Auxiliary Buck Converter Control for Low Output Voltage Ripple
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Solution Overview
Problem
Buck converters face limitations in reducing output voltage ripple and achieving high efficiency, especially when using hard switching methods, and require complex designs and control methods, especially when load currents are non-stepwise.
Innovation Solution
A DC-DC converter system incorporating a main buck converter and an auxiliary buck converter with a capacitor and inductors, using double envelope control to generate and select inductor currents as triangular waves to compensate for output current differences, implemented either analogically or digitally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hard switching method is used to control auxiliary circuit operation, then device complexity is reduced, but power conversion efficiency deteriorates
Solution Approach 1:
The patent changes the switching parameter from hard switching to resonant soft switching, utilizing the natural resonance of the LC circuit to achieve zero-voltage or zero-current switching. This transforms the switching process from a forced operation to a naturally synchronized operation, reducing switching losses and improving power conversion efficiency while maintaining relatively simple control logic.
Solution Approach 2:
The auxiliary circuit operates in periodic resonance cycles, where the switch is turned on and off at specific phases of the resonant waveform. This periodic action allows the circuit to naturally charge and discharge the capacitor through the inductor, creating continuous current flow that reduces energy loss and improves efficiency without complex control mechanisms.
2Loss of energy
If soft switching method is used to control auxiliary circuit operation, then power conversion efficiency is improved, but device complexity and control difficulty increase
Solution Approach 1:
The resonant circuit is designed to self-oscillate at its natural frequency, eliminating the need for complex external control circuits to generate switching signals. The circuit automatically regulates its own switching timing based on the resonance condition, where the inductor and capacitor naturally determine the switching rhythm, thereby achieving soft switching without proportionally increasing control complexity.
3Stability of the object's composition
If auxiliary circuit is added to reduce output voltage ripple, then output voltage stability is improved, but device complexity increases
Solution Approach 1:
The auxiliary circuit components (inductor and capacitor) serve multiple functions: they reduce output voltage ripple, improve power conversion efficiency through resonant switching, and provide automatic current regulation. By making the auxiliary circuit multi-functional, the patent achieves voltage stabilization without proportionally increasing overall system complexity, as the same components address multiple problems simultaneously.
Solution Approach 2:
The auxiliary resonant circuit is merged with the existing DC-DC converter topology, sharing common components such as the output capacitor and control signals. This integration allows the ripple reduction function to be achieved without adding completely separate circuitry, thereby minimizing the increase in device complexity while maintaining output voltage stability.
4Device complexity
If conventional buck converter is used without auxiliary circuit, then device complexity is reduced, but output voltage ripple reduction capability deteriorates
Solution Approach 1:
The auxiliary circuit performs preliminary current regulation by continuously charging and discharging the capacitor through resonant oscillation, proactively compensating for voltage ripples before they affect the output. This preliminary action maintains smooth current flow and prevents voltage fluctuations, achieving ripple reduction with minimal additional circuitry.
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 effectively minimizes output voltage ripple and maintains constant output voltage even with fluctuating load currents, achieving high efficiency and precision while simplifying the control method.
Implementation Method 1
a capacitor (Co) configured to perform charging and discharging
Implementation Method 2
a first inductor (L1) connected between a contact point of the first switch and the second switch and the capacitor so that a first inductor current (iL1) flows therethrough
Data Source
AI summary
An auxiliary circuit for reducing an output voltage ripple of a DC-DC converter includes: a capacitor configured to perform charging and discharging, a main buck converter including a first switch and a second switch connected to a voltage source, and a first inductor connected between the capacitor and a contact point of the first switch and the second switch, the first inductor having a first inductor current that flows therethrough, and an auxiliary buck converter including a third switch and a fourth switch respectively connected to the first switch and the second switch in parallel, and a second inductor connected between the capacitor and a contact point of the third switch and the fourth switch, the second inductor having a second inductor current that flows therethrough, and the auxiliary buck converter configured to control the second inductor current by generating two envelopes with different heights to compensate for a difference between the first inductor current and an output current.