GB2162066A

GB2162066A - Generation of an irregular sequence of pulses for electro-analgesia

Info

Publication number: GB2162066A
Application number: GB08517975A
Authority: GB
Inventors: Burkhard Hemm
Original assignee: Mela Elektromedizin GmbH
Current assignee: Mela Elektromedizin GmbH
Priority date: 1984-07-24
Filing date: 1985-07-17
Publication date: 1986-01-29
Also published as: GB8517975D0; DE3427243C1; NL8502119A; FR2568130A1; IT1208562B; IT8521694A0

Abstract

A circuit arrangement for generating an irregular sequence of individual pulses according to an irregular stochastic rhythm with a purely random pulse sequence for electro-analgesia comprises a noise signal source which comprises an inversely driven transistor (Tr1). From the noise signal spectrum of the noise signal source (Tr1) predetermined signals are selected by means of a subsequent filter and signal-suppression circuit (R3, C4, V2, ICM) and are used for generating individual pulses which follow each other in an irregular stochastic rhythm. The individual pulses can be adjusted with respect to their pulse width and pulse height and can also be varied with respect to their shape, so that the circuit arrangement can be adapted to very different conditions. <IMAGE>

Description

SPECIFICATION Generation of an Irregular Sequence of Pulses for Electro-analgesia This invention relates to a circuit arrangement for generating an irregular sequence of individual pulses according to an irregular stochastic rhythm for electro-analgesia, the circuit including a random generator having a frequency signal source from which the individual pulses are derived.

The generation of so-called stochastic stimulation currents for electro-analgesia has been known for a long time. The application of pulse currents, generally rectangular pulses of short duration (1 ms) and having an irregular aperiodic rhythm,for electro-analgesia has already been tried repeatedly and it has been found that such pulse currents have a maximum analgesic effect even over long periods of time and that because of the irregular pulse sequence the effect is not degraded by habit and the patient does not become accustomed to the stimulation.

The application of a stochastic stimulation current is particularly useful and effective for the following conditions: chronic pain conditions, pain in the spinal column region, lumbago, sciatic pain, arthritis, epicondylitis and periarthritis humeroscapularis.

A random generator is already known for the generation of stochastic stimulation currents, but that generator is comparatively very complicated and expensive, since it operates on the basis of a processor control and is also only capable of producing a quasi-random sequence of stimulation pulses.

It is therefore an object of the present invention to provide a circuit arrangement for generating an irregular sequence of individual pulses which is comparatively simply constructed and is capable of generating individual pulses having a pure statistical distribution (pure stochastic pulse sequence).

It is a further object of the invention to provide a circuit arrangement for generating an irregular sequence of individual pulses which is very adaptable and is capable of producing a very extensive and broad variation of stochastic stimulation currents.

In accordance with the invention there is provided a circuit arrangement for generating an irregular sequence of individual pulses according to an irregular stochastic rhythm for electro-analgesia, comprising a random generator having a frequency signal source from which the individual pulses are derived, in which the frequency signal source comprises a noise signal source and in which a filter and signal-suppression circuit is connected to follow the noise signal source for deriving from the noise signal of the noise signal source a low frequency irregular sequence of individual signals.

By the use of a noise signal source from which the generated individual pulses are derived, a pulse sequence can be produced which comprises a pure random sequence, so that any accustoming effect is completely avoided.

By the use of a noise signal source there is also the possibility of being able to adjust the middle frequency of the generated pulses by means of comparatively simply constructed circuit means within broad limits, which is also true for the voltage level of the generated pulses and for the pulse width of the generated pulses.

The noise signal source preferably comprises an inversely driven transistor, the base of which is at a reference potential, the emitter of which is at a positive or negative voltage potential of at least 10 volts, depending on whether the transistor is an NPN-type transistor or a PNP-type transistor, while the collector of the transistor has no voltage potential or has a floating potential.

According to one advantageous embodiment of the invention the filter and signal-suppression circuit comprises several stages, wherein a first stage includes a filter capacitor in order to filter out high frequency signal components from the noise signal, a comparator in order to realise the possibility of selecting only signals the signal level of which exceeds a predetermined value (comparison value), and a monostable multivibrator to suppress for example signal peaks which follow rapidly one after another, in view of the dead period of the multivibrator.

The pulse shape and/orthe pulse width of the monostable multivibrator is preferably adjustable.

The pulse shape of the pulses from the monostable multivibrator can be rectangular, triangular, sinusoidal, sawtooth-shaped, trapezoidal or can have some other shape.

A further very advantageous preferred feature of the invention is that between the comparator and the monostable multivibrator at least one counting stage may be provided. With such a counting stage the frequency of the derived pulses can be averaged or the range of fluctuation of the pulse sequence frequency can be narrowed.

A preferred embodiment of the invention will now be described by way of example and with reference to the drawing, the single Figure of which shows a connection diagram of the circuit arrangement according to the invention.

The circuit arrangement comprises a noise signal source in the form of a transistor Tri. It also comprises a filter and signal-suppression circuit which comprises a filter capacitor C4, a comparator V2 and a monostable multivibrator CM. By means of these three last-mentioned circuit components, particular signals from the noise signal spectrum of the noise signal source are selected.

The noise signal source in the form of the transistor Tri is selected with regard to the noise characteristics thereof. In the present embodiment a positive voltage from a power supply source N is supplied to the emitter of the NPN transistor Tri through a first resistance R1 and a second resistance R2. The voltage coming from the power supply source N has a value for example of +90 volts and is already stabilised by the power supply source N.

This voltage is stabilised a second time by means of the parallel connection of a capacitor C1, a zener diode Z and a capacitor C2. The voltage value at the junction point between the zener diode Z and the resistance R1 is about 40 volts.

The transistor Tri is inversely driven such that its base is at a reference potential, for example earth, while its collector is not connected to any potential or is floating in respect of the voltage thereof.

It should be understood that instead of an NPN transistor a PNP transistor can equally well be used if the polarity of the supply voltage is reversed.

The noise signals to the transistor Tr1 are fed through a capacitor C3 to a filter portion in the form of the capacitor C4 by which the high frequency components of the noise signal spectrum are filtered out. After the amplification of the remaining noise signal spectrum in an amplifier V1 having a gain which can be adjusted by means of the circuit portion including resistors R4, R6, a potentiometer P1 and a capacitor C5 the amplified signal is then fed to the comparator V2 via a resistor R7, said comparator serving here as a signal suppression circuit so as to pass only those signals, in dependence upon the adjusted comparator voltage, which exceed a comparatorthreshbld value.

A light-emitting diode LED is connected to the input of the comparator V2 through a resistor network R8, R9, R10, R11 and R12 which has two functions: on the one hand by means of said light-emitting diode LED an indication is provided that the power supply is switched on and that the apparatus is ready for use and on the other hand said light-emitting diode LED also serves as a reference voltage source. For example, through resistor R10 a voltage of +5 volts or +6 volts is supplied. It should be mentioned that the comparison voltage of the comparatorV2 can also be adjustable.

The output signals of the comparator V2 are connected through a capacitor C6 to the trigger input of the monostable multivibrator ICM, which then generates pulses having a constant pulse width. During the dead period of the monostable multivibrator ICM further signal peaks which occur are suppressed so that the monostable multivibrator ICM has not only the function of a pulse shaping stage, but also simultaneously performs a signal suppressing operation.

By means of a resistor network R13, R14, PR and a capacitor C7 the pulse width of the monostable multivibrator ICM can be adjusted within predetermined limits.

However, it is also possible to make the pulse shape of the monostable multivibrator ICM variable so that the monostable multivibrator produces either rectangular pulses, triangular pulses, sinusoidal pulses, saw-tooth pulses, trapezoidal pulses etc.

The output pulses of the monostable multivibrator ICM occur at a purely random frequency; the rhythm of such sequence is not repeated in view of the noise signal source which is used, so that the known undesirable accustoming effect is completely avoided. Therefore the pulses generated by the monostable multivibrator ICM have a pure irregular aperiodic stochastic rhythm.

The output pulses of the monostable multivibrator are fed through a potentiometer P2 to a voltage/current transducer in the form of an operational amplifier OP followed by a transistor Tr2, the emitter circuit of which includes a resistor R15 serving as a current limiting means if transistor Tr2 is fully conducting. The thus-derived current pulses are supplied through electrodes E and F to a patient. The electrodes E and F are bridged by means of a resistor R16 having a high resistance value (about 100 Kin).

Furthermore, the circuit arrangement also includes a further power supply source including a battery B and capacitors C8, C9, in order to provide a power supply having a low internal resistance and in order to provide a voltage value of about +5 volts which is used several times.

The power supply N is likewise supplied by a battery (which is not shown) so that the whole arrangement can be embodied as a portable apparatus. With such an apparatus the output terminal of the amplifier V1 can be connected to an external terminal S so that the presence of the noise signal spectrum can be checked at any time.

The values of the components used within the circuit arrangement shown are as follows: Ri=82KO R8 =560 K Q R2=470KO R9 =iOKD R3=IMn RiO=iKD R4=270D n R11=47 KQ Pi=SKO R12=470 K Q R6=1 M# Q R13=5.6 KQ R7=47 KQ R14=33 KQ The resistors PR=successively 100 Kn (potentiometer), 39 K Q and 5.6 K Q P2 =22 Kn R15=68R R16=100 KQ C1 =0.1 CIF C2 =10 guF C3 =0.1 us C4 =470 pF C5 =0.47 llF C6 =220 pF C7 =4.7 nF C8 =0.1 uF C9 =100,us Voltage value at terminal G=about +5V.

Voltage at terminal a=+10 V Voltage at terminal b=-7 V It is obvious that for a person skilled in the art many variations and changes of the circuit arrangement according to the invention can be realised, within the scope of the invention. For example, it is possible, in order to narrow the range of variation of pulse frequency of the generated pulses, to connect one or more counting stages (binary counting stages) between the comparator V2 and the monostable multivibrator ICM, whereby the possibility is created of averaging the frequency obtained.

Claims

1. A ci rcuitcircuit arrangement for generating an irregular sequence of individual pulses according to an irregular stochastic rhythm for electro-analgesia, comprising a random generator having a frequency signal source from which the individual pulses are derived, in which the frequency signal source comprises a noise signal source and in which a filter and signal-suppression circuit is connected to follow the noise signal source for deriving from the noise signal of the noise signal source a low frequency irregular sequence of individual signals.

2. A circuit arrangement according to claim 1, in which the noise signal source comprises an inversely driven transistor.

3. A circuit arrangement according to claim 2, in which the base of the transistor is at a reference potential, the emitter of the transistor is at a positive or negative voltage potential of at least 10 volts, while the collector of the transistor is connected to no voltage potential.

4. A circuit arrangement according to any preceding claim, in which the filter and signalsuppression circuit comprises a filter capacitor for filtering out high frequency signal components, and a comparator for suppressing signal components having a low signal level.

5. A circuit arrangement according to claim 4, in which an amplifier having adjustable gain is connected to follow the filter capacitor.

6. A circuit arrangement according to claim 5, in which the output of the amplifier is coupled to one input of the comparator, the second input of which is supplied with a, preferably adjustable, reference voltage.

7. A circuit arrangement according to claim 4,5 or 6, in which light-emitting diode means is coupled to the input side of the comparator, said diode means serving simultaneously as a reference voltage source for the comparator.

8. A circuit arrangement according to any preceding claim, in which the filter and signalsuppression circuit comprises a monostable multivibrator.

9. A circuit arrangement according to claim 8, in which the pulse shape and/or the pulse width of the monostable multivibrator is/are adjustable.

10. A circuit arrangement according to claim 8 or 9, in which the monostable multivibrator feeds an operational amplifier whose output voltage controls a transistor.

11. A circuit arrangement according to claim 10, in which the operational amplifiertogetherwith the transistor comprise a voltage/current transducer.

12. A circuit arrangement according to any preceding claim, in which the noise signal source is supplied with a voltage which is stabilised several times.

13. A circuit arrangement according to claim 12, which includes a battery-operated, voltagestabilised power supply.

14. A circuit arrangement according to claim 12, which includes a voltage stabilising circuit which is independent of the power supply and which is connected to the noise signal source through resistor means.

15. A circuit arrangement according to claim 9, in which the pulse width of the monostable multivibrator is adjustable between 30 and 500 p sec.

16. A circuit arrangement according to claim 9 or 15, in which the pulse shape of the monostable multivibrator is rectangular, triangular, sinusoidal, saw-tooth-shaped ortrapezoidal.

17. A circuit arrangement according to any of claims 8 to 11 when dependent on any of claims 4 to 7, in which at least one counter stage is connected between the output of the comparator and the input of the monostable multivibrator.

18. A circuit arrangement substantially as hereinbefore described with reference to the accompanying drawing.

19. Apparatus for generating an irregular sequence of individual pulses for electro-analgesia incorporating a circuit arrangement as claimed in any preceding claim.