Electric power conversion systems – Current conversion – Integrated circuit
Reexamination Certificate
1999-10-29
2001-03-13
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Integrated circuit
C363S071000, C363S065000
Reexamination Certificate
active
06201723
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to distributed power applications and systems, and more particularly, to a current sharing technique using DC-to-DC power modules suitable for use in such applications and systems where parallelability and current sharing are required.
BACKGROUND
The powering requirements of new computer and communications systems continue to require increased flexibility and performance. Increased system flexibility has resulted in increased interest in distributed power architectures. A fundamental requirement for distributed systems is module parallelability and current sharing.
Many different current share techniques have been suggested over the years to parallel multiple power supplies. In most cases, these schemes measure the current provided by each module, amplify it, compare it to the current form of other modules, and adjust the regulation voltage of its own module so as to minimize the difference in the output currents between modules. Many different variations of this technique have been suggested and implemented in industry. See Zhou, X., Peng, X., and Lee, F. C., “A high power density, high efficiency and fast transient voltage regulator module with a novel current sensing and current sharing technique”, IEEE APEC 99 Proceedings, pp. 289-294; Petruzziello, F., Ziogas, P. D., and Joss, G., “A novel approach to paralleling of power converters units with true redundancy”, IEEE PESC 90 Proceedings, pp. 808-813; Small, K. T., “Single wire current share paralleling of power supplies”, U.S. Pat. No. 4,717,8333, 1988; Jordan, M., “Load share IC simplifies power supply design”, High Frequency Power Conversion Conf. Proc., pp. 65-76, 1991; Jordan, M., “UC3907 load share IC simplifies parallel power supply design”, Application Handbook Unitrode, pp. 3-203-3-212 (U-129), 1997; Balogh, L., “The UC3902 load share controller and its performance in distributed power systems”, Application Handbook Unitrode, pp. 3-626-3-633 (U-163), 1997; Jamerson, C., Mullet, C., “Paralleling supplies via various droop methods”, High-Frequency Power Conversion Conf. Proc., pp. 68-76, 1994.
There are two widely used solutions of implementing current sharing modules in industry today. The first solution is the droop method. In this method, the system output voltage is allowed to droop as the load current increases, resulting in improved current sharing. The droop method works well if the initial set point of the different modules is relatively similar. However, there are systems which do not permit the voltage to droop.
The second solution, active current sharing, is generally used in these systems. In active current sharing, the individual current of each parallel module is measured, amplified, and compared to each other. Based on the result of this comparison, the module set point is adjusted to drive the difference between the output currents of each module to zero. Many different implementations of active current sharing are being used in industry today. Generally, active current sharing requires the use of several operational amplifiers.
Although the droop method and active current sharing are widely used in industry, each has disadvantages that involve either high cost, increased size, complexity, or decreased system performance. The droop method offers a simple and cost effective solution at the expense of system performance. Active current sharing, on the other hand, produces high performance but must be implemented with complex, costly, and power dissipating circuitry. Thus, what is needed is a cost effective and less complex current share circuit which does not decrease system performance nor significantly increase the physical size of the system.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a simplified current share circuit scheme for multiple power modules. The invention provides cost efficient and less complex circuitry than the prior art. The present invention may be adapted for use with power modules which are not designed for current sharing.
In one embodiment of the present invention, disclosed is a current sharing circuit scheme comprising a first and second power module. Each module includes an input side and an output side with the power modules coupled to each other via respective input sides. Each of the output sides include a positive terminal and a negative terminal. The circuit scheme also comprises first and second circuit output voltage terminals and first and second set point controls coupled to the negative terminal of each of the output sides. A first and second initial set point control is included providing current signal paths between the corresponding first and second set point controls and the first output voltage terminal. The first and second set point and the first and second initial set point controls are configured to allow current sharing through said first and second output voltage terminals when a current signal is applied to said input side of said first and second power modules.
The embodiment of the present invention as set forth above, may be adapted to more precisely handle the variations in the output voltage. Regulation terminals are coupled between the first and second power modules and the negative terminal of said circuit output voltage terminal to maintain the initial set point of the first and second power modules. Regulation terminals are also added between the first and second power module output sides and the other module's trim terminal such that the voltage across the first output terminal is controlled relative to the voltage across the circuit output voltage terminal to facilitate current sharing.
The present invention may be adapted to facilitate current sharing between three power modules. Various embodiments are also included to facilitate current sharing under conditions including mismatched system impedances.
REFERENCES:
patent: 5428523 (1995-06-01), McDonnal
patent: 5724237 (1998-03-01), Hunter
Ericsson Inc.
Navarro Arthur I.
Patel Rajnikant D.
Wong Peter S.
LandOfFree
Simplified current share circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Simplified current share circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Simplified current share circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441725