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  Uniform converter output voltage distribution power systemUSPTO Application #: 20060273770Title: Uniform converter output voltage distribution power system Abstract: A uniform converter output voltage distribution power system evenly controls the individual output voltages of DC-to-DC parallel-input series-output connected converters using a uniform output voltage distribution controller including a generator for generating respective error signals from the converter output voltages using a common distribution reference signal for providing respective converter control signals connected to the converters through respective shared-bus controls for evenly distributing the power delivered by the converters that are shared-bus current-mode converters for preferably providing high output voltages. Employing a common regulation control signal, the controller can also provide system output voltage regulation, system input current limiting, proportional-voltage control, relaxed voltage uniformity, and fault-tolerant power control. (end of abstract)
Agent: Carole A. Mulchinski M1/040 - El Segundo, CA, US Inventor: Kasemsan Siri Related Keywords: bus, converter, error, fault-tolerant, power control, reference signal, signal USPTO Applicaton #: 20060273770 - Class: 323272000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060273770. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The invention relates to the field of power systems. More particularly, the invention relates to uniform voltage distribution of parallel-input series-output connected converters in power systems. BACKGROUND OF THE INVENTION [0002] Power systems with parallel-inputs and parallel-output configurations are used to provide electrical power using DC-to-DC power converters. In such systems, uniform current distribution control is solved by using manufacturer-provided parallel control ports with user-developed shared-bus control topology. Using shared-bus configurations, a control voltage commands the parallel-connected converters to operate as voltage-controlled current-sources, that is, as current mode converters where each converters is controlled as a voltage controlled current source. The current-mode and shared-bus approach to uniform current distribution is well known, particularly for parallel-input parallel-output connected power converters. [0003] Another conventional practice in power systems, is to used the DC-to-DC converters in parallel-connected configurations where the converters are specified to be identical for uniform power distribution amongst the converters. In stand-alone configurations, the converters are often connected to the same input voltage source while the outputs of the converters independently distribute output voltages to individual loads. One problem with stand-alone converters is that internal component variations result in undesirable non-uniform output voltage distribution despite the parallel connection of the converters to the same input voltage source. The stand-alone converters need to have electrical isolation between the converter inputs and outputs to enable the outputs to be series connected. When these stand-alone converters are connected in a parallel-input and series-output configuration, non-uniformity in the output voltages of the converters results with uneven power distribution such that some converters may be overstressed while the remaining converters are not. Uneven distributed voltages can cause the converters to lose stability and can cause one or more of the converters to deliver an excessive portion of the output power across a common load. With excessive uneven power distribution, system reliability degrades mostly due to the result of thermal overstress to the converters that contribute a greater portion of the output power. Connecting the outputs of the converters in series cannot avoid uneven power distribution. Uneven power distribution occurs as a result of internal component mismatches among the series-output connected converters. The problems associated with non-uniform power distribution are not entirely eliminated even with external controls that conventionally do not have dedicated closed-loop regulation for output voltage distribution. [0004] When parallel-input series-output converters are operated in a current mode, mismatches in component values can still lead to uneven power distribution as well as different modes of operations. Among the nearly identical parallel-input and series-output connected converters, some converters may operate in over-current protection mode and some converters in normal output voltage regulation mode while the remaining converters operate in over-voltage protection mode. A problem with parallel-input and series-output connected converters is that the output voltages are not all tied to ground, and hence the converter output voltages cannot be directly used by controllers to separately and precisely regulate each of the converters. A problem with existing parallel-input and series-output converters power system is the inability to precisely control the proper distribution of power. Without precise power distribution among the converters, voltage output regulation is degraded and undesirable uneven input current sharing and power distribution can result. Subsequently, undesirable interactions among interconnected converters may exist and can result in regulation instability as well as overstress in one or more of the parallel-input and series-output connected converters. One problem of parallel-input and series-output power systems using multiple converters is the output voltage of each converter is not the same, and hence is non-uniform resulting in instability and uneven power distribution, particularly during any transient start-up, step-line, or step-load transients. [0005] Another problem with parallel-input and series-output connected converter power systems is the lack of a properly unified control for uniform or proportional output voltage distribution for precise distribution of control signals to the converters so as to meet the control objectives for the system, such as, system output voltage protection and system input current-limiting while actively sustaining uniform or proportional output voltages of the converters at all times. The lack of proper control for proportional power distribution among non-identical parallel-input and series-output DC-to-DC converters and proportional-to-power output-voltage limits the use of a mix of converters that have different output voltage and power ratings in a parallel-input and series-output power system. These and other disadvantages are solved or reduced using the invention. SUMMARY OF THE INVENTION [0006] An object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system. [0007] Another object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system having proportional converter control. [0008] Yet another object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system having fault tolerance. [0009] Still another object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system having output voltage regulation. [0010] A further object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system having input line current-limiting. [0011] Yet a further object of the invention is to provide uniform output voltage distribution among parallel-input series output DC-to-DC converters in a power system having relaxed control where one of the converters has a non-uniform output voltage compared to the remaining uniform output voltage converters. [0012] The invention is directed to a uniform output voltage distribution power system with parallel-input series-output connected converters control by a uniform output voltage distribution controller for controlling the output voltage of each of the converters to be the same so that power contribution by the converters is even. The distribution controller particularly includes an error signal generator for generating error signals that are produced from the converter output voltages. Successive single-ended output voltage levels from successive converters are differenced for creating difference signals equal to the individual converter output voltages so as to reconstruct, in the error signal generator, the sensed converter output voltages relative to ground. The reconstructed converter output voltages can then be compared to a distribution reference signal for generating separate converter control signals for separate control and regulation of the individual converters. In the error signal generator, a common distribution reference signal is compared to each of the reconstructed output voltages for producing respective error signals. The error signals are used to then form converter control signals for the respective converters using a shared-bus control input (SBI) port of the converters for maintaining uniform output voltage distribution. The common distribution reference signal establishes the power distribution among the converters while the error signals are used to drive the respective converters toward the uniform output voltage distribution. In a proportion configuration, the distribution reference signal can be varied for each converter so as to provide proportional power distribution between the converters. In a relaxed-control configuration, one of the converters can be controlled by only either the output voltage regulation or the input current-limiting controller while the remaining converters are controlled by both the output voltage regulation or input current-limiting controller and the voltage distribution error signal generator. The overall controller is preferably adapted to concurrently provide system output voltage regulation or input current limiting while sustaining uniform distribution of the converter output voltages. [0013] The uniform output voltage distribution controller power system operates in a current-mode using shared-bus converters configured as parallel-input and series-output converters with improved stability and uniform output voltage distribution among the converters through output voltage distribution control. The power system can be expanded to a higher output voltage power system consisting of nearly identical converters that are designed to operate as either stand-alone converters or parallel-connected converters. The power system has minimized interactions among converters because the converters are separately controlled for eliminating transient oscillation during current sharing at the converter input. The power system can be adapted to further provide proportional control for converters that have different output voltage ratings. The power system can provide system input and output current limiting. The power system can provide output voltage regulation. The power system can provide relaxed control when one converter may not need to be directly controlled for the uniform output voltage distribution as the remaining converters that are tightly controlled for the uniform distribution. Fault-tolerant parallel-input series-output converters preserve uniform output voltages even though one or more converter may fail to produce an output voltage. These and other advantages will become more apparent from the following detailed description of the preferred embodiment. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is a schematic of a uniform converter output voltage distribution power system. [0015] FIG. 2A is a block diagram of a generalized uniform output voltage distribution controller. [0016] FIG. 2B is a block diagram of a relaxed uniform output voltage distribution controller. [0017] FIG. 2C is a block diagram of a regulated fault-tolerant uniform output voltage distribution controller. [0018] FIG. 3A is a block diagram of a generalized uniform output voltage distribution error signal generator. [0019] FIG. 3B is a block diagram of a proportional output voltage distribution error signal generator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Continue reading... Full patent description for Uniform converter output voltage distribution power system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Uniform converter output voltage distribution power system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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