Hospira LifeCare XL Series, Техническое и сервисное руководство

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4.2 ELECTRONICS OVERVIEW
Technical Service Manual 4 - 3 430-00587-008 (Rev. 2/05)
U2 configuration allows DC voltage at pin 9 (ERR+) to equal the peak voltage across resistor
R9. DC voltage controls the delivered power through transformer T2 to regulate the output
voltage. Voltage at U2-9 is limited to +1.25 VDC so that peak current through transistor
Q1 is limited to approximately 2 amperes (A). This limit constitutes the output short
protection.
Optocoupler U3 is part of the main regulation loop; it provides the UL-544 isolation barrier.
Resistor R61, diode CR5, and capacitor C6 provide protection from T2 windings short by
applying the higher voltage across resistor R9 to the U2 inhibit input. C6 and the input
impedance at U2-4 determine the low hiccup frequency in the event of a T2 winding short.
Diode CR3 and the clamp winding of transformer T2 provide intermediate energy transfer
to capacitor C3 and limit the peak voltage across transistor Q1. At AC (mains) power-up,
capacitor C12 provides delayed timing to permit the voltage potential at U2-14 (Vcc) to
reach its minimum level.
Diode CR11 and capacitors C23 and C24 rectify the transformer T2 voltage to create the
main DC voltage source (+BUSS) for the infusion system. Diode CR10, resistor R23, IC
U4, and capacitor C19 constitute a sec12 VDC control loop for protection in case
of primary loop failure. Diode CR12 and capacitor C25 create a feed-forward converted
negative voltage across capacitor C25 to switch transistor Q9 on through resistor R57 and
diode CR14. The Q9 output, housekeeping DC (HKDC), provides the necessary voltage to
power both the main regulation loop and the charger circuitry. HKDC is at ground potential
when AC (mains) is off and CR12 blocks unnecessary battery power drain. Resistors R58,
R59, and R60; capacitors C30, C31, and C32; and IC U9 filter HKDC and create a stable
+2.5 VDC reference voltage (F2.5V).
Resistors R21, R39, R44, and R45; capacitor C27; and components U8B and U3 constitute
the main control loop. Transistor Q7, resistor R42, and diode CR9 eliminate latch-up at
AC (mains) power-up by enabling voltage regulation only after +BUSS r9 VDC.
4.2.1.2
VOLTAGE REGULATOR CIRCUITRY
The primary function of the voltage regulator circuitry is to provide constant DC
level output. The motor voltage (VMOT) regulator circuitry (U8A, Q5, Q4, and
associated passive components) provides a co9.35 VDC output when
AC (mains) is on. Transistor Q2 remains forward-biased by HKDC through diode
CR8 and resistors R11 and R12. While Q2 remains on, transistor Q3 is disabled to inhibit
POWERHOLD and SPSTIN (single-pole, single-throw in) effect on the VMOT voltage
regulator.
When AC (mains) is off, Q2 is disabled. If battery operation is required, Q4 is turned on
momentarily by the SPSTIN signal and permanently by POWERHOLD. Since Q2 is off, Q4
switches the battery voltage through the VMOT circuitry to supply voltage to the necessary
circuits, including the +5 VDC regulator U5. IC U5, the +5 VDC low-drop voltage regulator,
powers most of the digital circuits in the infusion system.
115 V