Synchronous Bootstrap Gate Drivers for Low-Droop Power Delivery

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Solution Overview

Problem

Conventional gate drivers in power converters suffer from inefficiencies due to diode-based bootstrapping, leading to voltage droop and increased complexity, especially in high-switch-count converters like Flying Capacitor Multi-Level (FCML) converters.

Innovation Solution

Implementing synchronous bootstrapping using active switches controlled by the switching activity of adjacent power switches, eliminating the need for diodes and local regulation, and allowing bi-directional charge flow to reduce path impedance and voltage droop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If diode-based bootstrapping is used in cascaded gate drivers, then power delivery can be achieved, but voltage droop and power loss increase due to diode forward voltage drops

Engineering Contradiction:

Improvepower lossVSAvoidcomplexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent changes the fundamental parameter of the power delivery mechanism by replacing passive diode-based bootstrapping with active synchronous switching. This transitions the system from relying on diode forward voltage characteristics to using controlled active switches, thereby eliminating the fixed voltage drop and reducing power loss while maintaining manageable complexity through integrated control

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the mechanical/passive diode-based power delivery system with an active electronic switching system. By using controlled switches instead of passive diodes, the system replaces a inherently lossy mechanism with one that can be dynamically controlled to minimize losses, directly addressing the power loss issue without proportionally increasing complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Volume of stationary object

If diode-based bootstrapping is used in high-switch-count converters, then power delivery to gate drivers is enabled, but converter volume increases due to required local regulation

Engineering Contradiction:

Improveconverter volumeVSAvoidpower delivery efficiency

Core Design Contradiction:

Volume of stationary objectVSLoss of energy

Solution Approach 1:

The patent extracts and eliminates the need for local regulation stages that are required in diode-based bootstrapping systems. By removing this bulky and lossy intermediate regulation layer through the use of synchronous bootstrapping, the system achieves both volume reduction and improved power delivery efficiency simultaneously

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The synchronous bootstrapping mechanism serves multiple functions: it provides power delivery, eliminates the need for separate local regulation, and reduces overall system volume. This multi-functionality allows the system to address both volume and efficiency concerns with a single integrated approach rather than requiring separate solutions for each problem

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If conventional cascaded gate drivers are used, then power conversion can be performed, but power delivery efficiency decreases due to accumulated diode drops

Engineering Contradiction:

Improvepower delivery efficiencyVSAvoidvoltage stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by proactively compensating for voltage drops through synchronous charging of bootstrap capacitors before they are needed. This prevents voltage instability from occurring in the first place, thereby maintaining both high power delivery efficiency and voltage stability without requiring reactive corrections

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If diode-based bootstrapping is used, then gate driver power can be delivered, but control complexity increases due to additional control signals and level-shifting requirements

Engineering Contradiction:

Improvecontrol complexityVSAvoidpower delivery capability

Core Design Contradiction:

Device complexityVSPower

Solution Approach 1:

The patent implements self-service by having the synchronous switches automatically controlled by the existing power switch gate signals. The system uses its own existing control infrastructure to drive the bootstrap mechanism, eliminating the need for separate control signals and level-shifting circuitry, thereby reducing control complexity while maintaining full power delivery capability

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12463533B2Bi-directional synchronous bootstrapping

Publication Date: 2025.11.04 RGT UNIV OF CALIFORNIA

AI summary

An apparatus and method for delivering power to the gate-drivers used in switching power conversion devices. In a bootstrapping network gate drivers are cascaded between a high-side and a low-side. Each gate driver controls a bidirectional active switch along a synchronous bootstrapping power path. The bootstrapping power path contains at least two bias voltage supplies to provide for bidirectional charge flow to the gate drivers, so that balanced delivery of charge can be maintained. A bias voltage supply on the high-side is line-referenced and provides charge to the bootstrapping network in a downward flowing direction.