Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Patent
1992-04-03
1993-08-03
Stephan, Steven L.
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
363 80, 323222, H02M 712, G05F 156
Patent
active
052335097
ABSTRACT:
An adjustable near unity power factor is achieved while reducing harmonics in a switch-mode power supply by replacing the conventional diode bridge in the front end with an H-bridge driver. Two feedback loops are required, one feedback loop is used to regulate a DC bulk voltage by comparing the DC bulk voltage to a reference voltage and generating an error signal therefrom. A programmable offset is applied to the error signal for adjusting the power factor. A second feedback loop samples and scales the AC input voltage for use as a scaled replica of the input current. The actual input current is then compared to the scaled replica current to produce a second error signal. The two error signals are multiplied to determine the desired input current wherein the desired input current follows the AC input voltage. The desired input current is pulse width modulated by a fixed frequency sawtooth waveform for providing switching signals for controlling the H-bridge driver. The H-bridge driver thus operates such that the input current closely follows the AC input voltage and near unity power factor is maintained. A DC-to-DC converter follows the H-Bridge driver using a single feedback loop for regulating a desired DC output voltage.
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Anderson F. E.
Berhane Adolf
International Business Machines - Corporation
Lobsenz C. B.
Stephan Steven L.
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