Dynamic Voltage-Reference Level Shifter for GaN Dead Time
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Solution Overview
Problem
The use of GaN devices in switching power supply devices results in a significant drop of the switching voltage during dead time, leading to erroneous operations in the level shifter due to the absence of a body diode, which causes the level shifter to incorrectly interpret a 0 V control signal as a HIGH level.
Innovation Solution
A level shifter configuration with multiple signal generators and internal voltage management, utilizing different internal voltages based on the relative values of the constant voltage, bootstrap voltage, ground voltage, and switching voltage to correctly determine signal levels, thereby preventing erroneous operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If GaN devices are used as switching elements to achieve high step-down ratio at high frequencies, then power density is improved, but the switching voltage drops significantly during dead time causing erroneous operations in the level shifter
Solution Approach 1:
The level shifter dynamically selects different internal voltage references based on the instantaneous switching voltage level. The circuit monitors the switching voltage and automatically switches between using the constant voltage (VREG) and the switching voltage itself as the reference, allowing accurate signal interpretation across the full range of switching voltage conditions including the significant drop during dead time
Solution Approach 2:
The invention changes the reference voltage parameter used by the level shifter based on operating conditions. By switching between two different voltage references (VREG and switching voltage), the circuit adapts to the changing electrical conditions caused by GaN device operation, particularly the rapid voltage drop during dead time, ensuring reliable signal level detection throughout the switching cycle
2Stability of the object's composition
If the level shifter uses a constant voltage as reference, then signal interpretation is stable under normal conditions, but it fails to correctly interpret signals when switching voltage drops significantly during dead time
Solution Approach 1:
The level shifter transitions from a static reference voltage approach to a dynamic one, where the reference voltage automatically adapts to the switching voltage level. This dynamic adaptation allows the circuit to maintain stable signal interpretation across varying voltage conditions, particularly during the transient dead time period when switching voltage drops significantly
Solution Approach 2:
The level shifter is designed to function correctly under multiple voltage conditions by implementing a dual reference voltage system. It can use either the constant voltage or the switching voltage as reference depending on which condition applies, making the circuit universally reliable across all operating states including normal operation and dead time
Data Source
AI summary
A level shifter includes first to third signal generators, wherein the first and second signal generators use, as an upper-side power supply voltage, a first internal voltage based on a first voltage when the first voltage is higher than a second voltage, and a second internal voltage based on the second voltage when the second voltage is higher than the first voltage, wherein the third signal generator uses the second voltage as an upper-side power supply voltage, wherein the first signal generator uses, as a lower-side power supply voltage, a third internal voltage based on a third voltage when the third voltage is higher than a fourth voltage, and a fourth internal voltage based on the fourth voltage when the fourth voltage is higher than the third voltage, and wherein the third voltage is lower than the first voltage and the fourth voltage is lower than the second voltage.