HP 3000 SERIES II System Service Manual page 185

HP 30311A Power Supply
Power Supply furnishes the input power and maintains the voltages to the memory system. The
amount of time the battery continues to furnish power depends on the condition of the battery and
the size of memory requiring power. Normally, the battery will furnish power for 40 to 90 minutes
before it discharges to a level that activates the undervoltage circuits and removes all power from
memory.
The power supply can be operated without the battery. However, no power will be available to the
memory system if AC power is removed from the HP 30310A Power Supply. When operating in this
mode, the battery status lights are disabled. A battery mode switch on the 30311-60003 Control
PCA must be set to operate without a battery.
B-27. BLOCK DIAGRAM DESCRIPTION. Figure B-4 is a block diagram of the HP 30311A Power
Supply. The figure shows the relationship with the HP 30310A Power Supply.
The +20 volt output of the HP 30310A Power Supply provides the charging power for the battery
pack and the input power for the +12.7, +12.0, and +5 volt regulators. The TEMP SENSE input to
the HP 30310A controls the output of the +20 volt line. The +20 volt output also supplies input
power to the +5 volt regulator and the control circuits.
Outputs of -3 and -5 volts are derived from a source voltage obtained from the +5 volt switching
regulator. Load current from the -3 volt line adds to the -5 volt load current so that a single
current limit on the -5 volt line protects both outputs. The maximum combined current for the -3
and -5 volt loads may be divided between the loads in any combination.
Over/under voltage detectors can disable the PSU (Power Supply Up) system DC power line, and
shut down the power supply by sensing the +12.0, +5, and -5 volt outputs for undervoltage. The-3
volt output is sensed for undervoltage to disable the +12.0 and +12.7 volt outputs, thus protecting
the memory array chips from lack of either -3 or -5 volt substrate bias. Overvoltage conditions
sensed on the +5 and +12.0 volt outputs cause the power supply to crowbar to protect the TTL
elements and memory array chips.
Indicators and controls that monitor and control HP 30311A operation are located on the System's
DC Control Panel and on the front panel of the HP 30311A.
B-28. DETAILED BLOCK DIAGRAM DESCRIPTION. The +20 volt output of the HP 30310A
Power Supply provides the power required for HP 30311A operation and the current to charge the
seven-cell lead-acid battery pack. The +20 volt output of the HP 30310A Power Supply is regulated
by the HP 30311A Power Supply controlling the DC input to its TEMP SENSE input terminal.
These connections may be seen in the detailed block diagram of the HP 30311A, figure B-5.
B-29. Battery Pack. When the power switch is ON, the battery pack is connected to the +20 volt
line through Fuse· Fl. While the switch is ON, the battery is kept at the proper float voltage. Float
voltage is defined as the voltage applied. to keep the battery fully charged. The battery charge
voltage is temperature dependent and the float voltage is nominally +16.45 volts at room
temperature. A temperature sensitive resistor located in the battery pack senses the temperature
variations and varies the potentials of the battery charge voltage divider. This change in potential
controls the battery voltage regulator output that is connected to the TEMP SENSE terminal of the
HP 30310A Power Supply. A decrease in battery temperature produces a control voltage from the
battery voltage regulator that causes the +20 volt line to increase to the correct float voltage for
JAN 1977 B-23