Soft Start Control Circuit Slope Switching
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Solution Overview
Problem
Inrush currents at the start of a power circuit cause sudden voltage drops, electromagnetic interference, and potential electrical overstress, damaging components and requiring effective reduction methods.
Innovation Solution
A power circuit incorporating a switching circuit and a soft start control circuit that adjusts the slope of the control signal from a first slope to a second slope, reducing inrush current by using a voltage division circuit, reference voltage generating circuit, and control main circuit to manage the turn-on state of the switching circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the switching circuit is turned on abruptly, then the power circuit can start quickly, but an inrush current is generated causing voltage drops and potential component damage
Solution Approach 1:
The soft start control circuit performs preliminary action by gradually increasing the control signal voltage from zero to the full operating voltage through a controlled ramp-up process. This preliminary voltage application ensures that the switching circuit turns on smoothly without generating inrush current, thereby preventing voltage drops and component damage while still achieving power circuit startup.
Solution Approach 2:
The control signal voltage is made dynamic by continuously adjusting its magnitude during the startup phase. The soft start control circuit dynamically increases the voltage at a controlled rate (first slope) until it reaches a reference voltage level, at which point the slope changes (second slope). This dynamic voltage adjustment allows the switching circuit to transition from off to full power operation without abrupt current surges, resolving the contradiction between fast startup and component protection.
2Reliability
If a soft start control circuit with slope switching is implemented, then inrush current is reduced, but the device complexity increases
Solution Approach 1:
The soft start control circuit acts as an intermediary between the power source and the switching circuit. It mediates the voltage transmission by introducing a controlled ramp-up process with slope switching. The control circuit includes voltage generation means that produces a control signal with a first slope until a reference voltage is reached, then switches to a second slope. This intermediary control mechanism protects the switching circuit from inrush current while adding only moderate complexity through standard control circuit components.
Data Source
AI summary
A power circuit including a switching circuit and a soft start control circuit is provided. A first terminal of the switching circuit is configured to receive an input voltage. A control terminal of the switching circuit receives a control signal. A second terminal of the switching circuit is configured to provide an output voltage. The soft start control circuit generates the control signal according to the output voltage and a first reference voltage to control a turn-on state of the switching circuit. The soft start control circuit switches a slope of the control signal from a first slope to a second slope after the switching circuit is turned on and when a voltage value of the control signal is equal to a second reference voltage, wherein the first slope is less than the second slope to reduce an inrush current at the time when the switching circuit is turned on.