9/15/06
888-2586-001
4-55
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
4.8.6.2
PA Power Supply Discharge
When the PS_DISABLE signal goes high, all of the SCR taps are disabled and the
DISCHARGE signals at J1-7 and J2-7 go low. This activates the PA discharge circuits
on the rectifier boards, which allows a quick and safe discharge of the PA supply.
4.8.6.3
Power Supply Standby Mode
Under certain circumstances, such as RF Mute, the power supplies will be placed in
standby mode via the signal PS_STANDBY. This signal comes from the Master
Controller and both PA Controllers. PS_STANDBY shuts off all the DRIVER signals
which deactivates all of the SCR taps on the power supplies. However, it does not
activate the discharge circuit. This allows the filter capacitors to maintain charge and be
ready to supply power at a moments notice without having to go through the Soft-Start
sequence again. However, the capacitors will bleed down slowly if the standby mode is
maintained. To keep the voltage within reasonable limits, the PS Controller will activate
the Soft-Start circuit if the PA voltage drops below 42Vdc and shuts it off when the
voltage is above 52Vdc. The PS Controller will maintain charge in this manner until the
PS_STANDBY signal goes low, and the power supplies are fully active again or shut
off by the PS_DISABLE signal.
4.8.6.4
Discharge Protection Circuit
The discharge protection circuit protects the power supply and the discharge circuit
components from a failure in the discharge circuit. Specifically it protects against a
short which would cause the discharge resistor to be “In circuit” when the power supply
is activated.
A sample of the voltage across the discharge resistor from each supply is sent to the PS
Controller at J1-20 and J2-20. If the voltage is more than 30Vdc, the comparator will
trip, and the output at U1-1 or U1-2 will go LOW. The fault signal 1_DISCH_SAMPLE
or 2_DISCH_SAMPLE is then sent to U9-2 or U10-2 where it is buffered before
reaching the micro-controller. The PS Controller would then shut down the power
supply. The detection circuit contains hysteresis to prevent false triggering.
4.8.6.5
RESET
There is a RESET line from the Life Support Board which is monitoring the +20Vdc
from the regulators on the Rectifier Boards. This is basically monitoring the Low
Voltage Power Supply. If the voltage falls below a set threshold, U37 on the Life
Support Board generates the RESET (active low) which is sent to all of the controller
boards (Master, PA and PS). On the PS Controller this RESET clears U2 and U3, which
brings their outputs low. This deactivates all of the DRIVER signals, disconnecting all
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