Over-current Protection Circuit with Dual Voltage Comparators
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Solution Overview
Problem
Existing over-current protection circuits in liquid crystal display (LCD) technology face challenges in configuring a precise protection point, leading to potential panel damage due to unpredictable current increases during short-connections, which can result in either false triggering or failure to prevent over-current issues.
Innovation Solution
An over-current protection circuit with a detection circuit, first and second protection branches, utilizing voltage comparators and NMOS transistors to adjust protection voltage by comparing detection voltages with reference voltages, cutting off current input when necessary to prevent over-current damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single fixed protection current threshold is used in the OCP circuit, then the circuit response is simple and fast, but the protection is inaccurate for gradual current increases during short-connections
Solution Approach 1:
The protection circuit is divided into two independent branches: a first protection branch with a first voltage comparator for high-threshold instantaneous protection, and a second protection branch with a second voltage comparator for low-threshold gradual protection. Each branch operates independently with its own threshold, allowing the system to handle both sudden and gradual current increases without requiring a complex adaptive threshold mechanism.
2Reliability
If the protection point is set too high, then false triggering is reduced, but panels with short-connections may be missed and could be damaged
Solution Approach 1:
The circuit dynamically selects which protection branch activates based on the actual current conditions. The first protection branch activates for sudden high-current short-connections, while the second protection branch activates for gradual current increases. This dynamic response ensures both high-current and low-current short-connection scenarios are protected without false triggering.
3Object-affected harmful factors
If the protection point is set too low, then all short-connections are protected, but false triggering occurs for normal operation currents
Solution Approach 1:
By segmenting the protection function into two branches with different thresholds, the system avoids false triggering while maintaining comprehensive protection. The first branch with higher threshold prevents false triggering during normal operation, while the second branch with lower threshold ensures coverage for gradual short-connections, together providing complete protection without false alarms.
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
The proposed solution effectively adjusts protection voltage to prevent over-current issues, ensuring the LCD panel is protected from damage by accurately detecting and responding to current changes, thereby enhancing the reliability of the over-current protection mechanism.
Implementation Method 1
the first voltage comparator compares the first detection voltage with the first reference voltage
Implementation Method 2
the first FET is turned off when the first detection voltage is smaller than the first reference voltage
Implementation Method 3
the detection circuit is configured for detecting a current of an output end of the over-current protection circuit in a real-time manner, and for obtaining a first detection voltage in accordance with the current
Data Source
AI summary
An over-current protection circuit includes a detection circuit, a first protection branch, and a second protection branch. The detection circuit is configured for obtaining a first detection voltage. The first protection branch compares the first detection voltage and the first reference voltage. When the first detection voltage is smaller than the first reference voltage, the detection circuit obtains the second detection voltage. The second protection branch compares the second detection voltage and the second reference voltage. When the second detection voltage is greater than or equals to the second reference voltage, the second protection branch cuts off the current inputted to the input end of the over-current protection circuit. The second reference voltage equals to the reference detection voltage plus the predetermined initial value. The over-current protection circuit may amend the protection voltage to avoid over-current issue.