LIFEPAK 20/20e Defibrillator/Monitor
Device Description
Functional Description
(continued)
A04 Therapy PCB
(continued)
■
H-Bridge
— The H-Bridge is a patient-isolated circuit that creates the
biphasic defibrillation waveform. A combination of silicon controlled rectifiers
(SCR) and insulated gate bipolar transistors (IGBT) are used to place a
positive-oriented defibrillation pulse across the patient load, followed
immediately by a negative-oriented defibrillation pulse. The defibrillation
pulse is delivered through the relay and W01 Therapy Connector assembly
to the external therapy cable on the outside of the device.
■
Pacer
— The pacer is a patient-isolated circuit that creates the pacing
waveform. A portion of the H-Bridge circuitry is used to support the pacer by
providing energy from the A13 Defibrillation Capacitor. A current drive is
used to control the amount of current provided to the patient during pacing.
■
Relay
— The relay provides patient isolation from the pacing and
defibrillation circuitry when not in use. The relay is closed when the pacing
current is set above zero and stays closed until the pacing current is set back
to zero.
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