Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
2000-02-01
2001-05-22
Riley, Shawn (Department: 2838)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C363S147000
Reexamination Certificate
active
06236582
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of controllers for power supply devices. More particularly, this invention relates to controllers having a low pin count for sharing a load among more than one power supply.
BACKGROUND OF THE INVENTION
It is known that more than one power supply can be used to provide power to a common power bus. Care must be taken to avoid having one circuit attempt to provide all the power. Such a condition could cause that circuit to fail. For example,
FIG. 1
shows circuit for a Unitrode UC1907, UC2907 and UC3907 integrated circuit. The Unitrode approach allows multiple power supply modules to be coupled together in parallel. Each of the parallel power supply module only supplies a proportionate share of the total load current. A current from each power supply module is sensed. The controller determines which of the power supply modules would normally have the highest current value and designates it as the master. The power supply module with the highest current is the one that is most likely to fail first. Upon determination of the master module, the other modules are adjusted have provide current within 2.5% of the current value of the master.
This Unitrode approach requires a sixteen pin package to provide sufficient inputs and outputs to control the power supply modules. It is well known that the cost of an integrated circuit is proportional in some measure to the number of these so-called I/O pins. As such it is desirable to reduce the number of pins.
SUMMARY OF THE INVENTION
The present invention is for an eight pin load current share controller. Unlike the prior art, the load share controller of the present invention detects the power supply module having the lowest supply current. That lowest supply current power supply module is selected to be the system master. Because it has the lowest supply current from among other similar power supply modules, the system reliability is enhanced.
In addition, because of the architecture of the load share controller, the devices in the system can be hot-swap capability. An output voltage loop amplifier includes an opto-coupler driver. The voltage loop amplifier compensation is compatible with conventional TL431 shunt regulators. This allows a power supply system to be implemented according the advantages of the present invention with minimum effort.
REFERENCES:
patent: 5428523 (1995-06-01), McDonnal
patent: 5757634 (1998-05-01), Ferens
Haverstock & Owens LLP
Micro Linear Corporation
Riley Shawn
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