JPH10164841A - Direct-current converter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC converter device of simple circuitry that is capable of bringing the output currents of a plurality of DC-to-DC converters into equilibrium, and further always operating them parallel in a favorable manner. SOLUTION: In the direct-current converter device, the inverting input terminals on the comparators 16 in the current mode-type PWM control circuits 19 in DC-to-DC converters A, B, are connected with each other through respective resistors 31. Thereby, the voltages of the inverting input terminals on the comparators 16 in the current mode-type PWM control circuits 19 in the DC-to- DC converters A, B are equalized, and the respective transistors 8 in the converters A, B are controlled using the same on period; therefore, the output currents Io of the converters A, B are brought into equilibrium. Since no special output current detecting circuit is necessary, it is possible to bring the output currents Io of the converters A, B through simple circuitry, and thus always operate the converters A, B parallel in a favorable manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel operation of a plurality of DC-DC converters constituting a DC converter.

[0002]

2. Description of the Related Art A DC converter device in which a plurality of DC-DC converters are connected in parallel to a load has been conventionally used as a large-capacity DC power supply device for electric equipment such as an uninterruptible power supply and information equipment such as a personal computer. Or, it is widely used in fields such as mechatronics. For example, FIG.
In the conventional DC converter device shown in FIG. 1, a DC power supply 3 is connected to DC input terminals 1 and 2 of two flyback type DC-DC converters A and B having the same configuration, respectively.
The DC output terminals 4 and 5 of the converters A and B are respectively connected in parallel, and the DC outputs from the converters A and B are supplied to the load 6. Each DC-DC converter A, B
A primary winding 7a of a transformer 7 and a transistor 8 as a switching element, which are connected in series to the DC input terminals 1 and 2, between a secondary winding 7b of the transformer 7 and the DC output terminals 4 and 5; A rectifying diode 9 and a smoothing capacitor 10 forming a connected rectifying and smoothing circuit; a current detecting resistor 11 serving as current detecting means connected in series with the transistor 8 and detecting a current flowing through the transistor 8 as a voltage corresponding thereto; , a reference power supply 13 which generates a reference voltage V _R which gives the reference value of the DC output voltage V _O, those of the error signal by comparing the reference voltage V _R of voltage and the reference power supply 13 between the DC output terminals 4 and 5 Error amplifier 14 that outputs
And an error amplifier 14 input to an inverting input terminal (one control input terminal) via a light emitting unit 15a of the photocoupler 15 driven based on an error signal of the error amplifier 14 and a light receiving unit 15b of the photocoupler 15. Control signal and non-inverting input terminal (the other control input terminal) based on the error signal of
And a control pulse signal applied to the base terminal of the transistor 8 based on the comparison output of the comparator 16 and the clock pulse output of the clock pulse generation circuit 17. And a latch circuit 18. The light source 15a of the reference power supply 13, the error amplifier 14, and the photocoupler 15 detects the voltage between the DC output terminals 4 and 5, compares the detected voltage with the reference voltage V _R of the reference power supply 13, and detects an error therebetween. An output voltage detection circuit 12 that outputs a signal is configured. The light receiving section 15 b of the photocoupler 15, the comparator 16, the clock pulse generation circuit 17 and the latch circuit 18 respond to a comparison output between a voltage control signal based on an error signal of the output voltage detection circuit 12 and a detection voltage of the current detection resistor 11. Thus, a current mode PWM control circuit 19 for controlling the ON / OFF period of the transistor 8 is constituted. Also, each D
Between the DC output terminals 5 of the C-DC converters A and B and the light emitting portion 15a of the photocoupler 15 in the voltage detection circuit 12, the output current of each of the converters A and B is detected and each output current is detected. An output current detection circuit 2 including an output current detection resistor 20 for balancing and an error amplifier 21
2 are connected respectively. In FIG. 5, 23, 2
4 shows a diode for preventing reverse current, V _CC indicates the voltage of the drive power supply of the various circuits.

Each of the DC-DC converters A and B shown in FIG.
, A DC power supply 3 applied to DC input terminals 1 and 2
The DC input voltage V _i is turned on and off by the on / off operation of the transistor 8 and is converted into high-frequency power, and a high-frequency pulse current flows through the primary winding 7 a of the transformer 7 and the transistor 8. As a result, a high-frequency pulse voltage is generated in the secondary winding 7b of the transformer 7 every time the transistor 8 is turned off, and this high-frequency pulse voltage is converted into a smooth DC voltage by the rectifier diode 9 and the smoothing capacitor 10, and The DC output voltage V _O is supplied from the output terminals 4 and 5 to the load 6. Next, each DC-DC converter A shown in FIG.
Explaining the constant voltage control operation of B, the DC output voltage V _O between the DC output terminals 4 and 5 is input to the non-inverting input terminal (+ terminal) of the error amplifier 14 in the output voltage detection circuit 12 and Reference power supply 13 input to (-terminal)
Is compared with the reference voltage V _R, an error signal is output from the output terminal of the error amplifier 14. The light emitting unit 15 a of the photocoupler 15 is driven by the error signal of the error amplifier 14 via the backflow prevention diode 24, and the light output of the light emitting unit 15 a of the photocoupler 15 is controlled based on the error output of the error amplifier 14. The light output of the light emitting unit 15a of the photocoupler 15 is transmitted to the light receiving unit 15b, and the current flowing through the light receiving unit 15b is controlled according to the light output of the light emitting unit 15a. Therefore, when the DC output voltage V _O between the DC output terminals 4 and 5 is higher than the reference voltage V _R of the reference power supply 13, the current flowing through the light receiving portion 15b of the photocoupler 15 increases and is shown in FIG. Collector voltage V of light receiving portion 15b of photocoupler 15
_PC lowers. Conversely, when the DC output voltage V _O between the DC output terminals 4 and 5 is lower than the reference voltage V _R of the reference power supply 13, the current flowing to the light receiving portion 15b of the photocoupler 15 decreases and FIG. Light receiving section 1 of photocoupler 15 shown in B)
5b collector voltage V _PC of increases. Current mode type PW
Collector voltage V _PC of the light receiving portion 15b of the photocoupler 15 in the M control circuit 19 comparator 1 as a voltage control signal
6, the detection voltage V _TR of the current detection resistor 11 input to the non-inverting input terminal shown in FIG.
And the comparison output is input to the reset terminal (R terminal) of the latch circuit 18. On the other hand, the clock pulse signal V _CL of the clock pulse generation circuit 17 shown in FIG. _6A is input to the set terminal (S terminal) of the latch circuit 18,
From the output terminal of the latch circuit 18 is the control pulse signal V _B shown in FIG. 6 (C) is output. Therefore, when the DC output voltage V _O between the DC output terminals 4 and 5 is higher than the reference voltage V _R of the reference power supply 13, the collector voltage V _PC of the light receiving portion 15b of the photocoupler 15 becomes lower, so that the current mode type PWM
ON period of the control pulse signal V _B applied from the control circuit 19 to the base terminal of the transistor 8 becomes shorter. Also,
The DC output voltage V _O between the DC output terminals 4 and 5 is
3 is lower than the reference voltage V _R, the collector voltage V _PC of the light receiving portion 15b of the photocoupler 15 increases, so that the control pulse signal V _{B applied} to the base terminal of the transistor 8 from the current mode PWM control circuit 19 Becomes longer. By the above operation, the DC output voltage V _O between the DC output terminals 4 and 5 of the DC-DC converters A and B is controlled to a constant value, and the DC output of a constant voltage is supplied from the converters A and B to the load 6. Is done.

[0004] Here, if the output current I _O of the DC-DC converter A is greater than the output current I _O of the DC-DC converter B, the DC output voltage V _O at the DC output terminals 4 and 5 of the converter A is the converter B Since it becomes lower than the DC output voltage V _{O at the} DC output terminals 4 and 5, the light emitting section 15 a of the photocoupler 15 from the output terminal of the error amplifier 14 of the output voltage detection circuit 12 in the converter A via the backflow prevention diode 24. Is smaller than the current flowing from the output terminal of the error amplifier 14 of the output voltage detection circuit 12 in the converter B to the light emitting portion 15a of the photocoupler 15 via the backflow prevention diode 24. At this time, the polarity of the voltage across the output current detection resistor 20 in the output current detection circuit 22 of each of the DC-DC converters A and B is as shown in FIG. Therefore, DC-
A diode 23 for preventing backflow from an output terminal of the error amplifier 21 in the output current detection circuit 22 in the DC converter A
The current flowing into the light emitting portion 15a of the photocoupler 15 through the light-emitting portion 15a of the photocoupler 15 from the output terminal of the error amplifier 21 in the output current detecting circuit 22 in the DC-DC converter B via the diode 23 for preventing backflow. It is larger than the current that flows. These currents are
A backflow prevention diode 24 from the output terminal of the error amplifier 14 of the output voltage detection circuit 12 in the DC converters A and B;
Are superimposed on the current flowing through the light emitting portion 15a of the photocoupler 15 through the converters A and B, respectively.
The current flowing through the light emitting portion 15a of the photocoupler 15 becomes uniform. Therefore, the ON period of the control pulse signal V _B applied from the current-mode PWM control circuit 19 to the base terminal of the transistor 8 becomes equal among each converter A, B. Therefore, each DC-DC converter A,
Since the output current _{IO of} B becomes equal, each converter A,
The output current _{IO of} B can be balanced.

[0005]

In the DC converter shown in FIG. 5, each DC-DC converter A,
The output current detection circuit 22 provided for each of the converters A and B detects the output current I _O of each of the converters A and B, and emits light of the photocoupler 15 in each of the converters A and B according to the detection signal. By controlling the currents flowing through 15a to be equal to each other, each converter A, B
It is evenly and allowed to equilibrate for each output current I _O to respective output current I _O of. Therefore, since one output current detection circuit 22 is required for each of the plurality of DC-DC converters constituting the DC converter device, the number of components increases, and the circuit configuration of the entire DC converter device becomes complicated. There were drawbacks. If the output current detection circuit 22 fails, the output currents of the DC-DC converters cannot be balanced, and it is difficult to satisfactorily operate the DC-DC converters in parallel.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC converter capable of balancing output currents of a plurality of DC-DC converters with a simple circuit configuration and capable of always performing good parallel operation.

[0007]

A DC converter according to the present invention comprises at least one switching element for intermittently converting a DC input voltage of a DC power supply into an RF power by an on / off operation, and the RF power to a load. A rectifying / smoothing circuit for converting to a supplied DC output voltage, current detecting means for detecting a current flowing through the switching element as a corresponding voltage, detecting the DC output voltage, and detecting the detected voltage and a reference for the DC output voltage. An output voltage detecting means for comparing the output voltage detecting means with a reference voltage giving a value and outputting an error signal thereof; a voltage control signal based on the error signal of the output voltage detecting means input to one control input terminal; A comparison is made between the detection voltages of the current detection means input to the terminals, and the switching element is turned on or off according to the comparison output. Current-mode type PWM to control the duration
And a plurality of DC-DC converters for supplying a constant-voltage DC output to the load by controlling on / off of the switching element, in parallel with the load. In this DC converter device, the current mode type P in each DC-DC converter
One control input terminal of the WM control circuit is connected to each. In the illustrated embodiment, one control input terminal of the current-mode PWM control circuit in each of the DC-DC converters is connected via a resistor. Further, one control input terminal of the current mode PWM control circuit in each of the DC-DC converters may be connected via a parallel circuit of a resistor and an amplifier or a parallel circuit of a rectifier and an amplifier, respectively.

By connecting one control input terminal of the current mode PWM control circuit in each DC-DC converter to the other, the voltage of one control input terminal of the current mode PWM control circuit in each DC-DC converter is connected. Are all equal. Therefore, each switching element in each DC-DC converter is controlled by a current mode PWM control circuit corresponding to each switching element in the same ON / OFF period, and each DC-D
All the output currents of the C converter become equal. Therefore, the output currents of the plurality of DC-DC converters can be balanced with a simple circuit configuration, and the plurality of DC-DC converters can always be favorably operated in parallel.
When one control input terminal of the current mode type PWM control circuit in each DC-DC converter is connected via a parallel circuit of a resistor and an amplifier or a parallel circuit of a rectifier and an amplifier, respectively, More balanced current can flow through the amplifier between each other, so that the respective output currents of a greater number of DC-DC converters are balanced, and a greater number of DC-DC converters are always operated in good parallel operation. Is possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the DC converter according to the present invention will be described below with reference to FIG. However,
In FIG. 1, the same portions as those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 1, the DC converter device according to the embodiment of the present invention omits the output current detection circuit 22 of each of the DC-DC converters A and B in the DC converter device shown in FIG. In this case, the inverting input terminals of the comparator 16 of the current mode type PWM control circuit 19 in FIG. Other configurations are substantially the same as those of the DC converter device shown in FIG. The resistor 31 is a resistor for protecting the phototransistor constituting the light receiving portion 15b of the photocoupler 15, that is, a current limiting resistor.
Those having a relatively low resistance value of about Ω are used.

[0010] In the above configuration, when the output current I _O of the DC-DC converter A is greater than the output current I _O of the DC-DC converter B, the DC output voltage V _O at the DC output terminals 4 and 5 of the converter A is Converter Since the voltage becomes lower than the DC output voltage V _{O at} the DC output terminals 4 and 5 of B, the light emission of the photocoupler 15 from the output terminal of the error amplifier 14 of the output voltage detection circuit 12 in the converter A via the backflow prevention diode 24. The current flowing through the section 15a is supplied to the error amplifier 1 of the output voltage detection circuit 12 in the converter B.
4 is smaller than the current flowing from the output terminal 4 to the light emitting section 15a of the photocoupler 15 via the backflow prevention diode 24. Accordingly, the current flowing through the light receiving portion 15b of the photocoupler 15 in the DC-DC converter A becomes DC-D
Although the current flowing through the light receiving portion 15b of the photocoupler 15 in the C converter B tends to be smaller than the current flowing through the light receiving portion 15b of the photocoupler 15 in the DC-DC converter B, the resistance 31 and the DC-DC converter A
Since the balanced current flows into the light receiving portion 15b of the photocoupler 15 in the converter A via the resistor 31 therein, the current flowing in the light receiving portion 15b of each photocoupler 15 in each of the converters A and B becomes uniform. This allows each DC
-Current mode PWM in DC converters A and B
Since each voltage of the inverting input terminal of the comparator 16 of the control circuit 19 becomes equal, the current mode type PWM control circuit 19
ON period of the control pulse signal V _B from being applied to the base terminal of the transistor 8 is each converter A, respectively, become equal among B. Therefore, the output current I _{O of} each of the DC-DC converters A and B becomes equal, and
The output current _{IO of} B can be balanced.

In the DC converter shown in FIG.
Current mode PW in C-DC converters A and B
By connecting the inverting input terminals of the comparator 16 of the M control circuit 19 via the respective resistors 31, the current mode PWM control circuit 19 in each of the converters A and B is connected.
The voltages at the inverting input terminals of the comparator 16 become equal, and the output currents _IO of the converters A and B are balanced. This eliminates the need for a special output current detection circuit that has been required conventionally, so that the output current I _O of each of the DC-DC converters A and B can be balanced with a simple circuit configuration, and the converters A and B are always Good parallel operation is possible.

The DC converter of the embodiment shown in FIG. 1 can be modified. For example, the DC converter shown in FIG. 2 is a DC-D converter of the DC converter shown in FIG.
An amplifier 32 is connected in parallel with the resistor 31 in each of the C converters A and B. In the DC converter device shown in FIG. 2, the light receiving unit 15 of the photocoupler 15 in the DC-DC converter B (or A) having the smaller output current _IO is used.
DC-DC converter A having a larger output current _IO from b
(Or B), a larger amount of the balanced current flowing through the light receiving portion 15b of the photocoupler 15 can flow through each amplifier 32. For this reason, even when the current capacity that can flow through the light receiving portion 15b of the photocoupler 15 in each of the DC-DC converters A and B is small, or when a larger number (two or more) of DC-DC converters are operated in parallel,
Each DC-DC converter A, B or more DC-D
The respective output currents I _O of the C converter can always be well balanced. Further, the resistance 31 in each of the DC-DC converters A and B of the DC converter device shown in FIG.
FIG. 3 shows a DC converter device including the NP-type transistor 34. Further, the amplifiers 32 in the respective DC-DC converters A and B of the DC converter shown in FIG.
FIG. 4 shows a DC converter device composed of a transistor 34 and an NPN transistor 35. 3 and 4
In any case of the DC converter shown in FIG. 2, the same operation and effect as those of the DC converter shown in FIG. 2 can be obtained.

The embodiments of the present invention are not limited to the above embodiments, and various modifications are possible. For example, FIG.
In the embodiment shown in FIG. 3, a diode may be connected in place of the resistor 31 as in the embodiment shown in FIG. 3, and in the embodiment shown in FIG. 3, a resistor may be connected instead of the diode 33. Further, the resistor 31 may be omitted in the embodiment shown in FIG. The operations and effects obtained in any of the above cases are substantially the same as those of the embodiment shown in FIG. In each of the above embodiments, the case where a bipolar transistor is used as a switching element has been described.
(A field effect transistor), a thyristor, or the like can also be used. Also, in each of the above embodiments, the DC-DC converters A and B constituting the DC converter device are flyback type DC-DC converters. However, a forward type, a half-bridge type, a full-bridge type or It may be a DC-DC converter such as a push-pull type, and is not limited to these insulated DC-DC converters, and may be a non-insulated DC-DC converter such as a step-up chopper type or a step-down chopper type.
A converter may be used.

[0014]

According to the present invention, a plurality of DC-DC converters can be provided with a simple circuit configuration without using a special output current detection circuit.
Since the respective output currents of the DC converters can be balanced, the failure of the circuit of the output detection and control system is small, and the plurality of DC-DC converters can always be favorably operated in parallel. In particular, many (two or more) DC-DC
The effects of the present invention are remarkable when the converters are operated in parallel.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a DC converter device according to the present invention.

FIG. 2 is an electric circuit diagram showing a modified embodiment of the DC converter device shown in FIG.

FIG. 3 is an electric circuit diagram showing a modified embodiment of the DC converter device shown in FIG. 2;

FIG. 4 is an electric circuit diagram showing another modified embodiment of the DC converter device shown in FIG. 2;

FIG. 5 is an electric circuit diagram showing a conventional DC converter device.

FIG. 6 is a waveform chart showing voltages of respective parts in the circuit of FIG.

[Explanation of symbols]

1,2. . . 2. DC input terminal; . . DC power supply, 4,
5. . . DC output terminal, 6. . . Load, 7. . . Transformer, 7a. . . Primary winding, 7b. . . 7. secondary winding; . .
8. transistor (switching element); . . Rectifier diode, 10. . . 10. smoothing capacitor; . . 11. current detection resistor (current detection means); . . 12. output voltage detection circuit (output voltage detection means); . . Reference power supply, 1
4. . . 14. error amplifier; . . Photo coupler, 15
a. . . Light emitting section, 15b. . . Light receiving section, 16. . . Comparator, 17. . . Clock pulse generation circuit, 1
8. . . Latch circuit, 19. . . 20. current mode PWM control circuit, . . 21. output current detection resistor; . . Error amplifier, 22. . . Output current detection circuit, 23, 2
4. . . Backflow preventing diode, 31. . . Resistance, 3
2. . . Amplifier, 33. . . Diode (rectifier),
34. . . PNP transistor, 35. . . NPN transistors, A, B. . . DC-DC converter

Claims (3)

[Claims] At least one switching element for intermittently converting a DC input voltage of a DC power supply by an on / off operation to convert to a high-frequency power, and a rectifying and smoothing circuit for converting the high-frequency power to a DC output voltage to be supplied to a load. A current detecting means for detecting a current flowing through the switching element as a voltage corresponding thereto, and detecting the DC output voltage and comparing the detected voltage with a reference voltage for providing a reference value of the DC output voltage. Output voltage detection means for outputting an error signal, a voltage control signal based on the error signal of the output voltage detection means input to one control input terminal, and a detection voltage of the current detection means input to the other control input terminal Mode PW for comparing the ON / OFF periods of the switching elements according to their comparison outputs
A DC converter device comprising an M control circuit, and a plurality of DC-DC converters for supplying a constant-voltage DC output to the load by controlling on / off of the switching element and connected in parallel to the load. A DC converter device, wherein one control input terminal of the current mode PWM control circuit in each of the DC-DC converters is connected. 2. The DC converter according to claim 1, wherein one of the control input terminals of the current mode type PWM control circuit in each of the DC-DC converters is connected via a resistor. 3. A control input terminal of the current mode PWM control circuit in each of the DC-DC converters is connected via a parallel circuit of a resistor and an amplifier or a parallel circuit of a rectifier and an amplifier, respectively. 1. The DC converter device according to 1).