Switching Regulator Oscillator Spread-Spectrum Clock EMI Reduction
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Solution Overview
Problem
Fixed-frequency clock signals generate high peak frequency spectral density, leading to electromagnetic interference (EMI), which can be mitigated by spread-spectrum clock generation but requires a wider frequency distribution of energy, posing challenges in reducing noise and improving privacy in communications.
Innovation Solution
A switching regulator circuit with an oscillator that includes a variable resistor modulated by a modulating signal to generate a spread-spectrum clock signal, reducing EMI by distributing energy across a wider frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fixed-frequency clock signal is used, then the clock signal has a narrow frequency spectrum with high peak frequency spectral density, but this generates high electromagnetic interference (EMI)
Solution Approach 1:
The patent applies dynamics by modulating the oscillator frequency over time using a spread-spectrum modulation technique. The oscillator frequency is dynamically varied around a center frequency according to a modulation signal, transforming the static fixed-frequency clock into a dynamic spread-spectrum clock that distributes energy across a wider frequency range, thereby reducing peak spectral density and EMI
Solution Approach 2:
The patent changes the frequency parameter of the clock signal from a fixed value to a time-varying value. By applying frequency modulation with a spread-spectrum technique, the instantaneous frequency of the clock signal is varied within a defined bandwidth, spreading the spectral energy and reducing the harmful concentration at any single frequency
2Object-affected harmful factors
If spread-spectrum clock generation is employed to reduce EMI, then the clock signal frequency spectrum is spread over a wider frequency range, but this requires distributing total energy across a broader spectrum which complicates the system
Solution Approach 1:
The patent merges the spread-spectrum modulation function directly into the oscillator circuit itself. The modulation signal is applied to the oscillator's frequency-determining elements (such as varactor diodes or programmable frequency synthesizers), combining the clock generation and spread-spectrum modulation functions in a single integrated circuit block, thereby avoiding the need for separate modulation stages and reducing overall system complexity
Solution Approach 2:
The oscillator circuit is designed to serve multiple functions: it generates the clock signal, implements spread-spectrum modulation, and controls the frequency distribution. This multi-functional oscillator reduces the need for additional dedicated components for each function, simplifying the overall system architecture while achieving EMI reduction
Data Source
AI summary
A switching regulator circuit is provided. The switching regulator circuit includes an oscillator circuit which includes a capacitor, a switch, a comparator, a variable resistor, and a modulating signal generation circuit. The capacitor is arranged to receive a first current to provide a ramp voltage. Also, the variable resistor is arranged to receive a second current to provide a reference voltage. The resistance of the variable resistor is modulated based on a modulating signal. The comparator is arranged to compare the ramp voltage with a reference voltage to provide a clock signal. Further, the switch is arranged to discharge the capacitor when the clock signal is asserted. The modulating signal generation circuit is arranged to provide the modulating waveform as a sawtooth signal, or other type of modulating waveform suitable for spread-spectrum modulation. Accordingly, the clock signal is a spread-spectrum clock signal.