Soft-Start Control Circuits for DC-DC Converter Inrush Current
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Solution Overview
Problem
DC-DC converters with multiple control signals, such as those used in charging circuits for secondary batteries, face challenges in preventing inrush currents due to uncontrolled switching states and prolonged times before control signals adjust between voltage and current control, leading to excessive current flow.
Innovation Solution
A DC-DC conversion circuit with multiple control signal generation circuits and soft-start control circuits that manage the transition of control signals at startup, ensuring controlled voltage and current adjustments, utilizing additional components like current measurement resistors and soft-start capacitors to regulate the output signals and prevent inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple control signals are used to control output voltage and current, then the DC-DC converter can achieve versatile output control, but the switching state becomes uncontrolled and inrush currents occur
Solution Approach 1:
The patent applies preliminary action by introducing soft-start control circuits that activate before the main control signals to establish a controlled initial state. The soft-start circuits gradually ramp up the control voltages, ensuring that switching elements transition smoothly from off-state without sudden inrush currents, thereby preventing uncontrolled switching while maintaining versatile output control capability
2Reliability
If the control signal adjustment time is prolonged to ensure stable transitions, then the switching state control is improved, but the uncontrolled state duration increases leading to efficiency loss
Solution Approach 1:
The patent applies dynamics by making the control signal adjustment speed variable rather than fixed. The soft-start control circuits dynamically adjust the ramp rate of control voltages based on real-time feedback from current detection circuits, accelerating the transition when safe and slowing down when needed, thereby optimizing both reliability and response speed without prolonged uncontrolled states
3Reliability
If soft-start control circuits are added to manage control signal transitions, then inrush currents are prevented, but the device complexity increases
Solution Approach 1:
The patent applies merging by integrating the soft-start control circuits with the existing control signal generation structure. Rather than adding completely separate control paths, the soft-start functionality is combined with the voltage and current control circuits, sharing common components such as operational amplifiers and feedback networks, thereby achieving inrush current prevention while minimizing the increase in device complexity
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 configuration effectively shortens the uncontrolled state duration and prevents inrush currents by ensuring synchronized and controlled transitions between voltage and current control modes, enhancing the stability and efficiency of the DC-DC converter.
Implementation Method 1
a soft-start capacitor CS1, and a control circuit CTL. One end of the soft-start capacitor CS1 is connected to a second non-inverting input pin between a first and second non-inverting input pins of an error amplifier ERA1 in the control circuit CTL. The other end of the soft-start capacitor CS1 is connected to a ground line.
Implementation Method 2
a current measurement resistor RS and a soft-start capacitor CS2. One end of the current measurement resistor RS is connected to the other end of the smoothing capacitor C1. The other end of the current measurement resistor RS is connected to the negative electrode terminal of the secondary battery BTR.
Data Source
AI summary
A DC-DC conversion circuit is configured by including a plurality of control signal generation circuits, a plurality of soft-start control circuits, and a start control circuit. The plurality of control signal generation circuits correspond to the plurality of control signals, and generate a corresponding control signal of the plurality of control signals based on a corresponding output value of a plurality of output values. The plurality of soft-start control circuits correspond to the plurality of control signals, and control a variation of the corresponding control signal at a start time of the DC-DC conversion circuit. The start control circuit instructs the corresponding soft-start control circuit to start operation in accordance with a change of the control signal taking part in an output control at the start time of the DC-DC conversion circuit.