信号至模数转换器。模数转换器将所述模拟信号转换为数字信号，并将所述数字信号输出至所述判断电路，所述判断电路基于所述数字信号判断流速V。
以下将进一步说明前置信号侦测电路32包括的功能方块。需注意的是，本揭露并未限制前置信号侦测电路32只能以下述的功能方块来实施。在本实施例中，前置信号侦测电路32包括侦测器300以及控制单元302。
侦测器300耦接于第二换能器152，并用以侦测接收前置信号，并基于侦测结果输出输出信号Sd至控制单元302。在本实施例中，侦测器300为脉波侦测器。但本揭露不限定于此。在其他实施例中， 侦测器300也可视所侦测信号的类型而被提供为相应的侦测器。在一些实施例中，侦测器300包括比较器。所述比较器通过比较所述接收前置信号及参考信号来判断是否侦测到接收前置信号。
控制单元302耦接于侦测器300及主信号处理电路34之间，并用以输出使能信号EN至侦测器300，以至于使能信号EN被有效化(asserted)时，侦测器300被使能。此外，控制单元302接收侦测器300的输出信号Sd并输出使能信号ENM至主信号处理电路34。更明确来说，控制单元302基于输出信号Sd反应出的侦测结果决定有效化使能信号ENM的时间点。在一些实施例中，控制单元302包括组合逻辑。侦测器300以及控制单元302的工作机制将详细说明于图4。
图4为相关于图3的流速侦测电路30在时域中的电压波形示意图。参照图4，图4显示波形400、402、404、406及408。波形400代表第一发射器TX11所发射的第一发射信号Se11的电压波形，其中第一发射信号Se11包括主信号Smain及前置信号S pre，其中主信号Smain具有时间长度Nmain，而前置信号S pre具有时间长度Npre。详言之，第一发射器TX11于第一时间点t1发射前置信号S pre后，经历至少具有时间长度T gap的衰减时间后再发射主信号Smain。所述衰减时间是为了确保当前置信号S pre衰减时，衰减的前置信号S pre的额外振动部分不会影响到主信号Smain。在本实施例中，主信号Smain及前置信号S pre均为脉波信号，其中所述脉波信号包括至少一脉波。然而，本揭露不限定于此。在其他实施例中，主信号Smain及前置信号S pre可以是其他适合型态的信号。
波形402代表第二接收器RX22所接收的第二接收信号Sr22的电压波形。第二接收信号Sr22包括接收前置信号S pre’及接收主信号Smain’。由波形402可看出，所述接收前置信号S pre’已经衰减，并且衰减的所述接收前置信号S pre’具有额外振动部分。因为具有所述衰减时间，衰减的所述接收前置信号S pre’的额外振动部分不会影响到所述接收主信号Smain’。
需说明的是，基于与在图2的波形202的讨论中所描述的相同理由，可以在电路设计阶段评估出，在标准操作环境下，信号在流体中的信号传输时间，以及所述接收主信号Smain’及所述接收前置信号S pre’各自到达第二接收器RX22的标准抵达时间点。为了方便理解，在标准操作环境下，在图4中的所述信号传输时间相同于图2的所述信号传输时间，均为参考时间差t DN。
波形404代表控制单元302输出的使能信号EN的电压波形，其中使能信号EN在高电位时侦测器300被使能。波形406代表侦测器300输出的输出信号Sd的电压波形。波形408代表控制单元302输出的使能信号ENM的电压波形，其中使能信号ENM在高电位时主信号电路34被使能。
操作时，参照波形400，第一发射器TX11于第一时间点t1提供前置信号Spre，经历衰减时间后于时间点tmain再发射主信号Smain至第一换能器151。经过第一换能器151及第二换能器152之间的传输后，参照波形402，第二换能器152输出所述接收前置信号Spre’及所述接收主信号Smain’。需注意的是，所述接收前置信号Spre’的时间长度及所述接收主信号Smain’的时间长度t RX在电路设计阶段是可以被评估出来的。参照波形404，控制单元302输出的使能信号EN从第一时间点t1开始经历具有时间长度的待机时间Ts/b后才被拉至正缘。也就是说，侦测器300从第一时间点t1开始经历具有时间长度的待机时间Ts/b后才被使能，而不是从第一时间点t1就被使能。据此，可以进一步提升前置信号侦测电路32的消耗功率的效率。然而，本揭露不限定于此。在其他实施例中，也可以从第一时间点t1就开始使能侦测器300。
接着，侦测器300于第二时间点t2侦测到所述接收前置信号Spre’。详细来说，侦测器300侦测到第二接收信号Sr22的第一个脉波的时间点为第二时间点t2。因此，参照波形406，侦测器300输出的输出信号Sd于第二时间点t2开始变动。控制单元302基于输出信号Sd评估出所述接收前置信号Spre’于第二时间点t2抵达第 二接收器RX22。
控制单元302基于第一时间点t1及第二时间点t2决定时间调整值，并基于所述时间调整值来使能主信号处理电路34。详细来说，控制单元302评估出第一时间点t1及第二时间点t2之间的评估时间差T tof，其中评估时间差T tof就是在评估流速V的操作当下信号实际上在流体中的信号传输时间。需说明的是，虽然评估时间差T tof是对前置信号Spre而非对主信号Smain评估得到，但是对于前置信号Spre及主信号Smain来说，在评估流速V的操作当下信号在流体中的信号传输时间是相同的。
控制单元302依据评估时间差T tof和参考时间差t DN决定时间调整值。详细来说，评估时间差T tof及参考时间差t DN之间的差值意味着，在评估流速V的操作当下的信号传输时间与在标准操作环境下的信号传输时间的差值。所述差值就代表所述接收主信号Smain’在评估流速V的操作下抵达第二接收器RX22的时间点，比所述接收主信号Smain’在标准操作环境下的标准抵达时间点提早或晚到的时间量。因此，所述差值视为是时间调整值。控制单元302基于标准抵达时间点及所述时间调整值就能够评估出所述接收主信号Smain’在评估流速V的操作下抵达第二接收器RX22的时间点。接着，控制单元302调整使能主信号处理电路34的开始时间点t，以使开始时间点t相同于评估出的抵达第二接收器RX22的时间点。也就是说，参照波形208，控制单元302在评估出的抵达第二接收器RX22的时间点将使能信号ENM拉至正缘。
由于能够在线上(on-line)评估出所述接收主信号Smain’到达第二接收器RX22的时间点，因此使能主信号处理电路34的时间长度可以固定为所述接收主信号Smain’的时间长度t RX，而不需要额外考虑第一时间差△t dn及第二时间差△t dn_T。简单来说，主信号处理电路34被使能的时间长度与所述接收主信号Smain’的时间长度t RX相同。因此主信号处理电路34被使能的时间长度比图1的第二接收器RX2被使能的总时间长度(时间长度t RX、第一时间差△t dn及第 二时间差△t dn_T的总和)短。
第二接收器RX22相较于图1的第二接收器RX2额外包括前置信号侦测电路32。但是，因为使能主信号处理电路34的时间长度缩短了，并且缩短时间长度减少的消耗功率大于前置信号侦测电路32产生的消耗功率。甚至于，因为前置信号侦测电路32不是用来判断流速因而前置信号侦测电路32的电路结构简单，前置信号侦测电路32产生的消耗功率可以忽略不计。因此，本公开的图3的流速侦测电路30的消耗功率比图1的流速侦测电路10的消耗功率低。
参回至波形404，需注意的是，待机时间Ts/b的设计也会考虑上述的最短信号传输时间及上述的最长信号传输时间。总的来说，在所述流体的物理量为第一数值时，所述流体从第一换能器151流至第二换能器152需要第一流动时间。在所述流体的所述物理量为第二数值时，所述流体从第一换能器151流至第二换能器152需要第二流动时间，其中所述第二数值不同于所述第一数值，且所述第一流动时间短于所述第二流动时间。所述第一流动时间就是上述的最短信号传输时间，以及所述第二流动时间就是上述的最长信号传输时间。在一些实施例中，所述物理量包括所述流体的温度或所述流体的流速V。在一些实施例中，所述物理量包括所述流体的温度及所述流体的速度V的组合。
进一步来说，为了确保侦测器300所侦测到的脉波是脉波信号的第一根脉波，必须设计让待机时间Ts/b小于流体从第一换能器151流至第二换能器152所需的最短时间，也就是上述的最短传输时间。换言之，侦测器300不是一直保持在使能状态。因此，本公开的图3的流速侦测电路30的消耗功率有效率。然而，本揭露不限定于此。在其他实施例中，侦测器300能够一直保持在使能状态。如前所述，前置信号侦测电路32的消耗功率可以忽略不计，是因为前置信号侦测电路32的侦测器300只是用来侦测信号，而不是用来判断流速。因此，侦测器300的电路结构简单而具有低消耗功率。即使侦测器300一直保持在使能状态，本公开的图3的流速侦测电 路30的消耗功率仍然比图1的流速侦测电路10的消耗功率低。
此外，为了进一步降低消耗功率，当控制单元302使能主信号处理电路34时，控制单元302禁能前置信号侦测电路32。在一些实施例中，当侦测器300侦测到所述接收前置信号Spre’的第一根脉波以使控制单元302使能主信号处理电路34后，控制单元就可以禁能侦测器300。或者，在一些实施例中，想要侦测到所述接收前置信号Spre’的所有的脉波。为此，控制单元进一步决定侦测器300被使能的结束时间点。详细来说，控制单元302基于流体从第一换能器151流至第二换能器152所需的最长时间(也就是前述的最长传输时间)决定侦测器300被使能的结束时间点。
图5为另一实施例的流速侦测电路在时域中的电压波形示意图。参照图5，图5的电压波形图类似于图4的电压波形图，差别在于，图5的电压波形图包括波形500。参照波形500，第一发射器TX11依序发射前置信号Spre及反向前置信号Sbpre，并且经历衰减时间后再发射主信号Smain，其中前置信号Spre及反向前置信号Sbpre的相位相反。额外增加的反向前置信号Sbpre有助于消除前置信号Spre的额外振动部分。消除额外振动部分的前置信号Spre不容易影响到主信号Smain。简单来说，可减少做为前导讯号的接收前置信号Spre’的大小变回数值零的时间。据此，衰减时间的时间长度可以进一步被缩短，使得第一发射器TX11的工作时间降低。因此，流速侦测电路30的消耗功率可以进一步被降低。
相反地，在一些比较实施例中，第一发射器TX11在发射前置信号Spre后就紧接著发射主信号Smain。若第一换能器151(或第二换能器152)的品质因数(quality factor)很高时，做为前导讯号的所述接收前置信号Spre’需要较长的时间才会衰减到不影响所述接收主信号Smain’。为了避免造成此种负面情况发生，需加长时间长度T gap，因而造成额外的消耗功率。
在一些实施例中，一种芯片包括流速侦测电路30，举例来说该 芯片可以是不同工艺实现的半导体芯片。

Claims (18)

  1. 一种流速侦测电路，耦接于所述流速侦测电路外部的第一换能器及第二换能器，其中所述第一换能器和所述第二换能器之间的距离大于零，且具有流速的流体依序流经所述第一换能器和所述第二换能器，所述流速侦测电路包括：
    发射器，耦接于所述第一换能器，并用以提供前置信号及主信号给所述第一换能器，所述第一换能器将所述前置信号及所述主信号转换为换能信号给所述第二换能器，所述第二换能器将所述换能信号转换为接收前置信号及接收主信号至接收器；以及
    所述接收器，耦接于所述第二换能器，所述接收器包括：
    前置信号侦测电路，用以在收到所述接收前置信号后才使能主信号处理电路；以及
    所述主信号处理电路，用以在被使能后基于所述接收主信号判断所述流速。
  2. 如权利要求1所述的流速侦测电路，其中所述发射器于第一时间点提供所述前置信号，所述前置信号侦测电路包括：
    侦测器，耦接于所述第二换能器，并于第二时间点侦测到所述接收前置信号；以及
    控制单元，耦接于所述侦测器及所述主信号处理电路之间，用以基于所述第一时间点及所述第二时间点决定时间调整值，并基于所述时间调整值来使能所述主信号处理电路。
  3. 如权利要求2所述的流速侦测电路，其中所述控制单元基于所述时间调整值调整使能所述主信号处理电路的开始时间点。
  4. 如权利要求3所述的流速侦测电路，其中所述控制单元进一步评估出所述第一时间点及所述第二时间点之间的评估时间差，并依据所述评估时间差和参考时间差决定所述时间调整值。
  5. 如权利要求4所述的流速侦测电路，其中所述参考时间差为在已知操作环境下所述第一换能器及所述第二换能器之间的信息传输时间。
  6. 如权利要求2所述的流速侦测电路，其中所述前置信号是脉波信号，所述脉波信号包括至少一脉波，以及其中所述侦测器为脉波侦测器，其中所述脉波侦测器侦测到所述脉波信号的第一个脉波的时间点为所述第二时间点。
  7. 如权利要求2所述的流速侦测电路，其中所述侦测器从所述第一时间点开始经历待机时间后才被使能。
  8. 如权利要求7所述的流速侦测电路，
    其中在所述流体的物理量为第一数值时，所述流体从所述第一换能器流至所述第二换能器需要第一流动时间，
    其中在所述流体的所述物理量为第二数值时，所述流体从所述第一换能器流至所述第二换能器需要第二流动时间，其中所述第二数值不同于所述第一数值，且所述第一流动时间短于所述第二流动时间，以及
    其中所述待机时间小于所述第一流动时间。
  9. 如权利要求8所述的流速侦测电路，其中所述控制单元基于所述第二流动时间决定所述侦测器被使能的结束时间点。
  10. 如权利要求9所述的流速侦测电路，其中所述物理量包括所述流体的温度或所述流体的所述流速。
  11. 如权利要求2所述的流速侦测电路，其中当所述控制单元使能所述主信号处理电路时，所述控制单元禁能所述侦测器。
  12. 如权利要求1所述的流速侦测电路，其中所述发射器发射所述前置信号后，经历至少具有时间长度的衰减时间后再发射所述主信号。
  13. 如权利要求12所述的流速侦测电路，其中所述发射器依序发射所述前置信号及反向前置信号，并且经历所述衰减时间后再发射所述主信号。
  14. 如权利要求13所述的流速侦测电路，其中所述前置信号及所述反向前置信号的相位相反。
  15. 如权利要求2所述的流速侦测电路，其中当所述侦测器操作时，所述侦测器具有第一消耗功率，以及当所述主信号处理电路操作时，所述主信号处理电路具有第二消耗功率，其中所述第二消耗功率高于所述第一消耗功率。
  16. 如权利要求1所述的流速侦测电路，其中所述主信号处理电路被使能的时间长度与所述接收主信号的时间长度相同。
  17. 一种芯片，包括：
    如权利要求1-16任意一项所述的流速侦测电路。
  18. 一种流量计，包括：
    如权利要求17所述的芯片；以及
    所述第一换能器；以及
    所述第二换能器。
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