Synchronous Rectification Controller Open-Circuit Fault Detection

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Solution Overview

Problem

Synchronous rectification DC/DC converters face issues with open-circuit faults in the drain pin, leading to increased power loss and heat generation due to operation in diode rectification mode, and intermittent overvoltage protection causing temperature fluctuations.

Innovation Solution

A synchronous rectification controller with an abnormality detection circuit that monitors the drain pin for open-circuit faults and an auxiliary power supply for extended suspension periods during intermittent operation, preventing diode rectification mode and reducing heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If synchronous rectification transistor is used instead of diode, then power loss is dramatically reduced, but open-circuit fault of drain pin causes operation in diode rectification mode with increased power loss

Engineering Contradiction:

Improvepower lossVSAvoidopen-circuit fault detection

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a feedback mechanism where the controller monitors the drain pin voltage and compares it against expected values. When an open-circuit fault is detected through this feedback loop, the controller switches from synchronous rectification mode to diode rectification mode, ensuring continuous operation while maintaining reliability through active monitoring and response.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The controller acts as an intermediary between the synchronous rectification transistor and the rectification process. It monitors the drain pin voltage and intermediates the switching between synchronous and diode rectification modes, ensuring that power loss is minimized while maintaining system reliability through fault detection and mode transition.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If intermittent overvoltage protection is implemented, then system protection is improved, but temperature fluctuations and heat generation increase

Engineering Contradiction:

Improveovervoltage protectionVSAvoidtemperature fluctuations

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent implements periodic action through controlled suspension of DC/DC converter operation during overvoltage conditions. By periodically suspending and resuming operation in a controlled manner, the system provides overvoltage protection while allowing heat dissipation during suspension periods, thereby reducing temperature fluctuations and heat generation compared to continuous operation or uncontrolled intermittent protection.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS10333415B2Insulated synchronous rectification DC/DC converter including synchronous rectification controller controlling synchronous rectification transistor

Publication Date: 2019.06.25 ROHM CO LTD

AI summary

A synchronous rectification controller configured to control a synchronous rectification transistor is provided on the secondary side of an insulated synchronous rectification DC/DC converter. A DRAIN pin receives the drain voltage VDS2 of the synchronous rectification transistor. A pulse generator generates a pulse signal S11 based on the voltage at the DRAIN pin. A driver drives the synchronous rectification transistor based on the pulse signal S11. Upon detecting an open-circuit fault of the DRAIN pin, an abnormality detection circuit asserts an abnormality detection signal S13.