3 .
SCHEMATIC DIAGRAM DESCRIPTION
3 . 1
PRINTED CIRCUIT BOARD (see Schematic, page 11)
3 . 1 . 1 Main Power Supply.
The DC voltage from the switchmode power supply is applied to the electronics
through the diode bridge BR1. The bridge provides a level of protection against
wiring errors. The 24 volt DC supply supplies power to switching regulators
IC11, & IC12 and the Piezo speaker.
Switching regulator IC11 su5 volt rail at 1A. Switching regulator IC12 is
the variable voltage supply. This supply is used to power the output amplifier
from 0 to +25 volts DC at 3A. The power supplies output voltage is controlled by
the microcontroller via filtering components R2, C29 & R5.
3 . 1 . 2 Oscillator, Output Stage & Contact Sense Control.
IC7 & IC8 form a PLL up convertor to generate the 1MHz signal for the output
stage. An input frequency of 61Hz is applied to pin 14 of IC7 from the
microcontroller and is multiplied by the PLL circuit 16385 times to a value of
1MHz or 3 MHz on pin 4 of IC9. IC10B is used to gate this signal for pulsed
mode. This signal is than buffered by IC9 to drive Q1 the output stage.
Alignment of the treatment applicators is controlled by the microcontroller and the
tune point of the applicators is stored in the eeprom located in the connector of
the treatment applicator.
L5 monitors supply current level in the output stage. Comparing this value with
preset values stored in eeprom, signals an in-contact or contact loss. If an
contact loss condition is encountered, the microcontroller reduces the output
power to 1W total (0.2 Watts/cm
2
) and pauses the timer. When contact is
reestablished the timer is restarted & power level is restored to that selected.
IC10A, IC10B & IC10C drive the bi-colour LEDs in the treatment applicators for
contact status.
Two output connectors are provided, J1 and J2, and the selection of one
particular connector is controlled by the “Applicator” key on the front panel and
the microprocessor. Relays RL1 and RL2 provide the necessary switching.
3 . 1 . 3 Microcontroller
IC13 resets the microcontroller IC1 on power up. The control program is stored
in memory IC3 and IC2 provides the address latching for IC3. IC4 provides the
external memory enable control.
The microcontroller monitors the keys and contact status and controls the drive
signal frequency, the seven segment displays, the piezo speaker drive and the
treatment applicators power output.
Metron Accusonic Plus
__________________________________________________________________
Version 1.6
March 2002
Page 6 of 12
