DC-DC Converter PWM Frequency Control for Noise Reduction

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Solution Overview

Problem

Conventional DC-DC converters experience a decrease in operating frequency of PWM signals when load variations occur, leading to noise interference as the frequency falls within the human-hearable range, affecting the utilization quality of electronic products.

Innovation Solution

A DC-DC converter with an adjustment module, output module, and control module that detects the frequency of the PWM signal and adjusts the pulse width to maintain the operating frequency above the human-hearable range by controlling the output voltage and switching the input voltage, using components like transistors, inductors, and digital control circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the COT regulator reduces the PWM signal frequency under light load conditions, then the distance between pulses is increased, but the frequency falls into the human-hearable range causing noise interference

Engineering Contradiction:

Improvedistance between pulsesVSAvoidnoise interference

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent changes the operating parameters of the PWM signal by dynamically adjusting the frequency based on load conditions. When the load becomes very light, instead of allowing the frequency to drop naturally, the system modifies the timing parameters to keep the frequency above 25 KHz, thus avoiding the human-hearable range while maintaining adequate pulse spacing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic frequency adjustment where the PWM operating frequency is not fixed but adapts based on real-time load conditions. The system transitions from a static frequency approach to a dynamic one that responds to load variations, ensuring the frequency remains in the ultrasonic range even under light load conditions

Inventive Principle:

Principle #15Dynamics

2Object-affected harmful factors

If the COT regulator increases the PWM signal frequency to avoid noise interference, then the operating frequency remains above human-hearable range, but the voltage conversion efficiency may be influenced

Engineering Contradiction:

Improvenoise interferenceVSAvoidvoltage conversion efficiency

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The patent applies partial action by selectively adjusting the PWM frequency only under specific light load conditions rather than maintaining a constantly high frequency. This partial adjustment is sufficient to push the frequency above the human-hearable range while avoiding excessive frequency increases that would harm conversion efficiency

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system dynamically balances frequency and efficiency by continuously monitoring load conditions and adjusting the PWM frequency accordingly. The frequency is increased only when necessary to avoid noise interference, and reduced when load conditions allow, thus optimizing the trade-off between noise reduction and voltage conversion efficiency

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8742745B2DC-DC converter and voltage conversion method thereof

Publication Date: 2014.06.03 UPI SEMICON CORP

AI summary

A DC-DC converter is provided. When a load of the DC-DC converter is too light, the DC-DC converter can raise a frequency of its PWM signal, and reduce a pulse width of the PWM signal, so as to avoid the frequency of the PWM signal falling into a frequency range that can heard by human's ear and maintain high conversion efficiency of the DC-DC converter.