Variable-Frequency Interleaved DC-DC Converters for Vehicle Power Supply
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Solution Overview
Problem
Existing power supply devices for vehicle on-board networks face issues with regulation stability, efficiency, and electromagnetic interference (EMI) due to fixed-frequency converters, which limit output power and require additional filtering to meet EMI standards.
Innovation Solution
A power supply device utilizing interleaved reversible DC/DC converters operating at variable frequencies, synchronized by a synchronization device that processes switching signals to maintain stability and reduce EMI emissions across a broader RF spectrum without the need for filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed-frequency converters are used, then the device structure is simple, but conducted and radiated emissions are concentrated over a narrow RF spectrum requiring filters to meet EMI standards
Solution Approach 1:
The patent applies variable frequency operation to the interleaved converters, allowing the switching frequency to be dynamically adjusted rather than fixed. This dynamic frequency variation spreads the electromagnetic emissions across a broader spectrum, reducing the concentration of energy at specific frequencies and thereby lowering EMI levels without requiring additional filters.
Solution Approach 2:
The patent changes the operating parameter of converter frequency from a fixed value to a variable range. By modulating the switching frequency of the interleaved converters, the system spreads spectral emissions across multiple frequencies, transforming the concentrated narrowband EMI problem into a distributed wideband emission profile that naturally complies with EMI standards.
2Ease of operation
If fixed-frequency converters are used, then the control is simple, but regulation stability is not maintained for duty cycle greater than 50% limiting output power
Solution Approach 1:
The patent implements variable frequency control that adapts the switching frequency based on the duty cycle operation point. When the duty cycle exceeds 50%, the system dynamically adjusts the frequency to maintain proper interleaving and regulation stability, enabling stable operation across the full duty cycle range from 0% to 100% without compromising control simplicity.
Solution Approach 2:
The patent modifies the operating frequency parameter in response to duty cycle changes. By detecting when the duty cycle exceeds 50% and adjusting the switching frequency accordingly, the system maintains regulation stability and interleaving effectiveness across all operating conditions, removing the previous limitation on maximum output power.
3Productivity
If fixed-frequency interleaved converters are used, then the converters can operate in parallel, but a minimum control duty cycle of 1% is required to maintain output voltage servo-control stability implying poor efficiency
Solution Approach 1:
The patent employs dynamic frequency adjustment that allows the interleaved converters to maintain stable parallel operation down to extremely low duty cycles接近0%. The variable frequency mechanism ensures that the interleaving relationship and servo-control stability are preserved regardless of how small the duty cycle becomes, eliminating the need for a minimum 1% duty cycle and thereby enabling efficient operation at very light loads.
4Object-generated harmful factors
If variable frequency converters are used without synchronization, then the EMI spectrum is broadened, but the converters cannot maintain proper interleaving and regulation stability
Solution Approach 1:
The patent implements a synchronization mechanism that uses feedback from the switching signals of all interleaved converters to maintain a fixed phase relationship. The synchronization device monitors the switching signals and adjusts the frequency of each converter to ensure they remain properly interleaved even while operating at variable frequencies, thereby maintaining both EMI broadening and regulation stability simultaneously.
Solution Approach 2:
The patent introduces a synchronization device as an intermediary between the variable frequency converters. This synchronization mechanism acts as a mediator that coordinates the switching frequencies and phases of multiple converters, ensuring they maintain proper interleaving relationships while independently operating at optimized variable frequencies for reduced EMI.
Data Source
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Figure 3A
AI summary
The invention relates to a power supply unit (3) for supplying power to an on-board electrical network of a vehicle, including: at least two DC-to-DC converters (9A, 9B) which are interleaved and reversible between an operating mode for lowering voltage and an operating mode for raising voltage, the converters (9A, 9B) being intended for being connected to an power storage unit (ST2) and being capable of supplying current to the on-board network; and a switch (K) enabling a power source (ST1) to supply power to the on-board network when the switch (K) is in a first state, and enabling the power storage unit (ST2) to supply power to the on-board network when the switch (K) is in a second state. The unit is characterised in that the converters (9A, 9B) are variable-frequency converters, and in that the power supply unit (3) also includes a synchronisation device (200) configured such as to synchronise the operation of the converters (9A, 9B) operating at variable frequencies and the current generation of the converters.