Switching ac voltage regulator
First Claim
1. An ac voltage regulator for receiving an ac input signal having a voltage to be regulated and providing an ac output signal having a regulated voltage, the regulator comprising:
- a transformer having a plurality of windings;
ac switching means, including four switching circuits, each containing a series-connected transistor and diode, for alternately connecting the transformer windings in a first switch configuration, in which the windings are connected such that the ac output signal is substantially the same as the ac input signal, and a second switch configuration, in which the windings are connected so as to transform the ac input signal and cause the ac output signal to have an instantaneous voltage that is a predetermined percentage of the instantaneous voltage of the ac input signal, the duty cycle of the alternate configuration providing a selected average voltage for the ac output signal;
quadrant detection means for determining the instantaneous voltage polarity and current direction of the ac output signal and for producing a corresponding quadrant signal having four possible states; and
control means, responsive to the quadrant signal, for controllably biasing selected transistors of the switching means so as to alternate between the first and second switch configurations at a predetermined modulation frequency substantially greater than the frequency of the ac input signal and at a prescribed duty cycle selected to provide a desired average voltage for the ac output signal;
wherein, for each of the four possible states of the quadrant signal, the control means biases a predetermined first transistor on continuously and biases a predetermined second transistor alternately on and off at the predetermined modulation frequency, wherein each time the second transistor is biased on, the diode connected in series with the associated first transistor becomes reverse biased and electrical current is immediately diverted from the first transistor to the second transistor, without the need for any snubber circuit, and wherein each time the second transistor is biased off, electrical current is immediately diverted from the second transistor to the associated first transistor, without the need for any snubber circuit.
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Accused Products
Abstract
A pulse-width ac voltage regulator that provides a precisely ac output voltage without the need for any inefficient protective circuitry for ensuring proper operation when it repeatedly switches between its two alternative operating modes. A transformer is arranged with a first winding connected between an input terminal and an output terminal and a second winding connected between one end of the first winding and a control terminal. A special switch assembly including four separate circuits, each having a series connected transistor and diode, is controllably switched such that the second winding is alternatively shorted or excited, to provide a stepped-up (or stepped-down) voltage out of the first winding. The transistors are controllably switched at a frequency substantially greater than that of the ac input signal and at a duty cycle selected to provide the desired ac output voltage. Each time a transistor in the assembly is biased ON or OFF, electrical current is immediately diverted from one transistor to another, without the need for any inefficient snubber circuit or the like.
27 Citations
11 Claims
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1. An ac voltage regulator for receiving an ac input signal having a voltage to be regulated and providing an ac output signal having a regulated voltage, the regulator comprising:
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a transformer having a plurality of windings; ac switching means, including four switching circuits, each containing a series-connected transistor and diode, for alternately connecting the transformer windings in a first switch configuration, in which the windings are connected such that the ac output signal is substantially the same as the ac input signal, and a second switch configuration, in which the windings are connected so as to transform the ac input signal and cause the ac output signal to have an instantaneous voltage that is a predetermined percentage of the instantaneous voltage of the ac input signal, the duty cycle of the alternate configuration providing a selected average voltage for the ac output signal; quadrant detection means for determining the instantaneous voltage polarity and current direction of the ac output signal and for producing a corresponding quadrant signal having four possible states; and control means, responsive to the quadrant signal, for controllably biasing selected transistors of the switching means so as to alternate between the first and second switch configurations at a predetermined modulation frequency substantially greater than the frequency of the ac input signal and at a prescribed duty cycle selected to provide a desired average voltage for the ac output signal; wherein, for each of the four possible states of the quadrant signal, the control means biases a predetermined first transistor on continuously and biases a predetermined second transistor alternately on and off at the predetermined modulation frequency, wherein each time the second transistor is biased on, the diode connected in series with the associated first transistor becomes reverse biased and electrical current is immediately diverted from the first transistor to the second transistor, without the need for any snubber circuit, and wherein each time the second transistor is biased off, electrical current is immediately diverted from the second transistor to the associated first transistor, without the need for any snubber circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An ac voltage regulator for receiving an ac input signal having a voltage to be regulated and for supplying an ac output signal having a regulated voltage, the regulator comprising:
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a transformer having a plurality of windings; ac switching means for alternately connecting the transformer windings between a first switch configuration, in which the windings are connected such that the ac output signal is substantially the same as the ac input signal, and a second switch configuration, in which the windings are connected so as to transform the ac input signal and cause the ac output signal to have an instantaneous voltage that is a predetermined percentage of the voltage of the ac input signal, wherein the switching between the alternate switch configurations occurs at a predetermined modulation frequency substantially greater than the frequency of the ac input signal and at a duty cycle selected to provide a predetermined average voltage for the ac output signal; reference means for generating an ac reference signal having a frequency and phase substantially the same as the ac input signal; comparator means for computing the instantaneous ratio of the ac output signal and the ac reference signal and for producing a corresponding error signal; and means for producing a pulse-width modulation signal having a frequency corresponding to the predetermined modulation frequency and having a duty cycle that varies in accordance with the error signal, the pulse-width modulation signal being used by the ac switching means to control its switching between the alternate first and second switch configurations. - View Dependent Claims (11)
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Specification