JPH0496617A - Overcurrent detection system - Google Patents

Abstract

PURPOSE:To detect an overcurrent in an efficiency adapted for a state of a using load by automatically setting a current limit value adapted for the load at each predetermined time, and detecting the overcurrent with the set limit value as a reference. CONSTITUTION:A load current is detected by a current detector 11, and converted to a digital value I by an A/D converter 12. A microcomputer 14 reads a detected load current value from the converter 12 n times at each predetermined time interval, and decides a current limit value. Then, the microcomputer 14 reads a detected load current value, and checks whether the detected value exceeds the limit value or not. If the microcomputer 14 judges the flow of the overcurrent, it again reads the detected value after a predetermined time, and checks whether the read detected value exceeds the limit value or not.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) This invention relates to an overcurrent detection method for a DC power supply device 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, the AC-DC of the DC power supply device 40
The conversion unit 41 rectifies and smoothes AC (alternating current) power to convert it to DC.
(DC) power supply. The regulator section 42 is an AC
- Stabilize the DC output voltage from the DC converter 41 to generate a specified DC voltage. The DC voltage output from the regulator section 42 is applied to a load such as an electronic computer, for example, a printed circuit board 50 (upper circuit) via a connector 51.

The DC power supply device 40 includes an overcurrent detection circuit 43 located between the regulator section 52 and the load (printed circuit board 50).
Or is provided. 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 design is set in the overcurrent detection circuit 43. When the overcurrent detection circuit 43 detects that a current exceeding the current limit value has flowed into the printed circuit board 50, it controls the regulator section 42 to shut down the output (cut off the power supply) or shut down the "back" characteristic. etc. to protect the power supply.

Now, in recent years, many power supply devices have a large current capacity N (rated current), and are often used as a common power supply, so the use of a power supply capacity of 1009° is becoming less common. For example, 5V, 20OA power supply
In a system used with a load of A, there is a margin of 150A. In such a system, even if a short-circuit accident occurs in the load, there are few loads that can pass a current of 150A.
Therefore, the power supply that led to the overcurrent detection was not cut off, so the current continued to flow, and there was a risk that the short-circuited part would heat up and cause a fire.

(Problem to be solved by the invention) As mentioned above, in conventional power supply devices, the overcurrent limit value, which is the standard for overcurrent detection, is fixedly set according to the rated power capacity of the device. If you are using a power supply with sufficient capacity for the current load, even if the current is too high for the current load, the overcurrent limit value will not be exceeded. There was a problem that overcurrent detection was not performed and the load could not be protected.

This invention was made in view of the above circumstances, and its purpose is to dynamically set an overcurrent limit value that is suitable for the load condition on the printed circuit board used, thereby achieving an efficient and efficient An object of the present invention is to provide an overcurrent detection method capable of detecting overcurrent.

In addition, when hot-replacing a printed circuit board in which a transient overcurrent flows, the present invention provides a fixed overcurrent limit value determined by the rated capacity of the DC power supply, rather than an overcurrent limit value determined by the load condition of the printed circuit board. An object of the present invention is to provide an overcurrent detection method that is not affected by transient overcurrents and can reliably detect only abnormal overcurrents caused by short circuits or the like by detecting overcurrents using limit values.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an activation system that detects that a hot-wire replacement has been performed on a printed circuit board to which DC power is supplied from a DC power supply and notifies the power supply. In addition to comprising a line exchange detection means, the DC power supply includes a current detection means for detecting an output current from the power supply, and a current value corresponding to an average current value of the output current detected by the current detection means in a normal state. a setting means for setting a first current limit value (IL) at approximately regular intervals; and a setting means for setting the latest first current limit value (IL) set by the setting means and the detection result of the current detection means in a normal state. The first overcurrent detection means for detecting that an overcurrent is flowing through the printed circuit board, and the predetermined overcurrent detection means corresponding to the rated capacity of the DC power supply when replacing the printed circuit board while hot. Comparing the second current limit value (IL2) and the detection result of the current detection means,
The present invention is characterized in that a second overcurrent detection means is provided for detecting that an overcurrent is flowing through the printed circuit board.

(Function) According to the above configuration, the current detection means always detects the output current (load current) flowing from the DC power supply device to the printed circuit board (load on the board). The setting means performs the following current limit value setting process in a normal state (other than during hot-wire replacement of a printed circuit board). That is, the setting means receives the output current detected by the current detection means, calculates the average current value at regular intervals, and each time sets the current limit value based on the calculation result (average current value). 11. Set.

In this way, the current limit value IL set by the setting means is dynamically determined at regular intervals based on the average current value flowing through the load actually used (load in use). In other words, since it is determined by learning the value of the current flowing through the load, the value is appropriate for the load condition. Therefore, by performing overcurrent detection by the first overcurrent detection means using the current limit value IL determined in this way as a reference, the method uses a fixed current limit value corresponding to the rated capacity of the power supply as in the conventional method. Compared to conventional methods, overcurrent detection can be performed more efficiently depending on the load being used.

Now, in electronic computers and the like, there are generally a plurality of printed circuit boards that receive power from a DC power supply device. In devices such as industrial computers that require 24-hour operation, the printed circuit boards are also duplicated, and have a so-called fault-tolerant function that allows the system to continue operating even if one printed circuit board fails. In this type of system, when a printed circuit board is inserted or removed to replace a faulty printed circuit board, the power is generally not turned off.

When a printed circuit board is inserted or removed while the power is on, that is, when a printed circuit board is hot replaced (especially when inserting a printed circuit board), the noise reduction plug installed on the printed circuit board must be removed. A temporary overcurrent (rush current) flows because the bypass capacitor is temporarily short-circuited. For this reason, even when replacing a printed circuit board with a hot wire, if overcurrent detection is performed based on the current limit value l, which is set by learning the value of the current flowing through the load as described above, it may be a temporary problem. An overcurrent is also detected as an abnormality. Therefore, in the present invention, a live wire replacement detection means is provided, and when it is detected that a printed circuit board has been replaced with a hot wire, instead of the overcurrent detection by the first overcurrent detection means, the rated capacity of the power supply is Overcurrent detection is performed by the second overcurrent means using a fixed current limit value IL2 corresponding to the current limit value IL2 as a reference. This prevents erroneous determination of abnormality due to transient overcurrent flowing during hot wire replacement, and also makes it possible to reliably detect abnormal overcurrent caused by short circuits and the like.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a two-position DC power source of a computer system to which the present invention is applied. Note that the same parts as in FIG. 4 are given the same reference numerals and detailed explanations are omitted. In FIG. 1, 10 is a DC power supply device. The DC power supply device 10 has an AC-DC conversion section 41 and a regulator section 42 like the conventional DC power supply device (40) shown in FIG. A current detection circuit 11 that detects current (output current, load current) and converts it into voltage is provided in place of the overcurrent detection circuit 43 shown in FIG. The DC power supply 10 further includes an A/D (analog/digital) conversion circuit (A/D) that converts the analog output current value (voltage conversion value) detected by the current detection circuit 11 into a digital value.
C) 12. Automatically set a current limit value (overcurrent limit value) of 1 m, which is a reference value for overcurrent detection suitable for the load, based on the output value of the A/D conversion circuit 12. A control unit, for example, a microcomputer j4, which compares the current limit value 1 with the output value of the A/D conversion circuit 12 to detect an overcurrent and outputs a power cutoff signal 13, and stores the current limit value IL. register 15 for
have.

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

It should be noted that the printed circuit board 20 may be omitted in FIG.
A plurality of circuit boards 20 are provided, and each printed circuit board 20 is provided with a connector 21 and a microswitch 22.

The state of the microswitch 22 provided for each printed circuit board 20 is wired ORed and notified to the microcomputer 14.

FIG. 2 is a flowchart showing an overcurrent detection routine performed by the microcomputer 14 in FIG. .

Next, the operation of the configuration shown in FIG. 1 will be explained as shown in FIGS. 2 and 3! This will be explained with reference to a flowchart.

It is now mounted (inserted) on the printed circuit board 20 or the connector 21, and in this state, the AC
When the power is input and turned on, a load current flows into the printed circuit board 20 through the current detection circuit 11 in the DC power supply 10 and further through the connector 21.

This load current is detected by a current detection circuit 11, and the current value is converted into a voltage value. This current detection circuit 11
The detected load current value (voltage conversion value here) 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) (2) 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, and first reads the load current detection value I from the A/D conversion circuit 12 n times at fixed time intervals, and calculates the average value as the steady load current value (steady output current value) If. (Step S2 in FIG. 2). Next, the microcomputer 14 determines a current limit value (overcurrent limit value) IL that is larger than 11 by α% (for example, about 20 is applied as α) based on the steady load current value 11. , register 15
(Step S2 in FIG. 2). The current limit value ■ is thus set in the register 15.

Since it is determined based on the steady load current value It, it is a value that is suitable for the load condition of the printed circuit board 20 currently in use.

When the microcomputer 14 finishes setting the current limit value, it starts a timer (not shown) for determining the cycle for setting the current limit value (second timer).
Figure step S3). Next, the microcomputer 14
Read the load current detection value ■ from the /D conversion circuit 12 (second
(Step S4 in FIG. 2) It is checked whether the read load current detection value I exceeds the current limit value I set in the register 15 (Step S5 in FIG. 2). If I≦IL, the microcomputer 14 determines that no overcurrent is flowing through the printed circuit board 20. In this case, the microcomputer 14 checks whether the time has expired or not in step S6 in FIG.
), and if there is no time-over, the above-mentioned step S4. Execute S5. On the other hand, if 1>■, the microcomputer 14 determines that an overcurrent has flowed through the printed circuit board 20. In this case, the microcomputer 14 checks whether the overcurrent is temporary due to a sudden change in load, etc., after a certain period of time.
The load current detection value I is read again from the D conversion circuit 12 (step S7 in FIG. 2), and it is checked whether the read load current detection value I exceeds the current limit value I (step S7 in FIG. 2). S8).

If the determination in step S8 is I>IL, the microcomputer 14 determines that the overcurrent flowing through the printed circuit board 20 is not temporary, and takes steps to protect the load on the printed circuit board 20. The power cutoff signal 13 is output to the regulator section 42 to cut off the power (step S9 in FIG. 2). Instead of this power cutoff, it is also possible to protect the load on the printed circuit board 20 using the "foldback" characteristic.

On the other hand, if I≦■L, the microcomputer 14 determines that the overcurrent detected in the previous step S5 is temporary and not abnormal, and in step S5
and 1≦1. In the same way as when it is determined that
6. Perform time over check. And step S
When a time-over is detected in step 6, the microcomputer 14 returns to steps Sl and S2 and executes the current limit value setting process again. In this way, by repeating the current limit value setting process every fixed cycle, even if there is a slight variation in the load condition on the printed circuit board 20, the current limit value I that matches the latest load condition can be set. can do.

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

Now, with the DC power supply 10 powered on,
It is assumed that the printed circuit board 20 is inserted into the connector 21. At this time, the actuator of the microswitch 22 is pressed by the contact 23 of the printed circuit board 20, and the microswitch 22 is turned on. The on signal of the microswitch 22 is input to (the interrupt input terminal of) the microcomputer 14 via the signal line 24 as an interrupt signal for notifying the hot-wire replacement of the printed circuit board 20.

When the microcomputer 14 receives an interrupt signal via the signal line 24, that is, when it detects that the printed circuit board 20 or the connector 21 has been inserted, the microcomputer 14 executes the third overcurrent detection routine instead of the overcurrent detection routine shown in FIG. The overcurrent detection routine shown in the figure is executed as follows.

First, the microcomputer 14 has an A/D conversion circuit 12.
The load current detection value (load current value) ■ is read from (step 5ll in FIG. 3), and the operation of checking whether the read load current detection value I exceeds the predetermined current limit value ILI ( FIG. 3 step 512),
Repeat execution until it is determined that I > I L. This current limit value ILI is a necessary and sufficient value to detect the flow of a transient overcurrent (rush current) when the printed circuit board 20 is replaced with a hot wire.

The microcomputer 14 performs I in step S12 above.
〉 If we judge the work L1 and determine that a temporary overcurrent has started flowing due to the hot replacement of the printed circuit board 2o, we can determine whether this overcurrent is truly temporary (such as a short circuit). In order to check whether there is an abnormal overcurrent due to an accident, the load current detection value I is read again from the A/D conversion circuit 12 after a certain period of time (step 813 in FIG. 3). Next, the microcomputer 14 determines that the load current detected value read in step 313 is a current limit value I L2 (here I L2 > I Ll) that is predetermined corresponding to the power supply rated capacity of the DC power supply 10. It is checked whether it exceeds the limit (step 514 in FIG. 3).

If the determination in step S14 is I≦IL2, the microcomputer 14 determines that a temporary overcurrent is flowing through the printed circuit board 20 due to the hot wire replacement, and that there is no abnormality. , the routine returns to the normal overcurrent detection routine shown in FIG. On the other hand, if I>IL2, the microcomputer 14 determines that a non-transient abnormal overcurrent is flowing through the printed circuit board 20 due to a short circuit accident on the printed circuit board 20, and sends the power cutoff signal 13. The signal is output to the regulator section 42 to cut off the power (step 515 in FIG. 3).

In the above embodiment, in the normal state, if it is detected that the load current detection value I exceeds the current limit value IL twice in a row, it is assumed that a non-transient overcurrent has flowed and the power supply is shut off. Although the case has been described in which the power supply is exceeded three or more times in a row, it is also possible to shut off the power supply. The same applies to overcurrent detection during hot replacement of a printed circuit board, and even if the power is shut off if it is detected that the load current detection value I has exceeded the current limit value IL2 several times in a row. good. Further, in the embodiment, the printed circuit board 20 to the connector 21 is
Although the case has been described in which the insertion of the printed circuit board 20 (hot replacement of the printed circuit board 20) is detected by the microswitch 22, the present invention is not limited to this, and it is also possible to detect it optically, for example.

[Effects of the Invention] As detailed above, according to the present invention, in a normal state, the first current limit is set according to the load in use based on the current flowing through the load on the printed circuit board actually used. The value (IL) is automatically set at regular intervals, and overcurrent detection is performed based on this set limit value, so if an overcurrent flows through the load due to an abnormality in the load being used, the power supply Unlike conventional methods, overcurrent detection can now be performed even within the fixed current limit value corresponding to the rated capacity.In other words, it is now possible to perform overcurrent detection with high efficiency according to the load in use, making it possible to detect Regardless of whether the load can be adequately protected.

Therefore, according to this invention, in order to properly protect the load in use, it is no longer necessary to select a power supply device with a power supply rated capacity that matches the size of the load in use, as in the past, and as long as the maximum capacity of the power supply is not exceeded. , the same power supply device can be used regardless of the size of the load used. Also, for the same reason,
When multiple power supplies are required for one system, the same type of power supplies can be used.

Further, according to the present invention, when replacing a printed circuit board with a hot wire, instead of overcurrent detection based on the first current limit value, the second current limit value, which is a fixed current limit value corresponding to the rated capacity of the power supply, is detected. Since the configuration is configured to perform overcurrent detection based on the limit value (I L2), it is possible to prevent false overcurrent detection due to the occurrence of transient overcurrent associated with hot wire replacement. Abnormal overcurrent caused by accidents such as short circuits can be reliably detected to prevent fires and the like.

[Brief explanation of 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 during hot replacement of a printed circuit board, and FIG. FIG. 4 is a block diagram showing a conventional example. 10... DC power supply device, 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... Micro switch (live wire exchange detection means)
, 41...Ac-Dc conversion unit, 42...regulator unit. No. 1 [1 Applicant's agent Patent attorney Takehiko Suzue Figure 4 Figure 4

Claims (3)

[Claims] (1) comprising a DC power supply device and a hot-line replacement detection means for detecting and notifying the power supply device that a printed circuit board to which DC power is supplied from the DC power supply device has been hot-replaced; The above DC power supply device includes a current detection means for detecting an output current from the power supply device;
a setting means for setting a first current limit value corresponding to an average current value of the output current detected by the current detection means at approximately regular intervals in a normal state; a first overcurrent detection means for detecting that an overcurrent is flowing through the printed circuit board by comparing the latest first current limit value and the detection result of the current detection means; , when the hot line replacement detection notification is sent from the hot line replacement detection means, the detection result of the current detection means is compared with a predetermined second current limit value corresponding to the rated capacity of the DC power supply device; and a second overcurrent detection means for detecting that an overcurrent is flowing through the printed circuit board, and under normal conditions, the first current limit value dynamically set by the setting means is used. Performs overcurrent detection,
An overcurrent detection method characterized in that when a printed circuit board is hot-wired replaced, overcurrent detection is performed using a fixed second current limit value corresponding to the rated capacity of the DC power supply. (2) When the first overcurrent detection means detects multiple times in succession at approximately constant time intervals that the output current detected by the current detection means exceeds the first current limit value; 2. The overcurrent detection method according to claim 1, wherein it is determined that an overcurrent is flowing. (3) The second overcurrent detection means determines that the detection result of the current detection means is a predetermined third current limit value (however, when the hot wire replacement detection means notifies the detection of the hot wire replacement, Overcurrent detection according to claim 2, characterized in that overcurrent detection is performed using the second current limit value as a reference after a predetermined time after the third current limit value<second current limit value) is exceeded. method.