LED Backlight Driving Circuit Shunt Switch for IC Overheating
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Solution Overview
Problem
In liquid crystal display (LCD) devices, when LEDs are short-circuited, the resulting high voltage difference causes heating in the control integrated circuit (IC), leading to reduced display brightness and compromised display quality due to the need to switch off the LED strings to prevent IC overheating.
Innovation Solution
An LED backlight driving circuit with a shunt controllable switch connected in series with the LED lightbar and control IC, which switches on when the output voltage exceeds a preset value, diverting current away from the IC and incorporating operational amplifiers and voltage dividing resistors for heat dissipation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are connected in series to form LED lightbars and connected with control IC, then display brightness is improved, but when LEDs are short-circuited the control IC overheats and display quality deteriorates
Solution Approach 1:
A shunt controllable switch is introduced as an intermediary component between the LED lightbar and control IC. When LED short-circuit is detected through voltage detection, the shunt switch activates to create an alternative current path, diverting current away from the control IC and preventing overheating while maintaining system operation
Solution Approach 2:
The system monitors voltage parameters at the output end of LED lightbar. When voltage exceeds a preset threshold indicating LED short-circuit, the control circuit changes the state parameter of the shunt controllable switch from off to on, dynamically adjusting current distribution based on detected electrical parameters
2Temperature
If shunt controllable switch is activated to divert current from control IC, then control IC temperature is reduced, but system complexity increases
Solution Approach 1:
The shunt controllable switch is equipped with automatic control circuitry including operational amplifiers and voltage detection components that autonomously monitor LED status and activate the shunt path without requiring external intervention. The system self-regulates based on voltage thresholds, reducing the need for complex external control mechanisms
Solution Approach 2:
A feedback mechanism is implemented where the voltage at the output end of LED lightbar is continuously monitored and fed back to the control circuit. When voltage indicates LED short-circuit, the feedback signal triggers the shunt switch activation, creating a closed-loop control system that automatically responds to LED failures
3Temperature
If voltage dividing resistors are added for heat dissipation, then heat dissipation capacity is improved, but device complexity and cost increase
Solution Approach 1:
Voltage dividing resistors are strategically placed only in critical high-voltage sections where heat generation is most significant, rather than throughout the entire circuit. This partial application provides sufficient heat dissipation capability where needed while minimizing the total number of resistors and associated complexity
Solution Approach 2:
The voltage division and heat dissipation function is segmented into discrete resistor elements distributed at specific locations in the circuit where voltage stress is highest. This segmentation allows targeted heat management without requiring a uniform distribution of heat dissipation components throughout the entire circuit
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 temperature of the control IC during LED short-circuits, maintaining display brightness and preventing overheating of the shunt controllable switch, thereby enhancing the reliability and performance of the LCD device.
Implementation Method 1
an output end of the LED lightbar is connected with a control IC in series, and is also connected with a shunt controllable switch; the shunt controllable switch is switched on when a voltage of the output end of the LED lightbar exceeds a preset value
Implementation Method 2
a control end of the shunt controllable switch is connected with an operational amplifier (OP) module; the shunt controllable switch is controlled by comparing a voltage difference between the feedback resistor end and the output end of the LED lightbar
Implementation Method 3
an anode of the diode is coupled to the first input end of the OP module, and a cathode of the diode is coupled to the output end of the LED lightbar. When the voltage of the output end of the LED lightbar exceeds the preset value, the diode is reversely switched on
Implementation Method 4
a voltage dividing resistor is connected in series between the output end of the LED lightbar and the shunt controllable switch. The voltage dividing resistor can share a part of voltage of a branch circuit of the shunt controllable switch and can perform the function of dissipating heat
Data Source
AI summary
The present disclosure discloses a light emitting diode (LED) backlight driving circuit, a backlight module, and a liquid crystal display (LCD) device. The LED backlight driving circuit includes an LED lightbars. An output end of the LED lightbar is connected with a control integrated circuit (IC) in series, and is also connected with a shunt controllable switch. The shunt controllable switch is switched on when a voltage of the output end of the LED lightbar exceeds a preset value and is switched off when the voltage is less than the preset value. In the present disclosure, because a shunt controllable switch is connected in parallel in the control IC, when the LED lightbars are short-circuited, the shunt controllable switch is switched on, a part of current flows towards the shunt controllable switch, and the burden of the control IC is alleviated. Thus, the temperature of the control IC is reduced.