Half-Bridge Converter Balancing via Timing-Based Current Injection
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Solution Overview
Problem
Half bridge LLC resonant converters face challenges in maintaining volt-second balance during burst mode operations, leading to flux walking and current sharing issues due to inaccuracies in measuring the resonant capacitor voltage, which can cause performance degradation and potential damage.
Innovation Solution
The implementation of VCR synthesis circuitry with integrated equalizer circuitry that corrects errors in resonant capacitor voltage measurements by injecting or removing current and adjusting pulse widths, using monitor circuitry and DAC circuitry to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If half bridge converter operates in burst mode, then power conversion capability is improved, but volt-second balance is disrupted causing flux walking
Solution Approach 1:
The patent implements a feedback mechanism where the control circuitry monitors the resonant capacitor voltage and adjusts the switching signals to maintain volt-second balance. The system continuously compares the actual voltage with the expected voltage and corrects any deviations by modifying the transistor switching durations, thereby preventing flux walking while operating in burst mode.
Solution Approach 2:
The control circuitry automatically detects and corrects volt-second balance errors without external intervention. The system uses its own monitoring capabilities to identify imbalances and self-correct by adjusting switching parameters, enabling stable burst mode operation without requiring external control systems.
2Device complexity
If resonant capacitor voltage is measured directly, then measurement simplicity is maintained, but measurement accuracy deteriorates due to noise and errors
Solution Approach 1:
The patent introduces an intermediary measurement approach where instead of directly measuring the resonant capacitor voltage, the system measures the switching times of the transistors and uses these measurements to infer the voltage. This indirect measurement method, combined with equalizer circuitry, provides more accurate results by avoiding direct exposure to noise while maintaining measurement feasibility.
Solution Approach 2:
The patent replaces direct electrical voltage measurement with a timing-based measurement system. Instead of using voltage probes that are susceptible to noise, the system uses time measurements of transistor switching events, which are more robust to electrical interference. This substitution of measurement methodology significantly improves accuracy while keeping the system relatively simple.
3Stability of the object's composition
If transistor switching times are monitored and equalized, then volt-second balance is restored, but circuit complexity increases
Solution Approach 1:
The control circuitry performs multiple functions: it generates switching signals, monitors resonant capacitor voltage, measures transistor switching times, and adjusts switching parameters to maintain volt-second balance. By consolidating these functions into a single multi-functional control unit, the patent minimizes the increase in overall circuit complexity while achieving the desired balance correction.
Solution Approach 2:
The patent combines the monitoring and control functions into an integrated equalizer circuitry that works closely with the existing control circuitry. Rather than adding separate independent systems, the patent merges the volt-second balance correction functionality with the existing switching control, thereby reducing the net increase in circuit complexity while effectively restoring volt-second balance.
Data Source
AI summary
An example apparatus includes: monitor circuitry configured to: determine a first transistor within half bridge converter circuitry is powered on for a first amount of time during a switching cycle of the half bridge converter circuitry; determine a second transistor within the half bridge converter circuitry is powered on for a second amount of time during the switching cycle; and digital to analog converter (DAC) circuitry coupled to the monitor circuitry, the DAC circuitry configured to inject an amount of current into the half bridge converter circuitry to correct an error, the amount of the current based on a difference between the first amount of time and the second amount of time.