High voltage, high efficiency sine wave generator with pre-set frequency and adjustable amplitude

An apparatus for generating a sinusoid at a pre-set frequency f, the apparatus comprising:

• n DC power sources, each of the n DC power sources having a voltage-control input that sets an output voltage of the respective power source, wherein n is a positive integer;
• a transformer having a primary and a secondary;
• a power switch having a control input, wherein the power switch is configured to either (a) apply the output of a selected one of the n DC power sources to the primary of the transformer in a selected direction in response to 2n states of a control signal that is applied to the control input or (b) remain off in response to an additional state of the control signal;
• a sequencer configured to control the generation of an oversampled version of a sine wave that is sampled N times per cycle using evenly spaced samples that include a sampling point at 0°, where N=2+4n, by setting the output voltages of the n DC power sources to levels that are present on the oversampled version of the sine wave, and then sequencing the control signal through the 2n states and the additional state, so that each of the n DC power sources is applied to the primary of the transformer in each direction at appropriate times in a sequence so as to generate the oversampled version of the sine wave;
• and
• an output filter connected to the secondary of the transformer, wherein the output filter passes the pre-set frequency f and attenuates frequencies above a cut-off frequency, and wherein the output filter has a transfer function with a zero at a frequency where a harmonic of the pre-set frequency f is expected to contain power, and
• wherein a controller is configured to control an amplitude of the sinusoid by adjusting the output voltages of the n DC power sources via the voltage-control inputs, while maintaining a fixed ratio between the output voltages of each of the n DC power sources.

An apparatus for generating a sinusoid at a pre-set frequency f, the apparatus comprising:

• n DC power sources, each of the n DC power sources having a voltage-control input that sets an output voltage of the respective power source, wherein n is a positive integer;
• a power switch having output terminals and a control input, wherein the power switch is configured to either (a) switch the output of a selected one of the n DC power sources across the output terminals in a selected direction in response to 2n states of a control signal that is applied to the control input or (b) remain off in response to an additional state of the control signal;
• a sequencer configured to control the generation of an oversampled version of a sine wave that is sampled N times per cycle using evenly spaced samples that include a sampling point at 0°, where N=2+4n, by setting the output voltages of the n DC power sources to levels that are present on the oversampled version of the sine wave, and then sequencing the control signal through the 2n states and the additional state, so that each of the n DC power sources is switched across the output terminals in each direction at appropriate times in a sequence so as to generate the oversampled version of the sine wave;
• and
• an output filter that filters a signal received from the output terminals of the power switch, wherein the output filter passes the pre-set frequency f and attenuates frequencies above a cut-off frequency, and wherein the output filter has a transfer function with a zero at a frequency where a harmonic of the pre-set frequency f is expected to contain power,
• wherein a controller controls an amplitude of the sinusoid by adjusting the output voltages of the n DC power sources via the voltage-control inputs, while maintaining a fixed ratio between the output voltages of each of the n DC power sources.

A method for generating a sinusoid at a pre-set frequency f, the method comprising:

• setting n DC power sources to respective output voltages, wherein n is a positive integer;
• generating an oversampled version of a sine wave that is sampled N times per cycle using evenly spaced samples that include a sampling point at 0°, where N=2+4n, by setting the output voltages of the n DC power sources to levels that are present on the oversampled version of the sine wave, and then switching the outputs of the n DC power sources to an output in a controlled sequence such that each of the n DC power sources is switched to the output in each direction at appropriate times in the sequence so as to generate the oversampled version of the sine wave;
• and
• filtering the oversampled version of the sine wave to pass the pre-set frequency f and attenuate frequencies above a cut-off frequency, wherein the filtering implements a transfer function with a zero at a frequency where a harmonic of the pre-set frequency f is expected to contain power,
• wherein the amplitude of the sinusoid is controlled by adjusting the output voltages of the n DC power sources.