JPH1042066A - Voltage detecting circuit and terminal network controller using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage detecting circuit by which a voltage is detected with high precision and battery power is saved unless voltage is detected by providing a switch part which on/off controls current permitted to flow in a voltage dividing part for dividing the voltage to be detected and also where voltage lowering is fixed. SOLUTION: When the voltage lowering of a battery 2 is detected, a control terminal is controlled, a transistor(TRS) 5a is turned on, the switch part 5 is operated and a constant voltage generated in the collector of TRS5a is given to the low voltage side of the resistor 7b of the voltage dividing part 7. The voltage divided by the resistors 7a and 7b is compared with the reference voltage of a comparison voltage generating part 4 by a voltage comparing part 3 and a comparison result is outputted to an output terminal. For a period when the voltage lowering of the battery 2 is not required to be detected, the control terminal is controlled, TRS5a is turned off, the switch part 5 is stopped, TRS5d is turned off and the current of the battery 2 is prevented from flowing in the voltage dividing part 7. Thus, the voltage lowering of the battery 2 is detected with high precision and current consumption is saved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage detection circuit mainly for detecting a voltage drop or a voltage increase, and more particularly to a voltage detection circuit used in a terminal network control device connected to an analog line and a terminal network using the same. The present invention relates to a control device.

[0002]

2. Description of the Related Art FIG. 6 shows a circuit diagram of a conventional voltage detection circuit. Note that the prior art describes a case where a voltage detection circuit is used for detecting a decrease in battery voltage.

In FIG. 6, reference numeral 2 denotes a battery, 3 denotes a voltage comparing unit for comparing the battery voltage divided by the voltage dividing unit 7 with the voltage supplied from the comparison voltage detecting unit 4, and 4 denotes a voltage comparing unit 3. A comparison voltage generation unit that supplies a constant voltage, 7 is a voltage division unit that divides the voltage of the battery 2, and 12 is a voltage detection switch unit that controls on / off of the current flowing through the voltage division unit 7.

Next, the operation of the conventional voltage detecting circuit will be described with reference to FIG. In FIG. 6, when it is desired to detect a voltage drop of the battery 2, the control terminal is controlled to first turn on the transistor of the voltage detection unit 12. Then, a current flows through the voltage divider 7 and the voltage of the battery 2 is divided and input to the voltage comparator 3. This is referred to as the voltage comparator 3
Compares the voltage supplied by the comparison voltage generator 4 with an output terminal.

[0005]

However, when the battery voltage is detected, when the battery voltage is used to generate a reference voltage to which the voltage is compared, DC-D
Unless the voltage is increased by a C converter or the like, a reference voltage higher than the battery voltage cannot be generated. Therefore, the voltage to be detected may be divided as described in the related art. However, in this case, a current always flows through a resistor configured to divide the voltage. For this reason, when not detecting the battery voltage drop, a transistor switch is provided to save battery power. Had become.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an on / off control of a current flowing through a voltage dividing section for dividing a voltage to be detected, and a switch section which has a constant voltage drop when on. With this configuration, it is possible to eliminate a shift in a detection threshold value due to a variation in collector-emitter voltage in a transistor manufacturing process, and to perform voltage detection with high accuracy.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a voltage dividing section for dividing a detected voltage, a voltage comparing section for comparing the detected voltage divided by the voltage dividing section with a reference voltage, and the voltage comparing section. And a switch unit that controls on / off of a current flowing through the voltage dividing unit and has a constant voltage drop when on.

According to this structure, the current flowing through the voltage dividing section is controlled on / off by the switch section, and the voltage drop is kept constant when the current is turned on. At the time of OFF, the detection current does not flow and no useless detection current is consumed.

The switch outputs a constant voltage via a buffer circuit and controls on / off of a current flowing through the voltage divider.

According to this configuration, since the switch section is configured using the buffer circuit, the circuit can be easily configured and the circuit can be downsized.

Further, the comparison voltage generator has a feature that it comprises a common voltage generator for supplying a constant voltage to each of the voltage comparator and the switch.

According to this configuration, the difference between the comparison reference voltage of the voltage comparison unit and the voltage output from the switch unit has substantially the same tendency, so that it is possible to reduce the influence of the reference voltage variation on the detection voltage. Become.

In addition, an overvoltage prevention unit for preventing an overvoltage from being applied to the input of the voltage comparison unit is provided. Even if an overvoltage is applied to the input of the voltage comparison unit by the overvoltage prevention unit, the voltage comparison unit is provided. Can be prevented from being destroyed.

Further, there is provided a terminal network control device using the voltage detection circuit for detecting a voltage drop of a battery as a power supply.

In general, in order to extend the life of the terminal network control device, it is necessary to consume a considerable amount of battery capacity, so that the depth of discharge of the battery is increased. You have to work. However, if the thresholds are set higher by that amount so that the circuits operate even if the thresholds vary on the low voltage side, then if the thresholds fluctuate on the high voltage side, the battery voltage will still operate sufficiently. Even if the voltage can be controlled, the battery voltage drop is detected, thereby shortening the life of the terminal network control device. Therefore, it is necessary to reduce the variation in the threshold value for detecting the battery voltage drop. Therefore, by incorporating the present voltage detection circuit in the terminal network control device, the detection of the battery voltage drop can be detected with high accuracy, and the terminal network control device can have a long life.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 (a) is a block diagram showing a configuration in which a switch section in Embodiment 1 of the present invention is configured on the ground side. FIG. 1B is a block diagram showing a configuration in which the switch section according to the first embodiment of the present invention is configured on the detected voltage side.

In FIG. 1A, reference numeral 1 denotes a voltage detection circuit,
Reference numeral 2 denotes a battery, 3 denotes a voltage comparison unit that compares the battery voltage divided by the voltage division unit 7 with the voltage supplied from the comparison voltage generation unit 4, and 4 denotes a comparison voltage generation unit that supplies a voltage to the voltage comparison unit 3 Reference numeral 5 denotes a switch for controlling the voltage of the voltage divider 7 while keeping the voltage on the low voltage side of the voltage divider 7 constant. Reference numeral 7 denotes a voltage divider for dividing the voltage of the battery 2.

Next, the operation will be described. In FIG. 1, when detecting a drop in the voltage of the battery 2, the switch unit 5 is turned on by the control terminal. Then, the switch unit 5 applies a constant voltage to the low voltage side of the resistor 7b. At this time, the voltage input to the voltage comparison unit 3 is as follows.

[0019]

(Equation 1)

This is compared with the voltage of the comparison voltage generator 4 by the voltage comparator 3 and the result of this comparison is output to the output terminal.
When the control terminal is turned off, the switch unit 5 does not operate, and the current of the battery 2 stops flowing through the voltage dividing unit 7.
In this embodiment, the voltage detection circuit is used for detecting a drop in the battery voltage. However, the voltage detection circuit can be used for detecting other voltages such as a line voltage, and the same effect can be obtained.
A similar drop can be obtained even if the switch section is configured on the detected voltage side as shown in FIG.

(Embodiment 2) FIG. 2 is a circuit diagram of a voltage detection circuit according to Embodiment 2 of the present invention.

The difference from the first embodiment is that the switch unit 5 outputs a constant voltage via a buffer. The components having the same reference numerals as those in the first embodiment have the same structure, and the description will be omitted.

Next, the operation will be described. In FIG. 2, when a voltage drop of the battery 2 is detected, the transistor 5a is turned on by the control terminal. Then, the switch section 5 operates to apply a constant voltage to the low voltage side of the resistor 7b. This is compared with the voltage of the comparison voltage generation unit 4 by the voltage comparison unit 3 and the comparison result is output to the output terminal. When the control terminal is turned off, the switch section 5 does not operate and the transistor 5d is turned off, so that the current of the battery 2 stops flowing through the voltage dividing section 7.

In this embodiment, the voltage detecting circuit is used for detecting a drop in the battery voltage. However, the voltage detecting circuit can be used for detecting other voltages such as a line voltage, and the same effect can be obtained.

(Embodiment 3) FIG. 3 is a circuit diagram of a voltage detection circuit according to Embodiment 3 of the present invention.

The difference from the second embodiment is that the comparison voltage generator is a common voltage generator for supplying a constant voltage to the voltage comparator 3 and the switch 5. The components having the same reference numerals as those of the second embodiment have the same structure, and the description is omitted.

In FIG. 3, since the voltage to be compared by the voltage comparison unit 3 and the voltage input to the switch unit 5 are both supplied from the common voltage generation unit 8, the influence on the detection voltage due to the voltage variation of the common voltage generation unit 8 is shown. Is as follows.

[0028]

(Equation 2)

Therefore, it is possible to reduce the influence on the detection voltage due to the voltage variation of the common voltage generator 8.

(Embodiment 4) FIG. 4 is a circuit diagram of a voltage detection circuit according to Embodiment 4 of the present invention.

The difference from the second embodiment is that an overvoltage prevention unit 9 for preventing an overvoltage from being applied to the input of the voltage comparison unit 3 is provided. The components having the same reference numerals as those of the second embodiment have the same structure, and the description is omitted.

In FIG. 4, even when an overvoltage is applied to the voltage comparing section 3, the overvoltage preventing section 9 causes the overvoltage to flow through the Zener diode to the ground. Not entered.

(Embodiment 5) FIG. 5 is a block diagram of a terminal network control apparatus according to Embodiment 5 of the present invention.

In FIG. 5, reference numeral 1 denotes a voltage detection circuit for detecting a voltage drop of the battery 2 and notifying the microcomputer unit 19 of the voltage drop, 2 a battery, 6 a relay driving capacitor for supplying electric power for driving the relay, 10 is a telephone line, 11
Is a relay for controlling connection / disconnection between the telephone line 10 and the telephone 14 side, 13 is a terminal network control device, 14 is a telephone, 15 is a voltage detection circuit 1, a pole detection unit 22, a relay driver unit 23 and a line voltage. A line interface unit comprising a detection unit 24, a center terminal 16 installed in a management center for managing automatic meter reading and the like and communicating with the terminal network control device 13 via the telephone line 10, and a telephone terminal 10
A line terminating section 18 for matching the DC resistance and AC impedance viewed from the viewpoint and transmitting and receiving signals, 18 is a modem section for modulating transmission data from the microcomputer section 19 and demodulating data received from the line terminating section 17; Is a microcomputer unit for controlling the terminal network control device 13, 20 is a meter interface unit for controlling communication with the meter 21,
Reference numeral 21 denotes a terminal network controller 1 for measuring the flow rate of gas and the like.
A meter for communicating the meter reading data with the center terminal 16 via the interface 3; a polarity detecting unit 22 for detecting the reversal of the polarity of the telephone line 10; A relay driver unit 24 for controlling the drive of the telephone line 24 is a line voltage detecting unit for detecting the voltage of the telephone line 10 to identify the line state to the microcomputer unit 19.

Next, the operation will be described. In FIG. 5, the normal meter reading of the meter 21 is performed using a no-ringing communication service. When the polarity reversal detection unit 22 detects the reversal of the polarity of the telephone line 10, the terminal network control unit 13 notifies the microcomputer unit 19 of the inversion, and the microcomputer unit 19 enters an operating state. Upon receiving the no ringing call signal (NRS), the modem section 18 sends an answer signal (ANS) to the telephone line 10. Thus, the center terminal 16 and the terminal network control device 13 enter a communication state. In the communication state, a received signal from the center terminal 16 is demodulated by the modem section 18 and transmitted to the meter 21 via the meter interface section 20. Conversely, when the meter 21 transmits a signal, the data signal transmitted via the meter interface unit 20 is modulated by the modem unit 18 and transmitted to the center terminal 16.

Next, when it is desired to communicate with the center terminal 16 from the meter 21, the meter 21 notifies the microcomputer unit 19 via the meter interface unit 20 of the terminal call communication. Next, the microcomputer unit 19 includes the line voltage detection unit 2.
4 to detect whether the telephone 14 connected to the terminal network control device 13 is currently in use by detecting the voltage state of the telephone line 10 and, if not, to control the relay driver 23 to drive the relay. The relay 11 is driven by the power of the capacitor 6 to disconnect the telephone line 10 from the telephone 14. Then, the telephone line 10 is closed by the line terminating unit 17 and dialing is performed, and thereby communication with the center terminal 16 is performed. After the communication, the relay driver 23 is controlled again to control the relay 11.
To connect the telephone line 10 and the telephone 14 side. When the voltage of the battery 2 drops, the microcomputer 19 causes the voltage detection circuit 1
Is detected by controlling. If the voltage has decreased, the voltage detection circuit 1 notifies the microcomputer unit 19 of the decrease.

[0037]

As described above, according to the present invention, when the switch is turned on, the voltage drop of the switch can be kept constant, so that the voltage can be detected with high accuracy.

Further, since the switch section is formed using the buffer circuit, the circuit can be easily formed and the circuit can be downsized.

Further, by supplying a constant voltage to each of the voltage comparison unit and the switch unit from the same constant voltage source, the difference between the comparison reference voltage of the voltage comparison unit and the voltage output from the switch unit tends to be the same, and the reference voltage It is possible to reduce the influence of the variation on the detection voltage.

Further, even if an overvoltage is applied to the input of the voltage comparison unit by the overvoltage prevention unit, the voltage comparison unit can be prevented from being destroyed.

Further, in order to extend the life of the terminal network control device, it is necessary to consume a considerable amount of battery capacity, so that the depth of discharge of the battery becomes large. You have to work. However, if the thresholds are set higher by that amount so that the circuits operate even if the thresholds vary on the low voltage side, then if the thresholds fluctuate on the high voltage side, the battery voltage will still operate sufficiently. Even if the voltage can be controlled, the battery voltage drop is detected, thereby shortening the life of the terminal network control device. Therefore, it is necessary to reduce the variation in the threshold value for detecting the battery voltage drop. Therefore, by incorporating the present voltage detection circuit in the terminal network control device, the detection of the battery voltage drop can be detected with high accuracy, and the terminal network control device can have a long life.

[Brief description of the drawings]

FIG. 1A is a block diagram illustrating a switch unit according to a first embodiment of the present invention on a ground side. FIG. 1B is a block diagram illustrating a switch unit according to a first embodiment of the present invention on a detected voltage side.

FIG. 2 is a circuit diagram of a voltage detection circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a voltage detection circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a voltage detection circuit according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a terminal network control device according to a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional voltage detection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage detection circuit 2 Battery 3 Voltage comparison part 4 Comparison voltage generation part 5 Switch part 6 Relay drive capacitor 7 Voltage division part 8 Common voltage generation part 9 Overvoltage prevention part 10 Telephone line 11 Relay 12 Voltage detection switch part 13 Terminal network control Device 14 Telephone 15 Line interface section 16 Center terminal 17 Line termination section 18 Modem section 19 Microcomputer section 20 Meter interface section 21 Meter 22 Polarity detection section 23 Relay driver section 24 Line voltage detection section

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiko Yasui 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Yuichi Tateyama 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] A voltage dividing section for dividing a detected voltage; a voltage comparing section for comparing the detected voltage divided by the voltage dividing section with a reference voltage; and supplying a reference voltage to the voltage comparing section. A voltage detection circuit comprising: a comparison voltage generation unit; and a switch unit that controls on / off of a current flowing through the voltage division unit and has a constant voltage drop when on. 2. The voltage detection circuit according to claim 1, wherein the switch outputs a constant voltage via a buffer circuit and controls on / off of a current flowing through the voltage divider. 3. The voltage detection circuit according to claim 2, wherein the comparison voltage generator comprises a common voltage generator for supplying a constant voltage to each of the voltage comparator and the switch. 4. The voltage detection circuit according to claim 1, further comprising an overvoltage prevention unit for preventing an overvoltage from being applied to an input of the voltage comparison unit. 5. A terminal network control device using the voltage detection circuit according to claim 1 for detecting a voltage drop of a battery as a power supply.