Resonant Power Conversion Frequency Detection Circuit
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Solution Overview
Problem
LLC-SRC resonant power conversion devices experience unstable output voltage under light loads due to increased operating frequency beyond the second resonant frequency, leading to inefficient energy usage and increased switch operation frequencies.
Innovation Solution
A resonant power conversion device incorporating a frequency detecting circuit that determines if the primary frequency is between the second and third resonant frequencies during light loads, temporarily stopping the control signal output to maintain stable voltage and reduce energy wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the operating frequency is increased to reduce voltage gain under light load, then the voltage gain is reduced, but the output voltage becomes unstable due to parasitic capacitance interference
Solution Approach 1:
The patent implements a feedback control mechanism where the control circuit continuously monitors the output voltage and adjusts the operating frequency accordingly. When light load is detected, the control circuit increases the frequency to reduce voltage gain, and when heavy load is detected, it decreases the frequency to maintain stable output voltage, thus resolving the contradiction between voltage gain control and output stability
Solution Approach 2:
The patent employs dynamic frequency adjustment based on load conditions. The operating frequency is not fixed but varies dynamically according to the load state, allowing the system to optimize voltage gain under light load while maintaining stability under heavy load, effectively resolving the contradiction across different operating conditions
2Power
If the power switches are controlled to stop and start alternatively under light load, then the output voltage is maintained, but the number of switch operations increases causing energy waste
Solution Approach 1:
The patent implements periodic duty cycle adjustment based on load detection. Under light load conditions, the control circuit extends the off-time of power switches, creating a periodic action pattern that maintains output voltage while significantly reducing the number of switch operations and associated energy losses compared to frequent on-off cycling
Solution Approach 2:
The patent changes the duty cycle parameter of power switch control based on detected load conditions. By adjusting the duty cycle to appropriate values under different load states, the system maintains stable output voltage while minimizing unnecessary switch operations and energy waste, resolving the contradiction between voltage maintenance and energy efficiency
3Power
If the operating frequency is increased beyond the second resonant frequency under light load, then the voltage gain control is achieved, but the energy efficiency decreases due to increased switch operations
Solution Approach 1:
The patent employs dynamic frequency adjustment that adapts to load conditions. Under light load, the frequency is increased to control voltage gain, but under heavy load, the frequency is reduced to improve energy efficiency. This dynamic adaptation resolves the contradiction by optimizing the frequency parameter for different operating conditions
Solution Approach 2:
The patent changes the operating frequency parameter based on detected load states and voltage gain requirements. By adjusting the frequency to appropriate values - higher for light load voltage control and lower for heavy load efficiency - the system resolves the contradiction between voltage gain control and energy conversion efficiency across different operating conditions
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 ensures stable output voltage and reduces unnecessary switch operations, optimizing energy efficiency by determining the appropriate frequency range and adjusting the control signal output accordingly.
Implementation Method 1
The resonant inductor Lr, the magnetizing inductor Lm and the resonant capacitor Cr constitute a first resonant frequency ωp
Implementation Method 2
The resonant inductor Lr and the resonant capacitor Cr constitute a second resonant frequency ωr
Implementation Method 3
The resonant inductor Lr, the resonant capacitor Cr and a parasitic capacitor constitute a third resonant frequency ωs
Implementation Method 4
interference by the parasitic capacitance distributed on the high-frequency transformer
Data Source
AI summary
A resonant power conversion device includes a primary side circuit, a frequency detecting circuit, a resonant converting circuit, a secondary side circuit, a secondary detecting circuit, and a control circuit. The primary side circuit receives, according to a control signal having a primary frequency, an input power to output a primary side power. The frequency of the primary side power corresponds to the primary frequency. The frequency detecting circuit detects and converts the primary frequency into a corresponding potential. The resonant converting circuit electrically couples the primary side power to output a resonant power. The secondary side circuit converts the resonant power into a secondary side power. The secondary detecting circuit detects the secondary side power and correspondingly generates a voltage signal. The control circuit outputs the control signal according to the voltage signal, and doesn't output the control signal when the corresponding potential is higher than a predetermined level.