High-Side Synchronous Rectifier Control Circuit for Power Converters

Solution Overview

Problem

Traditional synchronous rectifier controllers in power converters suffer from switching loss and electric-magnetic-interference (EMI) due to the switching operation of the secondary side's ground, which affects efficiency and performance.

Innovation Solution

A control circuit comprising a linear predict circuit, a reset circuit, and a PWM circuit is installed between the secondary side and the output of the power converter, coupled with a power switching device and a diode, to control the switching operation, allowing the ground terminal to be decoupled from the low-side secondary side ground, reducing switching loss and EMI.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the synchronous rectifier controller is installed on the low-side of the secondary side with ground terminal coupled to secondary side ground, then the controller can be simply connected and operated, but switching loss and EMI problems occur due to switching operation of the ground

Engineering Contradiction:

Improveconnection simplicityVSAvoidswitching loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent introduces an isolated coupling mechanism (optical or magnetic coupling) as an intermediary between the control circuit and the power switching device. This allows the control circuit ground to be separated from the power circuit ground, eliminating the ground switching path while maintaining control functionality through the isolated coupling channel.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the ground paths by using isolation technology to separate the control circuit ground from the power circuit ground. This segmentation prevents the ground switching current from flowing through the shared ground path, thereby eliminating the EMI and switching loss issues while maintaining independent grounding for each circuit domain.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If the synchronous rectifier controller is installed on the low-side of the secondary side with ground terminal coupled to secondary side ground, then the controller can be simply connected and operated, but EMI problems occur due to switching operation of the ground

Engineering Contradiction:

Improveoperation simplicityVSAvoidEMI

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an isolated coupling mechanism (optical or magnetic coupling) as an intermediary between the control circuit and the power switching device. This allows the control circuit ground to be separated from the power circuit ground, eliminating the ground switching path while maintaining control functionality through the isolated coupling channel.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the ground paths by using isolation technology to separate the control circuit ground from the power circuit ground. This segmentation prevents the ground switching current from flowing through the shared ground path, thereby eliminating the EMI and switching loss issues while maintaining independent grounding for each circuit domain.

Inventive Principle:

Principle #1Segmentation

3Loss of energy

If the ground terminal is decoupled from the low-side secondary side ground, then switching loss and EMI are reduced, but the control circuit becomes more complex

Engineering Contradiction:

Improveswitching lossVSAvoidcontrol circuit complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent introduces an isolated coupling mechanism (optical or magnetic coupling) as an intermediary between the control circuit and the power switching device. This allows the control circuit ground to be separated from the power circuit ground, eliminating the ground switching path while maintaining control functionality through the isolated coupling channel.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8625313B2High-side synchronous rectifier circuits and control circuits for power converters

Publication Date: 2014.01.07 SEMICON COMPONENTS IND LLC

AI summary

A control circuit for a switching power converter is provided. The control circuit is installed between a secondary side and an output of the power converter and coupled to control a switching device. The control circuit includes a linear predict circuit, a reset circuit, a charge/discharge circuit, and a PWM circuit. The linear predict circuit is coupled to receive a linear predict signal from the secondary side for generating a charging signal. The reset circuit is couple to receive a resetting signal for generating a discharging signal. The charge/discharge circuit is coupled to receive the charging signal and the discharging signal for generating a ramp signal. The PWM circuit is coupled to receive the linear predict signal for enabling a switching signal and receive the ramp signal for resetting the switching signal.