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Positive Latch-Off Power Supply Over-Voltage Circuit

IP.com Disclosure Number: IPCOM000100484D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Miller, BD: AUTHOR [+2]

Abstract

Disclosed is a power supply output over-voltage protection circuit. This over-voltage circuit is a permanent latch which does not allow the power supply to restart. There are cost, performance and reliability advantages to the circuit.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Positive Latch-Off Power Supply Over-Voltage Circuit

       Disclosed is a power supply output over-voltage
protection circuit.  This over-voltage circuit is a permanent latch
which does not allow the power supply to restart.  There are cost,
performance and reliability advantages to the circuit.

      Existing over-voltage protection circuits do not have permanent
latches.  They function by setting a latch that is powered by the
high-voltage DC supply.  This is done by sensing the voltage either
at the output or a primary sense level and then either tripping a
latch directly or tripping a crowbar SCR which sets a latch.

      There are several disadvantages of existing over-voltage
circuits, including complexity (both design and operation), board
area, cost (components, board area, design time), the possibility of
other necessary circuits being added (i.e., primary over-current
latch) and relative low reliability (due to the quantity and type of
components).  Conventional protection circuits do not permanently
disable the power supply.

      The new over-voltage circuit operates by opening the main power
path in the primary side of the power supply. When an over-voltage is
detected, the power semiconductor is held on.  This causes the power
transformer to saturate, resulting in a very large current through
the main power path.  This causes a component, such as the fuse,
inrush resistor, or power semiconductor, to be damaged.  This results
in a permanent latching condition for the power supply.

     ...