9600 Service Manual - gmecorp-usa.com

26 Power Distribution
BATTERY CHARGER PCB
S/N 69-0001 thru 69-1000 - Asy. #00-876644 - Sch. #876643
WARNING... With the keyswitch OFF, AC power is present on the C-Arm when the
Workstation is connected to AC power and the interconnect cable is
connected to the C-Arm.
AC Input Voltage
The Battery Charger PCB receives 120V_PH1 and 120V_PH2 from the Workstation via
the interconnect cable whenever the workstation is plugged into AC and the interconnect
cable is connected to the C-Arm.
120V_PH1 and 120V_PH2 pass through the Power/Signal Interface PCB where circuit
breakers CB2 and CB3, line filters LF1 and LF3, and current limiters RT1 and RT2,
provide protection and filtering before arriving at the Battery Charger PCB.
The two phases of AC are connected to bridge rectifier CR1. On the Battery Charger
PCB, there is no connection to the minus (-) connnection of CR1, both phases are half
wave rectified. The nominal output of CR1 at the plus (+) connection is approximately
160 VDC. As well as being used for charging the batteries, this voltage is scaled down
by R7 and sent back to the Analog Interface PCB as line voltage sense (LVOLTSEN).
Low Voltage Power Supply
120V_PH1 and Neutral are also connected to transformer T1 to drive a low voltage
power supply to provide +12V and -12V for use only on the Battery Charger PCB to
power the circuitry so that battery charging can occur while the system is off. T1 drives
rectifier VR3 which in turn provides power to be regulated to + 12SEP (separate) and -
12SEP by VR1 and VR2 respectively.
Regulation
A boost type switching regulator is powered from the DC voltage output of CR1. The
regulator is comprised of transistor Q1, inductor L2 located on the generator controller
assembly (connected at P1), output filter capacitors C10, C11 and L1. Q1 is turned off
and on by the pulse width modulator in voltage regulator U2. The oscillation frequency of
U2 is 20 KHz. and is set by R23 and C19. Voltage feedback to U2 is provided by voltage
divider R6, R9 and R10. Current sense resistor R1 provides an indication of the
instantaneous current through FET Q1 to PWM U2 which removes the drive from the
base of Q1 on a pulse-by-pulse basis for current limit control. The basic idea of this
circuit is to charge up the inductor L2 and then collapse the field and direct the boosted
voltage ( 225V - 235V) thru CR2 to the output fuse F1 (located on the generator
controller assembly) and the battery packs.