JPS6361549A - Power supply circuit for telephone set - Google Patents

Abstract

PURPOSE:To quickly raise the terminal voltage of a power supply capacitor and to operate a control part in conformity with off-hook by performing an initial charging by the charging electric charge held in another capacitor even if the charging of a capacitor by a loop current is delayed. CONSTITUTION:A diode D1 and a Zener diode ZD are inserted to a DC loop, and a capacitor C1 is charged through a diode D2 based on the Zener voltage of the diode ZD generated by the loop current conducted in accordance with off-hook. When a hook switch HS<8> is turned on by off-hook, transistors TRs Q1 and Q2 are turned on, and not only the loop current passing the diode D2 but also the charging current by the charging electric charge in the capacitor C1 is conducted to a capacitor C2, and the voltage (d) of a power source VD quickly rises. Then, TRs Q5 and Q3 are turned on, and the capacitor C2 is quickly charged through the TR Q1 by the charging electric charge held in capacitors C5 and C6, and the voltage (d) of the power source VD immediately rises to reach a prescribed value V1. Then, a voltage detecting circuit VDT 19 outputs a detection output (e) to turn off TRs Q5 and Q3 and turn on the TR.Q4.

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 a portion of the loop current that flows from the switchboard power supply via the telephone line to provide local power supply. It is intended to provide supplies.

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 causes the reverse current blocking diode to be activated. The capacitor is charged through the capacitor, and the terminal voltage of the capacitor is supplied to the control unit etc. as a power source.

However, if the loop resistance value of the telephone line is high, charging of the capacitor will not be completed immediately and the voltage rise at its terminal will be delayed), and it will take a considerable amount of time for the control unit to start responding to off-hook. However, since this would be inappropriate for handling, even during on-hook, a current to the extent that the switch does not respond is passed through a resistor with a relatively high resistance value, thereby trickle charging the capacitor, and then charging the capacitor in response to off-hook. Generally, means are used to quickly increase the terminal voltage.

[Problem that the invention seeks to solve]

However, depending on the type of exchange or the standard of the terminal equipment, the line DC resistance value during off-hook may have to be in an open state, and under this condition,
If trickle charging cannot be used and the line resistance value 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 implemented by the following means.
+4.

That is, in the above-mentioned power supply circuit, there is 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. Second
a capacitor, a voltage detection circuit that detects that the terminal voltage of the first capacitor reaches a predetermined value after off-hook, and a voltage detection circuit that is connected between the first and second capacitors until the voltage detection circuit generates a detection force. A switching element that is turned on during the period is provided.

[Effect]

Therefore, in response to off-hook, the switching element is turned on to connect the second capacitor to the first capacitor until the first capacitor is fully charged by the loop current, and the second capacitor holds This charge charges the υ first capacitor, and the terminal voltage of this capacitor quickly rises.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to figures showing actual cases.

Figure 2 is a block diagram of a public telephone. Line terminal L, L2, to which the telephone line from the exchange is connected, has a hook switch H81, a receiving circuit (hereinafter referred to as REC) 1, and a diode bridge (hereinafter referred to as DB). ) 2. Power supply circuit (hereinafter referred to as P
S) 3, and a forced disconnection circuit (hereinafter referred to as CB) 4,
A communication circuit (hereinafter referred to as TKO) 5 that forms a communication loop
A transmitter T and a receiver R of the handset 6 are connected to this.

In addition, a control unit (hereinafter referred to as CNT) 7 consisting of a processor such as a microprocessor and memory, etc., a frequency detection circuit (hereinafter referred to as FDT) 8, and a coin processing unit (hereinafter referred to as CPS) that performs sorting and storage of coins, etc. are provided. )9, dial key (hereinafter referred to as 0K) io, hook switch H8'', etc., makes control decisions according to each output, CPS9,
Display unit (hereinafter referred to as DP) 12, audio composite side V<hereinafter referred to as MF signal generator (hereinafter referred to as MF'G) 13 that generates a signal
, TKC5, CB4, etc.

In addition, MFG13 is connected to the output of DKl 0 and CNT7.
In response to the control of the TKC5, only when the permission signal OK is given from the CNT7, an MF multiplication signal is generated in accordance with the operation of the DKlo, and a control signal CS is given to the TKC5.
When transmitting monitoring information to a maintenance center, etc., the MFG
13 makes a dial call to a specific destination such as a maintenance center under the control of CNT7 in the same manner as described above, and then
Monitoring information is transmitted from the MF multiplied signal via the same route.

On the other hand, PS3 has hook switch H8 with off-hook
When 1 is turned on, a DC loop is closed via 9 and TKC5, and as the loop current with a constant polarity flows through DB2, the capacitor is charged by this, and the terminal voltage of the capacitor is used as the power supply V to connect each part. It is intended to be supplied to

Therefore, if off-hook and coin insertion are performed, the DC loop is closed and the CNT 7 sends out a permission signal OK in response to the output of the CPS 9, so the DKl
It becomes possible to make a dial call using o, and the call can be made freely depending on the response from the other party.

However, even if the other party responds, a signal such as a polarity reversal pulse does not arrive on this telephone line, and in order to detect the other party's response, the telephone line is connected via a RECl using a transformer, etc. The FDT 8 detects the incoming signal for each frequency component, and the CNT 7 monitors whether this detection output Df continues for a predetermined period of time. After determining the other party's voice, the other party's response is detected based on the judgment of the other party's voice, and according to this, the CPS S is controlled, the coin is stored, the mute signal MUT for TKC5 is extinguished, and the transmitter is While releasing T's inoperable state, if there is a shortage of waiting coins due to coins being thrown in, it controls C84 to open the DC loop for a certain period of time, restores the exchange, and forcibly disconnects the call. .

Depending on the DP12, the CNT7 sequentially displays the coin insertion and accumulation status, while the CNT7 has a self-diagnosis function, and performs self-diagnosis according to the output of the hook switch H8'' in response to off-hook, and checks the storage safe during CPSS. It detects whether the device is full, coins are jammed, disconnection due to theft of the handset 6, etc., and accordingly, the DP 12 displays an indication that the device is unusable, and also sends the above-mentioned monitoring information.

In addition, the FDT 8 has a minimum detection level of each frequency component that is freely variable by a control signal CL, and the CNT 7 controls the FDT 8 according to the conditions and sequentially 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, and the BTGl 4 sends out a local busy tone according to the control of the CNT 7, and the transformer T is The signal is sent to the receiver R of the handset 6 via the receiver R to notify the user that the call is not possible.

Figure 1 is a circuit diagram of PS3 and the circuits attached to it, and diode D1 and constant voltage diode ZD are inserted into the DC loop of C84' and TKC5 shown in Figure 2. Based on the Zener voltage of the constant voltage diode ZD generated by the loop current flowing through the loop current, the capacitor C0 is charged by a portion of the loop current through the reverse current blocking diode D3, and the first Capacitor C2 is also diode D
, and through a transistor (hereinafter referred to as TR) Ql,
It is similarly charged, and its terminal voltage is mainly supplied to the CNT 7 as the power supply VD.

In addition, a TR-Q shield is inserted between the emitter and collector in series with the capacitor C2, a resistor R1 is connected between the emitter and the pace, and the pace is connected to the resistor R2.
Connected to the collector of TR-Q through 1 and υ, TR
- Q, in response to the output of the control circuit (hereinafter referred to as CNC) 1B applied through the circuit of resistors R3, R, to the pace of T.
The on/off of R-Ql is controlled.

On the other hand, CN01B is a resistor R for chattering absorption.
6 to R7, capacitor C8, inverter (hereinafter referred to as I
NV) 21-23, resistor R,', R8, capacitor C2 and diode D8 for delayed recovery timer,
It consists of a pull-up resistor R0, and only for these, the terminal voltage of the capacitor C is equal to the power supply vS.
It is supplied as.

In addition, the power consumption of CNC18 is small, and
For example, the capacitance of capacitor C0 is selected as 10000 μF, the capacitance of capacitor C2 is selected as 1000 μF, and the capacitance of C□ is set to be 10 times larger than that of capacitor C8.

On the other hand, in PS3, the constant voltage diode Z
A second capacitor C5 and a capacitor C are connected in parallel with D through a resistor RIO and a diode D for reverse current blocking.
The emitter-collector of TR-Q8 used as a switching element and the resistor all are connected between capacitors C, , C, and capacitor C2 via capacitor C and TR-Ql. and resistor R□. , the emitter and collector of TR-Q are connected, and TR-Q BI Q
Resistors R12 and R are connected between the pace emitters of ', and a control signal based on the detection force of the voltage detection output circuit (hereinafter referred to as VDT) 19 is given to these paces. There is.

On the other hand, the output of VDT19, which detects that the voltage of the power supply (2) due to the terminal voltage of the capacitor C2 has reached a predetermined value, is supplied with the power supply VD through a pull-up resistor R, and this output INV24 has a level discrimination function with hysteresis characteristics, and resistor R51 for noise removal.
The output of INV25 is applied to the base of TR-Q as a control signal, and the other input of gate 26 is connected to the power supply. a diode 06 that prevents the power source VS from running around when VO disappears;
The output of INV22 is provided through INV27, which is similar to INV24, which includes a resistor R17 and a pull-up resistor R18 to which the power supply VD is applied.

Also, the output of the gate 26 is connected to the resistor R1911Rso
is applied to the base of TR-Q through the circuit of
The collector of this is connected to the base of TR-Q8 and TR
-Q, on/off is given to TR-Q as a control signal.

Figure 3 is a timing chart showing the waveforms of each part in Figure 1.
8 is turned on, the CNC 18 remains in operation due to the charging of the capacitor mouthpiece even after on-hook.
Since the input of INV21 (,) charges the capacitor C6 through the resistor R8 of rHJ value, and the input of INV22 becomes rHJ after a delay time t1 of, for example, 100m5, its output (,) is "L" and ab, Accordingly, INV23
The output (c) becomes rHJ.

Then, TR-Q turns on, which causes TR-Q to turn on.
Ql also turns on, and in addition to the loop current through the diode D2, a charging current due to the charging current of the capacitor mouth flows into the capacitor C8, and the voltage (d) of the power supply (2) rapidly rises.

This voltage (d) is monitored by VDT19.
Since the detection force (, ) is set to rHJ until the voltage (d) reaches the specified value V, the I
The output (f) of NV25 is also rHJ, and I
NV22 (Since D output (b) is equal to rLJ,
The output of INV27 is also set to "H", and the [F] gate 26
The output (g) is rHJ, which increases the base-emitter voltage V8 of TR-Q as the voltage of the power supply VD increases.
If this is the case, TR-Q is turned on, causing redundant Q.

The collector potential (h) of is rLJ and Hikoshi, and T
R-Q,l also turns on, and the charge held in capacitors C,,C, charges capacitor C2 through low resistance value resistor R1□ and TR-Ql.

Therefore, the capacitor C2 is rapidly charged by the node current, the charge of the capacitor C1, and the charge of the capacitors C, , C, and the voltage (d) of the power supply VD. immediately rises and reaches the predetermined value Ve in a short time in response to off-hook.

Then, since vDT19 generates the detected force (e) as rLJ, the INV25 output (f) and the output value of AND gate 26) also become "L", and accordingly, TR-
Q, turns off, sets the collector potential (h) to rHJ, turns off TR-Q8, and disconnects capacitors C, , C, and capacitors C1+C3, while output (f) turns 1
-L" turns TR-Q on), resistor R,
By bypassing the loop current, the charging path of the capacitors C5 and C is completed.

Therefore, even if the charging status due to the loop current is delayed due to the relationship with the line resistance value, the capacitor opening and C, .
C, is immediately charged by the charged load, the terminal voltage of capacitor C3 rises immediately, and the supply of power VD starts immediately in response to off-hook, and CNT7 etc. immediately respond. , the loop current causes capacitor C1,C.

continues to be charged, and the voltage of one power supply VO (
d) has slowed down to the predetermined value v1, the capacitors C, , C6
is charged in the same way.

In addition, as the capacitor C5, for example, 0.036 F
A supercapacitor (manufactured by 1tK, Japan) with a large capacity of ing.

Further, as the VDT 19, an integrated circuit MB3761 type (manufactured by Fujitsu) or the like is suitable.

In addition, a plurality of sets of diodes and capacitors (not shown in the figure) are connected to the constant voltage diode ZD, thereby supplying power to each of the other parts.

In contrast to the above, when the call ends, on-hook disappears.
The hook switch 38 is turned off and the input of INV21 (
, ) becomes rHJ, the output of INV21 immediately becomes r
LJ and high resistance resistor R9 and INV2
Since the charge in the capacitor C6 is gradually discharged through an output impedance of 1, the Nv220 input maintains rHJ for a delay time t of 211, and accordingly, the output (C) of INV23 also maintains rHJ. TR-Q
B+Qt is turned on, and during this time the CNT 7 performs post-processing control such as coin storage.

In addition, during this period, the voltage (d) gradually decreases as the loop current is disconnected, and the VDT19 has a hysteresis characteristic that makes it difficult to detect when the voltage (d) decreases to a lower value v, t than the predetermined value V. In order to return (, ) to rHJ, the output (f) changes to rHJ accordingly, and the output (b) of INV22 changes to rHJ only between rLJO, and TR-Q,
is turned on, the collector potential (h) is set to rLJ, and TR-
Q.

is also turned on to back up the power supply vDO by the capacitor C3.

However, as mentioned above, capacitor C6 has an extremely large capacity, and even after the output (C) becomes rLJ and the TR-Q switch is turned off, it retains a sufficient amount of charge.
Since capacitor C6 is the last to receive charge from capacitor C6, capacitor C6 holds sufficient charge and is ready for when the rig goes off-hook.

Therefore, depending on the relationship with the line resistance value, capacitor C2
Even if charging is delayed, initial charging is performed mainly by the charge held by the capacitor C6, and as soon as the voltage of the power supply vO rises quickly, control of the CNT7 against off-hook is immediately started.

However, it is also possible to use a plurality of each capacitor cap + C2 + 05. The same effect can be achieved even if other switching elements are used in place of Qa. In some cases, the capacitor cap, C6 and TR-Q etc. can also be omitted.

Also, as VDT19, a comparator or the like can be used, and INV24 to TR-Q can be set accordingly.

The delay time of the CNC 18 can be determined according to the conditions, and the configuration of the CNC 18 can be arbitrarily selected according to the situation, and the configuration shown in Fig. 2 can also be determined according to the operating conditions. Various modifications are possible.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, even if the charging of the capacitor by the loop current is delayed due to the relationship with the line resistance value, the initial charging by the charge held by a separate capacitor is delayed. Since the terminal voltage of the power supply capacitor rises quickly and the control section responds immediately to off-hook conditions, a remarkable effect can be obtained in various types of 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...TKO (telephone circuit),
7...CNT (control unit), 18...CNC (control circuit), 19...■π (1! Pressure detection circuit), 21
~25, 27...INV (inverter), 2
6... gate, Ll, L,... line terminal,
zD... Constant voltage diode, D-D ・
・ ・ ・Diode, C1 to C7 ・ ・ ・ ・l
4 Capacitor, Q engineering ~ Q5...TR () transistor)
, R engineering ~ R2o...Resistor. Patent applicant Tamura Electric Co., Ltd. Agent Masaki Yamakawa (2 people on TB Island) Figure 1 Figure 3

Claims (1)

[Claims] 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. a second capacitor having a large capacity that is charged by the loop current through a diode for blocking reverse current;
a voltage detection circuit that detects that the terminal voltage of the first capacitor reaches a predetermined value after off-hook; and a voltage detection circuit that is connected between the first and second capacitors and detects a 1. A power supply circuit for a telephone set, comprising: a switching element that is turned on until the occurrence of a switching element.