JPS60197161A - Constant current device - Google Patents

Abstract

PURPOSE:To supply an accurate constant current by commonly controlling the time ratio of a plurality of resonance type constant current converters so that the output currents of the entire device become constant, thereby preventing the output current from decreasing upon increasing of the load. CONSTITUTION:A plurality of resonance type constant current converters CONV are connected in series, and a current is supplied through a common current detector 6 to a load 9. The converters CONV have inverters 1, resonators 2, rectifying and smoothing circuits 3, and voltage/frequency converters 4 for controlling the operating frequencies of the inverters 1. The detector 6 detects the output current Iout of the entire device, compares it with a reference value by the controller CONT to control the converter 4 through a current/voltage converter 10. Thus, the inverters 1 are controlled by the common controller CONT, and the time ratio of the converters are controlled so as to become the prescribed constant current.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a single-leg current device, and in particular, to a one-leg current device that supplies a constant current to a load such as a relay amplifier by connecting a plurality of resonant converters in series. This invention relates to improvements in constant current devices.

In conventional analog carrier communication systems, a saturable reactor controlled constant current converter is generally used as a remote power supply device for supplying current to repeaters. This is a constant current converter that uses a saturable reactor in a constrained magnetized state and keeps the output current constant by controlling the firing angle of the saturable reactor, and the loss of saturable reactor that operates with large amplitude AC. Due to the switching loss of the inverter transistor, its efficiency is limited to about 70%. The output current is about 60mA to 160mA, and the maximum output voltage is about 7KV and is used as a constant current device.

The output current of remote power supply devices for digital carrier communication systems is 500 mA to 2.0 mA because the load repeater amplifiers are highly functional and the system is redundant.
A, the output voltage can be up to 15 KV, and the output power of the device is more than an order of magnitude higher than in analog carrier communication systems. For this reason, there has been a push to increase the output and efficiency of converters that use 416 power supply devices, and in recent years,
A constant current device using a resonant constant current converter having an efficiency of 80% or more has been developed. In the resonant constant current converter, since the collector current of the inverter transistor is a sine wave, switching loss is eliminated, high efficiency is possible, and the device is miniaturized.

On the other hand, when using multiple constant current converters connected in series to the load for maintainability and redundancy,
It is necessary to stabilize load sharing among multiple converters. For this reason, as shown in Fig. 1, a plurality of resonant constant current converters CON V□ to C0NV n are connected in series to the load, and each resonant constant current converter has 0NVI.
A constant current device is used in which a load sharing resistor 7 and a diode D are connected in parallel to each output section of -CONV n.

Each resonant constant current converter C0NVs to C0NV n is an inverter circuit 1 that manually converts direct current into alternating current and outputs it.
, a resonant circuit 2 that manually inputs the output of the inverter circuit l to a rectifier/smoothing circuit 3, a rectifier/smoothing circuit 3 that rectifies and smoothes the alternating current input via the resonant circuit 2,
A current detector 6 detects the output current of the smoothing circuit 3, outputs a voltage corresponding to the output current, and inputs it to the control circuit 5. The voltage manually inputted from the current detector 6 is compared with a reference voltage S.

a control circuit 5 that outputs a voltage Vc according to the difference; and a voltage-frequency conversion circuit 4 that converts and outputs the control voltage VC output from the control circuit 5 into a corresponding frequency to control the switching frequency of the inverter circuit l. A resistor 7 and a diode D for load sharing are connected in parallel to the output portions of the respective circuits. The diode D is connected to bypass a resonant constant current converter that has stopped due to a failure or the like and to continue supplying current to the load by another resonant constant current converter.

Next, the operation of each resonant type constant current fan will be explained. The inverter circuit 1 operates at the control frequency supplied from the voltage-frequency conversion circuit 4, and converts the DC human power E into an AC output at the control frequency. The AC output of the inverter circuit 1 is rectified and
The smoothing circuit 3 is manually powered. The resonant circuit 2 is a series resonant circuit consisting of a choke coil L and a capacitor C, and its resonant frequency is f res. Operating frequency f of inverter circuit l
When the ratio of aw and f res, f H/f res, is the duty ratio δ, the AC power input to the rectifier red smoothing circuit 3 depends on the duty ratio δ, and the output of the rectifier red smoother circuit 3 in an uncontrolled state The characteristics are shown in FIG.

In other words, when the duty ratio δ is 1, the impedance of the resonant circuit 2 is 0, the output impedance of the rectifier/smoothing circuit 3 is low, and has almost constant voltage characteristics, and as the duty ratio δ becomes smaller, the output impedance becomes higher. , and when the zero time ratio δ, which becomes saturated at a small current value, is 0.5 or less, the output impedance becomes a substantially constant finite value.

Therefore, the output current can be controlled by changing the hour ratio δ.

The current detector 6 detects the output current Ipf of the rectifier smoothing circuit 3, outputs a voltage proportional to the output current tpr, and supplies it to the control circuit 5. The control circuit 5 converts the input voltage into a reference voltage S. Compare and amplify the control voltage signal ■c and output the voltage -
It is supplied to the frequency conversion circuit 4. Voltage-frequency conversion circuit 4
converts the control voltage Vc' into a corresponding frequency to control the operating frequency fsw of the inverter circuit l. That is, the duty ratio δ is controlled so that the output current Ipf of the resonant constant current converter is constant. Therefore, each of the resonant constant current converters co*vt to C0NVn outputs a constant current, and in the controlled state, the output impedance thereof becomes extremely high.

As it is, multiple resonant constant current converters I/C0NV
, ~C0NV n are connected in series, if the output current of some resonant constant current converters fluctuates (within constant current control accuracy), the load sharing will be disrupted, and some resonant constant current converters/ An excessive load of 1 force will be applied overnight. To prevent this, each resonant constant current converter C0N
A resistor 7 for load sharing is connected in parallel to each output section of Vt to C0NVn.

When the resistance value of the resistor 7 for load sharing is Rpf, the output impedance of each resonant constant current converter C0NV becomes a finite value Rpf, making it possible to stabilize load sharing.

Therefore, the output impedance of the entire device in which n resonant constant current converters (-) are connected in series is nφRpf, and the output current vs. output voltage characteristics are as shown in FIG. increase, in other words the output voltage v1
As the output current increases, the output current 1 decreases, and the constant current characteristic deteriorates to 1/1. That is, when the load voltage is vL, the load current decreases by ΔI and becomes ΔI.

The amount of decrease Δ in the load current is expressed as ΔI=VL/nRpf. This decrease Δ flows through the load sharing resistor 7 connected to the respective outputs of the resonant constant current converters - C0NV, ~C0NVn, and thereby the power loss Wr = VL''/n 'Produces Rpf.

Due to this loss, the efficiency of conventional constant current devices decreases, and they also have the disadvantage of being bulky to take measures for heat dissipation.

In addition, multiple resonant constant current converters C0NV, ~C0
It is not economical because NV n includes a control circuit 5 and a current detector 6, respectively.Furthermore, the reference voltage S of each control circuit 5 is
It is necessary to adjust the output current by adjusting the
It takes a considerable amount of time to adjust the output current of the entire device to a predetermined constant current value.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional drawbacks, to reduce power loss without connecting a load sharing resistor to a plurality of series-connected resonant type constant current converters, and to The current converter does not have a control circuit or current detector, and outputs a constant current through common control, which prevents deterioration of the constant current characteristics due to increased load and makes the device more compact.

It is an object of the present invention to provide a constant current device that can achieve high efficiency and high precision, and can also easily adjust the output current in a short time.

Configuration of the Invention The constant current device of the present invention includes an inverter circuit that converts and outputs DC input to AC, a resonant circuit connected to the output of the inverter circuit, and a rectifier that rectifies the output of the inverter circuit that is input through the resonant circuit. a rectifier/smoothing circuit that smoothes and outputs the signal, and a voltage-frequency conversion circuit that converts and outputs a control voltage signal supplied from the current-voltage conversion circuit to a corresponding frequency to control the operating frequency of the inverter circuit. A plurality of resonant constant current converters are connected in series, and a current detector is inserted in series between the plurality of resonant constant current converters and the load, and the output of the current detector is set as a reference voltage. a control circuit that compares and amplifies the control current and outputs a control current; and a control circuit that converts the control current output from the control circuit into a control voltage and supplies the current to each voltage-frequency conversion circuit of the plurality of resonant constant current converters. - a voltage conversion circuit, wherein the plurality of resonant constant current converters are commonly controlled by the control circuit and the current-voltage conversion circuit so that the detected value of the current detector is constant. do.

Embodiments of the Invention Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a block diagram showing a first embodiment of the present invention. In other words, multiple resonant constant current converters C0NV
I' to GONV n' are connected in series and a current is supplied to the load 9 through a common current detector 6. and,
Each resonant constant current converter GONV,'~GONVn
' are the inverter circuit l, the resonant circuit 2, and
It includes a rectifier/smoothing circuit 3 and a voltage-frequency conversion circuit 4 for controlling the operating frequency of the inverter circuit 1. The voltage-frequency conversion circuit 4 is a current-voltage conversion circuit 10 described later.
The output frequency is controlled by Therefore, each resonant type constant current converter does not have a built-in control circuit and current detector for controlling the voltage-frequency conversion circuit 4 as in the conventional example shown in FIG. A diode D is connected to each output part of the constant current converters C0NV1' to C0NVn'.

This is for use as a power bus when the resonant constant current converter is stopped, and no resistor for load sharing is connected as in the conventional case.

The current detector 6 detects the output current of the entire device,
A voltage proportional to the output current is output and input to the control circuit C0NT. The control circuit C0NT compares and amplifies the input voltage with a reference voltage S using a built-in comparison amplifier A,
The output of comparison amplifier A is connected to transistor T via resistor R1.
Enter it into the base of H. The emitter of the transistor TH is grounded through the resistor R2, and the collector is a current-voltage conversion circuit! Connect to the negative pole of power supply E through the input winding of
The positive terminal of power supply E is grounded. Therefore, a control current 1c corresponding to the difference between the detection voltage of the current detector 6 and the reference voltage S flows from the control circuit C0NT into the current-voltage conversion circuit IO. The current-voltage conversion circuit IO converts the control current Ic into a voltage and outputs a control voltage Vc, which is supplied to each voltage-frequency conversion circuit 4 of the plurality of resonant constant current converters C0NV1' to C0NVn'. do. The current-voltage conversion circuit IO includes a magnetic amplifier using a saturable reactor,
Alternatively, a current-voltage converter using a photocoupler or the like can be used.

As described above, each resonant constant current converter voltage-frequency conversion circuit 4 controls the operating frequency of the inverter circuit 1 with a frequency corresponding to the control voltage Vc output from the current-voltage conversion circuit 1O. That is, in this embodiment, a plurality of resonant constant current converters C0NV,'~C0N
The operating frequency of each inverter circuit 1 of Vn' is determined by the common control circuit C0NT and current-voltage conversion circuit 1.
0, and the duty ratio δ of each resonant constant current converter is controlled so that the output current of the entire device becomes a predetermined constant current. Therefore, the output impedance of this device has a very high value, and has the effect of preventing the conventional phenomenon in which the output current decreases as the load voltage increases.

On the other hand, the output characteristics of each resonant constant current converter of this device are the same as those shown in FIG. That is, it has an output impedance of a certain finite value. Therefore, this output impedance provides the same effect as a conventional load sharing resistor, and the load sharing is balanced by the output impedance. This output impedance changes depending on the duty ratio δ, but if the resonant frequency of the resonant circuit 2 and the conversion ratio of the voltage-frequency conversion circuit 4 of each resonant constant current converter are set equal, it can be controlled by a common control voltage Vc. The duty ratio δ of each resonant constant current converter becomes equal,
Therefore, the output impedance becomes equal, and the load is shared evenly. In other words, the load of each resonant type constant current converter can be shared equally without connecting a resistor for load sharing as in the conventional case.The output voltage Vpf of each resonant type constant current converter is Overall output voltage V
, is 1/n. Note that in the range where the duty ratio δ is approximately 0.5 or less, the output impedance of the resonant constant current converter is a nearly constant finite value (the slopes are parallel in Figure 2). Change range is θ~0.5
For stable operation, it is desirable to have the following conditions.

This embodiment does not use a resistor for load sharing as in the conventional case, so power consumption corresponding to the power loss is reduced and efficiency is improved. Further, there is no need to take measures against the heat generation of the load sharing resistor, and the device can be downsized. In addition, the output impedance of the entire device is extremely high, which prevents a decrease in output current due to an increase in load, making it possible to obtain extremely accurate constant current characteristics. Furthermore, since a plurality of co-circular constant current converters are commonly controlled by the control circuit C0NT and the current-voltage conversion circuit 1O, the number of parts is reduced compared to the prior art, which is economical. Furthermore, the output current of this device is adjusted by adjusting the reference voltage S of the control circuit C0NT, which eliminates the need to adjust the load while equalizing the load sharing with each resonant layer constant current converter as in the past. Ru. Therefore, the time required to adjust the output current can be significantly reduced.

In addition, multiple resonant layer constant current converters C0NV□ ′
~ When one of C0NVn' fails and the resonant layer constant current converter is removed from the equipment in order to replace it with a good one, it is bypassed by diode D connected in parallel to its output, and the other normal Constant current can be continuously supplied to the load using a resonant layer constant current converter.

FIG. 5 is a block diagram showing a second embodiment of the invention. In this case, a power supply e insulated from the ground is inserted in series with the collector circuit of the transistor TR of the control circuit C0NT shown in FIG. 4, and the current-voltage conversion circuit 12 has one end connected to the ground and the other end connected to the ground. It is constituted by a resistor R connected to the positive terminal of the power supply e. Others are the same as the embodiment shown in FIG. impedance r
l, and the resistance value r2 of the resistor H is rz((r.

If it is set so that the control voltage Vc becomes approximately Icm
r, and the voltage is proportional to the control current Ic. This control voltage Vc is supplied to the voltage-frequency conversion circuit 4 of each resonant layer constant current converter, and each resonant layer constant current converter is commonly controlled by the control circuit C0NT.
Supply constant current to the load. The current-voltage conversion circuit 12 is composed only of a resistor R, and the power supply e of the control circuit C0NT is rectified and smoothed by adding a winding to the oscillator (Royer oscillator, Jensen oscillator, etc.) for the power supply path of the comparison amplifier A. It can be configured by adding circuits.

Therefore, this embodiment is more economical than the first embodiment and can provide similar functions and effects.

FIG. 6 is a block diagram showing a third embodiment of the present invention. In this case, a plurality of current detectors 68 to 6 are connected in series, and their respective outputs are connected to a plurality of control circuits CQNT.
I to C0NT m, and the outputs of the plurality of control circuits C0NT are connected in parallel to control the control current Icl
0 individual control circuits C that cause the control current Ic added with ~Ice to flow into the current-voltage conversion circuit 12
The configuration of 0NT is the same as the second embodiment shown in FIG. 5, and the current-voltage conversion circuit 12 is constituted by a resistor H. The current-voltage conversion circuit 12 converts the combined control current I
c is converted into a voltage and a control voltage Vc is output to control the duty ratio δ of each resonant layer constant current converter C0NV. Therefore, ■ckiIc・``2 = (Ic 1 +Ic 2+...・-+Icta) e
It becomes rz. If one control circuit fails, the remaining control circuits can supply control current to keep the output current at a predetermined value. That is, by redundant design, it is possible to reduce the failure rate of the control system to an extremely small value of several FIT or less. Regarding other effects,
This is similar to the first and second embodiments described above. In addition,
Since the control circuits of the first and second embodiments both output a control current, if a plurality of control circuits are provided and their outputs are connected in parallel, it is easy to obtain the same result as shown in FIG. (It is not easy to combine multiple control voltages.)

Effects of the Invention As described above, the present invention provides a current detector that connects a plurality of resonant layer constant current converters in series to supply current to a load and detects the output current of the entire device; a control circuit that compares and amplifies the output voltage of the converter with a reference voltage and outputs a control current; and a voltage-frequency conversion circuit that converts and outputs the control current output from the control circuit into a control voltage for the plurality of resonant layer constant current converters. and a current-to-voltage conversion circuit to supply the device, so that the output current of the entire device is a constant value.
Since the duty ratio of the plurality of resonant layer constant current converters is configured to be commonly controlled, the load increases.

This prevents the phenomenon that the output current decreases due to the increase in the current, and can supply a highly accurate constant current. Moreover, instead of connecting a resistor for load sharing to the output of each resonant constant current converter as in the past, the structure uses the unique output impedance characteristics of the resonant constant current converter to equalize the load sharing. Therefore, it is possible to reduce the loss that conventionally occurred in the load sharing resistor, reduce power consumption, and provide a highly efficient and compact constant current device that does not require measures against heat generation.

Furthermore, since the present invention has a configuration in which the duty ratio of a plurality of resonant constant current converters is commonly controlled, each common constant current converter needs to have a built-in current detector and control circuit for control. Therefore, it is possible to reduce the number of parts as a whole, which is economical. One thing to note is that this device allows for easy adjustment of the output current, eliminating the need for the complicated work of adjusting each individual resonant constant current converter while equalizing the load sharing among multiple resonant constant current converters. It can be adjusted in a single time.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional constant current device, Fig. 2 is a diagram showing the output characteristics of each resonant constant current converter of the above conventional example in an uncontrolled state, and Fig. 3 is a diagram showing the control of the above conventional example. 4 to 6 are block diagrams showing first to third implementations +l+ of the present invention, respectively. In the figure, l: inverter circuit, 2: resonant circuit, 3:
Rectification-smoothing circuit, 4: Voltage-frequency conversion circuit, 5: Control circuit, 6.6ri~6■: Current detector, 7: Resistor for load sharing, 9: Load, lO:' Heart current-voltage conversion Circuit, 12:
Current-voltage conversion circuit, C0NVI to C0NV n,
C0NV1'~C0NVn': Resonant type constant current converter, (:ONT, C0NTl~C0NT+
s: control circuit, E, e: power supply, D: diode. Applicant NEC Co., Ltd. Agent Patent Attorney Toshisuke Sumita Figure 1 Figure 2

Claims (1)

[Claims] An inverter circuit that converts DC input into AC output:
A resonant circuit connected to the output of the inverter circuit, a rectification/smoothing circuit that rectifies and smoothes the output of the inverter circuit input through the resonant circuit, and outputs the resultant output, and control supplied from a current-voltage conversion circuit described later. A plurality of resonant constant current converters each having a voltage-frequency conversion circuit that converts and outputs a voltage signal to a corresponding frequency to control the operating frequency of the inverter circuit are connected in series, and the plurality of resonant constant current converters are connected in series. A current detector inserted in series between a constant current converter and a load, a control circuit that compares and amplifies the output of the current detector with a reference voltage and outputs a control current, and a control output from the control circuit. a current-voltage conversion circuit that converts and outputs a current into a control voltage and supplies it to each voltage-frequency conversion circuit of the plurality of resonant constant current converters, the plurality of resonant constant current converters A constant current device characterized in that it is commonly controlled by the control circuit and the current-voltage conversion circuit so that the detected value of the detector is constant.