Upper-Lower Arm Switch Drive Circuit for Dead-Time Self Turn-On

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Solution Overview

Problem

Existing drive circuits for upper- and lower-arm switches with body diodes face issues with self turn-on and deterioration, particularly during dead time, where the lower-arm switch is inadvertently turned on due to feedback capacitance, and maintaining a negative voltage to prevent this accelerates switch deterioration.

Innovation Solution

A drive circuit that controls the electric potential of the control terminal relative to the second terminal of the target switch to be negative over a prescribed period after the target switch is switched off and until the opposing arm switch is set to the on-state, and then maintains it at an off-voltage until the next dead time, thereby suppressing self turn-on and reducing deterioration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a negative voltage is maintained at the control terminal during dead time to prevent self turn-on, then self turn-on is suppressed, but switch deterioration accelerates

Engineering Contradiction:

Improveself turn-on suppressionVSAvoidswitch lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The drive circuit applies negative voltage only during specific periodic intervals (dead time periods) rather than continuously, thereby preventing self turn-on only when necessary while minimizing the total duration of negative voltage exposure to reduce switch deterioration

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control circuit proactively applies negative voltage to the control terminal before the opposing arm switch is turned on, during the dead time period, to preemptively prevent self turn-on of the target switch while limiting the duration to only what is necessary for prevention

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the negative voltage maintenance period is extended to ensure complete suppression of self turn-on, then reliability improves, but the progression of switch deterioration increases

Engineering Contradiction:

Improveself turn-on suppressionVSAvoidswitch deterioration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control circuit applies negative voltage for the minimum necessary duration during dead time periods - not excessively long - thereby achieving sufficient self turn-on suppression while limiting the harmful exposure time that causes switch deterioration

Inventive Principle:

Principle #16Partial or excessive action

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

This approach effectively suppresses self turn-on of the target switch and shortens the period of negative voltage maintenance, thereby reducing the progression of switch deterioration compared to previous technologies.

Implementation Method 1

the lower-arm switch is inadvertently turned on due to feedback capacitance

Methodology Applied

Scientific EffectFeedback capacitance: Capacitance

Implementation Method 2

The drive circuit maintains an electric potential of a control terminal, relative to a second terminal of the target switch, at a negative voltage

Methodology Applied

Scientific EffectElectric potential control: Electric Field

Data Source

PatentUS11848599B2Drive circuit for driving an upper arm switch and a lower arm switch each having a body diode

Publication Date: 2023.12.19 DENSO CORP

AI summary

A drive circuit for a switch drives an upper-arm switch and a lower-arm switch that include body diodes. Of the body diodes in upper- and lower-arm switches, the diode through which a feedback current flows during a dead time is a target diode. Of the upper- and lower-arm switches, the switch that includes the target diode is a target switch. The remaining switch is an opposing arm switch. The drive circuit maintains an electric potential of a control terminal relative to a second terminal of the target switch at a negative voltage over a period from a timing subsequent to a start timing of a dead time immediately after the target switch is switched to an off-state until a point within a period over which the opposing arm switch is set to an on-state, and subsequently maintains the electric potential at an off-voltage until a next dead time is ended.