JPH1139044A - Power circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To flatten the voltage-current characteristics of the DC outputs of plural power circuits operating in parallel and to prevent sudden change of load voltage at the time of a reverse current preventing operation by detecting the potential difference of both terminals in a reverse current preventing element. SOLUTION: P channel MOS-FET 1 is used for the reverse current preventing element inserted into the +-side of a DC stabilization source 2. The voltage of the drain-side of P channel MOS-FET 1 is detected in resistances 3 and 4 and detection voltage Vd is generated. The voltage of the source-side of P channel MOS-FET 1 is detected in resistances 5 and 6 and detection voltage Vs is generated. An error amplifier 13 and resistances 11 and 12 control a transistor 10 with detection voltages Vs and Vd as inputs. Namely, the value of the gate voltage Vg of P channel MOS-FET 1 is changed by a transistor 9, a transistor 10 and resistances 7 and 8, which are the driving circuits of P channel MOS-FET 1. The on-resistance of P channel MOS-FET 1 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit used for an electronic device requiring parallel operation, and more particularly, to preventing a current from flowing into a power supply device in which an abnormality has occurred when an abnormality such as a short-circuit of an internal component occurs. The present invention relates to a technology effective when applied to a power supply circuit having a reverse current prevention element.

[0002]

2. Description of the Related Art In a conventional power supply circuit, when a plurality of power supply devices are connected in parallel to supply power to a load, an abnormality such as an output stop or the like occurs in a certain power supply device due to an internal component short circuit or the like. Then, a current flows from the power supply device that is operating normally to the power supply device in which the abnormality has occurred through the power supply line, thereby preventing a stable supply of voltage to the load.

Therefore, in a conventional power supply circuit that supplies power to a load by connecting a plurality of power supply units in parallel, a reverse current for preventing a reverse current from flowing from a power supply unit in normal operation to a power supply unit in which an abnormality has occurred is provided. It is common to provide a prevention element at the output of each power supply.

The operation of the reverse current prevention element in the conventional power supply circuit will be described below with reference to FIGS.

FIG. 3 is a diagram showing an outline of a conventional power supply circuit using a diode as a reverse current prevention element. As shown in FIG. 3, a conventional power supply circuit using a diode as a reverse current prevention element includes a plurality of power supply devices 21 connected in parallel,
6, the power supply 21 supplies power to the load 15 via a DC stabilized power supply 2 having an internal component 2a.
And a diode 20 which is a reverse current prevention element.

The "No. 1" power supply 21 in normal operation
Is configured to supply the output voltage Vo output from the stabilized DC power supply 2 to the power supply line 16 connected to the load 15 through the diode 20 as a reverse current prevention element.

[0007] Similarly, the other power supply device 21 also changes the output voltage Vo output from the stabilized DC power supply 2 during normal operation.
The power is supplied to the power supply line 16 connected to the load 15 through a diode 20 serving as a reverse current prevention element.

[0008] Here, for example, the power supply device 2 of "No. 1"
1 when the internal component 2a of the DC stabilized power supply 2 is short-circuited, the output voltage Vo of the DC stabilized power supply 2
Becomes 0 V, and the current tries to flow from the other power supply device 21 during normal operation to the power supply device 21 of “No. 1” through the power supply line 16.

However, since the diode 20 of the "No. 1" power supply 21 is in the opposite direction, the diode 20 functions as a reverse current prevention element, and the "No. 1" power supply 21
To prevent the generation of a reverse current in which a current flows to

As described above, the diode 20 has a reverse current preventing function of preventing the supply of a stable voltage from the other power supply device 21 to the load 15 during normal operation. When a large current is supplied from 2 to the load 15, the loss in the diode 20 increases.

When the diode 20 is used as the reverse current prevention element, even if the voltage-current characteristic of the DC stabilized power supply 2 at the preceding stage is flat, the diode characteristic is affected by the diode characteristic of the reverse current prevention element. The voltage on the feed line 16
Current characteristics deteriorate.

FIG. 4 shows a MOS-FET of a conventional power supply circuit.
FIG. 3 is a circuit diagram showing a power supply circuit having a reverse current prevention element.
As shown in FIG. 4, a conventional power supply circuit uses a MOS-FET 1 (Metal Oxi) to reduce loss in a reverse current prevention element.
de Semiconductor Field Ef
A plurality of power supply devices 34 are connected in parallel by using the power supply device 16, and the power supply device 34 supplies power to the load 15 via the power supply line 16.
A DC stabilized power supply 2 having an internal component 2a and a MOS-FET 1 as a reverse current prevention element are provided.

The "No. 1" power supply 34 in normal operation
Detects the output voltage Vo output from the stabilized DC power supply 2 by the resistors 30 and 31 and the comparison amplifier 33,
The transistor 9 and the resistors 7 and 8 which are the driving circuit of the ET1
, The gate voltage Vg of the MOS-FET 1 is set to Low to turn on the MOS-FET 1 as a reverse current prevention element, and power is supplied to the power supply line 16 connected to the load 15.

Similarly, the other power supply unit 34 turns on the MOS-FET 1 as a reverse current prevention element, and supplies the output voltage Vo output from the stabilized DC power supply 2 to the power supply connected to the load 15. It supplies to line 16.

When the internal component 2a of the stabilized DC power supply 2 of the power supply unit 34 of "No. 1" is short-circuited, the output voltage Vo starts to decrease and eventually becomes 0V.
is detected by the resistors 30 and 31 and the comparison amplifier 33, the MOS-FE is connected via the transistor 9 and the resistors 7 and 8 which are the driving circuit of the MOS-FET 1.
The T gate voltage Vg is set to High, and the M
OS-FET1 is turned off.

In this way, the turning off of the MOS-FET 1 prevents the occurrence of a reverse current in which a current flows into the power supply unit 34, and supplies the load 15 with another power supply unit 2 which is operating normally.
The supply of a stable voltage from 1 is performed.

[0017]

In a conventional power supply circuit, when a diode is used as a reverse current prevention element,
There is a problem that the loss in the diode is large.

Further, the voltage of the output of the DC stabilized power supply of the preceding stage-
Even if the current characteristics are flat, there is a problem that the voltage-current characteristics in the power supply line deteriorate as a result of being affected by the diode characteristics of the reverse current prevention element.

Further, when a MOS-FET is used as the reverse current prevention element, the MOS-FET in the ON state has a constant resistance value, so that the voltage increases as the current increases, and as a result, the voltage in the power supply line increases. There is a problem that the voltage-current characteristics deteriorate.

When a MOS-FET is used as the reverse current preventing element, the MO
Since current flows into the power supply during the switching time until the output voltage for turning off the S-FET is detected, a DC voltage drop occurs, resulting in a sudden change in the voltage of the power supply line.

An object of the present invention is to solve the above problems, to flatten the voltage-current characteristics of the DC output of a power supply circuit operated in parallel by a plurality of units, and to prevent a sudden change in load voltage during a reverse current prevention operation. Is to provide a possible technology.

[0022]

SUMMARY OF THE INVENTION The present invention relates to a power supply circuit for supplying power to a load by a plurality of power supply devices connected in parallel. It controls the operation.

The drive circuit of the power supply circuit according to the present invention detects the potential difference between both ends of the reverse current prevention element, and when the potential difference is generated so that the current flows from the DC stabilized power supply side to the load side, the reverse direction is detected. The normal operation is performed by turning on the current preventing element.

Here, when an abnormality such as a short-circuit of an internal component in the stabilized DC power supply occurs, current tries to flow from another power supply apparatus in normal operation to the power supply apparatus in which the abnormality has occurred.

Then, the potential difference between both ends of the reverse current preventing element changes to “0” or a direction in which current flows from the load side to the DC stabilized power supply side. Therefore, the drive circuit detects the change in the potential difference and performs the reverse operation. The current prevention element is turned off to perform a reverse current prevention operation.

Also, during normal operation of the power supply circuit of the present invention,
When the DC output current changes due to the load, the drive circuit detects a change in the potential difference between both ends of the reverse current prevention element, and changes the on-resistance of the reverse current prevention element in accordance with the detected change, and The voltage drop across the current prevention element is kept constant. Thereby, the voltage-current characteristics of the reverse current prevention element become flat.

As described above, according to the power supply circuit of the present invention,
Since the operation is controlled by detecting the potential difference between both ends of the reverse current prevention element, the voltage-current characteristics of the DC output of the power supply circuit operating in parallel with a plurality of units are flattened, and the load voltage during the reverse current prevention operation is reduced. It is possible to prevent sudden changes.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION A plurality of power supplies are connected in parallel to supply power to a load so as to prevent the occurrence of a reverse current when an abnormality such as an output stop occurs in a specific power supply. A power supply circuit according to the embodiment will be described.

FIG. 1 is a diagram showing a schematic configuration of the power supply circuit of the present embodiment. As shown in FIG. 1, the power supply circuit according to the present embodiment includes a plurality of power supply devices 14 connected in parallel,
6, the power supply 14 supplies power to the load 15 via a DC stabilized power supply 2 having an internal component 2a.
And a P-channel MOS-FET 1 serving as a reverse current prevention element
And

In the power supply circuit according to the present embodiment, the P-channel MO
Using the S-FET1, the voltage on the drain side of the P-channel MOS-FET1 is detected by the resistors 3 and 4, and the detected voltage Vd
Generate

The voltage on the source side of the P-channel MOS-FET 1 is detected by the resistors 5 and 6 to generate a detection voltage Vs, and the error amplifier 13 and the resistors 11 and 12 receive the detection voltages Vs and Vd as input transistors. 10 is performed.

That is, the value of the gate voltage Vg of the P-channel MOS-FET 1 is changed by the transistor 9, the transistor 10, and the resistors 7 and 8 which are the driving circuit of the P-channel MOS-FET 1.
1 is controlled.

Hereinafter, as the first stage of the power supply circuit of the present embodiment, the operation of the P-channel MOS-FET 1 as the reverse current prevention element when the power supply device 14 is operating normally will be described.

As a first step, when the power supply device 14 is operating normally, when the stabilized DC power supply 2 starts operating, the DC output voltage Vo passes through the load 1 through the body diode 1a.
5.

Since the power supply 14 is operating normally, the detection voltage Vd becomes higher than the detection voltage Vs as shown in Expression 1.

[0036]

Vd> Vs At this time, the voltage drop across the P-channel MOS-FET 1 can be obtained by the difference between the detection voltage Vd and the detection voltage Vs. As a result, the transistor 10 is driven, the gate voltage Vg is reduced, and the P-channel MOS-FET 1 is turned on.

[0037]

## EQU2 ## Va = A (Vd-Vs) The voltage drop Vx at the P-channel MOS-FET 1 at that time
Becomes as shown in Expression 3.

[0038]

Vx = Ron · Io As a second stage of the power supply circuit according to the present embodiment, a P-channel MOS when the DC output current Io changes due to the load 15 when the power supply device 14 is operating normally. -FET
1 will be described.

In the second stage, when the DC output current Io changes by ΔIo due to the load 15 during the normal operation of the power supply device 14, the equation 3 becomes the following equation 4, and the P-channel MOS-FET 1 The voltage drop between both ends changes.

[0040]

(Vx + ΔVx) = Ron · (Io + ΔIo) Further, since the detection voltage Vs also changes, Expression 2 becomes Expression 5 and the base voltage of the transistor 10 changes.

[0041]

Va + ΔVa = A (Vd− (Vs + ΔVs)) Therefore, the gate voltage Vg and the on-resistance Ron change.
Equation 4 becomes Equation 6, resulting in a P-channel MOS-FET
1 operates such that the voltage drop Vx across the terminals 1 is kept constant. Thereby, the voltage-current characteristics in the power supply line 16 become flat.

[0042]

## EQU00006 ## Vx = (Ron + .DELTA.Ron). (Io + .DELTA.Io) FIG. 2 is a diagram showing an outline of the voltage-current characteristics of the present embodiment. As shown in FIG. 2, the voltage-current characteristics of this embodiment are as follows.
When a diode 20 is used as a reverse current prevention element in a DC power supply output and a conventional power supply circuit, a MOS
-When the FET 1 is used and in the power supply circuit of the present embodiment, P
This shows voltage-current characteristics when the channel MOS-FET 1 is used.

In the power supply circuit of this embodiment, as described above, as a result, the voltage drop V across the P-channel MOS-FET 1
Since the operation is performed so that x is kept constant, the voltage-current characteristic in the power supply line 16 becomes flat as shown by the power supply output value 14x in FIG.

On the other hand, when the diode 20 is used as the reverse current prevention element in the conventional power supply circuit as shown in FIG. 3, not only the loss is large but also the voltage-current characteristic of the output of the DC stabilized power supply 2 in the preceding stage. Is flat as shown by the DC stabilized power supply output value 2x in FIG. 2, it is affected by the diode characteristics of the reverse current prevention element, and as a result, the voltage −
The current characteristics deteriorate as shown by the power supply output value 21x in FIG.

When the MOS-FET 1 is used as the reverse current prevention element in the conventional power supply circuit as shown in FIG. 4, the MOS-FET 1 in the ON state has a constant resistance value. The descent increases, and as a result, the feed line 16
The voltage-current characteristics at the point (1) deteriorate as shown by the power supply output value 34x in FIG.

Hereinafter, as a third stage of the power supply circuit according to the present embodiment, a P-channel MOS-type power supply in the case where the internal component 2a of the DC stabilized power supply 2 of the power supply 14 short-circuits and the power supply 14 becomes abnormal will be described. The operation of the FET 1 will be described.

In the third stage, the “No. 1” power supply device 14
When the output voltage Vo becomes 0 V due to an abnormality such as a short circuit of the internal component 2a of the DC stabilized power supply 2 of FIG.
o. The current tries to flow into the power supply 14 of "1",
At that time, since the DC output current Io of the power supply device No. 1 has not already flowed, the P-channel MOS-FET 1
No voltage drop occurs at both ends, and the state of Equation 7 or 8 is obtained.

[0048]

Vd = Vs

[0049]

Vd <Vs Because of this, the error amplifier output value Va of Expression 1 becomes “0” or “−”, so that the transistor 10 cannot be driven, and the gate voltage Vg becomes the same potential as the source voltage. , The P-channel MOS-FET 1 is turned off, and the reverse current preventing operation is performed without any switching time.

In the power supply circuit of the present embodiment, an example has been described in which a P-channel MOS-FET 1 is used as a reverse current prevention element. The same applies even if the element is inserted, and any element can be used as the reverse current prevention element as long as the element can be controlled linearly such as a bipolar transistor.

Further, when the device is used when the current capacity is large, more effects can be obtained by connecting a plurality of reverse current preventing elements in parallel.

Further, the power supply circuit of the present embodiment may be formed as an integrated circuit (hybrid IC, monolithic IC), or a DC obtained by rectifying an AC power supply may be used as a DC power supply.

As described above, according to the power supply circuit of the present embodiment, the potential difference between both ends of the reverse current prevention element is detected,
Since the operation is controlled, it is possible to flatten the voltage-current characteristics of the DC output of the power supply circuits operating in parallel by a plurality of units and to prevent a sudden change in the load voltage during the reverse current prevention operation.

[0054]

According to the present invention, since the potential difference between both ends of the reverse current prevention element is detected and its operation is controlled, the voltage-current characteristic of the DC output of the power supply circuits operating in parallel by a plurality of units is made flat. In addition, it is possible to prevent a sudden change in the load voltage during the reverse current prevention operation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a power supply circuit according to an embodiment.

FIG. 2 is a diagram showing an outline of a voltage-current characteristic of the present embodiment.

FIG. 3 is a diagram showing an outline of a conventional power supply circuit using a diode as a reverse current prevention element.

FIG. 4 is a circuit diagram showing a power supply circuit using a MOS-FET of a conventional power supply circuit as a reverse current prevention element.

[Explanation of symbols]

1a: body diode, 3-6: resistor, 10: transistor, 11 and 12: resistor, 13: error amplifier, 1
4 power supply device, 2 DC stabilized power supply, 2a internal components,
15 load, 16 feed line, 20 diode, 2
DESCRIPTION OF SYMBOLS 1 ... Power supply device, 1 ... MOS-FET, 7 and 8 ... Resistance,
9 ... transistors, 30 and 31 ... resistors, 33 ... comparative amplifiers, 34 ... power supply devices.

Claims (1)

[Claims] In a power supply circuit for supplying power from a plurality of power supply units connected in parallel, when an abnormality occurs in a specific one of the plurality of power supply units, an abnormality occurs from a power supply unit that is operating normally. A reverse current prevention element for preventing generation of a reverse current in which a current flows through the power supply device, and a drive circuit for detecting the potential difference between both ends of the reverse current prevention element and controlling the operation of the reverse current prevention element. Characteristic power supply circuit.