3D Frequency Dithering for DC-to-DC Converter Noise Suppression
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Solution Overview
Problem
Existing DC-to-DC converters in mobile phones generate significant switching noise, leading to spurious RF transmissions and poor communication quality due to output voltage ripple, which is exacerbated by frequency dithering methods that either increase ripple or require costly filtering.
Innovation Solution
A three-dimensional fast dithering method is introduced, where the switching frequency of a DC-to-DC converter is modulated with a pseudo-random value to spread the frequency over a wider bandwidth, reducing output voltage ripple and EMI, while allowing for less stringent filtering requirements and increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If frequency dithering is applied to reduce switching noise, then spurious RF transmissions are reduced, but output voltage ripple increases
Solution Approach 1:
The patent extends traditional frequency dithering (one-dimensional variation of switching frequency) to three-dimensional dithering by adding two more dimensions: duty cycle modulation and phase shifting. This multi-dimensional approach spreads the switching noise spectrum more effectively across frequency, time, and phase domains, reducing peak ripple amplitude while maintaining EMI suppression benefits.
Solution Approach 2:
The invention dynamically adjusts multiple parameters (frequency, duty cycle, phase) in a coordinated manner rather than using fixed dithering patterns. This dynamic multi-parameter modulation allows the system to adaptively suppress ripple at different operating conditions while spreading noise energy across multiple dimensions, preventing concentration of ripple at specific frequencies.
2Object-affected harmful factors
If traditional filtering is used to reduce output voltage ripple, then ripple is suppressed, but device complexity and cost increase
Solution Approach 1:
The patent replaces passive mechanical/electrical filtering components with an active control mechanism that uses multi-dimensional dithering of switching parameters. Instead of using large inductors and capacitors to physically filter ripple, the system uses controlled variations in frequency, duty cycle, and phase to spread and suppress noise spectrally, eliminating the need for bulky filtering hardware.
Solution Approach 2:
The invention changes the operating parameters of the DC-to-DC converter (switching frequency, duty cycle, phase) in a coordinated three-dimensional dithering pattern. By dynamically modulating these parameters, the system transforms the ripple suppression problem from a passive filtering task into an active parameter control task, achieving ripple reduction through intelligent parameter management rather than hardware filtering.
3Loss of energy
If switching frequency is increased to improve converter efficiency, then energy transfer efficiency improves, but switching noise and EMI increase
Solution Approach 1:
The patent applies three-dimensional dithering that operates effectively at high switching frequencies by spreading noise energy across frequency, duty cycle, and phase dimensions. This allows the converter to maintain high switching frequencies for efficiency while the multi-dimensional noise spreading prevents concentration of EMI at any single frequency, enabling high-efficiency operation with controlled emissions.
Data Source
AI summary
A circuit and method is disclosed that dithers a switching frequency of a DC-to-DC converter which gets modulated onto an RF carrier such that switching noise is spread over a given bandwidth that is wider than a communications measurements bandwidth. The circuit includes a switching circuitry adapted to transfer energy from a source to a load using a switching signal having a series of switching cycles and a switching frequency. Also included is a control circuitry adapted to generate a pseudo-random value near a beginning of each of the series of switching cycles to determine a maximum switching frequency value based upon the pseudo-random value. The method includes adjusting the switching frequency of the switching signal incrementally from a fixed minimum switching frequency value to the maximum frequency value and vice versa as a function of time during each of the series of switching cycles of the switching circuit.