Active Charge Control Diode for Reverse Recovery Current Reduction

Solution Overview

Problem

Conventional diodes face significant reverse recovery current issues during turn-off, leading to performance degradation and increased conductive losses, which are typically mitigated by minimizing minority carrier lifetimes but result in higher voltage drops during forward conduction.

Innovation Solution

The introduction of an additional control terminal on the diode, closest to the p-n junction and separated by an insulated trench, allows for active charge control by reducing minority carrier density before turn-off, thereby minimizing reverse recovery current through controlled voltage manipulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If minority carrier lifetimes are minimized to reduce reverse recovery current, then reverse recovery charge is reduced, but forward voltage drop increases

Engineering Contradiction:

Improvereverse recovery currentVSAvoidforward voltage drop

Core Design Contradiction:

Object-generated harmful factorsVSLoss of energy

Solution Approach 1:

The control terminal is activated before the diode turn-off to preliminarily reduce the minority carrier density in the drift region. This pre-action removes excess carriers before the reverse recovery event, thereby reducing reverse recovery charge without requiring minimized carrier lifetimes that would increase forward voltage drop.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

An additional control terminal is introduced as an intermediary element to actively manage the carrier population in the drift region. This control terminal provides a separate pathway to influence carrier density independently of the anode-cathode junction, enabling reverse recovery control without compromising forward conduction characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If conventional diodes are used without control terminal, then device complexity is low, but reverse recovery charge is large

Engineering Contradiction:

Improvereverse recovery chargeVSAvoiddiode structure

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

An additional control terminal is introduced as an intermediary element to actively manage the carrier population in the drift region. This control terminal provides a separate pathway to influence carrier density independently of the anode-cathode junction, enabling reverse recovery control without compromising forward conduction characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The control terminal is activated before the diode turn-off to preliminarily reduce the minority carrier density in the drift region. This pre-action removes excess carriers before the reverse recovery event, thereby reducing reverse recovery charge without requiring minimized carrier lifetimes that would increase forward voltage drop.

Inventive Principle:

Principle #10Preliminary action

3Object-generated harmful factors

If control terminal is driven to voltage outside anode-cathode voltage range, then reverse recovery current is reduced, but control circuit complexity increases

Engineering Contradiction:

Improvereverse recovery currentVSAvoidcontrol terminal circuit

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The control terminal is driven to voltage levels outside the normal anode-cathode voltage range (e.g., more negative than cathode or more positive than anode). This parameter change creates strong electric fields that efficiently extract minority carriers from the drift region, reducing reverse recovery current despite increased control circuit complexity.

Inventive Principle:

Principle #35Parameter changes

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 significantly reduces reverse recovery current while maintaining a low forward voltage drop, enhancing the performance of power diodes by allowing for longer minority carrier lifetimes and reduced conductive losses.

Implementation Method 1

the control terminal is driven to a voltage which is not within the range of the anode and cathode voltages... the control terminal is driven to reduce the minority carrier density before the zero-crossing of current

Methodology Applied

Scientific EffectCarrier density control through voltage manipulation: Electric Field

Data Source

PatentUS9787304B2Methods, systems, and devices for active charge control diodes

Publication Date: 2017.10.10 IDEAL POWER INC

AI summary

Methods and systems for active charge control diodes with improved reverse recovery characteristics. An extra control terminal is added on the side of a diode nearest to its p-n junction. The control terminal connects to a control region which extends from the drift region to the cathode surface and which is most preferably separated from the cathode region by an insulated trench. During turn-off, the control terminal is most preferably driven negative relative to the cathode just before reversing the polarity of the applied external voltage.