JP2831822B2 - Overcurrent detection system - Google Patents

Description

The present invention relates to an overcurrent detection system of a DC power supply used for supplying DC power to a printed circuit board.

(Prior Art) Conventionally, a DC power supply device has been configured as shown in FIG. In FIG. 4, an AC-DC converter 41 of a DC power supply 40 rectifies and smoothes an AC (AC) power supply and converts it into a DC (DC) power supply. The regulator 42 stabilizes the DC output voltage from the AC-DC converter 41 and generates a specified DC voltage. The DC voltage output from the regulator unit 42 is applied via a connector 51 to a load such as an electronic computer, for example, a printed circuit board 50 (upper circuit). The DC power supply 40 is provided with an overcurrent detection circuit 43 located between the regulator unit 52 and the load (printed circuit board 50). In the overcurrent detection circuit 43, a current limit value (overcurrent limit value) corresponding to the power supply rated capacity of the DC power supply device 40 determined at the beginning of the design is set. Thus, the overcurrent detection circuit 43
When it is detected that a current exceeding the current limit value has flowed into the printed circuit board 50, the regulator 42 is controlled to protect the power supply by shutting down the power (cutting off the power supply) or using the characteristic of "F".

In recent years, many power supply devices have a large current capacity (rated current), and there are many cases where the power supply device is used as a common power supply. Therefore, the use of 100% of the power supply capacity has been reduced. For example, in a system using a 5V, 200A power supply with a 50A load, there is a margin of 150A. In such a system, even if a short circuit accident occurs in the load, the load that can pass as much as 150 A current is small, so the overcurrent detection does not occur and the power supply is not shut off, so the current continues to flow,
There was a risk that the short-circuited part would generate heat and ignite.

(Problems to be Solved by the Invention) As described above, in the conventional power supply device, the overcurrent limit value serving as the reference for overcurrent detection is fixedly set according to the power supply rated capacity of the device. If you are using a power supply with a sufficient capacity for the current load, even if an excessive current flows for the current load,
Since the current does not exceed the overcurrent limit value, overcurrent detection is not performed and there is a problem that the load cannot be protected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to dynamically set an overcurrent limit value suitable for a load condition on a printed circuit board to be used, and thus to efficiently use the overcurrent limit value suitable for a use load condition. An object of the present invention is to provide an overcurrent detection system capable of detecting an overcurrent.

In addition, the present invention is not limited to the overcurrent limit value determined by the load state of the printed circuit board, but to the fixed overcurrent determined by the rated capacity of the DC power supply device during hot-line replacement of the printed circuit board where transient overcurrent flows. An object of the present invention is to provide an overcurrent detection system that can reliably detect only an abnormal overcurrent caused by a short circuit or the like without being affected by a transient overcurrent by performing an overcurrent using a limit value.

[Configuration of the Invention] (Means for Solving the Problems) The present invention relates to an overcurrent detection system for detecting an overcurrent flowing on a printed circuit board to which DC power is supplied from a DC power supply device. A current detecting means for detecting an output current from the device, and in a normal state, a value of the output current detected by the current detecting means is measured for a certain number of times at a certain time interval, and an average of the output current values measured for the certain number of times. Setting means for obtaining a value and setting a first current limit value (I _L ) corresponding to the average value at every constant cycle;
After the current limit value is set, the value of the output current detected by the current detection means is measured at regular time intervals until the next cycle is started. A first current limit value for detecting that an overcurrent is flowing through the printed circuit board by comparing with the latest first current limit value set by
And overcurrent detecting means.

The present invention further comprises a live-line replacement detecting means for detecting that a live-line replacement of a printed circuit board to which DC power is supplied from the DC power supply device has been performed, and notifying the power supply unit, In response to a live-line replacement detection notification from the replacement detection unit, the power-supply unit is activated to perform overcurrent detection based on a predetermined second current limit value (I _L2 ) corresponding to the rated capacity of the power supply device. An overcurrent detection means, wherein the value of the output current detected by the current detection means is a predetermined third current limit value (I _L1 ) (provided that the third current limit value I _L1 <the second A predetermined time after exceeding the current limit value I _L2 ), the value of the output current detected by the current detecting means is measured and compared with the second current limit value, so that when the printed circuit board is replaced with a hot wire, Overcurrent on the above printed circuit board Currents will also be characterized in that a second overcurrent detection means for detecting that are.

The present invention further provides the first overcurrent detection means with a next determination function, that is, a plurality of times that the output current value detected by the current detection means exceeds the first current limit value for a plurality of times. Also, a feature is provided that a determination function for determining that an overcurrent is flowing when detection is performed.

(Operation) According to the above configuration, the current detecting means always detects the output current (load current) flowing from the DC power supply to the printed circuit board (upper load). The setting means performs the following current limit value setting processing in a normal state (other than at the time of exchanging a live board of a printed board). That is, the setting means measures the value of the output current detected by the current detecting means at a certain time interval for a certain number of times, obtains an average value of the output current values measured at the certain number of times, and obtains a first value corresponding to the average value. It repeats the operation for setting the current limit value I _L at every predetermined cycle. in this way,
Current limit value I _L that is set by the setting means is actually used load (use load) to flow the output current latest average value of (load current), i.e. a constant average current value based on cycle Since it is dynamically determined for each time, that is, it is determined by learning the value of the current flowing through the load, the value is suitable for the load state. Therefore, by performing the overcurrent detection Thus the current limit value I _L which is determined as a reference by the first overcurrent detecting means, using a current limit value of the fixed corresponding to power rated capacity as in the prior art Efficient overcurrent detection suitable for the used load can be performed as compared with the system.

In an electronic computer or the like, there are generally a plurality of printed circuit boards that receive power supply from a DC power supply device. In the case of a 24 hour operation such as an industrial computer, the printed circuit board is also doubled, and has a so-called fault tolerant function that can continue the system operation even if one printed circuit board fails. In a system of this type, when a printed circuit board is inserted and removed to replace a failed printed circuit board, it is general that the power supply is not turned off. When the printed circuit board is removed and inserted while the power is turned on, that is, when the live wiring of the printed circuit board is performed (especially when the printed circuit board is inserted), the noise removal bypass provided on the printed circuit board is provided. A transient overcurrent (rush current) flows because the capacitor is temporarily in a state close to a short circuit. Therefore, even if during a hot replacement of the printed circuit board, than was overcurrent detection based on the current limit value I _L that is set so as to learn the value of the current flowing through the load as described above, transient Overcurrent is also detected as abnormal. Therefore, in the present invention, a hot-line replacement detecting means is provided, and when it is detected that the live-line replacement of the printed circuit board has been performed, the power supply rated capacity is replaced by the first overcurrent detecting means instead of the overcurrent detection. and to perform the overcurrent detection by the second overcurrent means relative to the current limit value I _L2 fixed corresponding to. This overcurrent detection is performed by the current detection means a predetermined time after the value of the output current detected by the current detection means exceeds a predetermined third current limit value I _L1 (I _L1 <I _L2 ). This is performed by measuring the value of the detected output current and comparing it with the current limit value _IL2 . As a result, it is possible to prevent an erroneous determination of an abnormality due to a transient overcurrent flowing at the time of hot-line replacement, and it is possible to reliably detect an abnormal overcurrent due to a short circuit or the like.

(Embodiment) FIG. 1 is a block diagram showing an embodiment around a DC power supply of a computer system to which the present invention is applied. The same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description is omitted. In FIG. 1, reference numeral 10 denotes a DC power supply device. The DC power supply 10 has an AC-DC converter 41 and a regulator 42 in the same manner as the conventional DC power supply (40) shown in FIG. 4, and also flows to a load (here, a printed circuit board 20 described later). A current detection circuit 11 for detecting a current (output current, load current) and converting it into a voltage is provided in place of the overcurrent detection circuit 43 shown in FIG. The DC power supply 10 further includes
A / D (analog / analog) for converting (the voltage conversion value of) the analog output current value detected by the current detection circuit 11 to a digital value
Digital) conversion circuit (ADC) 12, A / D converter circuit current limit value is a reference value based on an output value for performing an overcurrent detection adapted to a load of 12 (over-current limit value) automatically I _L to set, the current limit value I _L and the a / D converter output value and performs to overcurrent detection compares the power-off signal of the circuit 12 13
Outputting a control unit, a microcomputer 14 and the current limit value register 15 for storing the I _L,
have.

Reference numeral 20 denotes a printed board on which various circuits forming a part of the computer system are mounted, and reference numeral 21 denotes a connector on which the printed board 20 is mounted. The DC power of the DC power supply 10 is supplied to the printed circuit board 20 via the connector 21.
Reference numeral 22 denotes a microswitch for detecting that the printed circuit board 20 is mounted (inserted) on the connector 21, and reference numeral 23 denotes a microswitch when the printed circuit board 20 is mounted on the connector 21.
A contact provided on the printed circuit board 20 for pressing the actuator of 22 to switch on, 24 is a micro switch
This is a signal line for notifying the microcomputer 14 in the DC power supply 10 of the state of 22 as an interrupt signal.

Although not shown in FIG. 1, the printed circuit board 20
Are provided, and a connector is provided for each printed circuit board 20.
21 and a microswitch 22 are provided. The state of the microswitch 22 provided for each printed circuit board 20 is wired or
14 is to be notified.

FIG. 2 is a flowchart showing an overcurrent detection routine in the normal state by the microcomputer 14 in FIG. 1, and FIG. 3 is a flowchart showing an overcurrent detection routine when the live board of the printed circuit board 20 is replaced (inserted). .

Next, the operation of the configuration of FIG. 1 will be described with reference to the flowcharts of FIGS.

Now, the printed circuit board 20 is mounted (inserted) on the connector 21. In this state, when the AC power is input to the DC power supply 10 shown in FIG.
The current flows into the printed circuit board 20 through the current detection circuit 11 and the connector 21. This load current is detected by the current detection circuit 11, and the current value is converted into a voltage value. The load current detection value (voltage conversion value in this case) of the current detection circuit 11 is supplied to an A / D conversion circuit (ADC) 12. The A / D conversion circuit 12 converts the load current detection value from the current detection circuit 11 into a digital value I. The load current detection value (load current value) I converted into a digital value by the A / D conversion circuit 12
Is supplied to the microcomputer 14.

The microcomputer 14 starts operating when the power is turned on, first reads the load current detection value I from the A / D conversion circuit 12 n times at a constant time interval, and averages the average value to a steady load current value (steady output current value) Ii. (Step in FIG. 2)
S1). Next, the microcomputer 14 calculates the steady load current value.
Ii alpha% than the original, for example Ii (the alpha as for example about 20 is applied) only the value is large current limit value to determine the (overcurrent limit value) I _L, is set in the register 15 (FIG. 2 Step S2). In this way, the current limit value I _L that is set in the register 15, because it was determined based on the steady-state load current value Ii, printed circuit board 20 which is currently used
It becomes a value suitable for the load condition.

The microcomputer 14 has finished setting the current limit value I _L, it starts a timer (not shown) for setting the cycle of the current limit value setting (Fig. 2 step S3). Next, the microcomputer 14 reads the load current detection value I from the A / D conversion circuit 12 (step in FIG. 2).
S4), and checks whether this read load current detection value I exceeds the current limit value I _L that is set in the register 15 (FIG. 2 step S5). If if I ≦ I _L, the microcomputer 14 is the printed circuit board 20 determines that no overcurrent flows. In this case, the microcomputer 14 checks whether or not the time is over (step S6 in FIG. 2). If the time is not over, the microcomputer 14 executes the above steps S4 and S5 again after a fixed time. If contrast I> I _L, the microcomputer 14 determines that an overcurrent flows through the printed circuit board 20. In this case, the microcomputer 14 reads the load current detection value I again from the A / D conversion circuit 12 after a certain period of time in order to check whether or not the overcurrent is transient due to a sudden change in load or the like. 2 FIG step S7), and the read load current detection value I it is checked whether or not it exceeds the current limit value I _L (FIG. 2 step S8).

If it is determined that I> I _L in step S8, overcurrent microcomputer 14 is flowing to the printed circuit board 20 judges that not transient, in order to protect the load on the printed circuit board 20 Apply the power cutoff signal 13 to the regulator
42 to shut off the power (step S in FIG. 2).
9). Instead of the power shut-off, it is also possible to protect the load on the printed circuit board 20 by the "-" character.
If this respect an I ≦ I _L, the microcomputer 14
Determines that the overcurrent detected in the previous step S5 is transient and not abnormal, and in step S5, I ≦ I _L
Is performed, the time-over check in step S6 is performed. When time-out is detected in step S6, the microcomputer 14 returns to steps S1 and S2, and executes the current limit value setting process again. Thus, by repeating the current limit value setting processing for each predetermined cycle, even if setting the current limit value I _L that conform to the latest state of the load even if slight variations in the state of the load on the printed circuit board 20 can do.

Next, detection of overcurrent when the printed circuit board 20 shown in FIG. 1 is replaced by a hot wire due to a failure or the like will be described.

Now, with the DC power supply 10 turned on,
It is assumed that the printed circuit board 20 has been inserted into the connector 21.
At this time, the operator of the micro switch 22 is pressed by the contact 23 of the printed circuit board 20, and the micro switch 22 is turned on. The ON signal of the micro switch 22 is input to (the interrupt input terminal of) the microcomputer 14 via the signal line 24 as an interrupt signal for notifying that the live board of the printed circuit board 20 has been replaced.

When an interrupt signal is input via the signal line 24, that is, when the microcomputer 14 detects that the printed circuit board 20 has been inserted into the connector 21, the microcomputer 14 replaces the overcurrent detection routine shown in FIG. The overcurrent detection routine shown in the figure is executed as follows. First, the microcomputer 14
A load current detection value (load current value) I is read from the A / D conversion circuit 12 (step S11 in FIG. 3), and the read load current detection value I exceeds a predetermined current limit value _IL1 . Operation to check whether or not (step S1 in FIG. 3)
2) is repeated until I> I _L1 is determined. The current limit value _IL1 is a value necessary and sufficient for detecting that a transient overcurrent (rush current) flows when the printed circuit board 20 is replaced with a hot wire.

The microcomputer 14 determines in step S12 that I> I
_{When L1} is determined and it is determined that a transient overcurrent has started to flow due to the replacement of the live board of the printed circuit board 20, it is determined whether or not this overcurrent is truly transient (according to an accident such as a short circuit). In order to check for an abnormal overcurrent, the load current detection value I is read again from the A / D conversion circuit 12 after a predetermined time (step S13 in FIG. 3). Next, microcomputer 14
Is whether or not the load current detection value I read in step S13 exceeds a current limit value I _L2 (here, I _L2 > I _L1 ) corresponding to the power supply rated capacity of the DC power supply 10. Is checked (step S14 in FIG. 3).

If the determination in step S14 is I ≦ I _L2 , the microcomputer 14 determines that only a transient overcurrent has flowed through the printed circuit board 20 to replace the hot wire, and therefore it is not abnormal. Then, the process returns to the normal overcurrent detection routine shown in FIG. On the other hand, if I> I _L2 , the microcomputer 14 determines that an abnormal transient current that is not transient is flowing through the printed circuit board 20 due to a short circuit accident of the printed circuit board 20 or the like, and the power cutoff signal 13 To the regulator unit 42 to shut off the power (step in FIG. 3).
S15).

Note in the above embodiment, in the normal state, if the load current detection value I exceeds the current limit value I _L twice successively is detected, the power supply as an overcurrent is not transient flows Although the case of shutting off has been described, it is also possible to shut off the power supply when it is detected that the power is exceeded three times or more consecutively. The same applies in the overcurrent detection of the printed circuit board at the time of hot-replaced, shut off the power when the load current detection value I exceeds the current limit value I _L2 continues a plurality of times is detected Is also good. Further, in the above-described embodiment, the case where the insertion of the printed circuit board 20 into the connector 21 (hot swap of the printed circuit board 20) is detected by the microswitch 22 has been described. However, the present invention is not limited to this. It is also possible.

[Effects of the Invention] As described above in detail, according to the present invention, in the normal state, the first current limit adapted to the used load based on the current flowing to the load actually used on the printed circuit board The value (I _L ) is automatically set every fixed cycle, and overcurrent detection is performed based on this set limit value. If an overcurrent flows through the load due to an abnormality in the load used, etc. Even if it is within the range of the fixed current limit value corresponding to the power supply rated capacity, overcurrent detection can be performed differently from the past, that is, efficient overcurrent detection suitable for the used load can be performed, and the size of the used load can be reduced. Regardless, the use load can be appropriately protected. Therefore, according to the present invention, it is not necessary to select a power supply device having a power supply rated capacity suitable for the size of the use load as in the related art in order to properly protect the use load, as long as the maximum capacity of the power supply is not exceeded. The same power supply can be used regardless of the magnitude of the load used. For the same reason, when one system requires a plurality of power supply devices, the same type of power supply device can be used.

Further, according to the present invention, at the time of hot wire replacement of the printed circuit board, instead of the overcurrent detection based on the first current limit value, the second current which is a fixed current limit value corresponding to the power supply rated capacity is used. Since the overcurrent detection based on the limit value (I _L2 ) is adopted, it is possible to prevent erroneous overcurrent detection due to the occurrence of transient overcurrent due to hot-line replacement. An abnormal overcurrent caused by an accident such as a short circuit can be reliably detected to prevent a flame or the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart of an overcurrent detection routine in a normal state, FIG. 3 is a flowchart of an overcurrent detection routine at the time of hot wire replacement of a printed circuit board, FIG. 4 is a block diagram showing a conventional example. 10 DC power supply unit 11 Current detection circuit 12 A / D
Conversion circuit (ADC), 13 Power cutoff signal, 14 Microcomputer, 15 Register, 20 Printed circuit board, 21 Connector, 22 Microswitch (hot wire replacement detection means), 41 ... AC-DC converter, 42 ... Regulator.

Claims (3)

(57) [Claims] An overcurrent detection system for detecting an overcurrent flowing in a printed circuit board to which DC power is supplied from a DC power supply, wherein current detection means for detecting an output current from the DC power supply; In the normal state, the value of the output current detected by the current detecting means is measured a fixed number of times at fixed time intervals, an average value of the output current values measured a certain number of times is obtained, and a first value corresponding to the average value is obtained. Setting means for repeating an operation of setting a current limit value at every fixed cycle; and after the setting of the first current limit value by the setting means, until the next cycle is started, the current detecting means. The value of the detected output current is measured at regular time intervals, and each time, the latest first current limit value set by the setting means at that time is measured. By comparing the values, overcurrent detection system characterized by comprising a first overcurrent detection means for detecting that overcurrent flows to the printed circuit board. 2. A direct-current power supply device, and a live-line replacement detecting means for detecting that a live-line exchange of a printed circuit board to which direct-current power is supplied from the direct-current power supply has been performed and notifying the power supply unit. In the overcurrent detection system for detecting an overcurrent flowing in the printed circuit board, the DC power supply includes a current detection unit that detects an output current from the power supply, An operation of measuring the output current value detected by the means at a fixed time interval for a fixed number of times, obtaining an average value of the output current values measured at the fixed number of times, and setting a first current limit value corresponding to the average value Setting means for repeating the above at every constant cycle, and after the first current limit value is set by the setting means, until the next cycle starts, the current detecting means The value of the detected output current is measured at fixed time intervals, and each time the output current is compared with the latest first current limit value set by the setting means at that time, an overcurrent is supplied to the printed circuit board. A first overcurrent detecting means for detecting that the current is flowing, and a predetermined overcurrent corresponding to a rated capacity of the DC power supply device, being activated upon receiving a hot-line replacement detection notification from the hot-line replacement detecting means. A second overcurrent detection means for performing overcurrent detection based on the second current limit value, wherein the value of the output current detected by the current detection means is a predetermined third current limit value (However, the output current value detected by the current detection means is measured a predetermined time after exceeding the third current limit value <the second current limit value) and is compared with the second current limit value. This A second overcurrent detecting means for detecting that an overcurrent is flowing in the printed circuit board when the printed circuit board is replaced with a hot wire. 3. The method according to claim 2, wherein the first overcurrent detecting means detects a case where the value of the output current detected by the current detecting means exceeds the first current limit value continuously plural times. 3. The overcurrent detection system according to claim 1, wherein it is determined that an overcurrent is flowing.