DC-DC Converter Voltage Stability via Segmented Control
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Solution Overview
Problem
Existing DC voltage converters for motor vehicles face instability when battery voltage fluctuates, particularly when a filter for electromagnetic compatibility (EMC) is included, making it difficult to maintain a stable output voltage across varying battery conditions.
Innovation Solution
A DC-DC converter design that incorporates a step-up converter and a step-down converter, where the step-up converter controls intermediate voltage without feedback, using a pulse-width-modulated signal to adjust energy delivery based on battery voltage, and includes a diode to prevent overvoltage, allowing for stable operation over wide voltage ranges with reduced circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a step-up converter and step-down converter are connected in series to maintain stable output voltage, then the output voltage stability is improved, but the device complexity increases
Solution Approach 1:
The DC-DC converter is divided into two independent stages: a step-up converter that boosts battery voltage to an intermediate voltage, and a step-down converter that regulates this intermediate voltage to a stable output voltage. This segmentation allows each stage to be optimized independently, improving overall reliability while managing complexity through modular design.
Solution Approach 2:
An intermediate voltage stage is introduced between the battery and the final output. The step-up converter creates this intermediate voltage, which then serves as the input for the step-down converter. This intermediary stage acts as a buffer that isolates the two converters, improving stability while allowing straightforward control of each stage.
2Measurement precision
If feedback control is implemented for the step-up converter to regulate intermediate voltage, then the voltage regulation precision is improved, but the device complexity increases
Solution Approach 1:
The step-up converter is designed to proactively boost the battery voltage to a predetermined intermediate voltage level before the voltage drops to critical levels. This preliminary action ensures that the step-down converter always receives sufficient input voltage, maintaining output stability without requiring complex feedback control in the step-up stage.
Solution Approach 2:
The invention implements feedback control selectively: the step-up converter operates without feedback (open-loop) since it only needs to provide sufficient voltage, while the step-down converter uses feedback to precisely regulate the final output voltage. This selective feedback approach achieves the required precision while minimizing control circuit complexity.
3Reliability
If the step-up converter operates actively to boost voltage, then the output voltage stability is improved, but the power consumption increases
Solution Approach 1:
The step-up converter is designed to dynamically adjust its operation based on battery voltage conditions. It activates only when battery voltage drops below a threshold and disactivates when voltage recovers, optimizing power consumption while maintaining output stability during critical periods.
Solution Approach 2:
The step-up converter operates in periodic cycles, activating when voltage drops and deactivating when voltage recovers. This periodic operation reduces average power consumption compared to continuous operation, while still maintaining output stability during voltage dips through timely intervention.
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 ensures a stable output voltage across varying battery conditions, reduces power consumption, and maintains system stability even with EMC filters, by controlling the step-up converter solely based on input voltage without feedback, thus maintaining a stable DC-DC converter operation.
Implementation Method 1
the control circuit for the switch, which controls the switch with a pulse-width-modulated signal
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a step-up converter for converting the battery voltage (UB) to an intermediate voltage (UZ). Said intermediate voltage (UZ) is greater than or equal to the battery voltage (B). A step-down converter (5) receives the intermediate voltage (UZ) supplied by the step-up converter (4) and controls an output voltage (Ua) which is less than or equal to the intermediate voltage (UZ). The step-up converter (4) controls the intermediate voltage (UZ) in an open loop depending on the battery voltage (UB), at least if the battery voltage (UB) is lower than a first predetermined value, and at least if at the same time the load on the output of the step-up converter (4) exceeds a minimum load.