SR Controller Feedback for Isolated Power Supply Timing

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Solution Overview

Problem

In isolated switching mode power supplies, improper timing of the synchronous rectifier (SR) controller turning on or off the secondary switch can lead to undesirable results, including damage to the transformer due to reverse polarities and insufficient power efficiency, as conventional diodes are not efficient.

Innovation Solution

A mechanism where the SR controller turns off the secondary switch to trigger a message feedback to the primary side, allowing the primary-side controller to enable energy transfer only after detecting this message, ensuring the secondary switch is fully turned off before the primary switch is turned on, thus preventing simultaneous activation and potential transformer damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the SR controller turns on or off the secondary switch with improper timing, then the synchronous rectifier can increase power supply efficiency compared to conventional diodes, but it may cause reverse polarities that damage the transformer

Engineering Contradiction:

Improvepower supply efficiencyVSAvoidtransformer damage risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the secondary switch turning-off action triggers a message feedback to the primary side controller. The primary side controller detects this feedback message and only enables energy transfer after confirming the secondary switch is fully turned off, thus preventing simultaneous activation and transformer damage while maintaining SR efficiency benefits

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary action by having the SR controller turn off the secondary switch before the primary side controller enables energy transfer. The feedback message mechanism ensures this sequencing is properly executed, preventing reverse polarity conditions that would damage the transformer

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the primary switch is turned on before the secondary switch is fully turned off, then energy transfer can begin, but simultaneous activation of both switches causes reverse polarities and potential transformer damage

Engineering Contradiction:

Improveenergy transfer timingVSAvoidreverse polarity damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The feedback message mechanism provides real-time status information about the secondary switch state to the primary side controller. The primary side controller uses this feedback to determine the appropriate timing for enabling energy transfer, ensuring the secondary switch is fully off before activation to prevent harmful reverse polarities

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary action by ensuring the secondary switch is turned off before the primary switch is activated. The feedback message confirms this preliminary action is complete, allowing safe subsequent activation of the primary switch for energy transfer

Inventive Principle:

Principle #10Preliminary action

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 method effectively reduces the risk of transformer damage by ensuring proper timing of switch activation, enhancing power supply efficiency and reliability by preventing simultaneous on-states of the primary and secondary switches.

Implementation Method 1

the SR controller turns off the secondary switch and triggers the secondary winding to feed back a first message to the primary side circuit

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10116236B2Isolated switching mode power supply with message control between SR and primary side, and control method thereof

Publication Date: 2018.10.30 SYNC POWER CORP

AI summary

An isolated switching mode power supply and a control method of the isolated switching mode power supply are provided. The isolated switching mode power supply includes a primary side circuit and a secondary side circuit. The primary side circuit includes a controller. The secondary side circuit is coupled to the primary side circuit and includes a winding, a switch, and an SR controller. The winding is coupled to the primary side circuit. The switch is coupled to the winding. The SR controller is coupled to the winding and the switch. The SR controller turns off the switch to trigger the winding to feed back a first message to the primary side circuit. The controller enables the primary side circuit to transfer energy to the secondary side circuit if the controller detects the first message.