Multi-level DC-DC Converter Lossless Voltage Balancing
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Solution Overview
Problem
Existing multi-level DC-to-DC converter circuits face challenges in achieving a full range of output voltages across all operational zones due to limitations in inductor size and voltage overstress on switch transistors, particularly when dealing with large voltage differences and low switching frequencies.
Innovation Solution
The implementation of multi-level DC-to-DC converter circuits that alternate between adjacent zones to treat them as a single 'super-zone', using a parallel 'shadow' capacitor voltage balancing circuit to balance capacitor voltages and prevent voltage overstress, and allowing out-of-order state transitions for lossless voltage balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the voltage difference between input and output is large and switching frequency is low, then the converter can handle a wider voltage range, but the inductor size increases
Solution Approach 1:
The patent divides the voltage conversion process into multiple discrete levels using a multi-level converter architecture. Instead of a single large inductor handling the full voltage range, the system uses multiple smaller inductors (L1, L2, L3) and capacitors (C1, C2, C3) to create intermediate voltage steps, effectively segmenting the voltage transformation into manageable portions.
Solution Approach 2:
The patent introduces a temporal dimension to voltage balancing by implementing periodic switching sequences that alternate between different operational zones. The converter dynamically transitions between Zone 1, Zone 2, and Zone 3, using time-based switching to achieve voltage regulation without requiring a single large inductor to handle the entire voltage range simultaneously.
2Adaptability or versatility
If the converter operates at the boundaries of operational zones, then full voltage range is achieved, but voltage overstress occurs on switch transistors
Solution Approach 1:
The patent implements preliminary voltage balancing actions by monitoring capacitor voltages and initiating corrective switching sequences before voltage overstress occurs. The control system detects when capacitors are approaching unbalanced states and proactively transitions between zones to redistribute voltage, preventing the harmful condition of voltage overstress on switch transistors before it happens.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the voltages across capacitors C1, C2, and C3, and using this information to dynamically adjust the switching sequences. The control system responds to voltage imbalances by modifying the timing and duration of operations in different zones, ensuring that switch transistors never experience dangerous voltage overstress while maintaining full output voltage range capability.
3Stability of the object's composition
If traditional voltage balancing methods are used, then capacitor voltages are stabilized, but energy losses occur
Solution Approach 1:
The patent implements self-service voltage balancing where the converter uses its own operational switching sequences to balance capacitor voltages without external intervention or additional balancing circuitry. By strategically alternating between different operational zones and adjusting duty cycles, the system automatically redistributes energy among capacitors C1, C2, and C3, achieving voltage stabilization through the converter's inherent operation rather than separate balancing mechanisms.
Solution Approach 2:
The patent recovers energy that would otherwise be lost by utilizing the natural charging and discharging cycles of capacitors during zone transitions. When capacitors are discharged during certain switching sequences, the energy is not wasted but is instead recovered and redistributed to other capacitors that need charging, creating a closed-loop energy management system that minimizes losses while maintaining voltage balance.
Data Source
AI summary
Multi-level DC-to-DC converter circuits and methods that permit a full range of output voltages, including near and at zone boundaries. Embodiments alternate among adjacent or near-by zones, operating in a first zone for a selected time and then in a second zone for a selected time. Embodiments may include a parallel capacitor voltage balancing circuit that connects a capacitor to a source voltage to charge that capacitor, or couples two or more capacitors together to transfer charge, all under the control of real-time capacitor voltage measurements. Embodiments may include a lossless voltage balancing solution where out-of-order state transitions are allowed, thus increasing or decreasing the voltage across specific capacitors to prevent voltage overstress on the converter main switches. Restrictions may be placed on the overall sequence of state transitions to reduce or avoid transition state toggling, allowing each capacitor an opportunity to have its voltage steered as necessary for balancing.