Current Mode Synchronous Rectification DC/DC Converter Startup Stability
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Solution Overview
Problem
Conventional current mode synchronous rectification DC/DC converters experience fluctuations in output voltage during startup, leading to unstable output until the reference voltage reaches a stable action area.
Innovation Solution
Incorporating a soft start function unit and an output stabilization function unit, which includes a reference voltage generation unit that slowly increases the reference voltage during startup and an oscillator that generates a clock signal and slope voltage corresponding to the reference voltage, along with a mask circuit that masks the error voltage when the reference voltage reaches a specific threshold, to prevent excessive power and reduce drive frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional soft start function is used to prevent rush current, then rush current is suppressed, but output voltage fluctuations occur during startup
Solution Approach 1:
The patent applies preliminary action by enabling the soft start function before normal operation to gradually increase the reference voltage and output voltage. This prevents rush current from the beginning while the output stabilization function subsequently takes over to eliminate voltage fluctuations once the reference voltage reaches a stable level.
Solution Approach 2:
The patent implements dynamics by dynamically switching between two operational modes: soft start mode for initial voltage buildup and output stabilization mode for maintaining steady voltage. The transition between these modes is controlled by monitoring the reference voltage level, allowing the system to adapt its behavior based on the startup stage.
2Object-generated harmful factors
If the reference voltage is slowly increased during startup, then rush current is prevented, but output voltage fluctuations occur until stability is reached
Solution Approach 1:
The soft start function performs preliminary action by gradually increasing the reference voltage before full power operation begins. This controlled voltage buildup prevents rush current while the subsequent output stabilization function quickly establishes the target voltage to minimize overall startup time.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining the voltage increase process without interruption - the soft start function continuously increases voltage until the reference voltage reaches a stable level, then the output stabilization function continuously maintains the target voltage, ensuring uninterrupted power delivery throughout the startup sequence.
3Stability of the object's composition
If both soft start and output stabilization functions are implemented, then output voltage stability is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining the soft start function and output stabilization function into a unified control system. Both functions share common components including the reference voltage generation unit, PWM comparator, and switching control logic, allowing them to work together seamlessly without requiring completely separate control circuits.
Solution Approach 2:
The system uses dynamics by implementing a mode-switching mechanism that transitions from soft start operation to output stabilization operation based on the reference voltage level. This dynamic approach allows a single control circuit to perform multiple functions at different stages, reducing the need for additional dedicated hardware for each function.
Data Source
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AI summary
A current mode synchronous rectification direct current (DC)/DC converter according to the present invention includes: a soft start function unit (in FIG. 1, a reference voltage generation unit (104) enabling a reference voltage REF to slowly increase while starting), for inhibiting a target value of an output voltage VO to be lower than that at a normal action while starting; and an output stabilization function unit (in FIG. 1, a frequency variable type oscillator (110A) generating a clock signal CLK and a slope voltage SLOPE through an oscillation frequency corresponding to a reference voltage REF), for performing at least one of waiting for start of a switching action and reduction of a drive frequency while starting.