Inverter for producing a true sine wave
First Claim
1. A power inverter, comprising:
- a transformer including a primary winding having first and second ends and a tap between the first and second ends for receiving a DC voltage input, and a secondary winding for outputting an output waveform;
a comparator comparing the output waveform to a reference signal and outputting a correction signal based on the comparison;
a controller receiving the correction signal and providing a switching signal, a duty cycle of the switching signal being adjusted based on the correction signal; and
a first switch coupled to the first end of the primary winding and a second switch coupled to the second end of the primary winding, the first and second switch switching the transformer in accordance with the switching signal so that the output waveform tracks the reference signal.
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Accused Products
Abstract
A power inverter includes a transformer having a primary winding with a first and second ends and a tap between the first and second ends for receiving a DC voltage input, and a secondary winding for outputting an output waveform. A comparator compares the output waveform to a reference signal and outputs a correction signal based on the comparison. A controller receives the correction signal and provide a switching signal. The duty cycle of the switching signal is adjusted based on the correction signal. First and second switches are coupled to the first and second ends, respectively, of the primary winding. The first and second switches switch the transformer in accordance with the switching signal so that the output waveform tracks the reference signal.
139 Citations
20 Claims
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1. A power inverter, comprising:
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a transformer including a primary winding having first and second ends and a tap between the first and second ends for receiving a DC voltage input, and a secondary winding for outputting an output waveform;
a comparator comparing the output waveform to a reference signal and outputting a correction signal based on the comparison;
a controller receiving the correction signal and providing a switching signal, a duty cycle of the switching signal being adjusted based on the correction signal; and
a first switch coupled to the first end of the primary winding and a second switch coupled to the second end of the primary winding, the first and second switch switching the transformer in accordance with the switching signal so that the output waveform tracks the reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A power inverter, comprising:
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a transformer including a primary winding receiving a DC input at a center tap and a secondary winding outputting an output waveform. means for generating a reference signal having a desired shape for the output waveform;
means for switching the transformer at a high frequency;
means for comparing the output waveform to the reference signal and for outputting a correction signal based on the comparison; and
means for pulse width modulating the means for switching and for adjusting a duty cycle of the means for switching based on the correction signal, so that the output waveform tracks the reference signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A power inverter, comprising:
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a step-up transformer having a primary winding, a secondary winding, and a center tap on the primary winding adapted to be coupled to a DC voltage supply;
an FET switch connected at each end of the primary winding;
a sine wave generator producing a low frequency reference signal;
a controller producing a high frequency signal for switching the FET switches at the rate of the high frequency signal to produce a high voltage, high frequency signal on the secondary winding;
a filter coupled on the secondary winding for producing a DC output signal from the high voltage, high frequency signal; and
a comparator having a first input for receiving the low frequency reference signal from the sine wave generator and a second input for receiving a signal corresponding to the stepped up DC voltage and for producing a correcting signal corresponding to a difference between the first and second inputs, wherein the controller adjusts pulse widths of the high frequency signal based on the correcting signal so that the amplitude of the DC output signal is modulated to vary between a maximum voltage and a minimum voltage at the same frequency as the low frequency reference signal in order to produce a simulated AC signal comprising a true sine wave.
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20. In a power inverter, a method for producing a true sine wave output, comprising:
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providing a DC input to a center tap of a primary winding of a transformer;
generating a high frequency pulse width modulated (PWM) signal;
applying the high frequency PWM signal to switches at each end of the primary winding of the transformer for switching the transformer on and off at a high frequency to produce a high frequency signal output at a secondary winding of the transformer;
comparing the signal output with a reference signal representing a desired output; and
adjusting the pulse width modulation of high frequency PWM signal depending on the comparison, whereby the signal output is caused to track the reference signal.
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Specification