Method for generating pulse width modulated control signals

Claim 1

A method of generating a pulse width modulated (PWM) control signal for an electronic power converter having semiconductor switching elements in series between positive and negative DC buses and which has an output of variable amplitude and variable frequency, comprising the setps of: modulating an approximated reference waveform having positive and negative polarities with a timing waveform having a frequency substantially greater than said reference waveform and the same polarity, in each half period, as said reference waveform; calculating points of intersection of said waveforms to determine switching points of said control signal; generating a train of PWM pulses each occurring at the start of an interval in which the magnitude of said timing waveform is less than said reference waveform and terminating at the end of the respective interval; and supplying said PWM pulses to the switching elements of said power converter to control its output, whereby simultaneous conduction of series-connected switching elements to short circuit the DC buses is prevented.

Claim 2

A method of generating a pulse width modulated (PWM) control signal for an electronic power converter having semiconductor switching elements in series between positive and negative DC buses and which has an output of variable amplitude and variable frequency, comprising the setps of: modulating an approximated reference waveform having positive and negative polarities with a timing waveform having a frequency substantially greater than said reference waveform and the same polarity, in each half period, as said reference waveform; calculating points of intersection of said waveforms to determine switching points of said control signal; generating a train of PWM pulses each occurring at the start of an interval in which the magnitude of said timing waveform is less than said reference waveform and terminating at the end of the respective interval; and supplying said PWM pulses to the switching elements of said power converter to control its output, whereby simultaneous conduction of series-connected switching elements to short circuit the DC buses is prevented.

Claim 4

A method of generating a pulse width modulated control signal for an electronic power converter which has an output of variable amplitude and variable frequency comprising the steps of: modulating a reference waveform having positive and negative polarities with a timing waveform having a higher frequency than said reference waveform and the same polarity, in each half period, as said reference waveform; generating a train of width modulcated pulses each occurring at the start of an interval in which the magnitude of said timing waveform is less than the magnitude of said reference waveform, and terminating at the end of the respective interval; and supplying said pulses to the switching elements of said power converter to control its output; wherein said reference waveform is a trapezoidal approximation of a sinusoidal waveform and said timing waveform is triangular, and the step of calculating points of intersection of said trapezoidal and triangular waveforms to determine the time boundaries of said pulses.

Claim 5

A method of generating a pulse width modulated control signal for an electronic power converter which has an output of variable amplitude and variable frequency comprising the steps of: modulating a reference waveform having positive and negative polarities with a timing waveform having a higher frequency than said reference waveform and the same polarity, in each half period, as said reference waveform; generating a train of width modulcated pulses each occurring at the start of an interval in which the magnitude of said timing waveform is less than the magnitude of said reference waveform, and terminating at the end of the respective interval; and supplying said pulses to the switching elements of said power converter to control its output; wherein said reference waveform is a trapezoidal approximation of a sinusoidal waveform and said timing waveform is triangular, and the step of calculating points of intersection of said trapezoidal and triangular waveforms to determine the time boundaries of said pulses.

Claim 6

A method of generating a pulse width modulated (PWM) control signal for an electronic power inverter which has an output of variable amplitude and variable frequency comprising the setps of: modulating a sinusoidal reference waveform having positive and negative polarities with a triangular timing waveform having a higher frequency than said reference waveform and the same polarity, in each half period, as said reference waveform; generating a train of PWM pulses each occurring at the start of an interval in which the magnitude of said triangular waveform is less than the magnitude of said sinusoidal waveform, and terminating at the end of the respective interval; and supplying said PWM pulses to the switching elements of said power inverter to control its output; wherein said sinusoidal reference waveform is approximated by a trapezoidal waveform, and the step of calculating in a microprocessor points of intersection of said trapezoidal and triangular waveforms to determine switching points of said control signal.

Claim 7

A method of generating a pulse width modulated (PWM) control signal for an electronic power inverter which has an output of variable amplitude and variable frequency comprising the setps of: modulating a sinusoidal reference waveform having positive and negative polarities with a triangular timing waveform having a higher frequency than said reference waveform and the same polarity, in each half period, as said reference waveform; generating a train of PWM pulses each occurring at the start of an interval in which the magnitude of said triangular waveform is less than the magnitude of said sinusoidal waveform, and terminating at the end of the respective interval; and supplying said PWM pulses to the switching elements of said power inverter to control its output; wherein said sinusoidal reference waveform is approximated by a trapezoidal waveform, and the step of calculating in a microprocessor points of intersection of said trapezoidal and triangular waveforms to determine switching points of said control signal.