Cascode Normally-Off Switch With Self-Biased Startup Power

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Solution Overview

Problem

Traditional switched power converters face inefficiencies and high power dissipation due to the use of active components like BJT transistors for startup, especially in high-voltage applications, leading to increased energy draw when idle.

Innovation Solution

Integration of a low-voltage enhancement-mode transistor and a high-voltage depletion-mode III-N transistor in a cascode configuration, along with a monolithic IC controller and gate driver, to form a single electronic component package that reduces component count and eliminates the need for auxiliary windings and active components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a BJT transistor is used for startup in high-voltage applications, then the power converter can be started up, but significant power is dissipated particularly when idle

Engineering Contradiction:

Improvestartup capabilityVSAvoidpower dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the operating parameters of the startup transistor from BJT to depletion-mode MOSFET, which has different electrical characteristics including higher input impedance and lower off-state current, thereby reducing power dissipation while maintaining startup functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and eliminates the need for auxiliary windings and multiple discrete startup components by integrating the startup function directly into the main power switch using the depletion-mode MOSFET's inherent characteristics

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If auxiliary windings and multiple components are used for startup, then the IC controller can be powered, but the device complexity increases

Engineering Contradiction:

ImproveIC controller startup powerVSAvoidcomponent count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the startup function with the main power switch by using the depletion-mode MOSFET's body diode and inherent characteristics to provide startup current, eliminating the need for separate auxiliary windings and startup components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The depletion-mode MOSFET serves multiple functions: it acts as the main power switch during normal operation and simultaneously provides the startup function during power-on, eliminating the need for dedicated startup components

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250253762A1Cascode normally off switch with driver and self bias

Publication Date: 2025.08.07 TRANSPHORM TECHNOLOGY INC

AI summary

An electronic component comprises a semiconductor devices package. The semiconductor device package includes a conductive structural package base, a first terminal configured to be connected to an inductive load, and a second terminal configured to be connected to a common node or circuit ground. The package further comprises an enhancement-mode transistor and a depletion-mode III-N transistor in a cascode configuration. The enhancement-mode transistor is monolithically integrated with an IC controller and a gate driver on a common silicon substrate, where an anode of a rectifying diode is connected to the drain of the enhancement-mode transistor and a cathode of the rectifying diode is connected to a voltage input terminal of the IC controller, and a reservoir capacitor has a first terminal connected to the cathode of the rectifying diode and a second terminal connected to the conductive structural package base.