Semiconductor Bypass Unit for Body Diode Reverse Recovery

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Solution Overview

Problem

In switching mode power supplies, the body diode reverse recovery issue during the dead time can lead to undesired voltage fluctuations and inefficiencies, particularly due to current flowing through the body diode, which existing solutions like Schottky diodes cannot effectively address without high area costs and inflexible design.

Innovation Solution

A bypass unit with a transistor is introduced between the drain of the second transistor and ground, allowing current to bypass the body diode during dead time, reducing the voltage across the body diode and alleviating reverse recovery issues, with a threshold voltage lower than the body diode, thus minimizing current through the body diode and optimizing area based on breakdown voltage requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a Schottky diode is used to address body diode reverse recovery, then reverse recovery issues are reduced, but area cost increases and design flexibility decreases

Engineering Contradiction:

Improvebody diode reverse recoveryVSAvoidarea cost

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

A bypass unit is introduced as an intermediary component between the body diode and ground. This bypass unit provides an alternative current path during dead time, diverting current away from the body diode and eliminating reverse recovery issues without requiring a Schottky diode replacement

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bypass unit's threshold voltage is specifically designed to be lower than the body diode's threshold voltage. This parameter difference enables the bypass unit to activate first during dead time, controlling current flow and preventing body diode reverse recovery while maintaining area efficiency

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a Schottky diode is used to address body diode reverse recovery, then reverse recovery issues are reduced, but design flexibility is reduced

Engineering Contradiction:

Improvebody diode reverse recoveryVSAvoiddesign flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The bypass unit's threshold voltage can be adjusted to be lower than the body diode's threshold voltage, allowing flexible control of current paths. This parameter adjustment capability enables adaptation to different power supply levels and operating conditions without being constrained by fixed Schottky diode characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The bypass unit dynamically activates during dead time when the transistor switches off, providing adaptive current diversion. This dynamic operation allows the circuit to automatically adjust current paths based on real-time switching conditions, enhancing design flexibility compared to static Schottky diode solutions

Inventive Principle:

Principle #15Dynamics

3Duration of action of moving object

If current flows through the body diode during dead time, then circuit operation continues, but voltage fluctuations and inefficiencies occur

Engineering Contradiction:

Improvecurrent flow continuityVSAvoidcircuit efficiency

Core Design Contradiction:

Duration of action of moving objectVSLoss of energy

Solution Approach 1:

The bypass unit serves as a mediator that intercepts current during dead time and redirects it through a more efficient path to ground. This prevents the energetically lossy body diode conduction while maintaining continuous current flow, thereby reducing energy losses and improving overall circuit efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bypass unit converts the potentially harmful effect of dead time current flow (which would otherwise cause voltage fluctuations and energy loss through the body diode) into a beneficial outcome by providing a controlled, low-impedance current path that eliminates reverse recovery losses and stabilizes voltage

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The bypass unit significantly reduces body diode reverse recovery, eliminating the issue while maintaining low area costs and providing design flexibility by adjusting breakdown voltage and area according to power supply levels, enhancing overall circuit efficiency.

Implementation Method 1

A bypass unit with a transistor is introduced between the drain of the second transistor and ground, allowing current to bypass the body diode during dead time

Methodology Applied

Scientific EffectElectrical current flow: Conduction (electrical)

Implementation Method 2

with a threshold voltage lower than the body diode, thus minimizing current through the body diode

Methodology Applied

Scientific EffectThreshold voltage effect:

Data Source

PatentUS11189613B2Semiconductor device

Publication Date: 2021.11.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device and a method of forming the same are provided. The semiconductor device includes a transistor and a diode. The transistor includes a first gate region electrically coupled to a gate driver, and a first source region and a first drain region on two sides of the first gate region. The diode includes two terminals coupled between the first drain region of the transistor and a reference voltage. The transistor has a threshold voltage greater than that of the diode.