JP2008194520A - Interference wave apparatus and sine wave generating circuit used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a smooth sine wave with little strain at low cost in an interference wave generating apparatus, suppress generation of heat at a current amplification transistor of an output stage in such an apparatus, and furthermore achieve various functions such as pad separation detection even in a small device. <P>SOLUTION: The interference wave generating apparatus is provided, which utilizes the sine wave generating circuit generating a desired sine wave signal using a stepwise sine wave generated in advance by transmitting a digital output outputted from software to a D/A converter. A dedicated IC or a ladder-like resistor can be used as the D/A converter. A self-oscillation type drive circuit is provided for suppressing the generation of heat. Furthermore, a pad separation detection function and a pad short circuit detection function are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an interference wave device and a sine wave generation circuit used therefor that can be used, for example, in an interference wave therapy device or a muscle training device.

  As an example of the interference wave device, there is a handy type small interference wave treatment device disclosed in Japanese Patent Application Laid-Open No. 2004-267325. This treatment device passes at least two sinusoidal signals having different frequencies through a pair of conductors through a pad adhered to the patient's skin, and passes these sinusoidal signals to a predetermined site of the patient. Thus, treatment is performed as an interference wave signal. In recent years, it has become clear that this interference wave signal exhibits not only an effect as a rehabilitation treatment but also an effect as a muscle training.

JP 2004-267325 A

  However, for example, in the conventionally known interference wave therapy device listed above, a pulse wave is generated by the oscillation circuit 2 as shown in FIG. 1 in order to generate a sine wave signal (carrier wave is several kHz). In addition, the pulse wave generated by the oscillation circuit 2 is suddenly shaped by using the stepped RC filter 4, so that the sine wave signal is likely to be distorted. It was. Further, in this configuration, in order to change the interference frequency, it is necessary to provide a plurality of RC filters corresponding to the respective frequencies. As a result, there is a problem that the number of circuit parts increases and the cost increases. Also, as disclosed in the above publication, amplitude modulation may be applied to the interference frequency for the purpose of obtaining a rhythmic low-frequency stimulus by applying amplitude modulation to the output waveform. Since the sine wave that is the source of the waveform is generated by removing high frequency components using an RC filter, the constant of the filter must be changed according to the frequency of the amplitude modulation wave, and the frequency of the amplitude modulation wave In the case of various changes, there is a problem that the number of circuit parts increases and the cost increases.

  Further, in the conventionally known interference wave therapy device listed above, the sine wave signal shaped by the RC filter is used as it is in the output drive circuit, which is the subsequent output stage, using the current amplification transistor as it is. Since it was supposed to be amplified, there was a problem that the amount of heat generated in the transistor was large. For example, sine wave drive circuits are generally used as output drives for large medical interference treatment devices, etc. that have sufficient power supply (using a commercial power supply etc.), and this heat generation is large The problem of (large power loss) has been dealt with by dissipating heat, such as by attaching a radiator or a fan. However, in a handy type small device such as this instrument, The life of dry batteries used is limited, and as a size suitable for the handy type, for example, AA type dry batteries have a large restriction on the capacity.

  Furthermore, not only the interference wave treatment devices listed above, but interference wave treatment devices using a sine wave have characteristics of the output waveform as compared with conventional electronic treatment devices and training devices that use pulse train signals. In some cases, the output power is very high (for example, 5 times or more), and there is a high risk of abnormal heat generation or failure of the device due to a load short circuit.

  Furthermore, with these treatment devices, for example, if an electrical signal is output when the pad is not attached to the body, there is a risk that a large voltage is suddenly applied as soon as the patient touches the pad. Because there is a risk of abnormal heat generation or failure of the device due to a load short if the pads are in direct contact, it is common to provide safety devices for both pad open and pad (load) short circuit. In particular, a safety device for a small device has a function that an overcurrent protection circuit of a power supply circuit functions, or a current blown type or self-reset type fuse functions when an abnormal current flows due to a load short circuit. Although it is general, there is a technical difficulty in that the output waveform is not distorted during normal use and power loss must be minimized. In addition, in a handy type small interference wave treatment device such as the above-described conventional example, in general, there is provided a pad open detection function, that is, a function for detecting that the pad is peeled off from the patient's skin. There was also a problem that it was not.

  The present invention has been made to solve the above-described problems in the prior art, and an object thereof is to generate a smooth sine wave with low distortion and low distortion in an interference wave generator. Another object of the present invention is to suppress the heat generation of the current amplification transistor in the output stage. Further, it is an object of the present invention to realize various functions such as pad open detection even in a small device.

In order to achieve the above object, the present invention provides a sine wave which generates a desired sine wave signal by using a stepped sine wave generated in advance by passing a digital output outputted by software through a D / A converter. Features a wave generation circuit.
The D / A converter may be a dedicated IC or a ladder resistor.

Further, amplitude modulation may be performed by generating a pulse width modulation wave corresponding to the amplitude modulation wave and multiplying it with the stepped sine wave.
The stepped sine wave signal may be amplified by a self-excited oscillation type drive circuit.

  Further, a transformer is provided between the generation side that generates the sine wave signal and the output side that outputs the sine wave signal, and the generation side and the output side are electrically insulated from the primary side and the secondary side of the transformer. You may make it do.

  Further, a detection unit for detecting a current change on the primary side of the transformer may be provided, and another detection unit for detecting a current change on the secondary side of the transformer may be provided.

  Further, by connecting a photocoupler between the detection unit and the generation side, a current change on the secondary side is transmitted to the generation side in a state where the generation side and the output side are electrically insulated. Also good.

Furthermore, a detection unit that detects a current change on the primary side of the transformer, and another detection unit that detects a current change on the secondary side of the transformer, the current from the detection unit and the other detection unit You may make it determine a change by the same determination part provided in the said generation | occurrence | production side.
Further, these sine wave generation circuits may be used in an interference wave device.

  Since a sine wave is generated using software and a D / A converter, it is not necessary to provide a filter circuit for each frequency, and the number of parts can be reduced and the cost can be reduced. In addition, since a stepped sine wave is passed through a filter in advance, a waveform with less distortion can be generated.

  Further, by using a self-excited oscillation type drive circuit, heat generation of the current amplification transistor in the output stage can be suppressed. Furthermore, since the current on the secondary side of the output transformer is directly detected and transmitted to the primary side via the photocoupler, it is possible to confirm whether the pad is attached to the body without distorting the output waveform. Furthermore, since the short-circuit state is detected by detecting the overcurrent flowing to the primary side of the output transformer, abnormal heat generation and failure of the device can be prevented in advance.

  With reference to the drawings, a preferred embodiment of an interference wave device according to the present invention and a sine wave generating circuit that can be used therefor will be described below. Here, as an example, an interference wave treatment device and a sine wave generation circuit used therefor have been illustrated, but of course, the interference wave device and the sine wave generation circuit of the present invention are limited to such an interference wave treatment device. Instead, it can be applied to various interference wave devices including a muscle training device.

  This interference wave treatment device mainly includes a controller body (not shown) and at least two pairs of conductors (electrodes) CH1 that are electrically insulated from each other for transmitting electrical signals generated by the controller body. , CH2 (not shown). In addition to various operation buttons such as a power button, the controller main body may be provided with a liquid crystal display that enhances operability. This device is not so large, and it may be a so-called handy type small device that operates with a power source of about four AA batteries.

  Each conductor CH1, CH2 is connected to the controller at one end thereof. A pad (not shown) is provided at the tip of the other end. In actual use, with each conductor CH1, CH2 paired, each pad of each conductor CH1, CH2 is connected to the electrical signal from CH1 and the electrical signal from CH2 at a predetermined part of the body. In an intersecting state (4-pole interference mode), or an electrical signal from CH1 or an electrical signal from CH2 is independent from each other at a predetermined part of the body, that is, not intersecting (bipolar) In the interference mode), adhere to the patient's skin. As shown in FIG. 2, when used in the quadrupole interference mode, the CH1 pad is located at the positions of CH1-A and CH1-B, that is, in the vicinity of the human torso, and the CH2 pad is CH1-A. Are fixed at the positions of CH2-A and CH2-B intersecting with CH1-B, respectively, and when used as a two-pole interference mode, the pad of CH1 is, for example, CH1-A 'and CH1-B' The pad of CH2 is fixed to the position of CH2-A ′ and CH2-B ′, that is, one leg. In such a state, by outputting a predetermined sine wave signal from the controller main body, an electric signal is sent to the portions connecting the pads of the respective conductors, that is, the portions of the dotted line portions 17 to 20, respectively. A therapeutic effect such as rehabilitation can be given to the site. In particular, when used as a quadrupole interference mode, an interference frequency is generated at the intersection X between 17 and 18. When used as the two-pole interference mode, it is not always necessary to use both CH1 and CH2, and only one of them may be used.

  An example of a sine wave generation circuit that can be used in such an interference wave therapy device is shown in a block diagram in FIG. In the figure, since the functions of components such as the original oscillation (clock) unit 11, the reset unit 12, the switch unit 13, the memory unit 14, the display unit 15, and the CPU 16 are well known, they are not specifically described here. These elements 11 to 16 are used for both the conductors CH1 and CH2. The other elements, i.e. reference numbers 21 to 31 or 21 'to 31', are used for the respective conductors CH1 and CH2, respectively, and they have exactly the same configuration. Hereinafter, the description will be given mainly focusing on CH1, but CH2 may be considered similarly.

  The configuration of each conductor CH1 and CH2 can be roughly divided into two parts. One is a side that generates a sine wave signal (generation side), and the other is a side that outputs this sine wave signal (output side). On the generation side, a D / A converter unit 21, a modulation rate adjustment unit 22, an output voltage adjustment unit 23, a waveform shaping unit 24, a positive output drive waveform shaping unit 25, a negative output drive waveform shaping unit 26, a short detection unit 30, In addition, a portion (generation side) provided with the primary side A1 of the output voltage boosting unit 27 is included, and the output side includes the output unit 29, the open detection unit 28, and the secondary side A2 of the output voltage boosting unit 27. It is. These portions are electrically almost completely insulated by the primary side and the secondary side of the transformer of the output voltage boosting unit 27 and by the photocoupler 31. That is, CH1 and CH2 can be insulated.

  In order to generate a sine wave signal (carrier wave is several kHz) to be output to the patient through each of the conductors CH1 and CH2, first, a stepped sine wave that is a prototype is generated. This sine wave is generated mainly using the CPU 16 and the D / A converter of the D / A converter unit 21. If necessary, the generated sine wave may be subjected to amplitude modulation using the modulation rate adjusting unit 22 to give a rhythmic low-frequency stimulus to the output. Next, a sine wave that has been subjected to amplitude modulation or not subjected to amplitude modulation is adjusted by the output voltage adjustment unit 23 and shaped by the waveform shaping unit (filter unit) 24. The waveform shaping unit (filter unit) 24 is used because the sine wave output from the D / A converter of the D / A converter unit 21 is a stepped waveform and includes distortion due to subsequent amplitude modulation or the like. This is because it is shaped into a sine wave with less distortion by a low-pass filter or the like. Although not particularly illustrated, the waveform shaping unit 24 removes distortion by forming a two-stage low-pass filter with an operational amplifier and a peripheral CR. In addition, because of the interface with the next stage circuit, it is necessary to generate a waveform with the positive and negative phases reversed. Accordingly, on the one hand, a waveform obtained by inverting this waveform is generated. Since a slight delay or the like occurs when passing through the inverting circuit, it is preferable that the other non-inverting side is also passed through a buffer amplifier (not shown) of the same magnification and the conditions are the same. . Thereafter, power amplification is performed on the sine wave shaped by the waveform shaping unit 24 using an output drive circuit provided in the positive output drive waveform shaping unit 25 or the negative output drive waveform shaping unit 26. The amplified sine wave is further transmitted from the primary side to the secondary side in the transformer, and then output from the secondary side to the patient as a desired sine wave signal at the output unit 29 having a pad.

Next, these basic configurations will be described in more detail.
The prototype sine wave is generated as, for example, a stepped sine wave of 10 stages per cycle by passing the digital output output from the CPU 16 through the D / A converter of the D / A converter unit 21. As the D / A converter, a dedicated IC may be used, or a resistor 6 assembled in a ladder shape as shown in FIG. 4 may be used. By using digital output, signals can be generated at any timing and in any magnitude (for example, when using ladder resistor 6, which stage resistor of ladder resistor is used) By instructing whether to do so, the original stepped sine wave can be easily generated at a desired timing, that is, at a frequency, and at a desired magnitude, that is, an amplitude. Of course, if a dedicated IC is used, it is possible to generate a stepped sine wave more easily, but by using such a ladder resistor 6 instead of the IC, the device can be realized at a lower cost. You can also In this way, by using a CPU-controlled software and a D / A converter to generate the original sine wave in a staircase shape that approximates the sine wave, a sine wave with less distortion can be obtained and reduced. Cost, versatility, and applicability can be improved. Further, according to this configuration, for example, only the instruction of the timing of the signal to be transmitted to the ladder-shaped resistor 6 and which stage of resistance is used, that is, only one ladder-shaped resistor 6 is used. Thus, since it is possible to generate sine waves of various frequencies and amplitudes, it is not necessary to provide a filter circuit (RC filter 4 in FIG. 1) for each frequency as in the prior art. You can go down. Further, since a sine wave that is stepped in advance is passed through the waveform shaping unit 24 (filter), waveform distortion can be reduced. Furthermore, since software is involved, the output zero crossing can be easily realized. Zero cross is a function that always makes 0V when starting and ending output, and it works to prevent suddenly strong output from being applied to the patient and enhance the feeling of use. It is an indispensable function for things like containers.

  If necessary, amplitude modulation can be applied to the stepped sine wave. In order to apply amplitude modulation, a PWM (pulse width modulation) function of a microcomputer that can be provided in the CPU 16 or the like, or an amplitude modulation circuit 40 as shown in FIG. 5 can be used. These are all included in the modulation rate adjusting unit 22 of FIG. 3, and all of them generate a pulse width modulated wave corresponding to the amplitude modulated wave and multiply this with a stepped sine wave. Is.

  When the PWM function is used, the PWM modulation is performed by switching the stepped sine wave generated by the D / A converter with a transistor. For example, an open drain port of a microcomputer is used to form a variable gain amplifier to adjust the amplitude of the staircase sine wave. That is, the stepped sine wave input from the previous stage is lowered to the minimum level by the voltage dividing resistor, and the non-inverting amplifier circuit is formed by the operational amplifier and the resistor of the next stage. The non-inverting amplifier circuit changes the gain by switching to the GND connection or the open state according to the output setting of the open drain port connected by the resistor. In this PWM function, the sine wave is set to 0% to 100% when the PWM terminal is 100% modulated and the sine wave is set to 50% to 100% when the PWM terminal is 50% modulated with respect to each of the high (H) / low (L) PWM terminals. By switching, two types of modulation can be realized.

  An amplitude modulation circuit 40 as shown in FIG. 5 can also be used for amplitude modulation. The amplitude modulation circuit 40 (see FIG. 5A) mainly includes transistors T1 and T2 and resistors R1 and R2. The reason why two transistors are provided is that there are two types of modulation rates (depths) of amplitude modulation. The transistor T1 connected to the resistor R1 can be used at a depth of 100%, while the transistor T2 connected to both the resistor R1 and the resistor R2 can be used at a depth of 50%. Here, “depth” refers to the degree of modulation with respect to the amplitude before amplitude modulation is applied. In this amplitude modulation circuit 40, for example, a stepped sine wave of several kHz ((b) in FIG. 5) generated by software and the D / A converter unit 21 is converted into transistors T1 and T2 via resistors R1 and R2. A pulse width modulation signal (for example, (c) in FIG. 5) having a pulse width modulated in accordance with an amplitude-modulated wave, for example, is applied to the bases of the transistors T1 and T2. By applying to, an amplitude-modulated pulse signal ((d) in FIG. 5) can be output. The frequency of the pulse width modulation is preferably a frequency sufficiently higher (for example, several times) than one stage constituting the stepped sine wave.

  According to this configuration, the frequency of the pulse width modulated wave can be easily changed, and since the amplitude modulation is applied to the stepped sine waveform here, it is not necessary to use the sine wave directly. It is only necessary to apply a filter once to a waveform obtained by applying PWM modulation to each stepped sine wave of the amplitude modulated wave. For this reason, the number of parts and the cost can be reduced. Even if the amplitude modulation depth needs to be switched to 100%, 50%, etc., it can be easily handled by changing the voltage dividing resistance using software or by a transistor. is there. In order to adjust the output voltage of the sine wave that has been subjected to amplitude modulation or is not subjected to amplitude modulation, an amplifier (output voltage adjustment unit 23) whose degree of amplification can be controlled by the CPU, and the next stage It is transmitted in series to the filter (waveform shaping unit 24), and a smoother sine wave is obtained.

  In order to sufficiently amplify the load (human body) by amplifying the power of the sine wave signal, an output drive circuit provided in the positive output drive waveform shaping unit 25 and the negative output drive waveform shaping unit 26 is used. FIG. 6 shows an example of the output drive circuit 50. One output drive circuit is provided for each of the positive output drive waveform shaping unit 25 and the negative output drive waveform shaping unit 26. For simplification of the drawing, FIG. 6 shows a positive output drive waveform shaping unit. Only the output drive 50 provided in 25 is shown in detail, and that of the negative output drive waveform shaping unit 26 is shown in a simplified manner. The positive output drive waveform shaping unit 25 and the negative output drive waveform shaping unit 26 are respectively input with signals having opposite phases from the waveform shaping unit 24 with their phases reversed. Thereby, a voltage doubler can be equivalently applied to the output voltage booster 27 (transformer). For ease of understanding, FIG. 6 also shows the members of the output voltage boosting unit 27 and the output unit 29 that are peripheral members of the output drive circuit 50. The output drive circuit 50 of the present invention is a self-excited oscillation type drive circuit aiming at low loss and low heat generation. As will be apparent from the following description, this self-oscillation type drive circuit avoids the use in the active region, that is, avoids the use in the active region, and reduces the power consumption W by using it in the cut-on / cut-off region. The power consumption (heat generation) is suppressed by utilizing the characteristic that it can be reduced. By using such a circuit, heat generation of the current amplification transistor in the output stage can be suppressed. This method was able to improve power loss by 33%.

  The output drive circuit 50 includes a comparator OP1, two switching circuits SW1 and SW2, and a choke coil L and a smoothing capacitor C1 as main components. Each switching circuit SW1, SW2 includes switching FET1, FET2, diodes D1, D2, smoothing capacitors C3, C4, resistors R3, R4, and the like. In addition, the inverters between the comparator OP1 and the switching FET1, FET2, diodes D1, D2, smoothing capacitors C3, C4, resistors R3, R4, etc., cause the overcurrent to flow when the high-side and low-side FETs are turned on simultaneously. It also functions as a circuit for preventing (dead time control circuit).

  In amplifying the power, first, the comparator OP1 compares the reference voltage from the outside with the output voltage of its own circuit to determine ON / OFF of the switching FETs 1 and 2. When the output voltage is lower than the reference voltage, the FET 1 on the power supply side is turned on and current is supplied to the coil L. When a current flows into the capacitor C1 through the coil L, the voltage (output voltage) of the capacitor C1 rises. When the voltage of the capacitor C1 exceeds the reference voltage from the outside, the FET 2 on the GND side is turned ON, and the coil L To draw current from. When the current is drawn from the capacitor C1 through the coil L, the voltage of the capacitor C1 decreases. By repeating this many times, the output is made to follow the reference voltage from the outside. Tracking can be performed by sufficiently increasing the frequency of the self-excited oscillation above the frequency of the reference voltage (sine wave). In the present invention, since the pulse wave generated by the comparator OP1 is used to drive these FETs 1 and 2, the FET can be used in a cut-on or cut-off region. Unlike the method of directly applying an analog wave to the FET as in the case of driving, the active region is not driven, so that the power loss in the FET can be remarkably reduced. The sine wave thus amplified is then transmitted to the primary side A1 of the output transformer of the output voltage boosting unit 27, and further amplified by being transmitted to the secondary side A2, and then from the output unit 29 to the human body ( For example, it can be considered as an object having a resistance of 500Ω.

  In addition to the above basic configuration, this circuit has a pad open detection function, that is, a function that detects that the pad has been peeled off the patient's skin, and a pad short detection function, that is, the pads stick to each other. A function to detect that an overcurrent is flowing is added. In order to execute the pad open detection function, the open detection unit 28 is provided on the secondary side A2 of the output transformer, and further, the short detection unit 30 is provided on the primary side A1 of the output transformer to realize the pad short-circuit function. . FIG. 7 is a circuit diagram of the pad open detection circuit 60 and the pad short detection circuit 70 for realizing these functions. The circuit of FIG. 7 can correspond to a portion surrounded by a square 42 in FIG. However, for easy understanding, FIG. 7 also includes the output voltage boosting unit 27 and the output unit 29 which are peripheral members of the pad open detection circuit 60 and the pad short detection circuit 70.

  In detecting the pad open, in the present invention, the current on the secondary side A2 of the output transformer is directly detected in order to capture a slight change in output with a high S / N ratio. The reason for detecting the current from the secondary side A2 instead of the primary side A1 is that the current change at the primary side A1 is not stable, and only a relatively small change can be obtained even if the pad is opened. Because. The current from the secondary side A2 is detected by the resistor R5. The detected current is amplified by the amplifier OP2, converted into a direct current via the capacitor C2, and then optically connected to the primary CPU 16 via the photocoupler 31 in a state of being electrically insulated, that is, insulated. In this state, only the information is transmitted to the primary side. Thereafter, the CPU 16 provided on the primary side, more specifically, the A / D converter of the microcomputer measures the magnitude of the voltage and determines the pad open state. If it is determined that the pad is open, the output of the sine wave is stopped as necessary. The current / voltage transmitted to the CPU 16 on the primary side A1 through the photocoupler 31 is, for example, about 1.5 V when the pad is attached to the body, and about 0.1 V when the pad is open. 5V. Therefore, pad open can be detected by monitoring the magnitude of this voltage. Also, with such a configuration, it is possible to confirm whether the pad is stuck on the body without distorting the output waveform, and when it is peeled off, the output can be stopped to avoid danger. Note that the power supply necessary for operating the amplifier OP2 can be obtained by half-wave rectifying the output voltage on the secondary side. For example, the current flowing on the side 32 opposite to the GND of the secondary side switching circuit may be rectified and smoothed and then supplied to the amplifier OP2.

  On the other hand, pad short detection is performed by detecting an overcurrent flowing through the switching circuit on the primary side of the output transformer by the pad short detection circuit 70. When an overcurrent flows in the circuit, the power supply is interrupted by a current blown fuse (not shown), thereby preventing abnormal heat generation and failure of the device. When the power source (dry battery, AC adapter) is reversely connected, the fuse is blown by a short-circuit current caused by a diode, thereby also having a function of preventing damage to the circuit. In order to perform pad detection, for example, a resistor R6 of 0.1Ω is connected to the GND side 33 of the primary side switching circuit. The voltage across the resistor R6 is amplified by the operational amplifier OP3 and then monitored by an A / D converter (not shown) of the CPU 16. For example, when a voltage of 3.0 V or more is detected, the A / D converter determines that the pad is short-circuited. This A / D converter can also be used for the previous pad open detection. That is, all the current changes on the primary side and the secondary side are monitored by the A / D converter of one CPU 16, and for example, it can be determined that the pad is open if it is 1V or less, and that the pad is short if it is 3.0V or more. Therefore, according to this configuration, when both the pad short detection and the pad open detection are executed, the CPU A / D port is saved, thereby increasing the degree of freedom of design and the degree of design of the CPU. Therefore, the cost can be reduced.

  Finally, an example of a power supply that can be used in the above circuit will be briefly described. The control circuit power supply voltage (VCC) of the sine wave generation circuit used in this circuit is, for example, about 5V, and is generated by stabilizing the boosted voltage (VD) with a three-terminal regulator. The boosted voltage (VD) is, for example, a voltage of about 6 to 8 V, and is generated by boosting the input power supply voltage (VB) with a DC-DC converter. The output circuit power supply voltage (VO) is not boosted due to the property of flowing a large current, and is a system that can effectively transmit energy from the power supply in a straight line. This voltage is, for example, about 3.6 to 6V. A battery or an AC adapter is connected to the input power supply voltage (VB) via a fuse. In the case of a strong output such as an interference wave, a virtual ground is necessary to prevent an abnormal output (stimulation) when the power is turned ON / OFF. The voltage (VG) of the virtual ground can be about 1 V, for example, and is generated by dividing the VCC voltage as a virtual ground position in the signal processing circuit.

  It can be applied to various interference wave devices.

The structural example of the conventional pulse wave generator is shown. 1 illustrates the use of an interference wave therapy device according to a preferred embodiment of the present invention. 1 shows a block diagram of a sine wave generation circuit that can be used in an interference wave therapy device according to a preferred embodiment of the present invention. FIG. A ladder resistor is shown. 1 shows an example of an amplitude modulation circuit according to the present invention. 1 shows an example of an output drive circuit according to the present invention. 2 shows an example of a pad open detection circuit and a pad short detection circuit according to the present invention.

Claims (10)

  A sine wave generation circuit which generates a desired sine wave signal by using a stepped sine wave generated in advance by passing a digital output outputted by software through a D / A converter.   2. The circuit according to claim 1, wherein the D / A converter is a dedicated IC or a ladder resistor.   The circuit according to claim 1 or 2, wherein the amplitude modulation is performed by generating a pulse width modulation wave corresponding to the amplitude modulation wave and multiplying the pulse width modulation wave by the stepped sine wave.   4. The circuit according to claim 1, wherein the stepped sine wave signal is subjected to current amplification using a self-excited oscillation type drive circuit.   A transformer is provided between the generation side for generating the sine wave signal and the output side for outputting the sine wave signal, and the generation side and the output side are electrically insulated from the primary side and the secondary side of the transformer. Item 5. The circuit according to any one of Items 1 to 4.   The circuit according to claim 5, further comprising a detection unit that detects a current change on a primary side of the transformer.   The circuit according to claim 5, further comprising another detection unit that detects a current change on a secondary side of the transformer.   The current change in the secondary side is transmitted to the generation side in a state where the generation side and the output side are electrically insulated by connecting the detection unit and the generation side with a photocoupler. A circuit according to any one of the above.   A detection unit for detecting a current change on the primary side of the transformer; and another detection unit for detecting a current change on the secondary side of the transformer; and a current change from the detection unit and the other detection unit. The circuit according to claim 1, wherein the circuit is determined by the same determination unit provided on the generation side.   An interference wave device using the sine wave generation circuit according to claim 1.

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