Power controller circuit with automatic correction for phase lag between voltage and current
First Claim
1. A circuit for controlling the amount of AC power delivered to a load by varying the conduction angle of at least one semiconductor switching means, comprisingmeans for detecting the AC voltage zero crossings,means for detecting the load current zero crossings,means for detecting the phase lag between the voltage and the current in said load,means for producing a firing ramp voltage,means for producing a retarding ramp voltage,means combining said firing ramp voltage and said retarding ramp voltage to produce a first set of trigger pulses for establishing a firing conduction angle of said at least one semiconductor switching means,means responsive to said combining means and said phase lag detecting means for generating a second set of trigger pulses for beginning at said firing conduction angle of said at least one semiconductor switching means and continuing past the voltage zero crossing to the load current zero crossing, andmeans for discriminating between binary values of said second set of trigger pulses for supplying discriminate trigger pulses to said at least one semiconductor means.
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Accused Products
Abstract
What is proposed is an electronic circuit for controlling the amount of AC power delivered to an inductive or resistive load which continuously measures the actual phase lag between the load current and applied voltage and automatically adjusts the firing angle to provide the desired amount of AC power. The circuit includes an auxiliary on/off input with soft start and independently adjustable time delays for the on and off functions and also incorporates an input for remote power level control and features a half-wave rectified mode which delivers pulsating DC power to the load.
20 Citations
10 Claims
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1. A circuit for controlling the amount of AC power delivered to a load by varying the conduction angle of at least one semiconductor switching means, comprising
means for detecting the AC voltage zero crossings, means for detecting the load current zero crossings, means for detecting the phase lag between the voltage and the current in said load, means for producing a firing ramp voltage, means for producing a retarding ramp voltage, means combining said firing ramp voltage and said retarding ramp voltage to produce a first set of trigger pulses for establishing a firing conduction angle of said at least one semiconductor switching means, means responsive to said combining means and said phase lag detecting means for generating a second set of trigger pulses for beginning at said firing conduction angle of said at least one semiconductor switching means and continuing past the voltage zero crossing to the load current zero crossing, and means for discriminating between binary values of said second set of trigger pulses for supplying discriminate trigger pulses to said at least one semiconductor means.
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9. A method for controlling the amount of AC power delivered to a load by varying the conduction angle of a semiconductor switching means, comprising the steps of
measuring a phase angle lag between voltage zero crossover and current zero crossover, producing a firing ramp voltage, producing a retarding ramp voltage, combining said firing ramp voltage and said retarding ramp voltage to produce a first set of trigger pulses for establishing a firing conduction angle of said at least one semiconductor switching means, generating a second set of of trigger pulses in response to said first set of trigger pulses for beginning at said firing conduction angle of said at least one semiconductor switching means and continuing past the voltage zero crossover to the load current zero crossover, and discriminating between binary values of said second set of trigger pulses for supplying discriminate trigger pulses to said semiconductor means.
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10. A method for controlling the amount of AC power delivered to a load by varying the conduction angle of a semiconductor switching means, comprising the steps of
detecting the AC voltage zero crossings, detecting the load current zero crossings, measuring the phase lag between the voltage and the current in said load, producing a firing ramp voltage, producing a retarding ramp voltage, combining said firing ramp voltage and said retarding ramp voltage to produce a first set of trigger pulses for establishing a firing conduction angle of said at least one semiconductor switching means, generating a second set of trigger pulses in response to said first set of trigger pulses and said phase lag for beginning at said firing conduction angle of said at least one semiconductor switching means and continuing past the voltage zero crossing to the load current zero crossing, and discriminating between binary values of said sets of trigger pulses for supplying discriminate trigger pulses to said semiconductor means.
Specification