Agilent Technologies 6012B Service Manual page 103

Remote Trip. A negative-going edge applied to terminal J3-30 (
supply, reducing the output voltage to near zero. For minimum pulse duration and timing considerations with respect
to REMOTE RESET , see Table A-1. The following paragraph provides a brief circuit description (see schematic
diagram and Figure A-8).
A negative going edge at
TRIP/RESET latch (U5A) low. This sets terminal J1-13 ( INHIBIT ) low, thus inhibiting the Pulse Width Modulator
of the power supply. It also lights the unregulated indicator on the front panel and generates an unregulated signal
from the opto-isolator U3.
The low signal generated by the Trip/Reset Latch is also coupled through opto-isolator U2 and appears at J3-17 as
an OVERVOLTAG status signal. This signal does not affect the state of the power supply's OVP circuit. E
Remote Reset. A negative-going edge applied to terminal J3-29 (
initial state following a system-initiated shutdown or an OVP shutdown caused by a temporary over voltage
condition. For minimum pulse duration and timing considerations with respect to
under Remote Control. The following paragraphs provide a brief description of this circuit (see schematic diagram
and Figure A-8).
A negative-going pulse applied to terminal J3-29 (
One-Shot U13A then triggers and resets the TRIP/RESET latch output high. This sets terminal J1-13 ( INHIBIT )
high, thus enabling the power supply's Pulse Width Modulator.
The REMOTE RESET signal will also reset the power supply OVP circuit in the event that an overvoltage
condition has shut down the supply. When a
will produce an OV CLEAR pulse at terminal J1-12. The
low thus, resetting the OV FLIP FLOP. When this occurs the output of A2U24D goes high and simultaneously
causes the front panel OV LED to turn off and the OV signal (J1-6) to go high. The
U4B also goes high and enables the PWM of the power supply .
Note
By observing the
a reset pulse to
returns and
shutdown. If the output takes about one second to return, this indicates that the output voltage had
exceeded the OVP trip point. If the OVP circuit trips continually, check the load and/or the trip
point setting.
Alternate Method of Remote Control. The
remote shutdown. By maintaining a low logic level at this input, the supply's output will be inhibited until
REMOTE INHIBIT is returned to its initial high state. The following paragraph provides a brief description of this
circuit (see schematic diagram and Figure A-8).
A low logic level applied to terminal J3-31 (
U4B to inhibit the power supply's (PWM) Pulse Width Modulator. If jumper W1 is used (see Figure A-8) while a
REMOTE INHIBIT signal is applied, an
OVERVOLTAG thus, indicating the power supply shut down. E
REMOTE TRIP coupled through opto-isolator (U9) causes one-shot U13B to set the
REMOTE
REMOTE
OVERVOLTAG status indicator or the power supply's output while applying
REMOTE RESET
OVERVOLTAG goes high immediately, this indicates a controller-initiated E
REMOTE
REMOTE
OVERVOLTAG signal will appear at terminal J3-17
REMOTE TRIP
REMOTE RESET
RESET ) is coupled through opto-isolator U10.
RESET signal is present, ONE SHOT U13A goes low, this
OV CLEAR pulse will cause the output of A2U2 to go
E
, the user can determine the cause of shutdown. If the output
INHIBIT input, J3-31, provides an alternate method of
INHIBIT ) is coupled through opto-isolator U8 and causes
E
) will shut down the power
) will return the supply to its
REMOTE TRIP see Table A-1
OVERVOLTAG signal to E
103