Remote Trip. A negative-going edge applied to terminal J3-30 ( REMOTE TRIP ) will shut down the power 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 REMOTE TRIP coupled through opto-isolator (U9) causes one-shot U13B to set the
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 OVERVOLTAGE status signal. This signal does not affect the state of the power supply's OVP circuit.
Remote Reset. A negative-going edge applied to terminal J3-29 ( REMOTE RESET ) will return the supply to its 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 REMOTE TRIP See Table A-1 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 ( REMOTE RESET ) is coupled through opto-isolator U10. 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 REMOTE RESET signal is present, ONE SHOT U13A goes low, this will produce an OV
CLEAR pulse at terminal J1-12. The OV CLEAR pulse will cause the output of A2U2 to go 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 OVERVOLTAGE signal to U4B also goes high and enables the PWM of the power supply .
| | | | | | | |
Note | By observing the | | | | status indicator or the power supply's output while applying a reset |
OVERVOLTAGE |
| pulse to | | | , the user can determine the cause of shutdown. If the output returns and |
| REMOTE RESET |
| | | goes high immediately, this indicates a controller-initiated shutdown. If the output |
| OVERVOLTAGE |
| 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 INHIBIT input, J3-31, provides an alternate method of 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 ( REMOTE INHIBIT ) is coupled through opto-isolator U8 and causes 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 OVERVOLTAGE signal will appear at terminal J3-17 OVERVOLTAGE thus, indicating the power supply shut down.
