JPH0980106A - Floating DC power supply abnormality detection device - Google Patents

Abstract

(57) [Summary] [Purpose] To detect the ground fault and / or power supply voltage of a floating DC power supply with a simple configuration. [Structure] Four reference resistance elements Ra, Rb, Rc, Rd are connected in series between the positive and negative electrodes of a floating DC power supply E0, and two resistance elements Ra, Rd on the positive and negative electrode sides and two intermediate resistances are connected. A series resistance circuit 1 in which the resistance values of the elements Rb and Rc are set equal to each other, and a circuit independent of the series resistance circuit 1,
A reference voltage application circuit 2 is provided which applies a reference DC voltage to a connection point between two resistance elements Rb and Rc in the middle of the series resistance circuit and grounds a part of the circuit. Resistance element R of series resistance circuit
The potential Vab at the connection point of a and Rb and the resistance elements Rc and Rd
The potential Vcd at the connection point is added in phase, and the ground fault of the floating DC power supply is detected based on the variation in the added value in phase. Similarly potential V
The ab and Vcd are differentially amplified, and the voltage of the floating DC power supply is detected based on the variation of the differential amplification value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting device for a floating DC power supply, and more particularly to an abnormality detecting device for detecting a ground fault and / or a power supply voltage of a wiring system in a high voltage floating DC power supply used in an electric vehicle or the like.

[0002]

2. Description of the Related Art Generally, in an AC distribution system, an AC ground is formed, so that a closed circuit is formed when a leakage occurs due to a ground fault of a power source, and therefore a ground fault can be detected.

However, in a DC power distribution system in which a power source is used in a floating state, even if one electrode of the power source is grounded to the frame, the ground, etc., a closed circuit is not formed, so that the ground fault cannot be detected. . In this respect, Japanese Patent Application Laid-Open No. 6-308,185 proposes a technique for detecting the occurrence of leakage, the location of leakage, and the DC power supply voltage.

[0004]

However, in this prior art, the power supply voltage is divided by the detection resistor and the protection resistor, and both ends of the protection resistor are short-circuited or opened by the switch to detect the output at each time point. The circuit configuration is complicated because the sum and difference are calculated and compared.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and a floating DC power supply abnormality detecting device capable of easily detecting the ground fault and / or power supply voltage of the floating DC power supply. Is to provide.

[0006]

In order to achieve the above object, according to the present invention, four reference resistance elements Ra, Rb, Rc and Rd are connected in series between the positive and negative electrodes of a floating DC power source E0. , A series resistance circuit (1) in which the resistance values of the two resistance elements Ra and Rd on the positive and negative electrode sides and the resistance values of the middle two resistance elements Rb and Rc are set to be equal to each other, and the series resistance circuit (1). And the two resistance elements R in the middle of the series resistance circuit (1).
A reference DC voltage is applied to the connection point of b and Rc, and a reference voltage applying circuit (2) in which a part of the circuit is grounded is provided and is located on the positive electrode side of the floating DC power supply E0.
The potential Vab at the connection point of the resistance elements Ra and Rb and the potential Vcd at the connection point of the two resistance elements Rc and Rd located on the negative electrode side are added in-phase, and the floating DC Means (3) for detecting a ground fault of the power source E0, and two resistance elements R located on the positive electrode side of the floating DC power source E0
a potential Vab at the connection point of a and Rb, and 2 located on the negative electrode side
The floating DC power supply E is differentially amplified with the potential Vcd at the connection point of the resistance elements Rc and Rd, and based on the variation of the differential amplification value.
It is characterized in that it is configured to include at least one of means (9) for detecting a voltage of zero.

In the above, the floating DC power source E0
The means (3) for detecting the ground fault and the means (9) for detecting the voltage thereof are not essential, and only one of them is sufficient. In that sense, the claims have been described as “to include at least one”.

First, the principle of the abnormality detecting device according to the present invention will be described as follows.

That is, as shown in FIG. 2, four reference resistance elements Ra, Rb, are provided between the positive and negative electrodes of the floating DC power source E0.
Rc and Rd are connected in series, and two resistance elements Ra and Rd on the positive and negative electrode sides and two resistance elements R in the middle are provided.
Consider a series resistance circuit (20) in which the resistance values of b and Rc are set equal to each other.

Here, the potential at the connection point of the two resistance elements Ra and Rb located on the positive electrode side of the floating DC power supply E0 is Va.
b, the potential at the connection point of the two resistance elements Rb and Rc in the middle is Vbc, the potential at the connection point of the two resistance elements Rc and Rd on the negative side is Vcd, and the current of the circuit is I0, the potential is Vab and Vcd are set to Vab = Vbc + Rb × I0 Vcd = Vbc−Rc × I0 = Vbc−Rb × I0, with the negative potential of the power source E0 as a reference.

Next, as shown in FIG. 3, the positive electrode side of the DC power source E1 is connected to the connection point of the two intermediate resistance elements Rb and Rc, and a closed circuit is formed via the resistance element Rx. Consider a case where the reference voltage applying circuit (30) is formed and the negative side of the power source E1 in the reference voltage applying circuit (30) is grounded to a frame, a casing, or the like. Then, since the potential Vbc seen from the negative side of the power source E1 is Vbc = E1, the potentials Vab and Vcd can be expressed as Vab = E1 + Rb × I0 Vcd = E1-Rb × I0, respectively.

In the above, when the potentials Vab and Vcd are added in phase, the output becomes 2E1. When the negative side of the floating DC power supply E0 in the series resistance circuit (20) is grounded, the negative side of the power supply E0 of the series resistance circuit (20) and the negative side of the power supply E1 of the reference voltage applying circuit (30) are connected. Will be done. At this time, of the potential of each part of the series resistance circuit (20) viewed from the negative side of the power source E1, Vbc
Does not change with E1, but the current values flowing through the resistance elements Ra and Rb and the current values flowing through Rc and Rd become unbalanced and different, so the potentials Vab and Vcd increase and decrease.

Therefore, the in-phase added value of the potentials Vab and Vcd changes greatly with respect to 2E1, and the ground fault of the floating DC power source E0 can be detected by detecting this. These operations are the same when the positive side of the floating DC power source E0 is grounded. The magnitude of the in-phase added value with respect to 2E1 is used for recognizing the polarity of the power line that is grounded,
The magnitude of the in-phase added value corresponds to the resistance value that is grounded.

On the other hand, with the floating DC power supply E0 in the series resistance circuit (20) not being grounded, the potentials Vab and V
When cd and cd are differentially amplified, the output becomes a value obtained by amplifying 2Rb × I0. Since Rb is a constant value and I0 changes depending on the value of the power supply voltage E0, the power supply voltage E0 can be detected by monitoring the output value after the differential amplification.

[0015]

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

In the figure, (1) is a series resistance circuit, in which four reference resistance elements Ra, Rb, Rc, and Rd are connected in series between the positive and negative electrodes of the series power source E0. The resistance value of the two resistance elements Ra and Rd on the positive and negative electrode sides and the resistance value of the two middle resistances Rb and Rc are Ra = R.
d and Rb = Rc are set. The DC power supply E0 is, for example, a high voltage power supply of 200 to 600 V, and both the positive and negative electrodes are used in a floating state (so-called floating state). For example, a DC motor or the like is connected to this power source (not shown).

(2) is a reference voltage application circuit having a reference DC power source E1 of a low voltage of about 5V. The reference power supply E1 of the reference voltage application circuit (2) has two positive resistance sides R in the middle of the series resistance circuit (1).
The negative side of the power source E1 is connected to the connection point of b and Rc, and is grounded to a frame, a casing, etc., and is configured as an independent circuit different from the series resistance circuit (1).
Therefore, when the floating DC power supply E0 is not grounded, the resistance R when viewed from the negative electrode side of the reference DC power supply E1
The potential Vab between a and Rb and the potential Vcd between the resistors Rc and Rd are Vab = E1 + Rb * I0 Vcd = E1-Rb * I0, where I0 is the current of the series resistance circuit (1).

Reference numeral (3) is a ground fault detecting means, which is output through the impedance converters (4) and (5).
An in-phase adder (6) for adding in-phase two potentials Vab and Vcd is provided. The in-phase adder (6) is composed of an operational amplifier and a resistance element for operating the operational amplifier. Also, the impedance converters (4) and (5)
Is also composed of an operational amplifier. The output of the in-phase adder (6) is A / D converted by the A / D converter (7) and input to the CPU (8), and the CPU (8) monitors the input value as described later, The ground fault state of the floating DC power supply E0 is determined according to the variation.

Reference numeral (9) is a power supply voltage detecting means for detecting the voltage of the floating DC power supply E0, which comprises a differential amplifier (10), a reference voltage generator (11) and a gain adjuster (12). The differential amplifier (10) has two potentials V output via the impedance converters (4) and (5).
The ab and Vcd are differentially amplified. Further, the reference voltage generator (11) divides the voltage Vcc based on the voltage division ratio of the voltage dividing resistors (11a) and (11b) and outputs it as a reference voltage.

The gain adjuster (12) is connected to the output of the differential amplifier (10) and the resistors (11a) and (11b).
The reference voltage of the reference voltage generator (11) determined by the above is compared, and the difference is amplified with an appropriate gain and output. Each of the differential amplifier (10), the reference voltage generator (11), and the gain adjuster (12) is composed of an operational amplifier and a resistance element for operation.

Next, the operation of the abnormality detecting device according to the illustrated embodiment will be described.

As described above, the potential Vab between the resistors Ra and Rb and the potential Vcd between the resistors Rc and Rd when viewed from the negative side of the reference DC power source E1 are: Vab = E1 + Rb × I0 Vcd = E1-Rb × Since it is expressed as I0, the output of the in-phase adder (6) is a value obtained by adding in-phase the potentials Vab and Vcd. The output of the in-phase adder (6) is obtained by the A / D converter (7). A / D
It is converted and compared with the reference value 2E1 by the CPU (8). Since the output of the in-phase adder (6) is 2E1 which is equal to the reference value 2E1 when the series resistance circuit (1) is not grounded, the CPU determines that no ground fault has occurred.

Next, when the negative side of the floating DC power supply E0 in the series resistance circuit (1) is grounded, the negative side of the power supply E0 and the negative side of the reference power supply E1 in the reference voltage applying circuit (2) are connected. Therefore, the current flowing through the resistance element Rb increases and the current flowing through Rc decreases. Therefore, the value obtained by adding the potentials Vab and Vcd in phase is larger than 2E1, and this is judged by the CPU (8), and it is detected that the negative side of the power source E0 is grounded.

Next, the power source E in the series resistance circuit (1)
When the positive side of 0 is grounded, the same state as when the positive side of the power supply E0 and the negative side of the reference power supply E1 in the reference voltage application circuit (2) are connected is obtained, so the current flowing through the resistance element Rb decreases, The current flowing through Rc increases. Therefore,
The value obtained by adding the potentials Vab and Vcd in phase is smaller than 2E1, and this value is judged by the CPU (8) and the power supply E0
It is detected that the positive electrode side of has a ground fault.

By monitoring the low voltage output of the in-phase adder (6) in this way, the ground fault of the floating high voltage DC power supply E0 in the series resistance circuit (1) can be detected.

On the other hand, when the series resistance circuit (1) is not grounded, the output of the differential amplifier (10) is 2Rb × I0.
Becomes the amplified value, and this value and the reference voltage generator (11)
Is compared with the reference voltage by the gain adjuster (12). Here, the resistance value Rb is constant, and the current I0 flowing through the series resistance circuit (1) changes depending on the magnitude of the voltage value of the floating DC power supply E0.

As described above, the gain adjuster (12) is connected to the output of the differential amplifier (10) and the reference voltage generator (1).
Since the reference voltages according to 1) are compared and the difference is amplified and output, the change in the power supply voltage can be monitored with high accuracy.

In the illustrated embodiment, the negative side of the power source E1 of the reference voltage applying circuit (2) is grounded to the frame or the like, but the positive side of the power source E1 may be grounded. good. In this case, conversely to the above, when the negative side of the power supply E0 in the series resistance circuit (1) is grounded, the output of the in-phase adder (6) becomes smaller than 2E1 and the power supply E
When the positive electrode side of 0 is grounded, it becomes larger than 2E1,
The ground fault of the power source can be determined in the same manner as described above.

In the voltage detecting means (9), the output of the differential amplifier (10) is detected with high accuracy by the gain adjuster (12). good. Further, the configurations of the in-phase adder (6) and the differential amplifier (10) are not limited to those shown in the drawings.
The point is that the two potentials Vab and Vcd of the series resistance circuit (1) are differentially amplified or added in phase, and the ground fault or voltage of the floating DC power supply E0 is detected based on the result.

[0030]

According to the present invention, the two potentials Vab and Vcd of the series resistance circuit are added in-phase or differentially amplified,
Since the ground fault and / or the voltage of the floating DC power supply is detected based on the variation of those values, the ground fault and / or the voltage of the floating DC power supply can be detected with an extremely simple configuration.

In addition, the in-phase added value fluctuates on the basis of twice the DC voltage value applied to the connection point of the two resistance elements Rb and Rc in the middle of the DC resistance circuit, so that the DC voltage value is low. By setting the voltage, the handling voltage in the ground fault detecting means can be lowered. Further, since the differentially amplified value also becomes a low voltage, the handling voltage in the voltage detecting means can be lowered. Therefore, even if the floating DC power supply has a high voltage, the ground fault and / or the voltage of the floating DC power supply can be detected by the low voltage processing.

Although the voltage detecting means and the ground fault detecting means are provided in the above description, they are not essential, and only one of them may be provided.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram for explaining the operating principle of the present invention.

FIG. 3 is a circuit diagram for explaining the operating principle of the present invention.

[Explanation of symbols]

 1 series resistance circuit 2 reference voltage application circuit 3 ground fault detection means 6 in-phase adder 9 voltage detection means 10 differential amplifier E0 floating DC power supply

Claims (1)

[Claims] 1. Four reference resistance elements Ra, Rb, Rc, Rd are connected in series between the positive and negative electrodes of the floating DC power supply E0, and two resistance elements Ra, Rd on the positive and negative electrode side and in the middle. A series resistance circuit (1) in which resistance values of the two resistance elements Rb and Rc are set to be equal to each other, and a circuit configured independently of the series resistance circuit (1). A reference voltage application circuit (2) in which a reference DC voltage is applied to a connection point between two resistance elements Rb and Rc in the middle of 1) and a part of the circuit is grounded.
And a potential Vab at the connection point between the two resistance elements Ra and Rb located on the positive side of the floating DC power supply E0 and a connection point between the two resistance elements Rc and Rd located on the negative side. Means (3) for in-phase addition of the potential Vcd and detecting a ground fault of the floating DC power supply E0 based on the variation of the in-phase addition value, and two resistance elements Ra located on the positive side of the floating DC power supply E0. The potential Vab at the connection point of Rb and the potential Vcd at the connection point of the two resistance elements Rc and Rd located on the negative electrode side are differentially amplified, and the floating DC current E0 of the floating DC current E0 is changed based on the variation of the differential amplification value. An apparatus for detecting an abnormality in a floating DC power supply, comprising at least one of a means (9) for detecting a voltage.