Fault circuit for stimulator
AssigneeStimulation Technology, Inc.
InventorBill H. Niemi
Life of this patent
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Abstract
An improved control circuit which may be incorporated into a medical transcutaneous nerve or muscle stimulator for disabling the output from the stimulator to stimulation electrodes connected thereto upon the occurrence of an undesirable output event of the kind which may result in an electrical shock or burn to user of the stimulator. This disablement by the control circuit may be triggered when electrode impedance exceeds a threshold level, or when the current level of the output undergoes excessive change, or when the power source to the unit is interrupted. Included may be visual signaling functions.
Claims8
An improved fault protection circuit for a medical stimulator, said stimulator having a power on/off switch and triggered output pulse generating circuit with an amplitude adjustment, said output pulse circuit being connected to an electrode load comprising:
- means for monitoring the output load impedance connected to said pulse generating circuit;
- means connected to said impedance monitoring means for disabling said generating circuitry upon the detection of an excessive impedance value;
- and
- means for monitoring the rate of change in the magnitude of the output current from said pulse generating circuit, said output current monitoring means being connected to operate said disabling means upon the detection of an excessive rate of change in said output current magnitude, wherein said impedance monitoring means includes an impedance comparator connected to the output of said pulse generating circuitry and wherein said pulse generator disabling means includes a gate in the input trigger to said pulse generating circuitry, said gate being conditioned by a signal from said impedance comparator.
An improved fault protection circuit for a medical stimulator, said stimulator having a power on/off switch and triggered output pulse generating circuit with an amplitude adjustment said output pulse circuit being connected to an electrode load comprising:
- means for monitoring the output load impedance connected to said pulse generating circuit, said impedance monitoring means including an impedance comparator connected to the output of said pulse generating circuitry;
- means connected to said impedance monitoring means for disabling said generating circuitry upon the detection of an excessive impedance value;
- and
- means for monitoring the rate of change in the magnitude of the output current from said pulse generating circuit, said output current monitoring means being connected to operate said disabling means upon the detection of an excessive rate of change in said output current magnitude;
- wherein said pulse generator disabling means includes a gate in the input trigger to said pulse generating circuitry, said gate being conditioned by a signal from said impedance comparator;
- and wherein said output current rate of change monitoring means includes a step comparator connected to said pulse generating circuit amplitude adjustment, said step comparator being connected to condition said pulse generator input trigger gate said pulse generator disabling means input trigger gate including a nand-gate having at input from each said impedance comparator and said step comparator, and an and-gate, said and-gate being connected into the triggered line to said pulse generating circuit and being enabled by the output of said nand-gate.
In a transcutaneous nerve stimulator having a power on/off switch and a triggerably operated output pulse generator for driving stimulating electrodes, said pulse generator including an amplitude control, a fault protection circuit for detecting undesirable conditions at the output, comprising:
- means for disabling said pulse generator, said means being connected to regulate an input to said pulse generator;
- means for monitoring output electrode load impedance said means being connected to the output of said pulse generator and to said disabling means;
- and
- means for monitoring the operation of said amplitude control, said means being connected to said disabling means and including a rate of change comparator, wherein said pulse generator disabling means includes means connected into the trigger line to said pulse generator for stopping trigger signals to said pulse generator and wherein said electrode load impedance monitoring means includes means for comparing the electrode load impedance to a fixed threshold value for driving said disabling means when said threshold is exceeded.
Dependencies are inferred from the claim text.