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CT 9000 ® ADV
3-10
Servo
The servo section of the motherboard is concerned with generating
the motor power, stopping the motor, sensing pressure and hard-
ware safety features.
Each topic will be covered separately.
Motor Power
Motor power is generated by a flyback regulator circuit. Flyback
regulators (Figure 3-4) use a transformer to transfer energy from
input to output.
During S1 "on" time, energy builds up in the core
due to increasing current in the primary winding. At this time, the
polarity of the output winding is such that D1 is reverse biased.
When Si opens, the total stored energy is transferred to the sec-
ondary winding and current is delivered to the load. This circuit
provides isolation and safety.
If S1 shorts out, no voltage is gener-
ated on the secondary and the motor will not move.
Di
Vin
—
Vout
Figure 3-4. Typical Flyback Regulator Circuit
The main components of the flyback regulator circuit on the MOTH-
ERBOARD
consist of T1, Q4, D5, C11 and U16.
An analog voltage
from the CPU board is input to PWM (Pulse Width Modulator) IC
U16 pin 2. This IC converts a 0 to +5V analog voltage to a 0 to
+10V PWM output signal on IC U16 pin 14. The PWM signal is
characterized by a 100kHz frequency and a 0 to 50% duty cycle.
C14 and the potentiometer R80 set the PWM frequency using the
following formula:
f= 1/2 (C14 (0.7R80))
800961-C
Nov. 2000
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