The design of a constant voltage pulse stimulator for motor evoked potential monitoring

In order to fulfill the design requirements of motor evoked potential (MEP) stimulator in intraoperative neurophysiological monitoring (IONM) system, a kind of constant voltage pulse (CVP) stimulator has been designed. Two Flyback switching power supply (FSPS) circuits based on UC3845 provide the needed voltages. A transistor control circuit ensures that the voltage output is constant. An IGBT works as control switch to release pulses. The input and the output of the stimulator are physically isolated. Experimental results indicate that the stimulator has satisfied the design requirements. The parameters of output pulse are high-precision, rapid-response and wide-range with plenty options. When all setups are complete, the stimulator can release pulse within less than 100ms. The pulse highest amplitude is 900V. All parameters´ relative errors are less than ±10%. The pulse rise time and fall time are less than 0.4μs. The stimulator can be also employed in other operations and be modified for constant current stimulation.