JPH06105464A - Parallel d.c. power supply circuit - Google Patents

Abstract

PURPOSE:To prevent a parallel D.C. power supply circuit from being affected by the voltage drop of an OR diode in a parallel D.C. power circuit which is provided with current and an extra DC/DC converter including a resistor circuit for detecting an output voltage used for the adjustment of an output voltage and also including an OR diode between a load and this circuit to prevent back flow to each other. CONSTITUTION:Each DC/DC converter 2 is provided with a voltage compensation circuit 1 in which the voltages of both terminals of an OR diode 3 connected on its own side are detected to compare them by magnitude and to parallelly connect a compensation resistor Rc in the part of a resistor circuit DR for detecting the output voltage of the DC/DC converter 2 on its own side and the other side, thereby compensating for the voltages of both terminals to be equal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel DC power supply circuit, and more particularly to a parallel DC power supply circuit having working and spare DC / DC converters.

As a power source used for an exchange or the like, a plurality of power sources are connected in parallel according to the load capacity on the output side to supply the load. At this time, as a countermeasure against a failure of a plurality of power supplies connected in parallel, one extra power supply is added.

For example, as a power source for an exchange, a -48V DC power source is converted into a ± 5V or -2V DC power source by a DC / DC converter and supplied to an electronic circuit such as an LSI. At that time, when the load capacity is 10A, two 10A capacity power supplies are connected in parallel as a power supply device, or three 5A capacity power supplies are connected in parallel, and one of them is allocated as a standby power supply. , The load side is not affected when the working power supply fails or is replaced.

In the direct current power supplies connected in parallel as described above, diodes are connected in parallel with each other for the purpose of preventing backflow from the output side, and a diode or circuit spills over to the other power supply at the time of failure occurrence or restoration. Furthermore, the influence of the overvoltage protection circuit on the other side when the output voltage rises above the standard is prevented.

Therefore, the diode-OR circuit is indispensable for the operation of the parallel power supply circuit.

[0006]

2. Description of the Related Art FIG. 8 shows a connection structure of a conventional parallel DC power supply circuit having the above diode / OR circuit. In the figure, 21 is a working DC / DC converter (# 1) and 22 is a backup DC / DC converter (# 2), which have the same circuit configuration. In each DC / DC converter, 23 is a switching transistor, 24 is a voltage conversion transformer, 25 is a rectifying / smoothing circuit, and 26 is a control circuit.

Further, 27 is a diode OR circuit provided with diodes 31 and 32, which is a DC / DC converter 21,
It is inserted as a backflow prevention circuit for 22.

In the operation of each of the DC / DC converters 21 and 22, the input power (DC-48V) is converted into an alternating current by turning on / off the switching transistor 23, and the conversion transformer 24
The output voltage stepped down by is converted into a DC voltage by the rectifying / smoothing circuit 25 and ± 5 V is supplied to the load 4.

The output voltage of the DC / DC converters 21 and 22 is compared with a reference voltage (not shown) by the control circuit 26 to adjust the on / off ratio of the switching transistor 23 so that the output voltage falls within the standard. To be adjusted automatically.

The diode-OR circuit 27 prevents the power source of its own from detecting overvoltage when the output of the other power source circuit which is operated in parallel rises, and is also connected in parallel when the load is moving. This is to prevent inrush current from flowing even when the power supply circuit for operation is inserted into the device.

[0011]

If the capacity of the power supply circuit is 5V10A, the OR diodes 31 and 32 used in the diode OR circuit 27 have a voltage drop of about 5V10A. About 0.5 V,
It reaches 1/10 of the output voltage. When the output voltage is 2V, the voltage drop of 0.5V becomes 1/4 of the output voltage.

In the above conventional circuit, the control circuit 26 is
Since the output voltage V ₀₁ is detected on the anode side of the diodes 31 and 32, the voltage V ₀₂ actually applied to the load 4 is reduced by the voltage drop V _F generated in the OR diodes 31 and 32 ( V ₀₂ = V ₀₁ -V _F) and made to become. Further, since this voltage drop V _F greatly varies depending on the output current I ₀ , there is a problem that the output accuracy is greatly affected.

Therefore, the present invention comprises working and backup DC / DC converters each having an OR diode between them and a load for preventing backflow and having an output voltage detecting resistor circuit used for adjusting an output voltage. It is an object of the present invention to prevent the parallel DC power supply circuit from being affected by the voltage drop of the OR diode.

[0014]

In order to achieve the above object, the parallel DC power supply circuit according to the present invention, as shown in principle in FIG. A voltage correction circuit that detects the voltage across the diode 3, compares the magnitudes, and connects a correction resistor Rc in parallel with a part of the output voltage detection resistor circuit on its own side to correct the voltage across the diode 3 to be equal. 1 is provided.

Further, according to the present invention, one of the DC / DC converters detects the voltage across the OR diode 3 on its own side and compares the detected voltages, and compares the output voltage detection resistance circuit DR of the other DC / DC converter. It is also possible to provide a voltage correction circuit 1 in which a correction resistor Rc is connected in parallel as shown by a dotted line and a voltage is corrected so that the voltages at both ends become equal.

Further, in the present invention, the voltage correction circuit 1 has the amplifier 5 for comparing the magnitudes, and is provided between the input / output terminals of the amplifier 5 or between the output terminal of the amplifier 5 and the correction resistor Rc. A backflow prevention diode can be connected.

[0017]

The operation of the parallel series power supply circuit according to the present invention shown in FIG.
The operation will be described with reference to FIG. In addition, FIG.
・ For forward voltage drop correction of diode 3 (V₀₁> V
₀₂(In the case of), the figure (b) is when the voltage of the opposite side power supply circuit rises
In case of (V₀₁<V₀₂When).

Forward voltage drop V of the OR diode 3_F
In the case of correction, the voltage on the anode side of the OR diode 3
Is larger than the voltage on the cathode side, the voltage correction circuit 1
Is V ₀₁> V₀₂1 and is schematically shown in FIG.
As shown in FIG. 2A, the correction resistor Rc detects the output voltage.
The switching circuit is connected in parallel with the output resistance circuit DR.

The parallel connection in this case means that when the output voltage detecting resistor circuit DR is a series circuit of resistors R1 and R2 as shown in the figure, the resistor R2 and the resistor Rc in the lower part are connected in parallel. Since the resistance value of is decreased, the output value for voltage adjustment is decreased.

On the other hand, when the voltage of the DC / DC converter on the opposite side rises, the voltage on the cathode side of the OR diode 3 becomes larger than the voltage on the anode side, and the voltage correction circuit 1 becomes V
It is determined that ₀₁ <V ₀₂ is shown in FIG.
As shown in (b), the resistor R1 and the resistor Rc in the upper part of the output voltage detecting resistor circuit DR are connected in parallel. Therefore, the output value for voltage adjustment increases.

As described above, the output value for voltage adjustment to each DC / DC converter is decreased or increased, whereby DC / D
The C converter controls so that its own output voltage becomes equal to the output voltage of the opposite DC / DC converter.

In the present invention, the voltage on both sides of the OR diode 3 is monitored by the voltage correction circuit 1 to adjust the output voltage of the DC / DC converter on the side of the OR diode. Reference numeral 1 is not a DC / DC converter on its own side, but a correction resistor Rc is connected in parallel to the output voltage detection resistor circuit DR of the opposite DC / DC converter so that the voltages across the OR diode 3 become equal. You may

However, the voltage correction circuit 1 in this case is shown in FIG.
It is the opposite of each case shown in (a) and (b), and V
₀₁ <For V ₀₂ connected in parallel to the output voltage detecting resistor circuit DR correction resistor Rc as shown in FIG. (A), V _01>
In the case of V ₀₂ , it is connected in parallel as shown in FIG.

The voltage correction circuit 1 has the amplifier 5 for comparing the magnitudes, and is provided for preventing backflow between the input / output terminals of the amplifier 5 or between the output terminal of the amplifier 5 and the correction resistor Rc. By connecting the diodes, even if the output voltage of one DC / DC converter increases abnormally, it is possible to prevent the output of the other DC / DC converter from being affected.

[0025]

EXAMPLE FIG. 3 shows an example of a positive output voltage of a parallel DC power supply circuit according to the present invention. In this example, + 5V is used.
It is used as an output circuit. In the figure, the voltage correction circuit 1 is
Voltage dividing resistors R11 to R14 for detecting the voltage across the diode 31 in the OR diode 3 and resistors R11 and R12
The non-inverting input terminal is connected to the connection point with and resistors R13 and R14
The inverting input terminal is connected to the connection point with the resistor R15, and the resistor R16 is connected between the output terminal and the inverting input terminal, and the output terminal of this amplifier 5 It is composed of the connected correction resistor Rc. Incidentally, C
Reference numerals 1 and C2 are capacitors connected in parallel with the resistors R12 and R14 to bypass the AC component.

Reference numeral 12 is a control circuit included in the DC / DC converter 2 for adjusting the output voltage of the DC / DC converter 2.
A resistance circuit DR for detecting the output voltage of the DC converter 2 is formed, and resistors R1 and R2, to which the above-mentioned correction resistor Rc is connected, and a non-inverting input terminal are connected to the connection points of these resistors R1 and R1. And an amplifier (AMP2) 7 whose inverting input terminal is connected to a reference power source (V _REF ) 10 to generate a voltage regulated output.

In the illustrated example, DC / on one side (currently used)
Only the DC converter is shown, V ₀₁ is the anode side voltage of the OR diode 31, V ₀₂ is the cathode side voltage of the OR diode 31, and V _F is the OR diode as described above.
31 is the forward voltage drop, and I ₀ is the load current.

In the operation of this embodiment, when the forward voltage drop of the diode 3 is corrected as shown in FIG. 2A (when V ₀₁ > V ₀₂ ), the connection point voltage between the resistors R11 and R12 and the resistor Since the connection point voltage between R13 and R14 is given to the amplifier 5, the output voltage of the amplifier 5 is connected to the negative voltage (-), and the correction resistor Rc is connected to the resistor R2 of the output voltage detecting resistor circuit DR. It will be connected in parallel.

As a result, the output voltage (voltage adjustment output) V _CONT of the amplifier 5 is given by the following equation.

[0030]

[Equation 1]

Therefore, when the DC / DC converter 2 is controlled, the output voltage V _CONT becomes "0", so that the output voltage V ₀₁ is corrected by the following equation.

[0032]

[Equation 2]

On the other hand, when the output voltage of the opposite DC / DC converter 2 on the redundant side rises, as shown in FIG. 2B, the correction resistor Rc becomes the output voltage detection resistor R1. It will be connected in parallel.

As a result, the output voltage V ₀₁ is corrected by the following equation.

[0035]

[Equation 3]

When the above equations are compared with each other, since the numerator is the same and the denominator is larger than the equation, in the case of the equation, the output voltage of the amplifier 5 is the reference voltage V _REF.
Since the output voltage of the amplifier 5 becomes a voltage higher than the reference voltage V _{REF in} the case of the formula,
In the case of (a), the forward voltage drop of the diode 31 can be corrected, and in the case of FIG. 2 (b), the output voltage when the redundant voltage is increased can be decreased.

FIG. 4 corresponds to the case of a negative output voltage, whereas the embodiment shown in FIG. 3 corresponds to a case of a positive output voltage. For example, the embodiment shown in FIG. 4 is used, but the polarities of the diodes 31 and 32 forming the OR diode 3 are reversed.

In the embodiments shown in FIGS. 3 and 4, when the output voltage of the DC / DC converter 2 connected in parallel rises abnormally, the output voltage of the first amplifier 5 of the voltage correction circuit 1 becomes It is necessary to prevent it from rising above a certain voltage.

Therefore, as shown in the embodiment of FIG. 5 (a), the diode D1 may be connected in parallel with the resistor R16 connecting the inverting input terminal and the output terminal of the amplifier 5 for backflow prevention. preferable.

Alternatively, as shown in FIG. 7B, the diode D1 may be inserted between the output terminal of the amplifier 5 and the correction resistor Rc for backflow prevention.

The static characteristics of the output voltage and the output current in the embodiment for the positive output voltage of FIG. 3 are shown in FIG.
The difference in correction characteristics between the case where the voltage correction circuit 1 is added and the case where it is not added is shown.

In the figure, the relationship between the output current I ₀ (A) and the output voltage V ₀ (V) is the output voltage due to the voltage drop before and after the OR diode 3 in the conventional case where the voltage correction circuit 1 is not provided. Although there is a difference, it can be seen that when the voltage correction circuit 1 is added, the fluctuation of the output voltage is almost corrected.

Also, in the embodiment of FIG.
Figure 7 shows the output voltage characteristics when the
Externally applied voltage V from the connected power supply circuit₂And or da
Output voltage V on the side of the ion 3₁The relationship with
Pressure V₂Output voltage V ₁Even if the above
There is a slight voltage drop due to the addition of positive circuit 1.
It can be seen that there is no abrupt change due to the shock.

The correction resistor Rc of the voltage correction circuit is not the DC / DC converter on its own side, but the opposite resistance Dc.
Even when connected to the output voltage detecting resistance circuit in the control circuit of the C / DC converter, the same voltage control operation can be performed by replacing the input terminals of the amplifier 5.

[0045]

As described above, according to the parallel DC power supply circuit of the present invention, each DC / DC converter detects the voltage between both ends of the OR diode on its own side and compares them to determine the magnitude. Since a voltage correction circuit for correcting the output voltage detection resistance circuit of the DC side or the other side of the output voltage detection resistance circuit in parallel is provided with a correction resistance so that the voltages at both ends become equal, a parallel power supply is provided. The voltage drop of the OR diode in the output circuit can be automatically corrected and the output fluctuation is suppressed and the output accuracy is improved.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a parallel DC power supply circuit according to the present invention.

FIG. 2 is an operation explanatory diagram of a parallel DC power supply circuit according to the present invention.

FIG. 3 is a circuit diagram showing an embodiment (for positive output voltage) of a parallel DC power supply circuit according to the present invention.

FIG. 4 is a circuit diagram showing an embodiment (in the case of a negative output voltage) of a parallel DC power supply circuit according to the present invention.

FIG. 5 is a circuit diagram showing another embodiment of the voltage correction circuit used in the parallel DC power supply circuit according to the present invention.

FIG. 6 is a static characteristic graph diagram of output voltage and output current of the present invention and a conventional example.

FIG. 7 is a graph showing output characteristics of the present invention and a conventional example when an externally applied voltage is applied by a parallel power supply circuit.

FIG. 8 is a circuit diagram showing a conventional configuration example.

[Explanation of symbols]

 1 voltage correction circuit 2 DC / DC converter 3 (31, 32) OR diode 4 load 5 first amplifier 7 second amplifier 12 control circuit DR output voltage detection resistance circuit Rc correction resistance Or, shows a considerable portion.

Claims (4)

[Claims] 1. An OR for preventing backflow from each other
In a parallel DC power supply circuit having working and backup DC / DC converters having a diode (3) between a load (4) and an output voltage detecting resistor circuit (DR) used for output voltage adjustment, each DC In the / DC converter, the voltage across the OR diode (3) on the self side is detected, the magnitudes are compared, and a correction resistor (Rc) is provided in a part of the output voltage detection resistor circuit (DR) on the self side. A parallel DC power supply circuit comprising a voltage correction circuit (1) which is connected in parallel to correct the voltages of both ends to be equal. 2. An OR for preventing backflow from each other
In a parallel DC power supply circuit having working and backup DC / DC converters, which has a diode (3) between a load (4) and an output voltage detection resistance circuit (DR) used for output voltage adjustment, In the DC / DC converter, the voltage across the OR diode (3) on its own side is detected, the magnitudes are compared, and a correction resistor is used as a part of the output voltage detection resistor circuit (DR) of the other DC / DC converter. A parallel DC power supply circuit comprising a voltage correction circuit (1) for correcting (Rc) in parallel so that the voltages across the terminals are equal. 3. The voltage correction circuit (1) has an amplifier (5) for comparing the magnitude, and a backflow prevention diode is connected between the input and output terminals of the amplifier (5). The parallel DC power supply circuit according to item 1 or 2. 4. The voltage correction circuit (1) has an amplifier (5) for comparing the magnitude, and a backflow prevention diode is provided between the output terminal of the amplifier (5) and the correction resistor (Rc). The parallel DC power supply circuit according to claim 1 or 2, wherein the parallel DC power supply circuit is connected.