LLC Converter Control Using Phase-Frequency Modulation
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Solution Overview
Problem
LLC converters used in electric vehicles and plug-in hybrid vehicles face challenges in maintaining stable output gain control across varying loads due to their characteristic of increasing switching frequency at light loads when frequency control is applied.
Innovation Solution
A power conversion device and method utilizing a complex modulation scheme that includes phase modulation and frequency modulation modes, controlled by a controller to manage the switching units of a transformer's bridge switching units and resonance circuits, ensuring stable output gain from light to full load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable frequency control method is applied to LLC converter, then output voltage can be controlled, but switching frequency increases greatly at light load
Solution Approach 1:
The patent applies parameter changes by switching between two control modes: phase modulation mode for light loads and frequency modulation mode for heavy loads. This resolves the contradiction by changing the control parameter (phase difference vs. switching frequency) according to load conditions, preventing excessive frequency increase at light load while maintaining output voltage control capability.
Solution Approach 2:
The patent implements dynamic control by automatically switching between phase modulation and frequency modulation modes based on load detection. The controller dynamically adjusts the control strategy according to real-time load conditions, optimizing performance across the entire operating range and avoiding the drawback of fixed frequency control methods.
2Adaptability or versatility
If frequency control is used in LLC converter, then output gain can be adjusted, but output variation slope according to load becomes gentle
Solution Approach 1:
The patent changes the control parameter based on load conditions: using phase difference modulation for light loads to achieve steep output variation response, and frequency modulation for heavy loads to maintain output gain adjustment capability. This resolves the contradiction by optimizing the control parameter for each operating condition.
Solution Approach 2:
The patent implements dynamic mode switching between phase modulation and frequency modulation based on load detection. This dynamic adaptation allows the system to achieve both steep output variation response at light loads and adequate output gain adjustment at heavy loads, resolving the productivity-adaptability contradiction.
3Reliability
If complex modulation scheme with phase and frequency modulation is implemented, then stable output gain control is achieved, but device complexity increases
Solution Approach 1:
The patent segments the control range into two parts: light load range controlled by phase modulation and heavy load range controlled by frequency modulation. This segmentation allows each mode to operate in its optimal range, achieving stable output gain control while keeping individual mode complexity manageable through clear division of control responsibilities.
Solution Approach 2:
The patent uses dynamic mode switching to implement complex modulation only when necessary. The controller automatically selects the appropriate control mode based on load conditions, achieving reliable output gain stability across the full operating range while maintaining implementation feasibility through automated mode selection rather than continuously complex control.
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 complex modulation scheme allows for stable output gain control across the entire load range by synchronizing the switching elements and modulating phase and frequency, reducing frequency at light loads and maintaining efficiency.
Implementation Method 1
The LLC converter generally includes a resonant circuit (i.e., a resonant tank) composed of a resonant inductance (Lr), a magnetization inductance (Lm), and a resonant capacitance (Cr). When the resonant circuit operates at a resonant frequency (e.g., if the output gain is 1), the LLC converter may have the highest efficiency.
Implementation Method 2
a first bridge switching unit which is connected to a primary side coil of a transformer and performs full bridge switching; a first resonance circuit unit comprising a first capacitor and a first inductor disposed between the primary side coil of the transformer and the first bridge switching unit
Data Source
AI summary
There may provide a power conversion device and method capable of performing control of a stable output gain from a light load to a full load by controlling using a complex modulation method in which a phase modulation mode and a frequency modulation mode are performed by a controller.