JP2000180500A - Detector for power source output current - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apparently reduce a current-detecting resistor and to assure a high speed operation when a power is applied by providing two sets of resistor groups having equal resistance value ratios and an operational amplifier for supplying an output responsive to a voltage difference of an output side. SOLUTION: A current detector 4 has resistors 4r, 45, 43 and 42 groups connected in series, and an operational amplifier 41 for supplying an output responsive to a voltage difference between a connector of the resistors 44, 45 and a connector of the resistors 43, 43 to a connector of the resistors 45, 43. A resistance value ratio of the resistors 44, 45 and a resistance value ratio of the resistors 42, 43 are set to equal to each other. In the circuit 4, a voltage drop generated at the resistor 42 is compensated for a voltage drop of the resistor 44, and no voltage is generated between input terminals of the circuit 4. Positive and negative terminal voltages of the amplifier 41 become equal. As a result, a current flowing to a load 5 can be detected based on the voltage drop present at the resistors 44, 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply output current detecting device for detecting the magnitude of a current supplied from a power supply device.

[0002]

2. Description of the Related Art Conventionally, a power supply output current detecting device has been used to detect the magnitude of a current supplied from a power supply device and determine the quality of a device under test connected to the power supply device based on the detection result. Things. Power supply output current detectors generally consist of a large resistor inserted and connected between the power supply output amplifier and the load. By measuring the voltage drop of this resistor, the current supplied from the power supply output amplifier to the load is detected. ing.

[0003]

When such a power supply output current detecting device is used in a power supply device for inspecting the electrical characteristics of an IC device such as an IC test device, the rising speed at the time of applying power is very low. It becomes important. In other words, the rise at the time of power application is the speed determined by the current detecting resistor and the transient load fluctuation preventing capacitor connected to the load. In an IC test apparatus or the like, it is necessary to rapidly measure a small current consumption or the like of the IC device in a standby state. However, the capacitor cannot be made smaller than the minimum capacity for preventing the transient load fluctuation, and the resistance cannot be made smaller than the minimum resistance value for maintaining the detection accuracy. Therefore, the capacitor can be operated only at the speed specified by the minimum capacitance and the minimum resistance of the resistor. That is, the resistance and the capacitor are obstacles to the high-speed operation during the IC test.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a power supply output current detection device capable of ensuring a high-speed operation when power is applied by making the resistance for current detection apparently small. The purpose is to:

[0005]

According to a first aspect of the present invention, there is provided a power supply output current detecting device according to the present invention, wherein first to fourth resistors are connected in series from a power supply side to a load side in order. A resistor group configured such that a resistance value ratio between the first resistor and the second resistor and a resistance value ratio between the fourth resistor and the third resistor are equal to each other; An operational amplifier that supplies an output corresponding to a voltage difference between an input side of the resistor and an output side of the third resistor to an input side of the third resistor. A transient load fluctuation preventing capacitor is connected to the load side. Since the fourth resistor is inserted between the capacitor and the operational amplifier, it operates as a stabilizing resistor for reducing the influence of the capacitor. Since the fourth resistor is an apparent resistor, the first and second resistors constitute a circuit for compensating for this.

According to a second aspect of the present invention, there is provided a power supply output current detecting apparatus according to the first aspect of the present invention, wherein the power supply output current detecting apparatus includes an input side of the first resistor and the second output side. A bidirectional diode is inserted between the resistor 4 and the output side. This diode is a bypass diode of a capacitor for preventing a transient load fluctuation, performs high-speed charging or discharging, and realizes a high-speed rising.

According to a third aspect of the present invention, there is provided a power supply output current detecting apparatus according to the first aspect of the present invention, wherein the power supply output current detecting apparatus does not change the resistance value ratio. A resistance value changing means for changing the values of the third resistance and the fourth resistance is provided. The resistance value changing means changes the measurement range of the current supplied to the load by changing the overall resistance value of the third resistance and the fourth resistance.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of an embodiment according to a power supply output current detection device of the present invention. In this embodiment, a power supply output current detection device for an IC test device will be described. The set voltage supply means 1 is a power supply circuit 2
This sets the output voltage of 0, that is, the voltage applied to the load. The power supply circuit 20 includes a voltage error amplifier 2, an output amplifier 3, and a current detection circuit 4. The voltage error amplifier 2 detects a difference between the load terminal voltage (the voltage supplied to the measured IC 5 as a load) and the set voltage of the set voltage supply unit 1. The output amplifier 3 is a power amplifier that supplies power to a load (IC under test) 5 according to the voltage difference output of the voltage error amplifier 2. The voltage error amplifier 2 and the output amplifier 3 may be shared.

The current detecting circuit 4 detects a current flowing through a load, and includes an operational amplifier 41, resistors 42 to 47, diodes 48 and 49, and switches SW1 to
SW4. As the current detection circuit 4, besides the above-described resistance voltage drop type, a circuit in which the apparent resistance of an operational amplifier is reduced is known. When connected, it becomes unstable or requires a significantly lower speed configuration. Therefore, in this embodiment, the current detection circuit 4 is configured to operate stably with the high-speed configuration using the operational amplifier.

The current detection circuit 4 basically includes a group of resistors 44, 45, 43, and 42 connected in series from the output amplifier 3 side to the load 5 side, and a resistor 44 and a resistor 45.
And an operational amplifier 41 that supplies an output corresponding to the voltage difference between the connection between the resistor 43 and the resistor 42 to the connection between the resistor 45 and the resistor 43. The resistance value ratio between the resistors 44 and 45 and the resistance value ratio between the resistors 42 and 43 are set to be equal to each other. The diodes 48 and 49 bypass the charge current of the load capacitor 6 and can be charged with a large current, thereby realizing a fast rise.
This diode may be omitted, and that part may be an open circuit.

The resistances 46 and 47 have the same resistance ratio as the resistance 42 and the resistance 43, and have different overall resistances. That is, the resistors 46 and 47 are resistors for switching the current range supplied to the load 5. The switching of the resistance value is performed by the current range changeover switches SW1 to SW4. When the changeover switches SW1 and SW2 are on, the changeover switches SW3 and SW4 are off and the changeover switch S
When W3 and SW4 are on, changeover switches SW1,
It operates so that SW2 is turned off. For example, the resistor 42
And the resistor 43 is for a current range of 1 μA to 10 μA,
The resistor 46 and the resistor 47 have a current range of 10 μA to 100 μ
The respective resistance values are set so as to be used for A. The resistor 42 is a stabilizing resistor for reducing the effect of the capacitor 6 inserted between the capacitor 6 and the operational amplifier 41. Since the resistor 42 is an apparent resistor, a resistor 44 and a resistor 45 are provided as a circuit for compensating for this.

In the current detection circuit 4, the output current flows from the operational amplifier 41 through the resistors 42 and 43.
In a normal current detection circuit, the resistance 42 and the resistance 44 are 0 ohm, the part of the resistance 45 is not connected, and the voltage drop of the resistance 43 is output as it is. On the other hand, in the case of the current detection circuit 4 of this embodiment, the resistance 4
2 and the resistance value ratio of the resistance 43 and the resistance value ratio of the resistance 44 and the resistance 45 are selected to be equal to each other, so that the voltage drop generated in the resistance 42 is caused by the positive input terminal of the operational amplifier and the negative input Since the terminals have the same voltage, the voltage is compensated by the voltage drop of the resistor 44, and no voltage is generated between the input terminals of the current detection circuit 4. That is, the apparent detection resistance can be set to zero. On the other hand, the output voltage of the operational amplifier 41 is the output current × (the resistance 42 + the resistance 4
3), the positive terminal voltage of the operational amplifier 41 is the voltage divided by the resistors 44 and 45, and the negative terminal voltage of the operational amplifier 41 is the voltage divided by the resistors 42 and 43, and the respective voltage dividing ratios are equally selected. Therefore, both terminal voltages become equal. The current flowing through the load 5 can be detected based on the voltage drop appearing at the resistors 44 and 45.
Note that the detection may be performed based on a voltage drop appearing in the resistors 42 and 43. In this case, a detection amplifier having a large input impedance is required. Therefore, it is preferable to detect the current from both ends of the resistor 44 and the resistor 45.

In the above-described embodiment, the case where the current range is switched using the changeover switches SW1 to SW4 has been described. However, if the total resistance value of the resistors 42 and 43 is changed, It goes without saying that the resistance value may be changed by other methods.

[0014]

According to the present invention, there is an effect that the resistance for current detection can be made apparently small, and a high-speed operation when power is applied can be secured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment according to a power supply output current detection device of the present invention.

[Explanation of symbols]

1: set voltage, 20: power supply circuit, 2: voltage error amplifier,
3 output amplifier, 4 current detection circuit, 5 load (IC to be measured), 41 operational amplifier, 42 to 47 resistors, 48,
49… Diode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G003 AA07 AB02 AE01 AH04 2G032 AA00 AB00 AD01 AE14 AH00 AK01 AL18 2G035 AA13 AB02 AC01 AC02 AD04 AD11 AD20 AD45 5J091 AA01 CA65 FA12 HA19 HA25 HA29 HA38 KA00 KA01 KA01

Claims (3)

[Claims] A first resistor connected in series from a power supply side to a load side in order;
A resistor group configured such that the resistance value ratio of the second resistor to the second resistor, the resistance value ratio of the fourth resistor to the third resistor, and the resistance value ratio of the fourth resistor to the third resistor are equal to each other. A power supply output current detecting device, comprising: an operational amplifier for supplying an output corresponding to a voltage difference on an output side of a third resistor to an input side of the third resistor. 2. The power supply output current detecting device according to claim 1, wherein a bidirectional diode is inserted between an input side of said first resistor and an output side of said fourth resistor. 3. The apparatus according to claim 1, further comprising a resistance changing unit configured to change the values of the third resistance and the fourth resistance without changing the resistance value ratio. Power supply output current detector.