As the need for more complex control and friendly user interface is increasing, digital control implementation is crucial in modern energy conversion systems and power electronic converters. The Load resonant inverter (LRI) can be controlled to generate a quasi square wave of variable pulse width generated by digital signal processor (DSP). It is used to store the required commands for generating the necessary waveforms to control the frequency of the inverter through proper design of switching pulses. In this paper, a digital controller has been implemented which possess advantages of phase shift control while providing rapid frequency tracking for load resonant applications. The digital control algorithm has been optimized in Embedded C Language and implemented on a floating point Digital Signal Processor TMS320F28335. The DSP alogorithm is experimentally evaluated on load resonant inverter used for an induction heating system prorotype.

Statistical experimental design was used to optimize the chromatographic separations of two potential impurities in fixed dose combination tablets. Risk assessment has been made based on knowledge gathered during development activity. The Critical Quality Attributes (CQA's) selected were Trifluoroacetic acid (TFA) concentration, organic solvent and column temperature. A Box-Behnken Design was utilized using Minitab software to study the effects of these CQA's on closely eluting peaks of S-Oxide and Tenofovir. The effect of these three CQA's on resolution is depicted in the form of the p and f values between the various combination and permutations of these three CQAs. The chromatographic method employed a HPLC, Zorbax SB-Phenyl C18 column (150 x 4.6 mm i.e., 3.5µm particle size) with the mobile phase consisting of a TFA buffer and Methanol: TFA ((85:15 v/v) in a gradient program. The flow rate, injection volume and detection were 1.0 mL/min, 15 μL and 262 nm respectively. As per design space, 15 validation runs were performed and out of which Run 11 gave more resolution, i.e., of 4.4 at 45 °C column temperature with 0.11 % TFA concentration in mobile phase A and Methanol: 0.1% TFA in water (85:15 % v/v) in mobile phase B which was studied with different plots like interaction plot and overlaid contour plots. The results clearly showed that the quality by design concept could be effectively applied to optimize HPLC chromatographic method parameters with fewer trials and error-free experimentation.