JPH0450788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit that supplies local power within a telephone set using a loop current flowing from a telephone line.

[Conventional technology]

Public telephones require a control power source to control calls, charge collection, etc., and use part of the loop current that flows from the switchboard power supply via the telephone line to supply local power. It has become something to do.

In other words, a constant voltage element such as a constant voltage diode is inserted into the DC loop that is closed in response to off-hook, and the terminal voltage of the constant voltage element generated by the loop current passing through the DC loop is used to prevent reverse current. Charge the capacitor through the diode,
The terminal voltage of this is supplied to the control section etc. as a power source.

However, if the loop resistance of the telephone line is high,
Charging of the capacitor is not completed immediately, and the rise in the terminal voltage of the capacitor is delayed, and it takes a considerable amount of time for the control unit to start responding to off-hook.
Since this would be inappropriate for handling, it is necessary to trickle charge the capacitor by passing a current through a relatively high-resistance resistor during on-hook so that the exchange does not respond, and to prevent the capacitor's terminal voltage from rising in response to off-hook. Generally, methods are used to speed up the process.

[Problem that the invention seeks to solve]

However, depending on the type of exchange or the standard of the terminal equipment, there may be cases where the line DC resistance value during off-hook must be set to an almost open state.
Under this condition, trickle charging cannot be used, and furthermore, if the line resistance is extremely high, even if trickle charging can be used, problems such as incomplete pre-charging of the capacitor will occur.

[Means for solving problems]

In order to solve the above-mentioned problem, the present invention is constructed by the following means.

That is, the above power supply circuit has a first capacitor that is charged by the loop current through the reverse current blocking diode and supplies power, and a large capacitor that is charged by the loop current through the reverse current blocking diode. a second capacitor and a first capacitor;
a voltage detection circuit for detecting that the terminal voltage of the first capacitor reaches a predetermined value after off-hook;
and a switching element connected between the second capacitor and turned on until the voltage detection circuit produces a detection output to supply the charge of the second capacitor to the first capacitor.

[Effect]

Therefore, in response to off-hook, the switching element turns on and connects the second capacitor to the first capacitor until the first capacitor is fully charged by the loop current. The held charge charges the first capacitor, and the terminal voltage of this capacitor quickly rises.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

Figure 2 is a block diagram of a public telephone, with line terminals L ₁ and L ₂ to which telephone lines from the exchange are connected.
In contrast, the switch HS ¹ and the receiving circuit (hereinafter referred to as
REC) 1, diode bridge (hereinafter referred to as DB)
2, a telephone call circuit (hereinafter referred to as TKC) 5 that forms a telephone call loop is connected via a power supply circuit (hereinafter referred to as PS) 3 and a forced disconnection circuit (hereinafter referred to as CB) 4, and a handset 6 A transmitter T and a receiver R are connected.

In addition, a control unit (hereinafter referred to as CNT) 7 consisting of a processor such as a microprocessor, memory, etc. is provided, and a frequency detection circuit (hereinafter referred to as FDT) 8,
Coin handling section (CPS) 9, which sorts and stores coins, dial key (DK) 1
0, switch HS ² , etc. makes control decisions according to each output, CPS9, display unit (hereinafter referred to as DP)
12, MF signal generator (hereinafter referred to as MFG) that generates an audio complex frequency (hereinafter referred to as MF) signal 13, TKC5,
It is also used to control CB4, etc.

In addition, MFG13 outputs DK10 and
In response to the control of CNT7, a permission signal is sent from CNT7.
Only when OK is given, it generates an MF signal according to the operation of the DK10, gives a control signal CS to the TKC5, sends the MF signal as a dial signal via the TKC5, and sends the monitoring information to the maintenance center, etc. When sending to CNT, MFG13
7, make a dial call to a specific destination such as a maintenance center in the same way as above, and then
Monitoring information is transmitted via the same route using MF signals.

On the other hand, PS3 closes the DC loop via TKC5 by turning on the switch ^HS1 due to the off-hook, and as the loop current with a constant polarity passes through DB2, the capacitor is charged by this, and the capacitor is The terminal voltage is used as a power supply V to be supplied to each part.

Therefore, by off-hooking and inserting a coin, the DC loop is closed and the CPS is
Since the CNT 7 sends a permission signal OK in response to the output of the caller 9, the DK 10 can make a dial call, and when the other party responds, the call can be made freely.

However, even if the other party answers, billing signals such as polarity reversal pulses do not arrive on this telephone line, and in order to detect the other party's response, REC1 using a transformer etc.
the incoming signal from the telephone line given through
The FDT 8 detects each frequency component, and the CNT 7 monitors whether this detection output D _f continues for a predetermined period of time. Depending on the result, the CNT 7 detects various signal tones and the other party's voice. After judging the other party's voice, it detects the other party's response, controls the CPS9 accordingly, stores the coin, eliminates the mute signal MUT for the TKC5, and turns off the transmitter T. While canceling the inoperable state, if the coins inserted and waiting become insufficient, CB4 is controlled to open the DC loop for a certain period of time, restore the exchange, and forcibly disconnect the call.

In addition, depending on the DP12, while the CNT7 sequentially displays coin input accumulation information, the CNT7 has a self-diagnosis function, and performs self-diagnosis according to the output of the hook switch HS ² in response to off-hook.
It detects that the storage safe in the CPS 9 is full, coins are jammed, the handset 6 is disconnected due to theft, etc., and accordingly, the DP 12 displays an indication that the device cannot be used.
The above-mentioned monitoring information is transmitted.

In addition, the FDT8 has a minimum detection level of each frequency component that can be varied by the control signal CL.
The CNT 7 controls the FDT 8 according to conditions, and successively sets the minimum detection level to a desired value.

In addition, a busy tone generator (hereinafter referred to as BTG) 14 that locally generates a busy tone is provided.
The BTG 14 sends a local busy tone according to the control of the
The signal is sent to the receiver R of the handset 6 via the transformer T to notify the user that a call is not possible.

Figure 1 is a circuit diagram of PS3 and its attached circuit, and Figure 2 shows a diode _D1 and a constant voltage diode ZD inserted into the DC loop of CB4 and TKC5, which are connected depending on the off-hook. Constant voltage diode caused by loop current
Based on the Zener voltage of ZD, part of the loop current charges capacitor C ₁ via diode D ₂ for reverse current blocking, and the first capacitor C ₂ connected in parallel also charges diode D ₂ and It is similarly charged via a transistor (hereinafter referred to as TR) _Q1 , and its terminal voltage is mainly supplied to the CNT7 as a power supply VD.

Also, there is a capacitor C ₂ between the emitter and collector.
TR Q ₁ inserted in series with the emitter
A resistor R ₁ is connected between the bases and
The base is connected to the collector of TR・Q ₂ via resistor R ₂ , and the resistor R ₃ is connected to the base of TR・Q ₂ .
The control circuit ( _hereinafter referred to as
According to the output of CNC) 18, ON/OFF of TR/Q ₁ is controlled.

On the other hand, CNC 18 includes resistors R ₅ to R ₇ and capacitor C ₃ for chattering absorption, inverters (hereinafter referred to as INV) 21 to 23, resistors R ₇ ', R ₈ for delay recovery timer, capacitor C ₄ and diode. D ₈ and a pull-up resistor R ₉ , to which the terminal voltage of the capacitor C ₁ is supplied as the power supply VS.

In addition, the power consumption of CNC18 is small, and for example, the capacitance of capacitor _C1 is
10000μF, the capacitance of capacitor C ₂ is selected as 1000μF, and the capacitance of C ₁ is almost smaller than that of capacitor C ₂ .
It is set as 10 times larger.

On the other hand, in PS3, a second capacitor _C5 and a capacitor _C6 are connected in parallel with the constant voltage diode ZD via a resistor _R10 and a reverse current blocking diode _D4 . capacitors C ₅ , C ₆ and capacitors
Between C ₁ and the first capacitor C ₂ via TR/Q ₁ , the emitter-collector of TR/Q ₃ , which is a switching element, and a resistor R ₁₁ are connected _. The emitter and collector of TR/ _Q4 are connected, and the TR/Q4 is connected between the emitter and collector.
A resistor R ₁₂ is connected between the base and emitter of Q ₃ and Q ₄ .
_R13 are connected to each other, and a control signal based on the detection power of a voltage detection circuit (hereinafter referred to as VDT) 19 is given to these bases.

On the other hand, the power supply VD due to the terminal voltage of capacitor _C2
VDT1 detects that the voltage has reached a predetermined value.
The power supply VD is applied to the output of ₉ through the pull-up resistor R14.
Resistors R ₁₅ , R ₁₆ and capacitors for noise rejection
C ₇ and INV 25 are applied to the AND gate 26, and the output of INV 25 is applied to the base of TR・Q ₄ as a control signal. When the diode D ₅ prevents the power source VS from looping around,
Resistor R ₁₇ and pull-up resistor R ₁₈
The output of INV22 is provided through INV27, which is similar to INV24 to which the power supply VD is applied to the input.

Moreover, the output of the AND gate 26 is connected to the resistor R ₁₉ ,
It is fed to the base of TR Q ₅ via the R ₂₀ circuit, the collector of which is connected to the base of TR Q ₃ , and the on/off of TR Q ₅ is a control signal for TR Q ₃ . It has become something that is given as a.

FIG. 3 is a timing chart showing the waveforms of each part in FIG. 1. When the hook switch HS ⁸ is turned on due to off-hook, the CNC 18 remains in an operating state due to the charge of the capacitor C ₁ even after the on-hook. , the input (a) of INV21 changes from "H" (high level) to "L" (low level),
The output of INV21 changes to "H" and the diode _D3
and a capacitor through a resistor R ₈ of low resistance value
Charge C ₄ and INV after e.g. 100ms delay time t ₁
Since the input of INV 22 is set to "H", its output (b) becomes "L", and accordingly, the output (c) of INV 23 becomes "H".

Then, TR・Q ₂ turns on, which causes
TR・Q ₁ also turns on, and in addition to the loop current through diode D ₂ , a charging current due to the charging current of capacitor C ₁ flows into capacitor C ₂ , and the voltage (d) of power supply VD rises rapidly. .

This voltage (d) is monitored by the VDT19, and the detection power (e) is set to "H" until the voltage (d) reaches a predetermined value _V1 , so the INV25 is Since the output (f) of INV22 is also "H" and the output (b) of INV22 is "L", the output of INV27 is also "H", and the output (g) of AND gate 26 is "H". It becomes “H” and this is the power supply.
As the voltage of VD increases, if the voltage between the base and emitter of TR Q ₅ becomes V ₂ or higher, TR Q ₅ turns on, and the collector potential (h) of TR Q ₅ becomes "L". Correspondingly, TR Q ₃ also turns on, and the charge held in capacitors C ₅ and C ₆ causes low resistance resistors R ₁₁ and
Charge capacitor C ₂ via TR Q ₁ .

Therefore, capacitor C ₂ has a loop current of
Charge of capacitor C ₁ and capacitor
It is rapidly charged by the charges of C ₅ and C ₆ , and the power supply
The voltage (d) of VD immediately rises and reaches the predetermined value V ₁ in a short time in response to off-hook.

Then, since the VDT19 generates the detected force (e) as "L", the output (f) of the INV25 and the output (g) of the AND gate 26 also become "L", and accordingly,
TR・Q ₅ turns off and the collector potential (h) becomes “H”
As a result, TR Q ₈ is also turned off, and while capacitors C ₅ and C ₆ are disconnected from capacitors C ₁ and C ₂ , the output
TR・Q ₄ is turned on by “L” in (f), and this
Capacitor C ₅ due to loop current through TR Q ₄ ,
Complete the C ₆ charging path. In this case,
Turn TR/Q ₃ on and connect a large capacitor
When trying to charge C ₅ and C ₆ , most of the loop current flows through TR・Q ₃ and TR・Q ₁ to various parts such as CNT 7, so the discharged capacitors C ₅ and C ₆
As a result, these large capacity capacitors C ₅ and C ₆ cannot be charged in a short period of time. Therefore, after the voltage (d) of the power supply VD reaches a predetermined value V ₁ , by keeping TR Q ₃ in the off state, these capacitors C 5 , C ₅ ,
This allows the C ₆ to be charged quickly.

Therefore, even if the charging status due to the loop current is delayed due to the relationship with the line resistance value, the capacitor
C ₁ , C ₅ , and C ₆ are immediately charged by the charges, and the terminal voltage of capacitor C ₂ immediately rises, and the supply of power VD starts immediately in response to the off-hook, and the response of CNT 7, etc. After this, the loop current continues to charge capacitors C ₁ and C ₂ , and
After the voltage (d) of the power supply VD reaches the predetermined value _V1 , the capacitors _C5 and _C6 are similarly charged.

In addition, as the capacitor _C5 , for example, a super capacitor (Nippon Electric Co., Ltd.) with a large capacity of 0.036F
(manufactured by KK), etc., and in this case, the equivalent series resistance value is relatively large, for example, a 1000 μF capacitor.
_C6 is connected in parallel to reduce overall impedance.

In addition, as VDT19, integrated circuit MB3761
(manufactured by Fujitsu KK) etc. are suitable.

In addition, for the constant voltage diode ZD,
A plurality of sets of diodes and capacitors (not shown in the figure) are connected, and power is supplied to each of the other parts individually.

In response to the above, an on-hook is made in response to the end of the call, the switch HS ³ is turned off, and the INV
When the input (a) of INV21 becomes "H", the output of INV21 immediately becomes "L", but the high resistance value resistor
Through R ₇ and the output impedance of INV21,
As the charge of capacitor _C4 gradually discharges,
For example, the input of INV22 maintains "H" for a delay time t ₂ of 2 _S , and accordingly, the output (c) of INV23 also maintains "H", and TR・Q ₂ and Q ₁ are turned on.
During this time, the CNT 7 performs post-processing control such as storing coins.

Also, during this time, the voltage is increased depending on the disconnection of the loop current.
(d) gradually decreases, and the VDT 19 returns the detection force (e) to "H" when _the voltage (d) decreases to a value _V3 lower than the predetermined value V1 due to the hysteresis characteristic.
Accordingly, the output (f) becomes “H” and the output (g) also becomes “H”.
The output (b) of INV22 changes to "H" only while it is "L", turns on TR・Q ₅ , sets the collector potential (h) to "L", turns on TR・Q ₃ , and connects the capacitor C _2.
back up the power supply VD.

However, as mentioned above, the capacitor C ₅ has an extremely large capacity, and even after the output (c) becomes "L" and TR Q ₁ is turned off, it retains a sufficient charge, and the capacitor C ₁ Since capacitor _C5 is the last to receive charge, it retains enough charge for the next off-hook.

Therefore, even if the charging of the capacitor _C2 is delayed due to the relationship with the line resistance value, the initial charging is mainly performed by the charge held by the capacitor _C5 , and the voltage of the power supply VD increases quickly, and the CNT7 for off-hook Control is immediately started.

However, each of the capacitors C ₁ , C ₂ , and C ₅ may be provided in plural numbers, and other switching elements may be used in place of TR/Q ₃ .
Capacitors C ₁ , C ₆ and TR/Q ₁ etc. can also be omitted.

Also, as VDT19, it is the same even if a comparator etc. is used, and accordingly INV24 to TR.
You only need to select a configuration such as Q ₅ , and the delay time of CNC18 can be determined according to the conditions.
The configuration of 18 can be arbitrarily selected according to the situation, and the configuration shown in FIG. 2 can also be modified in various ways, such as being determined according to the operating conditions.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, even if charging of the capacitor by the loop current is delayed due to the relationship with the line resistance value, initial charging is performed by the charge held by a separate capacitor, and power is supplied. The terminal voltage of the power supply capacitor rises quickly, and the control unit immediately responds to the off-hook, and after the terminal voltage of the power supply capacitor reaches a predetermined value, the switching element is turned off to separately control the voltage. Since the capacitor (second capacitor) can be quickly charged, a remarkable effect can be obtained in various telephones that supply power based on loop current.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, Fig. 1 is a circuit diagram of a power supply circuit and ancillary circuits, Fig. 2 is a block diagram of a public telephone, and Fig. 3 is a timing chart showing waveforms of various parts in Fig. 1. . 2...DB (diode bridge), 3...PS
(power supply circuit), 5...TKC (communication circuit), 7...
CNT (control unit), 18...CNC (control circuit), 19
...VDT (voltage detection circuit), 21 to 25, 27...
...INV (inverter), 26...AND gate,
L ₁ , L ₂ ... Line terminal, ZD ... Constant voltage diode,
_D1 to _D4 ...Diode, _C1 to _C7 ...Capacitor,
_Q1 to _Q5 ...TR (transistor), _R1 to _R20 ...Resistor.

Claims (1)

[Claims] 1 In a power supply circuit of a telephone that charges a capacitor with a loop current passing through a DC loop and supplies the terminal voltage of the capacitor as a power supply, a first circuit that is charged by the loop current through a reverse current blocking diode and supplies the power. Detecting that the terminal voltages of the first capacitor, a second capacitor having a large capacity that is charged by the loop current through a reverse blocking diode, and the first capacitor have reached a predetermined value after off-hook. a switching element that is connected between the first and second capacitors and is turned on until the voltage detection circuit generates a detection output and supplies the charge of the second capacitor to the first capacitor. A power supply circuit for a telephone set.