Gate-Controlled Diode for Power Converter Loss Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional flywheel diodes face a tradeoff between reducing forward voltage drop and backward recovery current, leading to increased conduction and switching losses, and the generation of bounce voltage, which hinders the efficiency and cost-effectiveness of power converters.

Innovation Solution

A semiconductor device with a gate-controlled diode that switches between pn and Schottky diode modes, allowing for reduced forward voltage and backward recovery current, thereby minimizing conduction and switching losses and suppressing bounce voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a pn diode is used to reduce forward voltage drop, then conduction loss decreases, but bounce voltage increases due to large backward recovery current

Engineering Contradiction:

Improveconduction lossVSAvoidbounce voltage

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The diode function is segmented into two separate components: the pn diode for forward conduction and the Schottky diode for backward recovery. This segmentation isolates the bounce voltage generation to only the forward conduction phase (where it is beneficial) while eliminating excessive backward recovery current during switching, thus reducing harmful bounce voltage effects

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The Schottky diode acts as an intermediary during backward recovery, providing a low-impedance path for reverse current that minimizes charge injection into the circuit. This intermediary function prevents the large backward recovery currents that cause bounce voltage, while the pn diode continues to provide low forward voltage drop

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution significantly reduces the overall losses and noise in the semiconductor device and power converter, enhancing efficiency and promoting widespread use in energy-saving and renewable energy technologies.

Implementation Method 1

a pn diode made of silicon to have the ability to increase the conductivity by injecting electric charges is generally used to decrease the forward voltage drop

Methodology Applied

Scientific EffectElectric charge injection:

Implementation Method 2

a Schottky diode is available in which the amount of injected electric charges is small and the backward recovery current is very small

Methodology Applied

Scientific EffectSchottky barrier effect:

Implementation Method 3

the flywheel diode 600a is so operated as to commutate the current having been flowing through the IGBT 700a to a flywheel diode 600b connected to an IGBT 700b

Methodology Applied

Scientific EffectDiode conduction: Diode

Data Source

PatentEP2365532B1Semiconductor device and power converter using it

Publication Date: 2019.08.07 HITACHI LTD

Figure 1~2
Figure 3
Figure 4

AI summary

A semiconductor device and a power converter using it wherein a switching power device (700) and a flywheel diode (100) are connected in series, the flywheel diode (100) includes a region (30) having a Schottky junction (16) to operate as a Schottky diode and a region (17) having a pn junction to operate as a pn diode and control operation is performed such that when current flows forwardly through the flywheel diode, the pn diode operates and when the flywheel diode recovers backwardly, the Schottky diode operates mainly.