JPH07281766A - Power supply device - Google Patents

Abstract

PURPOSE:To improve efficiency and reliability at the time of a parallel operation. CONSTITUTION:An output current Io of a power supply is detected by a resistor 14. Corresponding to the output current Io, a comparator 15 turns on/off an FET11. When the power supply is normal, the FET11 is turned off, and the output current Io is supplied to a load 2. On the other hand, when the power supply is abnormal, the FET11 is turned off, and a reverse current is prevented from flowing in. Thus, when the power supply is normal, no voltage drop occurs at an output voltage line.

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 capable of parallel operation by a plurality of power supply main bodies, and more particularly to a power supply device intended to improve efficiency and reliability during parallel redundant operation.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram of a power supply device in a general parallel operation.
1 ... 1n + 1 is a power supply main body incorporating a DC-DC converter (not shown) having a feedback loop.
1 ... 1n + 1 can supply a stable DC output voltage Vo to the load 2 from the output terminals + V and -V. Even if one of the power source bodies 11 ... 1n + 1 fails, these power source bodies 11 ...
In order to supply electric power to the load 2 by 1 ... 1n, n + 1 power supply main bodies 11 ... 1n + 1 are connected in parallel to the load 2 in advance to perform so-called parallel redundant operation. Also, 31 ... 3n + 1 is a diode for preventing backflow, which is inserted and connected to the output voltage line of each power supply main body 11 ... 1n + 1, whereby any one of the power supply main bodies 11 ... 1n + 1 fails. Even so, the power supply body 11 ... 1n + that caused this abnormality
It is possible to prevent the current from flowing into 1, so that the load 2 and other normal power supply bodies 11 ... 1n are not affected.

[0003]

In the above-mentioned conventional parallel redundant operation, since the diodes 31 ... 3n + 1 are connected to the output voltage lines of the respective power source bodies 11 ... 1n + 1, the diodes 31 ... 3n + 1 are connected. A forward voltage drop is unavoidable when an output current flows through. Therefore, these diodes 31 to 3n + 1 always cause power loss proportional to the output current, resulting in a decrease in efficiency and a decrease in reliability due to heat generation.

In view of the above problems, it is an object of the present invention to provide a power supply device capable of improving efficiency and reliability during parallel operation.

[0005]

A power supply device of the present invention is a power supply device in which a plurality of power supply bodies for supplying a predetermined output voltage from an output terminal are connected in parallel, and is connected to an output voltage line of the power supply body. MOS FET for backflow prevention
And a current detection circuit for detecting the output current of the power source main body and turning off the MOS type FET when the power source main body is abnormal based on the detection result. in this case,
A current detector in which the current detection circuit is connected to the output voltage line, resistors for voltage division connected in series connected to both ends of the current detector, and a voltage level at a connection point of these resistors. It is preferable that the power supply main body is configured with a comparator for judging abnormality of the power supply body.

[0006]

With the above configuration, when the plurality of power supply main bodies operate in parallel, the output current from a certain power supply main body falls below a predetermined level, and when the current detection circuit detects a failure of this power supply main body, the MOS type FET is forced. To prevent reverse current from flowing into the failed power supply unit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Figure 1 shows the overall configuration of the power supply,
In FIG. 3, the power supply main body 11 which supplies a predetermined DC output voltage Vo from the output terminals + V and -V is the same as each power supply main body 11 ... 1n + 1 in the conventional example, and although not shown in FIG. As shown in FIG. 5, the other power supply main bodies 12 ... 1n + 1 are also connected in parallel to the load 2 so that parallel redundant operation is possible. Reference numeral 11 is a MOS type FET for preventing reverse current, which is inserted and connected to the output voltage line between the positive side output terminal + V of the power supply body 11 and the load 2, and the anode on the source side between the drain and source of this FET 11. There is a body diode 12 to which is connected. Also, 13 is a power supply main body 11
Resistor 14 which is a current detector for detecting the output current Io of the power source 1 and the voltage drop generated across the resistor 14
1 is a current detection circuit that includes a comparator 15 that detects a failure and turns off the FET 11 when a reverse current occurs in the output voltage line. The resistor 14 is a negative output terminal -V of the power supply body 11 and the load 2 It is inserted and connected to the voltage line between and. Between one end of the resistor 14 and the output voltage line connected to the positive side output terminal + V of the power supply body 11,
A series circuit of voltage dividing resistors 16 and 17 is connected,
Between the other end of the resistor 14 and the output voltage line connected to the positive side output terminal + V of the power supply body 11, the resistor 1 for voltage division is also provided.
A series circuit of 8 and 19 is connected. The connection point of the resistors 16 and 17 is connected to the inverting input terminal of the comparator 15, while the connection point of the resistors 18 and 19 is connected to the non-inverting input terminal of the comparator 15. The output terminal of the comparator 15 is F
It is connected to the gate of ET11, but the operating voltage V supplies the operating voltage Vcc to the gate of this FET11 and the comparator 15.
A resistor 20 is connected to the cc line. The ground of the comparator 15 is connected to the connection point between the other end of the resistor 14 and the load 2. In the current detection circuit 13 of this embodiment, in order to reliably turn on the FET 11,
It is necessary to make the operating voltage VCC higher than the voltage value obtained by adding the gate-source voltage of the FET 11 to the output voltage Vo. Further, the resistance values of the resistors 16 to 19 are determined so that the voltage level of the non-inverting input terminal of the comparator 15 is higher than the voltage level of the inverting input terminal when the power supply body 11 is normal. In this case, if the resistance values R1 of the resistors 16 and 18 are set to be the same, the ON / OFF operating points of the FET 11 can be changed by simply adjusting the resistance value R2 of the other resistor 17 and the resistance value R3 of the resistor 19. It can be changed easily.

Next, the operation of the above structure will be described. When the power supply main bodies 11 ... 1n + 1 are operated in parallel,
When the power supply body 11 is normal, the output current Io flows from the load 2 toward the minus side output terminal -V, so that the resistance 17
Is higher than the voltage level at one end of the resistor 14 connected to
The voltage level at the other end of the resistor 14 connected to 19 becomes high. Then, the voltage level of the non-inverting input terminal of the comparator 15 becomes higher than the voltage level of the inverting input terminal, and the output terminal of the comparator 15 becomes H level, so that F
To ET11, an operating voltage Vcc sufficient to turn on the source and drain of the FET11 is supplied to the gate, and from the positive side output terminal + V of the power supply device 11 to the output terminal + V.
→ FET11 (or body diode 12) → Load 2
→ The resistance 14 → The output current Io is supplied through the path of the output terminal -V.

On the other hand, when the power supply device 11 fails for some reason, the supply of the output current Io is stopped, and a current in the opposite direction to the output current Io is generated in the output voltage line, the resistance 19 The voltage level at one end of the resistor 14 connected to the resistor 17 is higher than the voltage level at the other end of the resistor 14 connected to. Therefore, this time, the voltage level of the inverting input terminal of the comparator 15 becomes higher than the voltage level of the non-inverting input terminal, and the output terminal of the comparator 15 immediately becomes L level.
Then, the FET 11 is turned off and the FET 11 is turned off, so that the reverse current is prevented from flowing into the output terminal + V of the failed power supply body 11. In this case, the load 2 is continuously supplied with electric power from the n power source bodies 12 ... 1n + 1 excluding the failed power source body 11.

In the above series of operations, the comparator 15
The abnormality determination of the power source body 1 by means of the above depends on the resistance values R1 to R3 of the resistors 16 to 19. That is, as shown in FIG.
If resistors 16 and 18 are set to the same resistance value R1, resistor 17
The resistance value R2 of R1 and the resistance value R3 of resistor 19 are the same (R2 = R
When set to 3), when the output current Io becomes zero,
The FET11 is switched on and off. Further, the resistance value R2 of the resistor 17 is larger than the resistance value R3 of the resistor 19 (R2> R3
) If set, before the output current Io becomes zero, FET11
Is switched on and off. In this case, the power loss of the body diode 12 can be reduced by setting the resistance values R2 and R3 of the resistors 17 and 19 so that the FET 11 is switched on and off when the output current Io is relatively small.

As described above, in the power supply device of the above embodiment, a plurality of power supply main bodies 11 ... 1n + 1 for supplying a predetermined output voltage Vo from the output terminals + V and -V are connected in parallel. In the connected power supply device, a backflow preventing MOS type FET 11 connected to the output voltage line of the power supply main body 11,
A current detection circuit 13 for detecting the output current Io of the power supply main body 11 and turning off the MOS type FET 11 when the power supply main body 11 is abnormal based on the detection result is provided. That is,
By combining the FET 11 and the current detection circuit 13, it is possible to surely prevent the reverse current from flowing into the power supply body 11 that has caused an abnormality, and also to turn on the FET 11 when the power supply body 11 is in a normal state and to use the diode as in the conventional case. Since the output current Io can be supplied to the load 2 side without causing a forward voltage drop, it is possible to improve efficiency and reliability during parallel operation.

According to the second embodiment, the current detecting circuit 13 is connected in series with the resistor 14 as the current detector connected to the output voltage line and the resistor 14 connected at both ends of the resistor 14, respectively. And resistors 16 and 17 and resistors 18 and 19 for voltage division, and a comparator 15 that determines an abnormality of the power supply main body 11 based on the voltage level at the connection point of these resistors 16 and 17 and resistors 18 and 19. From the resistance value R of each resistor 16 to 19
By simply adjusting 1 to R3 as appropriate, the threshold value for the abnormality determination of the power supply body 11 can be easily determined.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention. For example, the current detection circuit 13 can be modified in various ways, and a current transformer having a small loss can be used instead of the resistor 14 as the current detector.

[0014]

According to the present invention, in a power supply device in which a plurality of power supply main bodies for supplying a predetermined output voltage from an output terminal are connected in parallel, a backflow prevention MOS FET connected to the output voltage line of the power supply main body. And a current detection circuit that detects the output current of the power supply main body and turns off the MOS type FET when the power supply main body is abnormal based on the detection result, and improves efficiency and reliability during parallel operation. It is possible to provide a power supply device capable of doing so.

Further, according to the present invention, a current detector in which the current detection circuit is connected to the output voltage line, resistors for voltage division connected in series connected to both ends of the current detector, and each of these resistors are connected. It is composed of a comparator for judging the abnormality of the power supply body based on the voltage level of the connection point of the resistor, and by just adjusting the resistance value of each resistor appropriately, the threshold value for the abnormality judgment of each power supply body can be set. It is possible to set easily.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a power supply device showing an embodiment of the present invention.

FIG. 2 is a graph showing operating points of the same comparator.

FIG. 3 is a circuit diagram of a conventional power supply device.

[Explanation of symbols] 11 Power supply body 11 MOS type FET 13 Current detection circuit 14 Resistance (current detector) 15 Comparator 16, 17, 18, 19 resistance + V, -V output terminal

Claims (2)

[Claims] 1. A power supply device in which a plurality of power supply bodies for supplying a predetermined output voltage from an output terminal are connected in parallel, and a backflow prevention MOS type FET connected to an output voltage line of the power supply body and the power supply. The output current of the main body is detected and, based on the detection result, the MOS
And a current detection circuit for turning off the FET. 2. A current detector in which the current detection circuit is connected to the output voltage line, resistors for voltage division connected in series connected to both ends of the current detector, and connections of these resistors. The power supply device according to claim 1, wherein the power supply device is configured by a comparator that determines an abnormality of the power supply body based on a voltage level at a point.