LED Backlight Driving Circuit Short-Circuit Protection
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Solution Overview
Problem
The existing LED backlight driving circuits face issues with power loss, high temperature, and cost due to the use of isolation MOS transistors for short-circuit protection, which also pose security risks when the LED electrodes are shorted.
Innovation Solution
An LED backlight driving circuit with a voltage converting unit, a driving unit, a protection unit, and a control unit, where the protection unit is a resistor with a resistance less than a preset value, and the control unit outputs a signal to stop the driving unit when a short circuit occurs, effectively cutting off the connection and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation MOS transistor is added to the negative electrode of the LED for short-circuit protection, then the circuit protection function is improved, but the power loss increases and temperature rises
Solution Approach 1:
The patent extracts the protection function from the MOS transistor and implements it through a different mechanism: using a fuse-like protection unit that opens the circuit upon short-circuit detection, combined with a control unit that stops the driving signal. This separates the protection function from the power conduction path, eliminating the continuous power loss associated with MOS transistor operation.
Solution Approach 2:
The protection unit is designed as a disposable element that sacrifices itself (opens the circuit) when a short circuit occurs. This low-cost, single-use protection mechanism replaces the expensive and power-consuming MOS transistor, achieving protection without continuous energy loss.
2Reliability
If an isolation MOS transistor is used for short-circuit protection, then the circuit protection function is improved, but the cost increases
Solution Approach 1:
The protection unit uses a simple, low-cost design that sacrifices itself during short-circuit events. This disposable approach with basic components (resistors, fuses, control logic) replaces the expensive MOS transistor, significantly reducing overall circuit cost while maintaining protection functionality.
Solution Approach 2:
The patent uses a control unit that generates control signals to stop the driving unit when a short circuit is detected. This control mechanism copies the protection function from expensive active components to a simpler control logic system, reducing hardware costs.
3Reliability
If an isolation MOS transistor is used for short-circuit protection, then the circuit protection function is improved, but security risks remain when LED electrodes are shorted
Solution Approach 1:
The patent extracts the high voltage from the circuit by opening the protection unit circuit upon short-circuit detection. This removes the harmful high voltage factor from the system, preventing security risks associated with voltage leakage to the shell or user-accessible parts.
Solution Approach 2:
The control unit proactively stops the driving unit and opens the protection unit when a short circuit is detected, preventing high voltage from reaching unsafe levels before they can cause security risks. This preliminary action eliminates the harmful effect before it can manifest.
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 solution provides secure and reliable short-circuit protection, reduces power loss and temperature, and lowers costs by using a resistor instead of an isolation MOS transistor, while ensuring the circuit parts are protected from high voltage hazards.
Implementation Method 1
a maximum allowable power of the protection unit is less than a power when the driving voltage of the LED is directly applied to the protection unit so as to form an open circuit when the positive and negative electrodes of the LED are shorted
Data Source
AI summary
An LED backlight driving circuit has a voltage converting unit having an output terminal connected to a positive electrode of an LED to provide a driving voltage required by the LED, a driving unit to control the voltage converting unit to achieve a voltage conversion, and a protection unit connected in series between a negative electrode of the LED and the driving unit. A maximum allowable power of the protection unit is less than a power when the driving voltage of the LED is directly applied to the protection unit. The circuit also includes a control unit for outputting a control signal for stopping working to the driving unit when the protection unit forms an open circuit. Thus, the circuit parts can be protected, and the short-circuit protection function is more safe and reliable.