DC/DC Charger Dead Time Control for Ripple Absorption
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Solution Overview
Problem
Existing battery chargers for electric vehicles face challenges in reducing size while maintaining efficiency due to power ripple absorption, leading to inefficiencies and distortions in reactor and output currents when dead times are introduced in switch control.
Innovation Solution
A charger design incorporating a rectifier, DC/DC converter, and power ripple absorption circuit with controlled switch operations that eliminate dead times between specific modes, utilizing a control unit to manage power ripple absorption and reduce capacitor and inductor sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead time is provided for all switch timings in the DAB converter, then switching safety is improved, but current distortion increases and efficiency decreases
Solution Approach 1:
The patent applies local quality by differentiating dead time requirements across different switching scenarios. Dead time is provided only when necessary (specific transitions between modes) rather than uniformly for all switch timings. This selective approach maintains switching safety where needed while eliminating unnecessary dead time that causes current distortion and efficiency loss.
Solution Approach 2:
The patent implements dynamic dead time control where the dead time parameter changes based on the operating mode and switching transition type. The control unit dynamically adjusts whether to insert dead time based on the specific mode transition, making the system adaptive rather than static. This resolves the contradiction by optimizing the dead time parameter in real-time according to operational requirements.
2Reliability
If a large-capacity capacitor is used in the DC link section, then power ripple absorption is improved, but device size increases
Solution Approach 1:
The patent extracts the power ripple absorption function from the traditional large-capacity DC link capacitor by introducing a separate active buffer circuit. This buffer circuit, consisting of smaller capacitors and active switches, takes over the ripple absorption task, allowing the main DC link capacitor to be reduced in size while maintaining effective ripple filtering capability.
Solution Approach 2:
The patent changes the approach to power ripple absorption from passive large-capacity capacitance to active control with smaller capacitance. By using active switches and control algorithms, the system achieves equivalent or superior ripple absorption performance with significantly reduced capacitor size, thereby reducing overall device volume.
3Reliability
If dead time is provided in switch switching, then switching reliability is improved, but reactor current distortion and output current distortion increase
Solution Approach 1:
The patent applies local quality by providing dead time only at specific switching transitions where it is genuinely needed for safety, rather than uniformly across all transitions. This selective dead time insertion maintains switching reliability for critical transitions while preserving current waveform accuracy for transitions where dead time would cause unnecessary distortion.
Solution Approach 2:
The patent uses dynamic control to adjust dead time application based on the specific mode transition. The control unit determines in real-time whether dead time should be inserted, making the switching behavior adaptive. This dynamic approach ensures reliability when needed while minimizing current waveform distortion by eliminating unnecessary dead time periods.
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 charger achieves a compact and highly efficient power absorption by minimizing capacitor and inductor sizes, eliminating current distortions, and maintaining efficient power transmission.
Implementation Method 1
a circuit configuration including a diode rectifier with a power factor correction (PFC) circuit
Implementation Method 2
a large-capacity capacitor in the DC link section is required to have a capacity sufficient to absorb power ripple
Implementation Method 3
a power ripple absorption circuit including a first diode, a second diode, a third diode, an inductor, a capacitor
Data Source
AI summary
The control of the switches S21 to S28 of the DC/DC converter 120 includes a first mode in which all of the switches S21 to S28 of the DC/DC converter 120 are OFF and a plurality of second modes in which at least one of the switches S21 to S28 of the DC/DC converter 120 is ON, and when switching from the first mode to one of the plurality of second modes, a dead time Td is not provided between the first mode and the one of the plurality of second modes.