JP3395735B2 - DC power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply device for supplying a large capacity DC power supply by connecting a plurality of DC power supply circuits in parallel.

[0002]

2. Description of the Related Art In recent years, a plurality of DC power supply circuits (hereinafter referred to as "DC / D
It is becoming mainstream to configure a DC power supply device by connecting C converters) in parallel.

FIG. 5 is a diagram showing an example of the configuration of a conventional DC power supply device. In the direct-current power supply device shown in the figure, the positive terminal of the DC / DC converter 1 and the anode terminal of the diode 5 are connected via a positive power supply line, and the positive terminal of the DC / DC converter 2 and the anode of the diode 6 are connected. The terminals are connected to each other via the positive power supply line, and the power supply lines connecting the cathode terminals of the diodes 5 and 6 and one terminal of the load 9 are connected to each other via the common output terminal 7. There is. The other terminal of the load 9 is the common output terminal 8
Via the negative side power supply line to the negative terminals of the DC / DC converters 1 and 2, respectively. The control circuits 3 and 4 detect the voltage levels output from the positive terminals of the DC / DC converters 1 and 2, respectively, and transmit control signals for controlling the voltage levels to the DC / DC converters 1 and 2, respectively. It is supposed to do.

In such a DC power supply device, DC
The / DC converters 1 and 2 are adapted to supply DC power supplies of the same level, and the respective DC power supplies are superimposed via the diodes 5 and 6 and supplied to the load 9.

The diodes 5 and 6 are provided in this way when, for example, when a short circuit or the like occurs due to loss of some of the components inside the DC / DC converter, the DC / DC converter is A DC current output from a normally operating DC / DC converter is prevented from flowing backward to the positive terminal of the DC converter, and a reverse current that causes a DC current to be output from the negative terminal is generated due to the reverse current. This is to prevent

[0006]

By the way, in the diodes 5 and 6, a power loss occurs due to the flow of a current. For this reason, the efficiency of the DC power supply is reduced.

Therefore, it is conceivable to use a field effect transistor having a large input impedance and almost no power loss, instead of the diode. However, when a reverse current flows, the field effect transistor may be damaged. there were.

The present invention has been made in view of the above, and an object thereof is to provide a DC power supply device capable of preventing backflow of current and damage of a field effect transistor.

[0009]

In order to achieve the above object, a direct-current power supply device according to the present invention connects positive power supply lines of a plurality of direct-current power supply circuits, and also connects negative power supply lines. In a DC power supply device that supplies DC power in parallel, the source terminal and drain terminal are connected by inserting into the positive or negative power supply line of each DC power supply circuit, and the gate terminal is connected to the other power supply line. A field effect transistor connected to the power supply line, a backflow detection unit that detects a backflow of a current flowing through the power supply line, and a gate voltage that shuts off the gate voltage supplied to the gate terminal when the backflow of the current is detected. The gist is to have a blocking means.

According to the present invention, when the reverse current is detected by the reverse current detecting means, the gate voltage interruption means inserts it into either the positive side or the negative side of the power source line and the source terminal. By blocking the gate voltage supplied to the field effect transistor to which the drain terminal and the drain terminal are connected, the field effect transistor is made non-conductive to prevent backflow of the current flowing through the power supply line and damage the field effect transistor. I try to prevent it.

Here, the backflow detecting means may detect the backflow by the potential difference between the source terminal and the drain terminal, or the resistance may be applied to at least one of the positive and negative power supply lines. May be provided, and the backflow may be detected based on the direction of the current flowing through the resistor.

The gate voltage cutoff means may cut off the gate voltage by short-circuiting the gate terminal and the source terminal, or may open and close the connection line connecting the gate terminal and the power supply line. The gate voltage may be cut off by providing a switch means and opening the connection line.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments to which the present invention is applied will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a diagram showing a configuration of a DC power supply device according to a first embodiment. As a feature thereof, the diodes 5 and 6 shown in FIG. 5 are replaced with the reverse current blocking circuits 11 and 12, and the reverse current blocking circuits 11 and 12 prevent the current from flowing back to the DC / DC converter 1 or 2. Especially. In FIG. 1, a battery 10 is provided as an emergency power source when the DC / DC converter 1 or 2 is stopped, and its positive terminal is connected to a common output terminal 7 and its negative terminal. Are connected to the common output terminal 8.
In addition, in addition, the same components as those in FIG. 5 are denoted by the same reference numerals.

In the reverse current blocking circuit 11, one terminal of the resistor R1 and the resistor R2 is connected to the positive power supply line, and the drain terminal of the field effect transistor Q1 is DC /.
The negative terminal of the DC converter 1, the source terminal thereof are connected to the common output terminal 8, and the gate terminal thereof is connected to the other terminal of the resistor R1. The anode terminal of the diode D1 is connected to the source terminal of the field effect transistor Q1, and the cathode terminal is connected to the drain terminal. The collector terminal of the bipolar transistor Q2 is connected to the gate terminal of the field effect transistor Q1, the emitter terminal is connected to the source terminal of the field effect transistor Q1, and the gate terminal is connected to the other terminal of the resistor R2. Bipolar transistor Q
The base terminal and collector terminal of 3 are connected to a connecting line connecting the base terminal of the bipolar transistor Q2 and the resistor R2, and the emitter terminal is connected to the drain terminal of the field effect transistor Q1. Here, the bipolar transistor Q
An npn type transistor is used for 2 and Q3. The configuration of the backflow blocking circuit 12 is the same as that of the backflow blocking circuit 11, and therefore the description thereof is omitted here.

Next, the operation of such a DC power supply device will be described. The operations of the DC / DC converter 2 and the reverse current blocking circuit 12 are similar to the operations of the DC / DC converter 1 and the reverse current blocking circuit 11, so here, the operations of the DC / DC converter 1 and the reverse current blocking circuit 11 are mainly described. explain.

During normal time when the current is flowing in the normal direction, the direct current output from the positive terminal of the DC / DC converter 1 flows to the load 9 and the battery 10 and passes through the diode D1 to the DC / DC converter. 1 is input to the negative terminal of No. 1 and DC power is supplied to the load 9 and the battery 10.

In such a state, the potential of the drain terminal of the field effect transistor Q1 becomes lower than the potential of the source terminal thereof, and the voltage applied between the base and emitter of the bipolar transistor Q2 becomes equal to that of the bipolar transistor Q3. It is smaller than the voltage applied between the base and emitter by the voltage between the drain and source of the field effect transistor Q1. Therefore, the bipolar transistor Q3 is connected via the resistor R2 connected to the positive power supply line.
Current is supplied to the bipolar transistor Q3 so that the bipolar transistor Q3 becomes conductive and the bipolar transistor Q2 becomes non-conductive. When the bipolar transistor Q2 is off, a gate voltage is supplied to the gate terminal of the field effect transistor Q1 via the resistor R1 connected to the positive power supply line. As a result, the field effect transistor Q1 becomes conductive, and the current from the load 9 is divided into the diode D1 and the field effect transistor Q1 to flow, and the power loss is reduced.

On the other hand, since damage etc. occurs inside the DC / DC converter 1, the DC / DC converter 1
2 and the output voltage of 2 is different, DC / DC converter 2
The output current from the positive terminal of the
When a backflow that flows into the positive terminal of the C / DC converter 1 occurs, the potential of the drain terminal of the field effect transistor Q1 becomes higher than the potential of the source terminal. At this time, the base of the bipolar transistor Q2
The voltage applied between the emitters becomes larger than the voltage applied between the base and the emitter of the bipolar transistor Q3, and as a result, the base current is supplied to the bipolar transistor Q2 so that the bipolar transistor Q2 becomes conductive and the reverse. Moreover, the bipolar transistor Q3 becomes non-conductive. As a result, the gate terminal and the source terminal of the field effect transistor Q1 are short-circuited, the gate voltage is cut off, and the field effect transistor Q1 becomes non-conductive. In this way, the reverse current flowing through the field effect transistor Q1 is blocked.

Therefore, according to the present embodiment, the field effect transistor Q1 inserted and connected to the negative power supply line is connected.
Based on the potential difference between the drain terminal and the source terminal of the bipolar transistor Q3, when the reverse current of the current is detected and the bipolar transistor Q3 is in the non-conducting state, the bipolar transistor Q2 cuts off the gate voltage. Since the transistor Q1 becomes non-conductive, it is possible to prevent backflow of current and prevent damage to the field effect transistor Q1.

In this embodiment, DC / D
Although the case where breakage or the like occurs inside the C converter 1 has been described, when the breakage or the like occurs inside the DC / DC converter 2, the backflow blocking means 12 performs the same operation as the above-described backflow blocking means 11. So DC / D
It is possible to prevent the reverse flow of current from the C converter 1.

Further, in this embodiment, two D
Although the C / DC converters are connected in parallel, a larger number of DC / DC converters may be connected in parallel.

[Second Embodiment] FIG. 2 is a diagram showing a configuration of a backflow prevention circuit according to a second embodiment. The backflow prevention circuit shown in FIG. 1 is the backflow prevention circuit 11, 1 shown in FIG.
2 shows another example of the configuration, which is characterized in that the anode terminal of the diode D3 is connected to the bipolar transistor Q.
3, the cathode terminal is connected to the drain terminal of the field effect transistor Q1, the emitter potential of the bipolar transistor Q3 is raised by the forward voltage of the diode D3, and conversely, the emitter potential of the bipolar transistor Q2 is lowered. Compared to the case without the diode D3, the bipolar transistor Q3 is made non-conductive and the bipolar transistor Q2 is made conductive with a small reverse current value so that the field effect transistor Q1 is made non-conductive. In addition, the same components as those of the backflow prevention circuit 11 are denoted by the same reference numerals.

Therefore, according to the present embodiment, when the potential of the cathode terminal of the diode D3 becomes higher than the potential of the emitter terminal of the bipolar transistor Q2, the forward voltage of the diode D3 corresponds to the forward voltage of the bipolar transistor Q3. Since the base potential becomes high (along with the emitter potential) and the bipolar transistor Q2 is made easy to conduct, the reverse current blocking circuit 1 shown in FIG.
Since the reverse current flowing through the field effect transistor Q1 is smaller than those of the field effect transistors 1 and 12, damage to the field effect transistor can be reliably prevented.

Incidentally, it is desirable to use a Schottky diode having a small voltage drop as the diode D3.

[Third Embodiment] FIG. 3 is a diagram showing a configuration of a backflow prevention circuit according to a third embodiment. The backflow prevention circuit shown in FIG. 1 is the backflow prevention circuit 11, 1 shown in FIG.
2 shows another configuration example of No. 2. The drain terminal of the field effect transistor Q7 is connected to the positive terminal and the source terminal thereof is connected to the common output terminal 7 through the positive power supply line, respectively. Further, the emitter terminal of the bipolar transistor Q8 is the positive power supply line connecting the source terminal of the field effect transistor Q7 and the common output terminal 7, the collector terminal is the gate terminal of the field effect transistor Q7, and the base terminal is the bipolar transistor Q9. It is connected to the base terminal of. The emitter terminal of the bipolar transistor Q9 is
The drain terminal and the collector terminal of the field effect transistor Q7 are connected to one terminal of the resistor R6. This terminal of the resistor R6 is connected to a connection line connecting the base terminal of the bipolar transistor Q8 and the base terminal of the bipolar transistor Q9, and the other terminal of the resistor R6 is connected to the negative power supply line. . One terminal of the resistor R5 is connected to the gate terminal of the field effect transistor Q7, and the other terminal is connected to the negative power supply line. The anode terminal of the diode D4 is connected to the drain terminal of the field effect transistor Q7, and the cathode terminal is connected to the source terminal of the field effect transistor Q7. Here, the bipolar transistors Q8 and Q9
For this, a pnp type transistor is used.

In such a reverse current blocking circuit, when the current flows in the normal direction, the potential of the drain terminal of the field effect transistor Q7 becomes higher than that of the source terminal thereof, and the potential of the bipolar transistor Q8 is increased. The voltage applied between the base and the emitter becomes smaller than the voltage applied between the base and the emitter of the bipolar transistor Q9 by the drain-source voltage of the field effect transistor Q7.

Therefore, the base current is supplied to the bipolar transistor Q9 through the resistor R6 connected to the negative power supply line, the bipolar transistor Q9 is rendered conductive and the bipolar transistor Q8 is rendered non-conductive. When the bipolar transistor Q8 is off, the gate voltage is supplied to the gate terminal of the field effect transistor Q7 through the resistor R5. As a result, the field effect transistor Q7 becomes conductive, and the current is transferred to the diode D4.
And the field-effect transistor Q7, and the power loss is reduced.

On the other hand, when a reverse current flows, the potential of the drain terminal of the field effect transistor Q7 becomes lower than that of the source terminal. At this time, the voltage applied between the base and the emitter of the bipolar transistor Q8 becomes larger than the voltage applied between the base and the emitter of the bipolar transistor Q9, and as a result, the base current is supplied to the bipolar transistor Q8 and the bipolar transistor Q8 is supplied. The transistor Q8 becomes conductive, and conversely, the bipolar transistor Q9 becomes non-conductive. As a result, the gate terminal and the source terminal of the field effect transistor Q7 are short-circuited, the gate voltage is cut off, and the field effect transistor Q7 becomes non-conductive. In this way, the reverse current flowing through the field effect transistor Q7 is blocked.

Therefore, according to the present embodiment, the field effect transistor Q7 inserted and connected to the positive power supply line is connected.
When a reverse current is detected based on the potential difference between the drain terminal and the source terminal of the bipolar transistor Q9, the bipolar transistor Q9 is turned on and the bipolar transistor Q8 is turned off, so that the field effect transistor Q8 is turned off.
By cutting off the gate voltage supplied to the field effect transistor 7, the field effect transistor Q7 becomes non-conductive, so that the backflow of the current is prevented and the field effect transistor Q7 is prevented.
It is possible to prevent breakage of 7.

[Fourth Embodiment] FIG. 4 is a diagram showing a configuration of a backflow prevention circuit according to a fourth embodiment. The backflow prevention circuit shown in FIG. 1 is the backflow prevention circuit 11, 1 shown in FIG.
2 shows another example of the configuration of the resistor R9 and the resistor R9 by inserting the resistor R9 into the negative power supply line connecting the drain terminal and the negative terminal of the field effect transistor Q1 shown in FIG.
Current direction detection circuit 13 for detecting the direction of the current flowing in 9
Is connected in parallel, a light emitting diode Dpc that switches between a light emitting state and a non-light emitting state depending on the direction of the current flowing through the resistor R9 is installed in the current direction detection circuit 13, and the resistor R1 is connected to the positive power supply line. The phototransistor Qpc is inserted and connected to the connection line.
In addition, in addition, the same components as those in FIG. 2 are denoted by the same reference numerals.

The characteristics of the backflow prevention circuit having such a configuration are as follows.
When the current is flowing in the normal direction, the light emitting diode Dpc is caused to emit light, and when the reverse current flows, the light emission is stopped and the phototransistor Qp
When c does not receive the light from the light emitting diode Dpc, the phototransistor Qpc is made non-conductive to cut off the gate voltage supplied to the gate terminal of the field effect transistor Q1. Especially.

Therefore, according to the present embodiment, the current direction detection circuit 13 detects the backflow of the current, and when the backflow of the current occurs, the light emitting diode D
Since the light emission of pc is stopped and the phototransistor Qpc is made non-conductive to cut off the gate voltage, the field effect transistor Q1 becomes non-conductive, so that the backflow of the current is prevented and the field effect transistor Q1.
It is possible to reliably prevent breakage of No. 1.

[0034]

As described above, according to the DC power supply device of the present invention, when the reverse current of the current is detected by the reverse current detecting means, the gate voltage cut-off means makes the positive side or the negative side. Since the gate voltage supplied to the field effect transistor connected to the source terminal and the drain terminal is cut off by inserting it into one of the power supply lines on the side, the field effect transistor becomes non-conducting. It is possible to prevent the backflow of the current flowing through the wire and prevent the field effect transistor from being damaged.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a DC power supply device according to a first embodiment.

FIG. 2 is a diagram showing a configuration of a backflow prevention circuit according to a second embodiment.

FIG. 3 is a diagram showing a configuration of a backflow prevention circuit according to a third embodiment.

FIG. 4 is a diagram showing a configuration of a backflow prevention circuit according to a fourth embodiment.

FIG. 5 is a diagram showing an example of a configuration of a conventional DC power supply device.

[Explanation of symbols]

1, 2 ... DC / DC converters 3, 4 ... Control circuits 5, 6 ... Diodes 7, 8 ... Common output terminal 9 ... Load 10 ... Battery 11, 12 ... Reverse current blocking circuit 13 ... Current direction detection circuits Q1, Q4, Q7 ... field effect transistors Q2, Q3, Q5, Q6 ... npn type bipolar transistors Q8, Q9 ... pnp type bipolar transistors R1, R2, R3, R4, R5, R6 ... resistors D1, D2, D3, D4 ... diode Qpc ... phototransistor Dpc ... Light emitting diode

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02M 3/28

Claims (5)

(57) [Claims] 1. A direct current power supply device for supplying direct current power supply in parallel by connecting positive power supply lines of a plurality of direct current power supply circuits respectively, and also connecting negative power supply lines thereof respectively. Source terminal and drain terminal are connected to either the negative side or the negative side power line,
A field effect transistor having a gate terminal connected to the other power supply line, and a backflow of a current flowing through the power supply line between two points of the power supply line.
A direct current power supply device comprising: a reverse current detection means for detecting the polarity of a potential difference; and a gate voltage interruption means for interrupting a gate voltage supplied to the gate terminal when a reverse current is detected. . 2. The backflow detection means is configured to detect the field effect transistor.
Polarity of the potential difference between the source and drain terminals of the transistor
, Two transistors whose base terminals are connected to each other
The DC power supply device according to claim 1, wherein the DC power supply device is detected through the respective emitter terminals of the power supply. 3. The backflow detection means has a resistance provided on at least one of the positive side and the negative side of the power supply line, and detects the backflow by the direction of the current flowing through the resistance. The DC power supply device according to claim 1 or 2. 4. The DC power supply device according to claim 1, wherein the gate voltage cutoff unit cuts off the gate voltage by short-circuiting the gate terminal and the source terminal. 5. The gate voltage cutoff means has switch means for opening and closing a connection line connecting the gate terminal and the power supply line, and cuts off the gate voltage by opening the connection line. The DC power supply device according to any one of claims 1 to 4.