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Browse Prior Art Database

Bulk Supply Supervisory Circuit

IP.com Disclosure Number: IPCOM000120710D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Barbour, ER: AUTHOR [+3]

Abstract

Disclosed is a sense circuit for providing a "power good" level that is used to control safe operation of a power conversion circuit from a line-rectified DC bulk power source. (Image Omitted)

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 83% of the total text.

Bulk Supply Supervisory Circuit

      Disclosed is a sense circuit for providing a "power good" level
that is used to control safe operation of a power conversion circuit
from a line-rectified DC bulk power source.

                            (Image Omitted)

      The circuit provides adjustable hysteresis at upper and lower
limits, to avoid erratic converter operation as the borders are
crossed from either side.  It contains its own power supply, and this
guarantees proper operation of the comparator U1 far beyond the
borders of the range acceptable to the supervised converter.

      "Voltage good" is indicated by U1 pin7 open.  Voltage outside
this range is indicated by a VCE-sat level at this pin.  R4, R5, Z1
provide sense circuit power, with R4/R5 doubling as overvoltage sense
divider.  Undervoltage is sensed by R1/R2 and compared with a
reference voltage developed across R6/R7/R8.

      When U1 section A trips due to undervoltage, R3 modifies the
sensed voltage to an even lower level (hysteresis function).  The
changed output state U1 pin1 trips section B, bringing pin7 to a
VCE-sat level.  Both comparator sections flip back to provide a
"good" level upon return of the bulk to a higher than trip-out
voltage.

      At bulk overvoltages, the voltage drop across R5 increases
beyond the breakdown voltage VZ2 and Q1 is turned on.  D1 clamps Q1
collector voltage to VZ1 plus one diode drop, and the reference
voltage at...