PXS-710D Section 5
61
4.2
CONTINUED:
The Power Board Inverter Assembly is powered by 115 VAC via connector TB1
(ref dwg. 100206). With circuit breaker CB1 closed, an AC voltage is applied
through current limiting resistor R1 of the Power Board PWA. The voltage is
then rectified and filtered via Diode Bridge D1 and Capacitors C1 – C2. The DC
Voltage is used as the “Rail Voltage” for the High Frequency Drive to the X-Ray
Generator.
Relay K1, contacts 1A and 1B short resistor R1, on the Power Board PWA,
during the Prep and X-ray period to allow the line to deliver the required
power. Transistors Q1 and Q2 of the Control/Generator Assembly make up a
full bridge high frequency circuit operating at approximately 30 kHz. This circuit
is energized during the X-Ray On period and is used to convert the DC voltage
back to high frequency AC to drive the high voltage transformer in the generator
assembly (approx. 30 kHz).
The Control Board PWA provides commands to the Power Board PWA electronics
for the kV reference, filament pre-heat, exposure time… and monitors the source
for faults.
U15 of the Control Board PWA provides the High Frequency Drive for the High
Voltage Supplies (anode & cathode), it drives the pulse transformer T1 through
signal FET’s Q4 & Q6. Transformer T1 drives the Gate of the IGBT’s, Q1 & Q2
located in the Power Board Assy.
U16 of the Control Board Assy. supplies the High Frequency Drive for the
filament circuitry by driving FET’s Q8 & Q9 on the Power Board PWA. These
FET’s provide the High Frequency voltage for the filament transformer T1 of the
Generator Assy.
Current transformer T4 of the Power Board PWA monitors the primary current to
the High Voltage Transformers and triggers timer IC/U13 which sends a fault to
the Microprocessor and shuts down the High Frequency Generator IC/U15
which in turn shuts down the High voltage IC’s.
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