Boost Converter Startup Soft Start for In-Rush and Overshoot Control
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Solution Overview
Problem
Conventional DC-DC converters experience high in-rush currents during startup, leading to component degradation and output voltage overshoot, necessitating high-power components and increased system cost, while untrimmed devices and uncontrolled startup can cause switch failure.
Innovation Solution
A multi-phase startup mode with RC charging, oscillating signal control, and output voltage monitoring to limit in-rush current and overshoot, coupled with ultra-low leakage shutdown and bulk switching to prevent excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional DC-DC converter startup is used, then output voltage can be generated quickly, but high in-rush current degrades components and increases system cost
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor through a dedicated path before enabling the main boost converter switches. This preliminary charging action reduces the initial in-rush current when the converter starts, protecting components while still achieving quick startup. The control circuit enables the pre-charge path before normal operation begins.
Solution Approach 2:
The startup process is segmented into distinct phases: a pre-charge phase where the output capacitor is charged through a controlled path, and a normal operation phase where the main converter takes over. This segmentation allows the system to manage in-rush current separately from the main power transfer, reducing component stress while maintaining productivity.
2Productivity
If conventional DC-DC converter startup is used, then power conversion can begin immediately, but output voltage overshoot causes switch breakdown
Solution Approach 1:
The patent implements feedback control during startup by monitoring the output voltage and adjusting the pre-charge current accordingly. When the output voltage approaches the target level, the control circuit reduces or stops the pre-charge current, preventing voltage overshoot that could damage switches. This feedback mechanism maintains reliability while enabling quick power conversion startup.
Solution Approach 2:
The control circuit performs preliminary voltage monitoring and adjustment before full power conversion begins. By establishing controlled voltage levels in advance through the pre-charge path and regulating them before main operation starts, the system prevents overshoot conditions that would threaten switch reliability.
3Reliability
If high-power components are used to sustain in-rush current, then component reliability improves, but system cost increases
Solution Approach 1:
The patent uses preliminary pre-charge action to establish output voltage before main operation, which reduces peak in-rush current requirements. This allows the use of lower-power, lower-cost components while maintaining reliability, as the expensive high-power components are only needed for brief moments during phase transitions rather than sustaining continuous high current.
Solution Approach 2:
By segmenting the power delivery into pre-charge and normal operation phases, the patent reduces the maximum current any single component must handle continuously. This segmentation allows cheaper components to be used for the pre-charge function while only the main power path requires higher-power components, reducing overall system cost while maintaining reliability.
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
Reduces peak in-rush current, limits voltage overshoot, and maintains stable output voltage during startup, thereby reducing component stress and system cost, while extending battery life and eliminating the need for additional protection circuits.
Implementation Method 1
charging an output capacitance coupled to an output node of the DC-DC converter circuit at a first rate in a first phase of a multi-phase startup mode of operation... The first rate may be the rate of charging an RC circuit including the output capacitance coupled to the output node
Implementation Method 2
controlling a current through an inductor using an oscillating signal in a second phase of the multi-phase startup mode of operation, thereby adjusting the output voltage to equal a target voltage level
Data Source
AI summary
A method for operating a DC-DC converter circuit includes, in response to detecting a startup condition, charging an output capacitance coupled to an output node of the DC-DC converter circuit at a first rate in a first phase of a multi-phase startup mode of operation of the DC-DC converter circuit. The method includes, in response to an indication of an output voltage on the output node approaching an input voltage on an input node of the DC-DC converter circuit, controlling a current through an inductor using an oscillating signal in a second phase of the multi-phase startup mode of operation, thereby adjusting the output voltage to equal a target voltage level. The first rate may be the rate of charging an RC circuit including the output capacitance coupled to the output node.