LLC Converter Piecewise Linear Control for Wide Power Range
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Solution Overview
Problem
Conventional LLC converters face limitations in achieving a wide dynamic range of output power due to non-linear switching frequency control and high rising slope of output current, especially at low power requirements, leading to inefficiencies and inability to meet output specifications, especially at low load conditions.
Innovation Solution
A piece-wise linear control system that adjusts output power by tuning the duty cycle and pulse width of switching in an LLC converter, allowing for broad dynamic range and precise control of output voltage and current by varying the time periods of charging and discharging the capacitor, thereby overcoming the limitations of conventional switching methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the operational switching frequency is increased to reduce the volume of magnetic components, then the volume of magnetic components is reduced, but switching losses increase
Solution Approach 1:
The patent changes the switching method from hard switching to zero-voltage switching (ZVS), fundamentally altering the switching parameter to eliminate voltage across the switch during switching transitions. This allows high-frequency operation with minimal switching losses, resolving the contradiction between reduced component volume and energy loss.
2Volume of moving object
If the operational switching frequency is increased to achieve miniaturization, then the volume of circuits is reduced, but heat dissipation component volume increases
Solution Approach 1:
By implementing zero-voltage switching, the patent eliminates the primary source of switching losses that would require heat dissipation components. This enables high-frequency operation that miniaturizes circuits without increasing heat dissipation component volume, as the switching losses are reduced to near zero.
3Speed
If the operational switching frequency is increased to maintain output voltage under low load conditions, then the gain curve becomes flatter, but output voltage specification requirements are not met
Solution Approach 1:
The patent implements zero-voltage switching which fundamentally changes the switching characteristics, eliminating the flat gain curve problem at low loads. By ensuring voltage is zero during switching transitions, the system maintains proper voltage transfer ratios across the entire load range, meeting output voltage specifications even at low power requirements.
4Adaptability or versatility
If duty cycle and pulse width are both adjusted to control output power, then the dynamic range is broadened, but control system complexity increases
Solution Approach 1:
The patent implements dynamic control where both duty cycle and pulse width are adjusted based on operating conditions. The controller dynamically modifies switching parameters to maintain optimal performance across the full dynamic range, achieving broad adaptability while managing complexity through coordinated parameter adjustment.
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 system provides a wide dynamic range of output power control, enabling efficient operation across varying input voltages and loads, reducing switching losses, and maintaining output voltage specifications even at low power requirements, thus enhancing the operational efficiency and miniaturization of power supplies.
Implementation Method 1
a capacitor coupled in series with mutual inductors. A charging of the capacitor is controlled by switching of a pair of switches... The capacitor is charged during ton and discharged during toff
Implementation Method 2
inductor-inductor-capacitor (LLC) converter... a capacitor coupled in series with mutual inductors
Data Source
AI summary
A control system controls an inductor-inductor-capacitor (LLC) converter according to a switching method that tunes the output power of the LLC converter based on the required power to be supplied to an output load coupled to the LLC converter. The tuning of the output power is based in part on changing the duty cycle of a switching module. In addition, the output power is adjustable by changing a frequency of switching (e.g., a pulse width of the switching module output). The control system is capable of adjusting amplitude and changing rising slope of a current supplied to the output load by changing the duty cycle and pulse width of the switching. A piece-wise linear control method is achieved by controlling the duty cycle and pulse width differently when the input voltage is lower than a crossover voltage than when the input voltage is higher than the crossover voltage.