JPH05207655A - Output overcurrent cause detecting circuit for power supply - Google Patents

Abstract

PURPOSE:To make a quick decision whether the cause of overcurrent exists on the power supply side or on the load side by detecting the output voltage simultaneously with overcurrent. CONSTITUTION:If an overcurrent detecting circuit 6 detects an overcurrent when the output voltage of a DC power supply 3 is normal, a first logic circuit 13 produces an alarm. It is an abnormal load signal meaning that a load 4 is abnormal. On the other hand, a second logic circuit 14 produces an alarm signal when an overvoltage is produced from the DC power supply 3 and an overcurrent is fed therefrom. This cause is the constant voltage sustaining function of the DC power supply 3, and becomes power supply abnormal signal. Since a quick decision can be made whether the cause of overcurrent exists on the power supply side or on the load side by additionally providing an output voltage detecting means for the power supply and a simple logic circuit, the cause of abnormality can be found easily and power supply stop interval can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for determining whether the cause of an overcurrent of a power supply device that supplies power to a load while maintaining an output voltage at a predetermined value is the power supply device or the load. The present invention relates to an output current excess cause detection circuit of a device.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional example of overcurrent detection of a power supply device. In this conventional circuit, the DC power supply device 3 is composed of, for example, a rectifier and a chopper,
The AC power from the AC power supply 2 is converted into DC power having a constant voltage and is supplied to the load 4. By the way, the heat capacity of the semiconductor switch element that constitutes the DC power supply device 3 is extremely small, and if there is an overcurrent, the junction temperature may rise rapidly and be destroyed. Therefore, the output current of the DC power supply device 3 is set to a set value. DC power supply 3
Must be equipped with an overcurrent protection device that reduces or interrupts the output current. Therefore, the output circuit of the DC power supply device 3 is provided with a DC current transformer 5 for constantly monitoring the current, and the current detected by the DC current transformer 5 becomes an overcurrent larger than a predetermined value. It is well known that when this is detected by the overcurrent detection circuit 6 configured by a comparator or the like, the load 4 is disconnected from the DC power supply device 3 by operating a circuit breaker (not shown).

[0003]

As described above, conventionally, when the output current of the DC power supply device 3 becomes an overcurrent more than a set value, the DC power supply device 3 is simply cut off in order to protect the output current. Met. The abnormality of the load 4 can be mentioned as a cause of the overcurrent, but the output voltage of the DC power supply 3 suddenly rises due to the abnormality, which may cause a large current to flow to the load. That is, it is impossible for the conventional overcurrent detection device to determine whether the cause of the overcurrent is the DC power supply device 3 or the load 4. On the other hand, if the cause of the overcurrent is not eliminated, the DC power supply 3
However, since the cause of the overcurrent generation is unknown in the conventional overcurrent detection device as described above, not only it takes manpower and time to search the cause, but also the DC power supply device during that period. There is also an inconvenience that the load 3 and the load 4 cannot be used.

Therefore, an object of the present invention is to make it possible, when the output current of a power supply device becomes an overcurrent, to quickly determine whether the cause of the overcurrent is the power supply device side or the load side. is there.

[0005]

In order to achieve the above object, the output current excess cause detection circuit of the power supply device of the present invention is a power supply device which maintains an output voltage at a predetermined value and supplies power to a load. Current detection means for detecting the output current of the power supply device, overcurrent detection means for detecting whether or not the detected current exceeds an overcurrent set value, and voltage detection means for detecting the output voltage of the power supply device, An overvoltage detecting means for detecting whether the detected voltage exceeds an overvoltage set value higher than the predetermined value, and a first logic circuit for outputting a load abnormality signal if an overcurrent is detected without detecting the overvoltage. A second logic circuit that outputs a power supply device abnormality signal when the overvoltage is detected and the overcurrent is detected, or a voltage differential calculation means that further calculates a differential value of the power supply device output voltage, and this differential calculation value A first logic circuit for outputting a load abnormality signal if an overcurrent is detected without detecting the overvoltage, by providing a differential value detection means for detecting whether the overvoltage or the set value is exceeded. If the above differential value is detected and the overcurrent is detected, a power supply device abnormality signal is output.
And a logic circuit.

[0006]

When the power supply device has no abnormality and the load side causes an overcurrent, the power supply device output voltage exhibits a steady value or a value lower than the steady value, but if the power supply device output voltage becomes excessive, This causes overcurrent to flow to the load. Therefore, according to the present invention, when an overcurrent of the power supply device is detected, the output voltage of the power supply device is also detected at the same time. Judge that it is on the load side. on the other hand,
If the overvoltage is detected at the same time when the overcurrent is detected, it is determined that the cause of the overcurrent is the power supply unit side. Furthermore, when connecting a capacitive load such as a capacitor, it is not possible to judge only by the absolute value of the output voltage.Therefore, a voltage differential value detection means is provided, and the voltage change rate (dV / dt) is large when overcurrent is detected. if there is,
Even if the overvoltage is not detected, it is determined that the power supply unit is abnormal, so that the cause of the overcurrent can be more accurately pursued.

[0007]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The AC power supply 2, the DC power supply device 3, the load 4, and the DC current transformer shown in the circuit of the first embodiment are shown. 5, and the names, applications, and functions of the overcurrent detection circuit 6 are the same as those of the conventional circuit described above with reference to FIG. This first embodiment circuit includes a voltage detector 11 for detecting the output voltage of the DC power supply device 3 in the conventional circuit shown in FIG. 3 and an overvoltage higher than a predetermined value. The overvoltage detection circuit 12 for detecting, the 1st logic circuit 13, and the 2nd logic circuit 14 are added and comprised.

The first logic circuit 13 is composed of a logical product element 13A and a signal inverting element 13B, and the overvoltage detection circuit 1
The overvoltage detection signal output by 2 is input to the logical product element 13A via the signal inverting element 13B, and the overcurrent detection signal from the overcurrent detection circuit 6 is input to the logical product element 13A. Therefore, when the overcurrent detection circuit 6 detects an overcurrent although the output voltage of the DC power supply device 3 is not an overvoltage (that is, a normal state), the first logic circuit 13 outputs an alarm signal. To do. Detecting an overcurrent even though the output voltage of the DC power supply device 3 is normal means that an overcurrent state has occurred due to the occurrence of an abnormality in the load 4. That is, the output signal of the first logic circuit 13 is a load abnormality signal.

The second logic circuit 14 is composed of a logical product element 14A, and the logical product element 14A receives an overcurrent detection signal from the overcurrent detection circuit 6 and an overvoltage detection signal from the overvoltage detection circuit 12. input. Therefore, the second logic circuit 14 outputs the alarm signal when the output voltage of the DC power supply device 3 becomes an overvoltage and the output current becomes an overcurrent. It is considered that this overcurrent is caused by the failure of the constant voltage maintaining function of the DC power supply device 3 and the increase of its output voltage. Therefore, the output signal of the second logic circuit 14 is a power supply device abnormality signal.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The AC power supply 2, the DC power supply 3, the load 4, and the DC current transformer 5 shown in the circuit of the second embodiment. The names, applications, and functions of the overcurrent detection circuit 6, the voltage detector 11, the overvoltage detection circuit 12, and the first logic circuit 13 are the same as those in the first embodiment circuit described above with reference to FIG. Although the description of the second embodiment circuit is omitted, the second embodiment circuit is different from the first embodiment circuit described above in that it has a voltage differentiating circuit 21 for detecting a change in the output voltage of the DC power supply device 3, and this voltage differential value is a predetermined value or more. Differential value detection circuit 22 for detecting whether or not, and third logic circuit 2
3 and 3 are added and configured.

In the circuit of the first embodiment described above, the absolute value of the output voltage of the DC power supply 3 is detected. From the logical product of the fact that this is an overvoltage and the overcurrent of the output current, the cause of the overcurrent is the power supply. However, if the load 4 is a capacitor or the like, it cannot be determined only by the absolute value of the voltage. Because, when the capacitor capacity is C and the voltage is V, the capacitor current I _C is I _C = C (dV
/ Dt), the capacitor current I _C
Will depend on the magnitude of the voltage differential value. Therefore, by considering not only the absolute value of the voltage output from the DC power supply device 3 but also the voltage change rate, the cause of the overcurrent can be pursued more accurately and more quickly. Therefore, the second embodiment circuit shown in FIG. 2 is provided with a third logic circuit 23 composed of an AND element 23A and an OR element 23B, and an overvoltage detection signal from the overvoltage detection circuit 12 and a differential value detection circuit 2 are provided.
The voltage differential value detection signal from 2 is supplied to the logical sum element 23B, and the output signal of the logical sum element 23B and the overcurrent detection signal output from the overcurrent detection circuit 6 are supplied to the logical product element 23A.

With such a circuit configuration, even if the overvoltage detection circuit 12 does not detect the overvoltage, if the output voltage of the DC power supply 3 fluctuates rapidly, the voltage change speed,
That is, since the differential value detection circuit 22 detects that dV / dt is large, if the overcurrent detection circuit 6 detects an overcurrent at this time point, the third logic circuit 23 outputs a power supply device abnormality signal and issues an alarm. Emit. Since the operation of the first logic circuit 13 is the same as that of the circuit of the first embodiment described above, its operation description is omitted.

[0013]

When the output current of the power supply device that supplies power to the load while maintaining the output voltage at a predetermined value becomes an overcurrent, conventionally, the cause of this overcurrent is on the power supply device side, or is it the cause? Since it is unclear whether or not it is on the load side, it takes time and labor to search for the cause, and there is a disadvantage that this power supply cannot be used during that period. It is possible to immediately determine whether the cause of the overcurrent is on the power supply side or the load side by adding a simple logic circuit and the The effect that can be obtained is obtained. Furthermore, by adding a means for detecting the differential value of the power supply device output voltage and a simple logic circuit, when a load having the property of rushing in power such as a capacitor is connected to this power supply device, an Even if the power supply output voltage has not reached the overvoltage setting value when the current state is detected, if the voltage differential value is large, a power supply abnormality signal is output and an alarm is issued to detect the cause of overcurrent. It is possible to obtain the effect of facilitating the pursuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example of overcurrent detection of a power supply device.

[Explanation of symbols]

 2 AC power supply 3 DC power supply device 4 Load 5 DC current transformer 6 Overcurrent detection circuit 11 Voltage detector 12 Overvoltage detection circuit 13 First logic circuit 13A AND element 13B Signal inversion element 14 Second logic circuit 14A AND element 21 Voltage differentiation circuit 22 Differentiation value detection circuit 23 Third logic circuit 23A AND element 23B OR element

Claims (2)

[Claims] 1. A power supply device for supplying electric power to a load while maintaining an output voltage at a predetermined value, and current detection means for detecting an output current of the power supply device and whether or not the detected current exceeds an overcurrent set value. An overcurrent detecting means for detecting whether or not, a voltage detecting means for detecting an output voltage of the power supply device, and an overvoltage detecting means for detecting whether or not the detected voltage exceeds an overvoltage set value higher than the predetermined value, A first logic circuit that outputs a load abnormality signal if an overcurrent is detected without detecting the overvoltage, and a second logic circuit that outputs a power supply apparatus abnormality signal if the overvoltage is detected and an overcurrent is detected. A circuit for detecting a cause of an excessive output current of a power supply device, which is provided. 2. A power supply device for supplying power to a load while maintaining an output voltage at a predetermined value, and current detection means for detecting an output current of the power supply device, and whether or not the detected current exceeds an overcurrent set value. An overcurrent detecting means for detecting whether or not, a voltage detecting means for detecting an output voltage of the power supply device, and an overvoltage detecting means for detecting whether or not the detected voltage exceeds an overvoltage set value higher than the predetermined value, If the voltage differential calculation means for calculating the differential value of the power supply device output voltage, the differential value detection means for detecting whether this differential calculation value exceeds the set value, and the overcurrent without detecting the overvoltage, It is provided with a first logic circuit that outputs a load abnormality signal, and a third logic circuit that outputs a power supply apparatus abnormality signal if either the overvoltage or the differential value greater than a set value is detected and an overcurrent is detected. Characterized by Output current excessive cause detection circuit source device.