Question

Explain how using dSpace to implement your buck converter will limit the possible switching frequencies you can use

Answer 1

The switched mode dc-dc converters are some of the simplest power electronic circuits which convert one level of electrical voltage into another level by switching action. These converters have received an increasing deal of interest in many areas. This is due to their wide applications like power supplies for personal computers, office equipments, appliance control, telecommunication equipments, DC motor drives, automotive, aircraft, etc. The analysis, control and stabilization of switching converters are the main factors that need to be considered. Many control methods are used for control of switch mode dc-dc converters and the simple and low cost controller structure is always in demand for most industrial and high performance applications. Every control method has some advantages and drawbacks due to which that particular control method consider as a suitable control method under specific conditions, compared to other control methods. The control method that gives the best performances under any conditions is always in demand.

Direct current-to-direct current (DC/DC) converters with faster switching frequencies are becoming popular due to their ability to decrease the size of the output capacitor and inductor to save board space. On the other hand, the demands from the point-of-load (POL) power supply increase as processor core voltage drops below 1V, making lower voltages difficult to achieve at faster frequencies due to the lower duty cycle.

Many power IC suppliers are aggressively marketing faster DC/DC converters that claim to save space. A DC/DC converter switching at 1 or 2 MHz sounds like a great idea, but there is more to understand about the impact to the power supply system than size and efficiency. Several design examples will be shown revealing the benefits and obstacles when switching at faster frequencies

Three different power supplies were designed and built to show the trade offs of high switching frequency. For all three designs, the input voltage is 5V, the output voltage is 1.8V, and the output current is 3A. These requirements are typical for powering a performance processor such as a DSP, ASIC or FPGA. To bound the filter design and performance expectations, the allowable ripple voltage is 20 mV, which is about one percent of the output voltage, and the peak-to-peak inductor current is chosen at 1A.

Independent designs at frequencies of 350, 700, and 1600 kHz will be compared to illustrate the benefits and obstacles. The TPS54317, a 1.6 MHz, low-voltage, 3 A synchronous-buck DC/DC converter with integrated MOSFETs was chosen as the regulator in each example. The TPS54317 from Texas Instruments features a programmable frequency, external compensation and is intended for high-density processor power point-of-load applications.