JP2000116125A - Power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a load current characteristic which curves downward to the right using a voltage drop characteristic caused by a resistor for a power circuit scheduled for parallel operation and make the load current characteristic the one having a desired gradient at a low resistance value. SOLUTION: This power circuit is constituted of a first circuit (D1, C1) which generates a predetermined DC voltage from the voltage induced in a secondary winding of a main transformer T1, a voltage detection circuit (R1, R2) which detects the output voltage transmitted between two output terminals 1 and 2 from the first circuit, a source E of reference voltage, an error amplifier 3 which outputs error voltage based on the detection voltage detected by the voltage detection circuit and the reference voltage from the source of reference voltage, and a second circuit 4 which turns an electronic switch Q1 on and off based on the error voltage. In this case, a resistor Rx is inserted in a return circuit of load current and one of the detection terminals of the voltage detection circuit is connected to the return current input side of the resistor and the negative pole of the source of reference voltage is connected to the return current output side of the resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device in which parallel operation is scheduled, and more particularly to a power supply device that forms a load current characteristic falling to the right by utilizing a voltage drop characteristic of a resistor.

[0002]

2. Description of the Related Art FIG. 4 shows a configuration example of a conventional power supply device. In FIG. 4, this power supply device includes a main transformer T1,
It includes a transistor Q1, a diode D1 for rectification, a diode D2 for preventing backflow, a capacitor C1, resistance voltage dividing circuits (R1, R2), an error amplifier 3, and a control circuit 4.

[0003] One end of the primary winding of the main transformer T1 is connected to the collector of the transistor Q1, and between the other end of the primary winding of the main transformer T1 and the emitter of the transistor Q1.
A DC voltage (V1) is applied. The base of the transistor Q1 is connected to the output terminal of the control circuit 4. Note that the DC voltage (V1) is, for example, an output voltage of a rectifier circuit. One end of the secondary winding of the main transformer T1 is connected to the anode of the diode D1, and the other end is connected to the output terminal 2. The cathode of the diode D1 is connected to the anode of the diode D2 and one end of the capacitor C1. Diode D
2 is connected to the output terminal 1. Output terminal 1
Is a positive electrode terminal. The other end of the capacitor C1 is connected to a connection line between the other end of the secondary winding of the main transformer T1 and the output terminal 2. The output terminal 2 is a negative terminal (0 V terminal). The resistor R indicated by a broken line in the connection line between the other end of the secondary winding of the main transformer T1 and the output terminal 2 is not usually inserted.

In the resistance voltage dividing circuit (R1, R2), one end of the resistor R1 is connected to a connection line between the cathode of the diode D1 and the anode of the diode D2, and the other end is connected to one end of the resistor R2. . The other end of the resistor R2 is connected to a connection line between the other end of the secondary winding of the main transformer T1 and the output terminal 2. A connection end between the other end of the resistor R1 and one end of the resistor R2 is connected to an inverting input terminal of the error amplifier 3. The error amplifier 3 has a non-inverting input terminal connected to the positive terminal of the reference power supply E, and an output terminal connected to an input terminal of the control circuit 4. The negative electrode of the reference power supply E is connected to a connection line between the other end of the secondary winding of the main transformer T1 and the output terminal 2.

[0005] The power supply device configured as described above operates roughly as follows. The predetermined DC voltage (V1) is
The voltage is applied to both ends of a series circuit of the primary winding of the main transformer T1 and the transistor Q1. In this state, the control circuit 4 controls on / off of the transistor Q1 to turn on / off the DC voltage (V1) applied to the primary winding of the main transformer T1.

For example, during the ON period of the transistor Q1, the voltage induced in the secondary winding is rectified by the diode D1, smoothed by the capacitor C1, and passed through the diode D2 to a predetermined DC voltage between the output terminals 1 and 2. Is output.
In the above operation process, the resistance voltage dividing circuits (R1, R2) supply the detected value of the output voltage (V) (the voltage across the resistor R2) to the error amplifier 3, and the error amplifier 3 An error between the reference voltage VREF and the detection value of the output voltage V is detected, and the control circuit 4 detects a difference between the transistor Q based on the detected error.
By controlling the conduction width of 1, the output voltage V is stabilized. The diode D2 blocks a current flowing from the output terminal 1 into the inside.

[0007] By the way, for example, a computer system is divided into a basic function part and an additional function part that can be added as an option, and the additional function part differs depending on the user. Therefore, it is uneconomical to prepare the configuration of the power supply unit assuming full mounting from the beginning.
A power supply unit with a basic capacity is specified, and multiple units can be mounted.To cope with an increase in load, a predetermined number of basic power supply units are additionally mounted, and the entire load including the increased load is used as a basic unit. A method is adopted in which power is supplied by parallel operation of a plurality of power supply units. Hereinafter, a conventional parallel operation system will be described with reference to FIGS.

FIG. 5 shows load current characteristics. In this type of power supply, there is usually no resistor R indicated by a broken line in FIG.
The output voltage in this case shows a constant value even when the load current (I0) increases, as shown by "No R" in FIG. In this case, if there is no difference in the voltage that can be supplied to the load terminal among the plurality of power supply units that are operated in parallel, all of the power supply units can share the load according to the capacity.

However, a plurality of power supply units which are operated in parallel are all manufactured with the same specifications. However, due to the setting deviation of the output voltage of each power supply unit, the difference of the voltage drop of the diode D2, and the difference of the line length to the load. Usually, a difference in the voltage that can be supplied to the load terminal occurs due to a difference in the voltage drop. Then, when the load current characteristic of the output voltage is a constant value as shown by “No R” in FIG. 5, a power supply device that cannot share the load appears, and only some of the power supply devices share the load. Unbalanced state.

This problem can be solved by making the load current characteristic of the output voltage of each of the power supply units operated in parallel a downward-sloping characteristic. Conventionally, this downward-sloping characteristic is, as shown in FIG. 4, between the output terminal 2 and the other end of the resistor R2.
It is obtained by inserting a resistor R. In FIG. 4, the connection line between the output terminal 2 and the other end of the secondary winding of the main transformer T1 is a return path of the load current.
As shown in FIG. 4, when the resistor R is inserted between the output terminal 2 and the other end of the resistor R2, the return load current I0 flows through the resistor R, and there is a voltage drop of R · I0. The output voltage detected by the resistance voltage dividing circuit (R1, R2) is VR-IO. In other words, the load current characteristic of the output voltage in this case is
As shown by "with R" in FIG. 5, the characteristic becomes lower right as the load current (I0) increases.

That is, conventionally, when a plurality of power supply units of the same specification are operated in parallel, a resistor R is inserted as shown in FIG. The device can supply the load current in a well-balanced manner. FIG. 6 is a diagram illustrating the operation of the parallel operation. In FIG. 6A, two power supply devices 10, 1
1 have the same rating, but consider a case where they share the common load 12 at a certain ratio. Each of the two power supply devices 10 and 11 has a resistor R shown by a broken line in FIG. 4 inserted therein, and has a load current characteristic falling to the right as shown in FIG. However, the value of the resistor R is the same in the two power supplies 10 and 11.

Therefore, the load current characteristics of the two power supply devices have a relation of being shifted in parallel as shown in FIGS. 6 (a) and 6 (b). FIGS. 6A and 6B show a case where the output voltage of the power supply device 10 is higher than that of the power supply device 11. FIG.
As shown in (a) and (b), when the output voltage matches the load voltage V0, the power supply 10 supplies the load current Ia, and the power supply 11 supplies the load current Ib. Assuming that the current required by the load 12 is I0, I0 = Ia + Ib. However, both power supply devices balance the current so that the difference between the current Ia and the current Ib is constant. FIG. 6A shows a case where the difference between the current Ia and the current Ib is small, and FIG.
The case where the difference between a and the current Ib is large is shown.

[0013]

In the case where the load current is balanced by utilizing the load current characteristic falling downward, in the above-described example, the smaller the difference between the current Ia and the current Ib, the smaller the power supply efficiency. Get better. In order to reduce the difference between the current Ia and the current Ib, the slope of the load current characteristic falling to the right may be increased as shown in FIG. 6A. In the case of realizing by using, there are the following problems.

That is, by increasing the value of the resistor R to be inserted, the slope of the load current characteristic falling to the right can be increased.
As the loss in the resistor R increases, the power supply efficiency decreases. Particularly, in the case of a large current load, it is necessary to use a resistor for high power as the resistor R to be inserted. However, components for high power are generally large and expensive. An object of the present invention is to provide a power supply device capable of obtaining a load current characteristic having a low resistance value and a desired slope when a load current characteristic falling to the right is realized by using a voltage drop characteristic by a resistor. It is in.

[0015]

According to a first aspect of the present invention, there is provided a power supply device comprising: a main transformer; an electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer; A first circuit for generating a predetermined direct-current voltage from a voltage appearing in the next winding, a voltage detection circuit for detecting an output voltage transmitted between the two output terminals by the first circuit, a reference voltage source, and a voltage detection circuit A power supply device comprising: an error amplifier that outputs an error voltage based on the detected voltage and a reference voltage from the reference voltage source; and a second circuit that turns on and off the electronic switch based on the error voltage. Inserting a resistor in the return path, connecting one detection end of the voltage detection circuit to the return current input side of the resistor, and connecting the negative electrode of the reference voltage source to the return current output side of the resistor. Characterized in that there.

According to a second aspect of the present invention, there is provided a power supply device comprising:
A main transformer, an electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer, a first circuit for generating a predetermined DC voltage from a voltage appearing on a secondary winding of the main transformer, A voltage detection circuit for detecting an output voltage sent out between the two output terminals by the circuit, a reference voltage source,
A power supply device comprising: an error amplifier that outputs an error voltage based on a detection voltage of a voltage detection circuit and a reference voltage from the reference voltage source; and a second circuit that turns on and off the electronic switch based on the error voltage. An amplifier that inserts a resistor in the return path of the load current and amplifies a voltage drop at the resistor; connects one detection terminal of the voltage detection circuit to an output terminal of the amplifier; Is connected to the return current output side of the resistor. According to a third aspect of the present invention, there is provided a power supply device comprising: a main transformer; an electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer; and a predetermined voltage based on a voltage appearing on a secondary winding of the main transformer. A first circuit that generates a DC voltage, a voltage detection circuit that detects an output voltage that the first circuit sends out between two output terminals, a reference voltage source, a detection voltage of the voltage detection circuit, and the reference voltage source. In a power supply device including an error amplifier that outputs an error voltage based on the reference voltage and a second circuit that turns on and off the electronic switch based on the error voltage, a resistor is inserted in a return path of a load current, An amplifier for amplifying a voltage drop at the resistor is provided; one detection end of the voltage detection circuit and a negative electrode of the reference voltage source are connected to a return current input side of the resistor; Sum of the output value of the positive extreme and the amplifier of pressure source, characterized in that the said reference voltage.

(Operation) In the first aspect of the present invention, a resistor is inserted in the return path of the load current. However, the voltage detection circuit detects the actual output voltage regardless of the voltage drop at the resistor. To detect. On the other hand, the reference voltage given to the error amplifier is
Reduced by the voltage drop across the resistor. The slope of the load current characteristic of the output voltage decreases in accordance with the ratio between the reference voltage and the voltage drop at the resistor.

In other words, the slope of the load current characteristic of the output voltage according to the related art depends on the ratio to the output voltage. However, according to the present invention, the slope according to the ratio to the reference voltage which is lower than the output voltage is different. It will be. Therefore, assuming that the slope of the load current characteristic of the output voltage is the same as that of the related art, the value of the resistor inserted in the return path of the load current can be considerably lower in the present invention than in the related art.

According to the second aspect of the present invention, the voltage drop at the resistor inserted in the return path of the load current is amplified by the amplifier,
The amplified voltage is set to be a rise of the detection voltage in the voltage detection circuit. On the other hand, the reference voltage applied to the error amplifier is reduced by the voltage drop in the resistor. The slope of the load current characteristic of the output voltage decreases in accordance with the ratio between the reference voltage and the voltage obtained by amplifying the voltage drop at the resistor.
Therefore, the value of the resistor inserted in the return path of the load current is
The value may be lower than in the case of the first aspect of the invention.

According to the third aspect of the present invention, the resistor is inserted in the return path of the load current, but the voltage detection circuit detects the actual output voltage irrespective of the voltage drop in the resistor. On the other hand, the voltage drop in the resistor inserted in the return path of the load current is amplified by an amplifier so that the amplified voltage is the drop of the reference voltage applied to the error amplifier. The slope of the load current characteristic of the output voltage has a relationship that decreases in accordance with the ratio between the reference voltage and the voltage obtained by amplifying the voltage drop at the resistor, as in the second aspect of the invention. Therefore, the value of the resistor inserted in the return path of the load current can be a lower value than in the case of the first aspect of the invention, similarly to the second aspect of the invention.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
1 is a configuration example of a power supply device according to an embodiment. In FIG. 1,
The same parts as those in the conventional example (FIG. 4) are denoted by the same reference numerals and names. In the first embodiment, as shown in FIG.
In the connection line (0 V line) between the output terminal 2 and the other end of the secondary winding of the main transformer T1, which is the return path of the load current, the connection point between the other end of the resistor R2 and the negative electrode of the reference voltage source E , A resistor Rx is inserted between the connection point and the connection point. The ground terminal of the error amplifier 3 is connected to a 0 V line which is a return path of the load current.

The correspondence between the above configuration and claim 1 is as follows. The main transformer has a main transformer T1
Corresponds. The transistor Q1 corresponds to the electronic switch. The first circuit includes a diode D1 and a capacitor C
1 corresponds to the rectifying and smoothing circuit. A resistance voltage dividing circuit (R1, R2) corresponds to the voltage detecting circuit. A reference voltage source E corresponds to the reference voltage source. The error amplifier has
The error amplifier 3 corresponds. The control circuit 4 corresponds to the second circuit. A resistor Rx corresponds to the resistor inserted in the return path of the load current.

Next, the operation of the first embodiment will be described with reference to FIG. Since the resistor Rx is inserted in the return path of the load current, there is a voltage drop at the resistor Rx, and the load current characteristic of the output voltage is a right-down characteristic as in the conventional example (FIG. 4). However, a resistor voltage dividing circuit (R
In (1, R2), the actual output voltage is detected irrespective of the voltage drop at the resistor Rx. Note that V0 shown is a supply voltage when a load is connected.

When a load is connected, since the load current flows from the output terminal 2 on the return path of the load current, the resistor R
Due to the voltage drop at x, the negative potential of the reference voltage source E is transferred to the negative side. As a result, the reference voltage VREF applied to the error amplifier 3 is reduced by the voltage drop at the resistor Rx. Therefore, the slope of the load current characteristic of the output voltage has a relationship that decreases according to the ratio between the reference voltage VREF and the voltage drop at the resistor Rx.

Hereinafter, the relationship between the resistor R of the conventional example (FIG. 4) and the resistor Rx in the present embodiment when the slope of the load current characteristic of the output voltage is the same will be obtained. In this embodiment, the output voltage V0 when the load current I0 is supplied is as follows: V0 = {(R1 + R2) / R2} (VREF-I0.Rx) (1)

On the other hand, the output voltage V0 when the load current I0 is supplied in the conventional example (FIG. 4) is as follows: V0 = {(R1 + R2) / R2} .VREF-I0.R (2) However, if {(R1 + R2) / R2} .VREF = V (no-load output voltage), the equation (2) becomes as follows: V0 = V-I0.R (3) Expression (1) is as follows: V0 = V−I0 · Rx · {(R1 + R2) / R2} (4) Then, from Expressions (3) and (4), R = Rx ｛{(R1 + R2) / R2} (5) is obtained. Since (R1 + R2) / R2 = V / VREF, Expression (5) is R = Rx · (V / VREF) (6) From this, Rx = R · (VREF / V) (7) is obtained.

Here, VREF≪V. Equation (1)
From (3), the slope of the load current characteristic of the conventional output voltage is
Although it depends on the ratio to the output voltage, in the present embodiment, it is understood that the ratio depends on the ratio to the reference voltage which is lower than the output voltage. Therefore, assuming that the slope of the load current characteristic of the output voltage is the same as that of the related art, the value of the resistor inserted in the return path of the load current may be considerably lower in the present embodiment than in the related art. Specifically, in the present embodiment, the value of the resistor Rx can be set to a value significantly smaller than that of the resistor R of the conventional example (FIG. 4) at the ratio shown in Expression (7).

Next, FIG. 2 shows a configuration example of a power supply unit according to a second embodiment of the present invention. In the second embodiment, an amplifier 5 for amplifying a voltage drop of the resistor Rx is provided in the first embodiment, and an output terminal of the amplifier 5 is connected to the resistor R2.
Is connected to the other end. Therefore, the amplifier 5 corresponds to the amplifier in claim 2. Hereinafter, the operation of the portion according to the second embodiment will be described. In the second embodiment,
Assuming that the amplification degree of the amplifier 5 is Y, the voltage drop I0 · Rx of the resistor Rx is multiplied by Y by the amplifier 5. In the resistive voltage dividing circuit (R1, R2), which is a voltage detecting circuit, the divided voltage, which is the detection voltage, is increased by the voltage multiplied by Y. Shows a characteristic that decreases at the rate of

In comparison with the conventional example, Rx = (VREF
/ Y · V) · R. The value can be made smaller than in the first embodiment. Next, FIG. 3 shows a configuration example of a power supply device according to a second embodiment of the present invention. This third
In the embodiment, an amplifier 6 for amplifying a voltage drop of the resistor Rx is provided in the first embodiment, and an output terminal of the amplifier 6 is connected to a non-inverting input terminal of the error amplifier 3 via a resistor R3. The positive terminal of the voltage source E is connected to the non-inverting input terminal of the error amplifier 3 via the resistor R4. Therefore, the amplifier 6 corresponds to the amplifier in claim 3.

Hereinafter, the operation of the portion according to the third embodiment will be described. In the third embodiment, the amplification degree of the amplifier 6 is set to Y
Then, the drop voltage I0.Rx of the resistor Rx is multiplied by Y by the amplifier 6. Since the voltage multiplied by Y is a decrease in the reference voltage applied to the error amplifier 3, the output voltage exhibits a characteristic of decreasing at a ratio of the reference voltage VREF to Y ・ I0 ・ Rx.

In comparison with the conventional example, Rx = (VREF
/ Y · V) · R. The value can be made smaller than in the first embodiment.

[0032]

As described above, according to the first aspect of the present invention, the slope of the load current characteristic of the output voltage depends on the ratio between the reference voltage and the voltage drop at the resistor inserted in the return path of the load current. Therefore, the value of the resistor inserted in the return path of the load current can be considerably lower than the conventional value when the slope of the load current characteristic of the output voltage is the same as the conventional value. it can.

According to the second and third aspects of the present invention,
The slope of the load current characteristic of the output voltage decreases in proportion to the ratio between the reference voltage and the amplified voltage of the voltage drop at the resistor inserted in the return path of the load current. The value of the resistor can be even lower than in the case of the first aspect of the invention. Therefore, according to the first to third aspects of the present invention, it is not necessary to use a large resistor even for a large current load, and it is possible to reduce power consumption and improve power supply efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of a power supply device according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration example of a power supply device according to a second embodiment.

FIG. 3 is a diagram illustrating a configuration example of a power supply device according to a third embodiment.

FIG. 4 is a diagram illustrating a configuration example of a conventional power supply device.

FIG. 5 is a diagram showing a load current characteristic of an output voltage.

FIG. 6 is a diagram illustrating the operation of parallel operation. (A) is a block diagram. (B) is a diagram showing load current characteristics when the slope is steep. (C) is a diagram showing load current characteristics when the slope is gentle.

[Explanation of symbols]

 1, 2 output terminal 3 error amplifier 4 control circuit 5, 6 amplifier Rx resistor Q1 transistor T1 main transformer D1, D2 diode C1 capacitor E reference voltage source R1, R2 resistor of voltage detection circuit

Claims (3)

[Claims] An electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer;
A first circuit that generates a predetermined DC voltage from a voltage appearing in a secondary winding of the main transformer, a voltage detection circuit that detects an output voltage that the first circuit sends out between two output terminals,
A reference voltage source, an error amplifier that outputs an error voltage based on a detection voltage of a voltage detection circuit and a reference voltage from the reference voltage source, and a second circuit that turns on and off the electronic switch based on the error voltage. In the power supply device, a resistor is inserted in a return path of a load current, one detection end of the voltage detection circuit is connected to a return current input side of the resistor, and a negative electrode of the reference voltage source is connected to a return path of the resistor. A power supply device connected to a current output side. 2. A main transformer, an electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer,
A first circuit that generates a predetermined DC voltage from a voltage appearing in a secondary winding of the main transformer, a voltage detection circuit that detects an output voltage that the first circuit sends out between two output terminals,
A reference voltage source, an error amplifier that outputs an error voltage based on a detection voltage of a voltage detection circuit and a reference voltage from the reference voltage source, and a second circuit that turns on and off the electronic switch based on the error voltage. A power supply device comprising: a resistor inserted into a return path of a load current; an amplifier for amplifying a voltage drop at the resistor; and one detection terminal of the voltage detection circuit connected to an output terminal of the amplifier. And a negative electrode of the reference voltage source is connected to a return current output side of the resistor. 3. A main transformer, an electronic switch for turning on and off a DC voltage applied to a primary winding of the main transformer,
A first circuit that generates a predetermined DC voltage from a voltage appearing in a secondary winding of the main transformer, a voltage detection circuit that detects an output voltage that the first circuit sends out between two output terminals,
A reference voltage source, an error amplifier that outputs an error voltage based on a detection voltage of a voltage detection circuit and a reference voltage from the reference voltage source, and a second circuit that turns on and off the electronic switch based on the error voltage. In the power supply device, a resistor is inserted in a return path of the load current, and an amplifier for amplifying a voltage drop at the resistor is provided, and one detection terminal of the voltage detection circuit and a negative electrode of the reference voltage source are connected. A power supply unit connected to a return current input side of the resistor, wherein a sum of a positive value of the reference voltage source and an output value of the amplifier becomes the reference voltage.