Driving System for Switching Elements with Dynamic Dead Time Control
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Solution Overview
Problem
Existing driving systems for power converters face challenges in reducing variations in dead times between series-connected high- and low-side switching elements over switching cycles without complicating the circuit structure, which affects power conversion efficiency and reliability.
Innovation Solution
A driving system that measures the delay period between switching commands and actual state changes of the switching elements, adjusting the input timing of subsequent switch signals to match the required delay period, thereby reducing variations in dead times between series-connected high- and low-side switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dead time is increased to account for parameter variations and turn-off delay periods, then the reliability is improved by preventing through current, but the power conversion efficiency deteriorates due to longer non-conducting periods
Solution Approach 1:
The dead time is made dynamic by adjusting it based on the actual turn-off delay period measured in real-time. The control unit modifies the dead time duration according to the measured delay, allowing the system to adapt to varying operating conditions (temperature, voltage, current) rather than using a fixed conservative value. This resolves the contradiction by optimizing reliability only when needed while minimizing efficiency losses during normal operation.
Solution Approach 2:
The system implements feedback by measuring the actual turn-off delay period and using this information to adjust the dead time. The control unit continuously monitors the delay between gate voltage application and collector current change, then feeds this information back to optimize the dead time setting. This feedback mechanism allows the system to maintain reliability while reducing unnecessary energy losses from excessive dead time.
2Manufacturing precision
If multiple parameters (collector-emitter voltage, collector current, temperature) are measured and used to adjust dead time, then the manufacturing precision of dead time control is improved, but the device complexity increases due to additional circuit components
Solution Approach 1:
The invention extracts only the essential measurement needed for dead time adjustment - the turn-off delay period - rather than requiring all three parameters (voltage, current, temperature) to be measured and processed. By focusing on the direct observable (delay period) rather than the underlying causes (parameter variations), the system achieves precise dead time control with minimal circuit complexity. The turn-off delay period naturally reflects all parameter variations without needing to measure each one separately.
Solution Approach 2:
The turn-off delay period measurement serves multiple functions: it directly provides the adjustment information needed for dead time control, and it inherently accounts for the effects of temperature, voltage, and current variations. This single measurement acts as a universal indicator that replaces the need for separate sensing circuits for each parameter, simplifying the overall device structure while maintaining precision.
3Reliability
If a fixed dead time with margin is used to cover maximum parameter changes, then the reliability is improved by ensuring sufficient turn-off time, but the productivity deteriorates due to reduced power conversion efficiency
Solution Approach 1:
The system transitions from a static fixed dead time to a dynamic adjustable dead time. Instead of always using the maximum margin-based dead time, the control unit adjusts the dead time duration based on actual measured turn-off delay periods. This dynamic approach ensures reliability when needed (when delay is long) while maximizing productivity when conditions allow (when delay is short), resolving the contradiction between reliability and power conversion efficiency.
Data Source
AI summary
In a driving system, an applying module applies, in response to an input of an on or off command as a switching command, a switch signal to a target switching element as a high- or low-side switching element to switch the target switching element to be an on or off state. A measuring module measures a delay period defined as a time interval from a first time to a second time. The first time represents a time at which the switching command is switched from one of the on command and the off command to the other. The second time represents a time at which the target switching element is actually switched to be the on or off state. An adjusting module adjusts, based on the delay period, an input timing of a next switch signal applied from the applying module to the target switching element.