JP2008109736A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system having a plurality of converters connected in parallel, in which responsiveness in control and stability of operations are improved. <P>SOLUTION: A current detecting circuit 15a is provided in a constant voltage control converter 20, and a current detecting circuit 15b and an error amplification circuit 13 are provided in a current control converter 21. The current control convertor 21 controls currents so that an output current of the constant voltage control converter 20 matches an output current of itself (the current control converter 21). With this configuration, a set voltage of the constant voltage control converter 20 is supplied to a load 14, and the output currents of both the converters are made equal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power supply system in which a plurality of converters are connected in parallel to supply power to one load.

  2. Description of the Related Art Conventionally, for the purpose of improving the reliability of a power supply device and the like, a power supply system having a superposed configuration by connecting a plurality of converters (switching power supplies) in parallel has been used.

  When a plurality of converters are connected in parallel, the output current of the converter having the higher output voltage is increased, resulting in variations in the output power of each converter. Therefore, a power supply system in which a plurality of converters are connected in parallel requires a configuration for aligning the output currents of the converters.

  A configuration that can be easily considered to equalize the output currents of the converters is as shown in FIG. In FIG. 1, the first DC-DC converter 100 performs DC-DC conversion on the input DC power supply, and the shunt regulator SRa performs energization of the photocoupler PCa according to the difference between the output voltage of the DC-DC converter 100 and the reference voltage. Control the flow rate. The photocoupler PCa provides feedback to the primary side switching unit of the converter main circuit 121. With such a configuration, the DC-DC converter 100 functions as a constant voltage converter with a stable output voltage. The configuration of the second DC-DC converter 101 is the same as the configuration of the first DC-DC converter 100. However, the transistor Q3 is connected in parallel to the shunt regulator SRb (so as to be bypassed).

  In this example, the second DC-DC converter 101 adjusts its own output current to the output current of the first DC-DC converter 100. The amplifier circuits 12a and 12b amplify the voltage drop caused by the current detection resistors R1a and R1b. The error amplifier circuit 13 amplifies the difference between the output voltages of the amplifier circuits 12a and 12b, and controls the photocoupler PCb via the transistor Q3. I do.

  In FIG. 1, when the output current of the second DC-DC converter 101 is larger, the output of the error amplifier circuit 13 increases, the collector current of the transistor Q3 increases, the light emission amount of the photocoupler PCb increases, and the main circuit 131. The feedback is applied in the direction of narrowing the output (decreasing the voltage). On the other hand, when the output current of the second converter 101 is smaller, the output of the error amplifier circuit 13 decreases, the collector current of the transistor Q3 decreases, the light emission amount of the photocoupler PCb decreases, and the main circuit 131 increases the output. Feedback is applied in the direction of increasing the voltage. However, if the output current of the second converter 101 becomes too small and the transistor Q3 is turned off, the constant voltage control portion operates thereafter, so that the voltage cannot be increased beyond the set voltage. For this reason, it is not realistic to employ a circuit that performs such control that causes one hand to fall.

  Therefore, for example, in Patent Document 1, a plurality of constant voltage control converters are used, and constant voltage control of other converters is performed so that the output current of the other converter matches the output current of one of the converters as a reference. The reference voltage is configured to change according to the difference from the output current of the reference converter. With such a configuration, the output current of other converters changes, and the output current matches the output current of the reference converter.

Here, the configuration of the power supply system disclosed in Patent Document 1 will be described with reference to FIG.
In FIG. 2, current detection resistors 111 and 112 are inserted at a connection point where DC-DC converters 102 and 103 are connected in parallel, and a differential voltage amplifier 113 that inputs and amplifies a voltage difference between both ends of the resistors 111 and 112. The output voltage of the differential voltage amplifier 113 is level-shifted by the level shift circuit 114, and the difference from the detected value of the output voltage of the DC-DC converter 102 is amplified by the error amplifier 123 using the level shift circuit 114 as a reference voltage. Feedback is provided to the main circuit 121 via the circuit 122.

  Due to such a configuration, the DC-DC converter 103 detects a difference between the output voltage and the reference voltage Vref with the error amplifier 133 and feeds it back to the main circuit 131 via the control circuit 132 so as to obtain a constant voltage. Output. The DC-DC converter 102 detects a difference between the output voltage and the output voltage of the level shift circuit 114 by the error amplifier 123 and feeds back to the main circuit 121 via the control circuit 122, thereby outputting a constant voltage. , The output current becomes equal to the output current of the converter 103.

Patent Document 2 shows a configuration in which a plurality of constant voltage control converters are connected in parallel, an average value of output currents of each converter is detected, and control is performed so that the output current of each converter becomes the average value. Has been.
Japanese Patent Laid-Open No. 11-18415 JP-A-8-115133

  However, in both Patent Documents 1 and 2, the feedback amount is changed according to the value of the output current, but the feedback path is detection of output current → current comparison → fluctuation of reference voltage with respect to error amplifier → Voltage control. That is, when the current balance between the converters is lost, the primary side of the converter is controlled through the voltage feedback path. As described above, since the voltage feedback path is once passed, there is a problem that control delay occurs and operation stability is low.

  Accordingly, an object of the present invention is to provide a power supply system including a plurality of converters that solves the above-described problems and has high control responsiveness and high operational stability.

  The present invention is provided with a plurality of converters each including a switching unit that switches an input power supply voltage and a smoothing unit that smoothes the switched voltage and outputs a DC voltage, and power is supplied to the same load by the plurality of converters. One of a plurality of converters is a constant voltage control converter including a constant voltage control circuit that detects an output voltage and maintains the output voltage at a set voltage. The current control converter includes a current control circuit that controls the output current to be equal to the output current of the constant voltage control converter.

The constant voltage control converter and the current control converter each include a current detection circuit that amplifies a voltage drop of a current detection resistor provided in the output current line and generates a voltage signal proportional to the output current. ,
The current control circuit directly controls a feedback signal to the switching unit by a difference between an output voltage of a current detection circuit included in the current control converter together with the current control circuit and an output voltage of a current detection circuit of the constant voltage control converter. Circuit.

  Furthermore, the current control converter includes an output voltage limiting circuit that detects the output voltage and limits the output voltage so that the output voltage does not exceed a predetermined voltage higher than the set voltage of the constant voltage control converter. .

  In the power supply system of the present invention, the output current of the current control converter matches the output current of the constant voltage control converter, and the power balance of both converters can be achieved. The output voltage of the current control converter inevitably matches the output voltage of the constant voltage control converter because a current of the same magnitude flows through the same load as the load of the constant voltage control converter. Therefore, the current control converter functions as a constant voltage converter while performing current control.

  According to the present invention, when the current balance between the converters is lost, the primary side of the converter is not controlled through the voltage feedback path, but is controlled so that direct current control is performed. can get.

  Further, by limiting the output voltage of the current control converter so as not to exceed a predetermined voltage higher than the set voltage of the constant voltage control converter, a phenomenon that the output voltage becomes abnormally high at the time of sudden load change can be avoided.

<< First Embodiment >>
FIG. 3 is a block diagram of the power supply system according to the first embodiment, and FIG. 4 is a specific circuit diagram thereof.
As shown in FIG. 3, this power supply system has a constant voltage control converter 20 and a current control converter 21 connected in parallel. That is, the input of the constant voltage control converter 20 and the current control converter 21 are connected in parallel, the outputs are connected in parallel, the input power is input from the input section IN, and a constant voltage is supplied to the load 14. is doing. The capacitor Co is an output voltage smoothing capacitor provided in the output section.

  The constant voltage control converter 20 includes a converter circuit 10a and a current detection circuit 15a. The current control converter 21 includes a converter circuit 10b, a current detection circuit 15b, and an error amplification circuit 13.

  The converter circuit 10a of the constant voltage control converter 20 receives a DC power supply voltage from the input terminal IN, converts it to a predetermined DC voltage, and outputs it. The converter circuit 10a includes a constant voltage control circuit that detects an output voltage and performs feedback control so that the output voltage is maintained at a set voltage. The current detection circuit 15a includes a current detection resistor R1a provided on the output current line, and an amplifier circuit 12a that amplifies the voltage across the resistor.

  The current detection circuit 15b in the current control converter 21 is composed of a current detection resistor R1b provided in the output current line and an amplifier circuit 12b that amplifies the voltage at both ends thereof. The error amplifying circuit 13 amplifies the difference voltage between the output voltage of the current detection circuit 15a of the constant voltage control converter 20 and the output voltage of the current detection circuit 15b of itself (current control converter 21), and converts the error voltage into the converter circuit 10b. Give to. The converter circuit 10b includes a current control circuit that feedback-controls the output current so that the potential difference between the two input voltages of the error amplifier circuit 13 approaches zero.

  With such a configuration, the set voltage of the constant voltage control converter 20 is supplied to the load 14 and the output current of the constant voltage control converter 20 and the output current of the current control converter 21 coincide with each other. Operate. Therefore, the current control converter 21 inevitably outputs the set voltage.

  As shown in FIG. 4, the converter circuit 10a of FIG. 3 includes a converter main circuit 11a, a constant voltage control circuit 16, and a smoothing capacitor C1a. The constant voltage control circuit 16 includes a resistance voltage dividing circuit composed of resistors R2 and R3 for detecting an output voltage, an operational amplifier OP1 for amplifying an error of the output divided voltage with respect to a reference voltage Vr1, resistors R4 and R5a, a transistor Q1a, And a photocoupler drive circuit including a light emitting diode of the photocoupler PCa.

  The light receiving portion side of the photocoupler PCa is provided on the primary side in the converter main circuit 11a. The primary side circuit of the converter main circuit 11a outputs the output of the converter as the amount of light received on the light receiving portion side of the photocoupler PCa increases. Control in the direction to decrease the voltage.

  Here, considering the case where the output voltage rises, the base current of the transistor Q1a increases as the output voltage rises. Therefore, the collector current also increases, and the converter main circuit 11a to the primary circuit of the converter main circuit 11a is increased by the photocoupler PCa. The amount of feedback increases and the output voltage acts in the downward direction. When the output voltage drops, the reverse action occurs, the amount of feedback to the primary side circuit of the converter main circuit 11a via the photocoupler PCa decreases, and the output voltage acts in the increasing direction. In this way, a set voltage corresponding to the reference voltage Vr1 is output.

  The amplifier circuit 12a in the current detection circuit includes resistors R6a, R7a, R8a, R9 and an operational amplifier OP2a. Similarly, the amplifier circuit 12b in the current detection circuit on the current control converter 21 side includes resistors R6b, R7b, R8b, R9b and an operational amplifier OP2b. The error amplifying circuit 13 includes resistors R10 and R11, a capacitor C2, and an operational amplifier OP3.

  The current control circuit 17 in the current control converter 21 is a photocoupler drive comprising a resistance voltage dividing circuit comprising resistors R12 and R13 for dividing the output voltage of the error amplifier circuit 13, a resistor R5b, a transistor Q1b, and a light emitting diode of the photocoupler PCb. It has a circuit.

  The light receiving part side of the photocoupler PCb is provided on the primary side in the converter main circuit 11b, and the primary side circuit of the converter main circuit 11b decreases the output voltage of the converter as the amount of light received by the photocoupler PCb increases. Control in the direction.

  When the output current of the current control converter 21 becomes larger than the output current of the constant voltage control converter 20, the output voltage of the error amplifying circuit 13 increases, so that the feedback becomes negative feedback control and the output current is stabilized. That is, the output currents of the two converters are controlled to be the same.

  With the circuit configuration shown in FIG. 4, the photocoupler drive circuit in the current control circuit 17 is directly controlled by the output voltage of the error amplifier circuit 13. That is, the difference between the output voltage of the error amplification circuit 12b of the current detection circuit provided in the current control converter 21 and the output voltage of the error amplification circuit 12a of the current detection circuit of the constant voltage control converter 20 is sent to the switching unit of the converter main circuit 11b. The feedback signal is directly controlled.

  By directly controlling the feedback signal to the switching unit in this way, the feedback signal to the switching unit as in Patent Documents 1 and 2 is detected as output current → current comparison → fluctuation of reference voltage for error amplifier → voltage control. Higher responsiveness can be obtained than in the case of indirect control taking a feedback path.

  The converter main circuits 11a and 11b generally have the same circuit configuration, but output currents are the same even if converters having different characteristics are used.

<< Second Embodiment >>
FIG. 5 shows a configuration of a power supply system according to the second embodiment.
In the first embodiment, one constant voltage control converter 20 and one current control converter 21 are provided and configured with a total of two converters. However, the second embodiment is an example in which three or more converters are provided. is there. In FIG. 5, the power supply system includes a constant voltage control converter 20 and a plurality of current control converters 21b to 21n. The configurations of the constant voltage control converter 20 and the current control converters 21b to 21n are the same as those shown in the first embodiment.

  Each of the current control converters 21b to 21n decreases the difference between the output voltage of the current detection circuit 15a of the constant voltage control converter 20 and the output voltage of the current detection circuits 15b to 15n of itself (current control converters 21b to 21n). Control the output voltage.

  With such a configuration. Since the output voltage with respect to the load 14 is maintained at the set voltage by the constant voltage action of the constant voltage control converter 20, each current control converter 21b to 21n performs current control so as to be equal to the output current of the constant voltage control converter 20. The output currents of all the converters are gathered to balance the power.

<< Third Embodiment >>
A configuration of a power supply system according to the third embodiment will be described with reference to FIG.
The configuration of the entire power supply system is the same as that shown in FIG. FIG. 6 is a circuit diagram of the converter circuit 10b in the current control converter 21 in the third embodiment.

  In FIG. 6, the current control circuit 17 includes a resistance voltage dividing circuit including resistors R12 and R13 that divides the output voltage of the error amplifier circuit 13, and a photocoupler driving circuit including a resistor R5b, a transistor Q1b, and a light emitting diode of the photocoupler PCb. ing.

  The converter circuit 10b is further provided with an output voltage limiting circuit 18. The output voltage limiting circuit 18 includes resistors R15, R16, R14, a reference voltage Vr2 generation circuit, an operational amplifier OP4, and a transistor Q2.

  The light receiving portion side of the photocoupler PCb is provided on the primary side in the converter main circuit 11b. The primary side circuit of the converter main circuit 11b increases the output voltage of the converter circuit 10b as the amount of light received by the photocoupler PCb increases. Control in the direction to decrease.

  Here, considering a state where the resistance divided voltage by the resistors R15 and R16 does not exceed the reference voltage Vr2, the output voltage of the operational amplifier OP4 becomes low level, and the transistor Q2 is turned off. That is, the output voltage limiting circuit 18 does not limit the output voltage.

  If the output voltage of the converter circuit 10b rises and the resistance divided voltage by the resistors R15 and R16 exceeds the reference voltage Vr2, the output voltage of the operational amplifier OP4 rises in the positive direction, and the collector current of the transistor Q2 increases. As a result, the amount of feedback to the primary side of converter main circuit 11b by photocoupler PCb increases. For this reason, an increase in the output voltage of the converter circuit 10b is suppressed.

  As described above, when the resistance divided voltage by the resistors R15 and R16 exceeds the reference voltage Vr2, the increase of the output voltage is limited. The upper limit voltage of the output voltage limiting circuit 18 is set to a predetermined voltage higher than the set voltage of the constant voltage control converter 20. For this reason, even when the output voltage of the converter circuit 10b increases when the load suddenly changes, the upper limit thereof does not extremely exceed the set voltage of the constant voltage control converter 20, so that the load 14a is stably set after all. A voltage will be supplied.

It is a figure which shows the structural example of the power supply system by a prior art. It is a figure which shows the structure of the power supply system shown by patent document 1. FIG. 1 is a block diagram of a power supply system according to a first embodiment. It is a circuit diagram of the power supply system. It is a figure which shows the structure of the power supply system which concerns on 2nd Embodiment. It is a figure which shows the structure of the current control converter used with the power supply system which concerns on 3rd Embodiment.

Explanation of symbols

10-converter circuit 11-converter main circuit 12-amplifier circuit 13-error amplifier circuit 14-load 15-current detection circuit 16-constant voltage control circuit 17-current control circuit 18-output voltage limiting circuit 20-constant voltage control converter 21 -Current control converter

Claims (3)

A power supply that provides a plurality of converters each including a switching unit that switches input power supply voltage and a smoothing unit that smoothes the switched voltage and outputs a DC voltage, and supplies power to the same load by the plurality of converters A system,
One of the plurality of converters is a constant voltage control converter including a constant voltage control circuit that detects an output voltage and maintains the output voltage at a set voltage, and the other converters of the plurality of converters are themselves The power supply system which is a current control converter provided with the current control circuit which controls so that the output current of may become the same as the output current of the said constant voltage control converter. The constant voltage control converter and the current control converter each include a current detection circuit that amplifies a voltage drop of a current detection resistor provided in the output current line and generates a voltage signal proportional to the output current,
The current control circuit directly controls a feedback signal to the switching unit by a difference between an output voltage of a current detection circuit included in the current control converter together with the current control circuit and an output voltage of a current detection circuit of the constant voltage control converter. The power supply system according to claim 1.   The current control converter includes an output voltage limiting circuit that detects an output voltage and limits the output voltage so that the output voltage does not exceed a predetermined voltage higher than the set voltage of the constant voltage control converter. The power supply system according to 1 or 2.

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