Boost Converter Pulse Frequency Modulation Audible Noise Control
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Solution Overview
Problem
Display devices often generate audible noise due to switching signals at audible frequencies, which can negatively impact power consumption when attempting to reduce noise while maintaining energy efficiency.
Innovation Solution
A control circuit with a boost converter and timing circuit ensures a minimum switching frequency above audible thresholds by detecting pulses and adjusting the load to maintain a stable frequency, using a current sink to increase the frequency when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the switching frequency of LED signals is reduced to minimize audible noise, then noise reduction is improved, but power consumption increases due to higher charge requirements for switching
Solution Approach 1:
The patent changes the frequency parameter of the switching signal from audible range to ultrasonic range (above 20kHz). This parameter change allows the system to maintain low noise levels while avoiding the energy inefficiency associated with very low frequency switching, as the system operates in an optimal frequency range that balances acoustic performance with power consumption
Solution Approach 2:
The patent implements dynamic frequency adjustment through a PLL (Phase Locked Loop) circuit that can programmably adjust the switching frequency. This allows the system to dynamically optimize the switching frequency based on operating conditions, maintaining it above the audible threshold while minimizing power consumption requirements for LED switching
2Object-affected harmful factors
If the switching frequency is increased to remain above audible thresholds, then noise reduction is improved, but power consumption increases due to higher switching charge requirements
Solution Approach 1:
The patent employs a PLL (Phase Locked Loop) circuit that provides feedback control for the switching frequency. The PLL continuously monitors and adjusts the frequency to maintain it within the desired ultrasonic range, ensuring noise reduction is achieved while optimizing power consumption by avoiding excessive frequency increases that would unnecessarily raise power requirements
Solution Approach 2:
The system uses programmable frequency adjustment to change the switching frequency parameter to specific ultrasonic values. This allows precise control of the frequency parameter to the minimum necessary level above 20kHz, avoiding the power consumption penalty associated with unnecessarily high frequencies while maintaining effective noise reduction
Data Source
AI summary
The embodiments discussed herein relate to systems, methods, and apparatus for executing a pulse frequency modulation (PFM) mode of a boost converter in order to ensure that a switching frequency of the boost converter is a above an audible frequency threshold. In this way, a user operating a display device that is controlled by the boost converter will not be disturbed by audible noises generated at the display device. The PFM mode enforces an audible frequency threshold by using control circuitry designed to increase or decrease the frequency of a pulse signal depending on how the frequency of the pulse signal changes over time. The control circuitry can apply an additional load to the boost converter in order to increase the frequency of the pulse signal when the frequency is approaching the audible frequency threshold.