JPS6142018A - Constant current circuit - Google Patents

Abstract

PURPOSE:To reduce the power loss of a circuit to make it small-sized and reduce the variance for a partial trouble of redundant constitution by providing a current detecting circuit with the first winding and the second winding, whose number of turns is larger than that of the first winding, at least and providing a current limiting circuit in series to the second winding. CONSTITUTION:A control signal having a voltage proportional to the difference between a voltage Vd of the detection signal transmitted from a current detecting circuit 5 and a preliminarily determined reference voltage V0 for a value I10 of a current I1 is sent to a constant current source 3, and the transmission current I1 of the constant current source is so controlled that the voltage of the control signal is zero. When constant current circuits 2A and 2B are operated simultaneously, the operating point is the intersection between characteristics AD and BD, and voltages VA and VB are VL0/2 and they share equally the load if they have the same characteristic, and a current IL is IL0. As the result, the power loss for a resistance RP for taking partial charge of load is reduced; and a current limiting circuit 8 is added to limit the increase of a current I2 flowed to the resistance RP. If the current limiting circuit 8 is connected to the ground side when one output terminal is grouded, it is unnecessary to subject a winding WD2 to the high dielectric strength treatment, and a current detecting circuit where a reference current winding Ws is provided additionally may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a constant current R circuit, in particular, a constant current source having a constant current source each having an independent pressure current value controlled, and connecting a plurality of constant current sources in a series to supply a constant current Rt to a load. Regarding constant current circuits.

Figures 1) and 1(b) are block diagrams showing a configuration example of a conventional constant current circuit and an example of its use, respectively. The constant current circuit 1 controls the current flow 1t sent by the constant current source 3 to a predetermined value by the current detection circuit 4 and the control circuit 6, and supplies t current Lx, t to the load 7. . A magnetic amplifier (not shown) having a saturable reactor is used as the current detection circuit 4, and the current I sent out by the constant current source 3 is used.

After passing through the DC winding WD for current detection in the saturable reactor, the current is divided into a current I3 flowing to the load sharing resistor rLP and a current ■1 flowing toward the load 7. The current detection circuit 4 is an ampere turn N・If of the ■wave winding WD.
(However, N indicates the number of turns of the wave winding WD.) A detection signal of a voltage Vd proportional to the number of turns of the wave winding WD is generated and sent to the control circuit 6. Therefore, the voltage Vd of the detection signal is.

Vd = 5-・N-I wealth
・・・・・・・・・ (1)
It is expressed as the proportionality constant i, the expanded DC excitation ampere-turn/output voltage conversion ratio. The control circuit 6 is equipped with a comparison amplifier 61, and one of its pair of input terminals is applied with the voltage d of the detection signal sent from the current detection circuit 4, and the other is used for constant current control. A reference voltage vo serving as a reference is applied. This reference voltage V
The value of the work!・For.

■・＝、9−N・工１・・・・・・・・
... It is set so that the relationship (2) is satisfied. The control circuit 6 is.

A control signal with a voltage proportional to the difference between the voltage Vd and the reference voltage ■- is sent to the constant current source 3, so that the voltage of the control signal becomes zero, that is, the value of the current controller 1 becomes equal to I, ·. Controls the sending current generator 1 of the constant current source 3.

When supplying power using the constant current circuit 11 having such a configuration, a plurality of circuits are connected in series as shown in FIG. .In addition,
Diodes DA and 8 are for bypass when the constant current circuit 1 and IB are stopped, respectively. ), redundant configurations that operate simultaneously to improve reliability and load sharing. Both constant current ft circuits IA and IB have the same configuration as the same figure -), and each divides the voltages ■ and ■3 out of the voltage v1 of the load 7, and supplies the voltage t to the load 7.
Supply ItlL.

FIG. 2 is a characteristic diagram showing the operating characteristics when the connection shown in FIG. 1(b) is made. The horizontal axis shows the voltage vA111 shared by one constant current circuit, and the vertical axis shows the current IL supplied to the load 7.
The load 7 is longer than the minimum current required for operation m (not shown).

A constant voltage holding means is provided to maintain the voltage (1) at the operating voltage vLO. As is clear from FIG. 1+8).

is established, and further constant current control is performed.1. : I, , if this relationship is applied to the constant current circuit IAjC.

I, :I,. -7mu/ R, Hit... (4) This is illustrated in characteristic A).

The sending current of constant current R source 3 of constant current circuit IA is the specified value.

shows the output voltage V and output current IL characteristics when equal to
When constant current circuits IA and IB are operating simultaneously, V,=V,. -vA holds, this relational expression and equation (3)
If we apply this to the constant current ft@ path IB.

IL: IBQ + (vA-vLO)/H, 15)
This is fully shown in the diagram as characteristic B, where the output current of the constant current source 3 of the constant current R circuit IB is the specified value I. The operating point when the constant current circuit F and IB are operated simultaneously is 1 when the sending current of the constant current source 3 of both is equal to the respective specified value A.

and I, , given by the intersection of characteristics A and B, -IAO"180, then the voltage V.

and VB are both exactly half the voltage VLO, so that the constant current circuits I and IB share the load equally. Note that the electrician at this operating point. Ha, i! The low voltage RIm should be set higher than that.

Same #X of constant voltage ft circuits IA and IB! ! At the time of rotation, the outgoing current of both constant current sources 3 is constant current 15! Upper @ (ZAo + ∆) and lower limit (IBo - ∆I) of the control accuracy range
), the characteristics of both become characteristics A1 and BB, respectively. Along with this, the operating points are characteristics A and B.
1, a voltage variation ΔV of load sharing occurs, and the load sharing becomes uneven.

This voltage fluctuation ΔV is constant voltage [1111J accuracy b=ΔI
/I, using e.

ΔV=R,・ΔI=R,,−b・Single layer・
・・・・・・・・・ 0 expressed as (6)
Normally, it is impossible to reduce the control accuracy below a limit due to constraints from the accuracy and stability of the parts used. Therefore, when it is necessary to set the current factor 1 to a large value, the value of the resistor R must be made small in order to suppress the voltage fluctuation Δvl within the desired range. For example, in the analog transmission system using coaxial cables, the power supply current to the repeater is 50 to 100 mA3 degrees, whereas in the Amo digital transmission system using optical 7-iper, the power supply current to the repeater is orders of magnitude higher. There will be 1 or 2 people. In order to suppress the voltage fluctuation Δ■ in the latter case to the same extent as in the former case, a resistor R for load sharing is required.

must be lowered by an order of magnitude, but Fig. 1+at
t - As is clear from reference, the power W consumed by the resistance ratio is.

Since it is expressed as w=v/R, (7), if the resistance RP is set to a value one order of magnitude lower, the power consumption W increases by one order of magnitude. As a result.

As the external dimensions of the resistor R become larger, the heat dissipation cooling means also becomes larger in order to deal with the increased heat generation in the resistor R1, which necessitates a single constant current circuit and a larger IBt. Furthermore, if the value of the resistor R7 is lowered as described above, when a failure occurs in which one of the constant current circuits IA and IB stops operating, the amount of variation in the current flow that occurs will increase. When the constant current circuit IB stops operating, the first
When the diode D in figure (b) is in a conductive state, the force and constant current fi
Only 1A will share the voltage VLOt-. At this time, as shown in FIG. 2, the value of current IL is
1” Lower Luca, electric ff I, (D&motion IL.-IA,
=V, O/2R.

increases when the value of resistor R2 is lowered.

In this way, in a conventional constant current circuit, especially when the load current becomes large, the power loss in the load sharing resistor becomes large and the circuit becomes large. It has the disadvantage of large fluctuations.

An object of the present invention is to provide a constant current circuit which eliminates the above-mentioned drawbacks, can be made smaller by reducing the power loss in the load sharing resistor compared to the conventional one, and which has small load current fluctuations when a failure occurs in a part of the redundant configuration. There is a lot to offer.

・The direct circuit of the present invention includes a current detection circuit that detects the current at a predetermined point in one circuit, and controls the sending current so that the detected value converges to a predetermined value in response to a signal indicating the detected value of the current detection circuit. In a constant current FF circuit having a constant current source and a load sharing resistor.

The current detection circuit has at least first and second windings for current detection, and the number of turns of the second winding is set to be greater than the number of turns of the first winding.

The output voltage at of the constant current source - the first voltage flowing through the resistor
A second flow path that flows through the flow path and the first winding to an external load.
It has a connection metal that separates the flow into the flow path.

The first flow path includes a current limiting circuit that is connected in series with the second winding and the resistor and limits the current in the first flow path to a predetermined value or less.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a block diagram showing a first embodiment of the present invention. In the constant current circuit 2 shown in the figure, the current detection circuit 5 includes a resistor R in addition to a first DC winding WD1 for passing the current 11t flowing toward the load.

The second [fi winding WD
2t is provided, and a current limiting circuit 8t is connected in series to the resistance ratio P for load sharing. The current I is
A current flows toward the load through the first DC winding WD1 of the current detection circuit 5, and a resistor flows through the second DC winding WD2 and the current limiting circuit 8.

The current I flowing through is divided into two parts.

The voltage vd of the detection signal sent out by the current detection circuit 5 is the first
and the sum of ampere turns of the second [ff winding WD2 (
Nx・I, + N,・1) K proportional.

Vd=Jil(Nx I, +Nx4x) −・−
...(represented as 81. (However, Nx and N are the first and second DC windings WD1 and WD2, respectively.
1 indicates the DI current excitation ampere-turn/output voltage conversion ratio of the current detection circuit 5). ．． Against.

Vo = l−Nl ・Lo −・−・・(
9) A control signal of a voltage proportional to the difference from the stone reference voltage V is sent to the total constant current source 3, and the sending current L1t- of the constant current source 3 is increased so that the voltage of the control signal becomes zero. Control. As a result of this control, I ``It@-(sha)・工, ・・・・・・・・・
(1o) Quintuplicity is established. The current wire 1 branches into the current I and IL after passing through the first DC winding WDl, so that the current ft,
IL is.

It is expressed as

The fs4 diagram is a characteristic diagram showing the operation of the current limiting circuit 8. The horizontal axis indicates the voltage Vft between the terminals of the current limiting circuit 8,
The vertical axis shows the electric current fii flowing through the current limiting circuit 8. Voltage V
If the value of is below Vr, the operating characteristic is that the voltage fii is proportional to the voltage V], and when the value of the voltage Y rises to v, the voltage V
ti has an operating characteristic that limits the current to a constant value regardless of the value of the voltage V.

FIG. 5 is a characteristic diagram showing the operating performance of this embodiment.

The current limiting circuit 8 has the operating characteristics shown in FIG. 4, which shows the operating characteristics when two constant current circuits 2 are connected in series as shown in FIG. When applied to two people, and the winding resistances of the first and @2 current windings W and WD2 are very small i, the voltage drop is ignored, within the range where Is<lr holds.

When holds true and tI, = bow holds.

holds true, where r is the resistance value between the terminals of the current limiting circuit 8 at a voltage vK of v(v, expressed as r=YrAP.7tVc is the voltage V between the terminals of the current limiting circuit 8
VcztR indicates the value of the voltage ■ when becomes equal to
, +r)・import. Characteristic A is 1 equation (11)
This diagram illustrates the relationship between and (12), and the voltage VC
1, the operating voltage VLo of the load 7 and its half voltage V, o
/2. Similarly, the property Be
Equation (10) t is applied to the constant voltage circuit 2B as shown in the figure.

When two constant current circuits and 2B are operated simultaneously, the operating point is the intersection of characteristics AD and BD. When both have the same characteristics, '1 voltages vA and VB are both V L
With equal load sharing at O/2), electric 151EI becomes 11o. At this time, when both constant current sources 3 fluctuate to the upper and lower limits of the constant current control range, respectively (illustration of this characteristic fluctuation is omitted in Fig. 5).
, the associated load sharing voltage variation ΔV is.

RF + y ΔV= (-)・b・1st ・・・・・・・・・(1
3) It is expressed as bonha-sari. This equation (13) and the equation (
6) and refer to the entire equation (7), it is clear that −
In particular, when the voltage fluctuation ΔV is the same, the power loss in the resistors RP and r in this embodiment is equal to the resistance R in the conventional circuit.
The power loss in the IP is (Nr /Ns) times greater than the conventional one by increasing the number of turns N per turn and the total number of turns NK. Furthermore, the constant current circuit 2B stops operating,
When only two people share the load in a constant current circuit, the value of current I drops to IAL.

FIGS. 6(a) and 6(fb) are circuit diagrams showing examples of the configuration of the current limiting circuit 8, respectively. Figure 18) shows an example of using a constant ms diode CDt.The constant current diode CD is
It is a diode that utilizes the electric field effect of a semiconductor.If the voltage between the terminals is below the pinch-off voltage, the resistance between the terminals is approximately constant, and when the voltage between the terminals exceeds the pinch-off voltage, it exhibits substantially constant current characteristics. . That is, the constant current diode CD has operating characteristics substantially as shown in FIG.
The pinch-off voltage corresponds to the voltage VPK. Same figure tb
) has one end connected to the emitter of the transistor TR, a Zener diode ZD connected between the other end and the base of the resistor TR, and a resistor R connected between the base and collector.
It has a configuration in which the goose is connected. When the current I, is small and the voltage across the Zener diode ZD is less than the Zener voltage, the voltage across this circuit is approximately proportional to the current I, and therefore the resistance between the terminals is approximately constant, and the current , increases and the voltage across the Zener diode reaches the Zener voltage, it exhibits a substantially constant current characteristic, that is, this circuit also has substantially the operating characteristic shown in FIG.
The Zener voltage of the Zener diode ZD approximately corresponds to the voltage m. The circuit shown in FIG. 4A has the advantage of being compact, and the circuit shown in FIG.

As explained above, the second DC winding WDz is added to the current detection circuit 5, and the number of turns is N.

is set larger than the number of turns NK of the first DC winding WDl, and the number of turns NK of the first and second DC windings WD1 and WD is
By controlling the current in response to the ampere turns of 2, it is possible to reduce the power loss in the load sharing resistor R, and by adding a current limiting circuit 8, the current 2 flowing through the resistor R1 can be reduced.
By limiting the increase in , it is possible to reduce load current fluctuations when transitioning from simultaneous operation to unilateral operation.

FIG. 7 is a schematic diagram showing a second embodiment of the present invention. The circuit of this embodiment is the same as the circuit of the first embodiment in which one output terminal is grounded and the current limiting circuit 8 is connected to the ground side. Obviously, the operating principle is the same as the first embodiment, but the second i! shown in FIG. Since the voltage applied to the fi winding W0 is lower in this embodiment, ! f
There is no need to apply high voltage resistance treatment to the f winding WD2 as in conventional methods.

There is an advantage that the number of manufacturing steps for the current detection circuit 5 can be reduced compared to the conventional method.

FIG. 8 is a diagram showing a third embodiment of the present invention. In the circuit of this embodiment, a current detection circuit is additionally provided with a reference current winding W8 for passing a reference current Is. The reference current winding W3, which performs constant current control according to No. 15, has the sum of ampere turns (Nt) of the first and second DC windings W91 and Wo.

A reference current, t-, is supplied from the constant current source 13 in a direction that cancels the +N + It). When the number of turns of the reference current winding W3 is N, the current detection circuit 15 calculates the composite value of ampere turns (Nt ・I, +N, ・I, −N, ・
A detection signal of a voltage vd proportional to I, )K is generated and sent to the control circuit 6. In this embodiment, the constant current control reference voltage V of the control circuit 6 is set to zero, and the control circuit 6 sends a control signal with a voltage proportional to the voltage vd to the constant current source 3. is zero, that is, IL = (NS/Nt) ・I, -(''/Nt
) ・Is (14) The constant current source 3 is controlled so as to send out a current I such that the following relationship holds true. This is because equation (14) is an equation in which Il· in equation (10) is replaced by the term t (Ns/Nt )·I.

The same effect can be obtained by performing constant current control similar to that of the first embodiment.

It is clear that the same effects as in each of the embodiments can be obtained even when three or more of the circuits of the first to third embodiments described above are connected in series and operated.

As is clear from the above description, 1) the present invention has a constant current circuit which has less power loss in the load sharing resistor than the conventional one, and which has small load current fluctuations when a partial fault occurs when operating multiple units in series; -It has the effect of being able to appear in the dark.

[Brief explanation of drawings]

Figures 1(a) and (b) show the conventional constant '#LR, respectively.
, a block diagram showing a circuit configuration example and an example of use, FIG. 2 is a characteristic diagram showing the operation of a conventional constant current circuit, and FIG. 3. ! 7 and 8 are professional diagrams showing the complete embodiment of the present invention, Figures 4 and @5 are characteristic diagrams showing the operation of the embodiment of the present invention, and Figure 6 +a+ and (bl are All are circuit diagrams showing embodiments of the present invention. 1, IA, IB, 2A, 2B... constant current circuit;
3.13... Constant current source, 4,5.15...
...Current detection circuit, 6...Control circuit, 7...
...Load, 8...Current limit circuit, WD, WD
1. WD□...llff winding. Ws...Reference current winding, 几. , R1, 几1...
····resistance. CD・・・・・・Constant current diode, TR・・・・・・
transistor. ZD...Zener diode. (2B) (b) Early 2nd eye 3 birds Q vP Voltage V Half 4 Figure 0 Vc μ0 Voltage VA - Figure 5 (d) (b) Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] A current detection circuit that detects a current at a predetermined point in a circuit, and a sending current that is controlled so that the detected value converges to a predetermined value in response to a signal indicating a detected value of the current detection circuit. In a constant current circuit having a constant current source and a resistor for load sharing, the current detection circuit has at least first and second windings for current detection, and the second winding has a second winding. The number of turns is set to be greater than the number of turns of the first winding, and the sending current of the constant current source is passed through the first flow path to the resistor and the first winding to an external load. The current flow in the first flow path is connected in series to the second winding and the resistor, and the current in the first flow path is controlled to a predetermined level. A constant current circuit characterized by comprising a current limiting circuit that limits the current to a value below.