JP2002062333A - Measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a measuring apparatus with limited measuring errors, even if a switching power source is used. SOLUTION: Modification is accomplished for the measuring apparatus which applies an output to an object to be measured by a power of a switching power source, to perform at least one of the measurements of current and voltage. The apparatus has an A/D inverter, into which a voltage for the measurement of current or voltage is inputted to be converted to a digital data and a control part for stopping the switching power source, or keeping the switching frequency outside a measuring band pass in the conversion into the digital data with the A/D converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device used for, for example, an IC tester and operated by a switching power supply, and relates to a measuring device having a small measurement error.

[0002]

2. Description of the Related Art An IC tester uses a voltage / current measuring device to test DC characteristics of a device under test (DUT) such as an IC or an LSI. Such an apparatus is shown and described in FIG.

In FIG. 1, a measuring apparatus 100 includes an AC source 1, a switching power supply 2, a D / A converter 3, an amplifier 4,
Current / voltage converter 5, buffer 6, switch SW, A /
It comprises a D converter 7 and a controller 8. DUT2
00 has a load 9 and an impedance 10.

[0004] The AC source 1 outputs an AC voltage. The switching power supply 2 receives an AC voltage from the AC source 1, is connected to the ground and the ground, and outputs a DC voltage Va. D /
The A converter 3 receives the voltage set value and outputs an analog signal. The amplifier 4 operates with the DC voltage Va from the switching power supply 2 and the ground, inputs an analog signal from the D / A converter 3, and performs voltage output and current output.

[0005] The current / voltage converter 5 comprises a resistor R and a differential amplifier 51. The resistor R has one end connected to the output of the amplifier 4 and the other end connected to the input end of the load 9. The differential amplifier 51 is connected to both ends of the resistor R and outputs a voltage between both ends of the resistor R.

The buffer 6 has an input terminal connected to an input terminal of the load 9. The switch SW switches between the output of the differential amplifier 51 and the output of the buffer 6. The A / D converter 7 is
The output from the switch SW is converted into digital data.
The controller 8 outputs the set value to the D / A converter 3 and uses the digital data from the A / D converter 7 as a measured value.

The load 9 includes an impedance 91 and a capacitor C. The impedance 91 has one end having a current /
The output terminal of the voltage converter 5 and the input terminal of the buffer 6 are connected, and the other end is connected to the ground, and to the ground via the impedance 10. The capacitor C is connected to the impedance 91 in parallel. That is, one end is connected to one end of the impedance 91, and the other end is connected to the other end of the impedance 91.

The operation of such an apparatus will be described below.
First, a case where voltage output and current measurement are performed will be described. The switch SW is connected to the output of the current / voltage converter 5. Then, the controller 8 outputs the set value and outputs D /
A predetermined output voltage is generated by the A converter 3. The output voltage is amplified by the amplifier 4 and output to the load 9 via the resistor R. The A / D converter 7 includes a differential amplifier 51
Are output to the controller 8 as digital data (measured values).

Next, a case where current output and voltage measurement are performed will be described. The switch SW is connected to the output of the buffer 6. Then, the controller 8 outputs the set value,
A / A converter 3 generates a predetermined output voltage. With this output voltage, the amplifier 4 outputs a current and outputs the current to the load 9 via the resistor R. Then, the A / D converter 7 outputs the voltage at the input terminal of the load 9 to the controller 8 as digital data (measured value) via the buffer 6.

[0010]

In such a device,
The output noise generated by the switching power supply 2 is mixed into the voltage / current measurement system such as the output of the amplifier 4, the ground, and the resistor R, so that the measurement accuracy is deteriorated. In particular, there is a problem that a noise current flows through the capacitor C of the load 9 and a measurement error increases.

It is an object of the present invention to realize a measuring apparatus having a small measuring error even when a switching power supply is used.

[0012]

According to the present invention, there is provided a measuring apparatus for providing an output to an object to be measured with the power of a switching power supply and performing at least one of a current measurement and a voltage measurement. An A / D converter for inputting and converting to digital data, and a control unit for stopping the switching power supply or setting the switching frequency out of a measurement band when converting to digital data with the A / D converter. It is characterized by the following.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. Here, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, a switching power supply 21 is provided in a measuring apparatus 100, has an output capacitor (smoothing capacitor) not shown, receives an AC voltage from an AC source 1, connects to a ground and a ground, and Va is output to the amplifier 4.

The A / D converter 71 is provided in the measuring device 100 and converts an output from the switch SW into digital data according to a start signal and an end signal.

A controller (control unit) 81 is provided in the measuring apparatus 100, outputs a set value to the D / A converter 3, stops the switching power supply 21, and sends a start signal and an end signal to the A / D converter 71. And A / D
The digital data from the converter 71 is used as a measured value.

The operation of such a device is described below.
FIG. 2 is a timing chart showing the operation of the device shown in FIG. (A) is a control signal to a switching element (not shown) of the switching power supply 21, (b) is an on / off signal to the switching power supply 21, and (c) is an A / D converter 71.
(D) is an end signal of the A / D converter 71, and (e) is a DC voltage Va output from the switching power supply 21.

When performing voltage output and current measurement, the switch SW is connected to the output of the differential amplifier 51. Then, the controller 81 turns on the switching power supply 21 and outputs the set value. With the set value, the D / A converter 3 generates a predetermined output voltage. This output voltage is supplied to the amplifier 4
Is amplified and output to the load 9 via the resistor R. A / D
The converter 7 receives the output of the differential amplifier 51 via the switch SW.

At time t1, the controller 81 turns off the switching power supply 21. As a result, the switching power supply 21 stops the control signal to the switching element. As a result, the DC voltage Va of the switching power supply 21 becomes
The current flows from the output capacitor and starts to fall gradually.

At time t2, the controller 81
A start signal is supplied to the A / D converter 71 and the A / D converter 7
1 starts outputting the voltage from the differential amplifier 51 to the controller 81 as digital data.

At time t3, the controller 81 sets A
An end signal is given to the A / D converter 71 and the A / D converter 71
Ends the A / D conversion.

At time t4, the controller 81 turns on the switching power supply 21. Thereby, the switching power supply 21 starts the operation of the control signal to the switch element again. As a result, the DC voltage Va of the switching power supply 21 returns to the original voltage.

It is to be noted that the times t1 to t4 and the off time of the switching power supply 21 must be within the allowable range of the DC voltage Va.

When the current output and the voltage are measured, only the switch SW is connected to the output of the buffer 6 and the other operations are not changed, and the description is omitted.

As described above, since the controller 81 stops the switching power supply 21 at the time of A / D conversion of the A / D converter 71, the generation of noise in the switching power supply 21 can be prevented, and the measurement error can be reduced. . In particular, in the high-precision current measurement, the measured current is generally small and the output current of the switching power supply 2 is small. Therefore, the DC voltage Va can be maintained by the output capacitor of the switching power supply 2.

In addition, since there is no need to provide a component or a shield against output noise of the switching power supply 21, the cost can be reduced.

Next, another embodiment will be described with reference to FIG.
Here, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In the figure, a current / voltage converter 5 includes resistors R1 to R4, switches SW1 to SW3, and a differential amplifier 51.
Consists of One end of each of the resistors R1 to R4 is connected to the output of the amplifier 4. The switches SW1 to SW3 have one ends connected to the other ends of the resistors R1 to R3, respectively. The other end of the resistor R4 and the switches SW1 to SW3 are connected to the load 9. The differential amplifier 51 includes one ends of resistors R1 to R4 and switches SW1 to S4.
It is connected to W3 and the other end of the resistor R4, and outputs a voltage between both ends.

Such a device enables the current measurement in the low current range by switching the switches SW1 to SW3 when measuring the current. Other operations are the same as those described above, and the description is omitted.

Note that the present invention is not limited to this, and the controller 81 has a configuration in which the switching power supply 21 is turned on / off. However, any configuration may be used as long as noise caused by the switching power supply 21 can be prevented. That is, the controller 81 may be configured to increase or decrease the switching frequency of the switching power supply 21 to make it outside the measurement band.

[0031]

According to the present invention, the A / D converter has an A / D converter.
At the time of conversion, the control unit stops the switching power supply or sets the switching frequency out of the measurement band, so that noise generation of the switching power supply can be prevented, and the measurement error can be reduced.

Further, since there is no need to provide a component for preventing output noise of the switching power supply or a shield, the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the device shown in FIG.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional measuring device.

[Explanation of symbols]

 5 Current / Voltage Converter 6 Buffer 21 Switching Power Supply 71 A / D Converter 81 Controller 100 Measuring Device 200 DUT

Claims (3)

[Claims] 1. A measuring apparatus which supplies an output to an object to be measured by power of a switching power supply and performs at least one of a current measurement and a voltage measurement, wherein the voltage of the current measurement or the voltage measurement is input and converted into digital data. When converting to digital data with an A / D converter and this A / D converter,
A control unit for stopping the switching power supply or setting a switching frequency outside a measurement band. 2. A measuring apparatus for applying a voltage output to an object to be measured by the power of a switching power supply and performing current measurement, wherein the current value is provided on a signal path of the voltage output to be applied to the object to be measured. To a voltage, an A / D converter that receives the voltage from the current / voltage converter and converts it into digital data, and converts the data to digital data with the A / D converter. Sometimes
A control unit for stopping the switching power supply or setting a switching frequency outside a measurement band. 3. A measuring apparatus for applying a current output to a device under test by the power of a switching power supply and performing voltage measurement, comprising: a buffer for inputting an input voltage of the device under test; A / D converter for converting to data, and when converting to digital data with this A / D converter,
A control unit for stopping the switching power supply or setting a switching frequency outside a measurement band.