DC-DC Converter with Multi-Mode Full-Bridge Control
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Solution Overview
Problem
Existing dual active bridge (DAB) DC-DC converters face inefficiencies due to limited zero voltage switching (ZVS) range and increased reactive current when the input/output voltage ratio is large, leading to increased size and cost, especially under light loads and transient changes.
Innovation Solution
A DC-DC converter design with a first and second full-bridge circuit, a transformer, and a controller that operates in full-bridge, half-bridge, and five-level operation modes to widen the ZVS range, reduce reactive current, and balance output voltages, using series-connected switching elements and floating capacitors to manage voltage levels and phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional DAB converter uses a full-bridge circuit with standard switching control, then power transmission can be performed, but the ZVS range is limited and reactive current increases when the input/output voltage ratio is large
Solution Approach 1:
The patent implements dynamic switching control that adapts the full-bridge circuit operation mode based on real-time detection of input/output voltage ratios and load conditions. The controller dynamically adjusts switching patterns to maintain ZVS across varying operating conditions, transforming the static switching control into a dynamic system that responds to changing voltage and load parameters.
Solution Approach 2:
The patent changes the operational parameters of the full-bridge circuit by introducing multiple operation modes (full-bridge mode, half-bridge mode, and five-level operation mode) with different voltage output levels. By switching between these modes based on detected voltage ratios, the system optimizes the voltage transformation ratio and current characteristics to reduce reactive current while expanding ZVS range.
2Ease of operation
If the input/output voltage ratio is large and a light load is connected, then the converter can operate, but reactive current that does not contribute to transmission power is increased leading to efficiency deterioration
Solution Approach 1:
The patent applies partial action by implementing half-bridge operation mode and five-level operation mode in addition to full-bridge mode. These partial operation modes output voltages of half the full-bridge voltage or intermediate levels, allowing the system to operate efficiently under light load conditions with large voltage ratios by using only the necessary portion of the full voltage output, thereby reducing unnecessary reactive current.
Solution Approach 2:
The controller dynamically selects between full-bridge mode, half-bridge mode, and five-level operation mode based on real-time detection of load conditions and voltage ratios. Under light load conditions with large voltage ratios, the system dynamically switches to half-bridge or five-level modes to reduce reactive current, while under heavier loads it transitions to full-bridge mode for maximum power transmission.
3Reliability
If large magnetic cores are used to prevent magnetic saturation during transient changes, then DC offset can be prevented, but the device size and cost increase
Solution Approach 1:
The patent implements a feedback mechanism where the controller detects transient changes in operation state (such as abrupt transmission power changes or operation mode switching) and responds by adjusting switching patterns to prevent DC offset generation. This active feedback control allows the use of smaller magnetic cores since the system actively prevents saturation conditions rather than relying solely on oversized passive components.
Solution Approach 2:
The controller performs preliminary detection of transient change conditions (such as upcoming operation mode switches or power changes) and preemptively adjusts switching patterns to prevent DC offset before it occurs. This preliminary action allows the magnetic core to operate within safe flux density limits throughout transient events, eliminating the need for excessive core size as a safety margin.
4Device complexity
If the converter operates in conventional full-bridge mode only, then simple control is maintained, but the ZVS range remains limited under varying load conditions
Solution Approach 1:
The patent segments the full-bridge operation into multiple distinct operation modes: full-bridge mode for high power transmission, half-bridge mode for medium power, and five-level operation mode for fine-grained control under varying conditions. Each mode has optimized switching patterns tailored to specific operating ranges, allowing the system to maintain ZVS across the entire operating spectrum while keeping each individual mode's control logic relatively simple.
Solution Approach 2:
The patent creates a universal control system that can operate in multiple modes (full-bridge, half-bridge, five-level) using a single integrated controller that detects operating conditions and automatically selects the appropriate mode. This multi-functional approach allows one controller to handle all operating conditions optimally, expanding ZVS range without proportionally increasing control complexity through dedicated controllers for each mode.
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 efficient operation across a wide input/output voltage ratio and load variation range, reducing reactive current and DC offset, thereby minimizing device size and cost while maintaining high efficiency.
Implementation Method 1
a transformer that includes a primary winding connected to an input/output portion of the first full-bridge circuit and a secondary winding connected to an input/output portion of the second full-bridge circuit and that isolates the first full-bridge circuit and the second full-bridge circuit from each other
Implementation Method 2
switching loss is reduced by performing zero voltage switching (ZVS) by utilizing leakage inductance of the transformer and parasitic capacitance of a semiconductor device
Implementation Method 3
a DAB DC-DC converter, a direct current (DC) component may be superimposed on an inductor current and an excitation current of the transformer
Data Source
AI summary
A DC-DC converter includes a first full-bridge circuit and a second full-bridge circuit isolated by a transformer. The first full-bridge circuit includes switching elements, a first floating capacitor, and a second floating capacitor. The first full-bridge circuit operates in at least one of a full-bridge operation mode and a half-bridge operation mode. In switching of the operation mode, switching phases of the first full-bridge circuit are shifted in two portions in one cycle of a drive frequency, and shift amounts of the phases are determined such that positive and negative output voltages of the first full bridge circuit are balanced before and after the operation mode is switched.