Adaptive Soft Start and Stop for DC-DC Converters
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Solution Overview
Problem
Existing DC-DC converters experience excessive inrush current during startup and lack controlled soft stop procedures, leading to potential circuit damage and voltage instability, with existing soft start techniques limiting the slope of control signals and not addressing the need for controlled voltage gradients during mode switching.
Innovation Solution
An adaptive soft start and soft stop device that includes an adaptive reference generator, TON generator, PWM controller, current RAMP, adaptive output voltage controller, differential sensing block, error amplifier, PWM comparator, and gate driver, which collectively control the duty cycle and frequency of the PWM signal to manage the output voltage gradient during startup and shutdown, preventing inrush currents and ensuring linear discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear charging method is used to increase output voltage during startup, then the output voltage increases gradually without excessive inrush current, but the slope of the control signal is limited and the output voltage cannot quickly reach the target level
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor through a dedicated path before enabling the main power switch. This preliminary charging action ensures that when the main switch turns on, the inrush current is already limited, allowing both safe startup and faster voltage rise.
Solution Approach 2:
The startup process is segmented into distinct phases: a pre-charge phase where the capacitor charges through a limited current path, and a main switching phase where the full power is applied. This segmentation allows the system to combine the benefits of both gradual and fast charging at different stages.
2Speed
If the duty of PWM signal is increased sharply during mode switching, then the output voltage responds quickly, but an instantaneous inrush current occurs causing inductor deterioration and circuit damage
Solution Approach 1:
Before the main power switch is activated, the system performs preliminary action by charging the output capacitor through a controlled current source. This preliminary charging ensures that when the PWM duty is increased, the inrush current is already mitigated, allowing fast response without damaging current spikes.
Solution Approach 2:
The patent introduces an intermediary current source that acts as a mediator between the input voltage and the output capacitor during startup. This intermediary component controls the charging current to prevent inrush while still allowing the output voltage to rise quickly when needed.
3Reliability
If conventional soft start techniques are used, then inrush current is limited, but no controlled soft stop procedure is provided leading to voltage instability during shutdown
Solution Approach 1:
The patent implements a universal control mechanism that handles both startup and shutdown operations through the same controlled current source. This multi-functional approach ensures consistent voltage control during both power-on and power-off, providing stability throughout the entire operational cycle.
Solution Approach 2:
The system employs feedback control during shutdown by monitoring the output voltage and adjusting the current source accordingly. This feedback mechanism ensures that the output voltage decreases gradually and controllably, preventing voltage instability during the soft stop procedure.
Data Source
AI summary
The present invention relates to an adaptive soft start and soft stop device for a converter, and more particularly, provides an adaptive soft start and soft stop device for a converter which controls a final output voltage to be increased or decreased with a predetermined gradient by increasing a duty at a predetermined rate or increases a frequency during a start period using an input voltage Vin and an output voltage Vo and decreasing the duty at a predetermined rate or decreases a frequency during a stop period.