Valley Switching Power Controller Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching-mode power supplies operating in quasi-resonance (QR) mode often generate audible noise due to unstable operation and valley switching, which affects power conversion efficiency and user acceptance.
Innovation Solution
A power controller that detects the occurrence number of signal valleys and adjusts the start moment of the cycle time based on an expectation window, using a lock number mechanism to select the appropriate signal valley for switching, thereby stabilizing the operation and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If valley switching is used in QR-mode power supply, then power conversion efficiency is improved, but audible noise is generated due to unstable operation
Solution Approach 1:
The patent implements dynamic adjustment of the blanking time period based on the detected signal valley characteristics. The controller dynamically selects between different blanking time periods (first or second) depending on whether the signal valley occurs within an expectation window, allowing the system to adapt to varying operating conditions and maintain stability while preserving efficiency benefits
Solution Approach 2:
The patent employs feedback mechanisms by detecting signal valleys and using this information to control the power switch timing. The controller monitors the auxiliary winding voltage, identifies signal valleys, and uses this feedback to determine optimal switching moments, ensuring both efficiency and noise reduction through closed-loop control
2Object-generated harmful factors
If the blanking time period is extended to reduce switching frequency, then audible noise is reduced, but power conversion efficiency deteriorates
Solution Approach 1:
The patent dynamically adjusts the blanking time period based on real-time detection of signal valley positions. When signal valleys occur within the expectation window, a shorter first blanking time period is used to maintain efficiency. When valleys occur outside the window, a longer second blanking time period is applied to reduce noise, optimizing the trade-off between efficiency and noise reduction adaptively
Solution Approach 2:
The patent changes the blanking time period parameter based on operating conditions. By switching between two distinct blanking time period values (first and second) depending on signal valley detection results, the system optimizes the balance between power conversion efficiency and audible noise reduction for different load and voltage conditions
3Loss of energy
If valley switching is implemented, then zero-voltage switching is achieved, but operation becomes unstable causing noise
Solution Approach 1:
The patent uses feedback control by continuously monitoring the auxiliary winding voltage to detect signal valleys. This detection feedback ensures that the power switch is turned on at the correct moment (at or near zero voltage), maintaining zero-voltage switching benefits while the expectation window mechanism provides stability by defining acceptable timing ranges
Solution Approach 2:
The patent establishes the expectation window in advance as a reference range for acceptable signal valley positions. By preparing this timing window beforehand and comparing actual signal valley occurrences against it, the system can determine whether to use shorter or longer blanking times, proactively preventing instability before it occurs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes audible noise and stabilizes the operation of QR-mode power supplies, ensuring efficient power conversion and improved user acceptance by adjusting the cycle timing to align with the expectation window.
Implementation Method 1
a transformer is an inductive device with a primary winding PRM, a secondary winding SEC and an auxiliary winding AUX, inductively coupled to one another
Implementation Method 2
A switching-mode power supply normally uses s power switch to control the current through an inductive device, such as an inductor or a transformer
Data Source
AI summary
Control methods and related power controllers diminish audible noise in a power supply capable of performing valley switching. The power supply has an inductive device and a power switch. When the power switch is OFF, a winding voltage of the inductive device oscillates to provide an oscillation signal with at least one signal valley. An occurrence number of the signal valley is detected, and is compared with a lock number. When the occurrence number and the lock number fit a predetermined condition, the power switch is turned ON to start a cycle time at a start moment. Whether the start moment falls within an expectation window is checked. The lock number is changed if the start moment falls outside of the expectation window.