GE_OEC_9600_C-Arms

2 kV Generation
CONTROL INPUTS
Initializes the kV circuits by providing a control voltage and two timing (drive) signals.
The Technique Processor PCB initializes the Analog Interface PCB to create three
primary control and timing signals which control the X-ray Regulator PCB. These signals
are:
• kVp Control
• HVDRVA
• HVDRVB
KVP CONTROL
The KVP CONTROL signal is a current signal from the Analog Interface A/D U31. This
current signal is converted to a positive DC voltage proportional to the desired
kV (75mV/kVp) by the current to voltage converter U33-6 and 7. This signal is software
controlled in response to the kV selected and corrected by the calibration parameters.
This signal will vary with different kV settings.
The KVP CONTROL voltage is then inverted to a negative DC voltage by U20-6 and 7
on the X-ray Regulator PCB. This negative voltage, proportional to the desired kV, is
then applied to the R25/U23-2 summing point to be compared with the actual kV sensed
(KVP MEASURED). See KV ERROR CORRECTION, later in this section for more
information.
HVDRVA AND HVDRVB
The HVDRVA and HVDRVB signals are out of phase, fixed duty cycle, 2.5 kHz timing
signals from the Analog Interface PAL U17. The duty cycle of these signals will not vary
even as different kV settings are selected. These signals serve as timing signals for the
X-ray Regulator high voltage drive PAL U7.
KV DRIVE
Generates kV by providing the drive signals to the Darlington Driver transistors. When
an X-ray switch is pressed, the X-ray On logic activates the high voltage drive PAL U7
on the X-ray Regulator. U7 then generates its own out of phase, variable duty cycle, 2.5
Khz HVDRVA (pin 12) and HVDRVB (pin 13) drive signals. These drive signals are then
applied to the Generator Driver PCB where they are amplified by Q5, Q6 (HVDRVA)
and Q7, Q8 (HVDRVB) to approximate 15 VDC drive signals. These amplified drive
signals then drive transformers T3 (HVDRVA) and T1 (HVDRVB).