Dual Boost LED Backlight Drive Circuit for High Power Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional single boost circuits in LED backlight drive circuits are limited in power output, leading to increased power consumption, heat issues, and risk of component burnout, and fail to meet the growing power demands of larger liquid crystal display panels.
Innovation Solution
A backlight drive circuit with dual boost circuits, utilizing two MOS transistors and inductors operating alternately with phase-opposed drive signals to increase output power while reducing ripple and electromagnetic interference, thereby enhancing reliability and product pass rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single boost circuit is used to increase output voltage, then the output voltage can be raised, but the electrical current increases linearly causing excessive power consumption and heat generation
Solution Approach 1:
The single boost circuit is divided into two separate boost circuits operating in alternating cycles. Each circuit handles half of the total power delivery, with their currents being out of phase. This segmentation reduces the peak current through each inductor and transistor, thereby reducing power consumption and heat generation in individual components while maintaining the required output voltage.
2Illumination intensity
If the duty ratio is increased to raise output voltage, then the output voltage increases, but the conduction time extends causing current to quickly raise and components to overheat
Solution Approach 1:
The two boost circuits operate in alternating periodic cycles with 50% duty cycle each. While one circuit is in its on-state charging its inductor, the other is in its off-state discharging to the output. This periodic alternation ensures that each component experiences reduced peak current stress and has time to dissipate heat, preventing overheating while maintaining continuous power delivery to the LED string.
3Device complexity
If a single boost circuit is used, then the circuit structure is simple, but the output power is limited to around 70W and cannot meet the needs of larger displays
Solution Approach 1:
The power delivery function is segmented into two parallel boost circuits, each capable of delivering approximately 70W. By operating these circuits alternately with phase-opposed drive signals, the system achieves doubled output power (around 140W) while keeping each individual circuit relatively simple. This segmentation allows the system to scale power output without requiring a single complex high-power circuit.
4Power
If two boost circuits operate simultaneously, then the output power increases, but the ripple of output current increases and electromagnetic interference worsens
Solution Approach 1:
The two boost circuits are driven with phase-opposed periodic signals, causing them to operate in alternating cycles rather than simultaneously. When one circuit's MOS transistor is on, the other is off, and vice versa. This alternating operation reduces output current ripple because the inductors charge and discharge in complementary fashion, and significantly reduces electromagnetic interference by ensuring that only one switching event occurs at any given time, halving the EMI burden compared to simultaneous operation.
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 dual boost circuit design effectively doubles the output power without exceeding component limits, reduces ripple in output current, and minimizes electromagnetic interference, improving the reliability and efficiency of the LED backlight drive circuit.
Implementation Method 1
an electrical inductor L10, a MOS transistor Q10, a rectifier diode D10, and an output electrolyte capacitor C10 to form a single boost circuit that provides a higher level of voltage
Implementation Method 2
the magnitude of the output voltage is related to the duty ratio (D) of a gate drive signal of the MOS transistor Q10
Implementation Method 3
a rectifier diode D10
Data Source
AI summary
The present invention provides an LED backlight drive circuit, which includes a first power supply module, an electrical inductor, a rectifier diode, a MOS transistor, an electrolytic capacitor, an LED light string, a voltage division module, a voltage comparator, a second power supply module, and an LED constant-current drive chip. The LED backlight drive circuit is arranged to include a voltage comparator in an external circuit of the LED constant-current drive chip to detect output voltage of the drive circuit so that high voltage, the voltage comparator is caused to supply a low voltage level to forcibly pull down a PWM dimming signal or an ENA enabling signal of the LED constant-current drive chip to achieve an over-voltage protection function and also enable removal of over-voltage protection module from a conventional LED constant-current drive chip.