QUANTIZED DUTY RATIO CONTROL IN SWITCH-MODE POWER CONVERTERS (CONDITIONER, SUPPLY)

Digital control techniques which provide output voltage regulation in switch-mode power converters through the dynamic generation of time-quantized switch control waveforms are investigated.; A duty ratio quantization technique is developed and applied to a feedforward regulator. The regulation characteristics and quantization effects are analyzed and measured.; Digital proportional-integral-differential (PID) feedback and duty ratio quantization are combined to form a closed-loop digital power converter controller. Specific hardware implementations are described. A time domain computer model is developed to investigate the transient behavior of the closed-loop system. A frequency domain model is developed to predict closed-loop stability for various operating conditions. The unique ability of the digital PID controller to operate at various switching frequencies is described and experimentally verified. Normalized frequency characteristics of the digitally controlled power converter are developed. Digital implementations of special power converter control functions, open-loop operation, and the origin of quantization noise are discussed.; Detailed descriptions of the experimental digital control circuitry and the power switching circuitry are provided. Techniques are described and employed for experimental measurements of the model elements. The accuracy of the time domain model is demonstrated by a comparison of the predicted transient behavior to the measured transient behavior. The frequency domain model is shown to correctly predict instability in an experimental digitally controlled power converter. The operation of the digitally implemented special functions of output current limiting and power-up soft-start is verified. Measurements of quantization noise showing the relationship to changes in operating conditions are presented and discussed.; A digitally controlled ac to dc power conditioner which draws high quality sinusoidal input current is presented. A digital proportional-integral (PI) controller and a quantized current gain technique are utilized. The topics of investigation include: general aspects of unity power factor power conditioning; modeling, analysis and simulation of the closed-loop digitally controlled system; stability criteria; and experimental measurement of the harmonic current content and transient response.