LFSR Timebase Control for DC-DC Converter Noise Spreading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switch mode DC-to-DC converters experience undesirable noise spurs at the switching frequency, which interfere with electronic device performance and are not effectively mitigated by existing technologies.
Innovation Solution
The use of a timebase generator comprising a linear feedback shift register (LFSR) and a programmable digital divider to generate a pseudo-random sequence of timebase control words, varying the switching frequency in a narrow range, thereby spreading switching noise across multiple frequencies and reducing its amplitude at any specific frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a fixed switching frequency is used in DC-to-DC converters, then the converter operates efficiently at a specific frequency, but noise spurs are concentrated at that frequency causing electromagnetic interference
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The timebase generator uses an LFSR to continuously vary the switching frequency within a narrow range, transforming the static frequency into a dynamic, time-varying parameter. This frequency modulation spreads the noise energy across multiple frequencies, resolving the contradiction between noise concentration and operational efficiency.
Solution Approach 2:
The patent changes the frequency parameter of the switching signal from a constant value to a time-varying value generated by the LFSR-based timebase generator. By modifying this key parameter, the noise spectrum is spread across multiple frequencies rather than concentrated at a single frequency, reducing electromagnetic interference while maintaining converter efficiency.
2Object-generated harmful factors
If the switching frequency is varied to spread noise, then electromagnetic interference is reduced, but the timebase generation becomes more complex
Solution Approach 1:
The LFSR-based timebase generator is self-service in that it automatically generates the varying frequency sequence without requiring external control or complex programming. The feedback mechanism within the LFSR self-regulates the frequency variation, simplifying the overall control architecture while achieving noise spreading. This resolves the contradiction by providing complex functionality through a self-managing structure rather than requiring complex external control.
Solution Approach 2:
The LFSR uses feedback from its own output to determine its next state, creating a deterministic pseudo-random sequence. This feedback mechanism enables the timebase generator to autonomously produce frequency variations, reducing the need for complex external control logic while achieving the desired noise spreading effect across multiple frequencies.
3Object-generated harmful factors
If noise energy is distributed across multiple frequencies, then the amplitude at any specific frequency is reduced, but the overall noise power remains the same
Solution Approach 1:
The patent applies local quality by concentrating the noise spreading effect specifically in the frequency domain rather than attempting to reduce total noise energy. The LFSR-based timebase generator selectively modulates the switching frequency to spread noise across adjacent frequencies, achieving local improvement in noise amplitude at any given frequency without requiring global energy reduction. This resolves the contradiction by accepting constant total energy while improving local noise characteristics.
Data Source
AI summary
An integrated circuit. The integrated circuit comprises a timebase generator and a switch mode direct current-to-direct current (DC-to-DC) voltage converter coupled to the timebase generator. The timebase generator comprises a first linear feedback shift register (LFSR), a signal generator having an input coupled to an output of the first LFSR; and a digital divider comprising a second LFSR and a programmable digital divider, wherein a clock input of the programmable digital divider is coupled to an output of the signal generator, wherein an output of the programmable digital divider is coupled to a clock input of the first LFSR and is coupled to a clock input of the second LFSR, and wherein an output of the second LFSR is coupled to a program input of the programmable digital divider.