DC bias prevention in transformerless inverters
First Claim
1. A method of operating a transformerless DC to AC converter comprising circuitry including a plurality of transistor switches and a controller operative to control the switches to commutate DC inputs onto AC outputs so as to generate an approximation of an AC waveform at a desired power line frequency, comprising:
- monitoring a DC bias component on the AC output of the converter;
comparing the DC bias component to a predetermined threshold; and
only when the DC bias component is below the predetermined threshold, modifying, by the controller, the AC waveform generated, so as to reduce the DC bias component.
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Accused Products
Abstract
A transformerless DC to AC inverter providing an AC output at a power line voltage and at a power line frequency suitable for driving AC loads or appliances and having DC bias measurement circuitry for continuously assessing the magnitude of any DC bias component on the AC output, such as due to fault conditions or non-linear loads, and operative to eliminate or reduce any unwanted DC bias component from the AC output.
85 Citations
13 Claims
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1. A method of operating a transformerless DC to AC converter comprising circuitry including a plurality of transistor switches and a controller operative to control the switches to commutate DC inputs onto AC outputs so as to generate an approximation of an AC waveform at a desired power line frequency, comprising:
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monitoring a DC bias component on the AC output of the converter; comparing the DC bias component to a predetermined threshold; and only when the DC bias component is below the predetermined threshold, modifying, by the controller, the AC waveform generated, so as to reduce the DC bias component. - View Dependent Claims (2, 3, 4, 5)
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6. A transformerless DC to AC converter, comprising:
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circuitry connected between DC inputs and AC output, the circuitry including a plurality of transistor switches; a controller operative to control the switches to commutate the DC inputs onto the AC outputs so as to generate, at the AC outputs, an approximation of an AC waveform at a desired power line frequency; a measuring circuit connected to the controller and operative to continuously measure a value of a DC bias component on the AC output of the converter; and wherein the controller is further operative to compare a magnitude of the DC bias component to a predetermined threshold and only when the DC bias component is below the predetermined threshold, to modify the AC waveform generated, so as to reduce the DC bias component. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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Specification