JPH02104160A - Power supply system converting circuit - Google Patents

Abstract

PURPOSE:To suppress a current value when a subscriber's loop resistance is small by connecting the base side of an n-type Darlington transistor(TR) to the negative side of a Zener diode, connecting the base side of a p-type Darlington TR to the positive side of a Zener diode and controlling the upper limit value of a calling current value flowing between respective terminals. CONSTITUTION:In a circuit connected between subscriber's circuit side connecting terminals A, B and terminal equipment side connecting terminals A', B', an n-type Darlington TR 1, a Zener diode 3, a low resistor 5, and a high resistor 7 are connected between the terminals A' and A and a p-type Darlington TR 2, a Zener diode 4, a low resistor 6, and a high resistor 8 are connected between the terminals B' and B. The base side of the TR 1 is connected to the negative side of the diode 3, the base side of the TR 2 is connected to the positive side of the diode 4 and the upper limit of a calling current value flowing between the terminals B, B' and A', A is controlled. Thus, a loop current at the time of low loop resistance can be restricted.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a power supply method conversion circuit connected between a constant resistance power supply type subscriber circuit and a terminal device, and the purpose is to enable the accommodation of terminal devices with limited communication current. Connecting terminals A and B on the subscriber circuit side and connecting terminal A' on the terminal device side.
, B', an N-type Darlington transistor, Zener diode, low resistance, and high resistance are installed between A' and A terminals, and a P-type Darlington transistor and Zener diode are installed between B' and B&J terminals. A low resistance and a high resistance are set, and the base side of the N-type Darlington transistor is connected to the negative side of the Zener diode, and the P
Connect the base side of the type Darlington transistor to the positive side of the Zener diode, I3. It is configured to control the upper limit of the communication current value flowing between the Ll' terminal and between the A' and A terminals.

[Industrial application field]

The present invention relates to a power supply system conversion circuit connected between a constant resistance power supply type subscriber circuit and terminal equipment.

Due to recent advances in semiconductors, the functions of subscriber circuits that connect telephone exchange lines to telephone exchanges have greatly increased and become smaller. The subscriber circuit is composed of various circuits such as power supply monitoring, signal transmission, 2vA/4M+ conversion, etc., and the component parts are transistors,
Since various electronic components such as rectifiers are used, the current value of the power supply circuit that supplies communication current to terminal devices such as telephones also fluctuates as line resistance changes.

Furthermore, with the development of new services, terminal equipment such as telephones connected to subscriber circuits has become required to have various additional functions, and specifications have also come to be established for the current values for terminal equipment. In particular, when a terminal device such as a telephone is used to send an image communication signal to an electronic exchange, it has become necessary to limit the current in the terminal device.

[Conventional technology]

FIG. 4 shows power supply characteristics in a conventional constant resistance subscriber circuit without a power supply system conversion circuit. FIG. 4(a) shows a loop current measuring circuit, and FIG. 4(b) shows the loop current characteristics with respect to loop resistance.

In the figure, the relationship between the loop resistance R of the subscriber line connected to the subscriber power supply circuit P and the loop current ■ is such that as the loop resistance R becomes smaller, the loop current 1 increases rapidly, and the loop resistance R becomes 2. When the current value is Ω, the loop current value I is 20mA, and when the loop resistance R is 0Ω, the loop current is 100mA.
mA or more, and the resistance current characteristic becomes curved. Therefore, in terminal equipment that requires current limitation, such as a smartphone telephone for transmitting image communication signals, the specification standard is an upper limit current of 45rn8, so by lowering the loop current value when the loop resistance becomes small, the resistance current characteristic It is necessary to make it a straight line and create a constant current power supply circuit.

[Problem to be solved by the invention]

As described above, in conventional subscriber circuits that do not use a power supply method conversion circuit, the current value increases rapidly as the subscriber loop resistance decreases, and terminal devices that require constant current power supply by suppressing the upper limit current value cannot be applied to

An object of the present invention is to connect a power supply system conversion circuit to a subscriber circuit to suppress the current value when the subscriber loop resistance is small, thereby realizing a subscriber circuit having constant current power supply characteristics.

[Means to solve the problem]

FIG. 1 shows a basic configuration diagram of a power feeding method conversion circuit according to the present invention. In the figure, 11 indicates subscriber circuit side connection terminals A and B.
1 is an N-type Darlington transistor, 2 is a P-type Darlington transistor, 3.4 is a Zener diode, and 5゜6 is a low resistance , 7.8 indicates high resistance. Note that 12 represents a subscriber circuit, and 13 represents a terminal device.

The base side of the N-type Darlington transistor 1 is connected to the negative side of the Zener diode 3, and the base side of the P-type Darlington transistor 2 is connected to the positive side of the Zener diode. 11. Between the B' terminal and the A' and A terminals. The configuration is configured to control the upper limit of the communication current value that flows between the two terminals.

[Effect]

” When the subscriber circuit 12 is connected to the A and B terminals of the power supply system conversion circuit 11 and the terminal device 13 is connected to the A' and B' terminals to form a power supply circuit, the power supply from the subscriber circuit 12 and B, B', A' by the loop of the terminal device 13.

A loop current flows along the route to.

When the loop current is small, almost no current flows from the negative side to the positive side of Zener diodes 3 and 4, and the loop current flows through the B terminal, resistor 6, transistor 2, B' terminal, terminal equipment 13,
It flows through the path of A° terminal, transistor 1, resistor 5, and A terminal. Next, when the loop current increases, the voltage across resistor 6 and resistor 5 increases, Zener diodes 4 and 3 reach the Zener voltage, and current begins to flow from the negative side to the positive side of the diodes. At this time, the loop current is B
Terminal, resistor 6, transistor 2, B° terminal, terminal equipment 1
3. Route of A' terminal, transistor 1, and resistor 5A terminal■
Then, the current flows through the path (3) of the B terminal, the Zener diode 4, the resistor 8, the B'terminal terminal device 13, the A°terminal, the 1° resistor 7, the Zener diode 3, and the A terminal. However, as the current flows through the path ■, the base potential of transistors 2 and 1 is restricted, and the current between the emitter and collector of the P-type transistor 2 and the current between the collector and emitter of the N-type transistor l no longer flows, and the current flows through the path ■. The flowing current becomes 0. Therefore, by the operation of the Zener diodes 4 and 3, only the path (2) is inserted into which the high resistance of the resistors 7 and 8 is inserted, and the increase in the loop current is limited. In this way, by connecting the power supply system conversion circuit 11, the loop current of the subscriber circuit can be suppressed within a certain range.

〔Example〕

A circuit configuration diagram of an embodiment of the present invention is shown in FIG.

In the figure, 1 is an N-type Darlington transistor Tri
, 2 is a P-type Darlington transistor Tr2.3.4
are Zener diodes Di, D2.5. 6 is low resistance R
1, R2, 7, and 8 are high resistances R3, R4, 9, and 10 are capacitors CI and C2. 8. A 148V power supply from the subscriber circuit is connected to the B terminal, and the loop current I is measured by connecting the A' and B' terminals with a loop resistor R. Loop resistance R and loop current! Figure 3 shows the characteristics. Note that low resistance R1 and R2 are 100
Ω, high resistance R3 and R4 are IKΩ, Zener diode D
The polarity of I and C2 is changed by a Zener voltage of 3.6 cm, and the capacitors CI and C2 are 2 μF and are used to pass audio signals.

If the loop resistance R is large according to the circuit diagram in Figure 2,
The subscriber current is earth-subscriber circuit 12-B-R2-Tr2
-8'-R-8' -Tri -R1-A-Subscriber circuit 12- (-48V) flows through the path (■), and when the loop resistance R is small, the subscriber current is
- B-C2-124-8"-R-A'-R3-DI-
A-subscriber circuit 12-(-48ν) flows through the path .

According to the characteristic diagram in Figure 3, if the loop resistance is 2 to Ω, the loop current will be 16 mA, if the loop resistance is 1 to Ω, the loop current will be 22 mA, and if the loop resistance is 0 Ω, the loop current will be 37 mA. The maximum current value at low loop resistance is limited, and the characteristic curve is also approximately linear.

By adding a capacitor for passing audio signals, it is possible to prevent the standard level diagram from deteriorating and to pass even the frequency band signals of the bushphone.

〔Effect of the invention〕

By using the power supply method conversion circuit of the present invention, it is possible to limit the loop current when the loop resistance is small, and it is possible to limit the loop current when the loop resistance is small, and to convert the addition circuit that performs constant resistance power supply to terminal equipment that requires constant current power supply, and the current value It can be applied to terminal equipment that requires restrictions.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 is a loop resistance/loop current characteristic diagram of the embodiment, and Fig. 4 is a loop ti( An anti/loop current characteristic diagram is shown. In the figure, 1 is an N-type Darlington transistor, 2 is a P-type Darlington transistor, 3.4 is a Zener diode, 5.6 is a low resistance, 7.8 is a high resistance, and 9.10 1 is a capacitor, 11 is a power supply system conversion circuit, 12 is a subscriber circuit, and 13 is a terminal device.

Claims (1)

[Claims] Subscriber circuit side connection terminals A and B and terminal equipment side connection terminal A'
, B', an N-type Darlington transistor (1), a Zener diode (3), a low resistance (5), and a high resistance (7) are provided between the A' and A terminals.
', P-type Darlington transistor (2), Zener diode (4), low resistance (6) and high resistance (8) are connected between the B terminals.
), and the base side of the N-type Darlington transistor (1) is connected to the negative side of the Zener diode (3),
The base side of the P-type Darlington transistor (2) is connected to the positive side of the Zener diode (4), and the upper limit of the communication current flowing between the B and B' terminals and between the A' and A terminals is controlled. Power feeding method conversion circuit.