JP7407380B2 - Power supply impedance estimation and power supply voltage drop detection device - Google Patents

Description

The present invention relates to a power supply impedance estimation and power supply voltage drop detection device for estimating the internal impedance of a power supply unit that drives a circuit such as battery voltage, and detecting a drop in power supply voltage.

Conventionally, a power supply voltage drop detection IC has been used as a method for detecting a drop in the power supply voltage that drives a circuit such as a microcomputer (for example, see Patent Document 1).

In addition, as a method of detecting the internal impedance of the battery, a resistor and a switch are connected in series between the battery and GND, and the SW is turned ON/OFF to measure the battery voltage when ON and the battery voltage when OFF. The internal impedance is estimated by storing the voltage value in the RAM and calculating the voltage difference from the stored RAM value. This method of detecting internal impedance also requires a voltage detection device for detecting battery voltage (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 2009-174975 Japanese Patent Application Publication No. 8-115147

The above power supply voltage drop detection IC and voltage detection device have a stabilized power supply circuit inside the IC or device that outputs a stabilized voltage that is not affected by fluctuations in the power supply voltage, and uses the stabilized voltage as a comparison voltage to determine the power supply voltage. A common configuration is to compare the divided voltage and the comparison voltage using a comparator. That is, there is a problem in that a stabilized power supply circuit that outputs a stabilized voltage is required, and the circuit configuration is complicated.

In order to solve such problems, the power supply impedance estimation and power supply voltage drop detection device according to the present invention includes a power supply unit, a circuit unit driven by the output from the power supply unit, and a circuit unit that outputs the output from the power supply unit for a predetermined period of time. It has a holding section for holding and a determining section, and the determining section detects the difference between the output from the holding section and the output from the power supply section when the operation of the circuit section changes from ON to OFF or from OFF to ON. This is used to estimate power supply impedance and detect a drop in power supply voltage.

The power supply impedance estimation and power supply voltage drop detection device according to the present invention does not require a stabilized voltage as a reference voltage. Therefore, a voltage drop can be detected with a simple configuration.

Block diagram showing the configuration of a power supply impedance estimation and power supply voltage drop detection device in Embodiment 1 Block diagram showing the configuration of a voltage drop detection device in Embodiment 2 Signal diagram input to the determination unit in Embodiment 1 Signal diagram input to the determination unit in Embodiment 2 Diagram illustrating abnormal operation of the stepping motor and bidirectional valve in Embodiment 2

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to this embodiment.

(Embodiment 1)
FIG. 1 is a block diagram showing an example of the configuration of a power supply impedance estimation and power supply voltage drop detection device according to Embodiment 1 of the present invention, and FIG. 3 is a signal diagram input to the determination unit according to Embodiment 1.

[1-1. composition]
The configuration of Embodiment 1 will be described with reference to FIG. 1. The output voltage a of the power supply section 1 is supplied to the gas meter measurement section 2, which is a circuit section, and is also supplied to the holding section 3 and the determination section 4 at the same time. Furthermore, the output voltage b from the holding section 3 is also input to the determining section 4 .

The holding section 3 is composed of a resistor 31 and a capacitor 32. The determination section 4 includes a resistor 41, a resistor 42, and a comparator 43. The power supply unit 1 is composed of a lithium battery.

[1-2. motion]
The operation of the first embodiment of the present invention configured as described above will be explained with reference to FIG. 3. Output voltage a from power supply section 1 is supplied to capacitor 32 via resistor 31. The circuit composed of the resistor 31 and the capacitor 32 is a so-called integrating circuit. In FIG. 3, the vertical axis shows the voltage level, and the horizontal axis shows the passage of time. The solid line indicates the output voltage a of the power supply section 1, and the dotted line indicates the output voltage b from the capacitor 32.

The gas meter measurement unit 2 includes, for example, a wireless communication unit (not shown), and a large current flows during wireless communication. FIG. 3 shows the voltage change when the operation of the wireless communication section as shown above in the gas meter measurement section 2 is turned on at timing (a) and turned off at timing (b), resulting in a large change in current. .

The output voltage b changes slowly due to the action of the capacitor 32. The output voltage a is divided by a resistor 41 and a resistor 42 that constitute the determining section 4, and a voltage d is output. The comparator 43 compares the voltage d and the output voltage b. The voltage levels to be compared are the output voltage a at point A and the output voltage b at point B immediately after timing (b) in FIG. The voltage at point A is the output voltage a of the power supply unit 1 when the wireless communication unit is in the OFF state, and the voltage at point B is the output voltage b of the power supply unit 1 when the wireless communication unit is in the ON state. Indicates the condition.

In the gas meter measurement unit 2, only a very small current flows when the wireless communication unit is OFF, and the output voltage a at point A of the power supply unit 1 is equal to the voltage under no load. The output voltage of the lithium battery constituting the power supply section 1 under no load is approximately constant, for example, 3V, regardless of the battery capacity.

However, the internal impedance of the battery increases as the battery capacity decreases, so when a large current flows, such as when the wireless communication section is ON, the output voltage a and the output voltage b of the battery decrease significantly. The output voltage b at point B maintains the voltage dropped when the wireless communication section is turned on. That is, the difference between the output voltage a at point A and the output voltage b at point B indicates a voltage drop due to the internal impedance of the battery.

According to the above operation, the comparator 43 compares the voltage obtained by dividing the output voltage a and the output voltage b, and when the output voltage b becomes smaller than the divided voltage, it can be determined that the voltage is below a predetermined voltage.

Furthermore, if the load impedance of the wireless communication unit when the operation is ON is Ra, and the internal impedance of the power supply unit 1 is Ro,
Output voltage b at point B/output voltage a at point A=Ra/(Ro+Ra) (1)
The relationship holds true. On the other hand, the criteria for detecting a voltage drop in the comparator 43 are as follows, assuming that the resistances of the resistor 41 and the resistor 42 are R41 and R42, respectively.
Output voltage b at point B/output voltage a at point A=R42/(R41+R42) (2)
It is. Therefore, if the load impedance Ra is known from the above equations (1) and (2), it is possible to estimate the internal impedance Ro of the power supply unit 1 at the time of voltage drop detection.

[1-3. Effects, etc.]
As described above, in the first embodiment, it is possible to detect that the voltage has fallen below a predetermined voltage with a simple configuration without using a stabilizing power supply circuit for voltage measurement, and also to detect the internal impedance of the power supply unit 1. It is possible to estimate the source impedance.

(Embodiment 2)
Embodiment 2 will be described below with reference to FIGS. 2 and 4.

[2-1. composition]
FIG. 2 is a diagram showing the configuration of the second embodiment. Blocks having the same functions as those in the configuration of FIG. 1 are given the same numbers. Description of parts that overlap with the configuration of FIG. 1 will be omitted. The resistor 5, the stepping motor drive unit 6, the stepping motor 7, and the two-way valve 8 are functional blocks that constitute the gas meter measurement unit 2 in FIG.

The two-way valve 8 is for blocking or opening the gas flow rate flowing through the gas meter. The stepping motor 7 is rotated by the drive pulse generated by the stepping motor drive unit 6, and the two-way valve 8 is closed or opened depending on the direction of rotation.

The resistor 5 is for converting the instantaneous current flowing through the stepping motor drive section 6 into a voltage change. The output voltage c, which is the output of the resistor 5, is input to the resistor 31 instead of the output voltage a from the power supply section 1. The determination section 4 includes an analog-to-digital conversion section 44 and a logic section 45.

[2-2. motion]
The operation of the second embodiment of the present invention configured as described above will be explained with reference to FIG. Output voltage a from power supply section 1 is supplied via resistor 5 to capacitor 32 via resistor 31 as output voltage c. The circuit composed of the resistor 31 and the capacitor 32 is a so-called integrating circuit.

In FIG. 4, the vertical axis shows the voltage level, and the horizontal axis shows the passage of time. The solid line indicates the output voltage a of the power supply section 1, and the dotted line indicates the output voltage b from the capacitor 32. When the stepping motor drive unit 6 is turned on, a large current flows through the resistor 5. When the stepping motor drive section 6 is OFF, no current flows through the resistor 5, so the output voltage c and the output voltage a have the same voltage value.

In FIG. 4, the operation of the stepping motor drive unit 6 is turned on at timing (a), the bidirectional valve 8 is fully open or fully closed at timing (c), the rotation of the stepping motor 7 is stopped, and the stepping motor is turned on at timing (b). It shows the voltage change in a state where the operation of the motor drive section 6 is OFF and the current changes greatly. The change in timing (c) indicates that when the stepping motor 7 stops rotating, the load becomes heavier, so the current flowing through the stepping motor drive section 6 increases slightly.

The output voltage c is input to the analog-to-digital converter 44 as an output voltage b whose voltage changes are made gentler due to the action of the capacitor 32. The voltage change in the output voltage a is due to the voltage drop due to the internal impedance Ro of the power supply section 1, and the voltage change in the output voltage b is due to the voltage drop due to the internal impedance Ro of the power supply section 1 as well as the voltage drop due to the resistance value R5 of the resistor 5. is added.

The voltage at point A is the output voltage a of the power supply unit 1 when the stepping motor drive unit 6 is in the OFF state, and the voltage at point B is the output voltage b when the stepping motor drive unit 6 is in the ON state. It shows the condition. If the total load impedance of the stepping motor drive section 6 and the stepping motor 7 is Rb, then in the analog-to-digital converter 44, the output voltage a at point A immediately after timing (b) is set as the reference voltage, and the output voltage a at point A immediately after timing (b) is set as the reference voltage. Since the output voltage b at point B is converted to a digital signal, the digital signal value X of the output voltage b at point B is
X = Output voltage b at point B/Output voltage a at point A = Rb/(Ro+R5+Rb)
Ro=(1/X)×(Rb×(1-X)-X×R5)
It is.

On the other hand, the output voltage b at point D immediately before timing (b) is converted into a digital signal in the analog-to-digital converter 44 using the output voltage a at point C as a reference voltage. The value Y is
Y= Output voltage b at point D/output voltage a at point C=Rb/(R5+Rb)
Rb=R5×Y/(1-Y)
Therefore, from the above two formulas, Ro=(1/X)×R5×(Y-X)/(1-Y)
From the above, since the resistance value R5 of the resistor 5 and the digital signal values X and Y are known, the internal impedance Ro of the power supply unit 1, that is, the power supply impedance can be calculated.

Further, from the value of the digital signal value X, it is possible to know by what ratio the output voltage a of the power supply unit 1 has decreased due to the change from the time when the operation is OFF to the time when the operation is ON.

Next, referring to FIG. 5, the operation when an abnormality occurs in the operation of the stepping motor drive section 6, stepping motor 7, and bidirectional valve 8 will be described. Consider a disconnection of the stepping motor 7 and a sticking of the two-way valve as malfunctions. The stepping motor 7 has a plurality of coils. Here, the stepping motor 7 will be described as having two coils.

FIG. 5 shows a value (output voltage c/output voltage a) corresponding to the voltage drop across the resistor 5. The dotted line shown in FIG. 5 indicates the case where one of the two coils is disconnected. The normal operation indicated by the solid line is when the stepping motor 7 is operating normally. The stuck state shown by the dashed line is a case where the two-way valve is stuck and the stepping motor 7 does not rotate. When the wire is broken, the voltage drop across the resistor 5 becomes small, and when the wire is stuck, the voltage drop across the resistor 5 becomes large.

Therefore, the values of points E, F, and G immediately before timing (c) are obtained, and if the values are larger than the value of point F during normal operation by a predetermined value or more, it is determined that the wire is broken, and if the value is smaller than the predetermined value, it is determined that the wire is stuck. Here, E, F
, the value at point G is a value calculated by (output voltage c/output voltage a), but at points E, F, and G, output voltage c=output voltage b. Therefore, output voltage b/output voltage a is equal to the digital value Z converted by the analog-to-digital converter 44. That is, if the digital values at points E, F, and G are larger than a predetermined value with respect to the digital value Z during normal operation, it can be determined that the wire is broken, and if it is smaller than the predetermined value, it can be determined that the wire is stuck. Furthermore, it can also be determined that there is an abnormality when there is no change in the digital value Z at timing (c).

As explained above, by inserting the resistor 5, the power source impedance can be estimated accurately, and the detection of operational abnormalities such as disconnection or sticking of the stepping motor 7 and the two-way valve 8 can be realized with the same circuit configuration.

[2-3. Effects, etc.]
As described above, in the second embodiment, the power supply impedance of the power supply section 1 can be estimated without using a stabilized power supply circuit for voltage measurement. Therefore, when the power supply unit 1 uses a battery such as a lithium battery, it is possible to issue a battery voltage drop alarm by estimating that the battery capacity is low and the internal impedance of the battery has increased.

Furthermore, by storing the relationship between the internal impedance of the battery and the battery capacity in advance as a table, the remaining battery capacity can be accurately estimated from the estimated internal impedance of the power supply unit 1. Furthermore, detection of operational abnormalities such as disconnection or sticking of the stepping motor 7 and the two-way valve 8 can be realized with the same circuit configuration, contributing to cost reduction.

Note that in the first and second embodiments, voltage values before and after timing (B) are used, but voltage values before and after timing (A) may be used.

Further, in the second embodiment, the output voltage b at the point D is stored in the RAM as a digital value by the analog-to-digital converter 44 as the holding unit 3, and the output voltage b at the point D which was stored instead of the output voltage b at the point B is stored in the RAM. Although it is possible to use the output voltage b, by configuring the holding section 3 to hold the output voltage a in an analog voltage value state, an additional effect is obtained in that a RAM is not required.

Note that the above-described embodiments are for illustrating the technology of the present disclosure, and therefore various changes, substitutions, additions, omissions, etc. can be made within the scope of the claims or equivalents thereof.

INDUSTRIAL APPLICATION This invention is applicable to the voltage drop detection apparatus of the battery which drives the two-way valve built into a gas meter, and a wireless communication device.

1 Power supply section 2 Gas meter measurement section (circuit section)
3 Analog output holding section (holding section)
4 Judgment section 5 Resistance 6 Stepping motor drive section 7 Stepping motor 8 Bidirectional valve 31 Resistance 32 Capacitor 41 Resistance 42 Resistance 43 Comparator 44 Analog-digital conversion section 45 Logic section

Claims (2)

comprising a power supply section, a circuit section driven by an output from the power supply section, a holding section that holds the output from the power supply section for a predetermined period of time, and a determination section;
The determination unit detects a power supply impedance or a drop in power supply voltage using the difference between the output from the holding unit and the output from the power supply unit when the operation of the circuit unit changes from ON to OFF or from OFF to ON. and an analog-to-digital conversion section that converts the output from the holding section into a digital signal using the output from the power supply section as a reference voltage, and the power supply impedance or the power supply corresponding to the magnitude of the digital signal. Detects voltage drop,
The analog-to-digital converter is configured to be used in common with an analog-to-digital converter for determining an abnormality in a stepping motor that drives a bidirectional valve constituting the circuit. 2. The power source impedance estimation and power source voltage drop detection device according to claim 1, wherein the holding section is configured to hold the output from the power source section with a capacitor via a resistor.