JP2023059144A - Current supply device and magnetic sensor - Google Patents

Abstract

To provide a current supply device or the like that supplies a DC superimposed period waveform current in which a DC component is superimposed on an AC component, and can remarkably reduce distortion of the DC superimposed period waveform current.SOLUTION: A current supply device includes: a transistor 3 to which a rectangular wave generated by a rectangular wave generating circuit 6 is input; a first coil L1 connected to a rear stage side of the transistor 3; an LC resonance circuit 5 arranged between the first coil L1 and ground at a rear stage side of the first coil L1 and to which a capacitor C1 and a second coil L2 are connected in parallel; a first terminal 9 for connecting to a rear stage side of the second coil L2 in the LC resonance circuit 5; and a second terminal 10 for connecting to ground. A DC superimposed period waveform current which is a current in which an AC component and a DC component are superimposed is supplied to a load resistor R2 connected between the first terminal 9 and the second terminal 10.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current supply device that supplies current, and more particularly to a current supply device that supplies current in which a DC component is superimposed on an AC component (hereinafter referred to as a DC superimposed periodic waveform current).

Japanese Unexamined Patent Application Publication No. 2002-200010 discloses a technique related to a fundamental wave type orthogonal fluxgate. The technique disclosed in Patent Document 1 includes a sensor head formed by winding a detection coil around a magnetic core, a current supply unit for superimposing and supplying an alternating current for excitation and a direct current for bias to the magnetic core, and at least It comprises a first switch for switching the polarity of a DC bias current, and a detection circuit connected to the detection coil for detecting the magnetic field measured by the sensor head using a feedback current.

FIG. 16 is a diagram showing a circuit configuration of a current supply unit used in Patent Document 1. As shown in FIG. The current supply unit shown in FIG. 16 is arranged between a transistor to which a rectangular wave generated by the rectangular wave generating means is input, and between the transistor and the ground on the subsequent stage side of the transistor. an LC resonant circuit to be connected, a first terminal for connection to the rear stage side of the coil in the LC resonant circuit, and a second terminal for connection to the ground, and between the first terminal and the second terminal An alternating current superimposed with a direct current is supplied to the magnetic core 15 to be connected.

JP 2019-211450 A

Here, FIG. 17 is a diagram showing the waveforms of the collector current supplied by the current supply unit having the circuit of FIG. be. As shown in FIG. 17, the waveform of the collector current includes sharp changes that are almost vertical. This is because a capacitor is connected between the emitter and the ground, and the current supply part according to Patent Document 1 causes electromagnetic interference to other parts and circuits on the circuit board due to such abrupt changes. There is a problem that there is a possibility.

Further, FIG. 18 shows the ratio (Iac_amp/Idc) between the distortion factor of the current supplied by the current supply unit described in Patent Document 1 and the magnitude of the DC component (Idc) and the magnitude of the AC amplitude (Iac_amp). It is a diagram. FIG. 18A shows the distortion factor with respect to the ratio (fr/fd) between the repetition frequency (transistor driving frequency) (fd) of the rectangular wave output from the rectangular wave generating means and the resonance frequency (fr) of the LC resonance circuit. FIG. 18B shows (Iac_amp/Idc) with respect to (fr/fd). The distortion factor in FIG. 18(A) is obtained by the ratio of the square root of the sum of squares of the effective values of all harmonic components other than the fundamental wave contained in the waveform to the effective value of the fundamental wave, and (fr/fd) is 1. It has a relatively large value of 4% to 7.5% in the following range. Also, the value of (Iac_amp/Idc) in FIG. 18(B) exceeds 1 when (fr/fd) is about 0.8 or more, that is, it is suitable for a fundamental wave type orthogonal flux gate as shown in Patent Document 1. In order to satisfy the condition of a unipolar DC superimposed periodic waveform current by making the DC component larger in amplitude than the AC component, it is necessary to set (fr/fd) to less than 0.8, preferably less than 0.5. In other words, it is necessary to adjust the rectangular wave driving frequency (fd) to about twice the resonance frequency (fr). However, the waveform distortion rate of the AC component is still as large as about 4%, so if fd is increased too much to reduce this distortion rate, the fundamental wave component will become smaller, and when considering the drive of the magnetic sensor, (Iac_amp/Idc) becomes small, making it unsuitable for a sensor.

The present invention provides a current supply device capable of supplying a DC superimposed periodic waveform current in which a DC component is superimposed on an AC component, and remarkably reducing the distortion of the AC component of the DC superimposed periodic waveform current, and the current supply. A magnetic sensor using the device is provided.

A current supply device according to the present invention includes: a switching element to which a rectangular wave generated by a rectangular wave generating means is input; a first coil connected to the rear stage side of the switching element; an LC resonant circuit disposed between the first coil and the ground on the side thereof and in which a capacitor and a second coil are connected in parallel; and a second terminal for connecting to the ground, and a current in which an AC component and a DC component are superimposed on a load connected between the first terminal and the second terminal It supplies a DC superimposed periodic waveform current.

As described above, in the AC signal generating device according to the present invention, the switching element to which the rectangular wave generated by the rectangular wave generating means is input, the first coil connected to the downstream side of the switching element, the an LC resonant circuit disposed between the first coil and the ground on the subsequent stage side of the first coil and having a capacitor and a second coil connected in parallel; and the second coil in the LC resonant circuit. and a second terminal for connection to the ground. It is possible to supply a DC superimposed periodic waveform current in which a component and a DC component are superimposed, and it is possible to supply a DC superimposed periodic waveform current with little distortion by minimizing switching noise. .

The current supply device according to the present invention may optionally include rectangular wave frequency control means for controlling the frequency of the rectangular wave generated by the rectangular wave generating means.

As described above, since the current supply device according to the present invention includes the rectangular wave frequency control means for controlling the frequency of the rectangular wave, the ratio between the amplitude of the AC component and the magnitude of the DC component is determined according to the frequency of the rectangular wave. can be freely controlled, and it is possible to set appropriate parameters according to the environment of use.

In the current supply device according to the present invention, if necessary, the rectangular wave frequency control means controls the ratio (fd/fr) between the frequency (fd) of the rectangular wave and the resonance frequency (fr) of the LC resonance circuit. It is adjusted to 0.7≦(fd/fr)≦1.4.

Thus, in the current supply device according to the present invention, the ratio (fd/fr) between the frequency (fd) of the rectangular wave and the resonance frequency (fr) of the LC resonance circuit is 0.7≦(fd/fr)≦1.4. , the distortion factor of the AC component can be reduced to about 1% or less from the simulation results described later, and a DC superimposed periodic waveform current with little distortion can be generated.

In the current supply device according to the present invention, the inductance of the first coil is larger than the inductance of the second coil as required.

As described above, in the current supply device according to the present invention, by making the inductance of the first coil larger than the inductance of the second coil, the change in the waveform of the current flowing through the collector is reduced, and the current supply to other circuits is reduced. This has the effect of suppressing electromagnetic noise and the like.

The current supply device according to the present invention may optionally include a diode having a cathode terminal connected to a node between the switching element and the first coil and an anode terminal connected to the ground.

As described above, the current supply device according to the present invention includes a diode whose cathode terminal is connected to the node between the switching element and the first coil and whose anode terminal is connected to the ground. can be significantly reduced.

A magnetic sensor according to the present invention comprises, if necessary, the current supply device, and a fundamental wave type orthogonal fluxgate to which a magnetic core constituting a sensor head is connected between a first terminal and a second terminal. be.

Thus, since the magnetic sensor according to the present invention includes the current supply device and the fundamental wave type orthogonal fluxgate to which the magnetic core constituting the sensor head is connected between the first terminal and the second terminal, There is an effect that sensing using an exciting current, which has an extremely excellent feature as a drive source for a fundamental wave type orthogonal fluxgate, can be realized.

1 is a diagram showing a circuit configuration of a current supply device according to a first embodiment; FIG. FIG. 2 is a diagram showing an AC equivalent circuit of the circuit in FIG. 1 when fd is close to fr and the base side circuit is viewed from the emitter terminal of the transistor; 3 is a phasor diagram of current and voltage in the circuit of FIG. 2; FIG. FIG. 10 is a diagram showing the results of calculations (β=120) for the relationship between the AC component Iac of IL2 and fd/fr when L1 is varied with respect to a predetermined L2; FIG. 10 is a diagram (β=240) showing calculation results of the relationship between the AC component Iac of IL2 and fd/fr when L1 is varied with respect to a predetermined L2; FIG. 5 is a diagram showing results of calculating a distortion factor of an AC component in the current supply device according to the first embodiment; FIG. 2 is a diagram showing an example of the result of calculating the amplitude of the current flowing through the collector in the circuit of FIG. 1; FIG. 4 is a diagram showing waveforms of a current flowing through a load resistor in the current supply device according to the first embodiment; FIG. 4 is a diagram showing the waveform of the collector current in the current supply device according to the first embodiment; FIG. 7 is a diagram showing the circuit configuration of a current supply device according to a second embodiment; FIG. 10 is a diagram showing results of simulating current waveforms of respective parts in the current supply device according to the second embodiment; FIG. 12 is a diagram showing a current waveform flowing through a load resistor in the simulation of FIG. 11; FIG. 2 is a diagram showing the results of a simulation performed with the circuit configuration of FIG. 1; FIG. 11 is a diagram showing switching loss waveforms in each of the circuit configuration of FIG. 1 and the circuit configuration of FIG. 10; 10. It is a figure which shows the time change of the power supply from a DC power supply in each of the circuit structure of FIG. 1, and the circuit structure of FIG. 1 is a diagram showing a circuit configuration of a current supply unit used in Patent Document 1; FIG. FIG. 11 is a diagram showing waveforms of a collector current supplied by a current supply unit having the circuit of FIG. 10 described in Patent Document 1 and a current flowing through a load resistor; 4 is a diagram showing the distortion factor of the current supplied by the current supply unit described in Patent Document 1 and the ratio between the magnitude of the DC component and the magnitude of the AC amplitude. FIG.

Embodiments of the present invention will be described below. Also, the same reference numerals are given to the same elements throughout the present embodiment.

(First embodiment of the present invention)
A current supply device according to this embodiment will be described with reference to FIGS. 1 to 9. FIG. The current supply device according to the present embodiment supplies a DC superimposed periodic waveform current, which is a current in which a DC component and an AC component are superimposed. It can be used as an exciting current for , and exhibits particularly excellent characteristics in this case.

First, the circuit configuration and operation of the current supply device according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is a diagram showing the circuit configuration of the current supply device according to this embodiment. The current supply device 1 includes a DC power supply 2, a transistor 3 as a switching element to which the DC power supply 2 and the collector terminal are connected in the subsequent stage of the DC power supply 2, and an inductor connected to the emitter terminal of the transistor 3. A rectangular wave is supplied to the first coil L1 (including the parasitic resistance R1) of the first coil L1 (including the parasitic resistance R1), the LC resonance circuit 5 connected in series with the ground after the first coil L1, and the base of the transistor 3. The LC resonance circuit 5 has a capacitor C1 as a capacitor and a second coil L2 as an inductor connected in parallel. It has a first terminal 9 for serial connection to the coil L2 of the coil L2 and a second terminal 10 for connection to the ground. For example, a load resistor R2 (including the loss resistance of the second coil L2) is connected to the first terminal 9 and the second terminal 10 as a load. , and a DC superimposed periodic waveform current in which a DC component and an AC component are superimposed is supplied to the load resistor R2. As the load, in addition to the resistive element, an inductance or a capacitor may be attached as long as it is a two-terminal circuit and is resistive as a whole.

The base of the transistor 3 is driven by a rectangular wave of amplitude voltage Vp, the high level being Vp[V] and the low level being 0[V]. Base resistance is Rb. Parasitic resistance R1 is a parasitic resistance resulting from winding resistance loss and magnetic core loss of the first coil L1, and represents (accumulated energy of inductor)/(loss energy) in one cycle of driving frequency f of rectangular wave generating circuit 6. Using the Q value, it can be expressed as R1=ωL1/Q1. where ω=2πf and Q1 is the Q value of the first coil 4;

The capacitor C1, the two first coils L1 and the second coil L2 form a resonant circuit, in which case the first coil L1 and the second coil L2 form a parallel circuit with respect to the capacitor C1. When the parallel inductance of the first coil L1 and the second coil L2 is Lp (1/Lp=1/L1+1/L2), the resonance frequency fr of the LC resonance circuit 5 is

is given by When the drive frequency fd of the rectangular wave generating circuit 6 is set near the resonance frequency fr, the circuit of FIG. 1 operates in a resonance state or a state close thereto. In order to explain this resonance operation, FIG. 2 shows an equivalent circuit of the circuit of FIG. 1 as viewed from the emitter terminal of the transistor 3 on the base side. β is the current amplification factor of the transistor 3; The amplitude of the fundamental wave component contained in the rectangle with the duty ratio 0.5 of the peak value Vp of the square wave generated by the square wave generating circuit 6 is 2Vp/π, but the amplitude of V1 is the voltage drop VBE between the base and emitter (approximately 0.7[V]), √2V1=2(Vp-VBE)/π. If R2 is set to ωL2/R2=Q2 and expressed using L2 and Q2, the AC amplitude component of IL2 is given by the following equation. j is the imaginary unit.

FIG. 3 is a phasor diagram of current and voltage in the circuit of FIG. From the phasor diagram of FIG. 3, at resonance, IC1 and IL2 are nearly out of phase (the angle formed by the upward arrow of IC1 and the downward arrow of IL2 is nearly π), and IL1 and IC1 are nearly parallel. As a result, the angle between VC1 and VL1+VR1 approaches π, and the length of VC1 and VL1+VR1 increases with respect to a given V1. In other words, the amplitude of voltage and current increases under resonance conditions. Also, if L2 is fixed and L1 is made several times larger than L2 while operating fd near the resonance condition (that is, if C1 is made small appropriately), the resonant current flowing out of capacitor C1 will be split between L1 and L2. However, the ratio of IL1 and IL2 becomes 1/L1:1/L2, and the resonance current component contained in IL1 becomes small. As a result, the current iL1 in FIG. 1 is mostly composed of a DC component, and a current with a relatively small AC component flows. This has an important effect on the utilization of the circuit of FIG. That is, while AC and DC components with small distortion are supplied to the load resistor R2, most of the collector current of the transistor 3 is composed of DC components, and the current supplied from the DC power supply 2 to the transistor 3 is inductive to the surroundings. Creates a practically excellent action that does not generate magnetic noise.

Regarding the DC current component, in the equivalent circuit of Fig. 2, V1 is Vp-VBE, C1 is open, L1 and L2 are short-circuited, ωL1/Q1 is replaced by the DC resistance of L1 (winding resistance to DC) R1dc, If R2 is represented by the sum R2dc of the DC resistance of L2 and the load resistance, it is given by the following equation. Here, D is the duty ratio of the rectangular wave, which is obtained by dividing the on period (Ton) of the transistor 3 by one cycle period (T). The direct current is in principle irrelevant to the repetition frequency f of the square wave.

Next, the control of the driving frequency fd of the rectangular wave generating circuit and the relationship between the inductance L1 of the first coil L1 and the inductance L2 of the second coil L2 will be described with reference to FIGS. 4 to 6. FIG. FIG. 4 and FIG. 5 show the results of calculations of the relationship between the AC component Iac of IL2 and fd/fr when L1 (assuming the E6 series) is varied with respect to a predetermined L2. 4, the grounded emitter current amplification factor β of the transistor 3 is 120, and β=240 in FIG. However, in this series of calculations, Q1=30, Q2=9, duty ratio=0.5, and k=L1/L2. 4 and 5, the magnitude of the current is represented by the ratio of the magnitude of the DC component (broken line) to each k.

Here, in the excitation current supplied to the magnetic core in the fundamental wave type quadrature fluxgate sensor, it is preferable that the amplitude of the DC component is larger than the amplitude of the AC component. When the amplitude of the AC component becomes larger than that of the DC component, there is a time when the direction of the current becomes negative (in the opposite direction), and during that time the direction of the magnetic field becomes the opposite polarity, causing the domain wall to move, resulting in Barkhausen noise. It is from. From the simulation results in FIGS. 4 and 5, in the very vicinity of fd/fr=1, where the inductances of L1 and L2 are close (where the value of k is close to 1), the amplitude of the AC component becomes larger than that of the DC component. ing.

FIG. 6 is a graph showing the result of calculation of the distortion factor of the AC component of the DC superimposed periodic waveform current in the current supply device according to this embodiment. It is calculated with Rb=1 kΩ, β=120, and k=2.13. From the simulation results in Fig. 6, the distortion is the smallest when the drive frequency fd and the resonance frequency fr are equal, and in the range of 0.7<fd/fr<1.4, a very clean sine wave with a distortion rate of 1% or less is generated. It can be seen that

This point will be compared with the case of the conventional circuit shown in FIG. In the conventional circuit, fd/fr>2 is preferable from the results shown in FIG. 12, and the distortion factor at this time is as large as about 5%. On the other hand, the current supply device according to the present embodiment has a distortion factor of about 1% or less in the range of 0.7<fd/fr<1.4 from the results of FIG. 6, which is extremely superior to the conventional circuit. It becomes possible to obtain a DC superimposed periodic waveform current. Also, the distortion is the smallest at fd/fr=1, but as shown in the results of FIGS. 4 and 5, the amplitude of the AC component may become larger than that of the DC component. Even in such a case, the distortion is minimized by adjusting the inductance of each of the first coil L1 and the second coil L2, and the DC superimposition in which the DC component is made larger than the amplitude of the AC component is performed. It is possible to generate a periodic waveform current.

Next, adjustment of the inductances of the first coil L1 and the second coil L2 will be described with reference to FIGS. 7 to 9. FIG. When the AC component is generated, if the collector current fluctuates sharply as the transistor 3 is driven, there arises a problem that electromagnetic noise is given to other parts of the circuit. As shown in FIG. 11, when the conventional circuit is used, the collector current exhibits very steep rising and falling changes, and the influence of electromagnetic noise becomes large. In this embodiment, by adjusting the inductances of the first coil L1 and the second coil L2, it is possible to minimize the influence of noise caused by the current flowing through the collector.

FIG. 7 shows an example of the result of calculating the amplitude of the current flowing through the collector in the circuit of FIG. In FIG. 7, the magnitude of the current is represented by the ratio to the magnitude of the DC component (broken line) for each k. When k becomes smaller, that is, when L1 becomes smaller in the circuit of Fig. 1, the direct current flowing through the collector becomes discontinuous. Double the ingredients. The overall relationship is similar when the grounded emitter current amplification factor β=240, but when k=0.47 and fd=fr, the peak value of the current flowing through the collector reaches about 2.5 times the DC component. From these results, it can be said that when fd=fr or fd is very close to fr, setting L1 to be larger than L2 can suppress the AC component contained in the collector current. When the amplitude of the AC component contained in the collector current becomes smaller than Idc, a continuously flowing current component appears. As can be seen from FIG. 7, for any of k>1, k<1, and k=1, fd/fr is kept away from 1 within tolerance (for example, fd/fr=0.8 to 0.7 or fd/ fr = 1.2 to 1.4).

8 and 9 show the simulation results for IL2 and collector current with K=2.13 and fd/fr=0.9. FIG. 8 shows IL2, that is, the waveform of the current flowing through the load resistor, and FIG. 9 shows the result of IL1, that is, the waveform of the collector current. Regarding FIG. 8, as is clear from comparison with the waveform of the load current in FIG. 11, the DC superimposed periodic waveform current has a waveform with very little distortion. Also, from the curve of k=2.13 in FIG. 7, it can be read that the amplitude of the AC component contained in the collector current is small when fd/fr is close to 0.9. becomes. The DC component is a value around the center of the amplitude of the AC component, and is approximately 0.08 [A] in both FIGS. 8 and 9, which is almost the same. there is This indicates that the fluctuating component of the current flowing through the collector, which causes electromagnetic noise, is suppressed as compared with the case of FIG.

From the above, in the current supply device according to the present embodiment, as shown in FIG. It is possible to obtain a clean DC superimposed periodic waveform current with little distortion. 4 and 5, by appropriately adjusting the driving frequency fd, the ratio of the AC component/DC component is adjusted while the DC component is made larger than the amplitude of the AC component. It becomes possible to generate an optimum current for the excitation current.

In addition to the control of the drive frequency fd, or without depending on the control of fd, the inductances of the first coil L1 and the second coil L2 can be adjusted as shown in FIGS. It is possible to generate an optimum current for the excitation current of the fundamental wave type quadrature fluxgate by increasing the amplitude of the DC component relative to the amplitude of the AC component.

Furthermore, as shown in FIGS. 7 to 9, if L1 is made larger than L2, the AC component contained in the collector current can be suppressed. It is possible to suppress the influence of noise caused by the flowing current.

As described above, the current generated by the current supply device according to this embodiment can be used as the excitation current for the magnetic sensor. The configuration of the magnetic sensor is described in, for example, Patent Document 1, so a detailed description is omitted. When applying a DC superimposed periodic waveform current), by using a magnetic core as the load resistor R2 in the circuit of FIG.

In addition, by inserting a resistor of about 10 Ω on the collector side (between the DC power supply 2 and the transistor 3) of the circuit shown in Fig. 1, the influence of the variation in the current amplification factor of the transistor 3 is suppressed and excessive current is suppressed. You may make it With such a configuration, it is possible to distribute part of the collector loss of the transistor 3 to the inserted resistor secondarily. When K=L1/L2 is less than 1, the periodic variation of the collector current is large, so this secondary effect appears prominently. For example, inserting 10 Ω at k=0.7 will result in a current value of 88%, but 40% of the collector loss can be transferred to the resistor. When there is a risk that the switching element will generate excessive heat, it is possible to alleviate this problem by dispersing the heat generation by inserting a resistor with an appropriate resistance value.

(Second embodiment of the present invention)
A current supply device according to this embodiment will be described with reference to FIGS. 10 to 15. FIG. In the current supply device according to the present embodiment, in the current supply device according to the first embodiment, when the base drive voltage of the transistor is at low level, the transistor is used as a cutoff region, thereby greatly reducing the loss. is. In this embodiment, the same description as that of the first embodiment is omitted.

FIG. 10 is a diagram showing the circuit configuration of the current supply device according to this embodiment. A difference from the case of FIG. 1 in the first embodiment is that a diode 20 is provided between the emitter terminal of the transistor 3 and the ground. The diode 20 has a cathode terminal connected to a node between the emitter terminal of the transistor 3 and the first coil L1, and an anode terminal connected to the ground. The diode 20 allows current to flow through the diode 20 to the first coil L1 when the potential between the emitter terminal of the transistor 3 and the node of the first coil L1 becomes negative.

When the base voltage of the transistor 3 is high level (≈Vp[V]) and the transistor 3 is in the ON state, current is supplied to the first coil L1, but the base voltage is low level (≈0[V]). If a current is flowing through the first coil L1 at the timing when the transistor 3 is about to turn off, the potential at the upper end of the first coil L1 is set to the potential at the lower end so that the current does not become discontinuous. Compared to the potential, it makes a rapid negative transition and tries to maintain the current. In this embodiment, this rapid potential change turns on the diode 20 to maintain the continuity of the current. On the other hand, in the case of the current supply device according to the first embodiment, since the transistor 3 conducts in the active region during this period, problems such as power loss and heat generation may occur depending on the magnitude of the required excitation power. There is Therefore, in the present embodiment, by adopting the configuration including the diode 20 described above, even if the potential at the node between the emitter terminal of the transistor 3 and the first coil L1 becomes negative, the voltage is generated through the diode 20. Current can be supplied to the first coil L1, and loss can be greatly reduced.

In the following, a Schottky diode having a small forward potential drop was used as the diode 20 to simulate the current waveform of each part. The simulation conditions are fd/fr=0.92, k=L1/L2=2.13, R1=2.8kΩ, β=240, the Q value of inductor L1 is Q1=30, and the Q value of inductor L2 is Q2 = 9, square wave for base drive with duty ratio = 0.5. where Q1 = ωL1/r and r is the equivalent series resistance representing the losses in inductor L1 at angular frequency ω. Also, Q2=ωL2/R2. The loss of L2 is included in R2. The results of this simulation are shown in FIG. 11A shows the collector current waveform of the transistor 3, FIG. 11B shows the current waveform flowing through the diode 20, and FIG. 11C shows the current waveform flowing through the first coil L1. Note that 0 on the time axis indicates the timing at which data extraction is started, and does not indicate the timing at which the simulation is started.

The conduction period of the collector current of the transistor 3 is the period during which the base current is at high level, and the conduction period of the diode 20 is the period during which the base current is at low level. The current flowing through the first coil L1 is the sum of the currents in the respective conduction periods, which is obtained by summing the current waveforms of FIGS. ) can be visually confirmed.

FIG. 12 shows the current waveform flowing through the load resistor R2 in the simulation of FIG. The average value (DC level) is greater than the amplitude of the AC component and the waveform is unipolar. That is, by connecting a sensor head of a fundamental-wave quadrature fluxgate having a resistance value approximately equal to that of the load resistor R2, the excitation current can be optimized for the fundamental-wave quadrature fluxgate.

Next, power loss was compared between the circuit configuration shown in FIG. 1 in the first embodiment and the circuit configuration shown in FIG. 10 in the present embodiment. In order to obtain substantially the same DC superimposed periodic waveform current, a simulation was performed with R1=1000Ω and fd/fr=0.95 in the circuit of FIG. The results are shown in FIG. As shown in FIG. 13, it can be seen that in the circuit configuration of FIG. 1, a current waveform substantially similar to the current waveform of FIG. 12 according to this embodiment is generated.

FIG. 14 shows switching loss waveforms of the transistor 3 in each of the circuit configurations of FIG. 1 and FIG. 10 under such conditions. 14A shows the switching loss waveform of the transistor 3 in the circuit configuration of FIG. 1, and FIG. 14B shows the switching loss waveform of the transistor 3 in the circuit configuration of FIG. In the case of FIG. 14A, the average switching loss is 0.347 (W), and a large loss occurs when the base driving voltage of the transistor 3 is at low level. This is due to current conduction in the active region, as described above. When the base driving voltage of the transistor 3 is at a high level, the conduction loss is the conduction loss when the transistor 3 is saturated.

On the other hand, in FIG. 14B, the average switching loss is 0.132 (W), and when the base driving voltage of the transistor 3 is at low level, the transistor 3 is in the blocking region and no loss occurs. When the base drive voltage of the transistor 3 is at a high level, the conduction loss consists only when the transistor 3 is saturated. As a result, as is clear from FIG. 14, the circuit configuration of this embodiment can significantly reduce loss.

Next, the power supplied from the DC power supply 2 will be compared. 15A and 15B are graphs showing temporal changes in power supplied from the DC power supply 2. FIG. 15A shows the case of the circuit configuration of FIG. 1, and FIG. 15B shows the case of the circuit configuration of FIG. . In FIG. 15(A), the average power supplied from the DC power supply 2 is 0.478 (W), and in FIG. 15(B), the average power supplied from the DC power supply 2 is 0.276 (W). As is clear from these comparisons, the circuit configuration of FIG. 10 according to this embodiment is expected to significantly reduce the power supply.

Thus, in the current supply device according to the present embodiment, the switching loss due to the transistor 3 can be greatly reduced, and DC superimposition equivalent to the power supply of about 58% of the circuit configuration in the first embodiment can be achieved. It is possible to generate a periodic waveform current.

1 Current Supply Device 2 DC Power Supply 3 Transistor 5 LC Resonant Circuit 6 Rectangular Wave Generator Circuit 9 First Terminal 10 Second Terminal 20 Diode C1 Capacitor L1 First Coil L2 Second Coil R1, R2 Resistor

Claims (6)

a switching element to which the rectangular wave generated by the rectangular wave generating means is input;
a first coil connected to the downstream side of the switching element;
an LC resonance circuit disposed between the first coil and the ground on the rear stage side of the first coil and having a capacitor and a second coil connected in parallel;
a first terminal for connection to the rear stage side of the second coil in the LC resonance circuit;
a second terminal for connecting to the ground;
A current supply device, characterized in that a DC superimposed periodic waveform current, which is a current in which an AC component and a DC component are superimposed, is supplied to a load connected between the first terminal and the second terminal. The current supply device according to claim 1,
A current supply device comprising rectangular wave frequency control means for controlling the frequency of the rectangular wave generated by the rectangular wave generating means. In the current supply device according to claim 2,
The rectangular wave frequency control means adjusts the ratio (fd/fr) between the frequency (fd) of the rectangular wave and the resonant frequency (fr) of the LC resonant circuit to 0.7≦(fd/fr)≦1.4. feeding device. The current supply device according to any one of claims 1 to 3,
A current supply device in which the inductance of the first coil is greater than the inductance of the second coil. The current supply device according to any one of claims 1 to 4,
A current supply device comprising a diode having a cathode terminal connected to a node between the switching element and the first coil and having an anode terminal connected to ground. a current supply device according to any one of claims 1 to 5;
A magnetic sensor comprising a fundamental wave type orthogonal fluxgate to which a magnetic core constituting a sensor head is connected between the first terminal and the second terminal.

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