Power Conversion Circuit Short-Circuit Detection via PFM Frequency

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Solution Overview

Problem

Existing power conversion circuits for display panels face challenges in detecting short-circuit conditions effectively, particularly due to manufacturing defects or aged components, which can lead to damage, and often rely on analog circuits that increase complexity and reduce reliability.

Innovation Solution

A digital short-circuit detection method using a power conversion circuit with a second power converter operating in pulse frequency modulation mode, where the switching frequency is proportional to the leakage current, allowing for digital circuitry implementation and adjustable detection levels, thereby reducing circuit area and improving reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If analog circuits are used for short-circuit detection, then detection function is achieved, but circuit area increases and reliability decreases

Engineering Contradiction:

ImprovereliabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces analog detection circuits with a digital detection system. The second power converter operates in PFM mode where the switching frequency serves as the detection signal, eliminating the need for separate analog comparison circuits. This substitution of analog mechanisms with digital frequency-based detection reduces circuit area and improves reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The second power converter serves dual functions: it provides the second driving voltage for normal operation and simultaneously performs short-circuit detection through its switching frequency characteristics. This multi-functionality eliminates dedicated detection hardware, reducing overall circuit complexity while maintaining detection capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If analog circuits are used for short-circuit detection, then detection function is achieved, but circuit area increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidcircuit area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent replaces physical analog comparison circuits with digital frequency measurement. The switching frequency of the second power converter in PFM mode directly indicates leakage current levels, allowing detection through digital counting rather than analog voltage comparison. This significantly reduces the required circuit area while maintaining detection accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The second power converter's own switching frequency serves as the detection parameter. By operating in PFM mode, the converter naturally produces a frequency signal that reflects the leakage current state, eliminating the need for separate detection hardware and reducing overall circuit area.

Inventive Principle:

Principle #25Self-service

3Ease of manufacture

If switching frequency is used for detection, then digital implementation is enabled, but detection precision must be maintained

Engineering Contradiction:

ImprovemanufacturabilityVSAvoiddetection precision

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent substitutes analog voltage comparison with digital frequency measurement. The switching frequency of the second power converter in PFM mode is directly proportional to leakage current, allowing precise detection through digital counters and frequency-to-digital converters. This approach enables standard digital manufacturing processes while maintaining high detection precision through the direct relationship between frequency and leakage current.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach enables efficient detection of short-circuit conditions by measuring the switching frequency, which is inversely proportional to leakage resistance, allowing for accurate shutdown and preventing system damage, while simplifying the circuit design and enhancing reliability.

Implementation Method 1

the second power converter is configured to operate in a pulse frequency modulation mode to regulate the second driving voltage to a short-circuit detection level

Methodology Applied

Scientific EffectPulse Frequency Modulation:

Implementation Method 2

the switching frequency relates to a leakage current between the second driving voltage and the first driving voltage

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Data Source

PatentUS11811320B2Power conversion circuit having short-circuit detection function and short-circuit detection method thereof

Publication Date: 2023.11.07 RICHTEK TECH

AI summary

A power conversion circuit includes a first and a second power converters for generating a first and a second driving voltages respectively. The second power converter is a switching converter. In a short-circuit detection mode, the first driving voltage is regulated to the first driving level, and the second power converter is configured to operate in a pulse frequency modulation mode to regulate the second driving voltage to a short-circuit detection level, and when a switching frequency of the second power converter exceeds a threshold frequency, a short-circuit condition between the second driving voltage and the first driving voltage is determined.