JPS58156255A - Current control circuit - Google Patents

Abstract

PURPOSE:To control the load current, by detecting the current of a variable resistance network and then controlling the resistance value of said network with the detected value of current. CONSTITUTION:Either one of transistors TRQ0 and Q1 is turned on under the control of a control circuit CTL, and a load current IL is supplied to a load resistance RL. A photocoupler PH1 or PH2 detects the current IL which flows via the TRQ0 or Q1 and produces a voltage drop proportional to the current IL at a resistance R9. A converting circuit ADC converts the terminal voltage of the R9 into a digital form and supplies it to a processor PR. The PR processes the working of the RL2 of a realy RL0 on the basis of the supplied digital value. The working relay short-circuiting resistances R0-R2 and maintains the current IL at a prescribed level.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical field of the invention The present invention relates to 1i! c current control circuit, and a current control circuit that sometimes supplies a current t-11 to a load.

(b) Technical background For example, in a telegraph exchange, ar
The current value supplied to the terminal is a constant value (for example, ±20 milliampere) determined by the standard of the terminal to be connected to the terminal.
need to be maintained. Various line resistance values t-W
It is necessary to provide a current control circuit that can increase the fIL flow value supplied to each wL telegraph terminal accommodated by the telegraph mK to a predetermined value K11l (e) Prior art and problems summary 111ii In single company telegraph exchange FIG. 4 is a diagram showing a conventional current control tjl path o-4st. In FIG. 1, the line resistance of the communication circuit and the internal resistance of the telegraph terminal are collectively shown as a load resistance RL. Only one of the transistors and Q is a conductive layer based on the control circuit CTLO control, and a double current type load tf is applied to the load resistor RL.
iILt supplies 0 Even if the load resistance RL varies widely depending on the communication distance, etc., from 1 to 8 (for example, from several hundred ohms to 1,000 ohms), the load current IL (absolute 111)
As a current control circuit for maintaining K at the predetermined value (±20 milliamperes, for example), a variable resistance network consisting of resistors 2 to 3 connected in series and short-circuiting terminals T and T s is provided. Since the resistance value of the variable resistance network is changed by changing the connection between the terminals T and T, the load current ILt can be changed by appropriately connecting the terminals T to T. t to a predetermined value
It is possible to insert J4. Note that if the load resistance RL is large,
If a ground fault occurs in the communication line and the load resistance RL suddenly drops while the terminals To and T are connected, the load current LL will suddenly increase to 0 or \, and the transistor Qo or In order to prevent Ql from being damaged, terminals T. to T.
, it is necessary to set the resistance RcO value, which will not be short-circuited, to a certain value or more. However, in the conventional current 1111 control circuit, it is necessary to adjust the connection between the terminals To and T1t to the load resistor RL4 in order to supply the load current fiL' to a predetermined voltage, which requires a lot of effort. Yes ◎Resistance R
There is a drawback that the load resistance RLC) fF capacity range is limited because of e.

Figure 2 shows conventional current control 1 that eliminates the above-mentioned drawbacks.
In FIG. 2, which is a diagram showing another example of the gl path,
A current control circuit mainly consisting of transistors Qm and Q8% and constant voltage diodes 2 and Zs is provided, and a variable resistance network that requires connection between terminals is excluded. o Transistors Qs and Ql are: The conduction states of transistors Q and Q are controlled by control #Ql-jlcTL in the same way as in Fig. j11.

], only one side has a conductive embroidery, the load resistance R
A double current type load current lLt is supplied to L. Note that the transistor Q in the conductive state or (M>Base degree) is
The constant voltage diode 2@M9 is limited by zI. Therefore, as the load IEmIL increases, the voltage drop across the resistive island or R increases, and the transistor Qmt becomes Q,
(The voltage between D-base and E-emitter decreases, which acts to prevent an increase in load power.

Therefore, by appropriately selecting resistors R1 and R4, the load voltage can be reduced to 15! In a conventional current control circuit in which IL is masochistically maintained at the predetermined value, the transistor Q! Since Qs and Qs are operated in an unsaturated region, power consumption increases, and various heat dissipation measures are required to maintain the temperature rise below the total eave height value. In addition, the transistor Q
! and Q are required to have sufficient proof strength, which impedes miniaturization and economicalization of the current control circuit.

(a) Purpose of the invention The purpose of the present invention is to eliminate the drawbacks of the conventional current control circuit as described above, without expending much effort or expense in adjusting the load current, and at the same time impairing miniaturization and economicalization. The goal is to realize a current control circuit that never fails.

(・)Structure of the InventionThis object is to provide a variable resistance circuit network that adjusts the voltage supplied to the load, and a current detection circuit that detects the current value of the current, and uses the output of the current detection 1gl path. This is achieved by controlling the resistance value of the variable resistance network. This is a diagram showing a current path according to 0. Note that the same reference numerals indicate the same objects throughout the figures. In FIG. 3, I, consisting of resistors B to R and RP, connected in parallel with relays RL to RL and RLPo image points rl to rl 2 and rip, respectively.
2T variable resistance network, photocouplers PHt and PH as the voltage Igl detection path, and a conversion circuit ADC and processor P that operate the relays R1, .
0 Photocaps PH5i or PH equipped with a current control circuit consisting of R and multiple Drinos (DV)
1, the control circuit CTLK detects the load current iL flowing through the transistor Qo or Qtt', only one of which is in a conductive state, as in FIG. 0 conversion circuit AD generated in
C digitally converts the terminal voltage of the resistor Rs and inputs it to the processor PR. The processor 12-PR controls the operation of the relays RLo to RLt according to a predetermined logic 11 based on the input terminal voltage (digital value) of the resistor Re. 1II1 Relay RL o to R
LI is resistance R・no! Rt is short-circuited, and the resistance value of the variable resistance network is controlled so that the load current IL is maintained at the predetermined value.During operation, a ground fault or the like occurs in the communication line, and the load current L suddenly increases. In this case, the processor PR immediately drives the relay RLp and inserts the resistor Rpt-* into the charged current supply path to limit the load 4fi11- to a value sufficiently lower than the predetermined value. However, when the load current IL suddenly decreases, it is clear from the above explanation that the resistance value of the variable resistor IgllII network is equal to the load current fi I L ,
(Based on the D detection result, the gross set tPR connects the relay KL.
By driving p1 to RL, i accordingly, the load current Ill
Since the load (aIL) is automatically adjusted so that it is maintained at the predetermined value, no effort is required to adjust the load (aIL), and transistors made in the unsaturated region are not used. , heat dissipation measures, etc. are not required.Furthermore, the load m1EIL during communication circuits is limited to a sufficiently low value, preventing loss of value of transistors Q- and Ql, and unnecessary power consumption. By the way, the fan 3 figure is just a picture of one dog of the present invention, for example, variable resistance IgllI & rope 4
Although the structure shown in the figure is 6), it is difficult to reduce the size of the structure, and many other modifications can be considered, but the effects of the present invention remain the same in either case. Also, the resistance value of the variable resistance - road rope is relay R
It is not limited to what is nim* by 1n to RLm, and many O transformations can be considered in Rin, but in any case, the effect of the 4h* invention does not change.0 Furthermore, the subject of the present invention is
Needless to say, it is not limited to telegraph exchanges. (2) Effect of output @O According to the superposition gAK, it does not require any effort to increase the load current, and it can be made smaller and more economical. An undamaged current control circuit is achieved.

[Brief explanation of the drawing]

The first WA is a diagram showing an example of a conventional current control circuit, and the second WA is a diagram showing an example of a conventional current control circuit.
Diagram showing another example of the EFi current control circuit, iris 8
The figure shows a current control circuit according to an embodiment of the present invention. In the figure, CTL is a control circuit, Q. to Qs are transistors, 2. and zl are constant voltage diodes, pn. and Pug is the hot cube 2, MuDC is the conversion circuit, PR is the P9 sensor, Dv is the driver, RL@ to [,1 and RLp are relays, R1 to R-1 & and fLp are resistors, RL is load resistance, IL is Load current t, shown 0'78
1 Figure V 2nd Leap 3rd ■

Claims (1)

[Claims] a variable resistance circuit network that adjusts the current supplied to the load; a current detection circuit that detects the current of the current;
A current 111I even circuit is provided, and the resistance value of the variable resistance network is controlled by the output of the current detection circuit.