Quasi-Resonant Switching Converter Peak Current Control
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Solution Overview
Problem
Switching converters with quasi-resonant control experience audible noise due to frequency hopping phenomena at certain load and input conditions, which is a result of their intrinsic output characteristics.
Innovation Solution
A switching converter with a peak current comparing circuit and a first logic circuit that generates a switching control signal based on a frequency control signal and current control signal, adjusting the peak current signal or current sense signal when operating under non-current continuous-mode and when the switch voltage is higher than a valley reference signal, to achieve valley-switching and reduce audible noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If quasi-resonant control is used to reduce switching loss, then switching efficiency is improved, but audible noise is generated due to frequency hopping phenomena
Solution Approach 1:
The patent implements a feedback mechanism by comparing the actual switch-on voltage with a valley reference voltage. When the switch voltage is higher than the valley reference (indicating non-valley switching), the peak current limit is adjusted in the next cycle to ensure valley switching is achieved, thereby eliminating audible noise while maintaining QR control benefits
Solution Approach 2:
The control circuit automatically detects and corrects non-valley switching conditions by using the actual switch-on voltage information to adjust the peak current limit signal. The system self-regulates to maintain optimal switching conditions without external intervention, ensuring valley switching is achieved under varying operating conditions
2Productivity
If variable frequency control is used to overcome fixed frequency limitations, then switching efficiency is improved, but frequency hopping phenomena occur causing audible noise
Solution Approach 1:
The patent dynamically adjusts the peak current limit parameter based on the actual switch-on voltage conditions. By changing this critical parameter in response to operating conditions, the system maintains efficient variable frequency operation while preventing the frequency hopping that causes audible noise
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
This solution eliminates audible noise while maintaining stable switching frequency, and the converter remains compatible with continuous-current-mode operation, improving efficiency and reducing switching losses.
Implementation Method 1
When a current sense signal Ic indicative of a current flowing through the energy storage component decreases to zero, the energy storage component resonates with the parasitic capacitance of the switch
Data Source
AI summary
A switching converter with quasi-resonant control having a switch and an energy storage component, comprising a peak current regulating circuit configured to provide a peak current regulating signal to regulate a peak current signal or a current sense signal, wherein the peak current regulating signal is adjusted when non-CCM (Current Continuous Mode) and non-valley-switching are detected.