LifePak Power Control Description

BATT CHRG Indicator

A battery-charging LED signal illuminates the front panel BATT CHRG indicator whenever the ac power is connected to the instrument and the rear panels main power switch is on. An interlock in the battery harness prevents the indicator from lighting if the battery is not installed.

Power Conversion PCB Assembly (803724)

The Power Conversion PCB contains circuitry for power on/off switching, additional voltage generation and monitoring, energy storage capacitor charging, and defibrillation energy transfer. Refer to Figure 1-3, page 1-10.

Power Control

The Power Control circuit regulates battery voltage for the circuits which control instrument operation. The circuits directly affected by the Power Control circuit are: Switching Power Supply, Logic Power Monitor, External Control Input, Low Energy Charge Rate, and Energy Storage Capacitor Charger circuits. The Front Panel ON momentary pushbutton provides the start-up signal for the Power Control circuit. When the power switch is first pressed (turning power on), V BATT passes to the gate of Q11, causing Q 11 to conduct, which in turn causes Q10 to conduct. A portion of V BATT is held on the gate of Q11 by R52, which keeps Q10 conducting. During this time the PWR SW MONITOR line is low and the Power Control circuit provides the SWBATT voltage for the rest of the Power Conversion PCB Assembly circuits.

When the power switch is pressed a second time (turning power off), V BATT is divided by R108 and R109, forward-biasing CR44 and switching the PWR SW MONITOR line high. The System microprocessor reads the low-to-high transition and activates the Logic Power Monitor circuit, disabling the Power Control circuit. The functional integrity of the Power Control circuit may be confirmed by monitoring two pins on the test connector: R60 (connects to the gate of Q 10) and R57 (connects to the gate of Qil).

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