Halfbridge Controller Dynamic Dead Time Adjustment
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Solution Overview
Problem
The existing control methods for half-bridge circuits result in significant power losses due to the necessity of a dead time to prevent short-circuit currents, which accounts for a substantial portion of the overall power loss, especially in field effect transistors used in electrical consumers like motor vehicles.
Innovation Solution
A method that dynamically adjusts the dead time by determining latency times between switching events, allowing for minimized dead times and optimized control of switching devices, even under varying external influences like temperature, thereby reducing power loss and improving electromagnetic compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dead time is inserted between switching events to prevent short-circuit current, then safety is improved, but power loss increases
Solution Approach 1:
The patent implements dynamic dead time adjustment by continuously monitoring the actual switching behavior of the power semiconductor switches and adapting the dead time period accordingly. Instead of using a fixed conservative dead time, the system measures the real switching latencies and adjusts the dead time to be just sufficient to prevent shoot-through, thereby minimizing unnecessary power loss during dead time while maintaining safety.
Solution Approach 2:
The patent employs feedback mechanisms by monitoring the actual switching events of the power semiconductor switches and using this information to adjust the dead time period. The control system measures the real switching behavior and feeds this information back to optimize the dead time setting, ensuring it is neither too long (causing power loss) nor too short (causing safety issues).
2Reliability
If a long dead time is used to ensure safe operation, then reliability is improved, but power dissipation increases
Solution Approach 1:
The system dynamically adjusts the dead time period based on actual switching measurements rather than using a fixed long dead time. By continuously adapting the dead time to match the real switching latencies of the power semiconductor devices, the system maintains safe operation while minimizing the duration of high power dissipation during dead time periods.
Solution Approach 2:
The patent changes the dead time parameter dynamically based on measured switching behavior. Instead of maintaining a constant conservative dead time value, the system adjusts this parameter in real-time to optimize the balance between safety and power dissipation, reducing the dead time duration to the minimum necessary for safe operation.
3Loss of energy
If dead time is minimized to reduce power loss, then energy efficiency is improved, but risk of short-circuit current increases
Solution Approach 1:
The patent uses feedback from actual switching event monitoring to ensure the minimized dead time is still sufficient for safe operation. By continuously measuring the real switching latencies of the power semiconductor switches and adjusting the dead time accordingly, the system maintains adequate protection against shoot-through while minimizing power loss.
Solution Approach 2:
The system performs preliminary measurements of switching latencies and uses this information to pre-adjust the dead time setting before normal operation begins. This preliminary characterization of the power semiconductor devices allows the system to set an optimized dead time that minimizes power loss while ensuring safety from the start.
4Reliability
If fixed dead time is used based on worst-case calculations, then safety margin is improved, but power dissipation increases
Solution Approach 1:
The patent replaces fixed worst-case dead time settings with a feedback-based adaptive system that measures actual switching behavior. By continuously monitoring real switching latencies and adjusting the dead time accordingly, the system maintains adequate safety margins based on actual device performance rather than conservative worst-case assumptions, thereby reducing unnecessary power dissipation.
Solution Approach 2:
The system changes the dead time parameter from a fixed worst-case value to a dynamically adjusted value based on measured switching characteristics. This parameter adaptation allows the dead time to be optimized for actual operating conditions while maintaining sufficient safety margins, reducing the excessive power dissipation caused by overly conservative fixed dead time settings.
Data Source
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AI summary
A half-bridge comprises a first switching device for connecting a connection to a first potential and a second switching device for connecting the connection to a second potential. A method for controlling the half-bridge comprises steps of output of a closing signal for the first switching device while the second switching device is open, and determination of a latency between the beginning of the closing signal and a dip in a voltage applied across the first switching device. Next, the determined latency is taken as a basis for minimising a dead time that is situated between opening of the second switching device and closing of the fist switching device.