Adaptive Dead-Time Control for GaN Buck Converter Start-Up
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Solution Overview
Problem
Switched-Mode Power Supplies (SMPS) using GaN transistors experience ringing during start-up, which can damage components and reduce reliability, and existing methods to prevent ringing either fail to detect it effectively or reduce efficiency by increasing dead time.
Innovation Solution
A dynamic start-up procedure that adjusts dead time based on input voltage, output voltage, and output current, using pre-calculated functions to ensure full charge and discharge of parasitic capacitances, thereby reducing ringing while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is increased to prevent ringing during start-up, then reliability is improved, but efficiency deteriorates due to reduced pulse-high time
Solution Approach 1:
The patent applies dynamics by transitioning from fixed dead time to dynamic dead time adjustment. The dead time is varied based on operating conditions (input voltage, output voltage, output current) using pre-calculated functions stored in lookup tables. During start-up when ringing is problematic, longer dead time is applied; during normal operation, shorter dead time is used to maximize efficiency. This dynamic adaptation resolves the contradiction between reliability and efficiency.
Solution Approach 2:
The patent changes the parameter of dead time from a constant value to a variable parameter that adapts to operating conditions. By using pre-calculated functions that map operating parameters (Vin, Vout, Iout) to optimal dead time values, the system automatically adjusts dead time to prevent ringing when needed while minimizing its impact on efficiency during normal operation.
2Object-affected harmful factors
If dead time is increased to ensure full charge and discharge of parasitic capacitances, then ringing is reduced, but productivity deteriorates due to longer switching periods
Solution Approach 1:
The system dynamically adjusts dead time based on real-time operating conditions. During start-up when parasitic capacitance charging/discharging causes ringing, the system applies longer dead time from pre-calculated functions. Once the system reaches steady state, the dead time is reduced to minimize impact on switching frequency and productivity, thus resolving the contradiction between ringing suppression and productivity.
Solution Approach 2:
The patent uses pre-calculated functions and lookup tables that contain optimal dead time values determined in advance for various operating conditions. This preliminary calculation allows the system to quickly select appropriate dead time values without real-time computation delays, effectively suppressing ringing while minimizing impact on productivity during normal operation.
3Device complexity
If fixed dead time is used for all operating conditions, then device complexity is reduced, but adaptability deteriorates as it cannot optimize for different start-up and operating phases
Solution Approach 1:
The system implements adaptability through dynamic dead time adjustment while maintaining relatively simple device architecture. The core complexity is shifted to pre-calculated lookup tables rather than real-time control algorithms. The controller simply queries the lookup table based on current operating parameters and applies the retrieved dead time value, achieving high adaptability without significant increase in device complexity.
Solution Approach 2:
The patent uses pre-calculated functions and lookup tables that store optimal dead time values for various operating conditions. Instead of implementing complex real-time optimization algorithms, the system copies pre-determined optimal values into the control logic, achieving adaptability through data storage and retrieval rather than computational complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The procedure effectively reduces ringing during SMPS start-up, enhancing reliability and maintaining efficiency by dynamically adjusting dead time according to changing circuit conditions.
Implementation Method 1
the parasitic capacitances in the transistors 302, 304 charge and discharge during this dead time
Data Source
AI summary
A start-up routine for a Switched-Mode Power Supply (SMPS) gradually increases the duty cycle while reducing an initial dead time to a final optimal dead time for normal operation. Reliability is improved by the larger initial dead time that reduces ringing in switching transistors during low-voltage conditions early in the start-up sequence. Efficiency is improved by reducing the optimal dead time as voltages approach operating levels. The initial dead time is pre-calculated as a function of the input voltage and initial duty cycle. Optimal dead times are pre-calculated as a function of output voltage and output current. The optimal dead time is adjusted for each iteration of a second loop that also increases duty cycle until the target operating output voltage is reached. Pre-calculated dead times are based on the time required to fully charge and discharge parasitic drain-to-source capacitances in the switching transistors in the SMPS circuit.