CN111721997A - Current detection method, current detection device and water meter - Google Patents
Current detection method, current detection device and water meter Download PDFInfo
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- CN111721997A CN111721997A CN202010612780.0A CN202010612780A CN111721997A CN 111721997 A CN111721997 A CN 111721997A CN 202010612780 A CN202010612780 A CN 202010612780A CN 111721997 A CN111721997 A CN 111721997A
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- 238000001514 detection method Methods 0.000 title claims abstract description 80
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 26
- 239000003990 capacitor Substances 0.000 claims abstract description 207
- 238000000034 method Methods 0.000 claims description 33
- 238000007599 discharging Methods 0.000 claims description 6
- 238000005070 sampling Methods 0.000 abstract description 7
- 230000003750 conditioning effect Effects 0.000 abstract description 2
- 230000007958 sleep Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 230000005059 dormancy Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/003—Measuring mean values of current or voltage during a given time interval
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
Abstract
The invention provides a current detection method, a current detection device and a water meter, which are used for acquiring the average current of a load in a detection time period by detecting the voltage change on a capacitor so as to represent the power consumption of the load. The current detection method provided by the invention does not need to use a current sampling and amplifying conditioning circuit and a detection mode switching control circuit, so that the problem of easy interference caused by weak signal detection is avoided, the problem of load voltage drop during mode switching is avoided, the introduced power consumption is low, and the low-power-consumption performance of an electronic product is favorably improved.
Description
Technical Field
The invention belongs to the technical field of current detection, and particularly relates to a current detection method, a current detection device and a water meter.
Background
The power consumption performance of electronic products is getting more and more attention and attention of electronic product researchers and users, and therefore the supply current of the electronic products needs to be detected as a characteristic parameter of the power consumption of the electronic products. For example, in order to ensure that a product is required to have low power consumption when leaving a factory in an existing intelligent water meter, the battery supply current of an electronic module in the intelligent water meter needs to be detected.
Fig. 1 is a schematic diagram of a main power supply circuit of an existing intelligent water meter, in order to improve instantaneous current output capability, a large-capacity capacitor C is connected in parallel with an output end of a battery BAT, and in order to prevent current from being rewound to the battery BAT, an output end of the battery BAT is connected with a diode D. As shown in fig. 2, which is a schematic diagram of a main circuit for current detection of an intelligent water meter in the prior art, a resistor R is in a power supply loop of a battery BAT, the battery BAT supplies power to a load through a switch S1 while charging a capacitor C, when the switch S1 is turned off and a switch S2 is turned on, the capacitor C supplies power to the load through the switch S2 and the resistor R, a voltage drop across the resistor R is passed, and then a current flowing through the resistor is calculated through ohm' S law. When the intelligent water meter is in communication or user operation, the current is very large and reaches dozens or even hundreds of mA, but when the water meter enters low-power-consumption dormancy, the current is only dozens or even hundreds of mA, in order to reduce the voltage drop on the resistor R during heavy current and ensure the working voltage of a load and the detection precision of the measured muA-level current, the current detection circuit shown in figure 2 needs to be additionally provided with a mode switching control circuit to control the conduction of a switch S1 and the disconnection of an S2 when the heavy current works, so that the muA-level current detection circuit is bypassed, and when the low current is in dormancy, the control switch S1 is disconnected and the S2 is switched to the muA-level current detection circuit. In fig. 2, the voltage across the resistor R is sampled by the voltage detection conditioning circuit, and since the current across the resistor is μ a level during sampling, the current is easily affected by circuit noise of the resistor, electromagnetic interference from a load circuit and the environment, and the like, the detection error is increased, a filter circuit or a filter algorithm needs to be added for processing, the complexity is increased, and the detection consistency is deteriorated. In addition, the current detection technology is based on the working state of the water meter and the detected current value when the power supply path switching control is performed, because the working state of the water meter can be changed due to external operation, the randomness is provided, and the current effective value can be sampled only when the control switch is switched to the current detection loop. Therefore, when the control switch is switched to the muA-level current detection circuit, the water meter cannot be guaranteed to work in a dormant state of muA-level current, the load voltage can drop obviously at the moment, and particularly when the battery voltage is at a low level, the single chip microcomputer is reset due to power failure. The existing current detection method can introduce two parts of power consumption increase, one part is directly consumed on the sampling resistor, and the other part is consumed by the voltage detection circuit, so that the design requirement of low power consumption of electronic products is not favorably met.
Disclosure of Invention
In view of this, the invention provides a current detection method, a current detection device and a water meter, so as to solve the problems of complex implementation, low stability and high introduced power consumption of the existing current detection method.
A current sensing method, comprising:
step 11: the battery is enabled to supply power to the load and charge a capacitor which is connected with the load in parallel and is arranged at the output end of the battery,
step 12: detecting a voltage on the capacitor during charging of the capacitor,
step 13: recording the moment when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage as a first moment, and acquiring a first voltage on the capacitor at the first moment,
step 14: stopping the battery from supplying power to the load after the first time, wherein the capacitor supplies power to the load,
step 15: recording the moment when the voltage on the capacitor drops to be equal to or less than a set second threshold voltage as a second moment in the process that the capacitor supplies power to the load, and acquiring a second voltage on the capacitor at the second moment,
step 16: and returning to the step 11 after the second moment, and calculating the average supply current of the load from the first moment to the second moment according to the first voltage, the second voltage and the capacitance value of the capacitor.
Preferably, the current detection method further includes periodically calibrating the capacitance value of the capacitor, stopping detecting the supply current in the process of calibrating the capacitor, continuing to detect the supply current after the calibration of the capacitor is completed, and calculating the average supply current according to the calibrated capacitance value of the capacitor.
Preferably, the step of periodically calibrating the capacitance value of the capacitor comprises:
step 21: when the capacitance value of the capacitor needs to be calibrated, the capacitor is charged while the battery supplies power to the load,
step 22: detecting a voltage on the capacitor during charging of the capacitor,
step 23: recording a third moment when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage, and recording a third voltage on the capacitor at the third moment,
step 24: after the third time, the battery is enabled to continuously supply power to the load, the capacitor discharges the resistor,
step 25: recording a fourth time when the voltage on the capacitor drops to be equal to or less than a set fourth threshold voltage in the process that the capacitor discharges the resistor, and recording a fourth voltage on the capacitor at the fourth time,
step 26: and calculating the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage, the fourth voltage and the difference value between the fourth moment and the third moment to serve as the calibrated capacitance value of the capacitor.
A current detecting device, comprising:
a first switching unit connected between the power supply battery and the load,
a capacitor connected in parallel with the load at the output of the battery,
a second switching unit connected in series with the capacitor,
a control unit configured to control on-off states of the first switch unit and the second switch according to a voltage on the capacitor, obtain a first voltage on the capacitor at a first time and a second voltage on the capacitor at a second time, and calculate an average supply current of the load from the first time to the second time according to the first voltage, the second voltage, and a capacitance value of the capacitor,
wherein the first time is a time when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage in the process that the battery charges the capacitor, the second time is a time when the voltage on the capacitor drops to be equal to or less than a set second threshold voltage in the process that the capacitor supplies power to the load,
when the first switch unit and the second switch unit are both on, the battery supplies power to the load through the first switch unit and charges the battery through the first switch unit and the second switch unit in sequence,
after the first moment, the first switch unit is switched off, the capacitor supplies power to the load through the second switch unit, and after the second moment, the first switch unit is switched on.
Preferably, the current detection device further comprises a capacitance calibration unit,
the control unit controls the capacitance calibration unit to periodically calibrate the capacitance value of the capacitor, controls the current detection device to stop detecting the power supply current of the load in the calibration process of the capacitor, continues to detect the power supply current after the calibration of the capacitance of the capacitor is completed, and calculates the average power supply current according to the calibrated capacitance value of the capacitor.
Preferably, the capacitance calibration unit includes a third switching unit and a resistor, which are connected in series between the output terminal of the capacitor and a reference ground terminal,
when the capacitance value of the capacitor needs to be calibrated, the control unit controls the on-off states of the first switch unit, the second switch unit and the third switch unit according to the voltage on the capacitor, and calculates the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage on the capacitor at a third moment, the fourth voltage on the capacitor at a fourth moment and the difference value between the fourth moment and the third moment to serve as the calibrated capacitance value of the capacitor,
wherein the third time is a time when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage in the process of charging the capacitor by the battery, the fourth time is a time when the voltage on the capacitor falls to be equal to or less than a set fourth threshold voltage in the process of discharging the resistor by the capacitor,
when the first switch unit and the second switch unit are both turned on and the third switch unit is turned off, the battery is charged through the first switch unit and the second switch unit in sequence while the battery supplies power to the load through the first switch unit,
after the third time, the second switch unit is turned off, the third switch unit is turned on, the capacitor charges the resistor through the third switch unit, and after the fourth time, the second switch unit is turned on, and the third switch unit is turned off.
Preferably, the first switching unit includes a first switch connected between an output terminal of the battery and a power supply terminal of the load,
the second switching unit includes a second switch connected between the output terminal of the capacitor and the power supply terminal of the load,
the third switching unit includes a third switch connected between the output terminal of the capacitor and the resistor,
the control unit controls the on-off states of the first switch, the second switch and the third switch.
Preferably, the control unit is a single chip microcomputer control unit.
Preferably, an analog/digital converter is arranged in the singlechip,
the analog-to-digital converter is configured to detect a voltage on the capacitance.
A water meter comprises the current detection device, the battery is a power supply battery of the intelligent water meter, and the load is an electronic module in the water meter.
The invention has the beneficial effects that: the current detection method provided by the invention does not need to use a current sampling resistor, so that the supply current is detected when the load is switched to be in a dormant state by a mode switching control circuit, and the average value of the supply current can be periodically detected in any state (including a working state and a dormant state) of the electronic product by selecting the capacitor with a proper capacitance value and setting the first threshold voltage and the second threshold voltage to represent the power consumption of the electronic product. Because the supply current detected by the current detection method provided by the invention is not limited to the sleep current but is the average supply current of the electronic product at any time interval, the detection current obtained by the current detection method provided by the invention can reflect the whole power consumption of the electronic product, and not only the power consumption in sleep. In addition, the current detection method provided by the invention does not need to limit the detection current in a sleep state, so that mode switching is not needed, and the situation that the load voltage obviously drops to cause power-off reset of the single chip microcomputer in the background technology can be avoided, and the detection stability of the current detection method provided by the invention is good. In addition, the current detection circuit provided by the invention does not need to use a sampling resistor in the periodic detection process of the current, so that the introduced power consumption is less than that of the prior art, and the low-power-consumption performance of an electronic product is favorably improved.
Drawings
Fig. 1 is a schematic flow chart illustrating a current detection method according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a conventional power supply main loop;
FIG. 3 is a schematic diagram of a main circuit of a conventional current detecting device;
fig. 4 is a schematic diagram of a main circuit of a conventional current detection device.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without any creative effort, shall fall within the protection scope of the present invention. It should be noted that "…" in this description of the preferred embodiment is only for technical attributes or features of the present invention.
The basic principle of the current detection method provided by the invention is that the discharge charge quantity of a large-capacity capacitor connected in parallel with the output end of a lithium battery in a certain period is equal to the product of the average discharge current and the discharge time in the period and also equal to the product of the capacitance voltage drop and the capacitance value of the capacitor, namely;
Qdis＝Δt×Iavg＝Δu×C
wherein Q isdisTo discharge the electric quantity,. DELTA.t is the discharge time, IavgAnd is the average current, delta u is the capacitance voltage drop, and C is the capacitance value of the capacitor. Therefore, when the capacitance value of the capacitor is known, the average current during the discharge period can be calculated by detecting the voltage drop before and after the discharge of the capacitor. Specifically, fig. 3 is a schematic flow chart of a current detection method according to an embodiment of the present invention, where the current detection method mainly includes:
step 11: the battery is enabled to supply power to the load and charge a capacitor which is connected with the load in parallel and is arranged at the output end of the battery,
step 12: detecting a voltage on the capacitor during charging of the capacitor,
step 13: recording the moment when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage as a first moment, and acquiring a first voltage on the capacitor at the first moment,
step 14: stopping the battery from supplying power to the load after the first time, wherein the capacitor supplies power to the load,
step 15: recording the moment when the voltage on the capacitor drops to be equal to or less than a set second threshold voltage as a second moment in the process that the capacitor supplies power to the load, and acquiring a second voltage on the capacitor at the second moment,
step 16: and returning to the step 11 after the second moment, and calculating the average supply current of the load from the first moment to the second moment according to the first voltage, the second voltage and the capacitance value of the capacitor.
Specifically, the calculation formula of the average supply current Iavg is as follows:
Iavg＝(UC1-UC2)×C/(T2-T1)
wherein, UC1Is the first voltage, UC2Is the second voltage, C is the capacitance value of the capacitor, T1Is the first time, T2Is the second time.
According to the current detection method provided by the invention, the average power supply current in the discharging process of the capacitor can be periodically detected by selecting the proper capacitor and setting the proper first threshold voltage and second threshold voltage, and the detection is not limited to be only in the load sleep state.
Obviously, the current detection method provided by the invention does not need to use a current sampling resistor, so that the power supply current does not need to be detected when the mode switching control circuit is switched to a state that the load is in a sleep state, and the average value of the power supply current can be periodically detected in any state (including a working state and a sleep state) of the electronic product only by selecting the capacitor with a proper capacitance value and setting the proper first threshold voltage and second threshold voltage so as to represent the power consumption of the electronic product. Because the supply current detected by the current detection method provided by the invention is not limited to the sleep current but is the average supply current of the electronic product at any time interval, the detection current obtained by the current detection method provided by the invention can reflect the whole power consumption of the electronic product, and not only the power consumption in sleep. In addition, the current detection method provided by the invention does not need to limit the detection current in a sleep state, so that mode switching is not needed, and the situation that the load voltage obviously drops to cause power-off reset of the single chip microcomputer in the background technology can be avoided, and the detection stability of the current detection method provided by the invention is good. In addition, the current detection circuit provided by the invention does not need to use a sampling resistor in the periodic detection process of the current, so that the introduced power consumption is less than that of the prior art, and the low-power-consumption performance of an electronic product is favorably improved.
Because a reference value given by the capacitance value C of the capacitor may be different from an actual value, further, the capacitance value of the capacitor is periodically calibrated, during the calibration of the capacitor, the detection of the supply current may be stopped first, after the calibration of the capacitor is completed, the supply current is continuously detected, and the average supply current is calculated according to the calibrated capacitance value of the capacitor. The calibration period of the capacitor is larger than the detection period of the power supply current, namely, one capacitor calibration period comprises a plurality of current detection periods.
Specifically, the step of periodically calibrating the capacitance value of the capacitor includes:
step 21: when the capacitance value of the capacitor needs to be calibrated, the capacitor is charged while the battery supplies power to the load,
step 22: detecting a voltage on the capacitor during charging of the capacitor,
step 23: recording a third moment when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage, and recording a third voltage on the capacitor at the third moment,
step 24: after the third time, the battery is enabled to continuously supply power to the load, the capacitor discharges the resistor,
step 25: recording a fourth time when the voltage on the capacitor drops to be equal to or less than a set fourth threshold voltage in the process that the capacitor discharges the resistor, and recording a fourth voltage on the capacitor at the fourth time,
step 26: and calculating the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage, the fourth voltage and the difference value between the fourth moment and the third moment to serve as the calibrated capacitance value of the capacitor.
The capacitance value C of the capacitor is calculated according to the following formula:
C＝(T2-T1)/R×ln(UC1/UC2)
wherein, in the calculation formula of the capacity value C, T1Is the third time, T2At the fourth moment, R is the resistance value of the resistor, UC1Is said third voltage, UC2Is the fourth voltage.
The invention also provides a detection device for the supply current, which comprises: the device comprises a first switch unit connected between a power supply battery and a load, a capacitor connected with the load in parallel at the output end of the battery, a second switch unit connected with the capacitor in series, and a control unit. The control unit is configured to control the on-off states of the first switch unit and the second switch according to the voltage on the capacitor, acquire a first voltage on the capacitor at a first moment and a second voltage on the capacitor at a second moment, and calculate the average supply current of the load from the first moment to the second moment according to the first voltage, the second voltage and the capacitance value of the capacitor. The first time is the time when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage in the process that the battery charges the capacitor, and the second time is the time when the voltage on the capacitor falls to be equal to or less than a set second threshold voltage in the process that the capacitor supplies power to the load. During the period that the first switch unit and the second switch unit are both switched on, the battery supplies power to the load through the first switch unit and simultaneously sequentially charges the battery through the first switch unit and the second switch unit, after the first moment, the first switch unit is switched off, the capacitor supplies power to the load through the second switch unit, and after the second moment, the first switch unit is switched on.
Specifically, as shown in fig. 4, it is a schematic diagram of a main circuit structure of the current detection apparatus provided in the present invention. The first switching unit includes a first switch S1 connected between an output terminal of the battery BAT and a power supply terminal of the load, and the second switching unit includes a second switch S2 connected between an output terminal of the capacitor C and the power supply terminal of the load. In other embodiments, the first switch unit and the second switch unit may further include a protection circuit unit.
The working process of the current detection device provided by the present invention is specifically described below with reference to fig. 4, which is described as follows:
first, the control unit controls both the switch S1 and the switch S2 to be closed, and at this time, the battery BAT supplies power to the load while charging the capacitor C. Then detecting the voltage U on the capacitor CCWhen the voltage on the capacitor C is equal to or greater than the set first threshold voltage UCMHRecording the time as the first time T1And obtaining T1First voltage U across capacitor C at a timeC1And switch S1 is opened and the load is supplied by capacitor C, where UCMHThe voltage upper threshold is detected for the current, i.e. when the capacitor voltage is below this voltage value, no current detection is performed. Then, during the discharging process of the capacitor C, the voltage on the capacitor C is detected to be equal to or less than the set second threshold voltage UCMLRecording the time as the second time T2And obtaining T2Second voltage U across capacitor C at a timeC2And closes (in the sense of being conductive) the switch S1 to enter the next sensing period. Wherein U isCMLFor current detection of a voltage below a threshold value, i.e. when the capacitor voltage is below this voltage value, the capacitor discharge operation is stopped, and the average current I of said supply current is calculated according to the average current calculation formula mentioned in the methodavg。
The current detection device provided by the invention is also provided with a capacitance calibration unit, and the control unit controls the capacitance calibration unit
The capacitance calibration unit periodically calibrates the capacitance value of the capacitor, and the control unit controls the current detection device to stop detecting the power supply current of the load in the calibration process of the capacitor. And after the capacitance of the capacitor is calibrated, continuously detecting the power supply current, and calculating the average power supply current according to the calibrated capacitance value of the capacitor. When the capacitance value of the capacitor needs to be calibrated. The control unit controls the on-off states of the first switch unit, the second switch unit and the third switch unit according to the voltage on the capacitor, and calculates the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage on the capacitor at the third moment, the fourth voltage on the capacitor at the fourth moment and the difference value between the fourth moment and the third moment to serve as the capacitance value after the capacitor is calibrated.
The third time is the time when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage in the process that the capacitor charges the capacitor, and the fourth time is the time when the voltage on the capacitor falls to be equal to or less than a set fourth threshold voltage in the process that the capacitor discharges the resistor. During the period that the first switch unit and the second switch unit are both switched on and the third switch unit is switched off, the battery supplies power to the load through the first switch unit and charges the battery through the first switch unit and the second switch unit in sequence. After the third time, the second switch unit is turned off, the third switch unit is turned on, the capacitor charges the resistor through the third switch unit, and after the fourth time, the second switch unit is turned on, and the third switch unit is turned off.
Specifically, as shown in fig. 3, the capacitance calibration unit includes a third switching unit and a resistor R, the third switching unit and the resistor R are connected in series between the output terminal of the capacitor and a ground reference terminal, and the third switching unit includes a third switch S3 connected between the output terminal of the capacitor and the resistor. The capacitance calibration unit and the current detection unit share the first switch unit and the second switch unit. The operation of the capacitance calibration unit is described in detail below with reference to fig. 3, which is described as follows:
firstly, the control circuit controls the switches S1, S2 to be closed, the switch S3 to be open, the battery BAT supplies power to the load and simultaneously charges the capacitor C, then the voltage on the capacitor C is detected, and when the voltage on the capacitor C is equal to or greater than a set third threshold voltage UCCHRecording the time as the third time T1And obtaining T1Third voltage U across capacitor C at a timeC1And opening switch S2, closing switch S3, discharging capacitor C to R, where UCCHThe voltage upper threshold is calibrated for the capacitance, i.e. when the capacitance voltage is lower than this voltage value, no capacitance calibration is performed. Then, in the discharging process of the capacitor C, the voltage on the capacitor C is equal to or less than a set fourth threshold voltage UCCLRecord the time as the fourth time T2And obtaining T2Fourth voltage U of capacitor C at timeC2And opening S3, closing S2, and calculating the capacitance value of the capacitor C according to the capacitance value calculation formula in the method.
According to the current detection device provided by the embodiment of the present invention, the control unit is a single chip microcomputer control unit, and further, an analog/digital converter is disposed in the single chip microcomputer, and the analog/digital converter is configured to detect a voltage on the capacitor C.
The current detection device provided by the embodiment of the invention is suitable for current detection of different electronic products, for example, the electronic product comprising the current detection device is a water meter, such as an intelligent water meter, the battery is a power supply battery of the intelligent water meter, and the load is an electronic module in the water meter. The intelligent water meter can periodically detect the load power supply current according to the current detection circuit device and obtain the power consumption performance of the intelligent water meter according to the office power supply current, generally, the higher the detected current value is, the higher the power consumption of the electronic product is, and vice versa.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (10)
1. A current sensing method, comprising:
step 11: the battery is enabled to supply power to the load and charge a capacitor which is connected with the load in parallel and is arranged at the output end of the battery,
step 12: detecting a voltage on the capacitor during charging of the capacitor,
step 13: recording the moment when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage as a first moment, and acquiring a first voltage on the capacitor at the first moment,
step 14: stopping the battery from supplying power to the load after the first time, wherein the capacitor supplies power to the load,
step 15: recording the moment when the voltage on the capacitor drops to be equal to or less than a set second threshold voltage as a second moment in the process that the capacitor supplies power to the load, and acquiring a second voltage on the capacitor at the second moment,
step 16: and returning to the step 11 after the second moment, and calculating the average supply current of the load from the first moment to the second moment according to the first voltage, the second voltage and the capacitance value of the capacitor.
2. The method according to claim 1, further comprising calibrating the capacitance value of the capacitor periodically, stopping detecting the supply current during the calibration of the capacitor, continuing to detect the supply current after the calibration of the capacitor is completed, and calculating the average supply current according to the calibrated capacitance value of the capacitor.
3. The method of claim 2, wherein the step of periodically calibrating the capacitance of the capacitor comprises:
step 21: when the capacitance value of the capacitor needs to be calibrated, the capacitor is charged while the battery supplies power to the load,
step 22: detecting a voltage on the capacitor during charging of the capacitor,
step 23: recording a third moment when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage, and recording a third voltage on the capacitor at the third moment,
step 24: after the third time, the battery is enabled to continuously supply power to the load, the capacitor discharges the resistor,
step 25: recording a fourth time when the voltage on the capacitor drops to be equal to or less than a set fourth threshold voltage in the process that the capacitor discharges the resistor, and recording a fourth voltage on the capacitor at the fourth time,
step 26: and calculating the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage, the fourth voltage and the difference value between the fourth moment and the third moment to serve as the calibrated capacitance value of the capacitor.
4. A current detecting device, comprising:
a first switching unit connected between the power supply battery and the load,
a capacitor connected in parallel with the load at the output of the battery,
a second switching unit connected in series with the capacitor,
a control unit configured to control on-off states of the first switch unit and the second switch according to a voltage on the capacitor, obtain a first voltage on the capacitor at a first time and a second voltage on the capacitor at a second time, and calculate an average supply current of the load from the first time to the second time according to the first voltage, the second voltage, and a capacitance value of the capacitor,
wherein the first time is a time when the voltage on the capacitor rises to be greater than or equal to a set first threshold voltage in the process that the battery charges the capacitor, the second time is a time when the voltage on the capacitor drops to be equal to or less than a set second threshold voltage in the process that the capacitor supplies power to the load,
when the first switch unit and the second switch unit are both on, the battery supplies power to the load through the first switch unit and charges the battery through the first switch unit and the second switch unit in sequence,
after the first moment, the first switch unit is switched off, the capacitor supplies power to the load through the second switch unit, and after the second moment, the first switch unit is switched on.
5. The current detection device according to claim 4, further comprising a capacitance calibration unit, wherein the control unit controls the capacitance calibration unit to periodically calibrate the capacitance value of the capacitor, during the calibration of the capacitor, the control unit controls the current detection device to stop detecting the supply current of the load, after the calibration of the capacitance of the capacitor is completed, the supply current is continuously detected, and the average supply current is calculated according to the calibrated capacitance value of the capacitor.
6. The current detection device according to claim 5, wherein the capacitance calibration unit includes a third switching unit and a resistor, the third switching unit and the resistor being connected in series between the output terminal of the capacitance and a reference ground terminal,
when the capacitance value of the capacitor needs to be calibrated, the control unit controls the on-off states of the first switch unit, the second switch unit and the third switch unit according to the voltage on the capacitor, and calculates the capacitance value of the capacitor according to the resistance value of the resistor, the third voltage on the capacitor at a third moment, the fourth voltage on the capacitor at a fourth moment and the difference value between the fourth moment and the third moment to serve as the calibrated capacitance value of the capacitor,
wherein the third time is a time when the voltage on the capacitor rises to be equal to or greater than a set third threshold voltage in the process of charging the capacitor by the battery, the fourth time is a time when the voltage on the capacitor falls to be equal to or less than a set fourth threshold voltage in the process of discharging the resistor by the capacitor,
when the first switch unit and the second switch unit are both turned on and the third switch unit is turned off, the battery is charged through the first switch unit and the second switch unit in sequence while the battery supplies power to the load through the first switch unit,
after the third time, the second switch unit is turned off, the third switch unit is turned on, the capacitor charges the resistor through the third switch unit, and after the fourth time, the second switch unit is turned on, and the third switch unit is turned off.
7. The current detection device according to claim 6,
the first switching unit includes a first switch connected between an output terminal of the battery and a power supply terminal of the load,
the second switching unit includes a second switch connected between the output terminal of the capacitor and the power supply terminal of the load,
the third switching unit includes a third switch connected between the output terminal of the capacitor and the resistor,
the control unit controls the on-off states of the first switch, the second switch and the third switch.
8. The current sensing device of claim 7, wherein the control unit is a single-chip microcomputer control unit.
9. The current detecting device according to claim 8, wherein an analog/digital converter is provided in the single chip microcomputer,
the analog-to-digital converter is configured to detect a voltage on the capacitance.
10. A water meter comprising the current sensing device of any one of claims 4 to 9, wherein the battery is a power supply battery of the intelligent water meter, and the load is an electronic module in the water meter.
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| CN202010612780.0A CN111721997A (en) | 2020-06-30 | 2020-06-30 | Current detection method, current detection device and water meter |
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| CN202010612780.0A CN111721997A (en) | 2020-06-30 | 2020-06-30 | Current detection method, current detection device and water meter |
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