Spread-Spectrum DC/DC Converter Control for Radio Interference
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Solution Overview
Problem
Conventional DC/DC converters with fixed frequency switching signals cause interference in portable electronic devices, leading to poor connections and reduced convenience due to their fixed frequency control signals.
Innovation Solution
A DC/DC converter utilizing a spread spectrum switching signal controller with a Phase Lock Loop (PLL), programmable frequency divider, and counter to generate a control signal with a varying frequency centered at the working frequency, reducing interference by dynamically adjusting the duty cycle based on feedback voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed frequency control signal is used to control the switch, then the DC/DC converter can maintain stable output voltage, but it generates interference with radio signals in portable devices
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The controller dynamically adjusts the switching frequency around a center frequency using spread spectrum techniques, which reduces peak spectral density and minimizes radio frequency interference while maintaining the average output voltage stability through feedback control.
Solution Approach 2:
The patent changes the frequency parameter of the control signal from a fixed value to a dynamically varying value. By modulating the switching frequency according to a spread spectrum pattern centered at the working frequency, the system reduces harmonic content at any single frequency while maintaining the overall energy transfer required for stable voltage output.
2Object-affected harmful factors
If the switching frequency is varied to reduce interference, then radio signal interference is reduced, but the control signal complexity increases
Solution Approach 1:
The patent introduces an intermediary frequency modulation stage between the voltage feedback control and the switch control. A spread spectrum modulator acts as an intermediary that takes the duty cycle control signal and modulates the switching frequency, thereby reducing interference without requiring complete redesign of the power conversion control architecture.
Solution Approach 2:
The patent employs periodic modulation of the switching frequency around a center frequency. By using periodic spread spectrum sequences to vary the frequency, the system achieves interference reduction through distributed spectral energy while maintaining predictable average behavior that simplifies control compared to completely random frequency variation.
Data Source
AI summary
A DC/DC converter includes a converting circuit for converting a first voltage into a second voltage; a controller for generating spread spectrum switching signals; and a switch according to the spread spectrum switching signals controlling the on/off state of the switch.