JPH1075526A - Load monitor and load monitoring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a circuit without using a fuse and reduce the size and weight. SOLUTION: A load connecting detection circuit 6 which is provided in one of output lines judges whether a load is connected or not in accordance with a current value and outputs a level signal. An overcurrent detection circuit 5 which is provided between the secondary side of a switching regulator and the output terminal 3 of the output line opens and closes the contact of a relay RL1 in accordance with a level signal supplied from the load connecting detection circuit 6. Further, the value of an overcurrent detection resistor is changed to have two overcurrent detection points and, even if a part of the loads 1 and 2 is lost, the circuit is protected by an optimum applied current value. With this constitution, a fire caused by short-circuiting a load can be avoided without using a fuse, so that the improvement in view of security can be obtained. Further, as a fuse is not used for protecting the circuit from short- circuiting the load when a plurality of the loads 1 and 2 are connected in parallel with each other to the switching regulator, a space reduction can be realized and the size and weight reduction can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a load monitoring device and a load monitoring circuit, and more particularly to a load monitoring device and a load monitoring circuit for monitoring a load state when a plurality of loads are connected to a switching regulator.

[0002]

2. Description of the Related Art Conventionally, when a plurality of output lines are connected to a switching regulator, it is configured as shown in FIG.
The voltage excited in the secondary winding of the transformer Tl generates a DC voltage by a rectifying / smoothing circuit including diodes Dl and D2, a choke coil Ll, and a capacitor Cl.
0 and output to the load 102. When the output becomes excessive due to a short circuit, the rectifying / smoothing circuit 104 and the output terminal 10
3 is fed back to the control circuit 107 to control the on / off ratio of the switching transistor Ql so that the short-circuit current to the load does not exceed a certain value. It has become.

When there is no load 1 or load 2, for example, there is no load 1 having a current of 100 A, and
When there is only 1A load 2 and load 2 is short-circuited,
Unless a current of 100 A or more flows through the load 2, the overcurrent detection circuit does not operate. In the worst case, a short circuit occurs due to a high impedance having a thin output line to the load 2, so that a large current such as a current 90A continues to flow, which may cause a fire in a cable, a connector, or the like. Therefore, it was necessary to provide fuses F1 and F2 on the output line.

[0004]

In a conventional switching regulator, a fuse is provided on an output line to prevent an overcurrent due to a load short circuit, so that the number of maintenance parts increases and a physically large space is required. Required
There was a problem in terms of miniaturization or weight reduction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a load monitoring device and a load monitoring device which can be realized in a small space without using a fuse to protect a circuit when a load short circuit occurs when a plurality of loads are connected in parallel to a switching regulator. It is to provide a monitoring circuit.

[0006]

As a means for solving the problems, a load monitoring device of the present invention connects a load to a plurality of output lines on the output side of a switching regulator and monitors a current flowing through the load. A load monitoring device, which is provided on at least one output line of output lines, determines whether a load is connected to the output line based on the magnitude of a flowing current, and outputs a level signal. Means for detecting overcurrent between a secondary side of the switching regulator and a branch point of the output line, for opening and closing a contact of a relay based on a level signal from the load presence / absence detecting means and changing an overcurrent detection resistance value. Overcurrent detecting means having a point.

A load monitoring circuit according to the present invention is a load monitoring circuit for connecting a load to a plurality of output lines on the output side of a switching regulator and monitoring a current flowing through the load. A load presence / absence detection circuit that is provided on one of the output lines when the output line is connected, determines whether or not there is a load based on the magnitude of the flowing current, and outputs a level signal; It is located between the secondary side of the switching regulator and the branch point of the output line, and has two overcurrent detection points by opening and closing the contacts of the relay and changing the overcurrent detection resistance value according to the level signal from the load presence / absence detection circuit. An overcurrent detection circuit.

The load presence / absence detection circuit of the present invention comprises a current detection resistor for detecting a current, and a comparator for determining whether or not a load is connected according to the magnitude of the current. By connecting the detection resistor in parallel with the contact of the relay, the current detection resistor can be short-circuited.

Further, the overcurrent detection means of the present invention receives the output from the comparator of the load presence / absence detection means.

According to the load monitoring device and the load monitoring circuit of the present invention, when connecting a plurality of output lines to the output of the switching regulator, a load presence / absence detection circuit provided on at least one of the output lines A level signal is output by judging whether or not there is a load based on the magnitude of the current flowing through. An overcurrent detection circuit between the secondary side of the switching regulator and a branch point of the output line opens and closes a relay contact according to a level signal from the load presence / absence detection circuit. Thus, by changing the value of the overcurrent detection resistor and having two overcurrent detection points, the circuit can be protected with an optimal overcurrent value even when there is no part of the load.

Therefore, according to the present invention, the presence or absence of a load connected in parallel to the output of the switching regulator is automatically determined, and the current detection point is changed to an appropriate value, so that the fuse is not used. In addition, a fire due to a load short circuit can be prevented. Further, when a plurality of loads are connected in parallel to the switching regulator, no fuse is used for protecting the circuit when a load short circuit occurs, so that a small size and small space can be realized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A practical example of a load monitoring device and a load monitoring circuit according to the present invention will be described below with reference to FIG. In this embodiment, two output lines are connected in parallel to the output of the switching regulator, and a load 1 (large load capacity) and a load 2 (small load capacity) are connected to the respective output lines. Here, the load 1 and the load 2 are electronic circuits including an LSI, a resistor, a capacitor, and the like used in a computer or the like. The voltage excited in the secondary winding of the transformer Tl is converted into a DC voltage by a rectifying and smoothing circuit including diodes Dl and D2, a choke coil Ll, and a capacitor Cl, and is output to the load 1 and the load 2 through output lines.

Further, in this embodiment, a load presence / absence detection circuit comprising resistors (RS3, R5, R6, R7, R8) and a comparator A2 is provided between the output terminal 3 and the load 1. Further, between the rectifying / smoothing circuit 4 and the output terminal 3, there is provided an overcurrent detection circuit 5 composed of resistors (RS1, RS2, R1, R2, R3, R4), a relay RL1, and an operational amplifier Al. By connecting RS2 in parallel with the connection of the relay RL1, the current detection resistor RS2 can be short-circuited.

Due to the nature of the components constituting the electronic circuit, a current of at least A flows regardless of the operation of the load 1. In the load detection circuit, when a current flows to the load 1 through the current detection resistor RS3, a voltage drop occurs in the current detection resistor RS3. At this time, when the current flowing through the current detection resistor RS3 is equal to or less than the minimum current to the load 1, the voltage applied to the inverted human input terminal is higher than the voltage applied to the non-inverted input terminal of the comparator A.

In this embodiment, when the current flowing through the resistor RS3 is equal to or more than the minimum current to the load 1, the comparator A
2 so that the voltage applied to the non-inverting input terminal becomes lower than the voltage applied to the inverting input terminal.
The values of R7 and R8 are set in advance. The load presence / absence detection circuit 6 determines whether the load 1 exists or not by determining whether the load 1 is present or not.
Based on the current flowing in S3, it is determined whether the current is equal to or greater than the minimum current of the load 1, and the comparator A2 outputs a level signal (VA2) based on the determination.

In the circuit configuration shown in FIG.
Is connected, the comparator A2 outputs a high (H) level. When the load 1 is not connected, a low (L) level of the transistor level is output. Relay RLl in overcurrent detection circuit 5 receives output VA2 from comparator A2.

For example, when the output VA2 of the comparator A2 is at a high level, the contact of the relay RL1 is made, and when the output VA2 of the comparator A2 is at a low level, the contact of the relay RL1 breaks. That is, the current detection resistance in the overcurrent detection circuit 5 becomes the resistance RS1 when there is the load 1, and becomes the resistance RS + RS2 when there is no load 1.

In the overcurrent detection circuit 5, the operational amplifier Al outputs a control signal when the current flowing through the current detection resistor becomes equal to or more than a predetermined value. The control circuit that has received this control signal narrows the pulse signal to the switching transistor Ql and limits the output as a switching regulator. Accordingly, when the load 1 is present in the current detection resistor in the overcurrent detection circuit 5, the overcurrent value corresponding to the sum of the current value of the load 1 and the current value of the load 2 is limited by the current detection resistor RSl. . When there is no load 1, a smaller output current (an overcurrent value corresponding to the current value of the load 2) can be limited by the current detection resistor (RS1 + RS2).

According to the embodiment described above, when a plurality of output lines are connected to the output of the switching regulator, the magnitude of the current flowing through the load presence / absence detection circuit provided on one of the output lines is determined. Thus, it is determined whether or not there is a load, and a level signal is output. The overcurrent detection circuit 5 between the secondary side of the switching regulator and the branch point of the output line opens and closes the contacts of the relay according to the level signal from the load presence / absence detection circuit 6. Thus, by changing the value of the overcurrent detection resistor and having two overcurrent detection points, the circuit can be protected with an optimal overcurrent value even when there is no part of the load.

Therefore, according to the present embodiment, it is possible to automatically determine the presence or absence of a load connected in parallel to the output of the switching regulator, and to change the current detection point to an appropriate value, thereby using a fuse. Therefore, a fire due to a load short circuit can be prevented, which is preferable in terms of security. Also, when connecting multiple loads to the switching regulator in parallel, it can be realized in a small space without using a fuse to protect the circuit when a load short circuit occurs.
The size and weight can be reduced.

[0021]

As described above, according to the load monitoring device and the load monitoring circuit of the present invention, the presence or absence of a load connected in parallel to the output of the switching regulator is automatically determined, and the current detection point is set to an appropriate value. By changing to a value,
Since a fire due to a load short circuit can be prevented without using a fuse, security can be improved.

Further, according to the present invention, when a plurality of loads are connected in parallel to the switching regulator, a small space is realized without using a fuse for protecting a circuit when a load short circuit occurs. In addition, it is possible to achieve effects such as reduction in weight and reduction in product cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a specific configuration of a load monitoring device and a load monitoring circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a specific configuration of a conventional load monitoring device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 load 2 load 3 output terminal 4 rectifying and smoothing circuit 5 overcurrent detection circuit 6 load presence / absence detection circuit 7 control circuit Dl, D2 diode Ll choke coil Cl capacitor RSl, RS2, RS3 current detection resistor Al operational amplifier A2 comparator Rl, R2, R3 , R4, R5, R6, R7, R8 Resistance RLl Relay Fl, F2 Fuse Tl Transformer Ql Switching transistor

Claims (4)

[Claims] 1. A load monitoring device for connecting a load to a plurality of output lines on the output side of a switching regulator and monitoring a current flowing through the load, wherein the load monitoring device is provided on at least one output line of the output lines.
A load presence / absence detecting means for judging whether or not a load is connected to the output line based on the magnitude of the flowing current, and outputting a level signal; and a connection between a secondary side of the switching regulator and a branch point of the output line. And an overcurrent detection means having two overcurrent detection points for opening and closing a contact of a relay based on the level signal from the load presence / absence detection means and changing an overcurrent detection resistance value. And load monitoring device. 2. A load monitoring circuit for connecting a load to a plurality of output lines on the output side of a switching regulator and monitoring a current flowing through the load, wherein a plurality of output lines are connected to an output of the switching regulator. A load presence / absence detection circuit that is provided on one of the output lines and that determines whether or not there is a load based on the magnitude of the flowing current and outputs a level signal; and a secondary side of the switching regulator. An overcurrent detection circuit having two overcurrent detection points, which is located between the output line branch point and the level signal from the load presence / absence detection circuit and opens and closes a relay contact and changes an overcurrent detection resistance value. A load monitoring circuit, comprising: 3. The load presence / absence detection circuit comprises: a current detection resistor for detecting the current; and a comparator for determining whether or not a load is connected according to the magnitude of the current. 3. The load monitoring circuit according to claim 2, wherein the current detection resistor is connected in parallel with a contact portion of the relay. 4. The load monitoring circuit according to claim 2, wherein said overcurrent detection means receives an output from said comparator of said load presence / absence detection means.