Predicting Magnetic Device Discharge Time for Synchronous Rectifier Control

Solution Overview

Problem

Conventional switching regulators experience power losses and efficiency reduction due to reverse current issues under light and no load conditions, which existing methods attempt to mitigate through current sensing circuits, but these add complexity and power losses.

Innovation Solution

An evaluation circuit predicts the discharge time of a magnetic device to proactively turn off the synchronous rectifier using an auxiliary signal, generated based on input and control signals, preventing reverse current without the need for current sensing circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If a current sensing circuit is used to detect reverse current and turn off the synchronous rectifier, then reverse current can be limited, but power losses increase and system complexity increases

Engineering Contradiction:

Improvereverse currentVSAvoidpower losses

Core Design Contradiction:

Object-generated harmful factorsVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by predicting the discharge time of the magnetic device in advance and turning off the synchronous rectifier before reverse current occurs. The evaluation circuit calculates the predicted discharge time based on the relationship between input voltage, output voltage, and switching parameters, and generates a timing signal to turn off the synchronous rectifier proactively, eliminating the need for current sensing circuits and avoiding the power losses associated with them.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and removes the current sensing circuit from the system entirely. Instead of using a current sensing circuit to detect reverse current, the invention uses an evaluation circuit that predicts discharge time based on voltage and switching parameters, completely eliminating the need for current sensing and the associated power losses and complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-generated harmful factors

If a current sensing circuit is used to detect reverse current, then reverse current can be limited, but device complexity increases

Engineering Contradiction:

Improvereverse currentVSAvoidsystem complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts and removes the current sensing circuit from the system entirely. Instead of using a current sensing circuit to detect reverse current, the invention uses an evaluation circuit that predicts discharge time based on voltage and switching parameters, completely eliminating the need for current sensing and the associated power losses and complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies preliminary action by predicting the discharge time of the magnetic device in advance and turning off the synchronous rectifier before reverse current occurs. The evaluation circuit calculates the predicted discharge time based on the relationship between input voltage, output voltage, and switching parameters, and generates a timing signal to turn off the synchronous rectifier proactively, eliminating the need for current sensing circuits and avoiding the power losses associated with them.

Inventive Principle:

Principle #10Preliminary action

3Object-generated harmful factors

If the synchronous rectifier is turned off after reverse current is detected, then reverse current effects can be limited, but time loss occurs due to detection delay

Engineering Contradiction:

Improvereverse current effectsVSAvoiddetection delay

Core Design Contradiction:

Object-generated harmful factorsVSLoss of time

Solution Approach 1:

The patent applies preliminary action by predicting the discharge time of the magnetic device in advance and turning off the synchronous rectifier before reverse current occurs. The evaluation circuit calculates the predicted discharge time based on the relationship between input voltage, output voltage, and switching parameters, and generates a timing signal to turn off the synchronous rectifier proactively, eliminating the need for current sensing circuits and avoiding the power losses associated with them.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7511466B2Method and apparatus for predicting discharge time of magnetic device for power converter

Publication Date: 2009.03.31 SEMICON COMPONENTS IND LLC

AI summary

A method and apparatus for predicting the discharge time of magnetic device are provided. A switching circuit generates a switching signal and an auxiliary signal. The switching signal is used to regulate the switching regulator. The auxiliary signal is used to control the synchronous rectifier. An evaluation circuit generates a timing signal in response to an input signal and the switching signal. The input signal is correlated to the input voltage of the switching regulator. The timing signal is formed for turning off the synchronous rectifier for preventing a reverse current under light load and no load conditions.