DC/DC Voltage Converter with Capacitive Pre-Converter and Inductive Post-Regulator
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Solution Overview
Problem
Existing DC/DC converters face inefficiencies and regulation issues when operating near unity voltage conversion ratios, particularly in applications requiring both step-up and step-down conversions, such as lithium-ion battery-powered devices, due to limitations in Buck and boost converters and the need for mode switching, which leads to noise glitches, poor regulation, and dropout problems.
Innovation Solution
A DC/DC voltage converter topology that combines a switched capacitive pre-converter with a switched inductive post-regulator, allowing for efficient operation over a wide range of voltage conversion ratios without mode switching, using a charge pump and Buck converter configurations to maintain high-quality regulation even near unity input-to-output voltage ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mode switching is used in traditional Buck and boost converters to handle both step-up and step-down conversions, then the converter can adapt to different voltage conditions, but noise glitches and regulation quality deteriorate near unity voltage conversion ratios
Solution Approach 1:
The converter is divided into two independent stages: a first stage (capacitive charge pump) that handles gross voltage conversion and a second stage (inductive Buck converter) that provides fine regulation. This segmentation allows each stage to operate optimally without mode switching, maintaining high regulation quality across the full voltage range including unity conversion ratios.
Solution Approach 2:
An intermediate voltage node is introduced between the capacitive pre-converter and inductive post-regulator. This intermediary stage allows the system to transition smoothly between step-up and step-down operation without direct mode switching, eliminating noise glitches while maintaining adaptability.
2Adaptability or versatility
If mode switching is implemented to cover wide voltage range, then voltage adaptability improves, but dropout problems occur near unity conversion ratio
Solution Approach 1:
The conversion function is segmented between capacitive switching for gross voltage change and inductive switching for fine regulation. This allows the second stage to maintain continuous operation without dropout even when the overall conversion ratio approaches unity, as the first stage absorbs the bulk voltage adjustment.
Solution Approach 2:
The capacitive pre-converter performs preliminary voltage adjustment before the inductive regulator. By pre-adjusting the voltage to be close to the target, the second stage operates with minimal adjustment needed, preventing dropout conditions that would occur if a single stage attempted direct unity-ratio conversion.
3Device complexity
If single-stage Buck or boost converter is used, then device complexity is reduced, but efficiency deteriorates when operating outside optimal conversion ratio range
Solution Approach 1:
The converter dynamically adapts its operating point by using the capacitive stage for gross voltage conversion and the inductive stage for fine-tuned regulation. This dynamic two-stage approach maintains high efficiency across the full voltage range, unlike a fixed single-stage converter that would operate inefficiently outside its optimal range.
Solution Approach 2:
The system changes operating parameters by using capacitive switching for large voltage steps and inductive switching for small adjustments. This parameter change strategy allows each stage to operate in its optimal efficiency region, maximizing overall conversion efficiency while managing the increased device complexity.
4Adaptability or versatility
If mode switching is used to handle voltage variations, then adaptability improves, but noise glitches increase
Solution Approach 1:
The conversion process is segmented into capacitive switching (high-frequency, high-voltage-step) and inductive switching (lower-frequency, fine-adjustment). This segmentation isolates the noisy capacitive switching from the regulation function, allowing adaptability while minimizing noise transfer to the output.
Solution Approach 2:
The intermediate voltage node acts as a buffer that isolates the noisy capacitive switching from the sensitive inductive regulation stage. This intermediary filtering reduces noise glitches in the final output while maintaining the adaptability benefits of mode switching in the first stage.
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 enables efficient up-down conversion without mode switching, avoiding noise glitches and dropout issues, maintaining high regulation quality across a wide range of voltage ratios, and improving overall efficiency compared to traditional Buck and boost converters.
Implementation Method 1
The pre-converter includes a switched capacitive circuit
Implementation Method 2
the post-regulator includes a switched inductive circuit
Data Source
AI summary
A DC/DC converter includes a pre-converter stage, which may include a charge pump, and a post-regulator stage, which may include a Buck converter. The duty factor of the post-regulator stage is controlled by a feedback path that extends from the output terminal of the DC/DC converter to an input terminal in the post-regulator stage. The pre-converter steps the input DC voltage up or down by a positive or negative integral or fractional value, and the post-regulator steps the voltage down by a variable amount depending on the duty factor at which the post-regulator is driven. The converter overcomes the problems of noise glitches, poor regulation, and instability, even near unity input-to-output voltage conversion ratios.