Electricity: power supply or regulation systems – In shunt with source or load – Using choke and switch across source
Reexamination Certificate
2000-03-13
2001-10-02
Riley, Shawn (Department: 2838)
Electricity: power supply or regulation systems
In shunt with source or load
Using choke and switch across source
C323S283000, C323S290000
Reexamination Certificate
active
06297621
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and apparatus for the control of power converters, and in particular to methods and apparatus for such control that do not require sensing of input and output voltages.
BACKGROUND OF THE INVENTION
Switching power converters are widely used in a large number of domestic and industrial applications. Examples include computer systems, motor drives, and uninterruptible power supplies. With recent advances in semiconductor technologies and electronic packaging techniques, much research work has been done on new power circuit topologies, switching schemes, and control techniques for improving the converter efficiency, electrical specifications, and power density—all the time meeting various industrial standards. Examples of well known power converter topologies include buck converters, boost converters, buck boost converters, flyback converters and forward converters.
An underlying concept of power electronics is to be able to use low-level signals to control high power converter outputs. Conventionally this requires a comparison of the actual output voltage with a desired reference voltage and then giving commands to the power converters. However, it is a common practice that the power conversion stage and the control circuit be isolated in order to avoid noise coupling and grounding problems. In some situations input and output isolation in the power conversion stage is also desirable or necessary. These isolation requirements mean that signal-power interface techniques such as transformer coupling and optical isolation are necessary to achieve output regulation. These requirements substantially increase the cost and complexity of power converters.
PRIOR ART
One solution to this difficulty is to control switching power converters by using current sensors only and without requiring the use of voltage sensors. Such a system was described in
T. Ohnuki, O. Mivashita, P. Lataire
&
G. Maston IEEE Transactions on Power Electronics, Vol.
14
No.
2. Mar. 1999. In the system proposed in this paper only current sensors are used that generate signals in response to the currents flowing in inductors. The sensed current can in theory be used to obtain the input and output voltages and so provide control information. The use of current sensors alone has a number of advantages including a reduction in the number of sensors needed, and it obviates the need to use a dissipative voltage divider, such as a resistive network, to obtain the input voltage in feedforward arrangements and in output voltage regulation. Additionally, no voltage isolator (such as an optical coupler) is needed to isolate the high-voltage output and the low-voltage control signals. This has an additional advantage in that some optical isolators have a finite linear range, eliminating the need for such isolators therefore increases the practical voltage measurement range.
Since the current can be sensed using a contactless flux linkage sensor such as a Hall effect sensor, electrical isolation between the power conversion stage and the control stage may be achieved easily. This has the effect that the power and ground signals can be separated inherently so as to reduce noise coupling.
The proposal of this prior art has, however, a number of practical drawbacks. Most importantly it assumes that the circuit is an “ideal” circuit which in reality no such circuit ever would be. In addition, the current rather than being continuously sensed is simply sampled once in every switching cycle with the inevitable approximations and inaccuracies that this implies.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, it provides an apparatus for the voltage control of a power converter, comprising means for sensing an inductor current and means for deriving input and/or output voltages from the current. The apparatus further includes means for converting the inductor current to an inductor voltage, comprising means for determining an instantaneous inductance, means for determining a rate of change of the inductor current, means for multiplying the inductor current by an inductor resistance, means for generating a product of outputs of the instantaneous inductance determining means and the inductor current change rate determining means, and means for summing outputs of the multiplying means and the product.
In preferred embodiments, the output of the inductor current to inductor voltage converting means comprises positive and negative envelopes and the input and output voltage deriving means comprises means for demodulating the envelopes.
Depending on the nature of the power converter, the demodulated positive and negative envelopes may be combined in various ways to derive the input and output voltages.
According to another embodiment of the present invention, it provides a method for the voltage control of a power converter, comprising sensing an inductor current and deriving input and/or output voltages from the current. The method further includes converting the inductor current to an inductor voltage, comprising: determining an instantaneous inductance, determining a rate of change of the inductor current, multiplying the inductor current by an inductor resistance, generating a product of outputs of the instantaneous inductance and the inductor current change rate, and summing the outputs of multiplying the inductor current by the inductor resistance and the product.
According to another embodiment, the present invention provides a power converter, comprising a feedback or feedforward control means, means for sensing an inductor current, means for deriving an input and/or output voltage therefrom, and means for inputting the derived input and/or output voltage to the feedback or feedforward control means.
REFERENCES:
patent: 5475296 (1995-12-01), Vinsant et al.
patent: 5602463 (1997-02-01), Bendall et al.
Ohnuki et al., “Control of a Three-Phase PWM Rectifier Using Estimated AC-Side and DC-Side Voltages,”IBEE Transactions on Power Electronics, vol. 14, No. 2, (Mar. 1999). pp. 222-226.
Chung Henry Shu-Hung
Hui Ron Shu-Yuen
City University of Hong Kong
Merchant & Gould P.C.
Riley Shawn
LandOfFree
Voltage sensorless control of power converters does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Voltage sensorless control of power converters, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Voltage sensorless control of power converters will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2614430