Soft-Start Power Supply Inrush Current Protection
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Solution Overview
Problem
Power supply apparatuses with high power face issues due to inrush currents generated by voltage stabilizing capacitors, leading to erroneous short circuit protection activation, potential damage, and reduced reliability, especially when loads with internal short circuits are connected, causing repeated safety hazards.
Innovation Solution
A power supply apparatus with a soft-start function and protection mechanism, incorporating a power unit, soft-start adjusting unit, current detecting unit, and controlling unit, which monitors and adjusts the current to prevent inrush currents, detects short circuits, and implements protection measures to avoid erroneous activation and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a main power switch suddenly starts to work, then the power supply apparatus can provide power to the load, but the large capacitors of the voltage stabilizing circuit generate a huge inrush current that may cause erroneous short circuit protection activation
Solution Approach 1:
The patent implements a soft-start function that pre-charges the voltage stabilizing capacitors through a current-limiting resistor before the main power switch fully activates. This preliminary action limits the inrush current by controlling the charging process, preventing erroneous short circuit protection activation while still enabling rapid power delivery to the load.
2Reliability
If the soft-start function is finished without a load connected, then the power supply apparatus generates power voltage at the output end, but connecting the load subsequently causes a huge inrush current that triggers erroneous short circuit protection
Solution Approach 1:
The patent employs a control circuit that continuously monitors the output voltage and load connection status. When a load is detected after soft-start completion, the control circuit re-activates the current-limiting mechanism, providing adaptive feedback control that prevents inrush current while allowing normal power delivery during steady-state operation.
Solution Approach 2:
The patent makes the power supply system dynamic by allowing the soft-start circuit to be re-triggered based on load detection. The system transitions from a static soft-start state to an adaptive state where the current limiting mechanism is dynamically re-applied when loads are connected, preventing inrush current while maintaining power voltage generation capability.
3Productivity
If the protection mechanism is removed or the protection point is raised to ensure continuous power supply, then the power supply apparatus can operate without erroneous protection activation, but the inrush current may damage the power supply apparatus and internal components
Solution Approach 1:
The patent introduces a current-limiting resistor as an intermediary element between the power source and the voltage stabilizing capacitors. This intermediary component safely dissipates the inrush current energy during startup and load connection, protecting the power supply apparatus and internal components from damage while allowing continuous operation without erroneous protection activation.
Data Source
AI summary
A power supply apparatus with soft-start function is suitable to a load including a voltage stabilizing unit and a load unit coupled in parallel. The power supply apparatus includes a power unit, a soft-start adjusting unit, a current detecting unit and a controlling unit. The power unit generates a power voltage. The soft-start adjusting unit receives the power voltage, a first controlling signal and a second controlling signal, and transforms the power voltage to a soft-start current accordingly to output the soft-start current to the voltage stabilizing unit or output the power voltage to the voltage stabilizing unit. The current detecting unit measures a current of a loop formed between the power unit and the voltage stabilizing unit to generate a current detecting signal. The controlling unit receives the current detecting signal to generate the first controlling signal and second controlling signal.