Analog Simulation Tools Aid Digital-Control-Circuit Designers


Posted on Feb 6, 2014

Although analog and digital controllers may appear vastly different, their principles of operation are usually quite similar. Therefore, popular analog tools like Spice can still be used to benefit common digital proportional-integral controllers through analysis without spending hours on complex math or a fortune on specialized software. To give


Analog Simulation Tools Aid Digital-Control-Circuit Designers
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readers a hands-on view of these benefits, a digital infrared controller was developed. The PIC MCU drives current through an infrared emitter with its pulse-width modulator and measures the sensor voltage with its analog-to-digital converter. The article details the simulation of the IR controller through the use of Spice. Among the topics covered are the voltage-controlled voltage source, which is essentially an ideal op amp that can simulate the controller simply by adding resistors and capacitors. Also discussed is execution of the proportional-integral algorithm in Visual Basic. Detailed Spice results are provided. A closed-loop controller`s function is to maintain a desired response despite system changes and disturbances. An infrared controller was developed for this article to guide the reader through the analog simulation of a digital circuit. One of the most popular programs for simulating analog circuits is Spice, thanks to decades of validated operation and ease of access. An analog equivalent of the digital infrared controller executing the proportional-integral algorithm is provided to illustrate the simulation. The algorithm is executed through a PC in Visual Basic for development ease because it`s faster and easier than generating firmware. Spice results for various parameters were determined for the example digital controller. For instance, the loop gain showed a 3. 25-Hz bandwidth and 72. 3 ° phase margin....




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