Active Diode Isolation in Switch-Mode Converters

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Solution Overview

Problem

Existing switch-mode converters and boost devices face inefficiencies due to the limitations of one-way switching devices, such as Schottky diodes, which struggle to isolate reverse currents and maintain high efficiency when boosting voltages exceed supply voltages, leading to potential circuit breakdowns and increased costs.

Innovation Solution

The implementation of an active diode, such as a normally-ON transistor or junction field-effect transistor, which controls the flow of current between the bootstrap node and supply voltage, allowing for efficient isolation and charging of capacitors, thereby enhancing the performance and efficiency of switch-mode converters and boost devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a one-way switching device (Schottky diode) is used to isolate reverse current, then reverse current isolation is improved, but forward current efficiency and integration capability deteriorate

Engineering Contradiction:

Improvereverse current isolationVSAvoidforward current efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the operating parameters of the transistor by applying different control voltages to switch between linear region (for isolation) and saturation region (for conduction). This parameter change allows the same device to perform both forward current conduction and reverse current isolation functions efficiently

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The transistor is designed to perform multiple functions: acting as a diode for reverse current isolation, a switch for forward current conduction, and an amplifier for signal boosting. This multi-functionality eliminates the need for separate Schottky diode and transistor components

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Loss of energy

If a one-way switching device is used to provide forward current, then current conduction is improved, but integration into circuit and cost-effectiveness deteriorate

Engineering Contradiction:

Improveforward current conductionVSAvoidcircuit integration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the functions of the one-way switching device and the transistor into a single transistor component. The transistor's gate controls both forward current conduction and reverse current isolation, eliminating the need for separate diode and transistor components in the circuit

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Power

If bootstrap voltage is boosted above supply voltage, then high-side transistor conduction is improved, but circuit stability and breakdown risk worsen

Engineering Contradiction:

Improvebootstrap voltageVSAvoidcircuit stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent implements feedback control where the control logic monitors the bootstrap voltage level and adjusts the transistor's gate control signal accordingly. When bootstrap voltage exceeds supply voltage, the feedback mechanism activates the transistor's isolation function to prevent further voltage increase and potential breakdown

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The transistor is configured to automatically activate its isolation function when bootstrap voltage exceeds supply voltage, preventing reverse current flow before circuit breakdown can occur. This preliminary protective action ensures circuit stability without requiring external intervention

Inventive Principle:

Principle #9Preliminary anti-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 solution effectively isolates supply voltages from bootstrap nodes when voltages exceed supply levels, preventing circuit breakdowns and improving overall efficiency and cost-effectiveness by integrating active diodes that can be controlled to manage forward and reverse currents.

Implementation Method 1

the active diode isolates the supply voltage from the bootstrap node according to a control signal

Methodology Applied

Scientific EffectElectrical isolation: Diode

Implementation Method 2

The capacitor is coupled between the bootstrap node and the floating reference node

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 3

the high-side transistor provides an input voltage to the floating reference node according to the high-side output signal

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10033260B2Boost devices with active diodes and switch-mode converters thereof

Publication Date: 2018.07.24 VANGUARD INTERNATIONAL SEMICONDUCTOR CORPORATION

AI summary

A switch-mode converter includes a high-side driver, a high-side transistor, a low-side driver, a low-side transistor, a capacitor, and an active diode. The high-side driver is supplied by the bootstrap voltage of the bootstrap node and a floating reference voltage of a floating reference node, and generates the high-side output signal. The high-side transistor provides an input voltage to the floating reference node according to the high-side output signal. The low-side driver generates the low-side output signal. The low-side transistor couples the floating reference node to a ground according to the low-side output signal. The capacitor is coupled between the bootstrap node and the floating reference node. The active diode provides the supply voltage to the bootstrap node. When the bootstrap voltage exceeds the supply voltage, the active diode isolates the supply voltage from the bootstrap node.