Charge Recycling Circuit for LED Backlighting
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Solution Overview
Problem
Existing charge recycling schemes in LED backlighting applications require a large number of switches, leading to unreasonably large die size and high costs, and do not effectively provide stored charge to a power supply, resulting in inefficiencies such as 'ghost lighting' and wastage of charge.
Innovation Solution
A charge recycling circuit that selectively couples parasitic components with an energy storage element, allowing the stored charge to be provided to a power supply, reducing the number of required switches and enhancing power efficiency by reusing residual electrical charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge is discharged from parasitic capacitors to ground via switches, then ghost lighting is prevented, but charge is wasted and power efficiency deteriorates
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitor discharge (which causes ghost lighting) into a beneficial effect by directing the discharge current through LED strings to provide useful illumination. The parasitic capacitors are intentionally charged during normal operation and then discharged through the LED strings during dimming or off periods, eliminating waste and providing additional lighting benefit.
Solution Approach 2:
Instead of discarding the charge stored in parasitic capacitors to ground, the patent recovers this charge by routing it through the LED strings. The discharge path is controlled to flow through the LEDs, thereby recovering the energy that would otherwise be lost and using it productively.
2Loss of energy
If bit line to bit line charge recycling is implemented, then charge wastage is reduced, but the number of switches increases leading to larger die size
Solution Approach 1:
The patent makes the parasitic capacitors serve multiple functions: they act as decoupling capacitors during normal operation and as charge sources during dimming/off periods. This multi-functionality eliminates the need for separate charge recycling switches, as the existing parasitic capacitors and LED string connections are reused for charge discharge.
Solution Approach 2:
The system uses its own parasitic capacitors and existing LED string pathways to perform charge recycling, rather than requiring external recycling circuits. The parasitic capacitors automatically discharge through the LED strings when controlled by the dimming signal, making the system self-sufficient for charge recovery.
3Reliability
If switches are added to discharge parasitic capacitors to ground, then ghost lighting is eliminated, but device complexity and cost increase
Solution Approach 1:
The system uses existing components (parasitic capacitors and LED strings) to eliminate ghost lighting without adding external discharge switches. The controlled discharge through LED strings achieves ghost lighting prevention while utilizing already-present circuit elements.
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 reduces the number of switches needed, decreases die size and material costs, and improves power efficiency by directing parasitic capacitor discharge into an energy storage element rather than ground, enabling efficient reuse of charge for powering circuit elements.
Implementation Method 1
an energy storage element configured to receive a charge from a parasitic component, store the charge and to provide the charge to a power supply
Data Source
AI summary
A method and an apparatus for charge recycling. The method is comprised of the steps of receiving a charge at an energy storage element from a parasitic component, storing the charge at the energy storage element, and providing the charge stored at the energy storage element to a power supply's input or output. The step of receiving the charge at the energy storage element includes operating a discharging switch to selectively couple the parasitic component with the energy storage element and receiving the charge at the energy storage element via the discharging switch when the energy storage element and the parasitic component are coupled.