In-Vehicle Step-Down Power Supply Frequency Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In-vehicle step-down switching power supplies face challenges in regulating electromagnetic noise and maintaining stable output voltage, especially when input voltage decreases, due to limitations in switching frequency control and increased noise interference, which affects communication frequencies and load stability.
Innovation Solution
An in-vehicle step-down switching power supply with a switching frequency control circuit that adjusts switching frequency between specific ranges and skips noise-prone frequency bands, using a rectification unit to manage circulation current and voltage ripple, thereby stabilizing output voltage and reducing electromagnetic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching frequency is controlled in proportion to bootstrap voltage, then gate driving voltage stability is improved, but electromagnetic noise regulation deteriorates
Solution Approach 1:
The patent changes the control parameter from bootstrap voltage proportionality to direct input voltage-based control. The switching frequency control circuit now adjusts Fsw based on detected input voltage levels, allowing the system to maintain stable gate driving voltage while avoiding frequency bands that generate electromagnetic noise interference with communication frequencies.
2Stability of the object's composition
If switching frequency is set high to reduce output voltage ripple, then output stability is improved, but electromagnetic noise in communication bands increases
Solution Approach 1:
The patent applies local quality by making the switching frequency non-uniform across different input voltage conditions. Instead of using a single high frequency that causes noise, the system selectively adjusts frequency in specific ranges: maintaining higher frequencies when input voltage is high (reducing ripple), and lowering frequencies when input voltage decreases (avoiding communication band noise), thus optimizing both stability and noise reduction locally for each operating condition.
Solution Approach 2:
The patent implements dynamic switching frequency adjustment based on real-time input voltage detection. The control circuit continuously monitors input voltage and dynamically changes the switching frequency accordingly, transitioning between different frequency ranges to simultaneously maintain output stability and avoid electromagnetic noise in communication bands under varying operating conditions.
3Adaptability or versatility
If duty ratio increases to handle lower input voltage, then voltage conversion capability is improved, but switching element control becomes difficult
Solution Approach 1:
The patent changes the operating parameters by dynamically adjusting switching frequency alongside duty ratio. When input voltage decreases and duty ratio must increase for voltage conversion, the system simultaneously lowers the switching frequency to ensure adequate on/off transition times for the switching element, making control easier while maintaining voltage conversion capability across a wide input voltage range.
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
The solution enables stable step-down switching operations and effective noise suppression even at decreased input voltages, minimizing output voltage ripple and electromagnetic interference, while reducing the capacity and cost of coils and capacitors.
Implementation Method 1
a rectification unit which executes a rectification operation to generate a circulation current by a path of the output side when the first switch element is non-conductive
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Provided is an in-vehicle step-down switching power supply capable of obtaining a stable output while suppressing nose in a harmful frequency band even when an input voltage decreases. The in-vehicle step-down switching power supply includes a switching frequency control unit and the switching frequency control unit includes a switching frequency range setting unit that changes a switching frequency between fa and fb and a switching frequency path setting unit that skips a frequency band from fd to fe between fa and fb, via an intermediate frequency fc between fa and fb.