JPH08163238A - Ringing signal generating circuit - Google Patents

Abstract

PURPOSE: To miniaturize the ringing signal generating circuit and a telephone set, to reduce cost and to reduce power consumption. CONSTITUTION: This circuit is provided with an inductor 1, reference oscillation circuit 6 for generating a signal in a ringing period, oscillation circuit 3 for generating a high frequency signal, switching circuit 2 for performing switching control to the inductor 1 through an intermittent pulse with the high frequency signal modulated with a fundamental frequency signal, and smoothing circuit 4 for smoothing the inverse electromotive force of the inductor 1 by switching, and further equipped with a grounding control circuit 5 for grounding the output of the smoothing circuit 4 by the fundamental frequency signal, modulation circuits AG and IG for calculating AND between the inverted signal of the fundamental frequency signal and the high frequency signal, high resistor 7 for discharging, oscillation stop circuit 11 for stopping the fundamental oscillation circuit 6 after the lapse of several tens of ms ofter the stop of the oscillation circuit 3, offhook detecting circuit 10 for detecting an offhook state, and ringing stop circuit 12 for stopping the generation of a ringing signal at the time of offhook state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ringing technique for a general telephone or a telephone attached to a facsimile, and more particularly to a ringing signal generation circuit suitable for downsizing, cost reduction and power saving of the telephone. Is.

[0002]

2. Description of the Related Art Conventionally, technologies relating to ringing signal generation circuits for downsizing telephones and reducing power consumption include, for example,
JP 61-10352 A, JP 61-2471 A
53 and JP-A-62-114362. In these technologies, a high-frequency transformer that can be downsized to some extent is used as a transformer for DC voltage conversion, and the current supplied to the primary side of this high-frequency transformer is intermittently stepped up at high frequencies to boost the current. The rectified output is obtained and the rectified output is switched at the fundamental frequency to form a ringing signal.

However, in these conventional ringing signal generating circuits, a transformer is used, which is relatively large and costly, and further downsizing and cost reduction of the circuit cannot be achieved. In addition, a transformer has a large energy loss in the transformer and is inefficient.

[0004]

The problem to be solved is that the conventional technique uses a transformer which is relatively large and costly. An object of the present invention is to provide a ringing signal generation circuit which solves the problems of the conventional techniques and enables circuit size reduction, cost reduction, and power consumption reduction.

[0005]

In order to achieve the above object, the ringing signal generating circuit of the present invention is (1) a ringing signal generating circuit for generating a ringing signal for ringing a telephone 9 at a basic frequency, An inductor 1 that stores energy by a current, a basic oscillation circuit 6 that generates a signal of a fundamental frequency, an oscillation circuit 3 that generates a high frequency signal, and a current flowing through the inductor 1 is switched based on the high frequency signal from the oscillation circuit 3. Switching circuit 2 to control
And a smoothing circuit 4 for smoothing the counter electromotive force of the inductor 1 generated by the switching control of the switching circuit 2, and the output of the smoothing circuit 4 based on the basic frequency signal from the basic oscillation circuit 6 at the cycle of the basic frequency. A grounding control circuit 5 for grounding is provided. Also, (2)
In the ringing signal generation circuit described in (1) above, a modulation circuit (AG, IG) that performs a logical product operation of the inverted signal of the basic frequency signal and the high frequency signal is provided, and based on the logical product operation result by the modulated circuit, The switching control of the switching circuit 2 is performed, and the switching operation of the switching circuit 2 and the grounding operation of the grounding control circuit 5 are shifted by a half cycle with respect to the fundamental frequency. Also,
(3) In the ringing signal generation circuit according to any one of (1) and (2) above, a load (high resistance 7) is provided on the output side of the smoothing circuit 4, and when the ground control circuit 5 is not grounded, The output of the smoothing circuit 4 is grounded via the high resistance 7. Also, (4) above (1) to (3)
In the ringing signal generation circuit according to any one of 1 to 3, the smoothing capacitor (C1) in the smoothing circuit 4 is discharged by stopping the operation of the oscillation circuit 3 and grounding the output of the smoothing circuit 4 by the grounding control circuit 5. An oscillation stop circuit 11 for stopping the operation of the basic oscillation circuit 6 is provided later.
(5) In the ringing signal generation circuit according to any one of (1) to (4) above, an off-hook detection circuit 10 for detecting the off-hook state of the telephone 9 and an off-hook state of the telephone by the off-hook detection circuit 10 are detected. Ring stop circuit 12 for stopping the generation of the ring signal based on the detection result
And are provided.

[0006]

In the present invention, (i) the direct current flowing through the inductor is switching-controlled at the switching frequency of the high frequency signal to generate the counter electromotive force of the inductor, the counter electromotive force is smoothed, and the output thereof is output. A ringing signal is generated by grounding at a cycle of the fundamental frequency. In this way, the inductor is used instead of the transformer, so that the circuit can be made small in size and low in cost, and the loss in the circuit can be suppressed to only the loss of the element. Further, (ii) the intermittent pulse in which the switching frequency is modulated by the fundamental frequency is shifted by a half cycle with respect to the fundamental frequency, and the current flowing through the inductor is controlled by this pulse. As a result, it is possible to prevent the current from flowing from the inductor to the smoothing circuit while the ringing signal is off, that is, when the smoothing circuit output is in the grounded state, and it is possible to avoid waste of power consumption. Also,
(Iii) A high resistance (load) is provided on the output side of the smoothing circuit, and the output of the smoothing circuit is grounded via this high resistance even when the grounding control circuit is not grounded. This makes it possible to deal with the safety problem that the smoothing capacitor in the smoothing circuit or the ringing capacitor in the telephone remains charged to a high voltage when the ringing signal generation circuit is stopped. Even when the ringing signal generation circuit operates, it is possible to prevent the ringing signal from rising to an abnormally high voltage. Further, (iv) the basic oscillation circuit is stopped, for example, after several tens of seconds after the operation of the oscillation circuit is stopped. That is, after discharging the smoothing capacitor in the smoothing circuit and the ringing capacitor in the telephone through the grounding control circuit, the basic oscillation circuit that controls the grounding operation of the grounding control circuit is stopped. This makes it possible to deal with the same safety problem as (iii) above. (V) The off-hook state of the telephone is detected, and when the telephone is off-hook, the ringing signal generation is stopped. As a result, it is possible to avoid unnecessary power consumption in the off-hook state.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the configuration of the ringing signal generation circuit of the present invention according to the present invention. In the figure, 1 is an inductor that stores energy by a direct current (+ 24v), 2 is a switching circuit that controls switching of the current flowing through the inductor 1, and 3 is a high frequency signal that is used for controlling the switching operation of the switching circuit 2. Oscillation circuit, 4 is a smoothing circuit that smoothes the back electromotive force of the inductor 1, 5 is a grounding control circuit that grounds the output of the smoothing circuit 4 (described as a discharging circuit in the figure), and 6 is operation control of the grounding control circuit 5. , A basic oscillation circuit that outputs a basic frequency that is a ringing cycle, 7 is a high resistance as a load that grounds the output of the smoothing circuit 4, 8 is a communication line, 9 is a telephone (indicated as an auxiliary telephone in the figure), 10 Is an off-hook detection circuit for detecting the off-hook state of the telephone 9, 11 is an oscillation stop circuit for stopping the oscillation circuit 3 and the basic oscillation circuit 6,
Reference numeral 12 is a ringing stop circuit that stops the ringing signal generation based on the detection result of the off-hook state of the telephone 9 by the off-hook detection circuit 10.

FIG. 2 is an explanatory diagram showing the timing of signal on / off operation in each circuit of FIG. Figure 2 (a)
1 is a signal at (a) of FIG. 1, that is, a signal at the input end of the discharge transistor DTR of the ground control circuit 5, which is sent from the basic oscillation circuit 6 of FIG. FIG. 2B is a signal at the input terminal of the switching transistor STR of the switching circuit 2 of FIG. 1B, that is, the signal of the oscillation circuit 3 of FIG. Is coming. FIG. 2C shows a signal in FIG. 1C, which is an output from the ringing signal generation circuit of this embodiment, that is, a ringing signal used for ringing the telephone 9.

The operation of the ringing signal generating circuit of this embodiment will be described below with reference to FIG. The equivalent circuit of the telephone 9 when it is on-hook can be simply represented by CR (capacitor + resistance) as shown by the solid line in the figure. Then, the ringing capacitor is charged and discharged with an AC signal of 16 Hz to ring the ringer. Therefore, charging and discharging must be performed properly. Therefore, in this example, as shown in FIG. 2B, a signal for intermittently switching at 20 kHz at 16 Hz is used based on the signals from the oscillation circuit 3 and the basic oscillation circuit 6. That is, the oscillation circuit 3 is connected to the switching circuit 2 and turns on / off the switching transistor STR of the switching circuit 2 at 20 kHz. When the switching transistor STR is turned on, a current flows from the DC power supply (+ 24V) to the inductor 1 while linearly increasing. At this time, since both lines are short-circuited by the switching transistor STR, no current flows on the output side and energy is stored in the inductor 1.

Next, when the switching transistor STR is turned off, a counter electromotive force is generated in the inductor 1 and a current flows through the diode DI of the smoothing circuit 4 to the output side,
The smoothing capacitor C1 and the ringing capacitor C2 in the telephone 9 are charged. When switching at 20 kHz is repeated several times, the smoothing capacitor C1 and the ringing capacitor C2 are finally charged to the voltage generated by the counter electromotive force, and as shown in FIG.
0v). In order to ring the telephone 9, the ringing capacitor C1 must be discharged. Therefore, at the same time as switching of 20 kHz is stopped, the discharge transistor DTR of the ground control circuit 5 is turned on to form a discharge loop. By turning on the discharge transistor DTR,
The charges of the smoothing capacitor C1 and the ringing capacitor C2 are gradually discharged from 180V to 24V as shown in FIG. 2C, and one cycle is completed. By repeating this operation, the ringing signal shown in FIG. 2C can be generated.

Here, while the discharge transistor DTR of the ground control circuit 5 is on, that is, when the smoothing capacitor C1 and the ringing capacitor C2 are discharged by the ground control circuit 5, the switching transistor STR of the switching circuit 2 is discharged.
When the switching operation is performed, current flows to the output side of the inductor 1 even though the output side of the inductor 1 is in a discharged state, resulting in wasteful power consumption. Therefore, the AND circuit AG and the inverter circuit I are provided in the switching circuit 2.
G is provided, the output signal of the basic oscillation circuit 6 is inverted by this inverter circuit IG, and the inverted basic frequency signal (16
Hz) and the high frequency signal (20 kHz) from the oscillation circuit 3 are ANDed in the AND circuit AG, and the operation of the switching transistor STR is controlled by the result. That is,
The discharge transistor DTR of the ground control circuit 5 is turned on / off by the signal (16 Hz) shown in FIG.
The switching operation of the switching circuit 2 is controlled by the signal (20 kHz + 16 Hz) shown in (b). As a result,
At the same time that the discharge transistor DTR of the ground control circuit 5 is turned on, the switching operation of the switching circuit 2 is stopped. By doing so, it is possible to prevent a current from flowing to the output side of the inductor 1 when the smoothing capacitor C1 and the ringing capacitor C2 are discharged by the grounding control circuit 5, and wasteful power consumption. It can be avoided.

Next, while the grounding control circuit 5 is off, that is, when the smoothing capacitor C1 and the ringing capacitor C2 are being charged, the ringing signal generating circuit of this embodiment stops and operates, respectively. Think First, when the ringing signal generation circuit is stopped, the smoothing capacitor C1 and the ringing capacitor C2 are still charged, so the output side is
It is dangerous because the high voltage will be applied forever.
Therefore, in this embodiment, a high resistance 7 (several k to several hundred k ohm) is connected to the output side of the inductor 1 to form a discharge loop. In this way, by providing the high resistance 7, even when the ringing signal generation circuit is stopped while the grounding control circuit 5 is off as described above, the charges charged in the smoothing capacitor C1 and the ringing capacitor C2 are discharged. It does not have to remain at a high voltage. On the contrary, by providing the high resistance 7 even when the ringing signal generation circuit operates,
After the smoothing capacitor C1 and the ringing capacitor C2 are charged, there is a loop through which current flows to the output side of the inductor 1, so that the ringing signal can be prevented from rising to an abnormally high voltage.

If the ringing signal generating circuit is stopped while the smoothing capacitor C1 and ringing capacitor C2 are being charged,
Such a problem can also be solved by providing the oscillation stopping circuit 11 and controlling the operations of the oscillation circuit 3 and the basic oscillation circuit 6 as described below. That is, when stopping the ringing signal generation circuit on the way, the oscillation stop circuit 11
First, the oscillation circuit 3 is stopped, and then the basic oscillation circuit 6 is stopped several tens of ms after the oscillation circuit 3 is stopped. By doing so, the ground control circuit 5 can make
The electric charges charged in the smoothing capacitor C1 and the ringing capacitor C2 can be discharged.

In order to prevent the ringing signal from being generated even when the telephone 9 is off-hook, the off-hook detection circuit 10 and the ringing stop circuit 12 are provided in this embodiment. That is, when the telephone 9 is off-hook, as shown by the broken line in the figure, the telephone 9 is simply connected by a resistor, and a current flows from the ringing signal generation circuit through the resistor. The off-hook detection transistor OT of the off-hook detection circuit 10
A current flows through the base of R, and the off-hook detection transistor OTR turns on. As a result, the DC power supply (+ 5v) connected to the collector of the off-hook detection transistor OTR
Current flows toward the ground on the emitter side of the off-hook detection transistor OTR, and the detection signal drops to Low. When the ringing stop circuit 12 detects this detection signal (Low), the ringing stop circuit 12 stops the oscillation operation of the oscillation circuit 3 and the basic oscillation circuit 6 via the oscillation stop circuit 11, and stops the ringing signal generation. The operation when terminating the generation of such a ringing signal will be described below with reference to FIG.

FIG. 3 is a flow chart showing an example of the operation of the ringing signal generation circuit in FIG. 1 at the end of ringing signal generation. Since the equivalent circuit of the telephone 9 of FIG. 1 when it is off-hook can be simply represented by a resistor as shown in FIG. 1, the charges charged in the smoothing capacitor C1 and the ringing capacitor C2 of FIG. 1 are discharged through this resistor. Therefore, when the off-hook of the telephone 9 in FIG. 1 is detected (step 301), the operation of the ringing signal generation circuit of the present embodiment is stopped (step 302), and the process is ended. On the other hand, if off-hook is not detected, it is determined whether or not to stop the generation of the ringing signal (step 303). To stop, first stop the oscillation circuit 3 of FIG. 1 (step 304),
Next, after several tens of ms after stopping the oscillation circuit 3, the basic oscillation circuit 6 of FIG. 1 is stopped (step 305). By doing so, the ground control circuit 5 of FIG.
Therefore, the smoothing capacitor C1 and the ringing capacitor C of FIG.
The electric charge charged to 2 can be discharged.

As described above with reference to FIGS. 1 to 3, in the ringing signal generating circuit of this embodiment, the inductor is used in place of the conventionally used transformer, so that the circuit is small and the cost is low. In addition to being configured, wasteful power consumption can be suppressed to a low level. In addition, the smoothing capacitor and the ringing capacitor can be surely discharged by providing a high resistance and appropriately controlling the charging operation and the discharging operation of the smoothing capacitor and the ringing capacitor, and when the ringing signal generation circuit stops, the smoothing circuit It is possible to solve the safety problem that the smoothing capacitor inside and the ringing capacitor inside the telephone remain charged to high voltage. Further, when the telephone is off-hook, it is possible to stop the generation of the ringing signal without fail, and avoid unnecessary power consumption in the off-hook state.

The present invention is not limited to the embodiments described with reference to FIGS. 1 to 3, and various modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, in order to stop the generation of the ringing signal when the telephone is off-hook, the ringing stop circuit 12 and the oscillation stop circuit 11 are used to oscillate the circuit 3 and the basic oscillator circuit 6.
However, the oscillation stop circuit 12 may directly stop the oscillation operation of the oscillation circuit 3 and the basic oscillation circuit 6.

[0018]

According to the present invention, a transformer is not required, the ringing signal generating circuit and the telephone can be downsized, the cost can be reduced, and the power loss can be reduced. Further, the ringing signal can be effectively turned off. Power consumption can be reduced, and power consumption can be reduced. Also, the smoothing capacitor in the smoothing circuit and the ringing capacitor in the phone can be discharged when the ringing signal generation is stopped, ensuring safety. Furthermore, it is possible to detect the off-hook of the telephone, and it is possible to easily stop the sending of the ringing signal during the off-hook.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a configuration of a ringing signal generation circuit of the present invention according to the present invention.

FIG. 2 is an explanatory diagram showing a timing of an on / off operation of a signal in each circuit of FIG.

FIG. 3 is a flowchart showing an operation example of the ringing signal generation circuit in FIG. 1 at the end of ringing signal generation.

[Explanation of symbols]

1: Inductor, 2: Switching circuit, 3: Oscillation circuit, 4: Smoothing circuit, 5: Grounding control circuit, 6: Basic oscillation circuit, 7: High resistance, 8: Communication line, 9: Telephone, 10: Off-hook detection circuit , 11: oscillation stop circuit, 12: ring stop circuit, AG: AND circuit, C1: smoothing capacitor, C
2: Ring capacitor, DI: Diode, DTR: Discharge transistor, IG: Inverter circuit, OTR: Off-hook detection transistor, STR: Switching transistor

Claims (5)

[Claims] 1. A ringing signal generation circuit for generating a ringing signal for ringing a telephone at a cycle of a fundamental frequency,
An inductor that stores energy by a direct current, a basic oscillation circuit that generates a signal of the above-mentioned fundamental frequency, an oscillation circuit that generates a high-frequency signal, and switching control of the current flowing through the inductor based on the high-frequency signal from the oscillation circuit. A switching circuit, a smoothing circuit for smoothing the back electromotive force of the inductor generated by switching control of the switching circuit, and an output of the smoothing circuit based on a basic frequency signal from the basic oscillator circuit at a cycle of the basic frequency. A ringing signal generation circuit comprising a grounding control circuit for grounding. 2. The ringing signal generation circuit according to claim 1, further comprising a modulation circuit for performing a logical product operation of the inverted signal of the fundamental frequency signal and the high frequency signal, and based on a logical product operation result by the modulation circuit. A ringing signal generating circuit, wherein switching control of the switching circuit is performed, and a switching operation of the switching circuit and a grounding operation of the grounding control circuit are shifted by a half cycle with respect to the fundamental frequency. 3. The ringing signal generation circuit according to claim 1 or 2, wherein a load is provided on the output side of the smoothing circuit, and the load is applied when the ground control circuit is not grounded. A ringing signal generating circuit, wherein the output of the smoothing circuit is grounded via the ringing signal generating circuit. 4. The ringing signal generating circuit according to claim 1, wherein after the operation of the oscillation circuit is stopped, the output of the smoothing circuit is grounded by the grounding control circuit. A ringing signal generating circuit comprising an oscillation stopping means for stopping the operation of the basic oscillation circuit after discharging the smoothing capacitor in the smoothing circuit. 5. The ringing signal generation circuit according to claim 1, wherein an off-hook detecting means for detecting an off-hook state of the telephone, and a detection result of the off-hook state of the telephone by the off-hook detecting means. And a ringing signal stopping means for stopping the generation of the ringing signal.