Synchronous Rectifier Drive Circuit Using Auxiliary Windings

Solution Overview

Problem

Self-driven synchronous rectifiers of forward type experience significant power loss and thermal stress due to inefficient drive circuits, especially when handling high input DC voltages.

Innovation Solution

The implementation of a power converter with a primary side power circuit, a secondary side power circuit, and a synchronous rectifier drive circuit that utilizes magnetic coupling between auxiliary windings and output inductor windings to reduce power loss, including the arrangement of windings around a common core and embedding them within a printed circuit board, and the use of passive drive circuits to eliminate switching devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional drive circuits are used in self-driven synchronous rectifiers, then the rectifier can operate with wide input DC voltage range, but significant power loss and thermal stress occur

Engineering Contradiction:

Improveinput DC voltage rangeVSAvoidpower loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent replaces active switching devices with passive drive circuitry consisting of auxiliary windings and diodes. The drive signals are generated passively through magnetic coupling from the primary and output inductor windings, eliminating the need for active switching components in the drive circuit and significantly reducing power loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The drive circuit for the synchronous rectifier is self-generated through passive magnetic coupling. The auxiliary windings on the transformer and output inductor automatically produce the necessary drive voltages during normal operation, without requiring external active control components. The system uses its own operating signals to drive the rectifier switches.

Inventive Principle:

Principle #25Self-service

2Ease of operation

If active switching devices are used in drive circuits, then precise control can be achieved, but device complexity and cost increase

Engineering Contradiction:

Improvecontrol precisionVSAvoidswitching devices

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The patent replaces active switching devices with passive drive circuitry consisting of auxiliary windings and diodes. The drive signals are generated passively through magnetic coupling from the primary and output inductor windings, eliminating the need for active switching components in the drive circuit and significantly reducing power loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and removes the active switching devices from the drive circuit, retaining only the essential passive components (auxiliary windings and diodes) needed to generate drive signals. This simplification eliminates complex control circuitry while maintaining functional effectiveness.

Inventive Principle:

Principle #2Taking out (Extraction)

3Power

If high input DC voltage is handled, then power conversion capability increases, but thermal stress on drive circuits intensifies

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidthermal stress

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent replaces active switching devices with passive drive circuitry consisting of auxiliary windings and diodes. The drive signals are generated passively through magnetic coupling from the primary and output inductor windings, eliminating the need for active switching components in the drive circuit and significantly reducing power loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the high voltage present in the system into a beneficial effect by using the primary winding and output inductor winding to generate positive drive voltages through magnetic coupling. The high voltage, which would normally cause excessive power loss, is instead utilized to automatically generate the necessary drive signals for the synchronous rectifier, reducing thermal stress on drive circuits.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly reduces power loss and thermal stress in the drive circuits and synchronous rectifiers, improving efficiency and reducing costs by minimizing the need for active switching devices.

Implementation Method 1

The first auxiliary winding is inductively coupled to the primary winding and forms a second magnetic coupling with the primary winding. The second auxiliary winding is inductively coupled to the output inductor winding and forms a third magnetic coupling with the output inductor winding.

Methodology Applied

Scientific EffectMagnetic coupling: Electromagnetic Induction

Data Source

PatentUS9595878B2Drive circuit for synchronous rectifier and method thereof

Publication Date: 2017.03.14 ACLEAP POWER INC

AI summary

A power converter includes a primary side power circuit, a secondary side power circuit, and a synchronous rectifier drive circuit. The primary side power circuit includes a primary winding and a main switch coupled in series. The main switch is turned on and off in response to control signals. The secondary side power circuit includes a secondary winding, at least one synchronous rectifier switch, and an output inductor winding. The secondary winding is inductively coupled to the primary winding and forms a first magnetic coupling with the primary winding. The synchronous rectifier drive circuit includes a first and a second auxiliary winding coupled in series. The first auxiliary winding is inductively coupled to the primary winding and forms a second magnetic coupling with the primary winding. The second auxiliary winding is inductively coupled to the output inductor winding and forms a third magnetic coupling with the output inductor winding.