Crown MARCO-TECH 5000VZ - Soft-Start Operation Details; C120 Discharge by Protection Signals; U701 A Output Control; Opto-Triac U700 Activation

Notes
Note: Any protection sign$Uviíhin the amplifier which is t¡a^<á to shut it
down will discria.rg^t'his capacitor (C1 20) immediately causing ihe'fe .
(K700) ítfefien.%ipon ciearance of such shut-down protection signa*
the ch ¿( ¿e w;" ':-ogin again with the same ramp effect and same delay.
Q POWER
VSWITCH
r>O
—O +15V
—O -15V
—O +24V
O -24V
TOCH 2 SOFT-START DRIVER
CH 1 FAN
CONTROL
Refer to the graphic of Soft
next page.
The ramped voitage
onthecapacitorC120
is also sensed by
Standby amplifier
U111B. Its unity gain
output is non-
inverting. Itdrivesthe
Soft-start op-amp
(U/01A) inverting
¡nput with its ramp to
control the rate at
which the field
developsinthetoroid.
On the non-inverting
inputto U701A isíhe
pulsed DC drive from
the U701B/Q708
pulse circuit. Jumper
JP1 may be set to 50
or 60Hz, but must be
set properly to nave
the correct pulse width
for soft-start. Pulse
width is determined by;
C717andeitherR7;;/
(50Hz) or R7^-'in
parallel wjg?!'R806
(60hU}>
It is the output of
U701A ihat really
controlsthe Soft-start.
•start waveforms on the
Soft-start block diagram. Note: DC
pulse stretching circuit shown in Low
Voitage Power Supply schematic cut-
away on page 11.
When the output of U701A goes low, the opto-triac device U700 turns
on. While on the input triac Q700 conducís. Positor R702 litnits peak
input current to the toroid to a máximum of 22A (with 120VAC mains).
U701A combines the sloped input from the C120 circuitry onthe main
module with the pulsed DC. As the portíon of time which the output of
U701Agoeslowincreases, the amountof time whereAC mains conduct
to the transformar (via Q700 and R702) increases until it remains on.
When the U111C PWR circuit times out, the relay closes bypassing the
current límiting soft-start circuit. Soft-start control signáis are shown in
at the top of the next page. The uppersignal isproducedby C120. At
time O the amplifier is off. At time 1: the power swiích is pressed (on).
At time 2: C120 has fully charged, the magnetic fields have built up in
the high voitage supply, and the main relay closes. At time 3: a
protective action occurs; note that the DC supply remains. At time 4: the
conditionclearsandtherestartbegins. Time5isakintot¡me2,andtime
22 - MA-5000VZ