Regulation of current or voltage with PWM controller
AssigneeRochester Instrument Systems, Inc.
InventorJoseph A. Martin
Life of this patent
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Abstract
A circuit for providing a periodic output having a regulated magnitude is derived from a periodic input source. A switch is serially connected to the input for periodically sampling the input at a sampling frequency which is much higher than the frequency of the periodic input, while the duty ratio of the sampling is modulated as an inverse function of the output magnitude. The pulse train of samples is filtered to remove the sampling frequency and its harmonics and the result is a regulated output which replicates the input waveform.
Claims28
A controller circuit for providing, at a controller output, a periodic output waveform having a regulated magnitude derived from a periodic source connected to a controller input, the controller circuit providing line and load regulation compensating for line and load variations, the circuit comprising:
- (a) a switch having an input connected to the controller input, an output and a switching control input;
- (b) a magnitude detector having an input connected to the controller output, a detector output, and means for developing a detector output signal which is a function of the magnitude of the AC output waveform, the detector output signal provided at the detector output;
- (c) a pulse width modulated oscillator having an input coupled to the detector output, means for developing an oscillator frequency greater than the frequency of the periodic source, an output, and means for developing an output pulse signal having a frequency greater than the frequency of the periodic source and having a width which is modulated proportional to the signal at the oscillator input, the output pulse signal produced at the output of the oscillator, the oscillator output connected to the switching control input of the switch for periodically switching the switch between its on and off states at a duty ratio which is an inverse function of the magnitude of the controller output;
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- (d) a low pass filter having an input coupled to the output of the switch and an output coupled to the controller output and adapted to reject frequencies at and above the oscillator frequency and produce at the filter output a resulting filtered signal at the frequency of the periodic input.
A method for providing a regulated periodic output from a periodic input, the method providing line and lead regulation compensating for line and load variations, the method comprising:
- (a) sampling the input at a sampling frequency at least 10 times the frequency of the period input while modulating the duty ratio of the samples as an inverse function of the magnitude of the output;
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- (b) filtering out the sampling frequency and harmonics of the sampling frequency from the sampled input, and providing the resulting filtered signal at the frequency of the periodic input.
A controller for providing a regulated periodic output waveform at a controller output derived from a periodic source connected to a controller input, the controller providing line and load regulation compensating for line and load variations, the controller comprising:
- (a) detector means having an output and having an input connected to the controller output for detecting the magnitude of the output waveform;
- (b) pulse width modulated sampling means having an input connected to the controller input, having a sample control input connected to the output of the detecting means, and means for sampling the periodic source at a sampling frequency which exceeds the frequency of the periodic source while modulating the duty ratio of the samples as an inverse function of the output waveform magnitude;
- and
- (c) low-pass filter means having an input coupled to the sampling means and an output coupled to the controller output for filtering out the sampling frequency and harmonics of the sampling frequency and providing the resulting filtered signal at the frequency of the periodic input.
Dependencies are inferred from the claim text.