IT电源管理芯datasheet-slua622.pdfVIP

Application Report SLUA622 – December 2011 Digital Loop Exemplified Srivatsa Raghunath 1 Introduction Industry standard for the control of switch mode power supply (SMPS) systems has been analog control. Now with the advent of high speed, lower cost digital ICs there has been an increased interest in digital control of SMPS. Digital control offers opportunities to optimize operation w.r.t control, efficiency, line and load regulation. The ease of loop control is what makes digital control most attractive especially in non-isolated buck application. A converter with a digital loop can act as its own network analyzer. Based on measurement of the system, a device can optimize its loop response. This is of special advantage in point of load bucks to compensate for actual capacitive loading and adjust as components age. The aim and challenge of this paper is to compare the feedback loop of analog buck solution and feedback loop of a digital buck solution. The entire frequency domain to time domain calculations will be clearly stated and this will give a theoretical confidence in moving from analog to digital solution. A TPS40k analog buck solution will be compared to an UCD921x digital solution and its feedback loops will be designed 2 Feedback Theory A system always exists in time domain. It can be represented in different domains to get more information on the nature and characteristic of the system. The various domains for signals and systems are as shown in table 1. Table 1. Domain