Synchronous Rectifier Control for Zero-Voltage Switching Converters

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional power converters with low operation voltage and high operation current face challenges in achieving high power efficiency due to the decreasing power efficiency of rectification circuits as voltage decreases.

Innovation Solution

The implementation of synchronous rectification techniques in power converters, which replace Schottky diodes with low on-resistance power metal-oxide-semiconductor field-effect transistors (MOSFETs), to enhance power efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If Schottky diodes are used for rectification in low voltage power converters, then the circuit structure is simple, but power efficiency decreases

Engineering Contradiction:

Improverectification circuit structureVSAvoidpower efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent changes the key parameter from diode on-voltage drop to MOSFET on-resistance. By using MOSFETs with low on-resistance values, the rectification circuit achieves lower power loss at low operating voltages compared to Schottky diodes, directly resolving the contradiction between simplicity and efficiency.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes the passive diode rectification mechanism with active MOSFET-based synchronous rectification. This replacement enables controlled switching and lower resistance paths, transforming the rectification process from a passive voltage-drop mechanism to an active low-resistance conduction mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If synchronous rectification with MOSFETs is implemented, then power efficiency improves, but device complexity increases

Engineering Contradiction:

Improvepower efficiencyVSAvoidrectification circuit structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent integrates multiple functions into the synchronous rectification circuit, including rectification, zero-voltage switching control, and body diode utilization. The MOSFETs serve both as switching elements and as rectification elements, while their body diodes provide natural clamping and zero-voltage switching paths, reducing the need for additional components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent employs the intrinsic body diodes of the MOSFETs to provide zero-voltage switching paths and voltage clamping functions. This self-service approach eliminates the need for external clamp diodes or complex control circuits, as the MOSFETs' own body diodes perform the protective and switching functions.

Inventive Principle:

Principle #25Self-service

3Loss of energy

If zero voltage switching is achieved, then switching losses are reduced, but control complexity increases

Engineering Contradiction:

Improveswitching lossesVSAvoidcontrol circuit

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent prepares the switching conditions in advance by ensuring the MOSFETs are turned on before the voltage transitions occur. The control circuit anticipates the voltage waveform and pre-charges or pre-discharges the MOSFET gates to establish the correct conduction state before the zero-voltage crossing point, minimizing switching losses.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses voltage sensing and timing feedback to detect the zero-voltage crossing points and adjust the MOSFET switching timing accordingly. The control circuit monitors the voltage waveform and uses this feedback to synchronize the MOSFET gate drive signals with the voltage transitions, achieving optimal zero-voltage switching conditions.

Inventive Principle:

Principle #23Feedback

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

Synchronous rectification significantly improves power efficiency by reducing heat generation and enhancing current generation capability, particularly in systems with large output currents.

Implementation Method 1

replacing the Schottky diode with a power metal-oxide-semiconductor field-effect transistors (MOSFET) with low on-resistance

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Data Source

PatentUS20250125738A1Systems and methods for controlling synchronous rectifiers in power converters with zero voltage switching

Publication Date: 2025.04.17 ON BRIGHT INTEGRATIONS CO INC

AI summary

System and method for controlling synchronous rectification. For example, a system for controlling synchronous rectification includes: a first control-signal generator configured to generate a first control signal; a second control-signal generator configured to receive the first control signal for a first switching cycle and generate a second control signal for a second switching cycle based at least in part on the first control signal for the first switching cycle, the first switching cycle preceding the second switching cycle; and a driver configured to receive the first control signal and generate a drive voltage based at least in part on the first control signal; wherein the second control-signal generator is further configured to: process information associated with the first control signal; determine a first time duration when the first control signal remains at a first logic level during the first switching cycle.