GB1577834A

GB1577834A - Apparatus for producing alternating currents for electrotherapeutic treatment

Info

Publication number: GB1577834A
Application number: GB1445077A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-04-07
Filing date: 1977-04-05
Publication date: 1980-10-29
Also published as: DE2615157C2; DE2615157A1; ATA983776A; AT370628B; NL7614140A

Description

(54) APPARATUS FOR PRODUCING ALTERNATING CURRENTS FOR ELEC TROTHERAPEUTIC TREATMENT (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company of Berlin and Munich, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an apparatus for producing alternating currents for electrotherapeutic treatment.

Apparatus for use in interference current therapy is described in German Offenlegungsschrift 2 143 562, in which the phase of the useful current in one of a total of two electrode circuits is altered periodically by means of a phase shifter. This phase shifter comprises two monostable trigger stages, the first of which pulse-width modulates the square-wave output pulses of a medium frequency oscillator in dependence upon the output frequency of a low fequency oscillator. The second monostable trigger stage is triggered by the trailing edge of each pulsewidth modulated output pulse of the first monostable trigger stage, and as a result should produce output square-wave pulses having a mark-to-space ratio of 1:1 and the frequency of the medium frequency oscillator, the phase of which can be shifted periodically.

According to this invention there is provided apparatus for producing alternating currents for electrotherapeutic treatment, the apparatus including: a first oscillator, connected with a first electrode for electrotherapeutic treatment for providing it with a first alternating current at a frequency suitable for electrotherapy; a second oscillator, connected with a second electrode for electrotherapeutic treatment for providing it with a second alternating current at a frequency suitable for electrotherapy, a third oscillator for producing a third alternating current, of lower frequency than the first and second alternating currents, the third oscillator being connected with the second oscillator for producing a periodic variation of the phase of the second alternating current in relation to the first alternating current; and phase control means connected with the first and second oscillators for comparing the first and second alternating currents and controlling the second oscillator, on the basis of the comparison, such that the frequency of the first alternating current is in a predetermined relationship with the frequency of the second alternating current.

The apparatus could be further provided with a fourth oscillator, for producing a fourth alternating current, and further phase control means, connected with the first and fourth oscillators for comparing the first and fourth alternating currents and controlling the fourth oscillator, on the basis of the comparison, such that the frequency of the first alternating current is in a predetermined relationship with the frequency of the fourth alternating current. In this case, a source of oscillation could be provided, for producing a fifth alternating current, of lower frequency than the first, second, and fourth alternating currents, the source being connected with the fourth oscillator for producing a periodic variation of the phase of the fourth alternating current in relation to the first alternating current The first-mentioned periodic variation could have a frequency equal to the frequency of the third alternating current.

The second-mentioned periodic variation could have a frequency equal to the frequency of the fifth alternating current.

In the case of apparatus provided with the source, the source could be provided by one of two outputs of the third oscillator. These two outputs could comprise an inverting output and a non-inverting output.

The phase control means could include phase comparison means.

Preferably, the phase control means comprises a phase comparator connected in series with a low pass filter.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figures 1, 5 and 6 show block circuit diagrams of three embodiments of the invention, and Figures 2 to 4 illustrate interference current curves occurring in use in the embodiments according to Figures 1, 5 and 6 over a range of phase shift angles.

Referring to Figure 1, 1 is a medium frequency oscillator which produces, for example, output pulses with a frequency of 5 kHz. A further medium frequency oscilltor 2, has an adjustable output frequency in the range of 1 to 10 kHz, for example. The second medium frequency oscillator 2 and the first medium frequency oscillator 1 are connected with a phase control circuit which includes a phase detector 3 in series with a low pass filter 4. In this example the phase detector 3 may be designed, according to its type of construction, such that its control circuit effects a phase shift in the range: O (p (p < 4;r. The output voltage of the filter 4 generally comprises a direct voltage component and a superimposed alternating voltage component. This output voltage serves as a signal for the frequency control of the second medium frequency oscillator 2. If the first oscillator 1 docs not supply a signal to the phase detector 3 then the second oscillator 2 oscillates with its static or centre frequency, which generallv differs from the frequency of the oscillator 1. If. on the other hand, an output signal from the first oscillator 1 is applied to the phase detector 3, then the frequency of the second oscillator 2 is adjusted with respect to that of the first oscillator 1 and the output signal of the second oscillator 2 assumes a defined phase relation with reference to that of the first oscillator I , depending upon the type of construction of the phase detector 3. This phase relation can be altered in a periodic manner in dependence on the frequency of a low frequency voltage (in the range 0 - 200 Hz) produced by a low frequency oscillator 5. the output of which is connected with the output of the low pass filter 4 and acts as a variable disturbance voltage U(t) According to the phase range of the phase detector 3. periodic phase shifts are produced by the Figure 1 embodiment in the range 0" (p S lS() or alternativelv. in the range 0 Cf ( S 36O". The interference current curves obtaincd as a result of voltage superposition in each case are illustrated in Figures 3 and 4. Figure 2 shows a graph representing the variation of the phase angle (p and the variation of the interference voltage Us both as functions of time, over the period T NF of the (sinusoidal or triangular) low frequency voltage produced by the oscillator 5. The shape of the curve shown in Figure 3 results from a phase shift corresponding to that represented by curve I in Figure 2 and is the interference current result of the voltages U1 and U2 of the first and second medium frequency oscillators, 1 and 2 respectively, supplied via low pass filters 6 and 7 respectively and amplifiers 8 and 9 respectively to electrodes 10 and 11 respectively. As indicated, the phase shift is in the range 0 S cp s 1800 (the superposition image corresponds to an amplitude-modulated oscillation). Similarly, from a phase shift corresponding to that represented by curve II in Figure 2, there results a superposition result as shown in Figure 4, the phase shift here being in the range 0 S (p S 360" (the superposition image corresponding to a beat, or also amplitude modulation, with a suppressed carrier).

The Figure 1 embodiment can only produce a periodic phase shift of the useful current in the electrode 11. If a periodic phase shift of the useful current in the electrode 10 is also desired then. referring to Figure 5, it is obtained by connecting an additional medium frequency oscillator 12 to the electrode 10. This oscillator 12 and the first medium frequency oscillator 1 are connected with a further phase control circuit 13, 14. In this embodiment the low frequency oscillator 5 is connected by, for example, two opposingly operating outputs (inverting and non-inverting outputs) with the two medium frequency oscillators 2 and 12. Figure 6 shows a modification of the embodiments shown in Figures 1 and 5, in which a plurality of additional medium frequency oscillators 2 are associated with a plurality of phase control circuits 3, 4 in successive stages. At the electrode circuit outputs E, to E0 there are produced useful currents, the relative phase of which can be altered periodically in dependence upon the relative phases of the outputs of the additional oscillators 2 with which are connected a plurality of low frequency oscillators 5 n WHAT WE CLAIM lS: 1. Apparatus for producing alternating currents for electrotherapeutic treatment, the apparatus including: a first oscillator, connected with a first electrode for electrotherapeutic treatment for providing it with a first alternating current at a frequency suitable for electrotherapy; a second oscillator, connected with a second electrode for electrotherapeutic treatment for providing it with a second alternating current at a frequency suitable for electrother

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The phase control means could include phase comparison means. Preferably, the phase control means comprises a phase comparator connected in series with a low pass filter. The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figures 1, 5 and 6 show block circuit diagrams of three embodiments of the invention, and Figures 2 to 4 illustrate interference current curves occurring in use in the embodiments according to Figures 1, 5 and 6 over a range of phase shift angles. Referring to Figure 1, 1 is a medium frequency oscillator which produces, for example, output pulses with a frequency of 5 kHz. A further medium frequency oscilltor 2, has an adjustable output frequency in the range of 1 to 10 kHz, for example. The second medium frequency oscillator 2 and the first medium frequency oscillator 1 are connected with a phase control circuit which includes a phase detector 3 in series with a low pass filter 4. In this example the phase detector 3 may be designed, according to its type of construction, such that its control circuit effects a phase shift in the range: O (p (p < 4;r. The output voltage of the filter 4 generally comprises a direct voltage component and a superimposed alternating voltage component. This output voltage serves as a signal for the frequency control of the second medium frequency oscillator 2. If the first oscillator 1 docs not supply a signal to the phase detector 3 then the second oscillator 2 oscillates with its static or centre frequency, which generallv differs from the frequency of the oscillator 1. If. on the other hand, an output signal from the first oscillator 1 is applied to the phase detector 3, then the frequency of the second oscillator 2 is adjusted with respect to that of the first oscillator 1 and the output signal of the second oscillator 2 assumes a defined phase relation with reference to that of the first oscillator I , depending upon the type of construction of the phase detector 3. This phase relation can be altered in a periodic manner in dependence on the frequency of a low frequency voltage (in the range 0 - 200 Hz) produced by a low frequency oscillator 5. the output of which is connected with the output of the low pass filter 4 and acts as a variable disturbance voltage U(t) According to the phase range of the phase detector 3. periodic phase shifts are produced by the Figure 1 embodiment in the range 0" (p S lS() or alternativelv. in the range 0 Cf ( S 36O". The interference current curves obtaincd as a result of voltage superposition in each case are illustrated in Figures 3 and 4. Figure 2 shows a graph representing the variation of the phase angle (p and the variation of the interference voltage Us both as functions of time, over the period T NF of the (sinusoidal or triangular) low frequency voltage produced by the oscillator 5. The shape of the curve shown in Figure 3 results from a phase shift corresponding to that represented by curve I in Figure 2 and is the interference current result of the voltages U1 and U2 of the first and second medium frequency oscillators, 1 and 2 respectively, supplied via low pass filters 6 and 7 respectively and amplifiers 8 and 9 respectively to electrodes 10 and 11 respectively. As indicated, the phase shift is in the range 0 S cp s 1800 (the superposition image corresponds to an amplitude-modulated oscillation). Similarly, from a phase shift corresponding to that represented by curve II in Figure 2, there results a superposition result as shown in Figure 4, the phase shift here being in the range 0 S (p S 360" (the superposition image corresponding to a beat, or also amplitude modulation, with a suppressed carrier). The Figure 1 embodiment can only produce a periodic phase shift of the useful current in the electrode 11. If a periodic phase shift of the useful current in the electrode 10 is also desired then. referring to Figure 5, it is obtained by connecting an additional medium frequency oscillator 12 to the electrode 10. This oscillator 12 and the first medium frequency oscillator 1 are connected with a further phase control circuit 13, 14. In this embodiment the low frequency oscillator 5 is connected by, for example, two opposingly operating outputs (inverting and non-inverting outputs) with the two medium frequency oscillators 2 and 12. Figure 6 shows a modification of the embodiments shown in Figures 1 and 5, in which a plurality of additional medium frequency oscillators 2 are associated with a plurality of phase control circuits 3, 4 in successive stages. At the electrode circuit outputs E, to E0 there are produced useful currents, the relative phase of which can be altered periodically in dependence upon the relative phases of the outputs of the additional oscillators 2 with which are connected a plurality of low frequency oscillators 5 n WHAT WE CLAIM lS:

1. Apparatus for producing alternating currents for electrotherapeutic treatment, the apparatus including: a first oscillator, connected with a first electrode for electrotherapeutic treatment for providing it with a first alternating current at a frequency suitable for electrotherapy; a second oscillator, connected with a second electrode for electrotherapeutic treatment for providing it with a second alternating current at a frequency suitable for electrother

apy; a third oscillator, for producing a third alternating current, of lower frequency than the first and second alteranting currents, the third oscillator being connected with the second oscillator for producing a periodic variation of the phase of the second alternating current in relation to the first alternating current; and phase control means connected with the first and second oscillators for comparing the first and second alternating currents and controlling the second oscillator, on the basis of the comparison, such that the frequency of the first alternating current is in a predetermined relationship with the frequency of the second alternating current.

2. Apparatus according to claim 1, provided with a fourth oscillator, for producing a fourth alternating current, and further phase control means, connected with the first and fourth oscillators for comparing the first and fourth alternating currents and controlling the fourth oscillator, on the basis of the comparison, such that the frequency of the first alternating current is in a predetermined relationship with the frequency of the fourth alternating current.

3. Apparatus according to claim 2, provided with a source of oscillation, for producing a fifth alternating current, of lower frequency than the first, second, and fourth alternating currents, the source being connected with the fourth oscillator for producing a periodic variation of the phase of the fourth alternating current in relation to the first alternating current.

4. Apparatus according to any preceding claim, wherein the first-mentioned periodic variation has a frequency equal to the frequency of the third alternating current.

5. Apparatus according to claim 3 or claims 3 and 4 wherein the secondmentioned periodic variation has a frequency equal to the frequency of the fifth alternating current.

6. Apparatus according to claim 3, or claim 4 or 5, as dependent upon claim 3, wherein the source is provided by one of two outputs of the third oscillator.

7. Apparatus according to claim 6, wherein the two outputs comprise an inverting output and a non-inverting output.

8. Apparatus according to any preceding claim, wherein the phase control means includes phase comparison means.

9. Apparatus according to any preceding claim, wherein the phase control means comprises a phase comparator connected in series with a low pass filter.

10. Apparatus according to any preceding claim, wherein the first, second and fourth (if present) oscillators are medium frequency oscillators, the third oscillator is a low frequency oscillator. and (if present) the source is a low frequency source.

11. Apparatus for producing alternating currents for electrotherapeutic treatment, substantially in accordance with any example herein described with reference to the accompanying drawings.