7
Start-up and shut-down
The following description refers to each of the RCB1200 power supply primary section and its relative output modules, unless it
is explicitly stated otherwise.
Each input module operates from a universal input voltage range and start automatically upon application of adequate AC
mains voltage (>84 V
RMS
). After a short delay, the global “+5V bias” supply starts and the “ACOK” signal goes high to
indicate that the mains voltage is present and input stage is operating correctly. Once the “ACOK” signal is high, the output
modules turn on and deliver power to the application loads. The “Power Good” signals will indicate that the output voltages are
within specification. The diagram below shows the normal start-up / shut-down sequence and gives typical timings.
Typical timing values:
t
1
= 300 ms, t
2
= 50 ms, t
3
=
25 ms, t
4
= 15 ms, t
5
= 5 ms (minimum), t
6
= 100 ms
When the AC mains voltage is removed, the internal hold-up capacitors will supply power to the load for typically 20 ms (t
4
+t
5
)
at maximum power. The “ACOK” signal will go low at least 5 ms before the output voltages fall below the power good
threshold level (t
5
). This allows the application to prepare for the impending loss of power. The “+5V bias” supply will remain
on for typically 100 ms, after the output modules have turned off.
Hold-up
For short line disturbances (<20 ms), the output voltages will not be affected*. However, the “ACOK” signal may still go low to
warn that there is an impending loss of output power. The “ACOK” signal will return to the high state once the unit has
recovered from the disturbance.
*
Outputs that are adjusted above the hold-up voltage as detailed in their respective datasheets, may experience a dip in voltage but never
below the hold-up voltage specified.
Idle power
The idle power of the RCB1200 PSU is determined by both the input stages of each section and the input stage of each
assembled output modules.
In the worst case where all modules are connected and enabled, the unit typically requires 56 W with no output load.
To reduce the idle power, the output modules can be disabled using the global inhibit (GINH) pin in each connector of their
correspondent section.
With all the outputs disabled, the unit typically requires less than 42 W.
Over temperature protection (OTP)
Each of the RCB1200 input stages is protected from excessive temperature by means of various internal sensors. In case the
temperature limit is exceeded in one section or both, the same section or both may latch off, with no “ACOK” warning. To re-
enable the whole unit operations, the AC mains must be disconnected for approximately 2 minutes.
I
NPUT
M
ODULE
O
PERATION
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