Light Emitting Device Driving Circuit Overcurrent Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light emitting devices are prone to ground faults and power source faults due to foreign substances, leading to ineffective feedback control and excessive current flow, which can cause circuit elements to overheat.
Innovation Solution
A driving circuit with an overcurrent protection function, incorporating a DC-DC converter, current driver, protection resistor, and controller that adjusts the drive voltage to prevent overvoltage and overcurrent states by activating a protection circuit when the drive voltage exceeds a predetermined threshold, utilizing protection resistors to manage voltage drops and control the drive current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional light emitting devices are used without overcurrent protection, then the device complexity is reduced, but the reliability deteriorates due to ground faults and power source faults causing excessive current flow and overheating
Solution Approach 1:
The patent applies preliminary action by incorporating protection resistors (R1, R2) and overvoltage detection circuitry into the driving circuit before faults occur. The controller continuously monitors the drive voltage VOUT and compares it against a predetermined threshold voltage VOVP1, enabling early detection and activation of protection mechanisms before excessive current can cause damage to circuit elements or LED strings.
Solution Approach 2:
The patent uses protection resistors R1 and R2 as intermediary elements that limit current flow and create detectable voltage drops. These resistors act as mediators between the drive voltage source and the LED strings, providing a controlled path that prevents direct overcurrent damage while enabling voltage monitoring for fault detection.
2Reliability
If overcurrent protection circuitry is added to detect and respond to faults, then the reliability is improved, but the device complexity increases due to additional components
Solution Approach 1:
The patent merges the protection functions into the existing driving circuit by integrating overvoltage detection, current limiting, and fault response capabilities. The controller combines multiple protection tasks into a unified control mechanism that monitors drive voltage and activates protection protocols, reducing the need for separate dedicated protection circuits for each function.
Solution Approach 2:
The protection circuitry is designed with multi-functionality to handle various fault conditions including ground faults, power source faults, and overvoltage conditions. The same protection resistors and detection circuitry serve multiple purposes: current limiting, voltage monitoring, fault detection, and activation of protection protocols, making the protection system universally applicable to different failure modes.
3Stability of the object's composition
If feedback control is used to stabilize drive voltage, then the drive voltage stability is improved, but the response time to faults deteriorates because feedback control becomes ineffective during ground faults
Solution Approach 1:
The system implements preliminary action by continuously monitoring drive voltage against a predetermined threshold VOVP1 independent of the feedback control loop. This allows the protection mechanism to activate immediately upon detecting overvoltage conditions or faults, without waiting for the feedback control to respond, thereby maintaining fast fault response while preserving normal feedback-based voltage stability during operation.
Solution Approach 2:
The patent uses feedback control through the controller to stabilize the drive voltage VOUT under normal operating conditions by adjusting the duty cycle of the DC-DC converter. Simultaneously, a separate overvoltage detection mechanism monitors VOUT against threshold VOVP1, creating a dual-layer system where feedback maintains stability and threshold monitoring ensures rapid fault response.
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 solution effectively reduces the duration and magnitude of overcurrent flow during faults, providing earlier protection activation and minimizing heat generation in circuit elements, thus enhancing the reliability and safety of light emitting devices.
Implementation Method 1
The DC-DC converter 10 supplies a drive voltage VOUT to anodes of the LED strings 4_1 to 4_N by boosting an input voltage VIN
Implementation Method 2
A pair of resistors R11 and R12 divides the drive voltage VOUT. The OVP comparator 38 compares the divided drive voltage VOUT′ with a predetermined threshold voltage VOVP2
Implementation Method 3
Each LED string 4 includes a plurality of LEDs which are connected to each other in series
Data Source
AI summary
A driving circuit for a light emitting element is disclosed. The driving circuit includes a DC-DC converter configured to generate a drive voltage between a first line and a second line; a current driver, configured to be connected to the light emitting element in series between the first line and the second line, configured to supply a drive current to the light emitting element; a protection resistor configured to be connected to the light emitting element in series between the first line and the current driver; and a controller configured to control the DC-DC converter such that a first detection voltage, which corresponds to a voltage between both ends of the current driver, approaches a predetermined reference voltage and perform a predetermined protection process if the drive voltage between the first line and the second line exceeds a predetermined first threshold voltage.