Circuit Breaker Dead Time Measurement in Motor Output Stages
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Solution Overview
Problem
Existing methods for measuring and optimizing the dead time of power switches in motor output stages of electromechanical steering systems are complex and prone to errors, leading to inefficiencies and potential shoot-through issues.
Innovation Solution
A method involving the measurement of actual turn-on and turn-off times of high-side and low-side FETs, calculation of time intervals, and comparison with target values to determine and adjust dead times, using capture timers and edge detection circuits to monitor switching behavior and optimize dead times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods for measuring and optimizing dead time are used, then dead time can be adjusted, but the measurement process becomes complex and error-prone
Solution Approach 1:
The measurement process is segmented into distinct functional blocks: capture timer unit for time measurement, edge detection unit for signal processing, and control unit for coordination. Each block performs a specific function, making the overall complex measurement task manageable and accurate through modular organization
Solution Approach 2:
The patent introduces intermediate processing units between the raw signals and the final measurement result. The edge detection unit acts as an intermediary that processes raw switching signals before they are timed by the capture timer, and the control unit serves as an intermediary that coordinates between different measurement channels and processes the timed data to calculate dead time
2Loss of energy
If dead time is reduced to improve efficiency, then switching losses decrease, but shoot-through risk increases
Solution Approach 1:
The system continuously measures the actual dead time between complementary switch operations and compares it against target values. The control unit uses this feedback information to detect deviations and can trigger error signals or adjust switching commands to maintain safe dead time margins, preventing shoot-through while optimizing for low losses
Solution Approach 2:
The dead time measurement and adjustment is not a static one-time calibration but a dynamic continuous process. The system adapts to varying operating conditions by continuously monitoring switching times and adjusting the dead time compensation accordingly, allowing optimal energy efficiency while maintaining safety margins under different load and temperature conditions
3Measurement precision
If iterative dead time reduction is performed, then optimal dead time can be found, but system productivity decreases due to repeated testing
Solution Approach 1:
The system performs preliminary measurements of turn-on and turn-off times continuously during normal operation rather than requiring separate iterative testing phases. The capture timer unit continuously captures switching events, and the control unit continuously calculates dead time, so the optimal value is determined as part of normal operation rather than through time-consuming separate calibration iterations
Data Source
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AI summary
The invention relates to a method for measuring the dead time of circuit breakers in a motor output stage, wherein the motor output stage comprises at least one half bridge (14) having a high-side FET (12) and a low-side FET (13), wherein the following method steps are provided: measuring an actual switch-on time and an actual switch-off time of the low-side and high-side FETs; calculating the switch-on time and the switch-off time of the low-side and the high-side FETs; and calculating the dead times (DTF and DTR using the following formula: DTF= (switch-on time of the low-side FET) – (switch-off time of the high-side FET), DTR= (switch-on time of the high-side FET) – (switch-off time of the low-side FET); and comparing the calculated dead times (DTF, DTR) with predefined target values.