JPH0646117Y2 - Data transmission circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a data signal transmission circuit.

[Conventional technology]

One between the main unit of the key telephone unit and the slave unit.
A pair of call line and signal line are used to connect the two, and power is supplied to the child device via the signal line or both the call line and the signal line. In addition, the conventional method is to transmit a data signal that changes in the positive and negative directions.In the past, in general, a pulse-shaped signal that changes in the negative direction was used as the data signal, and a DC voltage applied to the signal line via the transformer was used. It is supposed to be superimposed on the voltage.

[Problems to be solved by the invention]

However, as shown the voltage waveform of the signal line in FIG. 4 (A), gradually DC voltage E is decreased in accordance with the superposition of the data signal S _d, it is assumed that gradually increases in accordance with the stop of the data signal S _d, Since this is repeated, the power supply voltage supplied to the slave unit fluctuates, and the reference voltage V _S for detection is fixed in the receiving circuit as shown in the enlarged view of FIG. When the voltage drops, problems such as unstable detection status occur.

Note that this is because the DC voltage E generally fluctuates depending on the positive / negative of the pulse forming the data signal due to the distributed capacitance of the signal line and the characteristics of the transformer, and the power supply voltage is changed through the signal line to the slave unit side. When power is supplied to the power source, a smoothing capacitor is connected in parallel with the power source extraction circuit on the slave side, and the capacitor is discharged due to the area ratio of the negative direction component N and the positive direction component P of the data signal S _d. This is caused by the fact that the DC voltage E gradually decreases in response to this, the capacitor is charged again due to the end of the data signal S _d , and the DC voltage E gradually increases accordingly.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention comprises the following means.

That is, in the circuit for transmitting the above data signal,
A voltage divider circuit that divides the power supply voltage so that the average value of positive / negative bidirectional changes of the data signal becomes zero and applies this divided voltage to one end of the primary winding of the transformer, and the primary winding of the transformer. Of a transformer connected between one end and the other end of the transformer, and a first transistor connected between the collector and the emitter between the power supply and the other end of the primary winding of the transformer and the primary of the transformer. A second transistor whose collector and emitter are connected between the other end of the winding and the common circuit. The first and second transistors complementarily turn on and off in response to a data signal and do not transmit. At times, a drive circuit in which both transistors are turned off is provided.

[Action]

Therefore, during transmission of the data signal, the first and second transistors of the driving circuit complementarily turn on and off in response to the data signal, and when the first transistor is on, the first and second transistors of the transformer are turned on. When the power supply voltage is applied to the secondary winding and current flows from the other end of the primary winding to one end, and the second transistor is on, the other end of the primary winding is connected to the common circuit A current flows to the end, and this is repeated, and a data signal that changes in both positive and negative directions is induced in the secondary winding of the transformer, and this is superimposed on the DC voltage, so the waveform of the data signal is DC. The voltage changes in both positive and negative directions, the average value of which changes to zero, the capacitor on the slave unit side does not charge or discharge, and the DC voltage does not fluctuate.

Further, since a resistor is connected between one end and the other end of the primary winding of the transformer for impedance matching, for example, when the transmission of the data signal is completed and each transistor is turned off, the primary winding is The potential at the other end of the line immediately becomes equal to the divided voltage, and as a result, stable and accurate data transmission can be performed.

〔Example〕

Hereinafter, the details of the present invention will be described with reference to the drawings showing embodiments.

FIG. 2 is a block diagram of a key telephone device. A main unit (hereinafter, KSU) 1 and a slave unit (hereinafter, ST) 2 are connected by a pair of signal line 3 and call line 4, respectively. Transformers T ₁ , T ₂ and T ₃ , T ₄ are connected to both ends of each of these, and the primary winding of the transformer T ₁ has a selector (hereinafter referred to as SEL) 11 and a capacitor C _S by an analog switch. A data transmission / reception unit (hereinafter, SR) 12 is connected through the same, while a primary winding of the transformer T ₂ is connected with a communication path switch (hereinafter, TRS) 13 by an analog switch for exchange connection. , Between the neutral points provided in the secondary windings of the transformers T ₁ and T ₂ ,
Power supply unit (hereinafter PS) via Posister POS for current limitation 1
4 is connected, and it is supposed that the fantom power supply will be performed by this.

Further, the ST2 side, transformer T ₃ to the primary winding SR21 is connected, transformer T ₄ of the primary winding calls in circuit (hereinafter, TKC) 22
Together but are connected, transformer T _3, stabilization of the power supply extraction between neutral point provided on each secondary winding of T ₄ (hereinafter, RE
G) 23 and a smoothing capacitor C _P are connected, which stabilizes the power supplied from KSU1 via signal line 3 and call line 4 and requires it as a local power supply VB. It is to be supplied to each part.

In the KSU1, the transformers T ₁ and T ₂ and the signal line 3,
SEL11 and TRS13 go to ST2 via the same route as call line 4.
In addition to being connected to other STs similar to the above, SEL11 and TRS13 are also connected to the power supply 10V for analog switch and its common circuit SG, and are connected to the primary windings of the transformers T ₁ and T ₂ . In, the power supply 5V is applied to one end, and the other ends are individually connected to the SEL11 or TRS13.

Therefore, the SEL11
There follow to select the ST ^# 1~ ^# n, the control data transmitted from the SR12, reception by SR21 of this, and the operation data transmitted from the SR21, transformer T ₁ reception by SR12 is this, T ₃
Via the signal line 3 and the control unit controls the TRS 13 according to the contents of the signal line. Therefore, the TKC22 is exchange-connected via the transformers T ₂ and T ₄ and the call line 4, and the call by the TKC 22 is performed. At the same time, the display etc. on the ST2 side are performed in response to the reception of the control data by SR21.

FIG. 1 is a circuit diagram showing SR21 on the ST side, and the secondary winding N _S
To the primary winding N _P of the transformer T ₃ connected to the signal line 3, the divided voltage V _{d of the} voltage dividing circuit of the resistors R _{1 to} R ₄ is applied to one end of the primary winding N _P , and the alternating current A capacitor C ₁ for the shunt path is connected, and the voltage divider circuit divides the voltage of the power source VB to generate a divided voltage V _d , and at the same time, a high first reference voltage V _S1 and, The second reference voltage V _S2 lower than this is generated.

The primary winding N _P has a resistor for impedance matching.
With R ₅ is connected between the this other end and the power source VB and the common circuit, each first and second transistor
The collector and the emitter of Q ₁ and Q ₂ are connected, and the noise elimination diodes D ₁ and D ₂ each having a polarity opposite to that of the power supply VB are connected.

However, transistors Q ₁ and Q ₂ of opposite polarity are used, the collectors are commonly connected, and a single-ended / complementary / push-pull-type drive circuit is configured. ON / OFF is controlled by each transmission data signal D _S and control signal D _C via ₆ , R ₇ , an inverter (hereinafter, IN) 31, and an input inverting type AND gate 32.

Therefore, as shown in FIG. 3 showing the waveforms of the respective parts in FIG. 1, in the transmission side (A), the transmission signal D _S (a) is “L” (low level) and the control signal D _C (b). Is not high (high level), the output of IN31 is high and AND gate 32
Output is "L", both the transistors Q ₁ and Q ₂ are off, and the divided voltage V _d appears as it is at the other end of the primary winding N _{P as} the primary voltage (c). On the other hand, if the control signal (b) becomes "L" and the transmission signal (a) repeats "H" and "L", the IN signal is sent according to "H" of the transmission signal (a).
The output of 31 turns to “L” and the transistor Q ₁ turns on, while the output of the AND gate 32 remains “L”, the transistor Q ₂ remains off, and the primary voltage (c) There while rises to a voltage of the power supply VB, if the transmission signal (a) is "L", whereas Do connexion transistor Q ₁ and the output is "H" of the IN31 is turned off, the output of the aND gate 32 "H" turned into the transistor Q ₂ reduces on and summer Te primary voltage (c) to the voltage V _l.

Therefore, if the resistance values of R _{1 to} R ₄ are set so that V _B −V _d ≈V _d −V _l is established by the complementary turning on and off of the transistors Q ₁ and Q ₂ , the primary voltage ( The average value of the positive and negative bidirectional changes based on the divided voltage V _d of c) becomes almost zero, and a waveform corresponding to this is induced in the secondary winding N _S , and this is superimposed on the DC voltage by PS14. The capacitor C _P is neither charged nor discharged, and the DC voltage does not change.

In addition, the drive circuit including the transistors Q ₁ and Q ₂ has a low output impedance at the time of turning on, and each line 3, which has a distributed capacitance,
4 is preferable because sufficient excitation can be performed via the transformer T ₃ .

Besides, in the transmission data signal (a), the periods of “H” and “L” are not always the same in general, and depending on the situation,
Resistor in a state where the positive and negative average value of the primary voltage is almost zero
The values of R _{1 to} R ₄ may be set.

On the other hand, at the other end of the primary winding N _P , which becomes the secondary winding when receiving,
Comparator using a differential amplifier via resistor R ₈ (hereinafter CP)
The non-inverting input of 33 is connected as a comparison input, and the analog input (hereinafter referred to as AS) 36, 37 that constitutes the reference voltage supply circuit is connected to the reference input using this inverting input.
The via, reference voltage V _S1, V _S2 has summer as selectively provided, for between the input of the CP33, the capacitor C ₂ for noise removal is connected.

The output of CP33 is power VB is applied through a resistor R ₉ of the pull-up in accordance with the voltage change of the comparator input "H",
"L" and summer as exhibiting binary, which through IN34, after receiving the further noise removed by the capacitor C _3, while being sent as a received data signal D _R, AS through IN35
It is supposed to drive 36 and directly drive AS 37.

Therefore, as shown in the third view of (B) (d) ~ ( f), since normally the primary voltage (d) is a divided voltage V _d, a comparison output (f) is "L", When AS36 is turned on and the reference input (e) is balanced by the state of VS ₁ , the received data signal (d) through the transformer T ₃ changes in the positive direction and exceeds the reference voltage V _S1. Output (f) turns to "H", AS36 turns off, AS37 turns on, and reference input (e)
If V _S2 is given, the comparison output (f) keeps “H” during the voltage of the received signal (d) is longer than this, and the voltage of the received signal (d) drops to the reference voltage V _S 2 or less, the comparison The output (f) becomes "L", and in response to this, AS36 turns on again, AS37 returns to the off state, and V _S1 is applied to the reference input (e), and the voltage of the received signal (d) becomes the reference. The comparison output (f) is maintained at "L" for a period of voltage V _S1 or less, and the above operation is repeated according to the change of the received signal (f).

Therefore, even if the waveform distortion occurs due to the transmission through the signal line 3 and the transformers T ₁ and T ₃ , the binary comparison output (f) of “H” and “L” is surely obtained and The reference voltage is selected as an optimum value according to the output level of the comparison output (f), and even if a waveform change D due to noise or the like occurs in the received signal (d), this does not affect the comparison output (f). Becomes

Further, as shown in FIG. 4 (B), even if the peak value of the data signal S _d changes, the detection situation becomes reliable by selecting the reference voltage.

Therefore, if the comparison output (f) is inverted by IN34 and sent out as the reception signal D _R , and given to the control unit not shown in the figure,
The reception data signal (d) is surely received.

Note that the control unit may stop accepting the reception signal D _R during transmission of the transmission signal D _S , but during reception of the reception signal D _S
The transmission state may be confirmed by monitoring D _R and checking the coincidence with the transmission signal D _S, and SR12 of KSU1 may have the same configuration as that in FIG.

Therefore, the DC voltage supplied from KSU1 does not change due to the data signal and can be supplied as a constant voltage to ST2, and at the receiving side, the peak value change of the data signal,
Stable and reliable reception of data signals is performed without being affected by waveform changes, waveform distortion, and the like.

However, in FIG. 2, it is assumed that the power supply from the KSU1 is performed only by the signal line 3, and accordingly PS14 and
The connection status of REG23 may be determined and SR12 may be provided for each ST in the same manner. In FIG. 1, the divided voltage V _d and the reference voltages V _S1 and V _S2 are generated by separate circuits. Alternatively, transistors Q ₁ and Q ₂ having the same polarity may be used, and the driving situation may be complementary, and a selector or the like may be used instead of AS 36 and 37.

Further, it is not always necessary to use both the transmitting circuit and the receiving circuit in FIG. 1, but to use only one of them and to apply the conventional circuit to the other, almost the same result is obtained, and only the button telephone device is provided. Instead, it can be applied to various transmission systems using the same data signal.

In addition, the waveform of the data signal is not only pulse-shaped,
As long as it changes in both the positive and negative directions, various waveforms can be selected according to the conditions, and various modifications are possible.

[Effect of device]

As is clear from the above description, according to the present invention, when a data signal that changes in the positive and negative directions with respect to a DC voltage is superimposed and transmitted, the power supply voltage is set so that the average value of the positive and negative bidirectional changes of the data signal becomes zero. Voltage is applied to one end of the transformer, and the first transistor whose collector and emitter are connected between the power supply and the other end of the primary winding and the other end of the primary winding and the common circuit Since the above-mentioned data signal is transmitted by complementary ON / OFF of the second transistor whose collector and emitter are connected to each other, and each transistor is turned off when not transmitting, the waveform of the data signal is a DC voltage. , The average value becomes zero, and as a result, for example, when data is transmitted from the main unit side to the slave unit, the capacitor on the slave unit side does not generate charge and discharge, and Variations no longer occur, significant effects in various data signals transmitted are obtained.

Further, since a resistor is connected between one end and the other end of the primary winding of the transformer for impedance matching, for example, when the transmission of the data signal is completed and each transistor is turned off, the primary winding is The potential of the other end of the line immediately becomes equal to the divided voltage, and as a result, the data signal can be transmitted stably and accurately.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a circuit diagram of a data transmitting / receiving unit, FIG. 2 is a block diagram of a button telephone device, FIG. 3 is a waveform diagram of each unit in FIG. 1, and FIG. It is a wave form diagram which shows an example. 3 ... Signal line, 14 ... PS (power supply), 12,21 ... SR (data transceiver), 31,34,35 ... IN (inverter), 32 ...
… AND gate, 33 …… CP (comparator), 36,37 …… AS (analog switch), T _{1 to} T ₄ …… Transformer, Q ₁ , Q ₂ …… Transistor, R _{1 to} R ₉ …… Resistor, VB ... power supply, V _d ... divided voltage, V _S1 , V _S2 ... reference voltage, D _S ... transmission signal, D _C ... control signal, D _R ... reception signal.

Claims (1)

[Scope of utility model registration request] 1. A circuit for transmitting a data signal, which changes in a positive or negative direction with respect to a DC voltage applied to a pair of signal lines, after being superimposed through a transformer, and transmits a power supply voltage as an average of positive and negative bidirectional changes of the data signal. Connected between a voltage dividing circuit that divides the voltage so that the value becomes zero and applies the divided voltage to one end of the primary winding of the transformer, and one end and the other end of the primary winding of the transformer. And a first transistor having a collector and an emitter connected between the power supply and the other end of the primary winding, and a collector between the other end of the primary winding and the common circuit. Driving in which the first and second transistors are complementarily turned on and off in response to the data signal and each of the transistors is turned off when not transmitting, the second transistor having emitters connected to each other And a circuit. Over data transmission circuit.