Slew Rate Control for DC/DC Converter Rush Current Reduction
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Solution Overview
Problem
Current methods for controlling the slew rate of DC/DC converters at high speeds result in increased rush current and overshoot, which cannot be sufficiently reduced by existing techniques.
Innovation Solution
A slew rate control device and method that adjusts the slew rate to become slower as the output voltage approaches the target voltage, using a setting part to determine the voltage value and a control part to manage the slew rate, thereby reducing rush current and overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the slew rate is increased to achieve high-speed startup and shutdown of the DC/DC converter, then the switching speed is improved, but the rush current and overshoot increase
Solution Approach 1:
The patent applies dynamics by making the slew rate adjustable rather than fixed. The control circuit dynamically changes the slew rate based on the operating state: using a first (faster) slew rate during normal operation and a second (slower) slew rate during startup and shutdown transitions. This dynamic adjustment resolves the contradiction by allowing high switching speed during normal operation while reducing rush current and overshoot during critical transition phases.
Solution Approach 2:
The patent changes the slew rate parameter according to the operating condition. By detecting whether the DC/DC converter is in a startup/shutdown state or normal operation state, the control circuit selects different slew rate values. This parameter change strategy allows the system to optimize performance for each operating phase, achieving high switching speed when needed while minimizing harmful effects during transitions.
2Device complexity
If a fixed slew rate control method is used, then the control simplicity is maintained, but the rush current and overshoot cannot be sufficiently reduced
Solution Approach 1:
The patent segments the operating conditions into distinct states: startup/shutdown state and normal operation state. By dividing the control into these segments, the system can apply different slew rate values appropriate for each state. This segmentation approach maintains relative control simplicity while effectively reducing rush current and overshoot during critical transition phases, unlike a single fixed slew rate approach.
Solution Approach 2:
The patent implements feedback by having the control circuit detect the operating state of the DC/DC converter and adjust the slew rate accordingly. The control circuit monitors whether the converter is in startup/shutdown or normal operation and automatically selects the appropriate slew rate. This feedback mechanism enables the system to reduce harmful effects without requiring complex external control, maintaining ease of implementation.
Data Source
AI summary
A slew rate control device for controlling a slew rate, includes: a setting part configured to set a voltage value used to determine the slew rate; and a control part configured to control the slew rate, based on the voltage value set by the setting part, so that the slew rate becomes slower as an output voltage of a power supply approaches from a transition starting voltage to a target voltage.