PWM Electric Motor Dead Time Control Using Switching Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In pulse-width-modulated electric motors, the dead time between switching off one switch and switching on the other leads to increased electrical losses and acoustic issues due to current flowing through freewheeling diodes, which is inefficient and varies with hardware delays and temperature fluctuations.
Innovation Solution
A method that dynamically adjusts the software dead time based on measured switching times to optimize and minimize the total dead time, compensating for hardware variations and ensuring efficient motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed software dead time is used to prevent short circuits, then reliability is improved, but electrical losses increase and efficiency deteriorates
Solution Approach 1:
The patent implements dynamic dead time adjustment by continuously monitoring the actual switching behavior of the semiconductor switches and adapting the software dead time accordingly. Instead of using a fixed conservative dead time value, the system measures the real switching times and adjusts the dead time dynamically to match actual hardware characteristics, thereby reducing unnecessary energy losses while maintaining reliable short circuit prevention.
Solution Approach 2:
The patent employs feedback mechanisms by measuring the actual switching times of the semiconductor switches and using this information to adjust the software dead time. The control unit continuously monitors the switching behavior and modifies the dead time setting based on the measured data, creating a closed-loop system that optimizes the balance between reliability and energy efficiency.
2Reliability
If a longer dead time is provided to account for hardware variations, then reliability is improved, but productivity deteriorates
Solution Approach 1:
The system dynamically adjusts the dead time based on actual switching measurements rather than using a static conservative value. This allows the motor control system to maintain accurate switching control adapted to real hardware characteristics while minimizing the dead time duration, thereby improving overall operational efficiency and productivity.
Solution Approach 2:
The patent changes the dead time parameter dynamically based on measured switching behavior. By adjusting this critical timing parameter according to actual hardware performance rather than relying on fixed conservative estimates, the system achieves both reliable control and improved productivity through reduced time losses.
3Reliability
If hardware dead time variations are compensated with a larger software dead time margin, then reliability is improved, but the dead time increases and efficiency worsens
Solution Approach 1:
The patent uses feedback from actual switching time measurements to determine the appropriate software dead time value. Instead of adding a large fixed margin to compensate for hardware variations, the system measures real switching behavior and sets the dead time precisely according to measured data, thereby maintaining reliable timing control while minimizing time losses.
Solution Approach 2:
The system performs self-characterization by measuring its own switching behavior and using this self-acquired information to optimize the dead time setting. This self-service approach eliminates the need for conservative over-compensation, allowing the system to achieve reliable timing control with minimal dead time based on its actual performance characteristics.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a method for operating a pulse-width modulated electric motor (4), in which, during the pulse width modulation, at least one bridge branch (26) is controlled by a high-side switch (44) and a low-side switch (46), and in which, between a switch-off operation of one switch (44, 46) and a switch-on operation of the other switch (46, 44), a dead time is provided which is composed of a hardware dead time duration (TLSoff, THSon, THSoff, TLSon) which changes during motor operation and an adjustable software dead time duration (TSWon, TSWoff), wherein the switching times (T2, T4, T6, T8) for the switching operations limiting the dead time are detected, wherein the software dead time (TSWon, TSWoff) is changed as a function of the detected switching times (T2, T4, T6, T8).