Input Voltage Adaptive Jitter Power Converter EMI Reduction
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Solution Overview
Problem
In quasi-resonant (QR) converters, implementing effective frequency jitter is challenging due to the turn-on condition at a valley point of the resonant voltage, which limits the switching frequency range and reduces the effectiveness of jittering techniques in reducing electromagnetic interference (EMI).
Innovation Solution
A power converter with a time-varying capacitance coupled in parallel to the power switch, where the capacitance varies with input voltage and includes a modulation switch to introduce frequency jitter, allowing the switching frequency to spread across a larger frequency range by varying the oscillation period of the resonant waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency jitter is implemented in quasi-resonant converters, then electromagnetic interference (EMI) is reduced, but the switching frequency range is limited by the valley point turn-on condition
Solution Approach 1:
The patent applies dynamics by making the capacitance value time-varying rather than fixed. The capacitance C(t) changes over time according to a periodic function, which dynamically adjusts the resonant frequency and enables broader switching frequency range while maintaining EMI reduction benefits through continuous frequency variation.
Solution Approach 2:
The patent changes the capacitance parameter from a constant value to a time-varying parameter C(t). This parameter change allows the resonant frequency to vary continuously, enabling the switching frequency to spread across a larger range and improving the effectiveness of EMI reduction through frequency modulation.
2Object-affected harmful factors
If traditional frequency jittering is used, then EMI is reduced, but power efficiency is not improved due to limited frequency range
Solution Approach 1:
The time-varying capacitance creates dynamic frequency modulation that optimizes the switching frequency at different operating conditions. This dynamic adjustment ensures that the converter operates at optimal efficiency points while maintaining EMI reduction, thereby improving power efficiency without sacrificing EMI performance.
Solution Approach 2:
By changing the capacitance parameter over time, the system achieves broader frequency modulation range that enables both EMI reduction and power efficiency improvement. The parameter change allows the system to adapt switching frequency to operating conditions, reducing switching losses while maintaining EMI suppression.
3Device complexity
If fixed capacitance is used in parallel with power switch, then circuit simplicity is maintained, but frequency jitter effectiveness is limited
Solution Approach 1:
The patent introduces a time-varying capacitance function C(t) that can be implemented using practical circuit elements such as switches and capacitors controlled by periodic signals. This dynamic approach maintains reasonable circuit complexity while achieving effective frequency jitter for EMI reduction through continuous frequency variation.
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 approach effectively reduces electromagnetic interference (EMI) by introducing frequency jitter in the switching frequency, improving power efficiency and reducing switching losses, especially at high input voltages.
Implementation Method 1
a resonant waveform of substantially sinusoidal oscillation of decreasing amplitude appears at the secondary winding and across the power switch due to the built-in inductance and capacitance in the converter
Implementation Method 2
Magnetic energy is stored in the inductance of the primary winding when the switch is turned on
Data Source
AI summary
A power converter includes a power switch controlling current flow in the power converter and a variable capacitance coupled in parallel to the power switch. The variable capacitance is configured to add a frequency jitter to the power converter.