ZOLL PD 2000 - Page 73

SERVICE MANUAL
Discharge
A discharge is initiated by depressing both DISCHARGE buttons on the
paddles or on the Multi-Function Cable. This provides voltage to the
patient discharge relay coil and notification to the CPU through the
PADMON signal. The CPU then controls activation of the patient
discharge relay. There are two exceptions to immediate discharge:
operating in SYNC mode and operating with the Multi-Function Cable.
In SYNC mode the discharge occurs near the peak of the ECG QRS wave.
With the Multi-Function Cable, an open circuit test is first performed. If
an open circuit is detected, the discharge is not allowed and the message
LEAD FAULT is displayed on the CRT.
Energy delivered to the patient goes through a wave shaping inductor as
specified by the AAMI Standards.
When the patient discharge relay is deactivated and the high voltage
capacitor returns to system side, the safety relay is closed to internally
dissipate any remaining energy .
If the PD™ 1400-series is in the self-test mode, the energy is-delivered
internally. The microprocessor calculates the actual delivered energy
from the current waveform and displays a TEST OK message on the CRT,
if the criteria for a "self-test" have been met. If the criteria are not met, a
TEST FAILED message is displayed.
DETAILED CHARGING OPERATION
Initiating High Voltage Capacitor Charging
The CPU controls several signals that are used to initiate charging the
high voltage capacitor. Once the stimulator board has received the
signals, the board will charge the high voltage capacitor with a Pulse
Width Modulator (PWM) controller (U1). The CPU will continue to
monitor the changing VCAP signal to ensure proper charging operation.
All the following conditions must be satisfied before the high voltage
capacitor can be charged.
1. XSAFE hi No safety hazard detected
2. XPWR_RESET hi Power on
3. P/XD low Defib mode
4. XSAFREL low Safety relay open
5. XPATREL hi Discharge buttons not active.
6. XPWRENBlow PWM enabled
IV-14