Browse Prior Art Database

Servo Control of Analog Power Supplies via a General Purpose Interface Card

IP.com Disclosure Number: IPCOM000104387D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 174K

Publishing Venue

IBM

Related People

Grant, DA: AUTHOR [+2]

Abstract

Disclosed is the concept of a universal printed circuit (PC), capable of fast personalization into many General Purpose Interface (GPI) card types, used to test analog production cards. A circuit embodiment using the concept is described for VDU analog cards under test (CUT)s with a single power rail that is expandable into multiple power rails without altering the test rig. A novel visual indicator of test resultss is included together with power faults protection.

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Servo Control of Analog Power Supplies via a General Purpose Interface Card

      Disclosed is the concept of a universal printed circuit (PC),
capable of fast personalization into many General Purpose Interface
(GPI) card types, used to test analog production cards.  A circuit
embodiment using the concept is described for VDU analog cards under
test (CUT)s with a single power rail that is expandable into multiple
power rails without altering the test rig.  A novel visual indicator
of test resultss is included together with power faults protection.

      Advantages over conventional hand wired interfaces, are:
reduced cost and turn around of GPIs and increased speed of testing,
due to concurrent operator adjustment of power supply (PS) voltages
while forcing a constant voltage from the test rig.

      A control system is used as a "bed of nails" card tester for
closing the feedback path of a switch mode power supply indepedently
of the display circuitry which normally presents a load at the
secondary winding of the supply.  This control system enables the
desired output voltage of the PS to be manually set during functional
testing regardless of whether a fault exists elsewhere on the CUT.

      A GPI card has been devised to meet the demands for functional
test of complex analog cards used in monitor and display products.
To reduce test time and to test cards at all, it is necessary to
connect external circuits to the CUT.  Traditionally these circuits
are fabricated by test engineers developing the test, using
prototyping boards, Fig. 1.  As the amount of external circuitry
required is considerable, a decision to design a custom printed
circuit board (PCB) was made with the objective to make it easy to
use the new GPI card in any functional test fixture and to test any
analog monitor card, as shown in Fig. 2.  Advantages over the
hand-built prototypes are that PCBs can be quickly manufactured by
outside vendors saving test department man-hours.  As the PCB is
general purpose, across the range of functional testers and monitor
cards, it can be partially populated and remain general purpose.
Only a few resistor/capacitor values change for use with different
monitors.  Replacement PCBs can be held at the card assembly point so
that a faulty card can be replaced quickly with less down-time on the
tester.  The PCB is more reliable in operation than a wired-up board,
because of mechanical robustness and the care taken to minimise the
likelihood of damage to card and tester if flashover occurs on the
CUT.

      The new GPI card contains a video waveform generator, to test
video circuits for gain, linearity and rise/fall times.  Also
contained are VSYNC and HSYNC identical redrive circuits, each with
one 50 ohm TTL input and three 50 ohm TTL outputs.

      V Synch and H Synch Redrive are two 50 ohm impedance inputs
into the GPI card via 50 ohm connectors.  They are each buffered by a
74128, split, and output...