Power Converter Dead-Time Shuffling for Waveform Distortion
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Solution Overview
Problem
Existing power converter systems for electric vehicles face challenges in preventing shoot-through without introducing significant distortion in the output waveform, particularly due to the insertion of dead-time in switching devices, which increases cost and complexity.
Innovation Solution
The solution involves a power converter with a phase leg comprising upper and lower switching devices, where a gate driver shuffles among alternate paired sets of dead-time inserted signals to minimize distortion, using a multiplexer to select gate drive signals based on current flowing in the load, thereby dispersing distortion and reducing the need for complex compensation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead-time is inserted to prevent shoot-through, then switching device safety is improved, but output waveform distortion increases
Solution Approach 1:
The patent applies dynamics by making the dead-time variable rather than fixed. The controller dynamically adjusts the dead-time duration based on real-time detection of current direction in the load. When current flows in one direction, a first dead-time value is applied; when current reverses, a second dead-time value is applied. This dynamic adaptation resolves the contradiction by optimizing both shoot-through prevention and waveform quality according to operating conditions.
Solution Approach 2:
The patent changes the parameter of dead-time duration based on current direction. By detecting whether current flows in the positive or negative direction through the load, the system selects appropriate dead-time values from a set of predetermined values. This parameter change strategy allows the system to maintain reliable shoot-through protection while minimizing waveform distortion for each specific operating condition.
2Reliability
If dead-time is inserted to prevent shoot-through, then switching device safety is improved, but control delays increase
Solution Approach 1:
The system dynamically adjusts dead-time duration based on current direction, applying shorter dead-time values when conditions allow and longer values only when necessary for safety. This dynamic approach reduces unnecessary time delays in the control loop while maintaining adequate protection against shoot-through, thereby resolving the contradiction between reliability and time loss.
3Manufacturing precision
If compensation circuits are added to reduce distortion, then output waveform quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the distortion compensation function from separate hardware compensation circuits and implements it within the existing control system through intelligent dead-time management. By detecting current direction and selectively applying appropriate dead-time values, the system achieves waveform quality improvement without adding complex external compensation hardware, thus resolving the contradiction between quality and complexity.
Solution Approach 2:
The control system performs self-service by detecting current direction and automatically selecting appropriate dead-time values without requiring external compensation circuits. The system uses its own control logic to compensate for waveform distortion, eliminating the need for additional complexity while maintaining output quality.
Data Source
AI summary
A power converter receives a DC supply voltage across a phase leg. The phase leg comprises an upper switching device and a lower switching device coupled across the DC link, wherein a junction between the upper and lower switching devices is configured to be coupled to a load. A gate driver is coupled to the phase leg activating the respective upper switching device according to an upper gate signal and activating the respective lower switching device according to a lower gate signal in response to a pulse-width modulation (PWM) control signal at a PWM frequency. The gate driver shuffles among a plurality of alternate paired sets of dead-time inserted signals. Each paired set of dead-time inserted signals corresponds to a different distortion of a current flowing in the load, so that overall distortion is dispersed.