JPH1118415A - Current balance circuit of parallel operation power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a current detector for taking the current balance of a parallel operation power unit, and increase the applicability. SOLUTION: This circuit is composed of resistors 11 and 12 which detect currents, being inserted into the junction where DC-DC converters 2 and 3 are connected in parallel, a differential voltage amplifier 13 which receives differential voltage within both ends of resistors 11 and 12, a level shift circuit 14 which applies the output voltage of the differential voltage amplifier 13 to the Vref of a level shift DC-DC converter 2, a lamp which receives the output voltage of the differential voltage amplifier 13 and discriminates between the positive and negative directions of the input voltage and shows the control direction, and an indicator 15 which produces an alarm at the limit of control. Then, the current balance is taken by varying the Vref by the differential voltage between the detected voltages V1 and V2 of the resistors 11 and 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current balance circuit for a parallel operation power supply device, and more particularly, to a case where two power supply devices are connected in parallel so as to detect respective output currents and positively balance output currents. And a current balance circuit for controlling the current balance.

[0002]

2. Description of the Related Art Conventionally, two power supplies are connected in parallel in a redundant configuration in order to increase the reliability of the power supplies. However, output currents become uneven due to variations in the output voltage of each power supply. In such a case, a full load may be applied to one power supply device. For this reason, there is a problem that the life and reliability of the loaded power supply device are reduced due to an increase in the internal temperature.

In order to avoid this problem, in order to balance the output current of each power supply, for example, Japanese Patent Laid-Open No. 61-29316
A technique as disclosed in Japanese Patent Application Laid-Open No. 8-108 is known.

FIG. 3 is a circuit diagram showing this prior art example. In FIG. 3, the input and output of the converter 61 and the converter 66 are connected in parallel. A current detector 62 and a current detector 67 for detecting respective output currents are connected. The voltage comparison circuit 68 includes the current detector 62 and the current detector 6
7, and amplifies and outputs the difference voltage. The control unit of the converter 61 is an error amplifier 6
5, a PWM circuit 64 and a drive circuit 63.

Next, the operation will be described. The converter 61 and the converter 66 always output voltages V1 and V2 proportional to the output current by the current detector 62 and the current detector 67, and input them to the voltage comparison circuit 68. Voltage comparison circuit 6
8 compares the difference voltage between V1 and V2 and outputs the difference voltage to the output voltage V3.
Is applied to the reference voltage terminal Vref of the error amplifier 65. The current detectors 62 and 67 are converters 61 and 6
6 is detected by converting each input-side switching current into a voltage by a current transformer.

The converter 61 and the converter 66 are initially set to a state in which the output currents are balanced by using the output voltage adjustment function in the PWM circuit. When the output current of the converter 66 is increased and the output current of the converter 66 is reduced to an unbalanced state, the current detector 6
The detection voltages V1 and V2 of the second and the second 67 become V1> V2, and the output voltage V3 of the voltage comparison circuit 68 changes in a decreasing direction.
The error amplifier 65 determines that the output voltage has relatively increased since Vref has decreased, and the output voltage is controlled to decrease by the PWM 64 and the control circuit of the drive circuit 63. As a result, the output current decreases and the output current is reduced. It returns to the state of. In this way, the control by current detection
The current balance is maintained positively.

[0007]

As described above, in the prior art, the current balance is maintained by control by current detection. However, since this current detection detects a current inside the converter, for example, an input-side switching current. The current detector is complicated by using a current transformer. In addition, since this current detector must be provided in advance inside the converter, there is a problem that this technique cannot be easily used when existing converters are connected in parallel.

[0008]

A current balance circuit of a parallel operation power supply device according to the present invention comprises a conversion circuit for switching a DC input voltage to convert the voltage and an error amplifier for detecting an error voltage of an output voltage of the conversion circuit. A power supply device having a control circuit for controlling the switching pulse width of the conversion circuit with the output voltage of the error amplifier to stabilize the output voltage.
Two resistors for current detection inserted at one end in common at the output side connection points connected in parallel with each other, and a positive / negative bidirectional differential voltage generated between the other ends of the two resistors. And a differential voltage amplifier for amplifying and level-shifting the amplified voltage and applying the amplified voltage to the reference voltage of the error amplifier of one of the power supply devices.

A conversion circuit for switching a DC input voltage to convert the voltage, an error amplifier for detecting an error voltage of an output voltage of the conversion circuit, and a switching pulse width of the conversion circuit controlled by an output voltage of the error amplifier. And two current detection resistors, each having one end inserted in common at its output side connection point, in which two power supply units having a control circuit for stabilizing the output voltage are connected in parallel. A first differential voltage amplifier for amplifying the positive voltage of the voltage across the other end of the resistor and applying the output voltage to the reference voltage of the malfunction amplifier of one of the power supply devices; and a negative voltage of the voltage. And a second differential voltage amplifier for amplifying the output voltage and applying the output voltage to the reference voltage of the error amplifier of the other power supply device.

[0010] Also, a display may be provided for inputting the output voltage of the differential voltage amplifier, identifying the positive / negative polarity of this voltage, and recognizing the control direction.

In addition, there is provided a display for inputting the output voltage of the first and second differential voltage amplifiers and visually recognizing the power supply device controlled by the first or second differential voltage amplifier. May be.

Further, the display may generate an alarm when the input voltage becomes a predetermined value or more.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, two DC-
The DC converters 2 and 3 are connected in parallel on the input and output sides, respectively, and the current balance circuit 1 of the present invention is inserted into the connection point on the output side. 4 is supplied evenly.

The DC-DC converter 2 converts a DC input voltage into a voltage and performs a voltage conversion, an error amplifier 23 which detects an error voltage of an output voltage of the conversion circuit 21, and a conversion circuit using the output voltage of the error amplifier 23. A control circuit 22 for controlling the switching pulse width of the circuit 21 to stabilize the output voltage. DC-DC converter 3
Also has the same configuration.

The current balance circuit 1 has two DC-
Two current detecting resistors 1 each having one end inserted in common at an output connection point where a DC converter is connected in parallel.
1, 12 and a differential voltage amplifier 13 for amplifying a positive-negative differential voltage generated between the other ends of the two resistors 11, 12.
And a level shift circuit 14 for level-shifting the output voltage of the difference voltage amplifier 13 and applying it to the reference voltage Vref of the DC-DC converter 2, and inputting the output voltage of the amplifier 13 to identify and control the positive / negative polarity of this voltage. The display unit 15 displays a direction and issues an alarm at the control limit at the same time.

Next, the operation of FIG. 1 will be described. DC-
Since the DC converters 2 and 3 are ordinary sketching regulators, the description is omitted. The resistors 11 and 12 for detecting the output currents of the DC-DC converters 2 and 3 have low resistance values that drop by about 100 mV at the rated output current in order to suppress a decrease in efficiency.

Initially, the DC-DC converters 2 and 3 are controlled, for example, so that the output currents are balanced.
The input voltage or Vref of the side error amplifier 23 is adjusted. The output voltage is adjusted by this input voltage or Vr
ef is changed (not shown). When the output current of the DC-DC converter 2 increases for some reason from the current balanced state and the output current of the DC-DC converter 3 decreases by this amount, for example,
The detection voltages V1 and V2 of the resistors 11 and 12 satisfy V1> V2, and the difference voltage is amplified by the difference voltage amplifier 13. In this case, the amplified output becomes a negative voltage, and the level shift circuit 14 shifts the voltage so as to match the voltage of Vref, and operates to lower this Vref. The error amplifier 23 determines that the output voltage has relatively increased since Vref has decreased, and transmits the output to the control circuit 22. Since the control circuit 22 controls the output voltage in the lowering direction, the output current decreases and the original current balance is restored.

The output voltage of the differential voltage amplifier 13 is input to the display unit 15. In this case, since the output voltage is in the negative direction, it indicates that the output voltage of the DC-DC converter 2 has been controlled to decrease. Turn on the lamp. On the other hand, when the input voltage is the positive voltage, a lamp indicating that the control has been performed in the upward direction is turned on. Further, when the input voltage exceeds a predetermined control limit, it is determined that an abnormality has occurred and an alarm is generated by blinking the lamp or the like.

This display lamp provides maintenance convenience. For example, if the lamp for controlling the lowering direction is turned on, the maintenance person adjusts Vref in the direction of lowering the output voltage and turns off the lamp. The current is balanced. That is, if vref is adjusted in a state where both lamps are turned off, it is possible to easily reset the initial state in which the current is balanced.

Next, another embodiment will be described with reference to FIG. FIG. 2 shows a configuration in which the configuration of the differential voltage amplifier of the current balance circuit 1 of FIG. 1 is changed and two differential voltage amplifiers are used, but the operation stability is further improved.

In FIG. 2, the current balance circuit 5
Current detection resistors 51 and 52 inserted at one end in common at output connection points where the C-DC converters 2 and 3 are connected in parallel, and the voltage between the other ends of the resistors 51 and 52, respectively. Amplify the positive voltage and output DC-DC
Differential voltage amplifier 53 applied to Vref of converter 2
A differential voltage amplifier 54 for amplifying the negative voltage and applying the output voltage to Vref of the DC-DC converter 3;
A display lamp for inputting the output voltages of the differential voltage amplifiers 53 and 54 to visually recognize the DC-DC converter controlled by the input differential voltage amplifier, and a display unit 55 for issuing an alarm when the control limit is exceeded. It is composed of

Next, the operation of FIG. 2 will be described. As in FIG. 1, the difference voltage between the resistors 51 and 52 is input to difference voltage amplifiers 53 and 54. For example, when the output current of the DC-DC converter 2 increases, the detection voltages V1, V
2 becomes V1> V2, and the difference voltage amplifier 53 outputs a negative direction voltage which is amplified and inverted by using this as a positive direction voltage.
The Vref of the C-DC converter 2 is lowered, and this output current is reduced to operate to balance the current. On the other hand, D
When the output current of the C-DC converter 3 increases, the detection voltage becomes V1 <V2 and the difference voltage is amplified by the differential voltage amplifier 54 to output a negative voltage by setting this as a negative voltage, and Vref of the DC-DC converter 3 is lowered. An operation is performed to reduce the output current and balance the current.

The display 55 has a differential voltage amplifier 53,
When the output voltage of the differential amplifier 53 is input and the input from the differential amplifier 53 is received, the lamp indicating the controlled DC-DC converter 2 is turned on, and the input from the differential voltage amplifier 54 is received. At the time, a lamp indicating the DC-DC converter 3 on the controlled side is turned on. Further, when the input voltage exceeds a predetermined limit value, it is determined that there is an abnormality, and the display lamp blinks to generate an alarm.

[0024]

As described above, in the current balance circuit of the present invention, since the current detection is performed by the resistor inserted at the connection point on the output side, the detector is simplified, and the current balance circuit can be applied to the existing power supply device. Has an effect that it can be easily added and used.

In order to balance the current, the power supply device in the controlled direction or the controlled side is displayed as a lamp, and at the same time, an alarm is generated at the control limit. This has the effect of improving maintainability such as automatic detection of failure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

[Explanation of symbols]

 1,5 Current balance circuit 2,3 DC-DC converter 4 Load 11,12,51,52 Resistor 13,53,54 Difference voltage amplifier 15,55 Display unit 14 Level shift circuit

Claims (5)

[Claims] 1. A conversion circuit for switching a DC input voltage to convert a voltage, an error amplifier for detecting an error voltage of an output voltage of the conversion circuit, and a switching pulse width of the conversion circuit controlled by an output voltage of the error amplifier. And two current detection resistors, each having one end inserted in common at its output side connection point, in which two power supply units having a control circuit for stabilizing the output voltage are connected in parallel. And a differential voltage amplifier for amplifying and level-shifting a differential voltage between the positive and negative bidirectional voltages generated between the other ends of the resistors and applying the resulting voltage to a reference voltage of an error amplifier of one of the power supply devices. Power supply current balance circuit. 2. A conversion circuit for switching a DC input voltage to perform voltage conversion, an error amplifier for detecting an error voltage of an output voltage of the conversion circuit, and a switching pulse width of the conversion circuit controlled by an output voltage of the error amplifier. And two current detection resistors, each having one end inserted in common at its output side connection point, in which two power supply units having a control circuit for stabilizing the output voltage are connected in parallel. A first differential voltage amplifier for amplifying the positive voltage of the voltage across the other end of the resistor and applying the output voltage to the reference voltage of the malfunction amplifier of one of the power supply devices; and a negative voltage of the voltage. And a second differential voltage amplifier for amplifying the output voltage and applying the output voltage to the reference voltage of the error amplifier of the other power supply device. 3. The parallel operation power supply device according to claim 1, further comprising a display for inputting the output voltage of the differential voltage amplifier, identifying the polarity of the voltage, and recognizing a control direction. Current balance circuit. 4. An indicator for inputting output voltages of the first and second differential voltage amplifiers and visually recognizing the power supply device controlled by the first or second differential voltage amplifier. 3. The current balance circuit for a parallel operation power supply device according to claim 2, wherein: 5. The display device according to claim 3, wherein the display generates an alarm when the input voltage becomes higher than a predetermined value.
Alternatively, a current balance circuit of the parallel operation power supply device according to 4.