Mallinckrodt NELLCOR NPB-4000, Service Manual

Page: 181 / 219

15-1
SECTION 15: POWER SUPPLY - THEORY OF OPERATION
15.1 Overview
15.2 AC Mains Flyback Power Supply
15.3 Battery Charger
15.4 Buck Converter Operation
15.5 Power Devices
15.6 Miscellaneous Control
15.7 System Power Supply
15.8 Mains (AC) LED Operation
15.9 Power Supply Control Logic
15.10 Alarm Section
15.11 NIBP Pump Control
15.12 Safety Devices
15. POWER SUPPLY - THEORY OF OPERATION
15.1 OVERVIEW
15.1.1 Three Power Supplies
See Figure 15-1 and
Figure 15-2. The NPB-4000/C power supply, as shown in the block diagram,
consists of three power supplies and some control logic. The three supplies are:
AC Mains Supply - Accepts universal AC input power (90 - 264 volts
RMS, 47-63 Hz). Provides safety line isolation, and produces 18 volts
DC at 2 amps (36 Watts) for the Battery Charger.
Battery Charger - Accepts input from either an external DC source
(vehicle battery) of 10-16 volts DC, or from the output of the AC Mains
Supply (18 volts DC). Provides a tailored charging profile for the
NPB-4000/C lead-acid, 3-cell battery. Includes current limiting and
temperature compensated float voltage. Maximum output, 7 volts DC at
3.5 amps (24.5 watts).
System Power Supply - Accepts input from the internal NPB-4000/C
battery (5.4 to 7 volts DC) and produces regulated outputs of +12, +5,
+3.3 and -24 volts DC for NPB-4000/C system usage. Maximum total
output power is 25 watts distributed among the four outputs. This peak
power occurs only briefly during NIBP pump and printer operation.
Typical output power is about 8 watts.