Voltage Regulators; Interface Connectors; Ultrasonics Board-Ultrasonic Generator; Fundamentals Of Operation - Integra Cusa Excel Service Manual

Ultrasonics Board–Ultrasonic Generator
Ultrasonics Board–Ultrasonic Generator
7-8

Voltage Regulators

There are voltage regulators for the isolated supplies. LM317 adjustable
regulators provide op amps with supply voltages with enough overhead margin to
output voltages in the required range. A switching regulator boosts and regulates
the 5V supply for the machine control and display driver boards. This is necessary
because the 5Vin signal is expected to dip momentarily due to the voltage drop
when the displays are lit up. A diode placed around the regulator eliminates start
up delay in the 5V supply for the PLD. This sheet shows bypass capacitors as well
as the independent power shutdown driver circuits. The open collector output
signals drive an opto-isolator LED inside the power modules in order to shut off
the supplies.

Interface Connectors

J2 and J3 are the ultrasonics interface connectors. J1 is the 5V input power supply
connector. J5 is the power shutdown control connector. J4 is the display board
interface connector.

Fundamentals of Operation

The CUSA EXcel ultrasonic generator is based on the principle of the Wien
Bridge Oscillator. The system has a non-inverting feedback loop to establish the
fundamental frequency of oscillation and an additional negative feedback loop,
which controls the amplitude of oscillation. The fundamental oscillation
component is a function of the resonant frequency of the magnetostrictive
handpiece.
Oscillation criteria for a Wien Bridge are that the gain around the loop must add
up to unity and the phase must add up to 360º or 0º. Only if the gain is initially
greater than unity and some perturbation (noise) in the initial conditions of the
system exists can startup occur.
The handpiece design uses the magnetostrictive and inverse magnetostrictive
effects. A magnetic field produces a small change in the physical dimensions of
ferromagnetic materials—on the order of several parts per million in steel—and,
conversely, a physical deformation or strain (or stress which causes strain)
produces a change of the magnetization in the material.
Much like a tuning fork excited by a "ping" or deformation, the handpiece
transducer—excited by these small deformations caused by the magnetostrictive
effect—resonates at an ultrasonic frequency. Linear operation within this
framework relies on biasing the magnetic field at a roughly linear point along the
main B-H curve. The feedback signal, sensing the change in the magnetic field
produced by the inverse magnetostrictive effect, is proportional to the
deformation.
CUSA EXcel Ultrasonic Surgical Aspiration System Service Manual