Segmented Boost Circuit for LCD Backlight Voltage Conversion
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Solution Overview
Problem
The existing driving circuits for LCD backlight sources face issues with high temperature, high Bill Of Material (BOM) costs, and low current-driving ability due to the use of high-voltage tolerance components, which are inefficient and costly, especially when converting 24V to 150V and managing heat dissipation.
Innovation Solution
A modified BOOST structure driving circuit is introduced, incorporating a voltage multiplexer circuit with capacitors and diodes for a second voltage boost, and an inductor as a freewheeling element to enhance current-driving ability, allowing the use of lower voltage tolerance components and reducing circuit temperature and BOM costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a BOOST structure with high voltage tolerance MOSFET is used to convert 24V to 150V, then the voltage conversion is achieved, but the circuit temperature increases and BOM cost increases
Solution Approach 1:
The patent divides the single high-voltage BOOST circuit into two separate low-voltage BOOST stages. Each stage operates at approximately 75V instead of requiring one stage at 150V, allowing the use of lower voltage tolerance MOSFETs (75V or 100V rated) that generate less heat and cost less, while achieving the same 24V to 150V conversion through cascaded stages
2Power
If high voltage tolerance MOSFET is used for 24V to 150V conversion, then the voltage conversion is achieved, but the BOM cost increases
Solution Approach 1:
The patent segments the voltage conversion into two stages, each handling a smaller voltage multiplication ratio. This allows the use of cheaper, lower voltage-rated MOSFETs in each stage rather than expensive high-voltage MOSFETs, significantly reducing the BOM cost while maintaining the required 24V to 150V conversion capability
3Power
If high voltage tolerance devices are used, then the voltage conversion to 150V is achieved, but the current-driving ability decreases
Solution Approach 1:
By splitting the conversion into two stages with intermediate voltage output (approximately 75V each stage), the patent enables better current control in each stage. The lower voltage stress on MOSFETs in each stage improves their current-handling capability compared to a single high-voltage stage, and the cascaded architecture allows cumulative current output to the LED strings
Solution Approach 2:
The patent introduces an intermediate voltage stage between the input 24V and the final 150V output. This intermediate stage acts as a mediator that improves current-driving ability by operating at lower voltage stress, and the two BOOST circuits work together to deliver enhanced current capability to the LED backlight
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 improves the current-driving ability of the circuit, lowers the temperature of the circuit board, and reduces the overall BOM costs by effectively managing voltage and current, while maintaining efficient operation for large LCDs.
Implementation Method 1
a BOOST structure which comprises a capacitor C12, a capacitor C13, an inductor L2, a diode D2, and a MOSFET
Implementation Method 2
a capacitor C11, a capacitor C14, a diode D3, and a diode D4, wherein one terminal of the diode D3 is connected to one terminal of the capacitor C13
Implementation Method 3
a diode D2, and a MOSFET, wherein the other terminal of the inductor L2 is connected to one terminal of the diode D2
Data Source
AI summary
A driving circuit for a LCD backlight source comprising a BOOST structure which comprises a capacitor C12, a capacitor C13, an inductor L2, a diode D2, and a MOSFET, wherein the driving circuit further comprises a capacitor C11, a capacitor C14, a diode D3, and a diode D4. One terminal of the diode D3 is connected to one terminal of the capacitor C13, and the other terminal is connected to one terminal of the diode D4; the other terminal of the diode D4 is connected to one terminal of the capacitor C14 which is the output terminal of the circuit, and the other terminal of the capacitor C14 is grounded; one terminal of the capacitor C11 is connected between the inductor L2 and the diode D2, and the other terminal of the capacitor C11 is connected between the diode D3 and the diode D4.