JPH1040792A - Relay driver circuit and terminal network controller using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a relay driver even when a high-level voltage is lowered. SOLUTION: When a control portion 5 outputs a high-level voltage to a driver input portion 14, a transistor is turned OFF, and a collector current flows. This collector current flows a transistor 12b, a current mirror circuit is actuated, a current amplifying this collector current flows a transistor 12a, and whereby the transistor 11b is turned ON. The transistor 12a is also turned ON, a current flows a relay 13, and the relay 13 is driven. Therefore, even when a high-level voltage to be output from the control portion 5 by means of a driver control portion 12 is low, operation of the relay driver is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driver circuit for driving a relay, and more particularly to a driver circuit for driving a relay.
The present invention relates to a relay driver circuit used in a terminal network control device that controls communication between a meter and a center terminal by automatic meter reading or the like.

[0002]

2. Description of the Related Art FIG. 4 shows a circuit diagram of a conventional relay driver circuit. In FIG. 4, reference numeral 5 denotes a control unit such as a microcomputer operated by a battery 16 for driving the relay, 13 denotes a relay, 14 denotes a relay driver circuit for driving the relay 13, and 15 denotes power for driving the relay. The supplied capacitor, 16 is a battery.

Next, the operation of a conventional relay driver circuit will be described with reference to FIG. When the control unit 5 outputs a high-level voltage, the transistor 14b turns on. Then, a current flows to the base of the transistor 14a, and the transistor 14a is also turned on to draw current from the capacitor 15 through the relay 13. The current drives the relay.

[0004]

However, in the relay drive section, transistors are connected in multiple stages in order to increase the driver capability for driving the relay. Usually, this is a two-stage connection. In this case, the base-emitter voltages of the two transistors are about 2 V in total, and the relay driver does not operate sufficiently without an input voltage of 2 V or more. Therefore, when the battery voltage decreases, the high-level voltage output from the control unit decreases accordingly. When the high-level voltage becomes 2 V or less, the relay driving unit does not operate sufficiently, so that the relay can be driven. Can not.

Further, when the circuit constant of the relay driver circuit is set so that the relay can be driven by the high level voltage from the control unit even when the battery voltage is low, when the battery voltage is high, the high level voltage of the control unit is adjusted accordingly. As a result, the current consumption of the relay driver circuit increases.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention utilizes a current mirror circuit for a relay driver to reduce a high-level voltage output from a control unit for controlling the relay driver. This also enables the operation of the relay driver. Furthermore, since the current input to the base of the input stage transistor of the relay drive unit is amplified by the current mirror circuit, compared to the case of a single transistor, even if the battery voltage fluctuates, the input to the input stage transistor is increased. Changes in the base current can be reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a battery as a power source, a relay driving unit for driving a relay by driving the current of the battery with a multi-stage connected transistor, and a high level according to the voltage of the battery. A control unit, a driver input unit having a transistor that is turned on / off by the control unit, and a collector current of the transistor of the driver input unit that is turned on by the control unit. And a driver control section for supplying current to the transistor, amplifying the current, flowing from the output transistor of the circuit, and turning on the multi-stage connected input stage transistor of the relay drive section. The relay can be driven even when the high-level voltage output from the control unit that controls the relay drive is 2 V or less. Furthermore, since the current input to the base of the input stage transistor of the relay drive unit is amplified by the current mirror circuit, the current is amplified by a single transistor, so that the variation can be reduced with less variation, and the battery voltage range can be increased. Even if it is wide, the current input to the base of the input stage transistor of the relay drive unit does not change significantly, so that it is possible to reduce the variation of the current consumed by the battery when driving the relay due to the voltage fluctuation.

[0008] Further, the present invention has a capacitor for supplying a current flowing to the input stage transistor of the relay driving section and driving the relay. Since the current consumed by the relay driving unit is supplied from the capacitor, the current drawn from the battery power supply during driving of the relay decreases, and the battery voltage does not drop significantly when driving the relay.

[0009] The terminal network control device may further comprise:
The relay driver circuit described above has a line switch. Since the relay driver circuit can operate even at a low voltage, the terminal network control device can operate at a low voltage.

FIG. 1 is a circuit diagram of a relay driver circuit according to a first embodiment of the present invention. In FIG. 1, reference numeral 5 denotes a control unit which controls the relay driving unit 11 and outputs an output voltage corresponding to the voltage of the battery 16, and 11 drives the relay by driving the current of the battery 16 by the transistors connected in multiple stages. When the transistor of the driver input section 20 is turned on, the relay drive section 12 allows the current from the battery 16 to flow as a collector current and to flow to the input transistor of the current mirror circuit composed of a PNP transistor, thereby outputting the output of the current mirror circuit. A driver control unit for turning on the multi-stage input transistor of the relay drive unit 11 by passing a current from the battery 16 to the transistor as a collector current, and a driver input unit 20 having a transistor that is turned on / off by the control unit 5 is there.

Next, the operation will be described. In FIG. 1, the transistor of the driver input unit 20 is turned on by the high-level voltage output from the control unit 5, and a collector current flows. Then, this collector current also flows to the transistor 12b, and the same amount of current flows from the collector of the transistor 12a by the current mirror circuit formed in the driver control unit 12, and this collector current causes the transistor 11b
Also turns on. As a result, the transistor 11a is also turned on, so that current can flow through the relay 13, and the relay 13 is driven.

FIG. 2 is a circuit diagram of a relay driver circuit according to a second embodiment of the present invention. The difference from the first embodiment is that a capacitor 15 that supplies a current flowing to the input-stage transistor of the relay driving unit 11 and drives the relay is provided. The components having the same reference numerals as those in the first embodiment have the same structure, and the description will be omitted.

In FIG. 2, since the driving power of the relay 13 and the collector current of the transistor 11b are supplied from the capacitor 15, the load on the power supply voltage when driving the relay can be reduced.

(Embodiment 3) FIG. 3 is a block diagram of a terminal network control apparatus according to Embodiment 3 of the present invention. In FIG.
1 is a center terminal installed in a management center for managing automatic meter reading and the like and communicates with a terminal network control device via a telephone line 2, 2 is a telephone line, 3 is a DC resistance and AC impedance as viewed from the telephone line 2. A line termination unit 4 for matching and transmitting / receiving signals modulates transmission data from the control unit 5 and a modem unit for demodulating data received from the line termination unit 3, and 5 controls a terminal network control unit 18. A control unit 6 for controlling communication with the meter 7; a meter 7 for measuring a flow rate of gas and the like and communicating with the center terminal 1 via the terminal network control device 18 for meter reading data and the like; Is a line voltage detecting section for detecting the voltage state of the telephone line 2 to identify the line state to the control section 5; The reciprocity detecting unit 10 for notifying this only by detecting the voltage drop of the battery 16 and informing the control unit 5 of the voltage drop, and 13 connects / disconnects the telephone line 2 and the telephone 17 side. A relay that performs control; 14 is a relay driver circuit that controls the driving of the relay 13; 15 is a relay driving capacitor that supplies power when driving the relay; 16 is a battery; 17 is a telephone; 18 is a terminal network control device; 19 is a line voltage detector 8
, Polarity inverting unit 9, relay driver unit 14, and voltage detecting unit 2
4 is a line interface unit.

Next, the operation will be described. In FIG. 3, when performing the automatic meter reading of the normal meter 7, a no-ringing communication service is used. The terminal network control device 18 is a reciprocal detection unit 9
When the polarity inversion of the telephone line 2 is detected, the control unit 5 is informed of this and the control unit 5 is set in an operating state. When receiving the no ringing call signal (NRS), the modem unit 4 sends an answer signal (ANS) to the telephone line 2. As a result, the center terminal 1 and the terminal network control device 18 enter a communication state. In the communication state, a received signal from the center terminal 1 is demodulated by the modem unit 4 and transmitted to the meter 7 via the meter interface unit 6. Conversely, when the meter 7 transmits a signal, the data signal transmitted via the meter interface unit 6 is modulated by the modem unit 4 and transmitted to the center terminal 1.

Next, when it is desired to communicate with the center terminal 1 from the meter 7, the meter 7 is connected to the meter interface unit 6.
To the control unit 5 via the terminal to perform terminal call communication.
Next, the control unit 5 detects the voltage state of the telephone line 2 by the line voltage detection unit 8 to detect whether or not the telephone 17 connected to the terminal network control unit 18 is currently in use. By controlling the driver circuit 14, the relay 13 is driven by the power of the capacitor 15 to disconnect the telephone line 2 from the telephone 17 side. Then, the telephone line 2 is closed by the line terminating unit 3 and dialing is performed, and thereby communication with the center terminal 1 is performed. After the communication, the relay 13 is driven by controlling the relay driver circuit 14 again to connect the telephone line 2 to the telephone 17 side. When the battery voltage drops, the control unit 5 controls the battery voltage drop detection unit 10 to detect whether the battery voltage has dropped. If the battery voltage has dropped, the battery voltage drop detector 10 notifies the controller 5 of this.

[0017]

As apparent from the above description, the present invention has the following effects.

Since the control unit directly controls the relay driving unit, the problem that the power supply voltage of the relay driver circuit cannot be reduced to a low voltage (for example, 2 V or less) has been raised. Is controlled, the relay can be reliably operated even if the battery voltage decreases and the high-level voltage of the control unit decreases accordingly. Furthermore, since the current input to the base of the input stage transistor of the relay drive unit is amplified by the current mirror circuit, the current can be amplified with less variation than by a single transistor. Therefore, even if the voltage change range of the battery is wide, the current input to the base of the input-stage transistor of the relay drive unit does not change significantly, so that it is possible to reduce the variation in the current consumed by the battery when driving the relay.

Further, since the driving power of the relay and the current consumed by the relay driving section are supplied from the capacitor, the amount of current drawn from the battery during driving of the relay is reduced, and the battery voltage does not drop significantly.

Further, since the relay driver circuit can be operated at a low voltage, the terminal network control device can be operated at a low voltage.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a relay driver circuit according to a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram of a relay driver circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a terminal network control device according to a third embodiment of the present invention;

FIG. 4 is an electric circuit diagram of a conventional relay driver circuit.

[Explanation of symbols]

 Reference Signs List 5 control unit 11 relay drive unit 11b input stage 12 driver control unit 12a output transistor (current mirror circuit) 12b input transistor (current mirror circuit) 13 relay 14 relay driver unit 15 capacitor 16 battery 20 driver input unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiko Yasui 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Yuichi Tateyama 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd.

Claims (3)

[Claims] 1. A battery serving as a power supply, a relay driving unit that drives a relay by driving a current of the battery by a transistor connected in multiple stages, and outputs a high-level voltage according to a voltage of the battery. A control unit for controlling a relay driving unit, a driver input unit having a transistor that is turned on / off by the control unit, and a collector current of the transistor of the driver input unit turned on by the control unit, the current being supplied to a current mirror circuit. And a driver control unit for supplying a current to the input transistor, amplifying the current, flowing from the output transistor of the circuit, and turning on a multi-stage input stage transistor of the relay drive unit. 2. The relay driver circuit according to claim 1, further comprising a capacitor that supplies a current flowing through an input-stage transistor of the relay driving section and drives the relay. 3. A terminal network control device using the relay driver circuit according to claim 1 as a line switch.