Lp 647 Power Logic A (4008 B/S) - Fresenius Medical Care 4008 E Technical Manual

8.22 P.C.B. LP 647 Power logic A (4008 B/S)
8.22.1 Description
General notes
In order to save space, power logic has been divided in 3 components in the 4008 B/S:
– P.C.B. LP 647 Power logic A
– P.C.B. LP 743 Power control 2
– P.C.B. LP 744 Power control 1
Standby voltage generation
Via the transformer TR2, the rectifier GL1 and the filter capacitors C1, C3, C4, an unstabilized DC
voltage of approx. 15 V is supplied to the input of the linear regulator (1/T1). The connected
circuits are supplied by the stabilized output voltage of 12 V via the diode D3. In order that the
turnon logic can be supplied in case of power failure, a voltage of approx. 10 V is generated from
the battery voltage via the regulator IC13 and ORed to the output voltage of T1 via D2.
Power turnon logic
When the ON/OFF key on the front panel of the machine is pressed, a LOW level is applied to
IC4, pin 1, via X647A, pin 7. By means of the interconnected gates of IC4 and IC5, this causes a
rising edge at IC8, pin 3. The output of the FF (IC8, pin 1) becomes HIGH, and the power relay
RL3 is activated via T8. At the same time, the bistable relay RL4 is energized via the differentiator
C28, R3 and the transistor T10. Among others, this causes the contact RL4, pin 4 and pin 5 to
close, so that a voltage of approx. 10 V is available at X647A, pin 16, via the linear regulator
consisting of T6, R55 and ZD1, for generation of the audible power failure alarm.
To turn the system off, a high edge is applied to IC8, pin 11, via DI10. This edge is used to store
the level at input D (IC8, pin 9) (H level with the system turned on). At the same time, a time
function element for the turnoff delay starts to run (R54, C27). After approx. 1 sec, IC4, pin 6,
becomes LOW and IC6, pin 3, is supplied with HIGH level. This level can be read by the CPUs via
X647A, pin 22, and is provided as turnoff detection. After another approx. 150 ms, the second
time function element (R41, C26) has elapsed as well, and the system is turned off via IC8, pin 4.
At the same time, the differentiator C29 and R2 and the transistor T11 are used to energize the
bistable relay RL4, so that the audible power failure alarm is suppressed (contact 4/5 RL4).
Fresenius Medical Care 4008 4/09.03 (TM)
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