This is a study of the XCANLEDDC device under various environmental conditions.
2. Test Parts
The testing proceeded in 3 parts. The first part was a 1000 hour test which cycled temperature between -55°C and 105°C while turning the power to the light fixture off and on again. The second part was a 24-hour high temperature soak, where the device was kept at the temperature of 107°C, and while the power to the device was turned off for 2 hours and then turned back on for two hours, and repeated until test conclusion. The final test was identical to the second test, excepting that the temperature was set to -55°C.
3. Test Results
3.1. Nemalux Part 1A Testing
This report is to detail Nemalux’s temperature part A testing on the XCANLEDDC device. The device was tested for 1000 hours.
Design temperature sweep: -55°C to +105°C, 1000 hours.
3.1.2 Notes About the execution of the Part 1A Test
1. After approx 2 days, the temperature sweep was widened to: -57°C to +107°C in order to ensure that the fixture reaches its target temperatures.
2. After resetting the temperature sweep (after day 2), a single setting was improperly programmed on the current meter. This is why it looks as though there was no current flowing through the device for the period between hours 46 and 70. Once this was noted, the setting was corrected. It should be emphasized that this was only a setting error, and that there was current flowing to the device, as evidenced by visually noting the presence of light coming from the thermal chamber.
3. The system was checked each business day to ensure that proper program execution was occurring. Once the system had finished its 1000 hour program, the fixture was allowed to return to room temperature, and was then inspected, and images of the fixture collected.
3.1.3 Main Outcomes from Part 1A Testing
1. The fixture physically survives the testing, and is capable of operation after the test.l
2. There is evidence of time-dependent performance change throughout the testing, which may be attributable to the temperature cycling, but which may also be natural device ageing.
3. Current draw at +107°C is changing over time, and ranges from approx. 2.43 A (@11.67 V) at the start of test, to approx. 2.45 A (@11.67 V) at the end of the test. This shift is highlighted by red bars overlaid on the data plot shown in figure 1.
4. Current draw at -57°C is changing over time, and ranges from approx. 2.3 A (@11.67 V) at the start of test, to approx. 2.0 A (@11.67 V) at the end of the test. This shift is highlighted by blue bars overlaid on the data plot shown in figure 1.
5. Maximum current draw is 2.95 A at an unknown temperature (@11.67 V).
3.1.4 Detailed Results Information
Figure 1. shows the temperature and current data plotted against time. The trend bars that have been added show time-dependent features of the plot (see points 3 & 4 in “Main Outcome from Testing”). In contrast to the preliminary report, the stable current draw at the low temperature extreme (-57°C) is lower than the stable current draw at the high temperature extreme (107°C); at an unknown temperature between these two extremes, the light fixtures draws a maximum current of approx. 2.95 amps. Figure 2 shows a close-up image of the current and temperature over a reduced time period to highlight important characteristics in the current-temperature relationship. This is a brief description of a single temperature/current period on Figure 2. The numbers correspond to the red numbers on Figure 2.
Power is reactivated after being off at high temperature. An immediately measured current is seen which is changing over time. The current quickly stabilizes at a value of approx. 2.44 A, but as the system starts to heat up due to excess power dissipation, the current lowers by approx 0.01A.
The temperature falls from 107°C down to -57°C. The UUT will thermally lag the chamber ambient temperature, but as temperature falls the current rises. It would seem that there is a peak current which occurs at a temperature somewhere within the operating region (i.e. not at one of the two extreme temps).
The ambient temperature reaches the low value and stabilizes. After 30 minutes, the power shuts off, and the current falls to zero. When the power is reactivated at low temperature, there is an immediately measured current which is changing over time. The measured current quickly tends towards 2.22 A, the approx. stable current at -57°C. The short section of increasing current which is concave down is likely being caused by the temperature increase due to the power dissipation after the unit has been re-energized.
The ambient in the chamber then begins to rise back towards 107°C. The UUT also begins to increase in temperature, and the current subsequently increases until it passes the temperature at which current is maximized (max current is approx 2.94 A, unknown maximizing temperature) and then begins to decrease again. The current drops to a value of approx 2.45 A, which is close to its stable operating current at 107°C.
The power to the unit is then shut off, and the device stabilizes in temperature.
Cycle complete, and repeats.