US 6,211,726 B1Granted

Low voltage, high-current electronic load

AssigneeInternational Business Machines Corporation

InventorsTimothy Charles Daun-Lindberg, Michael Lee Miller

Life of this patent

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Abstract

An electronic load circuit provides a variable load current at a high amp level, at low-voltage so that contemporary voltage supplies of perhaps 1.5V may be tested. This load is used for testing voltage supply circuits for computer systems or the like. A number of parallel, high-current MOS transistors of low internal resistance are used as a constant-current load. Current in the load path is sensed by a sensing resistor connected in series with all of the transistors, and this resistor has a value of the order of the effective internal resistance of the source-to-drain paths of the parallel transistors and connecting links to these transistors via a circuit board, connector terminals, etc. The sensing resistor provides a feedback signal to a high-gain op-amp, the output of which is compared to a variable input signal to produce a gate drive voltage for the transistors. The input signal may be varied to simulate the variable loading exhibited by a computer system. It is important that the current sensing arrangement including the sensing resistor is of low resistance.

Claims12

Dependent claims

A variable, high-current, low-voltage, load circuit for testing a voltage source, comprising:

a plurality of high-current transistors having source-to-drain paths connected in parallel between a pair of terminals and a test load, said transistors having gates separately connected to an input node by resistive means, each of said high-current transistors and connecting paths to said transistors having an internal resistance of a low value;
a sensing resistor connected in series with all of said source-to-drain paths having a resistance no greater than a value of about the order of said internal resistance of said high-current transistors and connecting paths, to thereby provide a feedback voltage responsive to current from the voltage source which passes through said test load;
a first high-gain op-amp responsive to said feedback voltage to produce an amplified feedback voltage related to said load current;
a second high-gain op-amp connected as a differential circuit comparing said amplified feedback voltage with a variable input voltage signal and producing a drive voltage to produce a current in said transistors related to the variable input voltage and responsive to said feedback voltage;
and
said drive voltage being connected to said input node.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/345,607Filed 28 Jun 1999
Granted: 3 Apr 2001
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01R 31/40
Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by…
G11C 5/147
Power supply arrangements , e.g. power down, chip selection or deselection, layout of wirings or power grids, or multiple supply levels: voltage…
G11C 29/02
Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation: detection or location of defective…
G01R
Measuring electric variables