Backlight Driving Circuit Alternating LED Strings
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Solution Overview
Problem
Conventional backlight driving circuits face high power loss and risk of component damage when driving multiple LEDs in series, as they require increased duty cycle and voltage, leading to elevated current and temperature.
Innovation Solution
The proposed solution involves a backlight driving circuit with a voltage conversion unit, switch units, and a level conversion unit, allowing for the division of an LED module into two strings, where the circuit loops are controlled to alternate in operation, reducing the duty cycle and driving voltage, and utilizing NMOSFETs and a comparator for efficient power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the duty cycle is increased to drive more LEDs in series, then the output voltage is sufficient to drive the LED module, but the power loss increases and temperature rises causing component damage
Solution Approach 1:
The patent divides the LED module into two separate LED strings (first LED string and second LED string) that are driven alternately. This segmentation allows each string to be driven at a lower voltage and duty cycle, reducing power loss and temperature rise while maintaining overall illumination output.
Solution Approach 2:
The patent implements periodic alternating operation where the first LED string and second LED string are switched on and off in alternation based on PWM signals. This periodic action allows the system to drive LEDs at lower duty cycles by distributing the operation over time, thereby reducing instantaneous power loss and thermal stress.
2Power
If the duty cycle is increased to drive more LEDs in series, then the output voltage is sufficient to drive the LED module, but the temperature of elements increases causing component damage
Solution Approach 1:
The patent divides the LED module into two separate LED strings (first LED string and second LED string) that are driven alternately. This segmentation allows each string to be driven at a lower voltage and duty cycle, reducing power loss and temperature rise while maintaining overall illumination output.
Solution Approach 2:
The patent implements periodic alternating operation where the first LED string and second LED string are switched on and off in alternation based on PWM signals. This periodic action allows the system to drive LEDs at lower duty cycles by distributing the operation over time, thereby reducing instantaneous power loss and thermal stress.
3Power
If the duty cycle is increased to drive more LEDs in series, then the output voltage is sufficient to drive the LED module, but the current flowing through the circuit increases causing component damage
Solution Approach 1:
The patent divides the LED module into two separate LED strings (first LED string and second LED string) that are driven alternately. This segmentation allows each string to be driven at a lower voltage and duty cycle, reducing power loss and temperature rise while maintaining overall illumination output.
Solution Approach 2:
The patent implements periodic alternating operation where the first LED string and second LED string are switched on and off in alternation based on PWM signals. This periodic action allows the system to drive LEDs at lower duty cycles by distributing the operation over time, thereby reducing instantaneous power loss and thermal stress.
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 effectively decreases the driving voltage and duty cycle, reducing power loss and heat generation, while ensuring the LEDs are driven efficiently without increasing the duty cycle, thus protecting the circuit components.
Implementation Method 1
a voltage conversion unit comprising a primary winding and a secondary winding
Implementation Method 2
when the MOSFET Q is turned on, the power voltage Vin is applied to two ends of the inductor L, the current flowing through the inductor L is enhanced, and the inductor L store energy
Implementation Method 3
a metal-oxide-semiconductor field-effect transistor (MOSFET) Q. The LED driving chip 10′ is used to output a pulse-width modulation (PWM) signal to control the MOSFET Q to turn on or off periodically
Data Source
AI summary
A backlight driving circuit includes a LED driving chip (10) for outputting a PWM signal, a power port (20), a voltage conversion unit (30), a first, a second, and a third switch unit (50, 60, 70), and a level conversion unit (40). The voltage conversion unit (30) includes a primary unit (31) and a secondary winding (32). The first switch unit (50) is connected to the power port (20) and the primary unit (31). The second switch unit (60), the secondary winding (32) and a first LED string (21) forms a first circuit loop (LP1). The first and the second switch unit (50, 60) are turned on or off when receiving the PWM signal. The third switch unit (70), the primary winding (31), and a second LED string (22) form a second circuit loop (LP2). The voltage conversion unit output a reversed PWM signal to the third switch unit (70).