Team Number: ECE-17

Team Advisor: Dr. Peter A. Lewin

Miniaturized, Portable UltrasoundDriver for Clinical Applications

• Maryam Ahmad Electrical Engineering• Jeff Kinslow Computer Engineering• Dan Rivas Electrical Engineering• Jesse Spade Electrical Engineering

Problem Description

• Current solutions for chronic wound

management have high cost, poor mobility

• Provide a viable alternative to chronic wound management

• Implemented as a low

frequency (30-100 kHz),

miniaturized, portable ultrasound applicator

• Assemble final breadboard prototype – Component Testing– Systems Integration and Integration Test

• The circuit will produce a waveform of zero-crossing tone-bursts with these attributes:

– Tone Burst Sinusoidal Frequency Range:30 kHz – 100 kHz

– Tone Burst Duration: 20 ms – 200 ms

– Pulse Repetition Frequency: 1 Hz – 30 Hz

– Output Voltage: 50 -100 Vp-p

Goals

Timer Module

DC-to-DC Converter

Battery

PowerAmplifier

Oscillator

Block Diagram

Transformer

To Ultrasonic transducer

Oscillator

Waveform Generation: Tone Burst

• Sinusoid Waveform Synthesis

• Analog Devices DDS AD9831

– Functionally identical to AD9832

– Parallel programming interface instead of serial

• ~1.1 Vp-p Sine Wave

• 0 Hz – 17.5 MHz (Master Clock Freq./ 2 )

• On-Board this CMOS chip:

– Numerically Controlled Oscillator (NCO)

– Sine Look-up Table (LUT)

– 10 bit Digital-to-Analog Converter (DAC)

Timer Module

Waveform Generation: Tone Burst

Programmed with AD software tool

via Parallel DB25 to Centronix 36 pin

Timer Module

Oscillator

Waveform Generation – Duty Cycle

• Microchip PIC12F683 Microcontroller

• Generated Duty Cycle will gate the AD9831 to produce tone-bursts

• 1.95 Hz – 17.5 MHz

• Software Library

– Enumerated list of frequency/Duty

Cycle pairs

– Functions for high-level programming

Waveform Generation – Duty Cycle

• Sample program, using our C library, to produce a 33% Duty Cycle at 30 Hz using the PIC12F683

• Compiled with freely licensed and freely available MikroElektronika microC compiler v1.6.5 (2009)

void main(){ setIOdir(GP5, OUTPUT); setOscillatorFreq(FREQ_125_KHZ); // 125kHz CLK setPWM(F_30H_D_33); // 30 Hz, 33% Duty Cycle

for(;;) { // Do nothing, let PWM continue }}

Waveform Generation – XR2206

• Monolithic Function Generator

• Functional replacement for AD9831 for presentation purposes

• Not programmable, requires external circuitry to change functionality

Optimizing Power Transfer

• Impedance matching– achieve maximum power efficiency– suppress undesired signal reflection

• Voltage step-up and current step down transformer

• Frequency of Operation:30 kHz – 100 kHz- Turns Ratio: 1:6

Testing Transformer – T36-1-X65

• T36-1-X65 from Mini-Circuits

– Turns ratio 1:6

– Frequency of Operation: 30 kHz – 20 MHz

– Successfully amplified the output signal of the operational amplifier, for an input signal to the amplifier ranging from 100 mVp-p to 500 mVp-p

– Distortion for input signals greater than 500 mVp-p

T36-1-X65 – Reason for Distortion

• Insertion Loss

Frequency (MHz)

Insertion Loss (dB)

0.03 2.44

0.05 1.60

0.10 0.89

0.20 0.69

0.27 0.67

0.47 0.55

2.17 0.38

4.66 0.50

20.00 2.38

Chosen Transformer

Implemented Transformer

• Audio Transformer F28050 from Pico Electronics

– Turns ratio of 3.06:1 (primary : secondary) in series configuration

– Turns ratio of 6.12:1 (primary : secondary) in parallel configuration

– Frequency of operation : 400 Hz – 250 kHz

– Successfully amplified the output signal of the operational amplifier, for an input signal to the amplifier ranging from 100 mVp-p to 600 mVp-p

Test results for Audio Transformer (F28050)

• Distortion for an input signal greater than 600 mVp-p

• Distortion: Frequency dependent

Input Signal :1 Vp-p @ 30 kHz, 100 kHz

Output Signal : 29.4 Vp-p , 34.1 Vp-p

• Achieved by boosting the current of the operational amplifier (by using complimentary Darlington pair) to 1 A

Input Signal : 1.1 Vp-p @ 30 kHz, 100 kHz

Output Signal from the transformer : 37.7 Vp-p

Test Results for F28050 with Minimal Distortion

Power Amplifier

• OPA453 by Texas Instruments

– Power-Supply Range of ±10 V to ±40 V

– 50 mA Continuous Current

• Piezoelectric Transducer

– 2.17 nF @ 30 kHz

• Transformer

– 100 Ω @ 30 kHz

Power Amplifier – Test Configurations

•Input signal (Tone-Burst) 780 mVp-p at 30 kHz

•Load Transformer Impedance

–Turns Ratio (n = 6.12)100 Ω @ 30 kHz

•Variable Gain

–20 V/V or 26 dB for 100 VP-P

–17 V/V or 24 dB for 80 VP-P

–10 V/V or 20 dB for 50 VP-P

•Required Current

–163 mA for 100 VP-P

–131 mA for 80 VP-P

–81 mA for 50 VP-P

Power Amplifier Modification

• “Master”, “Slave” Configuration

– Boosted Current : Approximately 100 mA

• Limitations

– Before the master slave configuration, input signal maximum ~ 500 mVp-p

– After master slave configuration signal distortion with 700 mVp-p tone-burst input signal

• Conclusion

– More load current was necessary

Power Amplifier – Final Configuration

• External Darlington Output Transistors– Boost output current

up to 1 Amp

• Maximum Input Signal– Increased above

780 mVp-p – Sufficient for desired

output signal

– Maximum Vp-p : 97.6 V (Measured with 10 :1 probe)

Tested DC-to-DC Converter

• Texas Instruments DCH010515D

• Unregulated dual output converter

• Measured Output (Vin=3.7V)

– To amplifier:

• Vout = 24.5V

• Problem

– Op-amp needed higher voltage in order to provide sufficient current to the transformer

Implemented DC-to-DC Converter

• Pico Electronics 5A28D– Unregulated dual output converter– Vin = 3.7 V, Vout = ±20 V– Switching Frequency : 40 kHz

• Noise Issues– A ripple at the input to the operational amplifier

power supplies caused distortion in the output signal

Improved Output Signal

Solution : Shunted 10 uF, 10 nF, 100 pF capacitors to ground to filter out the unwanted ripple

Input Noise

• Input Noise

– Converter projected noise onto the input signal to the operational amplifier

• Solution

– Applied two 2.2 µF capacitors between + Vin and – Vin

Input Signal without Filter

Input Signal with Filter

Battery UBP005 – Implemented solution

• Supply Voltage

- 3.7 V

• Supply Current

- Minimum of 355 mA

• Size:

- 1.22 in x 2.22 in x 0.22 in

• Only a single battery needed

Power Budget - Battery

• Battery Life = (Ib / Id) * 0.7

– Ib = Total capacity rating of the battery, mAh

– Id = Current consumption of the device, mA

Capacity Rating of Battery (mAh)

Current Consumption by the DC-DC converter (mA)

Life of Battery (hrs)

Life of battery (# of 15 min sessions)

740 355 1.45 5

Final Prototype Schematic

Prototype Circuit

System Integration

•Channel 1 : (Unamplified waveform )

–Peak to Peak Voltage : 880 mVp-p ,

–Frequency : 31.25 kHz

• Channel 2: (Amplified waveform)

–Peak to Peak Voltage : 84.0 Volts

–Measured with 10:1 probe

Waveform of Piezoelectric Transducer as the load

•Channel 1: Output pulse of the transducer

– Peak to Peak Voltage : 33.6 mV

•Channel 2 : Output pulse of the driving circuitry

– Peak to Peak Voltage : 78 mVp-p ,

– Measured with 10:1 probe

Video Demonstration

Prototype Budget

Labor Costs(@ 30% Fringe Benefits)

$125,280

Lab Costs $41,990

Electrical Components $423.50(prev. $333.62)

Overhead(@125%)$210,964

(prev. $209,505)

Grand Total Engineering Development Cost

$379,735(prev. $377,109)

Industrial Budget Summary

Gantt Chart

– Tone Burst Sinusoidal Frequency Range:30 kHz – 100 kHz

– Tone Burst Duration:20 ms – 200 ms

– Pulse Repetition Frequency:1 Hz – 30 Hz

– Output Voltage (to drive Transducer):50 -100 Vp-p

– Programmable– Miniaturization (3 cm x 3 cm)

Summary – Goals

Team Number: ECE-17

Team Advisor: Dr Peter A. Lewin

Miniaturized, Portable UltrasoundApplicator for Clinical Applications

• Jeff Kinslow Computer Engineering• Maryam Ahmad Electrical Engineering • Jesse Spade Electrical Engineering • Dan Rivas Electrical Engineering

Thank You.Special Thanks to Dr. Lewin and Youhan Sunny