UPS Gate Drive Circuit With Variable Deadtime for IGBT Overcurrent
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Solution Overview
Problem
In power conversion apparatuses, the fixed deadtime can lead to overcurrent issues due to inverse proportionality with interrupting current, resulting in inefficiency when extended to prevent overcurrents.
Innovation Solution
A power conversion apparatus with a control circuit that dynamically adjusts switching element drive signals based on voltage thresholds across switching elements, ensuring the second switching element is turned on only after the first is fully off, preventing overcurrents and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the deadtime is extended to prevent overcurrent, then overcurrent prevention is improved, but the duration of on of the second switching element becomes shorter and efficiency becomes poorer
Solution Approach 1:
The patent applies dynamics by making the deadtime variable rather than fixed. The control device dynamically adjusts the deadtime based on the interrupting current magnitude: when interrupting current exceeds a threshold, the deadtime is extended; otherwise, it uses a shorter duration. This resolves the contradiction by adapting the deadtime to actual operating conditions, preventing overcurrent when necessary while maintaining efficiency when not needed.
Solution Approach 2:
The patent changes the parameter of deadtime from a constant value to a variable value that depends on interrupting current. By monitoring the interrupting current and adjusting the deadtime parameter accordingly, the system achieves both overcurrent prevention and maintained efficiency, resolving the technical contradiction between reliability and energy loss.
2Device complexity
If the deadtime is set to a fixed constant value, then device complexity is reduced, but overcurrent may occur when interrupting current causes off delay time to exceed deadtime
Solution Approach 1:
The patent implements feedback by monitoring the interrupting current and using this information to adjust the deadtime. The control device continuously observes the current state and modifies the deadtime parameter in response, creating a closed-loop control system that prevents overcurrent while maintaining manageable complexity through automated adjustment rather than complex manual calibration.
Data Source
AI summary
A gate drive circuit of an uninterruptible power supply apparatus generates first and second gate drive signals in response to first and second PWM signals, and alternately turns on first and second IGBTs. When the first IGBT is on, the gate drive circuit sets the first gate drive signal to the “L” level in response to the second PWM signal and sets the second gale drive signal to the “H” level in response to a voltage across terminals of the first IGBT exceeding a threshold voltage.