JPS6142017A - Constant current circuit - Google Patents

Abstract

PURPOSE:To reduce the power loss and the variance of a load current for a partial trouble of redundant constitution by providing a current detecting circuit with the first and the second windings at least and providing a current limiting circuit connected in series to the second qinding and a resistance. CONSTITUTION:In a constant current circuit 2, a current detecting circuit 5 is provided with not only the first DC winding WD1 through which a transmission current I1 of a constant current source 3 passes but also the second DC winding WD2 through which a current I2 shunts to a resistance RP passes, and a current limiting circuit 8 is connected in series to the resistance RP for taking partial charge of a load. A control circuit 6 sends a control signal, which has a voltage proportional to the difference between a voltage Vd of the signal transmitted from the current detecting circuit and a preliminarily determined reference voltage V0 for a value I10 of the current I1, to the constant current source 3, and the current I1 is so controlled that the voltage of the control signal is zero. When several constant current circuits, for example, two equal circuits 2A and 2B are operated simultaneously, the operating point is the intersection between characteristics A0 and B0, and they share equally the load, and a current IL is IL0, and the power loss for the resistance RP and gamma is reduced. Further, the increase of the current I2 is limited by the current limiting circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant current circuit, in particular, a constant current circuit which has a constant current source whose current value is controlled independently, and which is connected in series to supply a constant current tube to a load. Concerning current circuits.

FIG. 1 [aJ and lbl are 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 11 sent out by the constant current source 3 to the current detection circuit 4 and the control circuit 6 to a predetermined value, and supplies the current ILl to the load 7. As the current detection circuit 4, a magnetic amplifier (
The electric current RIt sent out by the constant current source 3 flows through the current winding wire WD for detecting the current in the saturable reactor, and then flows to the load sharing resistor IL. Current I! and a current I flowing toward the load 7. The current detection circuit 4 generates a detection signal of a voltage vd proportional to the ampere turns N·L+ of the current winding WD (where N indicates the number of turns of the DC winding WD), and sends this to the control circuit 6. send to

Therefore, the voltage vd of the detection signal is.

Vd=9・N・Work 1 ・・・・・・・・・
+1), where the proportionality constant 1 is the DC excitation ampere-turn/output voltage conversion ratio. The control circuit 6 is equipped with a comparison amplifier 61i, and one of its pair of input terminals receives the voltage vd of the detection signal sent from the current detection circuit 4.
is applied, and the other is a reference voltage v that serves as a reference for constant current control.
A letter has been applied. This reference voltage is the value of the predetermined voltage tlt11.

Against.

v,==Ji+-1'J・工!・ ・・・・
...... 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 d and the reference voltage V is sent to the constant IIEfi source 3) so that the voltage of the control signal becomes zero, that is, the value of the current generator 1 becomes equal to I,. The output current I of the constant current source 3 is fully controlled.

When supplying power using the constant current circuit 1 having such a configuration, a plurality of circuits are connected in series as shown in FIG. Note that the diodes DA and RI are for bypass when the constant current circuit and IB are stopped, respectively), and a redundant configuration in which they are operated simultaneously] is intended to improve reliability and share the load. The constant current circuit 1 and IB both have the same configuration as Ta) in the same figure, and each share the voltage vA and 8 of the voltage V of the load 7, and
Supply L.

FIG. 2 is a characteristic diagram showing operating characteristics when the connection shown in FIG. 2 μ and FIG. 1(b) is made. The horizontal axis shows the voltage V shared by the constant current circuit IA, and the vertical axis shows the current supplied to the load 7. If the load 7 has a current of at least the minimum current required for operation (not shown).

A constant voltage holding means is provided to maintain the voltage vL at the operating voltage vLO. As can be seen by referring to Figure 1 (aJ?).

■=Ehie3=Construction-v/Rp...(3) is established, and further by constant current control! y L = It. If this relationship is applied to the constant current circuit IA.

I, = I□. -V□/RP ・・・・・・・・・
... (4) holds true. This is illustrated in Figure 9, where characteristic A6 is the characteristic, and the output current of the constant current source 3 of one constant current circuit is the specified value. ■ Output voltage when equal to , vs. output current .

When constant current circuits IA and IB are operating at the same time, 8=vL0-vA holds true.

If this relational expression and equation (3) are applied to constant current circuit IB.

I, == I,. +(VA-V,.)/RP...
...mark... (5) holds true. This is illustrated in the characteristic Bo.

The characteristics are shown when the sending current of the constant current source 3 of the constant current circuit IB is equal to the specified value I8°. Constant current circuit IA workshop IB
The operating point during simultaneous operation is 0, when the output currents of both constant current sources 3 are at their respective specified values.

In the case of the manufactured IBo, it is supported by the intersection of the characteristics Ao and B, and if IAo = IBo, the voltages E and VB are both exactly half of the voltage vL0, and the constant current circuits IA and IB are The load will be shared equally. Note that electric fiI at this operating point. is set to be equal to or higher than the minimum current.

When the constant current circuits IA and IB are operated simultaneously, when the sending current of the constant current source 3 of both constant currents fluctuates to the upper limit (I, .+Δmin.) and lower limit (IB. The characteristics of both are characteristic A and 8 ri, respectively. Along with this, the operating point moves to the intersection of the characteristics AI and B1, causing a variation ΔV in the load sharing voltage, resulting in uneven load sharing. This voltage fluctuation Δ■ is constant current control accuracy b=ΔI/It.

Using.

1V=R・j I=R−b・La
--・” 161?
? It is expressed as Normally, it is impossible to reduce the value below the limit due to constraints in terms of control accuracy bH, accuracy and stability of parts used. Therefore, when it is necessary to set the current I,e large, the value ft of the resistor B must be made smaller in order to suppress the pressure variation Δv within the desired range. For example, in an analog transmission system using a coaxial cable, the power supply to the repeater 'tR is 50 to 1
On the other hand, in the digital transmission system using optical fiber, the power supply current to the repeater is about 1 to 2 A, which is an order of magnitude higher than that. 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.

It has to be seven orders of magnitude lower. However, Fig. 1(a)
't-As is clear from reference, the power W consumed by the resistor Rp is.

w=v/to ・・・・・・・・・(7)
Therefore, if the resistance RPf is set to a knee-digit low value, its power consumption W increases by one order of magnitude. As a result.

As the external dimensions of the resistor become larger, the resistance R increases.

The rounded heat dissipation cooling means to cope with the increase in the amount of heat generated in the circuit must also be enlarged, and the constant flow circuits I and IB must be enlarged. Furthermore, if the value of the resistor RP is made low as described above, if a failure occurs in which one of the constant tff1 circuits IA and IB stops operating, the amount of variation in the current flow that occurs will increase. For example, when the constant current circuit IB stops operating, the diode D shown in FIG.

At this time.

As shown in FIG. 2, the current IL decreases at the value UIALt, but the fluctuation of the current IL is ``LO-AL'' vLO/2 liters.

increases when the value of resistor R1 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 is large, making the circuit large, and a part of the redundant configuration may fail, causing the load current t! It has the disadvantage of a long tt shift.

It is an object of the present invention to provide a constant current circuit which eliminates the above disadvantages, can be made smaller by reducing 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. Our goal is to provide the following.

The circuit of the present invention includes a current detection circuit that detects *fIL' at a predetermined location in one circuit, and a current detection circuit that detects *fIL' at a predetermined location in one circuit, and a current detection circuit that responds to a signal indicating the detection value of the ``? In a constant current circuit having a constant current source whose sending current is controlled and a resistor for load sharing.

The current detection circuit has at least a first and a second winding for current detection, and a first current flowing through the resistor after the sending current of the constant current source passes through the first winding. A 20th flow path that flows into the flow path and an external load has a connection for branching, and the @1 flow path is connected in series to the second winding and the resistor, and the first flow path is connected in series to the second winding and the resistor. Electric power +5! t-
This circuit includes a current limiting circuit that limits the current 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 the first embodiment of the present invention. In the constant current circuit 2 shown in the figure, the current detection circuit 5 includes a first NR winding W for passing the sending current i of the constant current source 3.
In addition to D1, a second Ii, ft winding W for passing the current I, which is shunted to the resistor R,.

The current limiting circuit 8t is connected in series with the resistor R1 for load sharing. Current I.

1 is the first DC winding W of the current detection circuit 5. 1, the current IL flowing towards the load and the second
The current I and fI are divided into two.

The voltage vd of the detection signal sent out by the current detection circuit 5 is the first
and is proportional to the sum of ampere turns (Nl·I, +N,·It) of the second DC windings WDX and WD2.

Vd = ,L(Nx ・It +N weight ・I
t)--(81. (However, Nl and N! indicate the number of turns of Ml and the second DC windings WD1 and WD2, respectively, and g is the current sensing ampere-turn output of the current detection circuit 5. ) control circuit 6 indicating the voltage conversion ratio
is the voltage ■d of this detection signal and the value I! of the predetermined electric current. . Against.

Ve =I-Nt・Its---(9
A control signal of a voltage proportional to the difference from the reference voltage V. expressed as 1 is sent to the constant current source 3, and the output power fItI of the constant current source 3 is fully controlled so that the voltage of the control signal becomes zero. As a result of this control, I,=I,. -(N!/Nl)・Work 3・・・・・・ (
10) holds true. Den 11 I 1 is the first Rin-ryu Maki?
1 AWD 1 all through, 9, and the current is divided into I and .

1Efil, ha.

・・・・・・・・・(11) It is expressed as

FIG. 4 is a characteristic diagram showing the operation of the current limiting circuit 8.

The horizontal axis shows the voltage vt between the terminals of the current limiting circuit 8, and the vertical axis shows the current i flowing through the current limiting circuit 8t.If the value of the voltage V is less than or equal to Yp, the voltage Ri and the voltage V are proportional to each other. When the value of voltage V exceeds vPt-, the current i
is an operating characteristic that limits the current to a constant value regardless of the value of voltage.

FIG. 5 is a characteristic diagram showing one EP1 production.

The operating characteristics are shown when two constant current circuits 2 are connected in two measurement columns as shown in FIG. Since the current limiting circuit 8 has the operating characteristics shown in FIG.
Applied to humans, and the second [flow winding wire W. 20 Since the winding resistance is very small, if we ignore its voltage drop, Ix<'p
In the range where it holds true.

1, :IA. -(1+Luo)・vA/(90r)・・・・
...... (12) When I z = 19 bottoms out, Ni II, = IAO-(''N, '・Vc/ (R=
, + r ) (13) holds true. However, r is the resistance value between the terminals of the current limiting circuit 8 at a voltage V of v(v, expressed as T=P/IP. Also, vc is the resistance value between the terminals of the current limiting circuit 8 at a voltage V of Y, Indicates the value of voltage vA when they become equal V,'
It is expressed as = (R, +r)·i.

Characteristic A is a demonstration of the relationship of Equations (12) and (13), and is expressed as voltage Vct - operating voltage of load 7 "LO
and half the voltage V. /2. Similarly, the diagram is applied to the characteristic B/equation (11) t constant voltage circuit 2B.

When two constant current circuits and 2B are operated simultaneously, the operating point is the intersection of characteristics A and B. When both have the same characteristics, voltage ■ and VB are both V L
(1/2 equal load sharing.

Electronic fLIL is engineering. become. At this time, when both constant current sources 3 fluctuate to the upper limit L and lower limit of the constant current control range, respectively (<Illustration of this characteristic fluctuation is omitted in Fig. 5),
The variation ΔV in the load sharing voltage associated with this is.

It is expressed as This equation (14) and the equation (
6), and it is clear from equation (7) that when the voltage fluctuation Δ■ is the same, the power loss in the resistor RP and γ of this embodiment is equal to that of the conventional circuit. The power loss in the resistor R is reduced by a factor of N+/(Ni+Nx).

Furthermore, the constant current circuit 2B stops operating, and the constant current circuit 2AI
When the load is shared by f and ke, the value of current LL decreases to IAL, but with the straight line characteristic shown by the broken line ao as in the prior art, the current LL increases to IaL. Opening 1a) shows an example of using a constant current diode CDi, a constant +lfL diode CD1-j, and a diode using semiconductor field effect gold. The resistance between the terminals is almost constant,
In addition, when the voltage between the terminals exceeds the pinch-off voltage, substantially constant current characteristics are exhibited. That is, the constant ta diode CD has operating characteristics substantially as shown in FIG. 4, and its pinch-off voltage corresponds to the voltage V. In circuit C of the same figure (1), one end is connected to the emitter of the transistor TR with a resistivity R, a neutral diode ZD is connected between the other end and the base, and a resistor R2 is connected between the base and the collector. It has the following configuration. 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 exhibits a nearly constant resistance across the terminals, and the voltage +51EI When the voltage increases and the voltage across the Zener diode reaches the Zener voltage, it exhibits substantially constant current characteristics. In other words, this circuit also has *qualitative operating characteristics as shown in Figure 4,
The Zener voltage of the Zener diode ZD is approximately equal to the voltage applied. The circuit shown in FIG. 1A has the advantage that it can be made compact, and the circuit shown in FIG. 1B has the advantage that there is a large degree of freedom in setting the current limiting characteristic.

As explained above, the current detection circuit 5 includes the second DC winding WD2t-additionally the first and second DC windings WD1.
By controlling the current in response to the ampere turns of W and 2, the power loss in the load sharing resistor R1 can be reduced, and by adding a current limiting circuit 8, the resistor RpH'cR
By limiting the increase in the electric current RIt, it is possible to reduce load current fluctuations when transitioning from simultaneous operation to unilateral operation.

FIG. 7 is a block diagram showing a second embodiment of the present invention.The circuit of this embodiment is the same as the circuit of the first embodiment, but when one output terminal is grounded, the 14L flow limiting circuit 81: Connect it to the ground side. Obviously, the operating principle is the same as the first embodiment, but the second DC winding Wl) shown in FIG.
Since the voltage applied to □ is lower in this example,
There is an advantage that the DC winding aWD 2 does not need to be subjected to high withstand voltage treatment as in the conventional case, and the number of man-hours for manufacturing the current detection circuit 5 can be reduced compared to the conventional method.

FIG. 8 is a diagram showing a third embodiment 2 of the present invention. In the circuit of this embodiment, the reference current winding W, which performs constant current control by the additionally provided current detection circuit 15, includes a first A reference current I is supplied from a constant current source 13 in a direction that cancels 2+1 (Nt·11+N,·I) of ampere turns of the second DC windings WD1 and WD2. Reference current winding W.

Assuming that the number of turns is N, the current detection circuit 15 calculates the composite value of ampere turns (N+-It+Nt・I, -N3・I,
), and sends it to the control circuit 6. In this embodiment, the constant current control reference voltage (■) of the control circuit 6 is generated. is set to zero, and the control circuit 6 sends a control signal with a voltage proportional to the voltage V to the constant current source 3 so that the voltage of the control signal becomes zero, that is.

L = (NB/Nt) ・IB - (Ns/Nt)4
x・・・・・・・・・・・・・・・ The constant current source 3 is controlled so as to send out the current Ist'' such that the relationship of (15) holds.Equation (15) is expressed as 1 expression (10) Part 1.

This is because the term t(N, /Nt)・k is replaced in the equation.

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 explanation, the present invention has a constant current circuit which has less power loss in load sharing resistors than the conventional one, and which has small load current fluctuations when a partial failure occurs when multiple resistors are operated in series. It is very effective if it can be realized.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams showing a configuration example and usage example of a conventional constant current circuit, respectively. Figure 2 is a characteristic diagram showing the operation of a conventional constant current circuit, and Figure 3. . Figures 7 and 8 are diagrams showing the 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 ta+ and ( Both of b) are circuit diagrams of Embodiment 1j 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, W, WD
□, WD2...DC winding, W. ...Reference current winding, R1, R1,...
...Resistance, CD... Constant current diode, T
IN...Transistor, ZD...Zener diode. Agent Patent Attorney Susumu Uchihara 1 (b) #3 Figure Ovr Voltage V Wase Voltage VA - Kotobuki S Figure (α) (b) Mu 6
Concave

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 current detection circuit has at least first and second windings for current detection, and has a connection such that after passing through the first winding, the flow is split into a first flow path flowing to the resistor and a second flow path flowing to an external load, and the first flow path includes A constant current circuit comprising: a current limiting circuit connected in series to the second winding and the resistor to limit the current in the first flow path to a predetermined value or less.