GaN Depletion HEMT DC-DC Converter for Envelope Tracking
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Solution Overview
Problem
Existing dc/dc converters face limitations in achieving high-frequency and high-power efficiency for envelope tracking techniques in RF and microwave amplification applications, due to restricted bandwidth and efficiency issues with silicon-based MOSFET transistors and bootstrap-type gate driving devices.
Innovation Solution
A multi-power supply voltage dc/dc converter block utilizing depletion HEMT transistors with a driving circuit, powered by multiple non-zero and positive voltages, allowing for high-frequency and high-power operation, and featuring a gate driving circuit with depletion HEMT transistors to optimize switching speeds and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicon-based MOSFET transistors with bootstrap-type gate driving devices are used in dc/dc converters, then the device complexity is reduced and ease of manufacture is improved, but the bandwidth and efficiency are restricted for high-frequency and high-power operation
Solution Approach 1:
The patent changes the material parameter of the transistor from silicon-based MOSFET to gallium nitride-based HEMT, which fundamentally alters the electrical characteristics including electron mobility and saturation velocity. This material parameter change enables the converter to achieve higher bandwidth and efficiency while maintaining ease of manufacture through standard GaN fabrication processes
Solution Approach 2:
The patent employs a composite structure combining depletion HEMT transistors with specific gate driving circuitry designed for GaN devices. This composite approach leverages the high electron mobility of GaN material while integrating specialized driving circuits to fully exploit the material's capabilities, achieving both high bandwidth and manufacturability
2Ease of manufacture
If silicon-based MOSFET transistors with bootstrap-type gate driving devices are used in dc/dc converters, then the device complexity is reduced and ease of manufacture is improved, but the efficiency for high-power operation is restricted
Solution Approach 1:
The patent changes the material parameter of the transistor from silicon-based MOSFET to gallium nitride-based HEMT, which fundamentally alters the electrical characteristics including electron mobility and saturation velocity. This material parameter change enables the converter to achieve higher bandwidth and efficiency while maintaining ease of manufacture through standard GaN fabrication processes
Solution Approach 2:
The patent converts the typically harmful switching losses into beneficial effects by utilizing the ultra-fast switching capability of GaN HEMTs. The high electron mobility allows for extremely rapid switching transitions, minimizing on-resistance and reducing switching losses, thereby converting what is normally a source of inefficiency into a performance advantage
3Device complexity
If conventional dc/dc converter architectures are used, then the device complexity is maintained at acceptable levels, but the efficiency and bandwidth are limited for envelope tracking applications
Solution Approach 1:
The patent changes the material parameter of the transistor from silicon-based MOSFET to gallium nitride-based HEMT, which fundamentally alters the electrical characteristics including electron mobility and saturation velocity. This material parameter change enables the converter to achieve higher bandwidth and efficiency while maintaining ease of manufacture through standard GaN fabrication processes
Solution Approach 2:
The patent implements a dynamic multi-power supply voltage architecture where the converter can operate with different input voltage combinations (e.g., 48V+12V, 48V+5V, or single 48V) depending on the operating conditions. This dynamic adaptability allows the system to optimize efficiency across different power levels and bandwidth requirements without significantly increasing device complexity
4Productivity
If multi-power supply input buck converters are used, then the output residual ripple is reduced and bandwidth is increased, but the switching losses in power transistors increase
Solution Approach 1:
The patent changes the material parameter of the transistor from silicon-based MOSFET to gallium nitride-based HEMT, which fundamentally alters the electrical characteristics including electron mobility and saturation velocity. This material parameter change enables the converter to achieve higher bandwidth and efficiency while maintaining ease of manufacture through standard GaN fabrication processes
Solution Approach 2:
The patent applies different quality characteristics to different parts of the circuit by using GaN HEMTs specifically for the power switching elements where high-frequency operation is critical, while other parts of the circuit can use conventional components. This localized optimization reduces switching losses in the critical path without requiring complete redesign of the entire system
Data Source
AI summary
A DC-to-DC converter block with multiple supply voltages includes a power circuit, the power circuit including N depletion-mode HEMT transistors (T3_1, T3_2, T3_N), N being a natural number greater than or equal to 3. The DC-to-DC converter block also includes a gate drive circuit for the N depletion-mode HEMT transistors (T3_1, T3_2, T3_N) of the power circuit, the drive circuit including depletion-mode HEMT transistors (T1_1, T2_1, T1_2, T2_2, T1_N, T2_N) configured to drive the gates of the N depletion-mode HEMT transistors (T3_1, T3_2, T3_N) of the power circuit, and the power circuit being powered by N positive and non-zero supply voltages, namely a lower supply voltage (VDD_1), an upper supply voltage (VDD_N), and (N−2) intermediate supply voltages (VDD_2) distributed between the lower (VDD_1) and upper (VDD_N) supply voltages.