Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific voltage responsive fault sensor
Reexamination Certificate
1999-10-05
2001-08-21
Huynh, Kim (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific voltage responsive fault sensor
C361S018000, C323S271000
Reexamination Certificate
active
06278597
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to over-voltage protection for power supplies. More specifically, the present invention relates to conditional over-voltage protection for redundant phase-shift converters.
A typical switching power supply has a switching stage, such as a pulse width modulator or phase-shift controller to regulate the output voltage of a power stage. Over-voltage protection is achieved by comparing the output voltage of the power stage to an internal over-voltage reference. When an over-voltage condition is detected, the switching is disabled which disables the power stage shutting down the output voltage.
In a redundant power system multiple power supplies are connected to a common bus to maintain availability of the bus voltage in the event of failure of one of the contributing supplies. An over-voltage condition of one power supply can raise the common bus voltage causing activation of the over-voltage protection of the other power supplies connected to the common bus.
In a low current redundant power system each power supply output is connected to the common bus through a diode, commonly referred to as an “OR-ing” diode. The “OR-ing” diode prevents each supply from sensing the over-voltage conditions of other supplies. An over-voltage bus reverse biases the diodes of the working supplies. Only the faulty supply is latched off by its over-voltage protection. Once the over-voltage condition is thus removed the remaining supplies resume normal operation.
In high current redundant systems it is not practical to use “OR-ing” diodes because of the severe loss of efficiency. All the supplies will sense an over-voltage fault in any supply and latch off causing unavailability of bus voltage.
SUMMARY OF THE INVENTION
Drawbacks and deficiencies of the prior art are overcome or alleviated by an over-voltage protection circuit for power supplies employing phase-shift controllers or the present invention. The power supplies typically comprise a redundant system for maintaining availability of bus voltage in the event of the failure of one of the supplies. The circuitry provides advantages in high power applications over prior art by overcoming the inefficiencies of connecting the supplies to a common bus through a diode. Additional circuitry eliminates the false shutdown of working power supplies. The present invention is embodied in circuitry that prevents the outputs of the phase-shift controller from switching when there is an over-voltage condition. The internal oscillator of the controller is halted whenever the error amplifier output goes low enough to drive the controller to 0% phase-shift.
The finite logic delays that cause unwanted sliver pulses are eliminated when there is no switching of the outputs of the phase-shift controller. Also, failure of one of the two switch drive circuits no longer causes an over-voltage condition. The phase-shift converter stops switching thus removing the energy source that caused the over-voltage condition.
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Covi Kevin R.
Seminaro Edward J.
Shevach Steven
Sorenson Dale F.
Cantor & Colburn LLP
Gonzalez Floyd
Huynh Kim
International Business Machines - Corporation
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