JPH11197256A - Low-frequency therapy device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine the output current values of stimulant pulses in a low-frequency therapy device having a means for generating the stimulant pulses from a pulse transformer and a means for displaying the states of the stimulant pulses. SOLUTION: A D/A converter output signal 9 in an MPU 10 for setting the driving voltage 3 of a pulse transformer 1 is obtained. A current detection resistance 4 is installed in a primary circuit, and a voltage at each end of the current detection resistance 4 is converted via an amplifier 5 into the input signal 6 of an A/D converter built into the MPU 10, to obtain the primary current of the pulse transformer 1. A storage device in the MPU 10 stores the driving voltage value of the pulse transformer 1, the primary current value detected, and an already stored transformer characteristic value table, and the program of the MPU 10 calculates the secondary current of the transformer by referencing the characteristic value table from the driving voltage and the primary current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-frequency treatment device using a pulse transformer, and more particularly to a low-frequency treatment device with a mode display that changes the output waveform and current value of a stimulation pulse according to, for example, treatment.

[0002]

2. Description of the Related Art Hitherto, the intensity of a stimulation pulse has been changed by a variable resistor at an output terminal. The magnitude of the output current is indicated by a leveler. In some cases, the number of times the push button is pressed is output, but the magnitude of the output current is schematically displayed.

[0003]

However, simply displaying the magnitude of the output current cannot compare or collate with other persons or past treatment records, and want to accurately grasp the magnitude of the stimulation pulse. There was a problem. To do this, a current detection circuit may be provided in the secondary circuit of the pulse transformer, but this will sacrifice the insulation performance between the primary and secondary sides of the transformer. Also, in order to ensure insulation performance, the installation circuit itself becomes complicated and expensive. The present invention has been made in view of the above problems, and an object of the present invention is to provide a low-frequency therapeutic device having a high therapeutic effect by accurately grasping the current value of a stimulation pulse without impairing the insulation performance of a pulse transformer. And

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems in the prior art, a configuration of the present invention comprises a means for generating a stimulus pulse from a pulse transformer and a means for displaying a form of the stimulus pulse. In the treatment device, a D / A converter output signal for setting a drive voltage of the pulse transformer and a current detection resistor are provided in a primary circuit of the transformer, and a voltage between both ends of the resistor is A / D converted through an amplifier. The primary current value of the transformer is obtained as an input signal of the transformer. On the other hand, the storage device of the MPU has the drive voltage value, the primary current value, and the characteristic value table of the pulse transformer already stored. The program is characterized in that a secondary current of a transformer which is an output current of the low frequency treatment device is calculated by referring to a characteristic value table from the driving voltage and the primary current. It is.

[0005]

By installing a current detection circuit in the drive circuit of the pulse transformer, the secondary current of the transformer, which is the output current, can be accurately obtained without impairing the inherent insulation performance of the transformer.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a circuit diagram showing an embodiment of the low frequency treatment device of the present invention. In FIG. 1, in the first embodiment, normally, the contact of the relay 19 is connected to the signal 20 side, and the secondary output of the step-up transformer 1 is directly connected to the human body part 2 via the conductor electrode. You. 2 is a human body resistor connected in a circuit. On the other hand, on the primary side of the transformer 1, there are a pulse drive power supply 15 and a signal power supply 30, and all circuits to be controlled are completely insulated from the secondary side circuit of the transformer. On the primary side, there is an MPU 10 for controlling the circuit. Reference numeral 11 denotes an oscillator for operating the MPU, which is a source of a basic clock for pulse width, period, and other necessary time management. MPU uses RO as memory
It has M and RAM, A / D converter, D / A converter and input / output port. Although not shown, MPU
Is connected as a display device with an LCD for displaying numerical values such as a pulse width, a cycle, a timer time and a current value, and displaying a character string such as an error or a warning.

[0007] The stimulation pulse to the human body is generated by applying a predetermined set voltage to the center tap 3 of the step-up transformer and then alternately driving both ends of the primary winding to generate a secondary side induced voltage. Circuit signals are controlled by a program. In FIG. 1, the setting data of the transformer voltage is converted into an analog value by a D / A converter in the MPU, and from the output port 9 via the amplifier 14, the setting voltage of the transformer 3
Is output as In the transformer driving method, a signal 7 and a signal 8 whose pulse width / cycle and drive time are controlled by a program are alternately driven every cycle to obtain a pair of positive and negative stimulation pulses. When the signal 7 is driven, a positive (upper) pulse is obtained, and when the signal 8 is driven, a negative (lower) pulse is obtained. 3 in FIG.
Shows the pulse waveform that is the basis of the stimulation current. In addition, since most stimulation modes consist of a plurality of combinations of the basic pulse waveforms, only the peak value of the basic pulse needs to be discussed. In FIG. 1, the primary current of the transformer is converted to a voltage value by
Becomes the input signal 6 of the A / D converter of the MPU,
The digital value is read into.

FIG. 3 is a timing chart showing the operation of the present invention. In FIG. 3, reference numeral 3 denotes the application timing of the set voltage (V) to the step-up transformer, 7 denotes the application timing of the drive signal 7 having a positive waveform, and 8 denotes the application timing of the drive signal having a negative waveform. In this way, positive and negative stimulation pulses 51 are output to both ends of the human body resistance 2. Reference numeral 52 denotes a waveform of a voltage across the current detection resistor 4 generated by the primary current of the transformer. In the figure, 53
And 54 show timings at which the MPU reads the current values of the plus waveform and the minus waveform, respectively. Strictly speaking, the peak values of the positive and negative pulses are not equal, but can be considered almost the same. As shown by 51 in FIG. 3, the peak value of the output current in the previous cycle is denoted by In _-1 , and the current cycle is denoted by In. Further, the set voltage of the transformer in the previous cycle is denoted by Vn _-1 , and the current time is denoted by Vn.

FIG. 5 is a diagram showing the relationship between the primary current and the secondary current of the transformer for the explanation of the calculation formula. In the figure,
When the output resistance is R (r = R), the primary current is I ₁ and the secondary current is I ₂ . When the transformer is short-circuited on the secondary side (r =
0) The primary current is I _1S and the secondary current is I _2S . The primary current at no load (r = ∞) is defined as _IO . Since the relationship between the respective currents can be regarded as a straight line as shown in the figure, the following equation is established from the similarity condition of the triangle. _{I 2 / (I 1 -I O} ) = I 2S / (I 1S -I O) _{Accordingly, I 2 = I 2S / (} I 1S -I O) × (I 1 -I
_{O 2} )... Equation (1). _{Alternatively} , assuming that the no-load exciting current (I _O ) is sufficiently smaller than the short-circuit current (I _1S ), I ₂ = α (I ₁ −I _O ) (2) α = constant. Accordingly, no-load current for each transformer setting voltage (V) _{(I O)} and the short-circuit current (I
_1S , I _2S ) are measured and stored in the storage device of the MPU as a characteristic value table. Alternatively, a preliminary test is performed to determine the I / _O of the transformer, and then α is determined from the above equation (2) to create a characteristic value table. The no-load current (I _O ) and the short-circuit current (I _1S and I _2S ), which are the characteristic values table of the transformer stored in the MPU in advance, are displayed in FIG.

FIG. 2 is a diagram showing a flowchart of the low frequency treatment device according to the present invention. In the figure, when a pulse output is desired, 30Y, the pulse width, period, output period (timer time) and output current value of the desired stimulation pulse are manually input 32 at the beginning. For example, the set current increases (or decreases) every 1 mA each time a push button (not shown) is pressed.
Is set. The pulse width is set to increase (or decrease) every 10 μS each time the push button is pressed. Here, in the step 31, an attention flag is not set as an initial state. Next, a transformer setting voltage (V) is set 33. This is 0 V in the initial state (because it starts from 0 mA). Further, a no-load current (I _O ) and a short-circuit current (I _1S and I _2S ) at the set transformer set voltage (V) are obtained from the transformer characteristic value table 34.
The pulse output 35 outputs a voltage (Vn) corresponding to the set voltage from the port 9. Almost simultaneously,
The ports 7 and 8 are output with the set pulse width at the timings 7 and 8 in FIG. After a lapse of a predetermined time (To in FIG. 3) after the output of the pulse, the primary current is read from the input signal 6 in FIG. 1 at timings 53 and 54 in FIG. Even if the pulse width changes in the future, the reading time (To) is constant as long as the output mode does not change. After reading the primary current as a digital value from the A / D converter,
The MPU determines 37 the magnitude of the load applied to the transformer prior to the calculation. That is, it is determined whether the human body resistance is connected to the circuit (open determination). The parallel resistor 2 in FIG.
Assuming that the resistance value of No. 9 is Ro, if the position of the primary current in FIG. 6 is below the curve indicated by 60 in FIG.
U determines that the circuit is open, displays an alarm (46), and stops the output (50). In step 37, if the point on the open determination curve 60 and _{I 60} in certain setting _voltage, and open error when _{(I 1 -I 60) ≦ 0} . If (I ₁ −I ₆₀ )> 0, the secondary current (I ₂ ) is calculated from the primary current read at 36 and equation (2) 38. The secondary current is stored 39 for each cycle. FIG.
In as described, _{I n-1} the previous output value and the current value and In, in the determination of the variation value _{40, |} I n -I
_{If n−1} | ≧ 10 mA, the fluctuation value is large (difference error). After the alarm display 47, the output is stopped 50. If the difference between the previous value and the current value is less than 10 mA, the process proceeds to the next step to determine the effective value current 41. 3 in FIG.
In the basic current waveform shown in, the pulse width t, the effective value current _{I rms} from the period T and pulse height _{I p-p} is Is calculated. Therefore, in step 41, after calculating the effective value current by the equation (3), a comparison is made as to whether or not the value is within a predetermined value (K) which has already been determined. That is, if I _rms ≧ K, a warning flag is set 48 indicating that the output current value has become close to the predetermined value. If the value is within the predetermined value, the pulse width / cycle / current value and the numerical value of the timer are displayed without setting (clearing) the warning flag 42. If the user wants to change the form of the stimulation pulse (43Y), and if there is already a caution flag in step (48), it is determined in step (31), and a manual operation to increase the effective current is prohibited (49). For example, the operations of increasing the pulse width, decreasing the period, and increasing the current value are invalid and cannot be set. This is not limited to the effective value display, and the same applies to the case where the peak value itself is limited. Even if the operator wishes to change the mode and makes a mistake in setting, care is taken not to output more than the specified value.

Next, the constant current operation will be described. Step 4
In 3, when the output is not updated 43 N, the MPU corrects the set voltage for the constant current operation 45. That is, if the current value (In) is larger than the previous value (In _-1 ),
A voltage lower than the set voltage by the minimum resolution of the D / A converter is applied. If the current value is smaller than the previous value,
Apply the voltage raised by the minimum resolution. If the current value is equal to the previous value, no correction is made to the set voltage.
For example, in an 8-bit D / A converter, the minimum resolution is 1/2.
56, and a correction of ± 1/256 is performed whenever necessary. Therefore, even when the human body resistance changes, a constant current can be continuously output. As described above, the peak value (I _pp ) of the output current shown by 51 in FIG. 3 is obtained from the primary current, so that a constant current operation and a monitoring function can be performed, and alarm information useful as a low frequency treatment device is output. it can.

Next, a second embodiment will be described. In the second embodiment, in FIG. 1, the relay contact contacts the signal 21, and the output of the transformer is connected to a rectifying / smoothing circuit. The smoothing capacitors 24 and 25 are for generating a positive waveform and a negative waveform, respectively, and a double voltage is generated at both ends of both capacitors. The output of the smoothing circuit is controlled while being isolated from the primary side by photocouplers 26 and 27, respectively. The photocoupler is driven by port outputs 16 and 17 from the MPU. The series resistor 28 is a limiting resistor for suppressing the output current, and its resistance value is determined in relation to the excitation frequency, the output pulse width, and the response time. FIG. 4 is a timing chart showing the operation of the transformer secondary circuit. In the figure, when the relay is driven 55 and the output mode is switched from the first embodiment to the second embodiment, the stimulus pulse which has been directly output until now is output via the smoothing circuit. This mode is for generating a longer pulse waveform required for another treatment than the direct drive mode of the transformer. In the figure, the primary side of the transformer is excited at a constant higher frequency than the output waveform. In FIG. 4, reference numerals 7 and 8 denote excitation waveforms for plus and minus waveforms, respectively, which are driven as shown. Reference numerals 17 and 16 denote drive signal waveforms of a photocoupler for outputting plus and minus waveforms, respectively.
In FIG. 1, a secondary circuit of a transformer excited at a high frequency is rectified through two diodes 22 and positive and negative voltages are stored in smoothing capacitors 24 and 25, respectively. The held voltage is applied to the photocouplers 26 and 27, the backflow prevention diodes 23 (two) and the limiting resistor 28.
Through the human body 2. Reference numeral 56 in FIG. 4 denotes an output waveform to the human body in this mode. In addition, even when the secondary circuit of the transformer has a smoothing circuit as in this mode, the short-circuit current and the no-load current are measured in advance, including the secondary circuit (rectifying / smoothing circuit and output control circuit). If the characteristic value table is different from that of the first embodiment, the peak value of the output current can be obtained by the calculation of the expression (1) or the expression (2) as in the first embodiment.

Therefore, in any case, the procedure shown in the flowchart of FIG. 2 can be performed, and the output can be stopped when the peak current reaches a certain value regardless of the hardware.
Further, as described above, the effective value current can be easily obtained from the equation (3), and it is possible to limit the current to a certain value, including an erroneous operation. This is important for the operation of the low frequency treatment device. In the output mode of the first embodiment, the effective value current is 20 mA or 50 mA as the specified value.
Limited by mA.

Further, if a sudden load change occurs during the constant current operation, the output can be stopped immediately for safety. This prevents a large current from flowing due to an unexpected change (position shift) of the human body electrode. If the current does not increase even after the operation, it is considered that the conductor electrode is not connected to the human body. As a warning of the MPU, a "differential error" is displayed on the LCD (not shown) in the former case and an "open error" is displayed in the latter case.

[0015]

According to the present invention, a complicated current detection circuit for insulation is not required on the secondary side. Further, the magnitude of the secondary current can be measured in a state where the transformer is insulated simply by placing the current detection circuit in the transformer drive circuit. Also, when a smoothing circuit was installed on the secondary side to increase the output pulse width, the output current could be similarly measured with the primary-side detection resistor. In addition, because of the program processing, the output state is constantly monitored, and a highly safe low-frequency treatment device having a useful information processing function can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention;

FIG. 2 is a flowchart showing a program procedure of the present invention.

FIG. 3 is a timing chart showing a first embodiment;

FIG. 4 is a timing chart showing a second embodiment;

FIG. 5 is a diagram showing a relationship between a primary current and a secondary current of a transformer,

FIG. 6 is a diagram showing a characteristic value table of a transformer.

[Explanation of symbols]

 1 pulse transformer 2 human body resistance 3 transformer setting voltage 4 current detection resistor 10 MPU 51 basic current waveform

Claims (7)

[Claims] 1. A D / A converter for setting a drive voltage of a pulse transformer in a low-frequency therapeutic device having means for generating a stimulation pulse from a pulse transformer and means for displaying a state of the stimulation pulse. An output signal and a current detection resistor are provided in a transformer primary side circuit, and a voltage across the resistor is used as an input signal of an A / D converter via an amplifier to obtain a primary current value of the transformer. The device has the drive voltage value, the primary current value, and the stored characteristic value table of the pulse transformer, and the MPU program refers to the characteristic value table from the drive voltage and the primary current to obtain the low frequency signal. A low-frequency therapeutic device for calculating a secondary current of a transformer, which is an output current of the therapeutic device. 2. The rectifier circuit according to claim 1, wherein
The low frequency treatment device according to claim 1, wherein a smoothing circuit and an output control circuit are provided to control an output of the stimulation pulse. 3. A peak value of a stimulus pulse is displayed from a calculation result of the secondary current, and constant current control is performed so that the peak value becomes a constant value for each cycle of the stimulus pulse. Item 2. The low frequency treatment device according to Item 1. 4. The low-frequency therapeutic device according to claim 1, wherein the secondary current is compared with a predetermined value based on a calculation result of the secondary current, and is output with a magnitude within a certain peak current. 5. The low-frequency treatment device according to claim 1, wherein an effective value is displayed as an output current from the result of calculation of the secondary current, or an output value is output within a certain effective value current. 6. The low-frequency treatment device according to claim 1, wherein an alarm is displayed when the amount of change in the output current exceeds a certain value, and the output is stopped. 7. The low-frequency treatment device according to claim 1, wherein an alarm is displayed when the change amount of the output current is less than a certain value, and the output is stopped.