JPH05142267A - Device for detecting current in high voltage power source - Google Patents

Abstract

PURPOSE:To make expensive insulating members and high withstand voltage cables useless, and to obtain a structurally simple, cheap, safe and very reliable device. CONSTITUTION:A high voltage power source PS1 and a load RL have a ground line for common use. The load RL is the device (DUT) to be measured such as an IC, transistor, etc., in which the measurement of a leak current is required, and one end of the load RL is connected to the source PS1 and the other end to the line L through a resistor R for detecting a current. An amplifier A2 constituting a voltage detecting circuit DT for detecting the potential difference VL generating between the ends of the resistor R is connected to both ends, and the leak current IL flowing through the load RL is found from, the output. Thus, high voltage is not applied to the circuit DT, because the current detecting resistor is connected to the return side of the load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detection device for a high voltage power supply, and more particularly to an improved current detection circuit for measuring a leakage current of an IC or a transistor.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of a current detecting device in a high voltage power supply. The high voltage power supply PS ₁ and the load R _L are connected with the ground line L in common. One end of the load R _L is connected to the ground line L, and the other end is connected to the high voltage power supply PS ₁ via the current detection resistor R. The current detection circuit DT is composed of a current detection resistor R and an amplifier A ₂ for detecting a potential difference generated in the resistor R, and obtains a leak current flowing through the load R _L from its output. Since the amplifier A ₂ handles at most several V to several tens of V as a detection voltage, a general IC
Although an operational amplifier is often used, the current detection resistor R
Is on the high voltage line H (hot line H) side,
The B power supply PS ₂ is a floating power supply.

[0003]

As described above, in the conventional current detecting device, the current detecting resistor R is inserted not on the ground line L side but on the hot line H side. Therefore, since a high voltage is applied to the amplifier A _2, the floating power supply is required to power the amplifier A ₂ as described above must be subjected to following troublesome insulating measures.

As shown in FIG. 4, the power supply PS ₂ for the amplifier A _{2 is} placed on the power supply chassis 1 in which the ground of the high-voltage power supply is dropped in order to insulate and float the power supply chassis 1.
Are provided via an insulating plate 2 made of a bake plate, a Teflon plate, or the like, and a sub-board 3 on which the current detection circuit DT is mounted is also provided via an insulating mount 4. Amplifier A ₂
A high voltage of approximately several kV is normally applied to the ± B power supply line and the GND line 5 drawn from the power supply PS ₂ for the amplifier A ₂ to the amplifier A ₂ , so a high withstand voltage wire that withstands this high voltage is required. become. For these electric wires 5, in reality, special high-voltage special electric wires of 10 to 20 kV, which are called expensive UL electric wires, are actually used. Further, in order to prevent the electric wires 5 from coming into contact with the chassis 1 and other low-voltage parts to cause an insulation failure accident, a high withstand voltage supporting rod 6 for bundling the electric wires 5 and floating them from the chassis 1 is also used. ing. It should be noted that the amplifier A ₂ is configured so that the voltage across the current detection resistor R is a voltage follower 1 as shown in FIG.
The differential amplifier 13 receives the difference between the two outputs to obtain a difference voltage having a small voltage value.
The high voltage is applied only up to the second stage differential amplifier 13 because it is received and output to the A / D converter. As described above, in the past, not only insulating members and expensive high-voltage wires have been required as insulation measures for current detection circuits, but also the mounting structure has been complicated, and the high voltage poses a risk for inspection and maintenance work. Along with this, there is a problem in terms of reliability because dust is easily adsorbed.

An object of the present invention is to provide a current detection device in a high voltage power supply which eliminates the above-mentioned drawbacks of the prior art by bringing a current detection circuit on the return side of a load and which does not require insulation measures. It is in.

[0006]

A current detection device for a high-voltage power supply according to the present invention comprises a high-voltage power supply having a load and a ground line in common, and a high voltage is applied to the load from the high-voltage power supply to connect a current in series to the load. A current detection device in a high-voltage power supply that detects the potential difference across the detection resistor with a detection circuit and finds the current flowing to the load from this detection output.The current detection resistor is provided between the load and the ground line. is there.

[0007]

If the current detection resistor is provided on the ground line side, the detection circuit will not receive a high voltage. For that purpose, the current detection resistor may be inserted in the ground line having the lowest potential. However, since a current flows into the ground line not only from the self-system circuit but also from the other system circuit, the resistor cannot be inserted. This is because if a resistor is inserted, the ground level, which is the reference, fluctuates, resulting in a significant drop in accuracy and the inability to detect current, as well as the circuit itself not functioning. Therefore, as in the present invention, when the current detection resistor is inserted between the return side of the load, that is, between the load and the ground line, the ground level of the ground line can be maintained,
Since the high voltage is absorbed by the load, the voltage applied to the detection circuit also decreases. As a result, insulation measures around the detection circuit are not required.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a leak current detection device used in a semiconductor test device or the like. The high voltage power supply PS ₁ and the load R _L are connected with the ground line L in common. High voltage power supply P
S ₁ is, for example, a programmable power supply whose output voltage can be arbitrarily set, and an amplifier A having a ± B power supply with its midpoint grounded.
It is composed of ₁ and can take out a high voltage although it takes a little current. For example, ±
A maximum current of 1 mA can be applied at 2 kV. The load R _L is a device under test (DUT) such as an IC or a transistor that is required to measure a leak current, one end of which is a high voltage power supply P
It is connected to the output of S ₁ and the other end is connected to the ground line L via the current detection resistor R. The current detection resistor R that constitutes the current detection circuit DT is configured with a precision resistor having a considerably large value in order to detect the potential difference caused by the leak current of the load R _L with high precision. Although it varies depending on the DUT, it is usually set to about 10 MΩ so that a potential difference of about 10 V is generated at both ends when a current of 1 μA is applied. An amplifier A ₂ forming a voltage detection circuit DT for detecting a potential difference V _L generated in the current detection resistor R is connected to both ends of the current detection resistor R, and a leak current I flowing from the output to the load R _L.
L (= V _L / R) is calculated. With such a configuration, a high voltage is applied from the high-voltage power supply PS ₁ to the load R _L , and the potential difference V _L generated across the current detection resistor R connected in series with the load R _L is detected by the amplifier A ₂ , and this detection output Calculate the current flowing from the load.

Incidentally, since the amplifier A ₂ handles at most several volts to several tens of volts as a detection voltage, a general IC operational amplifier is often used as described above. For example, the power source is ± 15V. .. In this embodiment, the current detection resistor R
Is connected to the return side of the load R _{L, not to} the hot line side, so that no high voltage is applied to the amplifier A ₂ ,
It is not necessary to float this from the ground line L. Therefore, as shown in FIG.
The case 15 of the power supply PS ₂ for ₂ can be directly screwed. When the power supply PS ₂ is ± 15V,
If the detection voltage is designed to exceed ± 10V, amplifier A
_{Although 2} will be saturated, not only the power supply case but also the power supply GND can be grounded especially when the detection voltage is within the range of ± 10V. Further, the printed circuit board 3 on which the amplifier A ₂ is mounted can also be directly attached to the chassis 1 without interposing an insulating mount. Moreover, the ± B supply line and the GND line 5 drawn from the power source PS ₂ of the amplifier A ₂ into amplifier A _2,
Since almost no voltage is applied when viewed from the chassis ground GND, an ordinary inexpensive electric wire having a low withstand voltage is sufficient. In addition, since the pressure is low, adsorption of dust is significantly reduced.

In particular, in recent years, as automobiles have become electronic and automatic, the opening and closing of windows (power windows) and the expansion and contraction of radio antennas, for example, have been automated, and along with this, electronic devices such as transistors and ICs that control them. High breakdown voltage is required for parts. For this reason, the high withstand voltage leak current measurement specifications required for semiconductor test equipment are becoming more and more stringent at present.In that sense, the current detection device of this embodiment is not limited to semiconductor test equipment. Although it is not intended to be applied, it has great significance especially when applied to a semiconductor test apparatus.

[0011]

According to the present invention, since the detection resistor is connected to the return side of the load, no insulation measure for the current detection circuit is required, the structure is simple, safe and inexpensive, and reliable. Can be increased.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a current detection device in a high voltage power supply according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an assembling state in a case of the current detection device according to the present embodiment.

FIG. 3 is a circuit configuration diagram of a current detection device in a high voltage power supply according to a conventional example.

FIG. 4 is an explanatory view showing an assembling state in a case of a current detection device according to a conventional example.

FIG. 5 is a configuration diagram of a current detection circuit common to the present invention and a conventional example.

[Explanation of symbols]

L ground line PS ₁ high voltage power supply R _L load R current detection resistor DT current detection circuit A ₂ amplifier

Claims (1)

[Claims] 1. A high-voltage power supply having a load and a ground line in common, wherein a high voltage is applied to the load from the high-voltage power supply to detect a potential difference across both ends of a current detection resistor connected in series with the load, and a detection circuit detects the potential difference. A current detecting device in a high-voltage power supply for determining a current flowing from a detection output to a load, wherein the current detecting resistor is provided between the load and a ground line.