JP7304247B2 - Voltage measuring devices and devices with sensors - Google Patents

Description

Application of Patent Act Article 30, Paragraph 2 Announced at the 3rd International Test Conference in Asia, Tokyo held on September 4, 2019 [Publications] 3rd held on July 23, 2019 Presented at the International Test Conference in India, Bangalore, India [Publications] 5th Taiwan and Japan Conference on Circuits and Systems (TJCAS 2019 at Nikk o) [Publication etc.] Presented at the 71st System LSI Joint Seminar held on January 26, 2019 Presented at Circuit design technology and electronic circuits in general

The present invention relates to a voltage measuring device for measuring minute voltage.

In order to test the performance of semiconductor devices, there are cases where it is desired to measure minute direct current (DC) voltages with high accuracy. For example, conventionally, a digital voltmeter using the Null method has been used to measure various characteristics of operational amplifiers (for example, DC offset voltage).

James M. Bryant, "Simple Op Amp Measurement", Analog Dialogue, Vol. 45, pp. 21-23 (2011)

However, with a voltmeter using the Null method, the effects of system noise, 1/f noise, and electromotive force (EMF) mixed in the amplification stage cannot be ignored, making it impossible to accurately measure voltages on the order of μV. becomes difficult.

In addition, in semiconductor testing, it is required to test each chip in about one second or less, and to simultaneously measure a plurality of semiconductor chips.

The present invention has been made in such a situation, and one exemplary object of some aspects thereof is to provide a voltage measuring device capable of measuring a voltage on the order of μV with high accuracy.

One aspect of the present invention relates to a voltage measurement device. A voltage measuring device includes an input terminal for receiving a DC input voltage, a DC/AC converter for converting the input voltage into an AC voltage having an amplitude and a predetermined frequency corresponding to the input voltage, and an amplifier for amplifying the AC voltage. and a detector for detecting the voltage level of the input voltage based on a predetermined frequency component contained in the amplified AC voltage.

Arbitrary combinations of the above constituent elements, or conversions of expressions of the present invention between methods, devices, etc. are also effective as aspects of the present invention.

According to one aspect of the present invention, a voltage on the order of μV can be measured with high accuracy.

1 is a circuit diagram of a voltage measuring device according to Embodiment 1; FIG. 2 is an operation waveform diagram of the voltage measuring device of FIG. 1; FIG. It is a circuit diagram which shows the structural example of a voltage measuring apparatus. It is a figure which shows the spectrum obtained by a voltage measuring apparatus. FIG. 5(a) is a diagram showing the relationship (measurement result) between the input voltage V _IN and the signal strength of the fundamental wave _f0 , and FIG. 5(b) is a diagram showing the relationship between the input voltage V _IN and the relative error. is. 6A and 6B are diagrams showing the relationship between the input voltage _VIN and the signal strength (measurement result) of the fundamental wave _f0 . 4 is a waveform diagram (actual measurement) showing switching noise included in the AC voltage _{VAC_AMP; FIG} . FIG. 10 is a circuit diagram of a voltage measuring device according to Embodiment 2; 9 is an operation waveform diagram of the voltage measuring device of FIG. 8. FIG. FIG. 9 is a diagram showing a configuration example of the voltage measuring device of FIG. 8; FIG. 4 is a diagram showing a modification of the DC/AC converter and dummy circuit; FIG. 9 is a waveform diagram (actual measurement) of an AC voltage _{VAC_AMP} obtained by the voltage measuring device of FIG. 8; FIG. 10 is a diagram schematically showing a voltage measuring device in which thermal EMF countermeasures are taken; FIG. 10 is a waveform diagram (actual measurement) of the AC voltage _{VAC_AMP} in the voltage measuring device after countermeasures against thermal EMF are taken; FIG. 15(a) is a diagram showing the relationship (measurement result) between the input voltage _VIN and the signal strength of the fundamental wave _f0 in the voltage measuring device after thermal EMF countermeasures are taken, and FIG. FIG. 4 is a diagram showing the relationship between _VIN and relative error; FIG. 10 is a circuit diagram of a voltage measuring device according to Embodiment 3; FIG. 17 is a diagram showing a spectrum obtained by the voltage measuring device of FIG. 16; FIG. 11 is a circuit diagram of a voltage measuring device according to Modification 3; 19(a) and 19(b) are block diagrams showing applications of the voltage measurement circuit.

(Overview of Embodiment)
One embodiment disclosed herein relates to a voltage measurement device. A voltage measuring device includes an input terminal for receiving a DC input voltage, a DC/AC converter for converting the input voltage into an AC voltage having an amplitude and a predetermined frequency corresponding to the input voltage, and an amplifier for amplifying the AC voltage. and a detector for detecting the voltage level of the input voltage based on a predetermined frequency component contained in the amplified AC voltage.

In a conventional configuration for amplifying a DC input voltage, system noise and 1/f noise at a level that cannot be ignored are superimposed on the signal component in the amplification stage. Accurately measuring the voltage level at _IN is difficult. In one embodiment, the influence of system noise and 1/f noise is eliminated by converting an input voltage into an AC voltage of a known frequency, amplifying it, and detecting the amplitude of the known frequency component of the amplified AC voltage. can be removed and the input voltage can be measured accurately.

The DC/AC converter complementarily switches the first switch and the second switch provided in series between the input terminal and the ground, and the first switch and the second switch according to a clock having a predetermined frequency. and a first driver.

The DC/AC converter may be thermally isolated from the amplifier and detector. As a result, the influence of thermal EMF can be reduced, and the measurement range can be widened.

"Thermal isolation of A and B" means mounting A and B on different substrates, mounting A and B separately in different regions on the same substrate, and mounting A and B on different heat sinks. connecting, covering one of A and B with insulation, and the like.

The voltage measuring device may further include a dummy circuit that has the same configuration as the DC/AC converter and operates synchronously with the DC/AC converter. The amplifier may include a differential amplifier having one input receiving an AC voltage and the other input receiving the output of the dummy circuit. The effect of switching noise can be canceled by generating the same switching noise as the DC/AC converter with the dummy circuit and subtracting it from the AC voltage with the differential amplifier.

The dummy circuit may include a third switch and a fourth switch provided between the ground and the ground, and a second driver for complementarily switching the third switch and the fourth switch according to the clock.

The DC/AC converter and dummy circuit may be thermally isolated from the amplifier and detector. This can reduce the influence of thermal EMF.

A plurality of switches that constitute the DC/AC converter and the dummy circuit may be connected to a common heat sink.

The detector includes an A/D converter that converts an AC voltage into a digital signal and a Fourier transformer that Fourier-transforms the output waveform of the A/D converter. , the voltage level of the input voltage may be detected.

The detection unit may include a filter that extracts a predetermined frequency component of the AC voltage, and detect the voltage level of the input voltage based on the amplitude of the signal that has passed through the filter.

The voltage measuring device includes at least one input terminal for receiving at least one input voltage, at least one DC/AC converter corresponding to the at least one input terminal, an AC voltage generated by the DC/AC converter, and at least an adder for adding at least one AC voltage produced by one DC/AC converter. Each of the at least one DC/AC converter converts a corresponding input voltage into an AC voltage having an amplitude dependent on the input voltage and a frequency unique to each. This allows multiple input voltages to be measured simultaneously. In particular, by using the Fourier transform, it is possible to simultaneously measure the voltage levels of a plurality of input voltages with one Fourier transform.

(Embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplication of description will be omitted as appropriate. Moreover, the embodiments are illustrative rather than limiting the invention, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention.

In this specification, "a state in which member A is connected to member B" refers to a case in which member A and member B are physically directly connected, or a case in which member A and member B are electrically connected to each other. It also includes the case of being indirectly connected through other members that do not substantially affect the connected state or impair the functions and effects achieved by their combination.

Similarly, "the state in which member C is provided between member A and member B" refers to the case where member A and member C or member B and member C are directly connected, as well as the case where they are electrically connected. It also includes the case of being indirectly connected through other members that do not substantially affect the physical connection state or impair the functions and effects achieved by their combination.

(Embodiment 1)
FIG. 1 is a circuit diagram of a voltage measuring device 100A according to Embodiment 1. FIG. The voltage measuring device 100 detects the voltage level of the DC input voltage _{VIN input} to the input terminal PIN. The voltage level of the input voltage _VIN is typically on the order of μV or sub-μV. The input voltage V _IN to be measured is not particularly limited.

100 A of voltage measuring apparatuses are provided with the DC/AC converter 110, the amplifier 120, and the detection part 130. FIG. The DC/AC converter 110 converts the input voltage V _IN to an AC voltage V _AC having an amplitude corresponding to the input voltage V _IN and a predetermined frequency f ₀ . The AC voltage _VAC is preferably a rectangular wave with a duty ratio of 50% that switches between two voltage levels, the input voltage _VIN and the reference voltage (eg, ground voltage 0V). For example, the switching frequency _f0 is 1 kHz.

Amplifier 120 amplifies _AC voltage VAC with a predetermined gain. The detection unit 130 detects the voltage level of the input voltage _VIN based on the amplified AC voltage _{VAC_AMP} .

The above is the basic configuration of the voltage measuring device 100A. Next, the operation will be explained. FIG. 2 is an operation waveform diagram of the voltage measuring device 100A of FIG.

A DC input voltage V _IN of several μV is input to the input terminal P _IN . A DC/AC converter 110 generates a square-wave AC voltage V _AC having an amplitude equal to V _IN , a duty ratio of 50%, and a period T ₀ =1/f ₀ . The AC voltage _VAC is amplified by the amplifier 120 in the subsequent stage. The amplitude of the amplified AC voltage V _{AC_AMP} is V _IN ×g. The amplified AC voltage _{VAC_AMP} is a periodic rectangular wave and is represented by the following equation (1).

A Fourier series expansion of the rectangular wave of Equation (1) is expressed by Equation (2).

Detector 130 measures the amplitude of the component of predetermined frequency _f0 included in amplified AC voltage _{VAC_AMP} . A component of the predetermined frequency _f0 is represented by equation (3).

A value obtained by dividing the measured amplitude of the fundamental wave component by a constant (2gV _IN /π) based on the gain g is the voltage level of the original input voltage V _IN .

The above is the operation of the voltage measuring device 100A. In the present embodiment, the input voltage V _IN is converted into an AC voltage V _AC having a known frequency _f0 and then amplified, and the amplitude of the component of the AC voltage V _AC after amplification having a known frequency _f0 is detected. , system noise and 1/f noise can be removed, and the input voltage _VIN can be accurately measured.

The present invention extends to various apparatus and methods grasped as the block diagram and circuit diagram of FIG. 1 or derived from the above description, and is not limited to any particular configuration. Hereinafter, more specific configuration examples and embodiments will be described not for narrowing the scope of the present invention, but for helping to understand the essence and operation of the invention and clarifying them.

FIG. 3 is a circuit diagram showing a configuration example of the voltage measuring device 100A. DC/AC converter 110 includes a first switch SW 1 , a second switch SW 2 and a first driver 112 . A first switch SW1 and a second switch SW2 are provided in series between the input terminal P _IN and ground. The first driver 112 complementarily switches the first switch SW1 and the second switch SW2 according to a clock CLK having a predetermined frequency _f0 .

Each of the first switch SW1 and the second switch SW2 may be composed of a CMOS switch (transfer gate). Alternatively, the first switch SW1 may be composed of a PMOS transistor, and the second switch SW2 may be composed of an NMOS transistor. Alternatively, both of them may be composed of NMOS transistors.

The amplifier 120 is a non-inverting amplifier including an operational amplifier 122 and resistors R ₁₁ and R ₁₂ and has a gain g=(R ₁₁ +R ₁₂ )/R ₁₂ determined according to the resistor values R ₁₁ and R ₁₂ .

The detector 130 includes a DC block capacitor C ₂ , an AC amplifier 132 , an A/D converter 134 and a Fourier transformer 136 . A DC blocking capacitor _C2 removes the DC component of the alternating voltage V _AC . This DC component includes the constant term gV _IN /π in equation (2), system noise, and 1/f noise.

AC amplifier 132 amplifies the AC component of AC voltage _{VAC_AMP} . The A/D converter 134 converts the AC voltage _{VAC_DUMMY} into a digital signal at a predetermined sampling rate. The Fourier transformer 136 performs Fast Fourier Transform (FFT) on the output waveform of the A/D converter 134 to generate a spectrum in the frequency domain. A low-pass filter having a cutoff frequency fc (fc<fs/2) corresponding to the sampling frequency fs of the A/D converter 134 is inserted before the A/D converter 134 in order to remove anti-aliasing noise. .

FIG. 4 is a diagram showing a spectrum obtained by the voltage measuring device 100A. Based on the intensity of the fundamental wave _f0 , the signal intensity of a given frequency _f0 included in the spectrum obtained by the Fourier transformer 136 correlates with the voltage level of the input voltage _VIN .

FIG. 5(a) is a diagram showing the relationship (measurement result) between the input voltage V _IN and the signal strength of the fundamental wave _f0 . It is assumed that f ₀ =1 kHz, the number of samples is 10000, the sampling rate is 100 ksps, and the frequency resolution is 10 Hz. FIG. 5(b) is a diagram showing the relationship between the input voltage _VIN and the relative error. In this example, it can be seen that linearity is ensured up to 2 μV.

6A and 6B are diagrams showing the relationship between the input voltage _VIN and the signal strength (measurement result) of the fundamental wave _f0 . FIG. 6(a) is the result when f ₀ =500 Hz, and FIG. 6(b) is the result when f ₀ =2 kHz. It can be seen that the lower the frequency f ₀ of the AC voltage _VAC , the more accurately the voltage range can be measured.

The inventors of the present invention have studied why the measurable range widens as the switching frequency f ₀ decreases, and have come to recognize that switching noise has an effect. FIG. 7 is a waveform diagram (actual measurement) showing switching noise included in the AC voltage _{VAC_AMP} . In this example, f ₀ =1 kHz. Switching noise is generated in the AC voltage _{VAC_AMP} at each edge of the clock CLK. The main frequency component of the switching noise is _2f0 which is twice the switching frequency _f0 , but the switching noise also contains the frequency component of the fundamental frequency _f0 , which degrades the linearity.

Switching noise can be reduced by devising a layout on the circuit because the clock CLK is mixed in through the parasitic capacitance. Embodiment 2 describes a voltage measurement device 100B capable of suppressing the influence of switching noise.

(Embodiment 2)
FIG. 8 is a circuit diagram of a voltage measuring device 100B according to the second embodiment. Voltage measuring device 100B further includes dummy circuit 140 . Dummy circuit 140 is a replica of DC/AC converter 110 having the same configuration as DC/AC converter 110 and operates in synchronization with DC/AC converter 110 . However, 0 V is input to the DC/AC converter 110 instead of the input voltage _VIN .

The amplifier 120 includes a differential input-single-ended output differential amplifier 124 . The output V _AC of the DC/AC converter 110 is input to one input terminal (non-inverting input +) of the differential amplifier 124, and the output voltage of the dummy circuit 140 is input to the other input terminal (inverting input -). _{VAC_DUMMY} is input.

The above is the configuration of the voltage measuring device 100B. Next, the operation will be explained. FIG. 9 is an operation waveform diagram of the voltage measuring device 100B of FIG. The output _VAC of the DC/AC converter 110 contains a rectangular wave component whose amplitude is the input voltage _VIN and switching noise. The output voltage of the dummy circuit 140 contains only switching noise. By amplifying the difference V _AC -V _{AC_DUMMY} between the two signals V _AC and V _{AC_DUMMY} by the differential amplifier 124, the effect of switching noise can be removed.

FIG. 10 is a diagram showing a configuration example of the voltage measuring device 100B of FIG. DC/AC converter 110 includes a first switch SW 1 , a second switch SW 2 and a first driver 112 .

The dummy circuit 140 includes a third switch SW3 and a fourth switch SW4 provided between the input and the ground, a second driver 142 that complementarily switches the third switch SW3 and the fourth switch SW4 according to the clock, including. The input of dummy circuit 140 is grounded.

FIG. 11 is a diagram showing a modification of DC/AC converter 110 and dummy circuit 140. In FIG. If the signal source that produces the input voltage V _IN has a non-negligible output impedance Rs, resistors Rd1-Rd4 may be added to DC/AC converter 110 and dummy circuit 140, respectively. Resistors Rd1-Rd4 are provided for impedance matching and their resistance value Rd is equal to the output impedance Rs. Specifically, if Rs≠Rd, the switching noise becomes unbalanced when converted into voltages by the resistors Rs and Rd, which can be a factor that hinders the reduction of switching noise in the differential circuit, so let Rs=Rd. Therefore, switching noise can be reduced. Also, the thermoelectromotive force at the resistor Rs of the signal source and that at the resistor Rd can be balanced.

The inventors mounted the voltage measuring device 100B of FIG. 8 on a common substrate, and measured the waveform of the AC voltage _{VAC_AMP} after amplification. FIG. 12 is a waveform diagram (actual measurement) of the AC voltage _{VAC_AMP} obtained by the voltage measuring device 100B of FIG. This waveform was measured with the input voltage _VIN as zero, but a square wave (noise) equivalent to 1 μV in _terms of the input voltage VIN was observed in the AC voltage _{VAC_AMP} in synchronization with the 1 kHz clock CLK. there is The inventors have recognized that this noise is due to thermal EMF.

As a countermeasure against thermal EMF, the DC/AC converter 110 and the dummy circuit 140 in the voltage measuring device 100B are thermally separated from the amplifier 120 in the subsequent stage. FIG. 13 is a diagram schematically showing a voltage measuring device 100C with measures against thermal EMF. The voltage measuring device 100C is a voltage measuring device configured using discrete elements.

Specifically, DC/AC converter 110 and dummy circuit 140 are mounted separately from circuit board 200 on which amplifier 120 is mounted. Switches SW1 to SW4 and drivers 112 and 142 that constitute DC/AC converter 110 and dummy circuit 140 are incorporated in one switch IC 202 . A heat sink 204 is connected to one surface (upper side in the drawing) of the switch IC 202 . Another surface of the switch IC 202 is connected to a conductive sheet 206 , and a heat sink 208 is connected to the conductive sheet 206 . If DC/AC converter 110 and dummy circuit 140 include resistors, resistor chips are also mounted on the conductive sheet 206 side.

Furthermore, the switch IC 202 (resistor chip) and heat sink that constitute the DC/AC converter 110 and the dummy circuit 140 are covered with a heat insulating member 210 (for example, foamed polystyrene). Further, the voltage measuring device 100C as a whole was housed in a heat insulating container so as not to be affected by external heat. FIG. 14 is a waveform diagram (actual measurement) of the AC voltage _{VAC_AMP} in the voltage measuring device 100C after measures against thermal EMF are taken. Due to thermal EMF countermeasures, the square wave noise seen in FIG. 12 is greatly reduced.

FIG. 15A is a diagram showing the relationship (measurement result) between the input voltage V _IN and the signal intensity of the fundamental wave f ₀ in the voltage measuring device 100C after thermal EMF countermeasures are taken. In FIG. 5, the linearity can be secured in a range of more than 2 μV, whereas in FIG. 15, the range in which the linearity can be secured can be expanded to 0.2 μV. FIG. 15(b) is a diagram showing the relationship between the input voltage _VIN and the relative error. The relative error at 0.2 μV is 20%.

It should be noted that the thermal EMF countermeasures described here are also effective for the first and third embodiments and some modifications described later.

(Embodiment 3)
In the third embodiment, a voltage measuring device 100D that can simultaneously measure a plurality of input voltages _VIN will be described. This voltage measuring device 100D is based on the voltage measuring device 100A according to the first embodiment and is multi-channeled.

FIG. 16 is a circuit diagram of voltage measuring device 100D according to the third embodiment. The voltage measuring device 100D can simultaneously measure N-channel (N≧2) input voltages V _IN1 to V _INN .

The voltage measuring device 100D includes N-channel DC/AC converters 110_1 to 110_N, N-channel amplifiers 120_1 to 120_N, and a detector 130D.

The plurality of DC/AC converters 110_1 to 110_N are supplied with clocks CLK ₁ to CLK _N having different unique frequencies f ₁ to _fN . Focusing on the i-th channel (i=1 to N), the DC/AC converter 110_i converts the corresponding input voltage V _INi into an AC voltage V _ACi having a frequency f _i and an amplitude V _INi . Since the subsequent FFT must be able to separate the signal components for each channel, the frequencies f ₁ to f _N are non-integer multiples of each other. Amplifier 120_i amplifies the corresponding AC voltage _VACi .

The detector 130D includes an adder 138 that adds the amplified AC voltages V _{AC_AMP1} to V _{AC_AMPN} . A summing amplifier using an operational amplifier can be used for the adder 138 . This adder 138 can double as an amplifier.

The A/D converter 134 converts the additionally amplified signal into a digital signal. The Fourier transformer 136 performs Fast Fourier Transform (FFT) on the output waveform of the A/D converter 134 to generate a spectrum in the frequency domain.

FIG. 17 is a diagram showing a spectrum obtained by voltage measuring device 100D of FIG. The components of the fundamental waves f ₁ to f _N included in the spectrum are respectively correlated with the voltage levels of the plurality of input voltages V _IN1 to V _INN .

As described above, according to the third embodiment, it is possible to simultaneously measure the input voltages V _IN1 to V _INN of multiple channels in a short time.

The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that this embodiment is merely an example, and that various modifications can be made to the combination of each component and each treatment process, and that such modifications are within the scope of the present invention. be. Such modifications will be described below.

(Modification 1)
In Embodiment 3, the voltage measuring device 100D of FIG. 16 may be used as a base for multi-channeling. That is, the voltage measuring device 100B of FIG. 8 may be multi-channeled for each channel as a countermeasure against switching noise.

(Modification 2)
In FIG. 16, the multi-channel signals V _{AC_AMP1} to V _{AC_AMPN} after amplification are added in the detection unit 130, but they may be amplified by the common amplifier 120 after being combined before amplification. In this case, the circuit configuration can be made smaller.

(Modification 3)
In the description so far, the detection unit 130 is configured based on FFT, but this is not the only option. FIG. 18 is a circuit diagram of a voltage measuring device 100E according to Modification 3. As shown in FIG. It is a circuit diagram of the detection unit 130E. The detector 130E includes a filter 150 and a detector 152. FIG. The filter 150 is a low-pass filter or a band-pass filter, and transmits the component of the switching frequency _f0 of the signal after amplification. Detector 152 detects the amplitude of the signal that has passed through filter 150 . This amplitude correlates with the voltage level of the input voltage _VIN .

Alternatively, instead of Fourier transformer 136, a real-time analyzer may be used.

(Modification 4)
Although the DC/AC converter 110 is composed of a single-phase inverter in the embodiment, it may be composed of an H-bridge circuit. The H-bridge circuit may generate complementary AC voltages _{VAC_P} and _{VAC_N} , and the amplifier 120 may amplify the difference between the complementary AC voltages _{VAC_P} and _{VAC_N} .

(Application)
The application of voltage measuring apparatus 100 according to the embodiment is not particularly limited, but it can be used, for example, for testing semiconductor devices, for example, for measuring various characteristics of operational amplifiers. In this case, the voltage measuring device 100 is designed with the highest priority given to accuracy over cost and productivity, and therefore the voltage measuring device 100 may be configured with discrete components.

19A and 19B are diagrams for explaining the application of the voltage measurement circuit 100. FIG. The voltage measuring apparatus 100 can be incorporated in a sensor-equipped device such as an IoT (Internet of Things) device 300 and used as a circuit that captures minute voltage output from the sensor.

As shown in FIG. 19( a ), IoT device 300 includes sensor 302 , wireless device 304 and microcontroller 306 . In this case, part or all of the voltage measuring device 100 can be integrated on an IC chip and used as the front end circuit 400 between the sensor 302 and the microcontroller 306. FIG.

As shown in FIG. 19B, the microcontroller 306 may incorporate an A/D converter 308 . Therefore, the A/D converter 308 built into the microcontroller 306 may be used as the A/D converter 134, and the CPU (Central Processing Unit) 310 built into the microcontroller 306 may function as the Fourier transformer 136. . That is, the functions of the A/D converter 134 and the Fourier transformer 136 in the voltage measurement circuit 100 are implemented in the microcontroller 306, and the front-end circuit 400 includes the DC/AC converter 110, the amplifier 120, and the AC amplifier 132. may be integrated.

Although the present invention has been described using specific terms based on the embodiment, the embodiment only shows one aspect of the principle and application of the present invention, and the embodiment does not include the claims. Many variations and rearrangements are permissible without departing from the spirit of the invention as defined in its scope.

100 voltage measuring device P _IN input terminal 110 DC/AC converter SW1 first switch SW2 second switch 112 first driver 120 amplifier 122 operational amplifier 124 differential amplifier R ₁₁ first resistor R ₁₂ second resistor 130 detector C ₂ DC Block Capacitor 132 AC Amplifier 134 A/D Converter 136 Fourier Transformer 138 Adder 140 Dummy Circuit SW3 Third Switch SW4 Fourth Switch 142 Second Driver Rs Resistor 150 Filter 152 Detector

Claims (10)

an input terminal for receiving a DC input voltage;
a DC/AC converter that converts the input voltage into a rectangular wave voltage containing an AC component having an amplitude and a predetermined frequency corresponding to the input voltage;
an amplifier that amplifies the rectangular wave voltage ;
a detection unit that detects the voltage level of the input voltage based on the predetermined frequency component included in the square wave voltage after amplification;
with
The DC/AC converter is
a first switch and a second switch provided in series between the input terminal and ground;
a first driver that complementarily switches the first switch and the second switch according to the clock having the predetermined frequency;
including
A voltage measuring device , wherein a voltage at a connection node between the first switch and the second switch is the rectangular wave voltage . 2. The voltage measuring device according to claim 1 , wherein said DC/AC converter is thermally separated from said amplifier and said detector. A dummy circuit having the same configuration as the DC/AC converter and operating synchronously with the DC/AC converter,
3. The voltage measuring apparatus according to claim 1 , wherein said amplifier includes a differential amplifier having one input receiving said rectangular wave voltage and another input receiving an output of said dummy circuit. The dummy circuit is
a third switch and a fourth switch provided between the ground and the ground;
a second driver that complementarily switches the third switch and the fourth switch according to a clock;
4. The voltage measurement device of claim 3 , comprising: 5. The voltage measuring apparatus according to claim 3 , wherein said DC/AC converter and said dummy circuit are thermally separated from said amplifier and said detector. 6. The voltage measuring device according to any one of claims 3 to 5 , wherein a plurality of switches forming said DC/AC converter and said dummy circuit are connected to a common heat sink. The detection unit is
an A/D converter that converts the rectangular wave voltage into a digital signal;
a Fourier transformer for Fourier transforming the output waveform of the A/D converter;
and detecting the voltage level of the input voltage based on the predetermined frequency component of the spectrum obtained by the Fourier transformer. . The detection unit includes a filter for extracting the predetermined frequency component of the rectangular wave voltage , and detects the voltage level of the input voltage based on the amplitude of the signal that has passed through the filter. Item 7. The voltage measuring device according to any one of Items 1 to 6 . A plurality of sets of the input terminal, the DC/AC converter and the amplifier are provided,
9. The voltage measuring device according to claim 1, wherein said detecting section includes an adder that adds the output voltages of said amplifiers in said plurality of sets . A sensor-equipped device comprising the voltage measuring device according to any one of claims 1 to 9.

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