GaN HEMT Half-Bridge Deadtime Shaping for Reverse Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
GaN HEMT half-bridge circuits experience significant power losses due to reverse voltage during the deadtime in half-bridge circuits, which limits their efficiency compared to conventional silicon devices.
Innovation Solution
A method and system are introduced to modify the deadtime portion of the driver signal in GaN HEMT half-bridge circuits by adjusting the driver signal to transition from a low voltage to an intermediate voltage during a portion of the deadtime, thereby reducing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If GaN HEMT devices are used for high-power density applications, then switching speed and electron mobility are improved, but reverse voltage losses during deadtime increase
Solution Approach 1:
The driver signal is dynamically adjusted during the deadtime period by transitioning from a low voltage level to an intermediate voltage level, rather than maintaining a static low level. This dynamic adjustment reduces the reverse voltage across the HEMT device during deadtime, thereby reducing power losses while maintaining the high switching speed capability of GaN HEMT devices
Solution Approach 2:
The gate voltage parameter is changed during the deadtime period by introducing an intermediate voltage level between the typical low (0V) and high (e.g., 10V) operating levels. This parameter change optimizes the device state to minimize reverse conduction losses while maintaining efficient switching operation
2Reliability
If deadtime is extended to prevent shoot-through, then device safety is improved, but power losses due to reverse voltage increase
Solution Approach 1:
The driver signal transitions dynamically from a low voltage level to an intermediate voltage level during the deadtime period. This dynamic adjustment maintains adequate device protection while minimizing the duration and magnitude of reverse voltage, thereby reducing power losses without compromising device safety
Solution Approach 2:
The deadtime period, which traditionally represents a harmful loss period, is converted into a beneficial transition period by applying an intermediate voltage level. This transforms the deadtime from a purely lossy interval into an opportunity to actively manage device state and minimize losses while maintaining protection
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A half bridge circuit includes two GaN high electron mobility transistors (HEMT). A driver circuit generates a high side and low side driver signals corresponding to square wave. A driver deadtime is the period between during which both driver signals are low. A half bridge adjustment circuit is coupled between the driver and the half bridge circuit and generates a modified high side driver signal and a modified low side driver signal, each including a transition from a low voltage to an intermediate voltage during the corresponding deadtime and a transition from the intermediate voltage to a high voltage at an end of the corresponding deadtime. The half bridge adjustment circuit drives the gate terminals of the high side and low side transistors with the modified high side and low side driver signals.