As a core equipment in photovoltaic research, material testing, and other fields, the stability of LED solar simulators directly affects the reliability of experimental data. Below are five major modules: light source system, power drive, heat dissipation system, control system, and optical components. The system summarizes common fault phenomena, causes, and solutions, and provides preventive maintenance recommendations.

1、 Light source system malfunction

1. Abnormal brightness or poor uniformity

Phenomenon: uneven brightness in some areas, overall brightness below the nominal value, or unstable flickering

Possible reasons:

-LED beads are aging or damaged (manifested as a single bead not lighting up or brightness decay)

-Inconsistent driving current (partial deviation of lamp bead current leads to brightness difference)

-Poor heat dissipation leads to a decrease in light efficiency (high temperature causes a decrease in LED efficiency)

Solution:

-Single lamp detection: Use a dedicated detection card or a point by point illuminance meter to scan, locate and replace failed lamp beads (matching wavelength and color temperature)

-Current calibration: By debugging the software through the driving circuit, the output of each channel's constant current source is balanced, and the error is controlled within ± 3%

-Heat dissipation optimization: Clean the dust on the surface of the heat sink, check if the thermal grease is ineffective, and install an auxiliary heat dissipation fan if necessary

2. Spectral characteristics deviate from the standard

Phenomenon: Excessive deviation between spectral distribution and AM1.5G standard curve

Possible reasons:

-Filter aging (such as decreased transmittance of UV cut filters)

-Misalignment of multi-color LED ratio (imbalance of light intensity ratio of LEDs with different wavelengths)

-Driving temperature changes lead to peak wavelength drift

Solution:

-Spectral calibration: Use a spectrophotometer to measure the actual spectrum and adjust the ratio of LED driving current at different wavelengths

-Filter maintenance: Regularly replace UV filters (recommended every 2000 hours) to avoid scratches or mold

-Temperature compensation: Enable LED constant temperature drive mode to maintain junction temperature stability (usually ≤ 2 ℃ fluctuation)

2、 Power drive system malfunction

1. The device cannot be started or frequently protected

Phenomenon: No response after power on, flashing indicator light alarm or automatic shutdown

Possible reasons:

-Abnormal input power supply (low/high voltage or excessive ripple)

-Drive circuit overload protection (such as short circuit or overheating triggering)

-Control board program crashes or communication interruption

Solution:

-Power detection: Use an oscilloscope to measure the input voltage ripple (should be<5%) and check if the output of the voltage regulator module is normal

-Load troubleshooting: Disconnect the LED array connection, test the no-load output current, locate the short circuit point or replace the MOS tube

-Program restart: Reload the control program through the reset button or software port, update the firmware to the latest version

2. Current fluctuation or regulation failure

Phenomenon: There is a large deviation between the set current and the actual value, or there is a step fluctuation during the adjustment process

Possible reasons:

-Aging of constant current source feedback loop components (such as drift in sampling resistor resistance)

-PWM dimming signal interference (high-frequency switch noise coupled to analog signal)

-Insufficient resolution of DAC digital to analog conversion (common low-cost solutions)

Solution:

-Hardware calibration: Replace high-precision low-temperature drift sampling resistors (such as 0.1% precision metal film resistors)

-Signal isolation: Install a magnetic isolation transformer on the PWM line to filter out high-frequency noise

-Algorithm optimization: Upgrade the control algorithm to adaptive dynamic regulation (such as PID closed-loop control)

3、 Cooling system malfunction

1. Overheating causes accelerated light decay

Phenomenon: The brightness significantly decreases after continuous operation, and recovers after cooling down after shutdown

Possible reasons:

-Axial flow fan inlet blockage (dust accumulation)

-Poor contact between the heat dissipation fins and the heat source (excessive installation gap)

-The ambient temperature is too high (>40 ℃) and exceeds the design threshold

Solution:

-Cleaning and maintenance: Clean the air inlet filter every month and use compressed air to remove internal dust accumulation

-Thermal optimization: Apply thermal grease (thickness about 50 μ m) again and tighten the screws to the specified torque

-Forced cooling: Install a water-cooled circulation system or move the equipment to an air-conditioned room

2. Failure of temperature control sensor

Phenomenon: Abnormal temperature display, malfunction or no response of the cooling system

Possible reasons:

-NTC thermistor aging (B value deviates from standard value)

-Poor contact of temperature measurement cable (such as plug-in oxidation or virtual soldering)

Solution:

-Sensor calibration: Conduct comparative testing using a standard constant temperature bath and replace sensors with an error>± 2 ℃

-Circuit repair: Re weld cable joints and reinforce waterproofing with heat shrink tubing

4、 Control system malfunction

1. Abnormal human-computer interaction

Phenomenon: Touch screen malfunction, inability to save parameters after setting, or communication timeout

Possible reasons:

-Oil stains on the surface of the capacitive screen cause touch failure

-EEPROM storage chip is damaged (parameters cannot be memorized)

-RS485/CAN bus interference (attenuation of long-distance transmission signals)

Solution:

-Touch screen cleaning: Use non-woven fabric dipped in alcohol to wipe in one direction, avoiding the use of sharp objects to scratch

-Data storage: After backing up the parameters, replace the storage chip and test whether the write function is normal

-Communication anti-interference: using shielded twisted pair cables and parallel connection of 120 Ω resistors at the terminals, reducing communication distance by less than 15 meters

2. Failure of automated testing

Phenomenon: The light intensity/time curve in programmable mode does not conform to the preset program

Possible reasons:

-PLC program logic error (such as conditional judgment vulnerability)

-Distortion of light intensity feedback signal (such as aging of photodiodes)

Solution:

-Program debugging: Use ladder diagram monitoring tools to gradually troubleshoot logical nodes and fix condition triggered defects

-Sensor calibration: Replace the silicon photodiode with linearity>98% and calibrate the output with a standard light source

5、 Optical component malfunction

1. Filter failure

Phenomenon: Spectral distribution distortion, sudden drop in light intensity in specific bands

Possible reasons:

-UV filter fluorescent material attenuation (such as MgF ₂ coating peeling off)

-IR filter thermal damage (localized discoloration at high power)

Solution:

-Visual inspection: Observe the surface of the filter for spots, cracks, or fading, and replace spare parts in a timely manner

-Life management: Record the cumulative usage time of the filter, and it is recommended to replace it every 1500 hours under AM1.5G conditions

2. Abnormal uniform light system

Phenomenon: Concentric circular stripes or obvious edge gradients appear in the illuminated area

Possible reasons:

-Fresnel lens dirty or installed offset

-Peeling of reflective coating inside the integrating sphere

Solution:

-Optical cleaning: Use lens paper dipped in anhydrous ethanol to wipe the lens, adjust the installation angle to align with the projection center

-Coating repair: Partial repair of PTFE coating on the inner wall of the integrating sphere, and replacement of the sphere in severe cases