Switching Power Supply Ringing Suppression Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Switching power supplies, particularly Quasi Resonant Flyback converters, generate audible noise due to low-frequency jittering caused by variations in ringing suppression times, maximum on and off times, and switching periods, leading to inaccurate timing and potential failure to meet output load requirements, with existing methods requiring large die areas and inaccurate noise suppression.
Innovation Solution
A digital circuit is used to accurately control the ringing suppression time by generating synchronized maximum on time and switching period signals, converting the ringing suppression time to a digital mode, and using counters to set precise timing, thereby eliminating audible noise and reducing circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ringing suppression time is extended to eliminate audible noise, then noise suppression is improved, but the feedback loop response time increases and system performance deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of ringing suppression time based on operating conditions. The controller monitors system state and adaptively modifies the suppression duration, allowing short suppression times during transient conditions (maintaining feedback responsiveness) and longer suppression times during steady-state operation (eliminating audible noise). This dynamic approach resolves the contradiction by making the suppression time flexible rather than fixed.
2Manufacturing precision
If timing parameters are individually trimmed for precision, then manufacturing precision is improved, but device complexity and die area increase
Solution Approach 1:
The patent changes the approach from individual parameter trimming to a unified timing control mechanism. Instead of separately trimming ringing suppression time, maximum on time, and maximum switching period, the invention uses a single controller that generates all timing signals based on a unified algorithm. This parameter transformation approach achieves high timing precision without requiring multiple trim circuits, thereby reducing die area and circuit complexity while maintaining manufacturing precision.
3Object-affected harmful factors
If switching frequency is reduced to meet maximum switching period requirements, then noise suppression is improved, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent implements dynamic switching frequency adjustment that responds to load conditions and timing constraints. The controller monitors the actual switching period and dynamically modifies the switching frequency to maintain it below the audible threshold (20 kHz) while optimizing for efficiency. During light loads, the frequency can be reduced more aggressively to ensure noise suppression, while during heavy loads, the frequency is adjusted to the minimum necessary to handle the power transfer requirements, thereby minimizing switching losses across all operating conditions.
Data Source
AI summary
This disclosure relates to a switching power supply with regulated voltage suppression to reduce transformer audio noise. The switching power supply is operable to be fed a zero crossing voltage and to generate an output voltage. The output voltage may have a voltage level set using a modulated gate signal. A circuit is provided to reduce audio noise in a switching power supply by setting a ringing suppression time of the modulated gate signal to a first time period when the zero crossing voltage is below a predetermined voltage threshold and to a second time when the zero crossing voltage is above the predetermined threshold voltage.