JPH11133068A - Voltage/current characteristic measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage/current characteristic measuring device that is stable against a large-capacity load, suppresses a spike and an overshoot when switching a range, and further can speedily change setting. SOLUTION: A voltage/current characteristic measuring device has an output current supply part with a current source 180, a range resistor, an output terminal 132 to a DUT 134, and an output control part for controlling current that flows to the output terminal 132, a current measuring part with a current source 180, a resistor 188 for IM where current that is proportional to that flowing to the DUT 134 flows, and a current measurement auxiliary resistor; and a voltage control part with a first DA converter 102, an integrator 104 with a clamping circuit for preventing the saturation of the first DA converter 102 and an amplifier 108, an output control part 152 in the above for controlling the output current of the output current supply part, and a voltage control unit with an output terminal and a feedback circuit for feeding back the voltage of the output terminal to the integrator 104 via a buffer amplifier and a feedback resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an apparatus for testing DC characteristics of semiconductors, and more particularly, to measuring current while applying a voltage to a device under test and measuring the voltage while applying a current to the device under test. The present invention relates to a voltage-current characteristic measuring device for measuring.

[0002]

2. Description of the Related Art A voltage-current characteristic measuring device tests DC characteristics of a wide range of devices under test (hereinafter abbreviated as DUT) such as relays, switches, resistors, capacitors, inductors, diodes, transistors, FETs, ICs, LSIs, and VLSIs. It is a device to do. This voltage-current characteristic measuring device basically applies a constant voltage to the DUT and measures the VF
An IM (V Force I Measurement) and an IFVM (I For
ce V Measurement), and a current limit (I limit) function that limits the current flowing to the DUT with VFIM and a voltage limit (V limit) function that limits the voltage applied to the DUT with IFVM. ing.

In order to realize the above-mentioned functions, the voltage / current measuring device is operated in a VF (V Force: constant voltage source) mode,
There are three modes: a positive IF (I Force: constant current source) mode and a negative IF mode, and the DUT is configured to always operate in any one of these modes.

[0004] In the present specification, for the sake of explanation, DU is used.
With respect to T, the voltage value set in the VF mode is called a control voltage value, and the current value set in the positive or negative IF mode is called a control current value.
Set the limit value to the limit current value, DUT in IF mode
Is referred to as a limited voltage value.

The structure and operation of a conventional voltage-current characteristic device are described in Japanese Patent Application Laid-Open No. 58-148507 and Japanese Patent Application Laid-Open No. 8-262.
No. 069, for example, has a configuration shown in FIG. That is, in the VF mode, D
A converter 11, voltage range resistor 12, error amplifier 13,
A constant voltage source loop (V loop) including the voltage / current converter 17, the integrator 41, the power amplifier 42, the current range resistor 43, the buffer amplifier 45, and the resistor 16 operates, and in the positive IF mode, the DA converter 21, inverting amplifier 22, resistor 23, error amplifier 24, voltage / current converter 28, integrator 41, current amplifier 42, current range resistor 43, CMRR
A circuit 52 (comprising the buffer amplifiers 48 and 50 and the differential amplifier 46) and a positive constant current source loop (Ip loop) composed of the resistor 27 operate, and in the negative IF mode,
DA converter 21, resistor 33, error amplifier 34, voltage / current converter 38, integrator 41, power amplifier 42, current range resistor 43, CMRR circuit 52 (constituted with buffer amplifiers 48 and 50 and differential amplifier 46) , A negative constant current source loop (In loop) composed of the resistor 37 operates.

The terminal 44 is an output terminal, reference numeral 56.
Is a DUT, and reference numerals 14 and 25 and 35 are clamping circuits for preventing the corresponding error amplifiers 13 and 23 and 33 from saturating.

As shown in FIG. 1, in the constant current source loop of the conventional voltage / current characteristic measuring device, the current flowing through the current range resistance circuit 43 at the stage prior to the output terminal is converted into a voltage, so that voltage measurement and The current range is being set.

However, in the conventional method, especially in the V loop, the phase of the feedback error amplifier 13 is shifted due to the relationship between the current range resistor 43 and the load connected to the output terminal 44. However, it was difficult to design the error amplifier 13 to ensure stability.

In particular, the error amplifier 13 must be designed in such a manner that the settling speed of the system is reduced in order to secure stability against a large capacity load. Conversely, there is a problem that the capacity load must be restricted in order to execute the setting and the measurement stably at high speed.

Further, the conventional method has a problem that the circuit becomes expensive. That is, in order to obtain a highly accurate current measurement, the current flowing through the DUT 56 must be accurately monitored. Therefore, a CMRR circuit 52 including a differential amplifier 46 and buffer amplifiers 48 and 50 for removing the common mode from the output voltage to the current range resistor 43 and extracting only the voltage applied to both ends is required. . As shown in FIG. 2, when the voltage at the output terminal 44 of the circuit shown in FIG. 1 is 20 V and the current flowing through the current range resistor 43 generates a common mode voltage of 0.1 V, an output of about 20 V 0.1V in voltage
A high-precision resistor that can detect the current value and obtain a current value is required for the current range resistor 43. That is, if a voltage of 0.1 V is obtained with a precision of 0.1% for current measurement, a CMRR characteristic of 0.0005% for 20 V is required, and an extremely expensive CMRR circuit is required.

Also, the problems of spikes and overshoot cannot be ignored. The voltage-current characteristic measuring device as shown in FIG. 1 includes a plurality of feedback circuits as described above to execute the VF mode and the positive or negative IF mode. Due to the finite frequency response of these feedback circuits,
If at least one parameter such as the input voltage, the feedback constant, or the switching of the feedback circuit that determines the state of the feedback circuit in the equilibrium state is changed, a spike or overshoot occurs in the output.

When a current / voltage is set and a range is switched, when the I limit is applied in the VF mode depending on the state of the DUT, or when a plurality of feedback circuits are switched in the IF mode due to the V limit, the clamped feedback operation is stopped. Since the state and the feedback control operation state in which the clamp is released are interchanged, particularly large spikes and overshoots occur, giving extra stress to the DUT, and having an adverse effect.

In order to suppress the above-mentioned spikes and overshoots, the following methods have been devised.

(A) A method of providing a filter at the output of the DA converter.

(A) The range change of the control voltage in the positive and negative IF modes is performed by switching the resistance (not shown) in the voltage range resistance circuit 12, and at this time, the DA converter is temporarily changed. In this method, the range resistor 11 is set to 0 V output, the range resistance is switched in that state, and then the DA converter is set to a desired value.

(C) When only the range of the limit voltage is changed in the positive and negative IF modes, when it is predicted that the absolute value of the voltage value temporarily becomes small, the V limit is applied, and a spike is generated. Voltage range Make-before-break switching of the resistance, temporarily connect the resistance in parallel, lower the resistance value than it was connected before, change the range of the limit voltage value, and set the previous limit voltage value How to do it again.

(D) When changing the current range resistance in the positive / negative IF mode, first change the setting so that the current voltage becomes the control voltage value, and maintain the voltage and current in the IF mode. Forcibly shift to the VF mode while keeping the voltage, then change the resistance of the current range resistor circuit and return to the IF mode.
F mode transition conversion method.

(E) In a positive / negative IF mode, when a setting change involving a change in current range resistance is performed, the voltage-current converters of the Ip loop and the In loop are brought into a function stop state, and the Ip loop and the In loop are temporarily stopped. A method of cutting the Ip · In loop, in which the feedback loops of the loops are cut, and then the current-related settings are changed, and after all the changes are completed, the feedback loops of the Ip loop and the In loop are restored.

(F) In the above method (e), Ip
A soft switch method in which when the function of the In-loop voltage / current converter is stopped, the FET switch for switching the current range resistance is driven by a ramp voltage waveform so that the change in the range resistance is slower than the frequency response of the V loop.

(G) During normal operation, the output voltage is stored in a V hold loop provided with a voltage hold circuit (V hold circuit), and the feedback of the V hold loop is performed only when the control voltage value or the control current value is changed. A V-hold loop adding method for forming a circuit and maintaining the output voltage at a value immediately before the change based on the storage voltage of the V-hold storage circuit.

However, the above countermeasures have the following problems.

(1) In the methods (a) to (g), 1
To change one setting, you have to perform several steps. Therefore, it takes time to change the setting.

(2) In the methods (a) and (f), D
Since the setting change of the low-pass filter and the soft switch of the A-converter is gradually performed, it takes time to change the setting.

(3) In the methods (a) to (e), the current voltage value is monitored, it is predicted whether or not the V limit will be applied after the setting is changed, and an appropriate method is selected from the plurality of changing methods described above. Since the order of operations must be switched, the control becomes complicated, and the arithmetic and control unit becomes complicated and expensive accordingly.

[0025]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and does not include a current range resistor in a V loop due to a circuit configuration mainly using current control. The object of the present invention is to provide a voltage-current characteristic measuring device which is stable even for a large capacity load, suppresses spikes and overshoots at the time of range switching, and can change settings at high speed by adopting a circuit system. I do.

Another object of the present invention is to provide a voltage-current characteristic measuring device having a low output impedance.

Another object of the present invention is to provide a voltage-current characteristic measuring apparatus which can easily design an output impedance to be resistive in a low-frequency region and ensure stability against a large-capacity load.

Another object of the present invention is to provide an expensive and highly accurate CM
An object of the present invention is to provide a voltage-current characteristic measuring device which does not require an RR circuit.

Another object of the present invention is to simplify the complicated control at the time of setting change of the prior art, and realize a part which has been controlled by a large-scale configuration including a CPU and firmware by hardware logic. It is an object of the present invention to provide a voltage-current characteristic measuring device with reduced complexity as much as possible.

Another object of the present invention is to provide a voltage-current characteristic measuring apparatus characterized in that the configuration and control of the range resistance switching circuit are simple and the cost can be reduced.

Another object of the present invention is to provide a voltage-current characteristic device which performs a range switching sequence by switching a range resistance and controlling a VF and IF setting DA converter to prevent overshoot and spikes. is there.

[0032]

According to the present invention, there is provided an output current supply unit having a current source, a current range resistor, an output terminal to a DUT, and an output control unit for controlling a current flowing through the output terminal, and another current source. And a current measuring unit provided with an IM resistor and a current measuring auxiliary resistor through which a current proportional to the current flowing through the DUT flows, and an integrator with a clamp circuit for preventing saturation of the first DA converter and the amplifier and an output current supply unit. A current source for the output current supply unit, comprising: the output control unit for controlling the output current; and a voltage control unit including a feedback circuit for feeding back the output terminal and the voltage of the output terminal to an integrator via a buffer amplifier and a feedback resistor. The current flowing from the current source of the current measuring unit is proportionally proportional to the output voltage of the second DA converter and the voltage of the range resistor of the output current supply unit by the control unit. By being controlled to be solves the above problems.

In the present invention, preferably, the current range resistance of the output current supply section, the current source and the output control section, the current measurement section of the current measurement section and the auxiliary resistance, and the control section for controlling these current sources are positive. And two for each negative voltage.

In the present invention, preferably, the integrator includes a voltage range resistor.

In the VF (constant voltage source) mode, first, the second DA converter is set so as to output a current having an I-limited current value to the current source of the current supply unit. Next, the output control unit of the output current supply unit is controlled by the output voltage of the first DA converter via the integrator, and the flow of the current flowing from the current source of the current supply unit is controlled. The current flowing from the output control unit flows to the DUT, and a voltage is generated in the DUT. D
The UT voltage is fed back to the integrator by a feedback circuit via a buffer amplifier and a feedback resistor, and the output control unit controls the current output from the output control unit according to the output of the integrator so that the output voltage becomes a desired value. I do.

At this time, by the operation of the control section, the current proportional to the current flowing from the output current supply section is controlled so as to flow also from the current source of the current measurement section. Therefore, the DUT
Can be obtained by measuring the voltage across the IM resistor.

When the I limit is applied, the following operation is performed. In other words, in this case, the current flowing through the DUT is going to exceed the limit current value set by the I limit due to the relationship between the voltage set in the VF mode and the impedance of the DUT. At this time, if the current flowing through the DUT does not reach the limit current value, the voltage of the DUT becomes VF.
Since the setting in the mode is not reached, feedback is applied to the integrator so as to make the current flow more easily in the output control unit. However, the maximum value of the current flowing through the DUT is set to the limited current value by the current source of the output current supply unit.
The current flowing through the UT does not exceed the current limit value. As a result, further feedback is applied to the integrator so as to make the current of the output control unit flow more easily. The ON state (that is, the conductive state) where the current flows most easily is obtained. But the feedback works further, and the amplifier in the integrator goes to saturation,
When the voltage at the input and output of the amplifier reaches the clamp voltage of the clamp circuit, current starts to flow through the clamp circuit and becomes a clamp state, and the amplifier remains in an unbalanced state with an I limit applied to the DUT.

In the IF (constant current source) mode, first, the first
And the second DA converter is set so that a desired current flows to the current source of the output current supply unit. When the set current flows through the DUT and the voltage generated by the DUT is lower than the limit voltage value, feedback is applied as described above, and the amplifier in the integrator goes to saturation and enters a clamp state. In this state, the output control unit is turned on, and the current flowing through the DUT is the current set as the current source of the output current supply unit. Whether the output current of the current source is equal to the set value is determined by controlling the current source by applying feedback of the voltage of the range resistor of the output current supply unit to the control unit.

At this time, the voltage applied to the DUT can be obtained by measuring the output voltage of the buffer amplifier connected to the output terminal.

When the V limit is applied, the following operation is performed. When the voltage generated by the DUT becomes higher than the limit voltage value, a current flows into the amplifier in the integrator via the buffer amplifier and the feedback resistor to escape the clamp state, form a voltage feedback loop, and connect the output control unit to the current source. The current is controlled so that it does not flow easily, and the balance is restored.

In the present invention, a photocoupler is preferably used for the control unit.

In the present invention, the range switching sequence can be easily realized by devising the setting order of the voltage and current range resistors and the first and second DA converters.

In another embodiment of the present invention, the control unit includes a voltage / current converter for converting the output of the second DA converter into a current, and a reference current generator having first and second reference current resistors. And the current flowing from the current source of the output current supply unit and the current flowing from the current source of the current measurement unit are proportional to the current flowing through the predetermined point of the reference current generation unit and the current flowing through the predetermined point of the output current supply unit. Mirror control unit for performing the control as described above.

In still another embodiment, a current flowing to an output terminal is controlled by using a resistor and an FET instead of a photocoupler in the output control unit.

[0045]

FIG. 3 shows a basic block diagram of a voltage-current characteristic measuring apparatus according to the present invention.

The output of the VF DAC (DA converter) 102 is connected to the negative input terminal of the amplifier 108 via the VF range resistor 106, and the positive input terminal of the amplifier 108 is grounded. Negative input of amplifier 108 and amplifier 108
Is connected to a capacitor 110, and a clamp circuit 112 in which zener diodes 114 and 116 having opposite polarities are connected in series is connected in parallel to both ends of the capacitor 110. The integrator 104 is constituted by the VF range resistor 106, the amplifier 108, and the capacitor 110. The output of the amplifier 108 is connected to the light emitting section 120 of two photocouplers 138 and 139 connected in series.
And 122 (that is, a connection point between the cathode of the light emitting unit 120 of the photocoupler and the anode of the light emitting unit 122 of the photocoupler), and the light emitting unit 1 of the photocoupler.
An anode 20 is connected to a power supply Vaa, and a cathode of the light emitting unit 122 of the photocoupler is connected to a power supply Vbb. The light receiving sections 124 and 12 of the respective photocouplers
6 is connected in series, an output terminal 132 is connected to an intermediate point between the light receiving portions of the two photocouplers (that is, a connection point between the anode of the light receiving portion 124 of the photocoupler and the cathode of the light receiving portion 126 of the photocoupler), and DUT on terminal 132
134 is connected. Output terminal 132 is connected to the negative input of amplifier 108 via buffer 128 and feedback resistor 118. The output of buffer 128 is V
An M (V Measure: voltage measurement) terminal is connected.

A power supply Vcc is connected to the cathode of the light receiving section 124 of the photocoupler via a current source 154 and an IF range resistor 156. The current source 154 is controlled by the Ip control unit 152, and the Ip control unit 152
150 from the output terminal and the IF range resistor 15
6 is connected as an input to a terminal that is not connected to the power supply Vcc.

A power supply Vee is connected to the anode of the light receiving section 126 of the photocoupler via a current source 164 and an IF range resistor 166. The current source 164 is controlled by the In control unit 162, and the In control unit 162
A signal from the output terminal of C150 via the inverter 160;
The terminal of the IF range resistor 166 that is not connected to the power supply Vee is connected as an input.

Preferably, the power supplies Vaa and Vbb of the light emitting section of the photocoupler are provided with the power supplies Vcc and Ve connected to the light receiving section of the photocoupler in order to prevent noise from the power supply.
e and another power source are used.

A circuit for IM (I Measure: current measurement) is configured as follows. Power supply Vcc and power supply V
ee, the resistor 182, the current source 180, and the current source 18
4 and a resistor 186 are provided. An IM terminal 190 is connected to an intermediate point between the current sources 180 and 184.
An IM resistor 188 is connected to the IM terminal, and the other end of the IM resistor 188 is grounded. The current source 180 is controlled by the Ip control unit 152, and the current source 184 is controlled by the In control unit 1
62.

The Ip control unit 152 controls the current source 154 and the current source 180 such that a current proportional to the voltage set by the IF DAC 150 and the current flowing through the IF range resistor 156 flows. That is, the Ip control unit 15
2 is a voltage equal to the voltage set by the IF DAC 150 and the terminal to which the power supply Vcc of the IF range resistor 156 is not connected.
The current source 154 and the current source 180 are controlled so as to be supplied to the terminal not connected to the power supply Vcc of the resistor 182 and the terminal not connected to the power supply Vcc.

The In control section 162 controls the current source 164 and the current source 184 to output a current proportional to the voltage set by the IF DAC 150 and passing through the inverter 160 and the current flowing through the IF range resistor 166. To control. That is, the In control unit 162 determines that the voltage of the voltage set by the IF DAC 150 via the inverter 160 and the terminal of the IF range resistor 166 to which the power supply Vee is not connected are connected to the IF range resistor 166. The current source 16 is supplied to the terminal not connected to the power supply Vee and the terminal of the resistor 186 not connected to the power supply Vee.
4 and the current source 184 are controlled.

In the VF mode, first, the IF DAC 150 is set so that the current source 154 or 164 outputs a current having a limited current value of the I limit. Next, D for VF
The AC 102 is set and output to the integrator 104 including the VF range resistor 106 selected to a desired value.

If the output of the VF DAC 102 is a positive voltage, the output of the integrator 104 becomes a negative voltage, the photocoupler 120 is active, and the light emitting unit 122 of the photocoupler is off. On the light receiving side, the light receiving section 124 of the photo coupler is activated and the light receiving section 126 of the photo coupler is turned off on the light receiving side. That is, the light receiving section 124 of the photocoupler operates so that a current proportional to the voltage applied to the light emitting section 120 flows. As a result, the current i ₁ flows through the IF range resistor 156,
No current flows through the range resistor 166. The current output from the light receiving unit 124 of the photocoupler flows to the DUT 134 via the output terminal 132, and a voltage is generated in the DUT.
At this time, if the output of the VF DAC 102 is V _fD , the resistance of the VF range resistor 106 is R ₁₀₆ , and the resistance of the feedback resistor 118 is R ₁₁₈ ,

V _fD · R ₁₁₈ / R ₁₀₆

Is the voltage applied to the output terminal 132, that is, the DUT 134.

The voltage at the output terminal 132 is fed back to the integrator 104 via the buffer amplifier 128 and the feedback resistor 118, and reaches an equilibrium state when the output reaches a desired voltage.

Conversely, if the output of the VF DAC 102 is a negative voltage, the output of the integrator 104 will be a positive voltage, the light emitting unit 122 of the photocoupler will be active, and the light emitting unit 120 of the photocoupler will be off. On the light receiving side, the light receiving unit 126 of the photo coupler is activated and the light receiving unit 124 of the photo coupler is turned off on the light receiving side. As a result, the current i ₂ flows through the IF range resistor 166, the current stops flowing through the IF range resistor 156, a predetermined voltage is applied to the output terminal 132, and the same feedback is applied.

The current i _DUT flowing through the _DUT 134 is measured as follows. It is assumed that the output of the VF DAC 102 is a positive voltage. The current source 180 is controlled by the Ip control unit 152.
Is controlled so that a current i _M1 proportional to the current flowing through the current source 154 flows.
And controls the current source 184 to flow a current △ i _M2 proportional to the current △ i ₂ flowing in the current i _M flowing through the IM resistor 188,

I _M = i _M1 − △ i _M2 = A · (i ₁ − △ i ₂ ) = A · i _DUT (Equation 1) where A = R ₁₅₆ / R ₁₈₂

Is obtained. Therefore, by measuring the voltage drop at the IM resistor 188 by connecting an AD converter (not shown) or the like to the IM terminal 190, the current flowing through the DUT can be measured.

In this method, the light receiving section 12 of the photocoupler
4 or 126, the bias current increases from Vcc to Vee and the IF range resistor 156 → current source 154 → photocoupler light receiving section 124 →
A current flows through a path of the light receiving portion 126 of the photocoupler → the current source 164 → the IF range resistor 166. Here, since the bias current flows through the resistors 156 and 166, the bias current may seem to cause an error. However, as can be seen from the above equation 1, the IM resistor 188 is canceled by each other. Does not flow, so it does not become an error factor.

When the I limit is applied, the following operation is performed. That is, in this case, the relationship between the voltage set in the VF mode and the impedance of the DUT 134 indicates that the DUT
This is a case where the current flowing through the switch 134 tries to exceed the limit current value set by the I limit. At this time, DUT
In the state where the current flowing through the current 134 does not reach the limit current value,
Since the voltage of the DUT 134 does not reach the setting in the VF mode, feedback acts on the amplifier 108 to make it easier to flow current in the light receiving portion of the photocoupler. However, the maximum value of the current flowing through the DUT 134 is
, The current flowing through the DUT 134 does not exceed the limit current value. As a result, feedback is further applied to the amplifier 108 so as to make the current in the light receiving portion of the photocoupler easier to flow.
Since no more current flows through T134, the light receiving portion of the photocoupler will be in an on state in which the current will flow most easily. However, the feedback works further and the amplifier 10
8 starts to saturate, but when the input / output voltage of the amplifier 108 reaches the clamp voltage of the clamp circuit 112, current starts to flow through the clamp circuit 112 to be in a clamp state, and the amplifier 108 consequently has an I limit on the DUT. Remains unbalanced.

At this time, by setting the response time of the Ip control unit 152 for controlling the current source 154 to be faster than the change in the voltage by the amplifier 108, the current from the current source 154 before the amplifier 108 reaches equilibrium. Since the current has an I limit, the I limit can be applied without giving a spike. The amplifier 108 remains unbalanced due to the application of the I limit.
As a result, it stays in the clamped state without actually saturating,
It can respond quickly to the next fluctuation.

In the clamp state, the light emitting section 120 of the photocoupler and the light receiving section 124 of the photocoupler are turned on, and the current supplied to the DUT 134 only by the current source 154 is limited.

The case where the above-mentioned I limit is applied will be described in the following.
The same applies to 26.

Next, the operation in the IF mode will be described.

For the sake of simplicity, a case where the control current i _S is set for the DUT in the positive IF mode will be described. First, the limit voltage value V _S of the V limit is set in the VF DAC. Here, it is assumed that the limit voltage value v _S is a positive value. The light receiving section 124 of the photocoupler is activated, and the light receiving section 126 of the photocoupler is turned off.
At this time, since the current flowing from the current source 154 has not been set yet, no current flows through the DUT 132. Since the voltage of the DUT is low, the buffer 108
Although feedback is applied via 8, but no current flows through the DUT 134, the amplifier 108 is clamped toward saturation. In this state, the light receiving unit 124 of the photocoupler is turned on, and the current flowing through the DUT 134 can be controlled only by the output current from the current source 154.

Next, the IF range resistor 156 is switched to a predetermined value, the IF DAC is set, and the Ip control unit 152 is set.
Causes the current source 154 to output the current i _S. Since the light receiving unit 124 of the photocoupler is on and the light receiving unit 126 of the photocoupler is off, the control current i _s is
4 to the output terminal 1 via the light receiving section 124 of the photocoupler.
32, and flows to the DUT 143. Ip control unit 1
52 monitors the voltage of the terminal of the IF range resistor 156 that is not connected to the power supply Vcc, and controls the current source 154 so that a desired current flows through the IF range resistor 156.

The voltage V _DUT of the _DUT is
An ADC (not shown) or the like is connected to the VM terminal 130 connected to the output of No. 8 for measurement.

The voltage v _DUT applied to the _DUT is equal to the VF DAC.
In the case of trying to exceed the limit voltage value V _S of the V limit set in the above, a current flows into the negative input of the amplifier 108 from the feedback resistor 118, the amplifier 108 exits the clamp state, and a voltage feedback loop is formed again. Then, the photocoupler 124 is changed from the ON state to the active state to limit the current from the current source 154, a feedback operation is performed on the amplifier 108, and again when the v _DUT reaches v _S · R ₁₁₈ / R _106. A state of equilibrium is reached.

The current flowing through the DUT is controlled by the Ip control unit 152 so that a current proportional to the current source 154 is supplied to the current source 180.
It can also be measured by connecting a DC (not shown) or the like.

The above description is the same for the negative IF mode.

The photocoupler has a very small floating capacitance between input and output. Therefore, in this embodiment, by using the photocoupler for the block 136, the leakage current flowing from the light emitting units 120 and 122 of the photocoupler to the output terminal 132 through the stray capacitance can be extremely reduced.

Preferably, photocouplers 138 and 139
Is preferably a photocoupler element having high linearity.

Next, a method for preventing overshoot and spikes in the present invention will be described.

In the range switching sequence, the VF / IF range resistance and the VF / IF DAC
The overwriting and spikes are prevented simply by altering the order of rewriting. Here, the VF range resistor 106 and the IF range resistors 156 and 166 of FIG.
Has a configuration like a circuit 600 shown in FIG. That is, the circuit 600 includes a plurality of relays 602, 606, and a plurality of range resistors 604, 614, 624, 634, and 644 so that the plurality of relays 602, 606,
612, 616, 622, 626, 632, 636, 6
42 and 646 are provided, and a range resistor corresponding to a desired range can be connected.

In the VF mode, when the current range of the I limit is increased without changing the setting of the limiting current value, the procedure of FIG. 4 is performed as follows. 1. 1. A range resistor of the next range is connected in parallel with the IF range resistor 156 or 166 (404). 2. disconnect the previous range resistor (406); The setting of the IF DAC 150 is changed (408).

In the VF mode, when the current range of the I limit is lowered without changing the setting of the limiting current value, the procedure of FIG. 5 is performed as follows. 1. 1. Change the setting of the IF DAC 150 (414); 2. Connect the range resistors of the next range in parallel with the IF range resistors 156 or 166 (416); The previous range resistor is disconnected (418).

When the current range of the control current is increased in the IF mode, the procedure of FIG. 5 is performed as follows. 1. 1. Change the setting of the IF DAC 150 (414); 2. Connect the range resistors of the next range in parallel with the IF range resistors 156 or 166 (416); The previous range resistor is disconnected (418).

When the current range of the control current is lowered in the IF mode, the procedure of FIG. 4 is performed as follows. 1. 1. A range resistor of the next range is connected in parallel with the IF range resistor 156 or 166 (404). 2. disconnect the previous range resistor (406); The setting of the IF DAC is changed (408).

In order to increase the voltage range of the control voltage in the VF mode, the procedure shown in FIG. 6 is performed as follows. 1. 1. Change the setting of the VF DAC 102 (424); 2. Connect the range resistors of the next range in parallel with the VF range resistor 106 (426); The previous range resistor is disconnected (428).

To lower the voltage range of the control voltage in the VF mode, the procedure of FIG. 7 is performed as follows. 1. 1. The next range resistor is connected in parallel with the VF range resistor 106 (434). 2. disconnect the previous range resistor (436); The setting of the VF DAC 102 is changed (438).

To increase the voltage range of the V limit without changing the setting of the limit voltage in the IF mode, the procedure of FIG. 7 is performed as follows. 1. 1. The next range resistor is connected in parallel with the VF range resistor 106 (434). 2. disconnect the previous range resistor (436); The setting of the VF DAC 102 is changed (438).

To lower the voltage range of the V limit without changing the setting of the limit voltage in the IF mode, the procedure of FIG. 6 is performed as follows. 1. 1. Change the setting of the VF DAC 102 (424); 2. Connect the range resistors of the next range in parallel with the VF range resistor 106 (426); The previous range resistor is disconnected (428).

That is, the spike is prevented from being applied to the V limit and the I limit when the VF / IF range is changed, the I limit / V limit range is changed, and the set values of the control current / voltage and the limit current / voltage are changed. Can be suppressed.

If the current limit does not change before and after the range is switched in the VF mode, the above sequence
By setting the current source 154 or 164 always to be equal to or more than the current limit value, the I limit does not need to be applied, and the V loop is always in an unbalanced state in which voltage feedback is applied. No need to appear in the output.

Also, in the case of the IF mode, if the limit voltage value does not change before and after the range switching, similarly, the output of the VF DAC is always set to a voltage equal to or higher than the voltage limit value so that the V limit is set. No need to worry, Ip or I
The n loop is maintained, and no spike occurs in the output.

Regarding the overshoot, when the current value and the voltage value change before and after the switching of the VF and IF range resistors, the VF and IF range resistors and the VF and IF DACs are set within the V loop band. By changing the setting of, overshoot does not occur. That is,
Range resistance for VF and IF and D for VF and IF
Overshooting can be suppressed by making the speed of the change in the AC setting slower than the speed at which the feedback of the V loop is applied.

FIG. 8 is a block diagram showing an embodiment of a concept lower than the block diagram of FIG. In FIG. 8, FIG.
The same reference numerals are used for the same elements as. FIG.
The Ip control unit 152 converts the voltage from the power supply Vcc to the resistor 202 and the voltage-to-current converter (VIC).
The Ip current mirror control unit 208 and the reference current generation unit grounded via the resistor 204 and the resistor 206 and the In control unit 162
2 and voltage-current converter (VIC) 214 and resistor 2
16 and an In current mirror controller 218 grounded via a reference current generator 16.

The output of the IF DAC 150 is connected to the VIC 204, and the output of the IF DAC 150 is connected to the VIC 214 via the inverter 160.

The Ip current mirror control unit 208 is connected to a terminal of the resistor 202 that is not connected to the power supply Vcc, and is connected to a terminal of the resistor 156 that is not connected to the power supply Vcc. The Ip current mirror control unit 208 causes the currents output from the current sources 154 and 180 to be proportional to the current flowing through the resistor 202 and the current flowing through the resistor 156. , Current sources 154 and 180
Control.

The In current mirror control unit 218 has a resistor 2
12 are connected to terminals on the side not connected to the power supply Vee, and are connected to terminals of the resistor 166 on the side not connected to the power supply Vee. The In current mirror control unit 218 determines whether the current output from the current source 164 and the current output from the current source 184 are equal to the current flowing through the resistor 212 and the resistor 166.
Current sources 164 and 184 to be proportional to the current flowing through
Control.

The operation of the reference current generating circuit and the Ip and In current mirror control units will be described in more detail. A description will be given taking a positive voltage in the VF mode as an example.

The resistance value of the resistor 202 is R ₂₀₂ ,
When the current flowing through the DUT is i _S1 and the resistance value of the resistor 156 is R ₁₅₆ , the output voltage of the DUT changes, and the current i _DUT flowing through the _DUT 134 tends to be larger than the limiting current i _S1 · R ₂₀₂ / R ₁₅₆ . At the time, the Ip current mirror control unit 208
Controls the current flowing through the resistor 156 to be a current proportional to the current i _S1 .

I _S1 · R ₂₀₂ ≧ i _DUT · R ₁₅₆

And the relationship is established.

That is, i _DUT ≦ i _S1 · R ₂₀₂ / R ₁₅₆

This is because if i _DUT is going to be larger than i _S1 · R ₂₀₂ / R ₁₅₆ , the Ip current mirror controller 2
08 works, and the current is limited so as not to flow over i _S1 · R ₂₀₂ / R ₁₅₆ or more.

Next, the IF mode will be described. For the sake of convenience, taking the case where the current flowing through the resistor 202 in the positive IF mode is set as i _S2 as an example, the operation of the Ip current mirror control unit 208

I _S2 · R ₂₀₂ = R ₁₅₆ · i _DUT i _DUT = i _S2 · R ₂₀₂ / R ₁₅₆

In this case, the amplifier 108 is a DAC for VF.
Although the output voltage is set by 102, the output voltage is set at a positive clamp voltage, so that the light emitting unit 120 of the photocoupler and the light receiving unit 124 of the photocoupler are in the ON state, the light emitting unit 122 of the photocoupler, and the light receiving unit 126 of the photocoupler.
Is off.

Therefore, the i _DUT set to a current proportional to the current i _S2 flowing through the resistor 202 is directly used as the light emitting unit 120 of the photocoupler and the light receiving unit 124 of the photocoupler.
Is output to the output terminal 132 through the DUT 134 and flows to the DUT 134.

The operation of the other parts of the block diagram of FIG.
The operation is the same as that of the corresponding part.

FIG. 9 is a block diagram showing one embodiment of the concept lower than the block diagram of FIG. In FIG. 9, FIG.
The same reference numerals are used for the same elements as. FIG.
204, VIC 214, Ip current mirror control unit 208, current source 154, current source 180, and In
Current mirror controller 218, current source 164, and current source 1
84 is more specific in FIG. Where FE
T304 and 344 and 350 are P channel FE
T and FETs 334 and 314 and 320 are N
It is a channel FET.

The positive input of the amplifier 302 is the DAC 1 for IF.
50, the negative input of amplifier 302 is connected to the non-grounded terminal of resistor 206, and amplifier 3
02 is connected to the gate of FET 304,
The drain of the resistor 304 is connected to the terminal of the resistor 202 not connected to the power supply Vcc, and the source of the FET 304 is connected to the non-grounded terminal of the resistor 206 and the amplifier 302.
Connected to the negative input of With this configuration, the IF D
The current is supplied to the resistor 2 so that the output voltage of the AC 150 becomes equal to the voltage of the source of the FET 304 and the midpoint of the resistor 206.
The current flows in a path of 02 → FET 304 → resistance 206.

The positive input of the amplifier 332 is the DAC 1 for IF.
The output of 50 is connected via inverter 160, the negative input of amplifier 332 is connected to the non-grounded terminal of resistor 216, the output of amplifier 332 is connected to the gate of FET 334, and the drain of FET 334 is Resistance 212
Connected to a terminal that is not connected to the power supply Vee,
The source of FET 334 is connected to the non-grounded terminal of resistor 216 and to the negative input of amplifier 332. With this configuration, the IF DAC inverted by the inverter 160
150, the source of the FET 334 and the resistor 21
The current flows through the path of the resistor 216 → the FET 334 → the resistor 212 so that the voltages at the middle points of the six are equal.

The positive input of the amplifier 306 is connected to the resistor 202 and the FE
The output of the amplifier 306 and the negative input of the amplifier 306 are connected via a capacitor 308, and the output of the amplifier 306 is also connected to the gate of the FET 314. The source of the FET 314 is a resistor 1
The FET 314 is connected to the power supply Vcc via 56, and the drain of the FET 314 is connected to the cathode of the light receiving section 124 of the photocoupler. The source of the FET 314 is a buffer amplifier 312
And the resistor 310 are connected to the negative input of the amplifier 306. With this configuration, the voltage of the terminal of the resistor 202 not connected to the power supply Vcc and the voltage of the
Resistor 156 → FET314 → Photocoupler 12 so that the voltages of the terminals not connected to cc become equal.
The current flows through the path of No. 4.

The positive input of the amplifier 336 is connected to the terminal of the resistor 212 that is not connected to the power supply Vee, and the output of the amplifier 336 and the negative input of the amplifier 336 are connected to the capacitor 33.
8 and the output of amplifier 336 is connected to FET 34
4 is also connected to the gate. The source of the FET 344 is connected to the power supply Vee via the resistor 166,
The drain of 44 is connected to the anode of the light receiving section 126 of the photocoupler. The source of the FET 344 is connected to the negative input of the amplifier 336 via the buffer amplifier 342 and the resistor 340. With this configuration, the power supply V
The voltage of the terminal not connected to ee and the resistance 166
In order to make the voltages of the terminals not connected to the power supply Vee of the photocoupler equal, the light receiving portion 126 of the photocoupler → the FET344 → the resistor 16
Current flows through the path of No. 6.

The output of the buffer amplifier 312 is
6 and the output of amplifier 316 is connected via capacitor 318 to the negative input of amplifier 316. The output of the amplifier 316 is connected to the gate of the FET 320, and the source of the FET 320 is connected to the power supply Vcc of the resistor 182.
Connected to the side not connected to The side of the resistor 182 that is not connected to the power supply Vcc is also connected to the negative input of the amplifier 316. The drain of the FET 320 is connected to the IM resistor 188 and the IM terminal 190. With this configuration, the voltage at the terminal of the resistor 156 to which the power supply Vcc is not connected is equal to the voltage at the terminal of the resistor 182 to which the power supply Vcc is not connected. The current flows through the path.

The output of the buffer amplifier 342 is
6 and the output of amplifier 346 is connected via capacitor 348 to the negative input of amplifier 346. The output of amplifier 346 is also connected to the gate of FET 350, the source of which is connected to the power supply Ve of resistor 186.
Connected to the side not connected to e. The side of the resistor 186 that is not connected to the power supply Vee is also connected to the negative input of the amplifier 346. The drain of the FET 350 is connected to the IM terminal 190 and the IM resistor 188. With this configuration, the voltage at the terminal of the resistor 166 to which the power supply Vee is not connected is equal to the voltage at the terminal of the resistor 186 to which the power supply Vee is not connected. The current flows through the path.

The operation of the other parts of the block diagram of FIG.
The operation is the same as that of the corresponding part.

Next, another embodiment of the voltage / current characteristic measuring apparatus according to the present invention will be described.

As can be easily understood by those skilled in the art, the light receiving section 1 of the photocoupler constituted by the light emitting sections 120 and 122 of the photocoupler and the photodiode in the present invention.
24 and 126 may use other types of photocoupler elements.

In FIG. 9, the Ip and In current mirror control units are realized by using amplifiers and FETs. However, as can be easily understood by those skilled in the art, these current mirror control units include other transistors such as transistors. It can also be realized by using an element.

Further, in an application field where the leakage current to the output terminal does not matter, the block 136 using the photocoupler shown in FIGS. 3, 8 and 9 is replaced with the resistor 5 shown in FIG.
Block 136 'using 02 and 504 and FETs 506 and 508 can also be used. Where F
ET506 is an N-channel FET, and FET508 is a P-channel FET.

Block 136 'in FIG. 10 is connected to each embodiment of the present invention as follows. The output of the amplifier 108 of FIGS. 3, 8 and 9 is
The output of the amplifier 108 is connected to the gate of the FET 508 via the resistor 504 while being connected to the gate of 506. The drain of the FET 506 is connected to the current source 154 in FIGS. 3 and 8 or the drain of the FET 314 in FIG.
8 and the output terminal 132, and the drain of the FET 508 is connected to the current source 164 in FIGS. 3 and 8 or the drain of the FET 344 in FIG. In this case, if the output of the amplifier 108 is a positive voltage, the FET 506 becomes active and the FET 5
08 turns off. If the output of the amplifier 108 is a negative voltage, the FET 508 becomes active and the FET 506
Turns off.

FIGS. 3 and 8 using the block of FIG.
The operation of the other parts of the block of FIG.
The operation is the same as that of the block diagrams of FIGS.

While the present invention has been described with reference to preferred embodiments, these are only examples, and those skilled in the art will recognize the embodiments described herein without departing from the spirit and scope of the invention. It will be readily understood that other embodiments can be substituted.

[0120]

As described above, when the present invention is used, spikes and overshoots can be suppressed with a simple circuit configuration and stable even with a large capacity load. A voltage-current characteristic measuring device can be provided.

It is possible to provide a voltage-current characteristic measuring device capable of setting current or voltage at a high speed without the need to lower the band of the system for stabilization.

In the present configuration, since the current source is used for the output, the output impedance can be designed to be resistive in a low frequency range, and it is easy to ensure the stability to a large capacity load.

Since the positive and negative circuits of the IF range resistor are independent of each other, a unidirectional FET switch can be used, so that the configuration and the control become simple, and the cost and the control can be reduced. it can.

In this configuration, when measuring the voltage between both ends of the IM resistor, the reference potential is set to the ground, so that the circuit configuration does not generate a common mode potential. Therefore, a highly accurate CMRR circuit is not required, and a large cost is obtained. Can be down.

Since the complicated control when changing the setting of the voltage and current or changing the range can be simplified, the hardware complexity is reduced, and the overload and spikes are reduced while the firmware load is greatly reduced. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional voltage-current characteristic measuring device.

FIG. 2 is a schematic diagram showing an operation of a CMRR circuit 52 in FIG.

FIG. 3 is a block diagram showing a voltage-current characteristic measuring device according to the present invention.

FIG. 4 is a flowchart illustrating a range switching method according to the present invention.

FIG. 5 is a flowchart illustrating a range switching method according to the present invention.

FIG. 6 is a flowchart illustrating a range switching method according to the present invention.

FIG. 7 is a flowchart illustrating a range switching method according to the present invention.

FIG. 8 is a block diagram showing a voltage-current characteristic measuring device according to the present invention.

FIG. 9 is a block diagram showing a voltage-current characteristic measuring device according to the present invention.

FIG. 10 is a block diagram showing another embodiment of the present invention.

FIG. 11 is a more detailed block diagram of a range resistor according to the present invention.

[Explanation of symbols]

 102: VF DAC (DA converter) 104: Integrator 106: VF range resistor 108: Amplifier 110: Capacitor 112: Clamp circuit 114, 116: Zener diode 118: Feedback resistor 120, 122: Photocoupler light emitting unit 124 , 126: photocoupler light receiving unit 128: buffer 130: VM terminal 132: output terminal 134: DUT 138, 139: photocoupler 150: IF DAC 152: Ip control unit 154, 164: current source 156, 166: IF Range resistance 160: Inverter 162: In control unit 180, 184: Current source 182, 186: Resistance 188: IM resistance 190: IM terminal

Claims (9)

[Claims] An output current supply unit including a first current source, a first range resistor, an output terminal, and an output control unit for controlling a current flowing through the output terminal; a second current source and the output terminal A current measuring unit provided with an IM resistor and a current measuring auxiliary resistor through which a current proportional to a current flowing through the first DA converter, an integrator with a clamp circuit, and an output for controlling an output current of the output current supply unit A voltage control unit including a control unit and a feedback circuit that feeds back the voltage of the output terminal and the output terminal to the integrator via a buffer amplifier and a feedback resistor; a second DA converter and the first current source And a current control unit having a control unit for controlling the current flowing from the second current source to be proportional to each other according to the output voltage of the second DA converter. Voltage-current characteristic measurement apparatus according to claim. 2. The control unit controls a current flowing through the first current source in accordance with a voltage at the first range resistor, and controls a current flowing through the second current source to the first range. 2. The method according to claim 1, wherein the control is performed in proportion to the voltage of the resistor.
The voltage-current characteristic measuring device according to the above. 3. An output current supply unit comprising: a first current source, a first range resistor, an output terminal to the DUT, and an output control unit for controlling a current flowing through the output terminal; a second current source and the DUT. A current measuring unit having an IM resistor and a current measuring auxiliary resistor through which a current proportional to the current flows, an integrator with a clamp circuit for preventing saturation of the first DA converter and the amplifier, and an output of the output current supply unit A voltage control unit including a feedback circuit that feedbacks the voltage of the output control unit, the output terminal, and the output terminal that controls a current to the integrator via a buffer amplifier and a feedback resistor; a second DA converter; A voltage / current converter for converting the output of the second DA converter into a current, a reference current generating unit having first and second reference current resistors, and a predetermined current of the reference current generating unit; And a current mirror control unit for controlling the current flowing from the first current source and the current flowing from the second current source in a proportional relationship based on the current flowing through the output current supply unit and the current flowing through a predetermined point of the output current supply unit. A voltage-current characteristic measuring device, comprising: a control unit. 4. The first range resistor and the first current source and the output control section, the second current source and the auxiliary resistor, and the control section respectively for positive and negative voltages. 4. The voltage-current characteristic measuring device according to claim 1, wherein two voltage-current characteristics measuring devices are provided. 5. The voltage-current characteristic measuring device according to claim 1, wherein the control unit includes a photocoupler. 6. The voltage-current characteristic measuring device according to claim 1, wherein the control unit includes a resistor and an FET. 7. The voltage-current characteristic measuring apparatus according to claim 1, wherein said integrator has a second range resistance. 8. A first D / A converter and at least a first photocoupler having two sets of terminals on a light emitting side and a light receiving side, respectively, wherein the first photocoupler on the light receiving side of the first photocoupler is provided. Is connected to a buffer amplifier, and is an integrator with a clamp circuit that prevents saturation during amplification. The input of the integrator is connected to the output of the first DA converter, Is connected to a first terminal on the light-emitting side of the first photocoupler, and a first current source connected to a second terminal on the light-receiving side of the first photocoupler; A first current range resistor connected to the other end of the first current source; and a feedback resistor connected to an output of the first buffer amplifier, wherein the feedback resistor is connected to a feedback input of the integrator. Connected, a second current source, and a second current source of the second current source. A first current monitor resistor connected to a second terminal of the second current source; a second DA converter; and a second DA converter. And at least a first current source control unit connected to the output of the first current source resistance unit, wherein the current flowing through the first current range resistor and the first current monitor 2. A voltage-current characteristic measuring device, wherein the current is controlled so as to be proportional to the output voltage of the second DA converter. 9. An output current supply unit including a current range resistor, a current source, and an output control unit for controlling current from the current source; a voltage D / A converter and a voltage range resistor; A voltage control unit that controls a current flowing to the output control unit in accordance with the output of the current D / A converter, And a current control unit having a control unit for controlling the voltage and current characteristics. (A) In the constant voltage source mode, only the I-limit range is increased, When lowering only the control current range in the constant current source mode, (a1) connect the next range resistance in parallel with the current range resistance, and (a2) connect the previous range resistance with the current range resistance. (A3) changing the setting of the current DA converter; (b) lowering only the I limit range in the constant voltage source mode; and changing only the control current range in the constant current source mode. (B1) Change the setting of the current DA converter, (b2) connect the range resistor of the next range in parallel with the current range resistor, and (b3) connect the previous range with the current range resistor. (C) When only the control voltage range is increased in the constant voltage source mode and when only the V limit range is decreased in the constant current source mode, (c1) the setting of the voltage DA converter is performed. (C2) connecting the next range resistor in the voltage range resistor in parallel, and (c3) disconnecting the previous range resistor in the voltage range resistor; (D) When only the control voltage range is reduced in the constant voltage source mode and when only the V limit range is increased in the constant current source mode, (d1) In the voltage range resistance, the range resistance of the next range is connected in parallel. (D2) disconnecting the previous range resistor in the voltage range resistor, and (d3) changing the setting of the voltage DA converter.