Half-Bridge Threshold Voltage Measurement for Fast GaN Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for measuring threshold voltage in GaN-based power devices are limited by long pulse widths, high costs, and inability to measure switching frequencies below 20 μs, with existing setups being expensive and unable to accurately characterize threshold voltage shifts due to OFF-state stress and switching transient currents.
Innovation Solution
A novel half-bridge circuit with a series-connected common source capacitor is employed, allowing for a pulse width less than 7.6 μs and incorporating a decoupling capacitor to measure threshold voltage instability in Group III-N based devices, including GaN, AlN, and AlGaN devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a conventional curve tracer is used to measure threshold voltage, then measurement can be performed, but the minimum pulse width is limited to 500 μs which is too large for actual switching frequency
Solution Approach 1:
The measurement process is segmented into distinct phases: OFF-state stress application, stress removal, and threshold voltage measurement. This segmentation allows the use of short pulses for measurement while maintaining the ability to characterize threshold voltage shifts that would require longer stress periods, resolving the contradiction between pulse width duration and measurement accuracy
Solution Approach 2:
The OFF-state stress is applied preliminarily before the actual threshold voltage measurement. This preliminary action prepares the device by inducing threshold voltage shifts through controlled stress, allowing subsequent measurement with short pulses to accurately capture the stress-induced changes without requiring long measurement pulses
2Duration of action of moving object
If an expensive curve tracer with N1265A is used to reduce minimum pulse width to 20 μs, then faster measurement is achieved, but the setup remains unable to measure devices switching less than 20 μs and requires expensive interface for connection and packaging
Solution Approach 1:
The invention extracts and eliminates the expensive interface and packaging components from the measurement setup. By using a simplified circuit configuration that directly connects to the device under test through standard terminals, it achieves sub-20 μs measurement capability without requiring complex external interfaces or specialized packaging
Solution Approach 2:
The measurement circuit uses simple, inexpensive components such as standard capacitors and resistors that can be easily replaced or modified. This approach replaces expensive, specialized measurement equipment with affordable, off-the-shelf components, reducing both cost and complexity while maintaining measurement capability for ultra-fast switching devices
3Duration of action of moving object
If a characterization circuit with half-bridge circuit and current source is used to reduce minimum OFF-state pulse duration, then shorter pulse width is achieved, but the current source and additional diodes make the overall circuit more expensive
Solution Approach 1:
The invention merges the stress application and measurement functions into a single integrated circuit configuration. The half-bridge circuit is combined with carefully selected capacitor values to inherently provide the necessary current sources and voltage references, eliminating the need for separate current source circuits and additional diodes, thus reducing component count and cost while achieving sub-20 μs pulse duration capability
Solution Approach 2:
The circuit components serve multiple functions simultaneously. For example, the decoupling capacitor not only provides decoupling but also acts as a current source during specific measurement phases. The half-bridge circuit provides both voltage switching and current limiting functions. This multi-functionality reduces the total number of components needed, lowering circuit complexity and cost
4Measurement precision
If existing measurement circuits are used to measure threshold voltage shift due to OFF-state stress, then measurement capability is provided, but they cannot measure threshold voltage shifts due to switching transient current
Solution Approach 1:
The measurement circuit is designed to capture dynamic threshold voltage changes during switching transients. By synchronizing the measurement timing with the switching events and using appropriately timed sampling, the circuit can measure both DC stress-induced shifts and dynamic transient-induced shifts, providing comprehensive threshold voltage characterization across different operating conditions
Data Source
AI summary
A power device threshold voltage measurement circuit and its operation method thereof are provided. The measurement circuit includes a switch component, a device under test, a common source capacitor and a decoupling capacitor. The switch component and the device under test forms a half bridge circuit and the common source capacitor is in series connected at the source of the device under test. The device under test is connected as a lower switch of the half bridge circuit and the decoupling capacitor is connected between the device under test and the common source capacitor. By applying an OFF-state stress mode and a measurement mode successively afterwards, a threshold voltage of the device under test is obtained. And the present invention is beneficial to achieving in shorter pulse width, faster measuring speed and inexpensive measuring equipment, and can thus be widely applied to group III-N based power devices.