Why does the lumen increase when the wattage of LED lamps decreases

1. Decoding the Efficiency Droop Phenomenon

Core Mechanism: Non-Linear Photoelectronic Conversion
LED chips exhibit peak luminous efficacy (lm/W) at moderate current densities (150–350 A/cm²), beyond which efficacy declines sharply due to:

• Carrier Overflow: At high current densities (>500 A/cm²), electrons/holes overflow the quantum well region before recombination, converting >30% of energy into waste heat (Applied Physics Letters, 92: 245503).

• Auger Recombination: Dominant above 400 A/cm², this three-carrier interaction dissipates energy as lattice vibration (heat) rather than photons – accounting for 40–60% efficiency loss (IEEE Journal of Quantum Electronics, 2017).

• Joule Heating Paradox: Current reduction from 100%→70% rated power decreases resistive losses by 51%, per Ohm’s law (P=I²R).

Engineering Insight: Operating at 60–80% rated current elevates system efficacy by 15–25% by circumventing the droop "cliff region."

2. Junction Temperature (Tj) Optimization Effects

Thermal Dynamics Governing Photon Output
Reducing power induces a cascade of efficiency-boosting events:

Scientific Validation:

• Vf reduction decreases power consumption (P=IV) despite constant current

• Phosphor thermal quenching reduced from 3.5%/°C to <1%/°C below 85°C (ECS Journal of Solid State Science, 2020)

3. Driver Efficiency Synergy

Optimal Operating Point Alignment
High-efficiency switching drivers (e.g., Buck-Boost topology) exhibit >95% conversion efficiency across 30–90% load range:

• Critical Design Insight: Quality drivers minimize losses at partial loads:

• MOSFET conduction losses ↓ at lower currents

• Core hysteresis losses ↓ with reduced flux swing

• Data-Driven Example: Infineon ICL5101 driver maintains 96.3% efficiency at 50% load vs. 95.1% at 100% load.

Engineering Application Guidelines

1. Current Tuning Protocol

• Configure drivers at 70–80% rated output via 0–10V dimming/PWM

• Use thermal interface materials (TIMs) with thermal resistance <1.0 K/W

2. Phosphor Selection Matrix

   Phosphor Type	Max Temp Stability	Efficacy Gain @ Low Tj
   LuAG:Ce³⁺	180°C	+12%
   β-SiAlON:Eu²⁺	150°C	+9%
   KSF:Mn⁴⁺	120°C	+5%

3. Finite Element Thermal Simulation
   Validate heatsink designs to maintain Tj<85°C at target operating point using Ansys Icepak.