Active Clamp Flyback Input Voltage Dependent Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In quasi-resonant (QR) converters, implementing effective frequency jitter is challenging due to the limited switching frequency range, which restricts the reduction of electromagnetic interference (EMI) in flyback converters operating in discontinuous conduction mode.
Innovation Solution
A power converter design that includes a power switch controlling primary current flow and a time-varying capacitance coupled in parallel, adding frequency jitter to the switching frequency, with a portion varying with input voltage and another as a time-varying function, to spread the switching frequency across a larger range and reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency jitter is implemented in QR converters, then EMI is reduced, but the switching frequency range is limited
Solution Approach 1:
The patent applies dynamics by making the capacitance value time-varying rather than fixed. The capacitance coupled to the power switch changes dynamically during operation, which dynamically adjusts the resonant frequency and enables broader frequency jitter range while maintaining EMI reduction benefits
Solution Approach 2:
The patent changes the parameter of capacitance from a static value to a time-varying value. By modulating the capacitance parameter over time, the system achieves wider switching frequency variation range, thereby improving adaptability while maintaining EMI suppression
2Object-affected harmful factors
If a capacitor is coupled in parallel to the power switch, then frequency jitter is added, but device complexity increases
Solution Approach 1:
The capacitor coupled in parallel to the power switch serves multiple functions: it adds frequency jitter to reduce EMI, it shapes the resonant waveform, and it controls the oscillation period. By making this single component perform multiple functions, the patent avoids adding numerous separate components, thereby limiting the increase in device complexity while achieving EMI reduction
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 introduces frequency jitter, reducing switching losses and electromagnetic interference (EMI) by varying the oscillation period of the resonant waveform, thereby enhancing the efficiency and noise reduction in QR converters.
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
a time-varying capacitance coupled in parallel to the power switch, adding frequency jitter to the switching frequency
Data Source
AI summary
A power converter and control circuit are provided. The control circuit has a power controller for turning on the power switch to maintain a desired output voltage and mode selection switch provides a mode selection signal. Depending on the magnitude of an input voltage of the power converter, in which the mode selection circuit compares the input voltage of the power converter with a reference voltage, a modulation controller is configured to turn on a modulation switch to activate the capacitor according to the mode selection signal.