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Improved Current Share Test for Power Supplies

IP.com Disclosure Number: IPCOM000201732D
Publication Date: 2010-Nov-19
Document File: 4 page(s) / 66K

Publishing Venue

The IP.com Prior Art Database

Abstract

This is an improved method for testing current share circuits on power supplies and voltage regulators during manufacturing test. This method ensures that the units are tested to the full operational range of the current share circuits and minimizes manufacturing escapes and false failures.

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Improved Current Share Test for Power Supplies

Background/Problem Definition


Current sharing is defined as sharing a common load equally amongst two or more devices that supply power to a common load. It is desirable for this load to shared equally by each individual device. Many methods exist to force the load to be equally shared, this patent describes an improved method of testing the current share circuits.

If the current share circuits are not sufficiently tested at the time of manufacture, certain combinations of units could cause possible field failures.

A key element to load sharing between two or more power supplies is the regulation point of the individual power supplies that are sharing the load. Without circuits to force the current to be equally shared between the power supplies, the power supply with the higher output voltage will source more current. Since in many power supply applications it is necessary to independently change the power supply voltages of each device, these current share circuits are essential to ensure the load remains equally shared amongst the individual power supplies.

Typically, these current share circuits are designed to ensure the load is shared equally as long as the voltage difference between the power supplies does not differ by more than a specific level or tolerance.

See Figure 1: Definition of Variables.

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Statement of the Issue


Current share circuits are designed to force the Voltage Regulation Modules (VRMs) to share the load current equally as long as the voltage difference between the individual VRMs does not exceed specified regulation tolerance band. In Figure 2, a traditional current share test would start with VRM1 and increase the output voltage by ½ the tolerance band and decrease the output voltage of VRM2 by ½ the

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tolerance band (1/2 tolerance band = x). VRM1 is considered the master and VRM2 is considered the slave. If the current share circuits are operating properly, each VRM should be supplying 50% of the total output load even though the output voltages are skewed due to the influence of the current share circuits. If each VRM is assumed to be regulating at the nominal output voltage before the test, this is a good method to test that the current share circuits are operating properly. If the c...