JP6519081B2 - Medical magnetic pulse generator having a rapid adjustment circuit for charging voltage - Google Patents

Description

The present invention relates to a medical magnetic pulse generator for causing sustained large contraction in muscles by stimulating peripheral nerves with a series of magnetic pulses.

Pulse current is used in a wide range of industries, and many products ranging from industrial high voltage pulses such as electrostatic precipitators, plasma generators and lasers, to medical low-frequency therapeutic devices that move muscles with weak pulse currents Is put to practical use. Most of the pulse current for industrial equipment is characterized by high voltage (3 to 10 kV), small current (several mA to several A), high frequency (30 to 100 kHz), and narrow pulse width (1 to 10 μs). The reason is that the higher the voltage and the narrower the pulse width, the higher energy can be generated instantaneously.

A number of patent applications have been filed for pulse power supplies for the purpose of generating such sharp high voltage pulses. Patent Document 1 discloses a “pulse compression technique” in which a resonant circuit of a capacitor and a coil is connected in multiple stages in series for the purpose of generating a high voltage ultrashort pulse. The coil used in the pulse compression circuit is a saturable reactor in which the core is saturated when a current of a certain level or more flows, and the function of the coil is both LC resonance and switch element in which the coil current rapidly increases due to magnetic saturation. doing.

Patent Document 2 discloses a method of stabilizing a pulse voltage. For this purpose, a charge / discharge capacitor and a plurality of inductors (coils) are connected in series, and each inductor constitutes an LC resonant circuit consisting of individual charge / discharge capacitors , a power supply and a switch, and the timing of those multiple resonance circuits. Is characterized in that the pulse voltage is stabilized by shifting. The coil of the present invention is not a saturable reactor, and there is no problem of core saturation since the resonance frequency is high and an air cored coil is used.

There is a medical magnetic pulse generator as one of the devices using magnetic pulses for medical applications. This is a method of stimulating the nerve with the induced current generated by the magnetic pulse, which has the advantage that the electrode does not have to be applied to the skin. In magnetic stimulation, a pulse current with a voltage of about 1400 V, a current of about 2000 A, and a pulse width of about 0.2 ms is instantaneously applied to the magnetic stimulation coil to generate a strong magnetic field and stimulate nerves with induced current generated in the living body by the magnetic field. . The electrical energy of one pulse in this case is generally about 100 joules. On the other hand, in the case of the above-mentioned industrial pulse power supply, the voltage is 10 kV, the current is 100 mA, the pulse width is about 1 μs, the electrical energy per pulse is about several hundredths of a joule, and more than the magnetic stimulation pulse. Very small.

Patent Document 3 discloses a medical magnetic pulse generator used for treatment of urinary incontinence. Since the present invention uses repeated magnetic pulses, the charge and discharge capacitor needs to repeat rapid charge and discharge. The description of the electric circuit described in the present invention is limited to the contents that the power supply voltage is 100 to 3 kV, the capacity of the charge / discharge capacitor is 300 μF, and the prevention of inrush current is performed by the protection resistor. There is no particular mention of problems such as speeding up of the charge voltage control of the charge / discharge capacitor accompanying the above.

Patent Document 4 discloses the basic circuit of the medical magnetic pulse generator developed by us previously and the characteristic value of the circuit component used therein. In the present invention, by setting the characteristic values of the parts to be used to appropriate values, significant downsizing and power saving of the device and rapid charge and discharge are possible, but the charge voltage is controlled to an arbitrary value. There was no mention of the means.

Unexamined-Japanese-Patent No. 2010-200446 Japanese Patent Application Publication No. 2003-9548 JP-A-9-276418 JP 2015-107176

In order to emit magnetic pulses in a short cycle and at a stable intensity, rapid and accurate charging of the charge / discharge capacitor is required. As one of the methods, a switching semiconductor element for charging is disposed between a DC power supply and a charging / discharging capacitor , and during charging, the charging switching semiconductor element is closed while the charging voltage of the charging / discharging capacitor is fed back. There is a method to stop charging at the moment the set voltage is exceeded. According to this method, it is possible to rapidly charge the charge / discharge capacitor to an arbitrary voltage. However, since a relatively large charging current flows for rapid charging, when the charging switching semiconductor device is opened at the time of stopping charging, a large counter electromotive force is generated at both ends of the device, and the device is broken. There is a problem of being done.

Further, as a problem unique to a medical magnetic pulse generator using such a charge / discharge capacitor, it is easy to raise the charge voltage, but there is a problem that there is no means for immediately lowering the charge voltage when it is desired. In general, when the charge voltage is lowered, charges must flow until the charge voltage is reduced to the target charge voltage after the charge flows to the voltage dividing resistor for monitoring the charge voltage. The problem is that it takes time for

In view of the above-mentioned subject, the present invention solved the above-mentioned subject using the following art. The invention according to claim 1 (FIG. 1, FIG. 2) is
A pulse coil 10 for magnetic therapy to generate an eddy current in the target site 12, a charge / discharge capacitor 9, and an excitation switching semiconductor element 11 for supplying a discharge current from the charge / discharge capacitor 9 to the pulse coil 10 in series in a ring. Connected discharge circuit section C,
A charging switching circuit portion A comprising a charging switching semiconductor element 3 and a CR element (4 + 5) connected in parallel to a contact of the charging switching semiconductor element 3;
A discharge switching circuit part B comprising a discharge switching semiconductor element 6, a discharge resistor 7 connected in series to the discharge switching semiconductor element 6, a DC power supply part 1 for outputting a DC voltage or a full-wave rectified voltage;
And a comparator 14 for comparing the set voltage and the charge voltage of the charge / discharge capacitor 9 ;
The DC power supply unit 1 and the charge / discharge capacitor 9 are connected therebetween via the charge switching circuit unit A, and the discharge switching circuit unit B is connected in parallel to the charge / discharge capacitor 9,
The medical magnetic pulse generator is characterized in that the charging voltage of the charge / discharge capacitor 9 is adjusted by opening / closing the contact of the charging switching semiconductor element 3 triggered by the output of the comparator 14.

According to the first aspect of the present invention, it is possible to perform rapid charge voltage control of the charge / discharge capacitor with a simple and compact circuit.

The invention according to claim 2 is characterized in that the capacitance (C1) of the CR element (4 + 5), the withstand voltage (V1) of the charging switching semiconductor element 3 and the switching semiconductor element 3 for charging when there is no CR element (4 + 5). The back electromotive force (V2) generated at both ends of the capacitor, the total inductance (L) on the charging circuit, and the maximum value (I) of the charging current flowing through the charging switching semiconductor element 3 during charging satisfy “Equation 1” The medical magnetic pulse generator according to claim 1, characterized in that

According to the second aspect of the present invention, accurate charging control can be rapidly performed without burning the charging switching semiconductor element 3 and suppressing overshooting of the charging voltage at the time of charging stop.

According to the third aspect of the present invention, when the setting voltage is changed to a smaller direction, the discharging resistance 7 is charged and discharged by closing the discharging switching semiconductor element 6 for a predetermined discharging time. 9 has a function of releasing the charge in 9 to lower the charge voltage of the charge / discharge capacitor 9, the discharge time (t), the capacitance (C2) of the charge / discharge capacitor 9 , the total DC resistance (R2) of the discharge resistor 7 The voltage drop ratio (V / V0, where V is the setting voltage after changing the setting, and V0 is the setting voltage before changing the setting) satisfy the equation (2). a medical magnetic pulse generator for.

According to the invention of claim 3, it is possible to complete the charge voltage control in the descending direction, which generally requires time for control, in a short time by using a simple and compact discharge circuit.

A fourth aspect of the present invention is the magnetic pulse generator for medical use according to the third aspect, which prohibits the switching semiconductor element 11 for excitation from being closed during the discharge time. It is a pulse generator.

According to the invention of claim 4, in the charge voltage control according to claim 3, the excitation of the pulse coil in the state where the charge voltage is unstable is inhibited, so that the magnetic pulse by the charge voltage different from the set voltage is generated. It is possible to avoid an event that occurs.

According to the present invention, it is possible to continuously emit a magnetic pulse of any magnitude with a short period and a stable intensity without causing electrical damage to components in the circuit. Further, even when the charge voltage of the charge / discharge capacitor is lowered, it is possible to generate a magnetic pulse of a desired intensity in a short time with almost no loss of time. These functions make it possible to immediately feedback the patient's sensitivity to magnetic stimulation, the magnitude of the patient's exercise effort, etc. to control the magnetic stimulation intensity, and thus, the muscle's paralyzed muscle triggered by the patient's exercise effort. It is possible to apply a magnetic stimulation to the treatment to promote the remodeling of neural circuits.

1 shows a first embodiment of the circuit of the medical magnetic pulse generator of the present invention. The 2nd Example of the circuit of the medical magnetic pulse generator of this invention. Counter electromotive force when CR element is not used Example of back electromotive force when CR element is used (C1 = 5 μF, R1 = 10 Ω) Change of back electromotive force to change of C1, R1 (DC power supply output 120V, setting voltage 35V) Change of back electromotive force to change of C1 (DC power supply output 450 V, R1 fixed at 40 Ω) Change of back electromotive force to change of R1 (DC power supply output 450V, C1 = 5μF fixed) Change of overshoot amount to change of C1 (DC power supply output 450 V, R1 fixed at 40 Ω) Change of overshoot amount to change of R1 (DC power supply output 450V, C1 = 5μF fixed)

Hereinafter, the present invention will be described according to the illustrated embodiments. The present invention is mainly intended to rapidly and accurately perform adjustment of a charging voltage to a set voltage in a medical continuous magnetic pulse device without causing electrical damage to components in the circuit, and the inventors of the present invention conducted intensive studies Did. As a result, the charge switching semiconductor device 3 is controlled by controlling the charging switching semiconductor element 3 that opens and closes in synchronization with the output of the comparator 14 that first compares the charging voltage of the charging / discharging capacitor 9 with the set voltage 13. On the other hand, it became possible to charge the charge accurately. Second, by connecting the charging switching semiconductor element 3 in parallel with the CR element (4 + 5) whose value is appropriately set, the charging switching semiconductor element 3 is open at both ends when the charging switching semiconductor element 3 is opened while maintaining the setting accuracy of the charging voltage. It has become possible to suppress the back electromotive force that occurs. Thirdly, when the set voltage is lower than the charge voltage, the discharge switching semiconductor element 6 connected in parallel with the charge and discharge capacitor 9 is closed for an appropriate time, so that the charge and discharge capacitor 9 is Thus, it becomes possible to discharge unnecessary charges and rapidly control the voltage of the charge / discharge capacitor 9 to a desired voltage.

In the conventional medical magnetic pulse generator, the charge voltage of the charge / discharge capacitor 9 is set to an arbitrary voltage by adjusting the output of the high voltage DC power supply upstream of the circuit, or the charging current is set using a large DC resistance. It is common to adjust the voltage to an arbitrary voltage by charging the charge / discharge capacitor 9 slowly while suppressing and stopping the charging when the charging voltage exceeds the set voltage. However, in order to stabilize the voltage output of the high-voltage DC power supply at an arbitrary value and output a relatively large current, a complex control circuit and large parts corresponding to high power are required, resulting in a large-sized apparatus. There's a problem. Also, when a large DC resistance is used, the charging speed becomes slow, and it is not possible to generate magnetic pulses at a high frequency, and in addition, a large amount of Joule heat is generated during charging. Since it is necessary to use one with a large heat capacity, there is also a problem that the size of the apparatus also increases here.

Therefore, in the present invention, research has been conducted on a method for performing rapid and stable charge control using a small and simple switching circuit without using a variable output DC power supply or a large DC resistance. An example of a circuit diagram of a medical magnetic pulse generator using the present invention is shown in FIG.

The circuit shown in FIG. 1 includes a high voltage DC power supply unit 1, a charge switching circuit unit A, a discharge switching circuit unit B, and a discharge circuit unit C. The discharge circuit unit C is brought close to or in contact with a target site 12 of a patient. The pulse coil 10 for magnetic therapy which generates continuous pulse-like eddy current for a minute time in the muscle to stimulate its peripheral nerves, the charge and discharge capacitor 9, and the discharge current from the charge and discharge capacitor to the pulse coil 10 The excitation switching semiconductor element 11 is connected in a ring in series and configured. The excitation switching semiconductor element 11 is mainly composed of a thyristor, a MOSFET, an IGBT or the like, and in many cases, these semiconductor elements and a diode are connected in antiparallel. The high voltage DC power supply unit 1 for supplying a voltage to the discharge circuit unit C is a unit capable of outputting a smoothed DC voltage or a full-wave rectified voltage or a circuit equivalent thereto. The terminals at both ends are connected via the charge switching circuit section A. The charge switching circuit unit is constituted by the charge switching semiconductor 3 and the CR element (4 + 5) connected in parallel. The charging switching semiconductor 3 is configured of a thyristor, a MOSFET, an IGBT or the like. The CR element is an element in which a CR element capacitor 4 and a CR element resistor 5 are connected in series. Between the high voltage DC power supply unit 1 and the discharge circuit unit C, an inrush current buffer element 2 for suppressing inrush current is inserted as necessary. As the inrush current buffer element, an inductor or a resistor with appropriately adjusted parameters is used. Further, in parallel with the charge and discharge capacitor 9, the charge voltage monitoring means 8 and the discharge switching circuit unit B are connected. As the charging voltage monitoring means 8, a preamplifier or the like via a voltmeter or an attenuator can be used. The discharge switching circuit portion B is configured of a discharge switching semiconductor element 6 and a discharge resistor 7 connected in series to the discharge switching semiconductor element 6. The discharge switching semiconductor element 6 is configured of a thyristor, a MOSFET, an IGBT or the like. The charging voltage signal output from the charging voltage monitoring means 8 and the setting voltage signal output from the setting voltage input interface 13 are connected to the comparator 14 and the computing unit 15. The output of the comparator 14 is connected to the control terminal of the charging switching semiconductor element 3, and the output of the computing unit 15 is connected to the time control terminal of the timer 16. The output of the timer 16 is connected to the control terminal of the discharge switching semiconductor element 6. When the computing unit 15 has a timer function, the timer 16 can be omitted, and the computing unit 15 and the control terminal of the discharge switching semiconductor device 6 can be directly coupled.

Another example of a circuit diagram of a medical magnetic pulse generator using the present invention is shown in FIG. In the circuit, the connection between the high voltage DC power supply circuit 1 and the charge / discharge circuit C is made to a terminal on one side of the charge / discharge capacitor 9 and a terminal on one side of the pulse coil 10 not connected to the charge / discharge capacitor 9. The rest is the same as in FIG.

Hereinafter, details of the actual operation of the medical magnetic pulse generator using the present invention will be described. In the circuits shown in FIGS. 1 and 2, when the charge voltage signal is low, the set voltage signal output from the set voltage input interface 13 is compared with the charge voltage signal output from the charge voltage monitor 8 by the comparator 14. The close control signal is output from the comparator 14 to the charging switching semiconductor element 3, and the charging switching semiconductor element 3 is closed. When the charging switching semiconductor element 3 is closed, the high voltage DC power supply unit 1 and the discharge circuit unit C are connected, current flows into the charge and discharge capacitor 9 in the discharge circuit unit C, and both ends of the charge and discharge capacitor 9 The voltage starts to rise. As a result, the charge voltage signal outputted from the charge voltage monitor means 8 exceeds the set voltage signal outputted from the constant voltage input interface 13 and the closing control signal outputted from the comparator 14 is stopped, and the charging switching semiconductor element 3 returns to the open state. At that time, a back electromotive force is generated at both ends of the charging switching semiconductor element 3, but most of it is absorbed by the CR circuit (4 + 5), and the charging switching semiconductor element 3 is protected from breakdown due to the back electromotive force.

Here, the parameters of the CR element (4 + 5) in the charge switching circuit part A are very important. If C is too small, if R is too large, the CR element (4 + 5) can not sufficiently absorb the back electromotive force generated when the charge switching semiconductor device 3 is opened, and the charge switching semiconductor device 3 is damaged. Do. Conversely, if C is too large, if R is too small, part of the charge of capacitor 4 in the CR element flows into charge / discharge capacitor 9 when the charge switching semiconductor 3 is open, causing a voltage overshoot. There is a problem of Therefore, it is necessary to select an appropriate value as the capacitance (C1) of the capacitor in the CR element, and specifically, it is desirable that the value of the capacitance (C1) satisfy “Equation 1”. For the direct current resistance (R1) in the CR element, a resistance value that does not increase the back electromotive force excessively is determined and used in a range of several Ω to several hundreds Ω.

Contrary to the above, when the set voltage signal output from the set voltage input interface 13 is changed to become smaller and becomes lower than the charge voltage signal output from the charge voltage monitoring means 8, the arithmetic unit 15 The closing control signal is output from the timer 16 during the discharging time calculated by the above, and the discharging switching semiconductor element 6 is closed. As a result, the charge stored in the charge / discharge capacitor 9 is absorbed by the discharge resistor 7, and the charge voltage at both ends of the charge / discharge capacitor 9 decreases to a voltage equal to the set voltage. When the charging voltage undershoots, the comparator 14 operates, and the charging voltage converges to the value as the set voltage in the same operation as described above.

In the above operation, the discharge time t is calculated by the arithmetic unit 15 using “Equation 2”. "Equation 2" is a function using the capacitance (C2) of the charge / discharge capacitor, the total DC resistance (R2) of the discharge resistor 7, and the ratio (V / V0) of the set voltage V after change to the set voltage V0 before change is there. By charging the discharge time to “the number 2”, it is possible to discharge the charge in the charge / discharge capacitor 9 so as to reach the target charge voltage.

During this discharge time, since the voltage in the charge / discharge capacitor is different from the set voltage, the closing operation of the excitation switching semiconductor element 11 is prohibited during this time, and the pulse coil 10 is not energized. Is desirable.

After the charge / discharge capacitor 9 is charged according to the set voltage in the operation described above, closing the excitation switching semiconductor element 11 causes the charge in the charge / discharge capacitor 9 to be discharged to the pulse coil 10, and the pulse coil 10 A more pulsed magnetic field is generated. As a result, eddy currents are generated in the muscles of the affected area placed in contact with or in close proximity to the pulse coil 10 to stimulate peripheral nerves.

Next, the details of the present invention will be described based on examples. This example is intended to facilitate the understanding of the person skilled in the art. That is, it should be understood that the present invention is limited only by the technical concept described in the entire specification, and not limited by the present embodiment.

A circuit having the same configuration as that of FIG. 1 of the present invention was prepared without using a CR element (4 + 5). The high voltage DC power supply unit 1 was created by a high voltage transformer and a full wave rectification bridge, and a full wave rectified voltage was output from the output. As the inrush current buffer element 2, an inductor with a rated current of 30 A and an inductance of 10 mH was used. A MOSFET with a withstand voltage of 2 kV and a rated current of 20 A was used as the switching semiconductor element 3 for charging. The charge / discharge circuit C is constituted by a charge / discharge capacitor 9 having a capacitance of 120 μH, a pulse coil 10 having an inductance of 20 μH, and an excitation switching semiconductor element 11 composed of a thyristor and a diode connected in reverse parallel. A charge / discharge capacitor 9 is a charge / discharge monitor circuit 8 comprising an attenuator for dividing a charge voltage into 100: 1, a discharge / switching semiconductor element (C-MOS relay) 6 and a DC resistance 7 (DC resistance 200 Ω) Part B was connected in parallel. A volume resistor is used as the set voltage input interface 13. The set voltage signal output from the volume resistor and the charge voltage signal output from the charge voltage monitoring means are adjusted to an appropriate level by a preamplifier or the like, and then the comparator 14 and arithmetic unit Input to 15 (microcomputer). The output of the comparator 14 was input to the control terminal of the charging switching semiconductor element 3. Since the arithmetic unit 15 used this time incorporates a timer function, the timer 16 is not used, and the output of the arithmetic unit 15 is directly connected to the control input of the switching semiconductor element 6 for discharging.

When charge voltage control of the charge and discharge capacitor 9 is performed while outputting full wave rectified voltage of 60 V from the high voltage DC power supply unit 1, back electromotive force of maximum 750 V is applied to the terminal of the switching semiconductor element 3 for charge when charging is completed. occured. Similarly, when the charge voltage control of the charge / discharge capacitor 9 is performed while outputting a full-wave rectified voltage of 120 V from the high voltage DC power supply unit 1, back charge of up to 1250 V is generated at the terminal of the switching semiconductor element 3 for charge when charging is completed. Power has been generated. Next, when the charge voltage control of the charge / discharge capacitor 9 was performed while outputting a full-wave rectified voltage of 180 V from the high voltage DC power supply unit 1, the charging switching semiconductor element 3 was burnt out. It is considered that a back electromotive force exceeding the withstand voltage (2 kV) is probably applied to the terminal of the switching semiconductor element 3 for charging. A graph illustrating the relationship between the set voltage and the generated back electromotive force is shown in FIG. When the set voltage is close to the DC power supply output voltage, the back electromotive force is small, but it can be seen that the back electromotive force tends to increase as the set voltage decreases. This is because the larger the difference between the set voltage and the DC power supply output voltage, the larger the charging current flowing to the charging switching semiconductor element 3 when charging is stopped.

Next, a CR element (4 + 5) was added to the above circuit to obtain a circuit similar to FIG. By increasing the capacitance (C1) of the CR element to a certain extent and reducing the DC resistance (R1) to a certain extent, it is possible to suppress the back electromotive force generated at the completion of charging. For example, C1 = 5 μF, R1 = 10 Ω By doing this, the back electromotive force can be suppressed to about 230 V even when the output of the high voltage DC power supply unit is 150 V, and the back electromotive force is about 600 V even if the output of the high voltage DC power supply unit is 450 V (FIG. 4). ).

FIG. 5 shows the result of measuring the back electromotive force while fixing the DC power output at 120 V and the set voltage at 35 V in the above circuit and changing the values of C1 and R1. As C1 increases, it can be seen that the back electromotive force tends to be suppressed. This indicates that the larger C1 is, the more inductive energy in the circuit causing the back electromotive force can be absorbed in C1. Moreover, when R1 becomes large, the current flowing into C1 is suppressed, and it can be seen that the back electromotive force tends to increase.

FIG. 6 shows the result of measurement of the change of the back electromotive force with respect to the change of the set voltage while changing the magnitude of C1 in the more practical area in the above circuit. R1 is fixed at 40 Ω. Although the back electromotive force did not exceed the withstand voltage of the charging switching semiconductor element 3 at any value of C1, the case where C1 is maximized (C1 = 10 μF) is the same as the tendency seen in FIG. 5. The back electromotive force was suppressed.

FIG. 7 shows the results of measurement of the change in back electromotive force with respect to the change in set voltage while changing the magnitude of R1 in a region close to practical use as in FIG. C1 is fixed at 5 μF. Although the back electromotive force did not exceed the withstand voltage of the charging switching semiconductor element 3 at any value of R1, the case where R1 is minimized (R1 = 1Ω) is the most similar to the tendency seen in FIG. The back electromotive force was suppressed.

By using the CR element in this way, it becomes possible to control the charging voltage of the charge / discharge capacitor 9 without damaging the charging switching semiconductor element 3. However, even if the charging switching semiconductor element 3 is opened, the charge in the capacitor included in the CR circuit flows into the charge / discharge capacitor 9, causing a problem that the charging voltage is an overshoot of the set voltage. It has been found. The relationship between the overshoot amount and C1 and R1 of the CR element is shown in FIG. 8 and FIG.

FIG. 8 is a graph showing how much the charge voltage overshooted when the measurement of FIG. 6 was performed. The amount of overshoot is determined by subtracting the value of the set voltage from the charge voltage that was actually charged at the end of charge. According to this result, the opposite tendency to the case of the back electromotive force is observed, and as C1 becomes larger, the charging voltage tends to overshoot the set voltage significantly. When C1 is 1.8 μF, the overshoot amount is about 4 V, which is less than 1% of the maximum charging voltage (= 450 V), but when C1 is 10 μF, the overshoot amount increases to near 10 V , Has exceeded 2% of the maximum charging voltage.

FIG. 9 is a graph showing how much the charging voltage overshooted when the measurement of FIG. 7 was performed. This result also has a tendency opposite to that of the back electromotive force, and it can be seen that the charging voltage tends to overshoot the set voltage significantly as R1 decreases. When R1 is 80Ω, the overshoot amount is about 4V and less than 1% of the maximum charging voltage (= 450V), but when R1 is 1Ω, the overshoot amount rises to near 10V, the maximum Over 2% of the charging voltage.

As shown in FIGS. 8 and 9, in order to reduce the overshoot, it is necessary to make C1 of the CR element smaller and R1 larger, which tends to increase the back electromotive force. That is, the magnitudes of C1 and R1 need to be selected in consideration of the characteristics of the circuit, the withstand voltage of the used component, the specifications required for the product, and the like.

The selection of the proper C1 and R1 can be carried out as follows. First, the maximum counter electromotive force V2 when the CR element is not used is calculated. Specifically, charging is performed in a state where the output voltage of the high voltage DC power supply unit 1 is lowered in a circuit without the CR element (the circuit of Example 1), and the back electromotive force is measured. Calculate the back EMF in the case of the required voltage. For example, in the above example, the back electromotive force generated when the output voltage of the high voltage DC power supply unit 1 is 120 V was 1250 V at maximum, so when the voltage actually used is 600 V, V2 is 1250 × 600/120 = 6250 V It becomes. Next, the maximum value of the charging current (= maximum charging current I) flowing through the charging switching semiconductor element 3 during charging is measured. Similarly, charging is performed with the output voltage of the high voltage DC power supply unit 1 lowered to measure the charging current, and the maximum charging current I in the case of the voltage to be actually used is calculated from the charging current. In the case of this example, I was 22.5 A. C1 is determined by substituting these measured values into “Equation 1”. In the case of the circuit of FIG. 1, since the inductance on the circuit is only the inrush current buffer element 2, L = 10 mH in the present embodiment (in the case of the circuit of FIG. 5, the inrush current buffer element 2 and the pulse coil The sum of the inductances of 10 becomes L). α is usually about 0.5, but may be increased to about 0.75 when it is desired to reduce voltage overshoot. Conversely, if it is desired to further suppress the back electromotive force, it may be lowered to about 0.25. In this example, the breakdown voltage (V1) of the charging switching semiconductor element 3 is 2 kV, and α is calculated as 0.5. As a result, the appropriate C1 was calculated to be 4.93 μF. In practice, C1 was 5 μF, and as a result of mounting several types of CR elements using C1, 60 Ω was appropriate as R1. By using a CR element of C1 = 5 μF and R1 = 60 Ω, even if the output of DC power supply unit 1 is set to 600 V, the back electromotive force at the charge stop is suppressed to 700 V, and the overshoot of the charge current is 4 V or less Could be suppressed. As a result, rapid and stable charge voltage control can be performed in the range of 60 V to a maximum of 600 V with a very simple and compact circuit configuration without burning the charging switching semiconductor element 3.

Assuming that the energy of the entire charging circuit at the time of charging is equal to the inductive energy due to the inductance of the entire charging circuit, part of this energy is absorbed as capacitive energy of the capacitor in the CR element, and the rest is the back electromotive force The “Equation 1” is derived from the model that appears at the terminals of the charging switching element 3 and the value of C1 that has the effect of suppressing the back electromotive force to such an extent that the terminals of the charging switching element 3 are not broken is calculated. It is possible. The consistency with each parameter in the charge control of the actual circuit is also confirmed.

In the circuit of the second embodiment, the case where the set voltage is lower than the current charge voltage is considered. When the control unit 15 does not perform control, when the set voltage is lowered than the current charge voltage, the charge of the charge / discharge capacitor 9 is discharged to the attenuator in the charge voltage monitoring means 8 and falls below the set voltage. At the point of time, charging is started by the comparator 14 and the charging voltage converges to substantially the same value as the set voltage. However, since the discharge rate is rather slow, it takes a long time to converge to the target charge voltage. In this embodiment, the internal resistance in the attenuator is about 500 k.OMEGA., For example, it takes two minutes or more to reach the voltage of 10% of the maximum charge voltage from the maximum charge voltage. If a large-capacity low-resistance discharge resistor is connected in parallel to the charge / discharge capacitor 9, the discharge speed will be faster, but in order to maintain a constant charge voltage, the charge switching semiconductor element 3 must be opened and closed frequently. Also, the heat generation of the discharge resistance results in useless Joule heat loss, resulting in deterioration of the electrical efficiency.

Therefore, the capacitance (C2) and the discharge resistance (R2) of the charge / discharge capacitor 9 in the calculation unit 15, the drop rate of the set voltage (V / V0, V is the set voltage after the setting change, V0 is the setting before the setting change) The discharge time t is calculated using “Equation 2” from the voltage), and the discharge switching circuit 6 is closed during the discharge time to perform control to discharge the charge in the charge / discharge capacitor to the discharge resistor 7 The In the present embodiment, β was set to 0.98. The value of β is normally set to 1.0, and is set to about 1.1 when it is desired to undershoot the charge voltage at the completion of discharge control, and to about 0.9 when it is not desired to undershoot. As a result, after changing the set voltage, it becomes possible to converge on the target charging voltage in about 0.7 seconds at maximum. The value of the DC resistance of the discharge resistor 7 should be smaller if you want to improve the response of the charging voltage to changes in the setting voltage, and if there is no problem even if the response is low, you may select a larger resistor. When the value of is small, it is necessary to use a large resistance of heat capacity. Although “Equation 2” is derived from the differential equation that describes the movement of charge in a simple model with a capacitor and a discharge resistance, it is an experiment that it is sufficiently compatible with the calculation of the discharge time of the actual circuit. It confirms with.

Using the device according to the present invention, even if a patient who has hindlimb movement due to brain dysfunction is normal, if peripheral nerves and muscles are normal, stimulation by continuous magnetic pulses can move the limb largely with less pain. It becomes. By voluntarily moving the muscles, it is possible to improve the patient's willingness to move the paralyzed limbs, and it is also effective in preventing muscle atrophy. A device using the present invention is expected to be widely used as a device for rehabilitation of quadriplegia patients.

1: High voltage DC power supply unit 2: Inrush current buffer element 3: Switching semiconductor element for charge 4: CR element capacitor 5: CR element resistance 6: Discharge switching semiconductor element 7: Discharge resistance 8: Charge voltage monitoring means 9 : Charge / discharge capacitor 10: Magnetic stimulation coil 11: Switching semiconductor element for excitation 12: Target portion 13: Set voltage (set voltage input interface)
14: comparator 15: computing device 16: timer A: charge switching circuit unit B: discharge switching circuit unit C: discharge circuit unit

Claims (4)

A discharge circuit section in which a pulse coil for magnetic therapy for generating an eddy current at a target site, a charge / discharge capacitor, and an excitation switching semiconductor element for supplying a discharge current from the charge / discharge capacitor to the pulse coil are connected in series in a ring. ,
A charging switching circuit portion comprising a charging switching semiconductor element and a CR element connected in parallel to a contact of the charging switching semiconductor element;
A discharge switching circuit element comprising a discharge switching semiconductor element, a discharge resistance connected in series to the discharge switching semiconductor element, and a DC power supply section for outputting a DC voltage or a full-wave rectified voltage;
It consists of a comparator that compares the set voltage with the charge voltage of the charge / discharge capacitor ,
The DC power supply unit and the charge / discharge capacitor are connected therebetween via the charge switching circuit unit, and the discharge switching circuit unit is connected in parallel to the charge / discharge capacitor,
A medical magnetic pulse generator characterized by adjusting a charging voltage of a charging / discharging capacitor by opening / closing a contact of a charging switching semiconductor element triggered by an output of the comparator. The capacitance (C1) of the CR element, the withstand voltage (V1) of the charging switching semiconductor element, the back electromotive force (V2) generated at both ends of the charging switching semiconductor element without the CR element, and the total on the charging circuit The medical magnetic pulse generator according to claim 1, wherein the inductance (L) and the maximum value (I) of the charging current flowing through the charging switching semiconductor element at the time of charging satisfy "Equation 1". When the set voltage is changed to a smaller direction, the discharge switching semiconductor element is closed for a predetermined discharge time to release the charge in the charge / discharge capacitor to the discharge resistor, thereby causing the charge / discharge capacitor to discharge. Function of lowering the charge voltage of the battery, the discharge time (t), the capacitance of the charge / discharge capacitor (C2), the total DC resistance of the discharge resistor (R2), the rate of drop of the set voltage (V / V0, V: setting change The medical magnetic pulse generator according to claim 1 or 2, wherein the relationship between the subsequent set voltage V0 is the set voltage before the setting change satisfies "Equation 2". 4. The medical magnetic pulse generator according to claim 3, wherein the excitation switching semiconductor element is not closed during the discharge time.