DC/DC Converter Resonant Control for Wide Load Efficiency
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Solution Overview
Problem
DC/DC converters face challenges in providing output regulation over wide load and line variations while maintaining high efficiency, particularly in applications where the desired DC output voltage ranges, such as in Lithium-ion battery chargers, where input voltages can vary significantly.
Innovation Solution
A DC/DC power converter design featuring a pulse wave generator with switches in a bridge configuration, a transformer with magnetizing inductance, resonant inductors, and a control unit that operates switches at a constant frequency with complementary duty cycles under ZVS conditions, allowing the duty cycle to vary to correlate with the fall and rise transitions of the pulse wave voltage, ensuring responsive output power variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the duty cycle is varied to regulate output power over wide load and line variations, then adaptability is improved, but voltage stress on components increases
Solution Approach 1:
The patent introduces a resonant capacitor connected in parallel with the rectifier as an intermediary component. This resonant capacitor, working with the resonant inductor, creates a resonant circuit that softens voltage transitions and reduces peak voltage stress on the rectifier and other components while enabling duty cycle variation for output regulation.
Solution Approach 2:
The patent utilizes resonant parameters (inductance of resonant inductor and capacitance of resonant capacitor) to create a resonant circuit that modifies the voltage waveform characteristics. By operating at or near the resonant frequency, the circuit achieves softer voltage transitions and reduced peak voltage stress while maintaining adaptability through duty cycle control.
2Loss of energy
If switches are operated at constant frequency with complementary duty cycles under ZVS condition, then efficiency is improved, but control flexibility is reduced
Solution Approach 1:
The patent employs periodic switching action at a constant frequency with complementary duty cycles for the bridge switches. This periodic operation, combined with the resonant circuit, maintains Zero Voltage Switching (ZVS) conditions to minimize switching losses while the duty cycle can still be varied within constraints to provide control flexibility for output regulation.
3Stress or pressure
If resonant inductor is connected in series with secondary winding, then voltage stress is reduced, but device complexity increases
Solution Approach 1:
The patent merges the resonant inductor function with the transformer by integrating the resonant inductor into the transformer structure or using the transformer leakage inductance as the resonant inductor. This integration reduces the number of discrete components while maintaining the voltage stress reduction benefits of the resonant circuit.
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 design effectively regulates output power and voltage across a wide range of input voltages, maintaining high efficiency and adaptability to varying load conditions, while minimizing voltage stress on components.
Implementation Method 1
a resonant inductor connected in series with the secondary winding... a resonant capacitor being either connected in parallel with the rectifier, or connected in parallel with the series connection of the rectifier and the filter... the rise transitions of the pulse wave voltage occur while a reverse voltage across the rectifier is resonantly falling from a ringing peak
Implementation Method 2
a transformer comprising a primary winding, a secondary winding and a magnetizing inductance in parallel with the primary winding
Data Source
AI summary
A DC-DC power converter including: input terminals for receiving an input voltage; a pulse wave generator for generating a pulse wave; a transformer having a primary winding and a secondary winding and a magnetizing inductance; a DC blocking capacitor; a rectifier; a filter capacitor; at least one resonant inductor connected in series with the transformer; a resonant capacitor connected to the rectifier; output terminals; and a control unit for controlling operation of the pulse wave generator such when the duty cycle of the pulse wave voltage varies, high efficiency is maintained.