DEC High-Current Pulse Generator

Transcription

1 High-Current Pulse Generator

2 Team Composition Members Greg Bulleit Stephen Chiev Matt Stegemann Ho Hsu* Wen Ya Ting* Li-yeh Yang* Shih-yao Yen* *First semester only, from Tatung University in Taiwan Advisors Robert Bouda Dr. Mani Mina John Pritchard Client High-Speed Systems Engineering Laboratory

3 Transcranial Magnetic Stimulation Transcranial Magnetic Stimulation (TMS) Medical procedure for treatment of depression Stimulation occurs from a large, focused magnetic field Magnetic field generated by a large current pulsed through a coil

4 Project Overview The goal of the client is to research a smaller and low-cost solution. This senior design project s objective is to create a high-current pulse generator device with biphasic output and adjustable pulse parameters.

5 Requirements Design and build a device that outputs a high-current pulse Pulse is biphasic or monophasic Pulse must be controllable in amplitude and width Physical device capable of hundreds of amperes, design scalable to thousands Mono-phasic Bi-phasic

6 System Level Diagram

7 Power Supply Switching from a transformer to a Toroidal transformer with a center tap to ground to power the whole design The center tap creates a negative voltage that is needed for the negative side of the biphasic pulse 12V AC power supply used for the arduino Using two smaller toroidal transformers to power the gate drivers

8 Energy Storage Using six 8200 uf capacitors Created a PCB to hold all of the capacitors together The PCB contains a discharging relay unit Three capacitors used for each side of the pulse; positive and negative sides

9 Initial Gate Drive Circuit First semester designed an opamp circuit to drive the Switching devices This circuit creates an adjustable DC voltage from the arduino PWM output Easy control by changing duty cycle of the PWM output Control can be done digitally without physical interaction with device

10 Biphasic Gate Drive Circuit Switched to using DC-DC regulators to simplify circuit By using a SEPIC and inverting buck-boost converters we can use one voltage supply Can supply much greater current to the switching devices >2A Arduino cannot control output only read it from its analog input. Requires a more complex pcb to use but have designed PCB for switch regulators before

11 Biphasic Gate Drive Circuit When using high side switching it is hard to get an accurate Vgs This can be achieved using an isolated gate driver Isolation lets us use the devices sources as the virtual ground for an accurate Vgs This circuit can be used in conjunction with the SEPIC converter, allowing us to still have adjustable pulse parameters

12 MOSFET Board This board includes the main power path for the circuit Input voltage rectification and filtering is done on this board Connections for the external caps. Traces between the caps and MOSFETs are as large as possible. Main switching MOSFETs are also on this board with connections to the external gate delivers Building the PCB this way allows for design flexibility

13 Arduino Tasks Handle the triggering of the pulses to the gate drive circuits Discharge the capacitors during shutdown Inputs Analog inputs for pulse width and monitoring converter output Digital inputs for pulse trigger and capacitor discharging Outputs Digital outputs for gate pulses and capacitor discharging

14 Enclosure Contains all of the components into one box Provides no direct contact between user and device Will contain the input and outputs on the outside of the enclosure

15 Simulations NI Multisim used for simulations Used to simulate our circuit design before doing physical testing Ability to quickly modify components and test multiple versions of the circuit Limited to only a selection of components that are accurate to real-world circuitry

16 Testing Bench testing for PCB boards Functionality verification High-wattage resistors with makeshift coil for loads

17 Testing NMOS pulse PMOS pulse

18 Risks & Challenges Physical harm to user Not finishing on time Not able to find the right parts for our design Parts not working as predicted PCB boards Grounding issues Team size cut in half after first semester

19 Q & A