JPH09236637A - Voltage application current measuring circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an accurate measurement of a steady current in a fast operation type IC with a short settling time by adding a current supply circuit in which a current flows into a voltage output terminal detecting that a voltage of the voltage output terminal drops below a prescribed value to a current attraction circuit to attract current from a voltage supply terminal by detecting that the voltage is higher than the steady value. SOLUTION: A current output circuit 30 which supplies a voltage of a voltage output terminal TO detecting that the voltage of the voltage output terminal falls below a specified value and a current attraction circuit 40 which attracts a current from the voltage output terminal TO by detecting that the voltage of the voltage output terminal TO is higher by a specified value are connected to the voltage output terminal TO of a voltage supply circuit 10 so arranged that a negative feedback 25 is applied to an operational amplifier 11 to output a fixed voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IC such as a CMOS IC, which consumes a large load current only when an active element performs an inversion operation and consumes only a small current in a steady state, particularly in a power supply voltage supply terminal. The present invention relates to a voltage applied current measuring circuit that measures a minute current flowing in a state where a constant voltage is applied.

[0002]

2. Description of the Related Art FIG. 5 shows a schematic configuration of a voltage applied current measuring circuit which has been conventionally used. The voltage applied current measuring circuit is generally composed of a voltage supply circuit 10 and a current measuring means 20. The voltage supply circuit 10 outputs an operational amplifier 11 having a non-inverting input terminal to which a constant voltage V _in is applied, and a voltage V ₀ output from the operational amplifier 11, and supplies the output voltage V ₀ to the load 25. Output terminal TO
And a negative feedback circuit 12 for negatively feeding back the voltage V ₀ output to the voltage output terminal TO to the inverting input terminal of the operational amplifier 11.
A current measuring resistor 13 connected in series between the output terminal of the operational amplifier 11 and the voltage output terminal TO; and a diode anti-parallel circuit 14 connected in parallel with the current measuring resistor 13. , A phase compensation capacitor 15 which is further connected in parallel to a parallel connection circuit of a current measuring resistor 13 and an anti-parallel connected diode, and a bypass capacitor 16 which is connected to a voltage output terminal TO and a common potential point. .

The current measuring means 20 is a current measuring resistor 13
The differential amplifier 21 for taking out the voltage generated in the above and the AD converter 22 for taking out the AD value of the voltage value detected by the differential amplifier 21 can be constituted. A DA converter is generally used as the voltage source 18 for supplying a constant voltage V _in to the non-inverting input terminal of the operational amplifier 11, and the voltage value given to the non-inverting input terminal of the operational amplifier 11 is a digital value given to the DA converter. It is configured so that V _in can be set to an arbitrary voltage.

A load 25 is placed between the voltage output terminal TO and the common potential.
Is connected. The load 25 is assumed to be a CMOS IC here, and the current consumption value of the CMOS IC in a steady state is measured. That is, the load 25 is a CMOS type I
If it is C, an active element (FET) in the CMOS type IC
Every time the inverting operation is performed, the operating current IP as shown in FIG.
And the reversal operation ends, the current consumption becomes extremely small, and the steady current ΔI flows. The ratio between the operating current IP and the stationary current ΔI has a large ratio of, for example, about 1000: 1. Therefore, in order to accurately measure the steady-state current ΔI, after the operating current IP flows, a sufficient time has elapsed from the time when the steady-state current ΔI was switched and the voltage V ₀ at the voltage output terminal TO became stable (hereinafter The time until the voltage V ₀ stabilizes is called the settling time), and
The D conversion operation may be executed.

If the operating speed of the IC under test serving as the load 25 is slow and the cycle of the operating current IP is sufficiently long, the steady current ΔI can be accurately measured even if the settling time is long. However, there is a demand for higher speeds in ICs, and the cycle in which the operating current IP flows tends to become shorter year by year. Therefore, conventionally, in this type of voltage applied current measuring circuit, various measures have been taken to shorten the settling time.

As one of them, a bypass capacitor 16 is connected to the voltage output terminal TO, and the bypass capacitor 16 is always charged with a steady voltage V ₀ to obtain an operating current IP.
When the current flows in the load 25, the operating current I flowing in the load 25
Most of P is discharged from the bypass capacitor 16 so that the operating current IP required by the load 25 can be supplied without excess or deficiency.

Further, a device for connecting a diode antiparallel circuit 14 to the current measuring resistor 13 so as not to cause a large voltage drop in the current measuring resistor 13 while the operating current IP is flowing. In order to reduce the voltage fluctuation of the voltage output terminal TO when the operating current IP flows, it is preferable to set the capacitance value of the bypass capacitor 16 large. If the capacitance value of the bypass capacitor 16 is set to be large, the operation of the negative feedback circuit including the operational amplifier 11 becomes unstable (oscillation phenomenon is observed). In order to eliminate this phenomenon, the capacitance value of the position compensation capacitor is set large to eliminate the unstable phenomenon.

[0008]

By the way, when the capacitance value of the phase compensation capacitor 15 is large, the resistance value of the current measuring resistor 13 is also large. Therefore, the current measuring resistor 1
3 and the phase compensation capacitor 15 have large time constants, and the voltage at the voltage output terminal TO returns to the original steady voltage in accordance with this time constant. Therefore, the settling time becomes longer as the time constant becomes larger, and the high-speed operation IC It means that the steady current of cannot be measured.

An example of the settling time will be described below with numerical values. In order to obtain high-speed load fluctuation characteristics, it is required to improve the frequency characteristics of the entire circuit including the operational amplifier 11. Further, in order to measure the minute steady current ΔI, the resistance value R _m of the current measuring resistor 13 needs to be large. The operating current IP flowing during the operation of the CMOS type IC normally flows for several ns to several tens of nanoseconds.
In the negative feedback type voltage supply circuit 10 using the operational amplifier 11, the load fluctuation cannot be compensated for during the period when the operating current IP is flowing. Therefore, a bypass capacitor 16 is conventionally provided, and a current is supplied from the bypass capacitor 16 to the load 25 while the operating current IP is flowing, and after the operating current IP ends, the charge consumed from the operational amplifier 11 side is bypassed by the bypass capacitor 16. Is being supplied to.

If the time TP during which the operating current IP is flowing is short and the operating current IP is a constant current, the charge Q stored in the bypass capacitor 16 is generally Q = C *
Since V = I * T, the voltage fluctuation Δ of the voltage output terminal TO
V ₀ is ΔV ₀ ≈IP * TP / C ₁₆ , and the capacitance value C ₁₆ required for the bypass capacitor ₁₆ is C ₁₆ ≈IP * TP / Δ
It becomes V ₀ .

As a general example, IP = 500 mA, TP
= 100 ns, ΔV ₀ = 200 mV, C ₁₆ ≈IP * TP / ΔV = 500 mA * 100 ns / 200 m
V = 0.25 μF. The current measurement resolution when the current flowing through the voltage output terminal TO is in a steady state is 100 nA, the gain of the differential amplifier 21 provided in the current measuring means 20 is 10 times, and the measurement resolution of the A / D converter 22 is 1 mV. Then, the resistance value R _m of the current measuring resistor 13 becomes R _m = 1 mV / (100 nA * 10) = 1 KΩ.

The frequency response characteristic of the operational amplifier 11 is shown in FIG. In the figure, a curve A shows an attenuation characteristic of -6 dB per octave, and a curve B shows an attenuation characteristic of -12 dB per octave. Between the frequencies f1 and f2 shown in the figure per octave
It exhibits a damping characteristic of 12 dB, and this octave is -12 dB.
As is well known, if the attenuation characteristic of 0 is reached to 0 dB, the system operates in an unstable manner. In this frequency response characteristic, if the frequency f1 is f1≈1 / (2π * R _m * C ₁₆ ) = 636 Hz f _n is 100 MHz and the frequency f2 is 100 KHz for stable operation of the circuit, this frequency f2
The capacitance value C _m of the phase compensation capacitor 15 that gives the following is f2 = 1 / (2π * R _m * C _m ), so that C _m = 1 / (2π * R _m * f2) = 1600 PF.

The settling time during current measurement is the resistance value R _m of the current measuring resistor 13 and the phase compensation capacitor 15.
It is determined by the time constant of the capacitance value C _m . The voltage generated across the current measuring resistor 13 during the period when the operating current IP is flowing is clamped to the forward voltage of the antiparallel circuit 14 of the diodes. When the voltage generated in the current measuring resistor 13 during the period in which the operating current IP is flowing is 700 mV, until the voltage across the current measuring resistor 13 determined by the time constant τ = R _m * C _m is restored to 1 mV. Discharge time TS (setting time) of loge (1 mV / 700 mV) = − 6.55, TS = 6.55 (R _m * C _m ) = 6.55 * 1 KΩ × 1600 PF = 10.4 μs .

After all, it takes a settling time TS of about 10.4 μs until the voltage fluctuation ΔV _o of the voltage output terminal TO shown in FIG. 6B returns to the steady value V ₀ = V _in . This settling time TS If the time has not passed, the current measuring means 20 has a disadvantage of measuring a current value having a large error value even when measuring the current. Settling time TS
Is 10.4 μs, 1 / 10.4 μs ≈
0.1 × 10 ⁶ = 100 KHz, which means that only the IC having a frequency at which the operating current IP has a repetition frequency lower than 100 KHz can measure the steady-state current ΔI.

An object of the present invention is to set time T
It is an object of the present invention to provide a voltage applied current measuring circuit capable of shortening S and accurately measuring the steady-state current ΔI of a high-speed operation type IC.

[0016]

According to the present invention, an operational amplifier having a non-inverting input terminal to which a constant voltage is applied and an output voltage of the operational amplifier are applied, and an operation having a peak value periodically larger than a steady-state current. A voltage output terminal for supplying the output voltage to a load that consumes current, a voltage supply circuit configured by a feedback circuit for feeding back the voltage of the voltage output terminal to the inverting input terminal of the operational amplifier, and the voltage supply circuit A current measuring resistor connected between the output terminal and the voltage output terminal of the operational amplifier, a feedback circuit connected between the voltage output terminal and the inverting input terminal of the operational amplifier, and the voltage output terminal in common A bypass capacitor connected between the electric potential point, an anti-parallel connection circuit of a diode connected in parallel to the current measuring resistor, and a complementary circuit connected in parallel to the current measuring resistor. In a voltage applied current measuring circuit configured to include a capacitor and a current measuring unit that measures a voltage generated in the current measuring resistor and measures a current value output from the operational amplifier to a voltage output terminal. , The voltage output terminal detects that the voltage at this voltage output terminal has dropped below the specified value and supplies a current to the voltage output terminal, and detects that the voltage at the voltage supply terminal has exceeded the steady value. The present invention provides a voltage applied current measuring circuit to which a current attracting circuit for attracting current from a voltage supply terminal is added.

According to a second aspect of the present application, in the voltage applied current measuring circuit proposed in the first aspect, the current supply circuit and the current suction circuit are supplied with a voltage after a predetermined time elapses from the time point when the operating current flowing periodically is cut off. Provided is a voltage applied current measuring circuit to which a switching circuit for disconnecting from a terminal is added. According to claim 3 of this application, in the voltage applied current measuring circuit proposed in claim 1, the current supply circuit outputs a voltage slightly lower than the voltage value in a steady state output to the voltage supply terminal, and the voltage source. Provided is a voltage applied current measuring circuit configured by a diode having a source voltage applied to an anode and a cathode connected to a voltage supply terminal, and a current source having a current output terminal connected to an anode of the diode.

According to claim 4 of this application, in the voltage applied current measuring circuit proposed in claim 1, the current suction circuit outputs a voltage slightly higher than the steady-state voltage of the voltage output terminal, and this voltage source. The voltage of the source is applied to the cathode, the anode is connected to the diode connected to the voltage output terminal and the connection point between the cathode of this diode and the voltage source, and the voltage of the voltage supply terminal becomes higher than the voltage of the voltage source. There is provided a voltage applied current measuring circuit configured by a current source that draws current from a voltage supply terminal through a diode at a time point.

[0019]

According to the voltage-applied current measuring circuit proposed in claim 1 of the present application, the operating current IP having a large peak value flows in the IC to be tested as a load, so that the voltage at the voltage output terminal decreases. When the voltage fluctuates, a decrease in the voltage is detected by a current supply circuit provided separately from the voltage supply circuit configured by the negative feedback loop, and a current is supplied to the voltage output terminal. By supplying this current, the current that was conventionally supplied only from the voltage supply circuit is also supplied from the current supply circuit in the present invention to be supplemented, so that the voltage fluctuation width of the voltage output terminal can be suppressed to a small range.

Since the voltage fluctuation width of the voltage output circuit can be made small, it becomes possible to set the capacitance value of the bypass capacitor to a small value, which causes the time required for the voltage of the voltage supply circuit to return to the steady-state voltage. (Settling time) can be shortened. The present invention further proposes a configuration in which the voltage output terminal of the voltage supply circuit is provided with a current suction circuit that detects a rise in the voltage when the voltage of the voltage output terminal rises and sucks a current. By providing this current suction circuit, an operating current flows through the load, and when the operating current is cut off and returns to a steady current,
If an overshoot occurs in the voltage of the voltage output terminal, the overshoot is detected and the current is drawn. The overshoot is limited by the suction of this current. By this voltage limiting operation, the voltage at the voltage output terminal is quickly restored to the steady voltage, and the settling time can be shortened even if an overshoot occurs.

According to the voltage applied current measuring circuit proposed in claim 2, a switching circuit for disconnecting the current supply circuit and the current suction circuit from the voltage output terminal when a predetermined time elapses from the time when the operating current is cut off. Since I proposed a configuration with
It is possible to provide a voltage application current measurement circuit in which an error does not occur in the current measurement value due to the current flowing through the current supply circuit and the current suction circuit.

[0022]

FIG. 1 shows an embodiment of a voltage applied current measuring circuit according to the present invention. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals. That is, 10 is a voltage supply circuit, TO is a voltage output terminal, and 25 is an IC under test.
Is a load, 30 is a current supply circuit added in the present invention, and 40 is a current suction circuit.

Since the structure and operation of the voltage supply circuit 10 are the same as those described with reference to FIG. 5, their duplicate description will be omitted here. The characteristic feature of the present invention is that the current supply circuit 30 and the current suction circuit 40 are also connected to the voltage output terminal TO. The current supply circuit 30 has a voltage output terminal T
A voltage source 31 that produces a slightly lower voltage VL due to the steady state voltage of O at the steady state voltage V ₀ = V _in.
A diode 33 in which the voltage of the voltage source 31 is applied to the anode, the cathode is connected to the voltage output terminal TO, and the anode is connected to the current output terminal of the current source 32.
And a diode 34 connected between the anode of the diode 33 and the voltage source 31.

The current suction circuit 40 includes a voltage source 41 which outputs a voltage VH slightly higher than the output voltage V ₀ = V _in of the voltage output terminal TO in a steady state, and a voltage VH of the voltage source 41 which is applied to the cathode of the anode. Is connected to the voltage output terminal TO, and the attracting current source 42 is connected to the cathode of the diode 43. The cathode of the diode 43 and the voltage source 4 are connected.
1 and the diode 44 connected between the two.

In the steady state where the voltage of the voltage output terminal TO is V ₀ = V _in , the diode 3 of the current supply circuit 30
4 and the diode 44 of the current sink circuit 40 are kept in the ON state as shown in FIGS.
3 remains off. Therefore, the current I1 supplied from the current source 32 flows to the common potential point COM through the diode 34 and the voltage source 31. The current I2 drawn by the current source 42 is drawn by the current source 42 from the common potential point COM through the voltage source 41 and the diode 44.

In this state, the operating current IP (see FIG. 2) is applied to the load 25.
2A flows, and the operating current IP flows, the voltage V ₀ of the voltage output terminal TO decreases as shown in FIG. 2B. When the voltage V ₀ becomes lower than the voltage VL of the voltage source 31, the diode 34 becomes Since the diode 33 is turned off and the diode 33 is turned on instead, the current I1 supplied from the current source 32 is injected into the voltage output terminal TO.

When a current is injected from the current supply circuit 30 to the voltage output terminal TO, the bypass capacitor 16
Is charged by this current I1, and the voltage fluctuation ΔV ₀ is clamped so as not to drop below the voltage VL. As a result, the fluctuation width of the voltage fluctuation ΔV _{0 at} the voltage output terminal TO is suppressed to a small fluctuation width determined by the voltage VL of the voltage source 31. Since the voltage fluctuation width is suppressed to a small value, the voltage of the voltage output terminal TO can return to the steady value V ₀ = V _in within a very short time from the time when the operating current IP is cut off. .

Here, the voltage variation ΔV ₀ of the voltage output terminal TO
Since the fluctuation range of can be made small, there is an advantage that the capacitance value C ₁₆ of the bypass capacitor 16 can be made small. Capacitance C ₁₆ of the bypass capacitor 16, a current supply circuit 30
2 switching time (time when operating current IP flows)
If nS, C ₁₆ ≉IP * TP / ΔV ₀ ≅500 mA * 2 nS / 200 mV = 0.005 μF.

The resistance value R _m of the current measuring resistor 13 remains unchanged and is 1 KΩ. Frequency f1 of the frequency characteristics shown in FIG. 7 by the determined capacitance value C ₁₆ of the bypass capacitor 16, f1 ≒ 1 / (2π ※ R m ※ C 16) = 31.8kHz f n the circuit stably as 100MHz When the frequency f2 for operating is 1 MHz, the capacitance value C _m of the phase compensation capacitor 15 is C _m = 1 / (2π * R _m * f2) = 160 PF.

In this way, the capacitance of the phase compensation capacitor 15 is
Quantity C_mIs about 1/10 of the conventional value, so the resistance for current measurement is
Resistance value R of the armor 13_mAnd the capacitance of the phase compensation capacitor 15
Value C _mDischarge time TS (set ring tie
Is TS = 6.55τ = 6.55 * 1KΩ * 160PF =
1.04 μs, shortening the settling time TS to 1/10
be able to.

On the other hand, in the present invention, if the amount of current injected from the current supply circuit 30 is large when the operating current IP is cut off, the voltage at the voltage output terminal TO transiently changes as shown by the solid line in FIG. 2B. It is possible that a so-called overshoot occurs. When this overshoot occurs and the voltage of the overshoot exceeds the voltage VH of the voltage source 41, the diode 43 provided in the current suction circuit 40 is turned on, and the current source 42 outputs the current I2 from the voltage output terminal TO.
Aspirate. Due to this current attraction, the overshoot voltage is clamped to the voltage VH of the voltage source 41, and the voltage VH
Suppressing rise above H. As a result, since the amount of overshoot is limited, the settling time can be shortened even if overshoot occurs.

FIG. 3 shows an embodiment in which switching circuits 50 and 60 proposed in claim 2 of this application are added. In FIG. 3, the voltage supply circuit 10 is omitted. In this embodiment, the switching circuit 5 is activated when the operating current IP flows through the load 25.
Diodes 52 and 62 of 0 and 60 are connected to voltage sources 51 and 61.
Is controlled by the positive voltage V _swp and the negative voltage V _swn output by the power supply circuit 30 to turn on the current sources 32 and 42.
And is kept connected to the current suction circuit 40. Therefore, the current supply circuit 30 and the current suction circuit 40 perform the current supply and the suction operation as described with reference to FIG. The voltage V _swp and V _swn generated from the voltage sources 51 and 61 are returned to 0 (zero) when a predetermined time TM (see FIG. 4B) has elapsed from the time when the operating current IP was cut off, and the diode 5
Control 2 and 62 off. This results in current sources 32 and 42
Is separated from the current supply circuit 30 and the current suction circuit 40,
The currents of the current sources 32 and 42 are prevented from leaking to the voltage output terminal TO. Therefore, by measuring the current with the current measuring means 20 after the current sources 32 and 42 are disconnected from the circuit, the currents of the current sources 32 and 42 are not affected, and
The current can be measured.

[0033]

As described above, according to the present invention, the current supply circuit 30 supplements the current supply function of the voltage supply circuit 10 configured by the negative feedback circuit, and the operating current IP having a large peak value flows. However, since the voltage fluctuation amount of the voltage output terminal TO is reduced, the current supply capacity of the voltage supply circuit 10 can be reduced. That it is possible to set the capacitance value C ₁₆ in the bypass capacitor 16 to a small value. Since it is possible to set the capacitance value C ₁₆ in the bypass capacitor 16 to a small value, the phase compensation capacitor 1
The capacitance value C _{m of} 5 can also be set to a small value, and the time constant R _m * C _m with the current measuring resistor 13 can be reduced. This makes the operating current IP with a large peak value
The settling time until the voltage of the voltage output terminal TO immediately after the flow of the current returns to the steady-state voltage can be shortened, and as a result, the steady-state current can be obtained even when the cycle period of the operating current IP is high. It will be possible to measure ΔI accurately.

Further, according to the voltage applied current measuring circuit proposed in claim 2, at the time of measuring the current, the current supplying circuit 30 for supplementing the current and the current attracting circuit 4 for removing the overshoot.
Since the current sources 31 and 41 forming 0 are separated from the circuit, they are not affected by the leakage currents of the switching diodes 33 and 43. Therefore, the provision of the current supply circuit 30 and the current suction circuit 40 does not impair the reliability of the measured current value.

Further, in the current supply circuit 30 and the current suction circuit 40, the period in which the operating current IP is flowing ends, and the diodes 33 and 43 are controlled to be in the off state during the measurement of the minute current in the steady state, and the voltage output is performed. No current is output to the terminal TO side. As a result, the current sources 32 and 42 and the voltage sources 31 and 41 are required to have only high-speed responsiveness, and low noise characteristics and highly accurate output voltage stability are not required, so that the device can be easily manufactured.

Further, the capacitance value C of the bypass capacitor 16
_{Since 16} can be set to a small value, the influence of uncertain current due to noise can be reduced. That is, if noise is present in the output of the voltage supply circuit 10,
A noise current flows through the bypass capacitor 16, and this noise current becomes an uncertain current when measuring a minute current. By the way 1
When 10 μV noise is generated at 00 KHz, the noise current is conventionally C ₁₆ = 0.250 μF Z _C = 1 / (2π * f * 0.250 μF) = 6.3Ω Noise current = 10 μV / 6.3Ω = 1.58 μA In the present invention, C ₁₆ = 0.005 μF Z _C = 1 / (2π * f * 0.005 μF) = 318 Ω Noise current = 10 μV / 318 Ω = 0.03 μA, and the noise required for the voltage supply circuit 10 The characteristics can also be significantly eased.

[Brief description of drawings]

FIG. 1 is a connection diagram for explaining an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a connection diagram for explaining a circuit configuration of a main part proposed in claim 2 of the present invention.

FIG. 4 is a waveform diagram for explaining the operation of FIG.

FIG. 5 is a connection diagram for explaining a conventional technique.

6 is a waveform diagram for explaining the operation of FIG.

7 is a frequency characteristic curve diagram for explaining the operation of FIG.

[Explanation of symbols]

 10 Voltage Supply Circuit 11 Operational Amplifier 12 Negative Feedback Circuit 13 Current Measuring Resistor 14 Diode Anti-Parallel Circuit 15 Phase Compensation Capacitor 16 Bypass Capacitor TO Voltage Output Terminal 18 Voltage Source 20 Current Measuring Means 25 Load 30 Current Supply Circuit 40 Current Absorption Circuit 50, 60 Switching circuit

Claims (4)

[Claims] 1. An operational amplifier to which a constant voltage is applied to an input terminal and an output voltage of the operational amplifier are applied to a load which periodically consumes an operating current having a peak value larger than a steady-state current. A voltage output circuit for supplying a voltage, a voltage supply circuit configured by a feedback circuit for feeding back the voltage of the voltage output terminal to the inverting input terminal of the operational amplifier, and an output terminal and a voltage output terminal of the operational amplifier forming the voltage supply circuit. A current measuring resistor connected between the current measuring resistor, a bypass capacitor connected between the voltage output terminal and a common potential point, an anti-parallel connection circuit of diodes connected in parallel to the current measuring resistor, and The current value output from the operational amplifier to the voltage output terminal by measuring the voltage generated in the phase compensation capacitor connected in parallel with the current measuring resistor and the current measuring resistor. In a voltage applied current measuring circuit configured to include a current measuring unit for measuring the voltage, the voltage output terminal detects that the voltage at the voltage output terminal has dropped below a specified value, and supplies a current to the potential supply terminal. A voltage applied current measuring circuit characterized by adding a flowing current supply circuit and a current suction circuit for detecting that the voltage of the voltage supply terminal has become higher than a steady value and drawing a current from the voltage supply terminal. . 2. The voltage applied current measuring circuit according to claim 1, wherein the current supply circuit and the current suction circuit are disconnected from the voltage supply terminal after a lapse of a predetermined time from the time point when the operating current flowing periodically is cut off. A voltage applied current measuring circuit characterized by adding a switching circuit for separating. 3. The voltage applied current measuring circuit according to claim 1, wherein the current supply circuit outputs a voltage slightly lower than a steady-state voltage value output to the voltage supply terminal, and the voltage source. Is applied to the anode of the voltage supply circuit, the cathode of which is connected to the voltage output terminal of the voltage supply circuit, and the current output terminal of which is connected to the anode of the diode. Measurement circuit. 4. The voltage applied current measuring circuit according to claim 1, wherein the current suction circuit outputs a voltage slightly higher than a steady-state voltage of the voltage output terminal, and the voltage of the voltage source is a cathode. When the voltage of the voltage supply terminal is higher than the voltage of the voltage source, the anode of which is connected to the voltage output terminal and the connection point of the diode cathode and the voltage source. And a current source that draws a current from the voltage output terminal through the diode.